A streamlined Emergency Department approach to moderate risk chest pain in patients with no pre‐existing coronary artery disease: A pilot study

Moderate risk patients with chest pain and no previously diagnosed coronary artery disease (CAD) who present to ED require further risk stratification. We hypothesise that management of these patients by ED physicians can decrease length of stay (LOS), without increasing patient harm.


Introduction
Chest pain accounts for approximately 10% of presentations to EDs each year 1 and is the most common cause for ambulance calls in Australia. 2There are many causes of chest pain; however, only around 10% will ultimately have a diagnosis of acute coronary syndrome (ACS), 3 thus, the single most important element of the ED assessment is to identify those with ACS or other life-threatening conditions.
Consistent with worldwide recommendations 4,5  This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Key findings
• The implementation of an ED led approach to moderate risk chest pain in patients with no previously diagnosed coronary artery disease decreased their length of stay.• There was no significant increase in major adverse cardiac events in moderate risk patients with no coronary artery disease referred directly from ED to a rapid access chest pain clinic.

Society of
Australia and New Zealand (NHFA/CSANZ) recommends that patients presenting with symptoms consistent with an ACS receive care guided by a suspected ACS assessment protocol including formal risk stratification using a validated risk assessment tool, thus supporting quantification of 30-day major adverse cardiac events (MACE). 6There is no universally accepted composition of MACE, with studies using various diagnoses as composite end points. 7here is, however, consensus that high risk patients routinely require admission for further management in order to prevent complications 6 whereas low risk patients may be discharged without follow up; but what of those of moderate risk?
NHFA/CSANZ guidelines recommend that further diagnostic imaging be performed on moderate risk patients to provide prognostic information, and that this testing be done during or shortly after discharge from ED 6 with no specific timing suggested.This moderate risk group is, however, a heterogenous group of patients with a risk of MACE somewhere between 2% and 8%, 8-10 10%-20% of whom will already have had previous cardiac imaging, 9 and trying to further delineate risk among the subgroups within this cohort is complex.As such, various management strategies are employed in this group and many of these patients are admitted from the ED for short stay inpatient management, including changes in medical therapy or functional testing.
Traditionally in our ED all patients presenting with chest pain consistent with an ACS were risk stratified following an established approach using the TIMI risk stratification tool. 11Those of moderate risk and not requiring admission for any other reason received a cardiology review prior to discharge with outpatient investigations and follow up.This process was non-selective and could lead to unnecessary delays without patient benefit; patients were not seen overnight, and a recent departmental audit revealed a change in medication in only 2 of 40 patients and no changes in disposition.
Rapid access chest pain clinics (RACPC) have been commonplace in the UK since the late 1990s proving to be a cost-effective and safe alternative to inpatient management. 12espite their use overseas, uptake in Australia has been limited, possibly because of differences in practice; in the UK, many patients with acute chest pain are referred directly from their GP to avoid ED overcrowding, clinics may run daily, 13 and some patients are seen the day of referral, 14 whereas in Australia these patients would be referred to ED. 12 Limited RACPC Australian data has shown low rates of re-presentation in low risk patients 15 and outpatient service improvements 16 but to our knowledge there is no literature addressing the outpatient management of moderate risk patients and the effect on ED length of stay (LOS).
We therefore performed a pilot study to test our hypothesis that a selected group of moderate risk patients with no pre-existing coronary artery disease (CAD) can be safely managed by ED physicians and referred for outpatient testing and follow up as required, leading to a decreased ED LOS.

Methods
A prospective study was performed on patients over 18 years of age presenting to the ED with chest pain consistent with ACS and deemed to be at moderate risk of MACE.Primary outcome measures were LOS and LOS post troponin.The department is in a major tertiary hospital and consists of 54 beds with an additional short stay unit consisting of 15 monitored beds; approximately 110 000 patients are seen per annum.The hospital itself consists of most major speciality services including a coronary care unit, radiology services, and on-site cardiac angiography, interventional cardiology and cardiothoracic surgery.The hospital uses Abbot's High Sensitivity Troponin I (hsTnI) blood test with a value of ≥26 ng/L consistent with myocardial injury.
The new guideline commenced in early August 2021 and pre-specified data collection was over a 6-month period divided into two cohorts of patients: between 1 May 2021 and 2 August 2021 (control group), and 3 August and 31 October (intervention group).Demographic information was collected for each patient and risk factors for CAD; in addition to the total LOS and the LOS following the final troponin measurement.Data was also collected for seven MACE (myocardial infarction, death by any cause, angiography, percutaneous intervention (PCI), congestive heart failure, arrythmia requiring pacing, stroke) at 30 days.Additional follow-up data included investigations arranged, time to and outcomes of those investigations (nil, mild, moderate, or severe disease) as reported by the reviewing radiologist or cardiologist following internationally approved guidelines [17][18][19] ; and whether those patients proceeded to angiography, and PCI or coronary artery bypass grafting (CABG).

Intervention
During the control period patients suspected of having ACS were risk stratified using the TIMI risk stratification tool.Those with a negative troponin and deemed to be of moderate risk were transferred to the ED short stay unit (ESSU) to await a second troponin (Fig. 1).ESSU admission paperwork was completed prior to, or at the time of transfer.During their ED ESSU stay patients were then seen by a cardiology registrar working for the Chest Pain Assessment Unit (CPAU), a virtual unit developed for the purposes of the pathway.Medication changes, further investigations on discharge, and patient follow up were all determined by the cardiology registrar.
During the intervention period the HEART score, 20 including a negative troponin, was used to risk stratify patients (Fig. 2).Following the pathway, patients deemed at moderate risk of MACE were similarly transferred to the ESSU for further troponin testing following completion of a new, more detailed admission form (Fig. 3).This pathway also included a change in troponin (delta troponin) with a value of >3 considered significant, 21 chosen to remain consistent with other local EDs, thus, simplifying the process for rotating doctors.Using the new   guideline patients were then differentiated into those with pre-existing CAD who were still managed primarily by the cardiology registrar and those with no pre-existing CAD, who were managed by the ED physician.Following discharge, patients with no pre-existing CAD were referred both for outpatient cardiac imaging, namely a CT coronary angiogram unless contraindicated, and to a rapid access cardiac follow-up clinic.

Data collection
Electronic data capture and Digital Medical Records were used for data collection across the two periods, and patient demographics, risk factors, LOS, and LOS post troponin were recorded.Patients with preexisting CAD were excluded, resulting in a final study group of moderate risk patients with no pre-existing CAD.
Follow-up data was collected through prospective data collection at the time of cardiology clinic appointment; supplemented by an electronic data review to establish the number of adverse events.Data was de-identified and stored on a secure system.

Statistical analysis
Statistical analysis was performed using IBM SPSS (v23) statistical software suite.Comparison of the control and intervention groups was performed using Chi-squared or Fisher's exact test for categorial data, and independent-samples Mann-Whitney U tests for continuous data.Data for LOS and LOS post troponin were log transformed because of the skewness of the data and linear regression analysis was performed for age and sex.Fisher's exact test was used to compare rates of MACE in the two groups.A P-value of 0.05 was considered significant.

Patient and public involvement
The department's Consumer Advisory Group was consulted during the initial drafting of the new pathway.LOS was determined to be a key factor in a patient's experience of their ED journey and thus a relevant outcome to measure.The study was approved by the hospital's Governance, Evidence, Knowledge, and Outcomes (GEKO) review board (FSFHG GEKO 46492).

Results
Two thousand three hundred fifty-one patient details were reviewed over the 6-month period (Fig. 4), 506 of which were deemed to be at moderate risk of MACE.One hundred eighty-six patients in the moderate risk group had no pre-existing CAD and were therefore included in the final analysis, both groups being similar in number (92 vs 94).There was a significant age difference between the groups (71.5 vs 66.3, P = 0.03) whereas sex and the number of indigenous patients were not statistically different (P = 0.77 and P = 0.51, respectively).There was also no significant difference between the groups with regards to the cardiac risk factors hypertension (P = 0.38), diabetes (P = 0.57), dyslipidaemia (P = 0.76) and smoking history (P = 0.57) (Table 1).
Follow-up data was compared for both groups (Table 3); all patients were followed up at 30 days.There were no incidences of MACE in the control group, and a 2% (2/94) rate of MACE in the intervention group (P = 0.50), where two patients underwent coronary angiography within 30 days.Both incidences of angiography were performed semi electively following a positive CTCA, one of whom progressed to PCI; neither suffered any complication.In total, the ED physicians arranged 42 outpatient cardiac investigations in the 3-month intervention group, the remaining patients either being not suitable because of advanced aged and co-morbidities, or not attending follow up.Thirty-four patients underwent CTCAs.The other eight investigations (six MPS, two Echocardiogram) were arranged because of contra-indications and/or following discussion with the cardiology team.The mean number of days until cardiac investigations were performed was 31.5 (AE17.2) (Table 4).74% (34/42) of patients referred for outpatient investigations were deemed to have no or minimal disease, 10% (4/42) had moderate disease and 16% (7/42) had severe disease.Six patients subsequently underwent angiography, three of which progressed to PCI and two required coronary artery bypass grafting, neither of which was done within 30 days.

Discussion
This pilot study sought to test our hypothesis that a specific group of moderate risk patients with no preexisting CAD can be safely managed by ED physicians and referred for outpatient testing and follow up as required, leading to a decreased length of ED stay.LOS post troponin significantly decreased in our study following implementation of the new guideline, suggesting a much earlier review of patients following their final troponin, possibly aided by a pre-formed discharge plan, leading to earlier discharge from the ED.This intervention also negates the need for specialist input in this select group, thus having the added benefit of freeing up inpatient teams to utilise their time more efficiently.There was also a similar decrease of approximately 1 h in total LOS, although because of the large distribution of LOS in the group, the result was not statistically significant.Total LOS is affected by multiple factors from the patient's initial ED arrival, including assessment, investigations and discharge planning, and a larger study with greater numbers is needed to fully investigate this outcome.
4][25] Our study suggests 30 patients per month would meet criteria for an ED led discharge; with a decrease in 1 h per patient that would equate to over 350 h of ED time saved per year.It may also be that with greater familiarity and comfort in using the guideline this number will increase, thereby decreasing annual bed occupancy further.Not only does this improve ED throughput but also provides a better patient experience. 23espite being well matched for sex and cardiac risk factors there was a significant difference in age between the two cohorts which, despite our analysis adjusting for the difference, may also have had some effect on both LOS and LOS post troponin, as younger patients may be easier to discharge because of less requirements for social intervention.While there is no definitive explanation for this difference in age, it may be that using the newer admission paperwork a more patient focused approach is being undertaken and less co-morbid patients are following the pathway.
Utilisation of a RACPC in Australasia has been shown to decrease re-presentation rates, improve services and increase patient satisfaction 15,16,26 ; we believe this is the first study to show an improvement in ED LOS.The literature has also been limited to low-risk patients or no risk stratification, includes discussion with a cardiologist to establish appropriateness of referrals, and further investigations have been dictated at the time of clinic review.In our study, patients were risk stratified as moderate risk and investigations were arranged directly from ED, further negating the need for cardiology input until after they have been performed.
Despite the moderate risk stratification there were no serious adverse events in our study, with only two patients undergoing angiography within 30 days, one of whom progressed to PCI; this was despite a follow-up time to initial cardiac investigation being on average 31 days post ED discharge.Consistent with recent data suggesting a MACE of 1.7% in moderate risk patients with no pre-existing CAD, 10 this lack of MACE despite a prolonged time to testing suggests that the pathway is relatively safe, although a study of this size was not powered to detect a statistical difference in MACE between the cohorts and this needs confirmation by a larger study.
Almost three quarters of patients who received follow-up investigations had no or minimal disease suggesting that ischemia was unlikely to be the underlying cause of their chest pain despite being at moderate risk of MACE.This may be used to reassure patients and physicians that further testing for CAD in these patients is not required 17 which in turn may rationalise medication use and could potentially lead to a decrease in ED re-presentations. 15

Limitations
As a result of the specific group of patients targeted, this pilot study analysed only a small sample of patients over 6 months with a large distribution in LOS.It is, therefore, difficult to make too many assumptions regarding the intervention until a larger study is completed.There was a very small percentage of indigenous patients within our patient cohort, limiting its transferability to areas with larger indigenous populations.It is also a single centre study and thus influenced by local departmental and hospital factors such as staffing levels and availability of outpatient cardiac investigations that may not be as accessible at other sites thus limiting the generalisability of our findings to other healthcare settings.
As alluded to previously, LOS is affected by many factors, including those associated with input (volume of patients waiting to be seen), throughput (time to process patients) and output (exit block and discharge planning) 22 ; these factors will influence departments differently.Furthermore, LOS may be affected by seasonal illnesses and influences such as holidays.Our study took place over the winter months in Australia when patient numbers are traditionally higher, and a different result may be obtained during the warmer months.

Conclusion
Our initial pilot study suggests that moderate risk patients with chest pain and no pre-existing CAD can be safely managed by emergency physicians and discharged for outpatient follow up, thus streamlining their ED management and decreasing LOS.This pathway could be used in other centres following confirmation of the results by a larger study.

Competing interests
None declared.

Acknowledgement
Open access publishing facilitated by The University of Notre Dame Australia, as part of the Wiley -The University of Notre Dame Australia agreement via the Council of Australian University Librarians.

Data availability statement
The data that support the findings of this study are available on request from the corresponding author.The data are not publicly available due to privacy or ethical restrictions.

Figure 1 .
Figure 1.TIMI pathway used during the control period.

Figure 2 .
Figure 2. pathway used during the intervention period.

Figure 3 .
Figure 3. HEART short stay admission form used during the intervention period.
the National Heart Foundation of Australia & Cardiac Correspondence: Associate Professor Christopher L Jones, Department of Emergency Medicine, Fiona Stanley Hospital, Perth, WA 6150, Australia.

TABLE 1 .
Comparison of the control and intervention groups

TABLE 3 .
Comparison of MACE at 30 days

TABLE 4 .
Outcomes of patients referred for further cardiac investigations CTCA studies were performed privately; therefore, the exact date of study is unknown.CTCA, CT coronary angiogram; MPS, myocardial perfusion scan; PCI, percutaneous intervention; SE, stress echocardiogram.

TABLE 2 .
Comparative data for Total LOS and LOS post troponin