European Heart Rhythm Association (EHRA)/Heart Rhythm Society (HRS)/Asia Pacific Heart Rhythm Society (APHRS)/Latin American Heart Rhythm Society (LAHRS) expert consensus on risk assessment in cardiac arrhythmias: use the right tool for the right outcome, in the right population

Jens Cosedis Nielsen (EHRA Chair)1 | Yenn-Jiang Lin (APHRS Co-Chair)2 | Marcio Jansen de Oliveira Figueiredo (LAHRS Co-Chair)3 | Alireza Sepehri Shamloo4 | Alberto Alfie5 | Serge Boveda6 | Nikolaos Dagres4 | Dario Di Toro7 | Lee L. Eckhardt8 | Kenneth Ellenbogen9 | Carina Hardy10 | Takanori Ikeda11 | Aparna Jaswal12 | Elizabeth Kaufman13 | Andrew Krahn14 | Kengo Kusano15 | Valentina Kutyifa16,17 | Han S. Lim18,19 | Gregory Y. H. Lip20,21 | Santiago Nava-Townsend22 | Hui-Nam Pak23 | Gerardo Rodríguez Diez24 | William Sauer25 | Anil Saxena26 | Jesper Hastrup Svendsen27,28 | Diego Vanegas29 | Marmar Vaseghi30 | Arthur Wilde31 | T. Jared Bunch (HRS Co-Chair)32

With this document, we intend to describe and review status of performing risk assessment in different patient populations with cardiac diseases or conditions with high risk of developing such.
Our objectives are to raise awareness of using the right risk assessment tool for a given outcome in a given population, and to provide physicians with practical proposals that may lead to improvement of patient care in this regard. For quick reference, sub-chapters start with a short section on consensus statements. The document concludes with a summary of consensus statements.

| Evidence review
Members of the Task Force were asked to perform a detailed literature review using PubMed and EMBASE, weigh the strength of evidence for or against a particular treatment or procedure, and include estimates of expected health outcomes for which data exist. Patientspecific modifiers, comorbidities, and issues of patient preference that might influence the choice of particular tests are considered, as are frequency of follow-up and cost-effectiveness. In controversial areas, or with regard to issues without evidence other than usual clinical practice, consensus was achieved by agreement of the expert panel after thorough deliberations. This document was prepared by the Task Force and peer-reviewed by official external reviewers representing EHRA, HRS, APHRS, and LAHRS.
Consensus statements are evidence-based and derived primarily from published data or determined through consensus opinion if no data available. Current systems of ranking level of evidence are becoming complicated in a way that might compromise their practical utility. 1 In contrast to guidelines, we opted for an easier user-friendly system of ranking using 'coloured hearts' that should allow physicians to easily assess the current status of the evidence and consequent guidance (Table 1) Finally, this consensus document includes evidence and expert opinions from several countries. The risk assessment approaches discussed may therefore include tests not approved by governmental regulatory agencies in all countries.

| Relationships with industry and other conflicts
All members of the writing group, as well as reviewers, have disclosed any potential conflicts of interest. Details are available in Supporting Information online.
All consensus statements were voted upon by the writing committee independently and reached the predefined level of ≥75% consensus for inclusion in consensus statement tables. Each partner society officially reviewed the document, and all reviewer comments were addressed. Each partner society approved the final document and consensus statements.

| Value of clinical history and characteristics including clinical risk scores such as CHA 2 DS 2 -VASc
Clinical assessment of the patient with cardiac arrhythmias starts with a good clinical history and basic investigations for an underlying aetiological factor for the arrhythmia or its associated complication(s). In addition, an assessment of the risks and benefits of any therapeutic intervention should be made, and appropriate management initiated.
Following on from clinical history and assessment, there is a proposal toward a more integrated and holistic approach to arrhythmia management, as evident in guidelines. Such an integrated approach requires multidisciplinary teams of healthcare professionals, patient involvement, access to treatment options, and decision-support tools to optimize the patient journey. Many proposals have been made towards the operationalization of such an integrated approach to risk assessment and practical management in cardiac arrhythmias, which has been of varying complexity. As an example, the management of atrial fibrillation (AF) has been simplified into the ABC pathway ('A' Avoid stroke with Anticoagulation; 'B' Better symptom management, with patient-centred and symptom-directed decisions on rate or rhythm control; 'C' Cardiovascular and comorbidity risk management), which has been shown to be associated with improved clinical outcomes and reduced healthcare costs. [2][3][4][5][6] This makes a strong argument for using the right approaches and clinical tools for patient assessment, but using them appropriately for the reasons they were first proposed (e.g. stroke risk scores to assess stroke risk, and not other outcomes).
Taking AF as an illustrative example with regard to using the right score for the right reason there are many risk factors for stroke (but the more common and validated ones have been used to formulate risk stratification tools). 7 The most common in use is the

TA B L E 1 Scientific rationale of consensus statements
Definitions related to a treatment or procedure

Consensus statement instruction Symbol
Scientific evidence that a treatment or procedure is beneficial and effective. Requires at least one randomized trial, or is supported by strong observational evidence and authors' consensus (as indicated by an asterisk).
'Should do this' General agreement and/or scientific evidence favour the usefulness/efficacy of a treatment or procedure. May be supported by randomized trials based on a small number of patients or not widely applicable.
'May do this' Scientific evidence or general agreement not to use or recommend a treatment or procedure.
'Do not do this' The categorization for our consensus document should not be considered directly similar to the one used for official society guideline recommendations which apply a classification (I-III) and level of evidence (A, B, and C) to recommendations.
The 12-lead ECG provides diagnostic and prognostic information in patients with inherited high-risk syndromes including long QT syndrome (LQTS), short QT syndrome, Brugada Syndrome, and arrhythmogenic cardiomyopathy and should be obtained. 17 Exercise ECG provides diagnostic and prognostic information for patients with LQTS arrhythmogenic cardiomyopathy, hypertrophic cardiomyopathy (HCM), catecholaminergic polymorphic ventricular tachycardia, and documented or suspected arrhythmias related to exertion, and should be obtained. 17 Ambulatory ECG evidence of nonsustained ventricular tachycardia provides prognostic information in ischaemic cardiomyopathy, arrhythmogenic cardiomyopathy, and HCM and should be obtained. 17 The signal-averaged ECG and QRS fragmentation may aid in the diagnosis of arrhythmogenic cardiomyopathy. 18 The signal-averaged ECG and QRS fragmentation may be useful in risk stratification of Brugada syndrome. 18 Heart rate variability, heart rate turbulence, signal-averaged ECG, and T wave alternans analysis, when used in combination with additional clinical, electrocardiographic, and structural measures, may be useful for identifying high-and low-risk groups among patients with acquired structural heart disease. 19

| Electrocardiographic methods
The ECG is the gold standard for risk assessment in patients with or at risk of developing cardiac arrhythmias. The 12-lead ECG is inexpensive and widely available. Risk stratification with the ECG is limited in general by its low positive predictive value (PPV) determined to a large extent by the low prevalence of cardiovascular events in the general population. However, the prognostic significance of the ECG is enhanced in patients with heart disease.

| P wave and PR interval
The prognostic value of P wave characteristics has been examined in subjects enrolled in clinical trials of AF for prediction of the development of AF, where maximum P wave duration was a significant independent risk marker for the development of AF over 10 years. 20 This observation was confirmed by epidemiologic/population studies (including ARIC and the Copenhagen ECG studies) that showed increased risk of AF in patients with prolonged P wave duration and PR interval prolongation, [21][22][23] and summarized in a review by Nikolaidou et al. 24 Moreover, a prolonged P wave duration was determined as a sensitive predictor of post-operative AF in patients undergoing coronary artery bypass grafting (CABG). 25 The definition of an abnormal P wave varies greatly depending on how it is measured, and definitions vary depending on whether P wave area, duration, terminal forces in lead V1 or signal-averaged P wave are analysed. Abnormal P wave morphology was associated with incident stroke in the Multi-Ethnic Study of Atherosclerosis. 26 The prognostic significance of PR interval prolongation, which is variably defined as PR intervals greater than 196-220 milliseconds, is controversial and depends on the patient population studied. Most studies show that PR interval prolongation is not associated with increased mortality in healthy middle-aged individuals during medium term follow-up. On the other hand, a number of reports show worse survival in patients with suspected heart failure (acute and chronic) or heart disease (coronary artery disease [CAD]). Additionally, PR prolongation and P wave prolongation predict increased risk of AF and the greater degrees of PR prolongation and P wave duration predicted higher risks of AF. 27,28 An increased PR interval is also associated with poor cardiovascular outcomes in patients with AF. 29 Several studies have shown that PR prolongation in patients undergoing cardiac pacing or receiving cardiac resynchronization therapy (CRT) is an independent predictor of worse prognosis and lower probability of reverse remodelling as well as an increased risk of AF, death, and hospitalization. 30,31 There are no data indicating whether the degree of PR prolongation portends a worse outcome compared to patients who have lesser degrees of PR prolongation, nor is there information on its prognostic value in acute inferior wall myocardial infarction (MI).  32 The presence of an unprovoked type 1 Brugada Syndrome pattern is associated with increased risk as is discussed later in the document.

QT interval
Measurement of the QT interval can be complicated by QRS prolongation and by the need to correct for heart rate, as has been described elsewhere. 33 Despite these limitations, prolongation of the heart rate-corrected QT interval (QTc) has been associated with mortality in several population studies. 34,35 In congenital long QT syndrome (LQTS), the length of the QT interval is a major predictor of risk of cardiac events, including sudden cardiac death (SCD).
When initiating QT-prolonging drugs such as sotalol or dofetilide, a QT interval of 500 milliseconds or higher should prompt reduction or discontinuation of the offending drug(s).

QT dispersion
This measure of ventricular repolarization heterogeneity is typically defined from the 12-lead ECG as the QT max − QT min . It has been used to predict a wide variety of events, including ventricular proarrhythmia, VTs, although the sensitivity, specificity, and accuracy are poorly defined and highly dependent on the patient population studied. 36 T wave T wave inversions are common and may be non-specific or may signal important abnormalities such as ischaemia or hypertrophy.
Widespread deep T wave inversions in combination with QT prolongation, such as may occur in acute stress cardiomyopathy, can be associated with torsades de pointes. Abnormal T wave notching can be a clue to abnormal repolarization and is often seen in patients with QT prolongation. Computerized T-wave analytic techniques   such as principal component analysis, T-wave residuum, flatness,   asymmetry, and notching have been developed in an effort to detect   and quantify abnormal repolarization and may have particular value   in identifying patients with LQTS. 37,38 Moreover, it has been shown   that adding T-wave morphology characterizations to age, gender, and QTc in a support vector machine model can improve LQTS diagnosis. 39 However, these additional analytic techniques are not used in routine clinical practice.
The Tpeak-end interval, measured from the peak to the end of the T-wave, thought to reflect heterogeneity of repolarization in the heart, has been associated with arrhythmic risk in various populations. 40 However, considerable controversy remains as to how it should be measured and applied. 41 T-wave alternans is a beat-to-beat alternation of T wave morphology. When seen with the naked eye, it usually accompanies marked QT prolongation and is a harbinger of immanent torsades de pointes. Analysis of more subtle T-wave alternans has been used for assessing abnormal and heterogeneous repolarization to predict mortality and arrhythmic risk. Abnormal microvolt T-wave alternans assessed using the spectral method during graded exercise has a high negative predictive value and has been used to identify a subgroup of patients with reduced ejection fraction who are not likely to benefit from defibrillator implantation. 18 Microvolt T-wave alternans analysis cannot be performed when the rhythm is AF, and patients with ventricular pacing have not been studied extensively.

Early repolarization
Early repolarization pattern, highly prevalent in the overall population, defined as an elevation of the J point of at least 0.1 mV, may occur in the anteroseptal or inferolateral leads. In 2008, Haissaguerre reported an association of inferolateral early repolarization with increased risk of idiopathic ventricular fibrillation (VF) in a case-control study 42 and subsequently confirmed in other case-control studies.
Exercise testing or isoproterenol testing improved the pattern of repolarization, and the pattern was accentuated with exposure to betaadrenergic blockers. In a meta-analysis of population-based studies, inferolateral early repolarization was associated with increased risk of arrhythmic death, but the risk was still quite low in general (70/100 000 patient-years). 43 It appears that individuals at highest risk have early repolarization in multiple (especially inferior) leads, with high voltage (at least 0.2 mV), and with notching or horizontal/ down-sloping ST segments. Early repolarization is especially prevalent in young men, particularly young black men, and in athletes. 44 Because the absolute risk of arrhythmic death is so low, asymptomatic individuals with early repolarization, even those with higher risk ECG patterns, do not require further evaluation except when there is a strong family history of sudden cardiac death or when the J point elevation is associated with Brugada syndrome (discussed later in this document) or short QT syndrome (SQT).

| Ambulatory electrocardiographic monitoring
In 1984, Bigger et al. showed that ventricular ectopy recorded on a Holter monitor, especially when combined with a low left ventricular ejection fraction (LVEF), predicted a higher risk of mortality in post-infarction patients compared to those without ectopy. 45 Non-sustained VT is also associated with increased risk in patients with arrhythmogenic and hypertrophic cardiomyopathy (HCM).
Other data that can be extracted from ambulatory monitoring include heart rate, heart rate variability, and heart rate turbulence measurements, which can predict mortality risk at least in ischaemic cardiomyopathy, but have not been incorporated into clinical practice. 19 Cardiac MRI is useful in assessing aetiology-driven risk of VT and for the presence of scar or myocardial inflammation. [49][50][51] Cardiac positron emission tomography may be useful for the assessment of aetiology-driven risk of ventricular arrhythmias and the presence of scar or myocardial inflammation in patients without CAD. 52,53 the Efficacy of ICDs in Patients with Non-ischaemic Systolic Heart Failure (DANISH) trial showed that primary prevention ICD in the setting of severe non-ischaemic cardiomyopathy did not reduce all-cause mortality in patients on optimal medical therapy for heart failure, ICD implantation was associated with a 50% reduction in ar-  66 The MADIT trial initially also utilized an EPS in post-MI patients with an EF ≤30%, and non-sustained VT events to implant an ICD, and showed survival benefit with the ICD. 54 However, MADIT-II subsequently eliminated the need for an EPS in post-MI patients with an EF ≤30% and similarly showed the life-saving benefit of the ICD in a broader patient cohort. 55 Therefore, post-MI patients with an EF ≤30% do not currently need to undergo an EPS to guide decisions on whether to implant an ICD.
In patients with heart failure and EF ≤35%, an EPS is not recommended for risk assessment for the decision on ICD indication.
Some centres perform an EPS for inducibility to better characterize induced, sustained VT events, and their response to antitachycardia pacing (ATP), which may potentially help to tailor ICD programming.
Furthermore, in patients who have syncope of uncertain origin, an EPS could identify ventricular arrhythmias or document electrical conduction disorders. 67,70,71,74 In the case of channelopathies, there is no indication for an EPS, except for Brugada syndrome. In Brugada syndrome, EPS may be useful in asymptomatic patients with spontaneous or drug-induced type 1 pattern, especially when there is a family history of sudden death. 75-77

Implantable cardiac devices Class References
An ILR is indicated in the evaluation of patients with infrequent recurrent syncope of uncertain origin especially when ambulatory monitoring is inconclusive [78][79][80] An ILR is indicated in patients with syncope and highrisk criteria in whom a comprehensive evaluation did not demonstrate a cause of syncope or lead to a specific treatment, and who do not have conventional indications for primary prevention ICD or pacemaker. [78][79][80] An ILR can be considered in patients with palpitations, dizziness, pre-syncope, frequent premature ventricular complexes (PVCs)/nonsustained VT, and in those with suspected AF, and following AF ablation. 78-80

| Implantable loop recorder to diagnose unexplained syncope/atrial fibrillation with cryptogenic stroke
The implantable loop recorder (ILR) provides long-term continuous monitoring and improves the diagnosis in patients with unexplained syncope. 81 In a meta-analysis of 49 studies that included 4381 participants, the diagnostic yield for the detection of arrhythmogenic syncope was 26.5%. 78 Moreover, the CRYSTAL-AF trial 80 revealed that the ILR can detect subclinical AF following cryptogenic stroke.
Still, any benefit of these findings needs to be confirmed in large randomized trials. Early use of the ILR has been advocated by the European guidelines 82 and in the American guidelines following inconclusive non-invasive monitoring. 83 The indications for ILR have been expanded in the current guidelines (Table 2).

| Implantable loop recorder to diagnose atrial and ventricular arrhythmia events
While the ILR can be useful to detect atrial and ventricular arrhythmias, a large cohort study indicated that most of the current use of ILRs is primarily in patients with unexplained syncope (84%), followed by palpitations (13%), and suspected AF (12%). 79 Another smaller study specifically studying the risk of SCD and arrhythmias in patients with haemodialysis, found that 20% of these patients had SCD or bradyarrhythmia events necessitating pacemaker implantation, and 33% of these patients had an arrhythmic endpoint. Interestingly, the median time to event was 2.6 years, confirming the need for long-term monitoring. Surprisingly however, bradyarrhythmias were very commonly diagnosed in this cohort suspected to be at high risk for ventricular arrhythmias and sudden cardiac death. 84 Further studies are needed to establish the role of ILR in risk stratification.

| Wearables/direct to consumer
Wearables/direct to consumer Class References Wearables may provide diagnostic data that contribute to disease detection and management when integrated into the clinical context and physician judgement 85,86 The direct to consumer or wearable technology market, comprised of devices that monitor physiological parameters such as heart rate and sleep pattern, is anticipated to grow to 929 million connected devices by 2021. 87

| Biomarkers, tissue, genetics Biomarkers, tissue, genetics Class References
Genetic testing should be considered in several inherited arrhythmic diseases associated with an increased risk of ventricular arrhythmia and SCD [95][96][97] MRI with LGE to detect fibrosis and scar may be useful in assessing the risk of arrhythmic events in AF patients and patients with cardiomyopathies [98][99][100] Plasma NT-proBNP may be useful in differentiating patients with higher vs. lower burden of AF [101][102][103][104][105] Plasma CRP or other inflammatory markers may be useful in risk assessment, for identifying individuals with increased risk of future AF and for identifying individuals with high degree of atrial fibrosis [106][107][108] The use of biomarkers, tissue biopsy, and genetic assessment can be used for risk assessment in patients suspected of specific arrhythmias or syndromes. The utility of using these tools broadly spans determining arrhythmic risk, refining a clinical diagnosis and estimating prognosis.

| Biomarkers
Cardiac myocytes express and secrete natriuretic hormones that have a central function on blood pressure regulation, blood volume, and plasma sodium balance. Levels of B-type natriuretic peptide (BNP) and its stable N-terminal peptide pro-BNP (NT-proBNP) are increased in AF. 101 AF burden has been shown to be associated with increased NT-proBNP. 102 In a large meta-analysis consortium, BNP and C-reactive protein (CRP) associate with AF but only BNP was superior to wellknown clinical variables in AF risk prediction. 103 Inflammatory processes and fibrosis are central to pathogenesis of AF, 106,109 and the inflammatory marker CRP is associated with longer AF duration and atrial remodelling. 110

| Genetics
The majority of clinically applicable genetic testing is intended to be driven by phenotype and the pre-test probability of specific diagnosis determines the utility of genetic investigation. 95 Due to incomplete penetrance of genetic arrhythmia syndromes, harbouring a genetic variant with known pathogenicity is almost never solely enough to meet diagnostic criteria for a particular syndrome. 123 For LQTS, part of the diagnostic framework (along with the ECG biomarker of QT prolongation) can include a positive genetic test. 123 Moreover, understanding the genetic diagnosis is important for treatment and prognostication. For example, patients with Jervell and Lange-Nielsen and Timothy Syndrome patients (LQT8) have more malignant clinical courses, 124,125 and for LQT1 the arrhythmic risk depends partly on which region of the channel the mutation affects. 126 In catecholaminergic polymorphic ventricular tachyarrhythmia (CPVT), 127 genetic testing of suspected individuals has a moderately high yield. 95 Identification of an at risk first-degree relative of a CPVT affected individual is essential due to the high penetrance but more so the lethality of this syndrome. 123,128 Similar to LQT1, CPVT due to RYR2 mutations may have some degree of risk depending on where in the ryanodine receptor the mutation falls. 129 Brugada syndrome can be particularly difficult to clinically diagnose and the utility of genetic testing for improving diagnosis is poor. For patients who are clinically diagnosed with Brugada Syndrome the yield of genetic testing is ~30%, 130 the majority of whom harbour SCN5a mutations, a gene associated with a plethora of arrhythmia syndromes. 131,132 Genetic testing can be useful for family members of an appropriately genotype identified proband but is not recommended in the absence of a diagnostic ECG. 95 Using genetics as part of diagnostic criteria for arrhythmogenic cardiomyopathies will be discussed later in the document. Lastly, genetics in AF is a developing area, but certain primary electrical sudden death syndromes have increased AF association as discussed in Patients with inherited rhythm disease (long QT syndrome/short QT syndrome/catecholaminergic polymorphic ventricular tachyarrhythmia/Brugada syndrome) section. For families with a substantial number of AF cases or in early onset AF, 133-136 genetic testing can be considered but the yield is low.

| Artificial intelligence
Machine learning is a broad term of artificial intelligence derived from the extraction of patterns from large data sets. The marriage with healthcare analytics and decision processes has been rapidly forwarded with computerized medical records and the creation of large data warehouses.
A deep neural network was created to analyse raw ECG data from an ambulatory heart monitor and classify it into 12 categories based upon the presence of arrhythmia. Machine learning performed very well with an average under the reviewer operating characteristic curve (ROC) of 0.97 and an average F1 score (mean of the PPV and sensitivity) of 0.837; a score better than an average cardiologist (0.780). 137 Machine learning has been applied to standard ECG characteristics in sinus rhythm to predict incident AF using the eight independent ECG leads (leads I, II, V1-6) through a convolutional neural network. 138 The ROC area under the curve for the detection of AF Machine learning has shown accuracy in predicting mortality and risk stratification of patients with CAD. 141 Machine learning has also been shown to accurately discriminate between athletic hearts compared to hypertrophic cardiomyopathy hearts. 142 Machine learning has great potential in this area of risk assessment because of the large amount of data contained in the large ECG and clinical datasets available to determine rules.

| Patients of advanced age
There is agreement that the prevalence of AF in the general population in the Western world is in the order of 1%-2%. [143][144][145] It is estimated that in 2010 there were 33.5 million people in the world with AF of which 20.9 million were men and 12.6 million were women. 146 During the past 20 years, the age-adjusted prevalence rates of AF increased for both men and women and similarly the corresponding incidence rates have increased. [146][147][148][149][150] Age is a major risk factor for the development of AF and in persons younger than 55 years a prevalence of AF around 0.5% is seen whereas in persons older than 85 years AF prevalence is around 15% (Figure 1). 144 A stepwise increase in AF prevalence with increasing age has been found in several studies. 152,153 Studies in a multi-ethnic cohort from the United States has shown large variation in AF prevalence among various race-ethnicity groups in which AF associated hospitalizations were lower in Hispanics, Chinese, and Black Americans compared to White Americans. 153 The predominant contributor to the increasing AF prevalence is our aging populations, more widespread use and availability of screening tools, and improved treatment for various heart diseases that enhance longevity.
Among AF patients, those aged younger than 65 years are in general healthier than those older than 65 years. 154 Life time risks of AF in 55-year-old subjects without a history of AF have been found to be 20%-24% in the Rotterdam study 155 but considerably higher at 37% in the Framingham study. 134 The lifetime risk of AF in Asians older than 20 years (1 in 6 for men and 1 in 7 for women; i.e. 14%-17%) was lower than the risk reported from Western countries. 156 The incidence rates, prevalence, and lifetime risk of AF are higher for men than women. Despite this, the absolute number of women with AF exceeds the total number of men with AF because women live longer than men. 144 Women have their first episode of AF about 5 years later than men and less commonly have lone AF. 144 In general, women with AF are more likely to have hypertension or valvular heart disease compared to men. 144 Women often present with atypical symptoms related to AF ( Figure 2). On the other hand, compared to men, women are less likely to have asymptomatic AF, they have a higher symptom burden, they have higher average heart rate during AF and more often longer lasting episodes of AF. 144 These factors contribute to the observation that women are more likely to contact their physician due to AF-related symptoms compared to men.
Conflicting results exist with respect to risk of stroke secondary to AF and its prognosis in women compared to men. [157][158][159] There does not seem to be a gender difference with respect to development of dementia secondary to AF, although women have higher rates of dementia than men in general. 145,157 Since both AF and stroke are highly associated with age and stroke may occur as a complication of AF it seems reasonable to consider screening for this arrhythmia in elderly populations. Several studies are ongoing and expected to be finalized within the next couple of years. These studies are expected to guide us with respect to cost-effectiveness of these screening strategies.

| Patients with heart failure
Due to common risk factors like age, hypertension, diabetes, obesity, and sleep apnoea, AF and HF are intricately linked and share common pathophysiologic mechanisms. Atrial fibrillation occurs in more than half of individuals with HF and presence of both carries greater mortality risk compared with those without either condition. 167 In the particular case of cancer treatment, HF is also a common consequence of cardiotoxicity associated with some chemotherapeutic agents, including anthracyclines, human epidermal growth factor receptor 2 (HER2), and proteasome inhibitors. In this setting, A careful evaluation of clinical characteristics known to be associated with increased risk for AF should be performed 160 Frequent interrogation or remote monitoring of stored arrhythmia episodes in device implanted HF patients should be performed in order to diagnose AF and allow its early management 161 Investigations needed to assess risk for AF in patients with heart failure Class References Echocardiography is useful in identifying cardiac characteristics associated with a higher risk for AF 162 Cardiac MRI may be considered in identifying degree of atrial fibrosis and scar 163 Use of biomarkers may be considered for identifying individuals with increased risk of future AF and for identifying individuals with high degree of atrial fibrosis 107,164,165 Searching for common genetic variants associated with AF risk by genetic molecular analysis has not been found to be useful in a routine clinical setting 166 unknown, it seems plausible that the negative effect on the cardiac systolic function also plays a central role. 168 Given the deleterious effects of AF in HF patients, significant interest has been directed to risk factors predicting the development and progression of this arrhythmia ( Figure 3).

| Clinical risk factors
Older age and male gender are associated with a higher risk of developing AF. 160 Diabetes confers a 1.4-to 1.6-fold higher risk for AF. 160 Because of its high prevalence in the general population, hypertension is responsible for more AF in the population (14%) than any other risk factor. 160 Obesity and sleep apnoea are independent risk factors for AF. 169 AF incidence also increases in case of renal or thyroid dysfunction. 170,171 With regard to HF and the type of underlying heart disease, prevalence of AF increases significantly with the severity of HF symptomatology. Among the valvular diseases, the left-sided valve stenoses have the highest prevalence rates of AF. In addition, the presence of CAD or hypertrophic cardiomyopathy is a significant risk factor for incidence and progression of AF. 172 Finally, in congenital heart disease patients, substantial AF rates appear decades before their onset in the general population. 173

| Electrocardiography
Electrocardiogram-derived variables, such as the PR interval, ECGbased left ventricular hypertrophy (LVH), P wave indices like P wave duration, area, and terminal force have been used in various AF prediction models but their additive value over other clinical risk factors is minimal. 174 Short duration Holter monitoring is not useful for AF detection in asymptomatic patients. Longer duration monitoring with external or implantable loop recorders may help when paroxysmal AF is suspected. In addition, frequent interrogation or remote monitoring of Holter memories in device implanted HF patients is mandatory in order to diagnose AF and allow its early management. 161

| Biomarkers
Markers of inflammation (high-sensitivity CRP, fibrinogen), atrial overload (atrial and B-type natriuretic peptides), myocardial ischaemia (high-sensitivity troponin T and I), cardiac fibrosis (galectin-3), and others (soluble ST2, growth differentiation factor-15), have been studied to predict AF incidence. 165 Of these, only natriuretic peptides have consistently demonstrated added predictive value beyond information on clinical variables. 164,165

| Imaging
Many echocardiographic variables have been associated with a significantly higher AF recurrence rate. Possibly, left atrial volume is superior to left atrial diameter in predicting progression to persistent AF. Speckle left atrial strain and stiffness index can also predict the maintenance of sinus rhythm after cardioversion for AF. 162 Concerning MRI, the amount of left atrial enhancement quantified on MRI with LGE may be helpful to predict progression of AF, 163 but the reproducibility of such findings remains controversial.

| Genetics
A family history of AF in a first-degree relative independently increases AF risk two-fold. 175

| Patients with obesity, hypertension, diabetes, sleep apnoea, or structural heart disease
The assessment of underlying AF in people at higher risk for AF can be considered from opportunistic perspective, or the consideration of clinical risk prediction tools. 180  Many of these conditions are present concomitantly. Also, obesity and hypertension are commonly associated with sleep apnoea, which is another risk for incident AF.
Obesity has been associated with incident AF, 182 but clinical trial data have a suggestion of an 'obesity paradox' whereby overweight AF patients tended to have improved outcomes; however, the relationship between obesity and outcomes from real-world observational cohorts are less clear. [183][184][185] In a systematic review of trial and real-world evidence, there was suggestion of an obesity paradox in AF patients, particularly for all-cause and cardiovascular death outcomes. 184 An obesity paradox was also evident for stroke/systemic embolic event outcomes in the non-vitamin K antagonist oral anticoagulant (NOAC) trials, with a treatment effect favouring NOACs over warfarin for both efficacy and safety that was significant only for normal weight patients. Nonetheless, proactive management of obesity is part of the lifestyle advice for patients with AF.
On a population basis, hypertension is the most common aetiological factor for AF, and contributes to its complications. Indeed, AF can be regarded as a manifestation of hypertension target organ damage. The optimal blood pressure targets in AF patients have been described, being 120-129/<80 mm Hg. 186 Also, longer hypertension duration is associated with the increased risk of ischaemic stroke; however, this long-term effect of hypertension duration can be attenuated by long-term strict SBP control throughout the entire duration of hypertension. 187 Poor diabetes control is associated with incident AF. In the diabetic AF patient, longer disease duration is related to a higher risk of stroke/thromboembolism in AF, but not with a higher risk of anticoagulant-related bleeding. 188 These risks were similar for Type 1 and Type 2 diabetes. 189 Evidence of other target organ damage such as diabetic retinopathy increased risk, although it did not add to the predictive value of risk assessment using the CHA 2 DS 2 -VASc score. 190 Indeed, the ATRIA study also confirmed that duration of diabetes is a more important predictor of ischaemic stroke than glycaemic control in patients who have diabetes and AF. 191 Unsurprisingly SHD is a potent risk factor for incident AF, as well as its complications, such as stroke and HF. 177,192  This score could potentially be considered to target the high-risk patients that may be suited for more intense screening for incident AF, e.g. post-stroke where the C2HEST score was superior to the other scores such as the Framingham score. 178 The risks of AF with associated valvular heart disease are well recognized, as recently discussed in an EHRA position document. 193 In terms of HF, there is a link between AF complications and HF, whether HF with a reduced EF (HFrEF) or HF with a preserved EF (HFpEF). 194 In the CHA 2 DS 2 -VASc score, the 'C' component refers to recent decompensated HF, irrespective of the EF, or the presence of moderate-severe systolic dysfunction whether asymptomatic or not. 7 Of note, the CHA 2 DS 2 -VASc score is predictive of stroke in HF, whether or not AF is present. 195

| Patients who have undergone cardiac surgery Patients who have undergone cardiac surgery Class References
Heart rhythm monitoring for 4-7 d is recommended for detection of post-operative AF

Patients who have undergone cardiac surgery Class References
Patients with post-operative AF may undergo follow-up rhythm monitoring to assess for the presence of symptomatic and asymptomatic arrhythmias [196][197][198][199] Post-operative AF remains the most common complication following cardiac surgery and its incidence ranges between 20%-50% across numerous studies. 196  The majority of post-cardiac surgical AF occurs within the first 4 post-operative days, and is most common on the 2nd post-operative day, while recurrences are most common on the 3rd post-operative day. 197,203 In another study of CABG patients, 94% of post-operative AF occurred by the 7th post-operative day. 198 Hence rhythm monitoring such as inpatient telemetry or ECG for post-operative AF should focus on this time frame.
While post-cardiac surgical AF likely occurs as a result of the interaction between acute perioperative triggers and the underlying atrial and cardiac substrate, its occurrence identifies a subset of patients associated with long-term morbidity and mortality. In a study of patients who underwent CABG, post-operative AF conferred an eight-fold increased risk of future AF and doubled cardiovascular mortality on long-term follow-up. 199 Follow-up rhythm monitoring, for example with ECG or Holter monitoring is advisable in this subset of patients particularly in the setting of symptom development.
There is emerging data on the use of implantable cardiac monitors for long-term monitoring of this subset of patients. While implantable cardiac monitors allow continuous long-term monitoring for arrhythmias and asymptomatic arrhythmias, the risk-benefit ratio is balanced by the arrhythmia detection rate beyond the immediate post-operative period and level of invasiveness of the monitoring device. Its routine use will depend on further results from prospective medium to long-term studies.

| Patients with cryptogenic stroke Patients with cryptogenic stroke Class References
Patients should initially undergo brain diffusion-weighted MRI imaging for the diagnosis of cryptogenic stroke. 204,205 AF is more likely to be detected after cryptogenic stroke with more intense investigation with longer and more sophisticated monitoring. [205][206][207] Long-term ECG monitoring techniques, such as transtelephonic ECG monitoring or cardiac event recorders or ILR can increase yield of AF diagnosis after cryptogenic stroke in selected patients. 205,206 The use of an ILR should be considered for detecting AF in selected patients who are at higher risk of AF development, including the elderly, patients with cardiovascular risk factors or comorbidities. 80,207  LGE (MRI)

Family history SuscepƟbility Genes
Patients with cryptogenic stroke Class References TOE may lead to the reclassification of cryptogenic stroke because many cases are embolic and due to a cardiogenic source, mainly AF. 205,206 Cryptogenic stroke is defined as ischaemic stroke of undetermined aetiology. 208 The diagnosis of cryptogenic stroke is generally made by exclusion. Although cryptogenic stroke includes few potential causes, such as paradoxical embolism through a patent foramen ovale, atrial septal aneurysm, and aortic arch atheroma, the majority of cases are thought to be caused by cardio-embolism due to undetected paroxysmal AF. 205

| Atrial fibrillation risk in athletes-general
Paroxysmal or persistent AF is common in athletes and may be autonomically mediated or triggered by other supraventricular tachycardias. 215 AF is the primary arrhythmia observed in middle-aged athletes. 216 AF in athletes tends to be paroxysmal, vagally mediated, and highly symptomatic. 213 The mechanism of increased AF risk at either end of the physical activity spectrum likely includes autonomic, structural, inflammatory, and fibrotic changes to the heart.
For example, increased vagal tone, which is often observed in the endurance athlete, has been shown to result in a short atrial refractory period, and thus initiates AF. 217

| Atrial fibrillation risk in athletesexercise paradox
Recent studies have observed a U-shaped risk relationship of physical activity to AF. At one end of the spectrum, a large observational study 218,219 of people showed that those at the lowest levels of physical fitness had a 5-fold increased risk of AF. 220 Increasing the physical activity of sedentary patients could help reduce the risk or burden of AF. Long-term endurance training, as well as a sedentary lifestyle, 221 increase chronic systemic inflammation, which in turn could also facilitate AF. 106 For example, one randomized study demonstrated that just 12 weeks of moderateintensity physical activity decreased the AF burden by 41%. 222 Of the physically inactive with AF, the obese might benefit the most from moderate levels of physical activity. 220 In contrast, a metaanalysis of 655 endurance athletes also demonstrated a five-fold increased risk of AF. 212 Of these studies, increased AF risk was generally only observed with the highest levels of physical activity that was maintained over a prolonged period of time. 213

| Atrial fibrillation risk in athletes-structural cardiac changes
Most studies have shown structural changes in endurance athletes, which have resulted in the term athlete's heart. These changes include dilatation of all four heart chambers, increase in left ventricular mass, and mild right ventricular hypertrophy. 223 Studies show that moderate physical activity might reduce inflammatory markers. [224][225][226] Extreme levels of exercise are a known cause of cardiac fibrosis, particularly in hinge point locations of the heart, such as the right ventricle; however, the significance of MRI-detected fibrosis remains controversial. 227 Athletes who experience higher levels of fibrosis also have higher levels of coronary calcium. 228 In turn, fibrosis is a well-established risk factor of AF. 163 In one study, the fibrotic changes caused by vigorous exercise were reversed after an 8-week period of physical activity cessation. 229 Among young elite athletes, age, years of competition, and echocardiographically measured parameters, including left atrial anterior-posterior diameter and atrial strain, were associated with higher AF risk. 230,231 Although increasing physical activity might reduce AF in sedentary patients, decreasing physical activity levels in elite endurance athletes may also reduce AF. 215 Currently, the role of deconditioning to lower AF risk in elite athletes for primary or secondary prevention of arrhythmia requires prospective evaluation.

Patients with inherited rhythm disease Class References
Patients with certain inherited arrhythmia syndromes are at higher risk for AF and benefit from symptom-driven and periodic surveillance 123 Evaluation should include non-invasive symptomdriven surveillance for patients at risk for AF and periodic noninvasive surveillance for asymptomatic patients [232][233][234] EPS to determine atrial AF substrate or susceptibility is not useful. 123 Some patients with primary electrical sudden death syndromes have an increased AF association, including Brugada Syndrome, LQTS, SQT, and catecholaminergic polymorphic ventricular tachycardia (CPVT). These patients are at risk for arrhythmia symptoms from AF and are vulnerable to AF consequences such as pro-arrhythmia and inappropriate ICD shocks.
Brugada Syndrome is characterized by ST-segment elevation in the precordial ECG leads and increased risk of SCD due to VF. 235 Brugada Syndrome is associated with a higher incidence of SVTs, and AF is the most common SVT in these patients. 236 Cognitive assessment should be performed in AF patients where there is suspicion of cognitive impairment. 258,259 Assessment of cognitive function may be multifaceted, and cognitive impairment screening by available tools is just one component. 258 Risk reduction of cognitive dysfunction and its comorbidities in AF may include risk assessment for vascular disease and/or Alzheimer's disease. 258,260 General health measures may reduce the concomitant risks of AF and stroke, with a putative benefit on cognitive function. with score of ≥1 in a male or ≥2 in a female should be considered for stroke prevention strategies. [265][266][267][268] Nevertheless, it has to be kept in mind that no stroke risk scheme has perfect predictive accuracy.
Another major adverse effect of AF is impairment of cognitive function. 258,259 Multiple risk factors for dementia have been identified in the general population, including modifiable and non-modifiable ones. 269 Apart from these AF-non-specific risk factors, AF may lead to cognitive impairment by multiple mechanisms. These include apparent stroke, silent stroke but also other mechanisms that are independent of thromboembolism. 270  Decline in the Elderly (IQCODE) may be applicable. 258 In addition, more comprehensive assessments may be done after appropriate referral to a psychiatrist, geriatrician, or neurologist. 258

| Risk assessment for stroke/transient ischaemic attack status post-left atrial appendage occlusion/ ligation Risk assessment for stroke/TIA after LAA occlusion/ligation Class References
TOE after 6 weeks and if necessary after 1 year is useful for detecting peri-device residual flow, incomplete appendage ligation, or device-related thrombus to identify patients at higher risk of stroke 271,272 Clinical features such as previous TIA/stroke, persistent AF, low LVEF, vascular disease, and early discontinuation of anticoagulation may be helpful to guide decisions regarding imaging for device related thrombus 273,274 Multi-detector CT and cardiac CT angiography have been found to be equivalent to TOE to detect peridevice flow 275,276 After surgical occlusion or exclusion of the left atrial appendage, imaging may be useful to look for a residual appendage and its function or a residual leak after ligation to guide decisions regarding anticoagulation [277][278][279] Left atrial appendage (LAA) occlusion/ligation using one of several devices or surgical techniques has been developed as an alternative to anticoagulation in high-risk patients with non-valvular AF. [280][281][282] The maximum experience has been with the Watchman device (Boston Scientific), which has been found to be non-inferior to warfarin in patients who are still candidates for short-term warfarin treatment. [283][284][285] Results of comparison between LAA occlusion/ligation and NOACs are awaited. Current guidelines recommend use of LAA occlusion as a possible strategy in patients having contraindications to long-term anticoagulation. 279 The residual risk of stroke/TIA following LAA occlusion/ligation can be related to procedural or patient related risk factors. Among the procedure related factors, peri-device leak, and device-related thrombus are important factors for thrombo-embolic events in short and medium term after the procedure. Stroke risk is significantly elevated in patients in whom LAA ligation fails after surgical 286 or percutaneous approaches. 287 Post-procedure surveillance is therefore important to assess long-term risk of stroke and need for continued anticoagulation.
These may be detected on TOE immediately or after few weeks/ months. 271

Risk for heart failure incidence and prognosis Class References
Screening for AF in patients with HF should be performed because of the increased risk of adverse cardiovascular outcomes in combination more than the risk conveyed by either disease state alone. 288,289 Interval use of echocardiography and arrhythmia directed monitoring for development of AF-induced cardiomyopathy and risk assessment over time should be part of standard follow-up for patients with AF. 290,291 Atrial fibrillation and HF are conditions that coexist in many patients, and sometimes it will be difficult to establish if HF was the cause of AF or AF caused HF (tachycardia-induced cardiomyopathy). 288,292 In the Framingham study, 41% of patients with AF and HF developed HF first, 38% developed AF first, and in the remaining 21%, AF and HF occurred at the same time. 289 AF is associated with a three-fold increased risk of incident HF. 293 In trials of patients with chronic systolic heart failure, the prevalence of AF was 4% in patients with Class I symptoms, 10%-27% in patients with Class II-III symptoms, and 50% for those with Class IV HF symptoms. 291 Additionally, aging and the structural and neurohormonal changes in HF make the development and progression of AF much more likely.
The risks of developing an AF-induced cardiomyopathy appear to be related to the ventricular rate during AF and the duration of AF.
However, the precise incidence of tachycardia-induced cardiomyopathy with AF, in patients with and without SHD is unknown.
The mechanisms and pathophysiology of AF and HF share several risk factors and common pathophysiologic processes. Hypertension, smoking, obesity, diabetes, renal impairment, sleep apnoea, and CAD are all associated with an increased risk of developing both HF and AF, and each condition increases morbidity and mortality when associated with the other. All types of HF (HFpEF or HFrEF) are associated with an increase prevalence of AF. 294,295 There are no studies examining the role of monitoring to detect AF in asymptomatic pa-

Risk for death in AF patients (including risk for SCD) Class References
Clinical characteristics of the patient including presence of advanced age, cognitive dysfunction or dementia, diabetes mellitus, hypertension, prior stroke, vascular disease, and HF should be used as important risk markers of higher mortality in patients with AF. 299,300 Atrial fibrillation is associated with 1.5-to 2-fold higher risk of all-cause mortality which may result from stroke, HF, or SCD. 279 Of the mortality associated with AF, only 1 in 10 deaths are stroke, and >7 out of 10 are cardiovascular. 301 A multipronged strategy incorporating stroke prevention, better symptom control, and cardiovascular risk optimization is associated with improved outcomes, including a reduction in mortality. 3,4 Females with AF have slightly higher mortality compared to male patients. Ethnic or racial differences exist in mortality risk, with one study showing highest risk in African Americans among all racial/ethnic groups. 302 Also, presence of comorbidities increases the risk compared with 'lone' AF. Advanced age, renal failure, pulmonary disease, and HF have been found to be most important risk factors for higher mortality in AF ( Figure 5). 299,300 Numerous risk scores have been designed to assess the mortality risk in AF. The CHA 2 DS 2 -VASc score was designed to assess stroke risk, but given it is a cluster of common risk factors for cardiovascular mortality also predicts mortality risk. 303 More complex clinical risk scores designed to predict mortality, such as an integrated GARFIELD-AF risk tool, statistically improves mortality prediction, being superior to the CHA 2 DS 2 -VASc score. 304 All clinical risk scores only have modest predictive value (c-indexes 0.6-0.7) but can always be statistically improved by the inclusion of cardiac biomarkers, such as NT-proBNP and hs-TnT. Both biomarkers (and others) have been found to be independently associated with increased midterm mortality in AF patients presenting to emergency room. 305 Indeed, risk scores incorporating biomarkers have been proposed, such as the ABC-death risk score, which utilizes age, biomarkers, and clin- is not static but changing with increasing age and incident risk factor(s), thus repeat risk re-assessment is more appropriate given that a change in risk scores is more highly predictive of adverse outcomes.
Importantly, many biomarkers are non-specific, more likely reflecting a patient with significant comorbidities and significant

| Post-ablation atrial fibrillation recurrence
Post-ablation AF recurrence is one of the most important and frequent adverse outcomes, which occurs in 30%-50% of cases. 328,329 In fact, although the acute success rate of AF catheter ablation seems high, achieving a durable treatment efficacy has remained a main challenge. 279

| Other adverse outcomes
Apart from AF recurrence, according to the available real-world data, around 5%-15% of patients undergoing AF catheter ablation experience complications, mainly during the index hospitalization

Risk of adverse outcomes in patients treated with catheter ablation Class References
Patients that undergo an AF ablation should be monitored closely in the first 30 days after the procedure due to a higher risk of neurological, gastrointestinal, cardiovascular, vascular and peripheral complications [320][321][322][323][324][325] Wolff-Parkinson-White syndrome patients following radiofrequency ablation may benefit from additional follow-up due to a persistent elevated risk of developing AF compared to the general population 296,326 and early in the post-procedure course. [320][321][322][323][324][325]

Mortality and morbidity
The impact of the ablation on hard clinical endpoints is much less evident. Previous findings from observational studies indicated a positive effect of the procedure on mortality and morbidity. 352 These, however, were not confirmed in the recent large rand-

| Catheter ablation in Wolff-Parkinson-White patients
Careful attention must be given in WPW patients who underwent RF ablation, as it was demonstrated that they had an increased risk of AF at follow-up when compared to general population, though an increased risk of death was not reported. 297,326

| Risk of adverse outcomes in patients treated with surgical Maze
The surgical Cox-Maze operation was introduced in 1987 to treat patients with refractory AF. 355 This surgical approach carries more risk of complications than the catheter ablation procedure, and is suitable for selected patients only. In this setting, we can observe three different case-scenarios.

| Atrial fibrillation surgery
A simplification of the Cox-Maze procedure was proposed by replacing the 'cut and sew' lesions by different ablation devices and minimally invasive access. 356 In the recent years, bipolar RF clamping devices guided on a beating heart, by thoracoscopic epicardial approaches have been introduced. 277

| Surgical Maze in patients with concomitant heart surgery
An AF surgical ablation procedure is reasonable for selected patients with AF undergoing cardiac surgery for other indications. 279 In patients that may receive a concomitant Maze procedure, a shared decision-making strategy should be used with an AF heart team to make the best decision available for the patient and their heart condition. 358

| Stand-alone surgical Maze
A stand-alone AF surgical ablation procedure may be reasonable for selected patients with highly symptomatic AF not well managed with other approaches (e.g. after a failed catheter ablation, longstanding AF, dilated left atrium  Cardiac MRI with a LGE can be considered in order to evaluate arrhythmogenic substrate including myocardial scarring to include in risk assessment, and guide a possible VT ablation procedure. This investigation should be preferably performed before ICD implantation to avoid artefacts due to the presence of an implanted device 370 For more than 20 years, patients with a history of sustained VT/VF have been recognized to be at high risk of recurrence. 371 Nowadays, these patients are given a Class I (Level of Evidence A) indication for ICD implantation. 70 For this reason, the practical usefulness of VT/ VF recurrence risk assessment is questionable, as additional testing is likely not going to influence decision pathways (i.e. catheter ablation or antiarrhythmic drug therapy as an alternative to ICD implantation), and patient outcomes in a secondary prevention setting.

| Primary prevention of ventricular tachyarrhythmia/ventricular fibrillation in patients with ICM and a left ventricular ejection fraction ≤35%
Patients presenting with ICM, in NYHA Class II-III, with EF ≤35% after 3 months of optimized heart failure pharmacological treatment, are given a Class I/A indication for ICD implantation for the

Primary prevention of VT/VF in patients with ICM and LVEF ≤35% Class References
ICM substrate and ischaemic triggers for VT/VF must be evaluated when appropriate (coronary angiogram, functional ischaemic evaluation by nuclear scan, stressechocardiography or MRI) 54,70,71 Cardiac MRI with a LGE can be considered in order to evaluate arrhythmogenic substrate including myocardial scarring to include in risk assessment and guide a possible VT ablation procedure. This investigation should be preferably performed before ICD implantation to avoid artefacts due to the presence of an implanted device 370 primary prevention of SCD. 70 Nonetheless, it is widely recognized that only a small subgroup of these patients will present with VT/ VF during follow-up, and consequently will benefit from the device. A better risk stratification of these patients would be crucial to help identify those who would indeed benefit from an ICD. Most of the numerous investigations assessed in this setting, like programmed ventricular stimulation (PVS), heart rate variability (HRV), late ventricular potentials (LVP), baroreflex sensitivity, QT interval dispersion, T-wave alternans, and heart rate turbulence have been largely abandoned because none of them have influenced routine clinical practice. 46,73,372,373 However, some of these explorations, like T-wave alternans, have shown some value for SCD prediction in ICM patients. 42 It is still uncertain whether biochemical markers as B-type natriuretic peptide and N-terminal pro-BNP will prove useful in assessing risk for VT/VF. Cardiac MRI with LGE should also help to improve VT/VF and SCD risk stratification by analysing cardiac structure and myocardial scarring. 376 Finally, a recent randomized trial suggests that assessment for hibernating myocardium performed routinely is of no use to decrease the risk of SCD. 68

| Primary prevention of ventricular tachyarrhythmia/ventricular fibrillation in patients with ICM and left ventricular ejection fraction >35%
This group of patients should be the priority for VT/VF risk assessment: in absolute numbers, it represents by far the highest number of those at risk of VT/VF and SCD. 369 In addition, these patients are currently non-protected, as they are not targeted for ICD implantation in guidelines, due to their LVEF value. 70 In this setting, MRI with LGE could be an option to better understand the diagnosis, prediction, and treatment of VT/VF. 370 This investigation could possibly help improve VT/VF and SCD risk stratification by analysing cardiac structure and myocardial scarring, particularly when EF is relatively preserved. In this setting, a large prospective trial documenting that treatment guided by MRI-based risk stratification improves outcomes in this patient group is still very much expected. 376 Otherwise, the MUSTT Trial suggested the value of EPS for improving the SCD risk stratification, in the subgroup of ICM patients with a residual EF comprised between 30 and 40%. 377 In addition, other non-invasive investigations like tissue Doppler Imaging (TDI) seem also to be of potential value in predicting VT/VF in ICM. Late diastolic velocity assessed by TDI, particularly when detected in the inferior myocardial wall, seems to be a sensitive marker of future VT/VF. 374 Finally, it is well known that non-sustained ventricular tachycardia (NSVT) is a marker of increased risk of VT/VF and arrhythmic death. During the convalescent phase after an acute coronary syndrome, NSVT seems to be associated with an increased risk of cardiovascular death, most marked within the first 2 months after detection. 375 The use of such investigations could help to detect those patients at higher risk of VT/VF, more particularly during the early phase after an acute coronary event. Specific measures like prolonged monitoring or use of wearable cardiac defibrillator could be undertaken on an individual patient-case basis. However, more solid data are needed to support such recommendations broadly.

| Patients with non-ischaemic heart failure
Patients with non-ischaemic heart failure Class References MRI may be considered for further risk stratification of sudden death in patients with non-ischaemic cardiomyopathy who do not otherwise meet an indication for ICD implantation 378 EPS may be considered for further risk stratification of sudden death in selected patients with non-ischaemic cardiomyopathy who do not otherwise meet an indication for ICD implantation 378 Patients with non-ischaemic HF represent a broad and diverse group of patients including those with progressive and infiltrative forms of cardiomyopathies. For this reason, the risk of developing VT in non-ischaemic HF is difficult to accurately predict in this group of patients. Subsequent sections in this document will address specific conditions that have unique risk profiles including inflammatory cardiomyopathies, congenital heart disease, arrhythmogenic cardiomyopathy, and Chagas' disease.
Prior investigations into identification of the risk of developing VT in non-ischaemic cardiomyopathy focused on the risk of SCD and the role of the implanted defibrillator for primary prevention.
The DANISH trial 61 reported no survival benefit from prophylactic ICD implantation in the overall cohort. Implantable cardioverter-defibrillator reduced SCD to half, and subgroup analysis showed that in patients younger than 68 years, survival was prolonged with an ICD. Although pooled analysis of the five primary prevention trials (DEFINITE, SCD-HeFT, CAT, AMIOVIRT, COMPANION,

Primary prevention of VT/VF in patients with ICM and LVEF >35% Class References
ICM substrate and ischaemic triggers for VT/VF must be evaluated when appropriate (coronary angiogram, functional ischaemic evaluation by nuclear scan, stress-echocardiography or MRI) 54,70,71 EPS and non-sustained VT evaluation could be considered to improve VT/ VF risk stratification in patients with relatively preserved LVEF, particularly in the convalescent phase (first 2 months) after an acute coronary syndrome 312,374,375 Heart rate variability (HRV), LVP, baroreflex sensitivity, QT-interval dispersion, T-wave alternans and heart rate turbulence have not been evaluated adequately in this population for generalized use 73,372,373 and DANISH; n = 2970) revealed that ICD therapy was superior to medical therapy in patients with non-ischaemic cardiomyopathy with decreased cardiac function, these trials were judged globally negative. 379 In a limited number of studies outside of these clinical trials, the role of EPS or non-invasive programmed stimulation has revealed inconsistent results. 378 More recently, the role of cardiac MRI for definition of scar and potential substrate has emerged as a powerful risk stratification tool in observational studies. 49,380,381 Genetic testing is also useful in patients with decreased cardiac function with conduction disturbance (i.e. LMNA mutations).
In summary, non-ischaemic HF includes a diverse group of patients with reduced ventricular function due to cardiomyopathies from different aetiologies, and at high risk for VT. Reduced cardiac function remains a powerful predictor of VT and appropriate ICD therapy in these patients as a primary prevention. Cardiac MRI and EP testing shows promise in some subsets. Further characterization based on the type of cardiomyopathy leading to HF shows the most promise for accurate assessment of VT risk.

| Patients with inflammatory cardiomyopathies Patients with inflammatory cardiomyopathies Class References
In patients with non-ischaemic heart disease who present with ventricular arrhythmias, use of cardiac MRI or cardiac PET can help delineate aetiology of non-ischaemic cardiomyopathy, initiate aetiology-driven treatment, and evaluate prognosis. 52,53,380 Inflammatory cardiomyopathies encompass a broad spectrum of disorders characterized by myocardial inflammation as the primary cause of cardiac dysfunction. This includes viral myocarditis (commonest cause), cardiac sarcoidosis, giant cell myocarditis, autoimmune myocarditis associated with underlying connective tissue diseases, eosinophilic cardiomyopathies, and Chagas disease (addressed in a separate chapter).
In patients who present with ventricular arrhythmias and diagnosed with non-ischaemic cardiomyopathy, the incidence of inflammatory cardiomyopathy may be as high as 50%. 382  In addition, the distribution of LGE confers important prognostic information, with mid-wall anteroseptal LGE representing a more malignant form compared to a sub-epicardial inferolateral wall LGE pattern. 388,389 Inflammatory biomarkers, such as C-reactive protein, are typically lower in this group with septal LGE, but biomarkers of myocardial damage such as troponin are typically higher, suggestive of a subset with less inflammation but greater myocardial injury.
F-fluorodeoxyglucose (FDG)-PET is advantageous for detecting active inflammation in cardiac sarcoidosis, and a mismatch of FDG and perfusion and involvement of the right ventricle predicts adverse cardiac events and ventricular arrhythmias, respectively. 53 Endomyocardial biopsy is performed in cases where a histological diagnosis is required to confirm cardiac sarcoidosis or giant cell myocarditis, with its yield enhanced by electrogram guidance. Active viral genomes may also be identified by biopsy, which can differ significantly from peripheral serological tests. 383,390 Little data exist on how to assess risk of VT/VF in inflammatory cardiomyopathies. Besides EF, which is used for all non-ischaemic aetiologies, no randomized studies have evaluated other parameters or even EF as a predictor of VT in different inflammatory cardiomyopathies. In particular, certain inflammatory cardiomyopathies may carry higher risk than others (sarcoidosis vs. viral myocarditis). Risk of ICD therapy may be as high as 15% per year in biopsy proven cardiac sarcoidosis patients. 391 Although randomized data on use of higher EF in these patient populations is lacking, given risk of VT noted in retrospective studies, use of MRI and cardiac PET to evaluate aetiology of non-ischaemic heart disease is warranted, and treatment of inflammation to reduce risk of VT is advised. Furthermore, cardiac PET and MRI can be used to assess for recurrent inflammation or progression of disease on treatment.

| Patients with congenital heart disease
Ventricular arrhythmias in patients with congenital heart disease (CHD) may be observed in two different groups: the paediatric age group and adults with repaired congenital defects group. 398 In the paediatric age, life-threatening VT is rare both prior to and after sur-

| Patients with inherited arrhythmia diseases (inherited channelopathies and inherited structural diseases including arrhythmogenic right ventricular cardiomyopathy)
Patients with inherited arrhythmia disease are without doubt at increased risk for ventricular arrhythmias, including SCD. The extent to which this is pertinent and predictable is different for the various conditions.
The main primary inherited arrhythmia syndromes, i.e. the 'channelopathies' are LQTS, Brugada syndrome and CPVT. 402 Patients that are symptomatic (syncope, cardiac arrest) at the time of presentation are at highest risk, with arrhythmic syncope representing a sentinel sign of risk, and resuscitated cardiac arrest reflecting the highest risk cohort. 97 Despite major social impact on perceived risk, family history is not of major importance in all three diseases.

Risk for ventricular arrhythmias in patients with congenital heart disease Class References
In the paediatric patient with CHD, ventricular overload, surgical scars and patches or baffles, ventricular dysfunction, and previous conduction defects are recognized risk factors for VT. [392][393][394] In adult patients with CHD, older age at surgery, poor haemodynamic status, and prolonged QRS represent the most common risk factors for ventricular arrhythmias. [393][394][395] In adult patients with CHD, VTs are mainly observed after correction of tetralogy of Fallot (TOF) and left ventricular outflow tract defects. [395][396][397] In patients with TOF, residual haemodynamic lesions and ventricular dysfunction represent the most important risk factors for VT or SCD. [395][396][397] In patients with TOF, frequent PVCs, QRS >180 ms, palliative systemic to pulmonary shunts, syncope, atrial tachycardia, decreased LVEF, dilated right ventricle, severe pulmonary stenosis or regurgitation, are risk factors for sustained VT.

Risk for ventricular arrhythmias in patients with inherited arrhythmia diseases Class References
Patients with primary inherited arrhythmia syndromes and cardiomyopathies should undergo risk stratification that integrates clinical presentation, family history, and non-invasive diagnostic testing 400 Select patients with primary inherited arrhythmia syndromes and cardiomyopathies may benefit from electrophysiologic testing to refine non-invasive risk stratification 401 In LQTS, clearly defined disease-specific risk factors are the extent of resting QT prolongation, documentation of arrhythmias and gene and even mutation specific associated risk. 403 In CPVT, the extent of the arrhythmic response of an exercise test predicts events, including breakthrough symptoms on therapy. 404

Risk stratification of ventricular arrhythmias in ARVC Class References
In patients with ARVC, history of aborted sudden death, sustained ventricular arrhythmias, and severe right and/or left ventricular dysfunction identify a high risk of cardiac death 413,414 In patients with ARVC, advice to not perform high-level or endurance exercise should be given. 415,416 Clinical factors including age, male sex, unexplained syncope, nonsustained VT, number of anterior precordial leads with T wave inversion, and genetic mutation status can be used for prognostic stratification of patients with ARVC 413,414 In patients with confirmed ARVC, regular Holter monitoring and imaging for assessment of ventricular function may be useful. 415,416 A detailed history of exercise intensity and duration may be helpful in patients with ARVC as exercise level may represent a modified risk factor of adverse cardiovascular events and disease progression 417 In arrhythmogenic right ventricular cardiomyopathy (ARVC or ),

| Patients with Chagas disease Patients with Chagas disease Class References
The Rassi score is useful in assessing risk of death in Chagas disease patients 347,348 In patients with syncope and a BBB, an invasive EPS is useful in assessing risk of sustained ventricular arrhythmias 349,350 When available, cardiac MRI with LGE should be considered to evaluate for arrhythmogenic substrate as part of a risk stratification strategy in those patients with cardiomyopathy [351][352][353][354] Chagas disease is an infectious disease affecting 10 million people around the world and 100 million more are at risk of this A single ICD shock is associated with a two-to five-fold increase in mortality, and progressive heart failure has been reported the most common cause of mortality among these patients. 428

| Appropriate shock predictors
A previous episode of sustained VT correlates with high rate of appropriate shocks. [433][434][435][436] A higher risk of appropriate therapy was seen in a secondary prevention ICD group when compared with a primary prevention ICD group at 5-year follow-up, while the rate of inappropriate therapy was comparable. 437 Several studies have shown male sex as an independent risk factor for appropriate ICD therapies. 438 Women are 30%-50% less likely to receive an appropriate shock, [439][440][441][442] and this difference is more pronounced among CRT-D recipients. [443][444][445] However, most of studies have shown similar mortality rates in both genders after ICD implantation. 438

Risk for heart failure incidence and progression Class References
Periodic monitoring of PVC burden (every 6 months) and LVEF and dimensions are useful in patients with frequent, asymptomatic PVCs and a normal LVEF and dimensions 461 PVC burden exceeding 20% is associated with a higher risk of PVC-related cardiomyopathy [462][463][464] PVC burden lower than 10% is associated with a lower risk of PVC-related cardiomyopathy 465,466 In patients with PVC-related cardiomyopathy, absence of LGE on cardiac MRI may be used to identify patients with a favourable prognosis of left ventricular systolic function recovery [467][468][469]  However, no prospective longitudinal assessments have been conducted that definitively prove their causal relation to PVC-induced cardiomyopathy. 472 The diagnosis of tachycardia-induced cardiomyopathy or PVCrelated cardiomyopathy can be challenging and the role of imaging modalities in the characterization of myocardial tissue as part of the diagnostic workup is limited. 467 Cardiac MRI with LGE can accurately identify the presence and extent of myocardial scar and has become a first-line non-invasive imaging modality for the aetiologic assessment of primary cardiomyopathies and/or left ventricular systolic dysfunction, and could identify early stage of the structural heart disease.

Risk for death in VT patients (including risk for SCD) Class References
Risk for SCD should be judged in each patient on a case-by-case basis and risk considered as a continuous variable rather than a dichotomized variable (high or low risk may change) [473][474][475] Individual risk assessment needs to be dynamic as the type and severity of risks can change over time (repeated measurements need to be made over time) 476 Risk assessment may include consideration of mode of death as the relative risk of non-sudden, non-cardiac death, sudden cardiac death, and non-sudden cardiac death is influenced by aging and worsening cardiomyopathy and cardiovascular risk factors 370,477,478 Risk prediction of death in VT patients has used numerous

| Risk of adverse outcomes in patients treated with catheter ablation
Risk of death or acute haemodynamic compromise in patients who undergo catheter ablation of ventricular arrhythmias is driven by patient-specific factors (comorbidities), procedural factors, and presentation of the patient. In a large retrospective multicentre registry, factors such as low EF, chronic kidney disease, VT storm, and unmappable VTs were associated with early mortality. 489 As mentioned above, male sex is associated with occurrence of VT/VF and ICD shocks. 490 As procedural factors are often difficult to determine prior to the procedure, various risk scores have been developed to assess risk of acute haemodynamic compromise and/or death in patients undergoing catheter ablation of VT. Of these, a modified version of the Seattle HF Model and PAINESD score have been used in single centre and multicentre retrospective studies to evaluate risk of acute haemodynamic compromise or death post-procedure. 486,487,489 The Seattle HF Model incorporates, amongst other variables, age, EF, blood pressure, weight, gender, HF medications, blood electrolyte, and haemoglobin levels as well as NYHA to predict mortality.
A modified version of this model which incorporates VT storm and ICD shocks was recently reported to be potentially more useful in predicting 6 months survival in patients who undergo VT ablation. 488 The PAINESD score incorporates pulmonary disease, age, presence of ischaemic cardiomyopathy, NYHA, EF, VT storm, and diabetes and assigns a score between 3 and 6 to each of these patient characteristics. In retrospective studies, patients with a PAINESD score greater than 15 had a 24% risk of acute haemodynamic compromise and a significantly higher risk of mortality. 487 With regard to VT recurrence, in addition to patient related comorbidities, large single centre and multicentre studies have shown that the risk of VT recurrence is driven by the underlying aetiology, particularly in patients with non-ischaemic heart disease, even after adjusting for other patient comorbidities. [492][493][494] In particular, patients with Lamin A/C cardiomyopathy, hypertrophic cardiomyopathy, cardiac sarcoidosis, and valvular cardiomyopathy appear to be at higher risk for VT recurrence after catheter ablation as compared to idiopathic dilated cardiomyopathy. 485,492 In addition, location of scar seems to determine risk of VT recurrence post-catheter ablation. 495 In this regard, endocardial ablation alone may be insufficient in many non-ischaemic cardiomyopathies. In arrhythmogenic right ventricular cardiomyopathy, epicardial presence of scar can serve as the substrate for VT and combined endo-epicardal mapping and ablation or adjuvant epicardial ablation after endocardial ablation is often required. [496][497][498][499] Cardiac MRI with LGE can be used in assessment of scar location and may be beneficial in diagnosis and peri-procedural planning of VT ablation. 500 Retrospective studies have shown that inducibility of VT at the end of ablation is associated with adverse outcomes, even after adjusting for other patient comorbidities. Non-inducibility of VT in ischaemic cardiomyopathy patients was shown to be associated with improved arrhythmia-free survival rates and all-cause mortality, 501,502 even after adjusting for other comorbidities. In addition, inducible clinical VT during non-invasive programmed electrical ventricular stimulation (PES) is associated with decreased 1-year VT free survival as compared with those who are not inducible (<30% vs. >80%) 503 Patients who were non-inducible during non-invasive PES after ablation had a VT recurrence rate of only 9% at 1 year of follow-up when both acute (at the end of the procedure) and late (at

Risk of adverse outcomes in patients treated with catheter ablation Class References
The aetiology and severity of cardiomyopathy and inducibility of arrhythmias after VT ablation are useful in determining risk of recurrence of VT after catheter ablation 485 Risk scores in combination with procedural characteristics may be useful for assessing adverse outcomes associated with catheter ablation of VT [486][487][488] 6 days post-procedure) programmed stimulation were negative. 504 Therefore, PES may be used to guide redo ablation and address ICD programming.
Finally, although catheter ablation is generally performed after the occurrence of ICD therapies, two clinical trials reported the value of catheter ablation prior to or in conjunction with ICD implantation. The Prophylactic Catheter Ablation for Prevention of Defibrillator Therapy clinical trial randomized patients with spontaneous ventricular tachycardia or fibrillation and history of myocardial infarction to ICD or ICD and catheter ablation. In this trial, 30-day mortality was zero along with a significant reduction in ICD therapies from 31% to 9% between the control (ICD) and intervention arms (ICD + catheter ablation). 505 The Catheter Ablation of Stable Ventricular Tachycardia before Defibrillator Implantation in Patients with Coronary Heart Disease (VTACH) trial randomized patients with history of myocardial infarction and stable VT to catheter ablation followed by ICD implantation vs. ICD implantation alone and showed that catheter ablation reduced occurrence of VT or VF by 18% at 2 years of follow-up. These data imply that in patients who receive ICD for secondary prevention and have ischaemic heart disease, catheter ablation can be considered earlier, at the time of ICD implantation, to reduce future ICD therapies and prior to potential presentation with VT storm. 506 The impact of early ablation (at the time of ICD implantation) on mortality was the subject of the BERLIN-VT clinical trial, early results of which have indicated a lack of a difference in death or hospitalization for VT/VF in the deferred group (ablation after occurrence of third appropriate shock) vs. those who underwent prophylactic ablation at the time of ICD implantation. 507 It is important to note that in these studies, patients had a history of VT or VF. In patients with ischaemic heart disease undergoing ICD implantation for primary prevention of sudden cardiac death, prophylactic substrate modification of scar by catheter ablation requires further investigation. In the Substrate Modification Study, patients randomized to ICD implantation plus VT ablation had similar time to VT recurrence as those who underwent ICD implantation only. However, catheter ablation at the time of ICD implantation was associated with a greater than 50% reduction in total number of ICD therapies throughout the follow-up period. 508

| Patients with ventricular premature contractions Patients with ventricular premature contractions Class References
An evaluation of cardiac function and screening for heart failure symptoms should be considered in patients with frequent ventricular ectopy (>10 000 PVCs within 24 h or >10% over a more extended timeframe) 509

Patients with ventricular premature contractions Class References
An evaluation of cardiac function and screening for heart failure symptoms may be considered in patients with frequent multiform PVCs, PVCs with a QRS duration > 150 ms or PVCs with a coupling interval of <450 ms 510,511 Frequent PVCs can lead to cardiomyopathy and HF, and are associated with increased mortality. 509 In addition, in some patients with an inherited arrhythmogenic cardiomyopathy, PVCs may be the initial clinical manifestation that leads to this diagnosis. An initial case series describing four patients who had reversal of cardiomyopathy after amiodarone successfully suppressed a high PVC burden has resulted in the recognition for the potential reversibility of this condition. 463 However, only a minority of patients with PVCs will develop symptoms or adverse sequelae. The factors that can potentially predict development of HF and increased risk of adverse outcomes include PVC frequency as well as characteristics of the PVC morphology and timing of the PVC coupling interval.

| Premature ventricular complex frequency
In a large cohort of patients, increased PVC frequency was associated with reduced LV function, a higher incidence of heart failure, and a higher risk of death. Specifically, compared to the lowest quartile of PVC frequency (<0.002%), the highest quartile (0.123% to 17.7%) in this cohort of patients with a structurally normal heart at baseline had a 31% increased risk of death over a follow-up of >13 years. 509 Other studies correlating frequency with PVC-induced cardiomyopathy suggested a threshold effect observed at >20%, though there is no accepted cut-off that appears to be protective. 462,510 In a study of 239 consecutive patients with apparently normal hearts, a PVC burden of >20 000 in 24 hours was associated with a reduced LVEF, whereas >10 000 but <20 000 showed LV dilation with preserved LVEF. 512

| Premature ventricular complex morphology
In addition to PVC burden, the morphological features of the PVC have been evaluated. The width of the PVC QRS complex, perhaps reflective of dyssynchrony, has been associated with increased risk of developing PVC-induced cardiomyopathy. 510,511 In these retrospective studies, patients with a PVC duration of >150 milliseconds appeared to require a lower burden for development of a cardiomyopathy. A PVC duration of >153 milliseconds in patients with a >10% burden, was associated with an 82% sensitivity and 75% specificity for subsequent development of a cardiomyopathy. The presence of multiform PVCs has also been associated with the development of new onset heart failure. 513

| Premature ventricular complex coupling interval
One mechanism of PVC-induced cardiomyopathy may be due to ineffective mechanical contraction leading to adverse remodelling, possibly related to the timing of the PVC. However, there are only a few small studies evaluating this. In a retrospective cohort study of 510 patients, a PVC coupling interval of <450 milliseconds was associated with a reduced LVEF. 514 Another smaller study of 70 patients did not show any association, though its power was limited. 515 Another study specifically identified the presence of interpolated PVCs regardless of coupling interval as associated with reduced LVEF. 516 A short PVC coupling interval may also be an important determinant of VF, especially in patients with genetic or acquired early or abnormal repolarization. 42,517,518 While the promise of effective treatment for reversing the potential adverse cardiac effects of frequent PVCs remains a possibility, it remains unclear whether such patients can easily be identified.
Most cardiologists accept the dose-response relationship of PVC burden and reduced cardiac function, although the precise threshold for this effect remains unknown. There also is the potential for other factors aside from frequency alone, such as PVC QRS duration and coupling intervals, to influence adverse events associated with frequent PVCs.

| Patients with supraventricular tachyarrhythmia such as Wolff-Parkinson-White syndrome and focal atrial tachycardia
Patients with supraventricular tachyarrhythmia such as WPW syndrome and focal atrial tachycardia Class References EPS, with the use of isoprenaline, is recommended to risk stratify individuals with asymptomatic pre-excitation who have high-risk occupations/hobbies, and those who participate in competitive athletics [519][520][521] EPS should be considered for risk stratification in asymptomatic pre-excitation patients without high-risk occupations or those who are not competitive athletes 519,521,522 Non-invasive screening with exercise testing, drug testing, and ambulatory monitoring may be considered for risk stratification in asymptomatic pre-excitation patients without high-risk occupations or those who are not competitive athletes 519,521,522 Patients with supraventricular tachyarrhythmia such as WPW syndrome and focal atrial tachycardia Class References High-risk features to consider at EPS with or without catecholamine challenge are accessory pathways with an antegrade refractory period ≤250 ms, shortest pre-excited RR interval during AF ≤250 ms, inducible atrioventricular reentrant tachycardia, and multiple accessory pathways 519,523,524 Observation without treatment may be reasonable in asymptomatic WPW patients who are considered to be at low risk following EPS, abrupt loss of pre-excitation during exercise testing, or due to intermittent pre-excitation on a resting ECG or during ambulatory monitoring 519,521 Patients with WPW may experience dramatic adverse events including SCD due to VF. 521 The estimate for the frequency of SCD ranges up to 4% with more recent studies reporting a rate of 2%. 519 Alarmingly, in approximately half of the patients SCD is the first clinical manifestation of the syndrome rendering appropriate risk stratification essential. 520 Risk assessment strategies have been recently reviewed in the 2019 ESC Guidelines for the management of patients with supraventricular tachycardia. 525  A short pre-excited RR interval during AF ≤250 milliseconds and the presence of multiple accessory pathways have been also reported as risk markers. For these reasons, EPS is recommended for risk stratification in subjects with asymptomatic ventricular pre-excitation who either have high-risk occupations or are competitive athletes.
In patients without high-risk occupations or those who are not competitive athletes, EPS should be considered for risk stratification of patients with asymptomatic pre-excitation that can derive a prognostic benefit from prophylactic catheter ablation of the accessory pathway. 525 Permanent Junctional Reciprocating Tachycardia (PJRT) re-presents a rare form of atrioventricular reciprocating tachycardia using a concealed accessory pathway. The incessant behaviour of PJRT may result in tachycardia-induced cardiomyopathy that usually resolves after successful treatment by RF catheter ablation.
Non-invasive testing may also be helpful. Non-invasive findings that identify a pathway not capable of maintaining rapid conduction during AF include intermittent loss of conduction over the accessory pathway on the resting ECG or during ambulatory monitoring, and abrupt loss of pre-excitation during exercise testing. 523,524 Focal atrial tachycardias are characterized by regular atrial activation from atrial areas with centrifugal spread and can be classified as sustained or non-sustained. Sustained focal atria tachycardia in the adult population is usually associated with a benign prognosis, although tachycardia-mediated cardiomyopathy has been reported in up to 10% of patients referred for ablation of incessant SVT. 526 Non-sustained atrial tachycardia is frequently found on Holter recordings and often does not require treatment; however, we should consider that patients with a high premature atrial contractions (PAC) burden (>500/24 h) are at increased risk for developing of AF and be educated on the symptoms of AF. 527

SUMMARY
In clinical practice and for scientific purposes, cardiologists and primary care physicians perform risk assessment in patients with cardiac diseases or conditions with high risk of developing such.
The European Heart Rhythm Association (EHRA), Heart Rhythm Society (HRS), Asia Pacific Heart Rhythm Society (APHRS), and the Latin American Heart Rhythm Society (LAHRS) set down this expert consensus statement task force to summarize the consensus regarding risk assessment in cardiac arrhythmias. Objectives were to raise awareness of using the right risk assessment tool for a given outcome in a given population, and to provide physicians with practical proposals that may lead to rational and evidence-based risk assessment and improvement of patient care in this regard. A large variety of methods are used for risk assessment and choosing the best methods and tools hereof in a given situation is not simple. Even though parameters and test results found associated with increased risk of one outcome (e.g. death) may also be associated with higher risk of other adverse outcomes, specific risk assessment strategies should be used only for the purposes for which they are validated.
The work of this task force is summarized in a row of consensus statement tables.

CO N FLI C T O F I NTE R E S T
None declared.

S U PP O RTI N G I N FO R M ATI O N
Supplementary material is available at Europace online.