Incidence and predictors of early and late sudden cardiac death in hospitalized Japanese patients with new‐onset systolic heart failure

Abstract Background Patients with heart failure (HF) and low left ventricular ejection fraction (LVEF) are at high risk of sudden cardiac death (SCD). Optimal HF treatment can improve LVEF and reduce the risk of SCD. The aim of this study was to evaluate the incidence and predictors of SCD in Japanese patients with new‐onset systolic HF and to investigate factors that affect LVEF improvement. Methods We retrospectively studied 174 consecutive hospitalized patients with new‐onset HF and LVEF ≤35% (median age, 66 years; men, 71%). The primary outcome was a composite of SCD, sustained ventricular arrhythmias, and appropriate implantable cardioverter‐defibrillator therapy. Results The cumulative rates of meeting of the primary outcome at 3, 12, and 36 months after discharge were 3.9%, 8.1%, and 10.5%, respectively. Atrial fibrillation was a significant predictor of the primary outcome within 12 months after discharge (odds ratio, 5.87; 95% confidence interval [CI], 1.60–21.57). Among 104 patients who completed follow‐up echocardiography within 12 months after discharge, changes in LVEF were inversely associated with SCD (odds ratio/1% increase, 0.78; 95% CI, 0.65–0.93). A QRS duration <130 ms and a B‐type natriuretic peptide level <170 pg/mL were predictors of LVEF improvement to >35% (odds ratio, 3.69; 95% CI, 1.15–11.77; odds ratio, 3.19; 95% CI, 1.33–7.69, respectively). Conclusions Our results showed a high incidence of meeting of the primary outcome within 12 months after discharge in hospitalized patients with new‐onset systolic HF. An improved LVEF may reduce the risk of late SCD.


| INTRODUC TI ON
Sudden cardiac death (SCD) is a major cause of cardiovascular death in patients with systolic heart failure (HF). 1,2 Low left ventricular ejection fraction (LVEF) is a potential indicator of SCD in patients with myocardial infarction and/or HF. [3][4][5][6] Previous landmark trials have shown that the use of implantable cardioverter defibrillators (ICDs) reduced all-cause mortality, including that from SCD, in patients with systolic HF or prior myocardial infarction. [5][6][7] However, previous clinical trials reported that early implantation of ICDs did not reduce mortality in patients with myocardial infarction. 8,9 There have been no clinical trials evaluating the benefit of early implantation of ICDs in patients with new-onset nonischemic HF. 10 Optimal medical therapy or interventions such as revascularization could improve LVEF within several months and improve prognosis in patients with new-onset systolic HF or myocardial infarction, [11][12][13][14] and they would not depend on the presence of an indication for ICD implantation. An observational study reported that LVEF improvement is associated with a decrease in the risks of all-cause mortality and appropriate shocks in HF patients receiving ICDs for the primary prevention of SCD. 15 Previous studies revealed that nonischemic etiology, as well as short HF duration/new-onset HF, are associated with an early improvement in LVEF in patients with systolic HF. [16][17][18] In Japan, the prevalence of ischemic HF is approximately 30% of hospitalized patients with HF, and nonischemic HF is more common. [19][20][21] Moreover, most patients with acute myocardial infarction receive early coronary revascularization, and a low prevalence of SCD in Japanese patients with myocardial infarction has been reported. 22 However, there have been few reports regarding the incidence of SCD during the early period after hospital discharge or on how long we should protect against SCD in Japanese patients with new-onset HF and low LVEF. The aim of this study was to evaluate the incidence and predictors of early and late occurrences of SCD or sustained ventricular tachycardia (VT)/fibrillation (VF) after discharge in hospitalized Japanese patients with new-onset systolic HF and to investigate factors that affect LVEF improvement.

| Patients
In this retrospective observational study, 174 consecutive hospitalized patients with new-onset HF and LVEF ≤35% who were admitted to our hospital between January 2014 and April 2016 were enrolled.
We searched the inpatient database of our hospital and then confirmed that the patients had an LVEF of ≤35% by echocardiography during hospitalization. Among these patients, we identified consecutive patients with new-onset (de novo) HF in whom LVEF ≤35% was detected during the index hospitalization by reviewing the patient medical records. New-onset HF was defined as a first-time diagnosis of HF. HF was defined as new or worsening signs and symptoms of HF, such as fatigue, dyspnea, edema, elevated venous pressure, crepitations, and additional use of diuretic drugs or treatment with intravenous inotropes and/or vasodilators, noninvasive positive pressure ventilation, respirators, or mechanical support. We excluded patients if the previous hospitalization for worsening HF was documented. Moreover, we also excluded patients who had a history of sustained VT/VF ( Figure 1).
We collected information on baseline clinical characteristics and treatment during hospitalization from the medical records of our hospital. Acute myocardial infarction was defined on the basis of the fourth universal definition. 23

| Outcomes
The primary outcome was a composite of SCD, sustained VT/VF, and appropriate ICD therapy for VT/VF. SCD was defined as a nontraumatic, unexpected death occurring within 1 h of the onset of symptoms or an unexpected death within 24 hours of having last been seen as well. Secondary outcomes included all-cause death and the recovery rate of LVEF in 104 patients who completed follow-up echocardiography within 12 months after discharge. The LV volume and LVEF were measured using the modified Simpson's method. An improvement in LVEF was defined as more than 35%. Patients were followed until death or June 2020. patients. An ICD shock was delivered when triggered by VF or if the antitachycardia pacing failed to terminate VT. selected based on previously reported predictors of clinical outcomes, such as age <60 years, female sex, eGFR ≥60 mL/min/1.73 m 2 , plasma brain natriuretic peptide (BNP) level <170 pg/mL, 24,25 ischemic etiology, use of β-blockers, use of ACEIs/ARBs, use of cardiac resynchronizing therapy (CRT), and electrocardiographic and echocardiographic parameters. Multivariate analysis was performed using a forward stepwise method, with entry or removal based on a P value of <.05. A P value of <.05 was considered to be statistically significant.

| Patient characteristics
The median age was 66 years, and the proportion of males was 71%. Among the patients, nonischemic cardiomyopathy was the most common etiology, and ischemic etiology accounted for 28% of cases. Persistent atrial fibrillation was observed in 25% of patients, and nonsustained VT was detected in 34% of patients during hospitalization (Table 1).

| Outcomes
During the median follow-up period of 51     Table S1. Within 3 months after discharge, 6 (3.7%) of 162 patients who were discharged alive experienced SCD or received appropriate ICD therapy. A total of 11 patients (6.8%) experienced SCD, had sustained VT/VF, or received appropriate ICD therapy within 12 months after discharge, and the details of these patients are presented in Table S2. The etiologies of heart disease vary, and 5 patients experienced NSVT during hospitalization. Basal rhythm in 6 of 11 patients was atrial fibrillation at discharge. Although 9 of 11 patients received β-blockers, only 2 patients took the guideline-recommended maximum dose of β-blockers and the others took <50% of the maximum dose. Multivariate analysis showed that atrial fibrillation was a significant factor associated with the occurrences of SCD and ventricular arrhythmias within 12 months after discharge (Table 3).

F I G U R E 2
Kaplan-Meier curves of the primary outcome (a composite of sudden cardiac death, sustained ventricular tachycardia/fibrillation, and appropriate implantable cardioverterdefibrillator therapy) (A) and all-cause death (B) in patients with new-onset systolic heart failure who were discharged alive follow-up echocardiography. The SCD trend was a lower incidence in patients with an LVEF improved to >35% than in patients without an LVEF improved to >35% (0/52 vs 4/52, P = .06). The odds ratio for SCD was 0.78 (95% CI, 0.65-0.93) for every 1% increase in LVEF.
The incidence of all-cause death was lower in patients with an LVEF improved to >35% than in patients without an LVEF improved to >35% (3/52 vs 11/52, P = .02). The odds ratio for all-cause death was 0.91 (95% CI, 0.84-0.97) for every 1% increase in LVEF. Multivariate analysis showed that a narrow QRS duration (<130 ms) and low BNP level (<170 pg/mL) at discharge could be predictors of an LVEF improvement to >35% (Table 4).

TA B L E 4 Factors associated with
improved left ventricular ejection fraction 12 months after discharge; (4) patients with an improved LVEF had significantly lower rates of SCD or all-cause mortality than patients without an improved LVEF; and (5) a narrow QRS duration and low plasma BNP level were independent predictors of improved LVEF.

| Early incidence of ventricular arrhythmia
Recent guidelines recommended that ICDs should be implanted after 3 months or more of optimal medical therapy for patients with HF and LVEF ≤35%. 26,27 However, the risk of SCD or ventricular arrhythmia does not decrease until LV systolic function improves.
During the initiation and optimization of HF therapy, patients with newly diagnosed HF and low LVEF are reported to be at high risk of SCD. 28 During this period, cardioprotective therapies such as β- Several observational studies of patients with WCDs showed that 1.6%-4.8% received an appropriate WCD shock within 2 or 3 months among patients with low LVEF and a high risk of SCD, mostly with newly diagnosed ischemic or nonischemic cardiomyopathies. [29][30][31][32] In our study, 6 (3.7%) of 162 patients who were discharged alive experienced SCD or received an appropriate ICD shock within 3 months after discharge. This result was compatible with previous studies. Our study showed a high incidence of SCD or sustained VT/ VF within 3 months after discharge as well as a relatively high incidence up to 12 months after discharge. In other words, we should treat patients with new-onset HF and low LVEF, recognizing that they are at high risk of SCD during this period. The mechanisms of early SCD occurrence after hospital discharge might be caused by hemodynamics that are not fully stabilized, electrophysiologic effects due to stretched myocardial fibers, neurohormonal activation such as increased sympathetic activity, rapid atrial fibrillation, inflammation, and transient ischemia or electrolyte imbalance that are not yet well controlled by medical HF treatment. In this study, half of the patients who met the primary outcome within 1 year after discharge had atrial fibrillation. Atrial fibrillation was also a significant factor that affected the early occurrence of SCD and ventricular arrhythmias in this study. Atrial fibrillation is known to be a potential risk factor for SCD in patients with several heart diseases such as HF, hypertrophic cardiomyopathy, and prior myocardial infarction. 33 Although the mechanism of the relationship between atrial fibrillation and SCD is not fully understood, atrial fibrillation with rapid and irregular heart rate may induce ventricular arrhythmias via electrical and structural remodeling of ventricular myocytes. The effect of β-blockers on mortality is diminished for patients with systolic HF and atrial fibrillation. 34,35 It is controversial as to how long after the initiation of HF therapy in patients with new-onset HF there is a risk of SCD, but from our results, it cannot be concluded that a 3-mo risk reassessment is sufficient.

| Changes in LVEF and outcome
Our study showed that 50% of patients who underwent followup echocardiography showed an improvement in LVEF to >35%

| Study limitations
Our study was a single-center, retrospective, observational design. To minimize selection bias, we enrolled consecutive patients, but 23 patients were lost to follow-up. The number of patients was relatively small. Although only 6 patients received CRT-D/ ICD, ICD detection, and therapy programming were not identical.
Nonessential ICD therapy for the possibility of self-terminating/ nonsustained VT could not be excluded. Because the incidence of late SCD (later than 12 months after hospital discharge) was low, the effect of an improvement in LVEF to >35% on late SCD or significant clinical factors that predict late SCD could not be demonstrated from this small sample size study. The patients in this study were hospitalized during the period when ivabradine and angiotensin receptor-neprilysin inhibitors were not available in Japan. At present, these drugs may also have a contributing role in improving LVEF.

| CON CLUS IONS
Our results showed a high incidence of meeting of the primary outcome criteria within 12 months, especially within 3 months, after discharge in hospitalized patients with new-onset systolic HF. An improvement in LVEF to >35% within 12 months after discharge was a significant factor related to reduced risks of subsequent SCD and all-cause mortality.

ACK N OWLED G M ENTS
We thank Dr Kotaro Arai and Dr Kyomi Ashihara for their support.