Background: Chest pain is one of the most frequent presenting patient complaints in emergency departments (ED) and has an extensive differential diagnosis with very different levels of severity (1). Many of these chest pain presentations require a significant stay in the ED to rule out acute coronary syndromes (ACS). Low-risk chest pain has been defined by consensus guidelines as having a less than 1% risk of a Major Adverse Cardiac Event (MACE) – a composite of death, myocardial infarction (MI) and coronary revascularization (2,3). There is certainly an overuse of troponin ordering in certain low-risk chest pain populations, translating into unnecessary resource utilization and possible downstream patient harm.
The HEART Pathway combines a History, ECG, Age, Risk factors (HEAR) score and serial troponins to stratify patients with acute chest pain and attempt to identify those who most likely do not have ACS that are most suitable for early discharge from the ED without further testing (4). The HEART Pathway ideally reduces hospitalisations from the ED and outpatient cardiac testing, but it is not known if there exists a sub-population of very low-risk patients who could be objectively identified for discharge without any troponin testing at all.
This study sought to measure the MACE rate among very low-risk chest pain patients, as defined by a HEAR score ≤1, and determine whether the HEART Pathway requires troponin testing among very low-risk patients to achieve an accepted missed MACE event rate of less than 1%.
Article: Smith LM et al. Identification of very low-risk acute chest pain patients without troponin testing. Emerg Med J 2020. PMID: 32753395.
Clinical Question: When using the HEART Pathway to risk stratify patients, is there a group of very low-risk chest pain patients (HEAR score ≤ 1) that does not require troponin testing to achieve a MACE miss rate <1%?
- This was a preplanned secondary analysis of the HEART Pathway Implementation Trial. The trial was conducted between November 2013 and January 2016 at three large tertiary hospitals in the Piedmont Region of North Carolina in the United States.
- It used a pre-implementation and post-implementation design with a wash-in period (about 1-2 months) between exposures to allow provider acclimation to the HEART Pathway. Providers used ‘usual care’ for chest pain assessment during the pre-implementation period and the HEART Pathway risk assessment (HEAR scores and serial troponin testing at 0 and 3 hours) during the post-implementation period.
- The secondary analysis used only the post-implementation cohort of adult ED patients being investigated for chest pain due to possible ACS and measured the MACE rate within a 30-day follow-up period. The analysis calculated the diagnostic accuracy of using the HEAR score only or using the HEAR score plus troponin testing to identify a very low-risk group of patients.
- Inclusion: Adult patients over 21 years of age in the post-implementation and wash-in periods presenting with chest pain with a completed HEAR assessment. Patients presenting with chest pain and no evidence of STEMI were eligible for the assessment if at least one troponin was ordered.
- Exclusion: Patients with incomplete HEAR assessments, with an acute ischaemic ECG (≥1mm of ST depression or T wave inversion in contiguous leads) and those with known coronary artery disease (CAD) were not included in this analysis.
- 5799 patients were evaluated
- 820 patients had no HEAR assessment
- 1170 patients were excluded due to being high-risk patients from ACS due to known CAD (n = 828), ischemic ECG (n = 324), and known CAD/ischemic ECG (n = 18)
- This left 3809 patients for analysis
- HEAR Score = 0: 82/3809 (2.2%)
- HEAR Score = 1: 365/3809 (9.6%)
- HEAR Score ≥2: 3362/3809 (88.3%)
- Of the 3809 eligible patients, 3278 had adequate troponin measures so diagnostic performance using HEAR score with troponin was conducted among this group of patients only
- A clinical decision support tool for the HEART Pathway Assessment was fully integrated into the electronic health record (EHR) at each site. The tool was tested, and providers were trained on using it during the wash-in period. ED providers would see an interruptive pop-up alert for the HEART Pathway tool for any adult patient with chest pain and at least one troponin test ordered in the post-implementation and wash-in periods. Patients deemed low risk were those with HEAR scores ≤3 and without elevated troponin values. Low-risk patients were targeted for early discharge without objective cardiac testing and non-low-risk patients were recommended for further testing or admission. For this analysis, patients with a HEAR score of ≤1 were considered very low risk.
- Data from initial ED presentation to discharge from the ED, observation unit or inpatient ward were extracted from the health system. Patient demographics, medical history, laboratory results, providers’ HEART Pathway assessments, disposition, diagnoses and vital status were obtained using pre-validated structured EHR variables or diagnoses and procedure codes. The EHR was used for within-network return visits, along with insurers’ claims data and state death index data to determine 30-day outcomes.
- Primary outcome: MACE within 30 days. MACE is a composite of death, MI and coronary revascularization for any reason (emergent or elective). Coronary revascularization included coronary artery bypass grafting, stent placement or other percutaneous coronary intervention. Patients with incomplete follow-up were considered free of 30-day MACEs.
- Sensitivity along with several other diagnostic accuracy measures (e.g., specificity and negative predictive value (NPV)) were calculated for ruling out or predicting MACE at 30 days for patients with HEAR score = 0, HEAR score ≤1 without troponin, and HEAR score ≤1 with troponin
- The miss rate of a test is 1-sensitivity or the type II error. In this study, it refers to the chance of being identified as being very-low risk among patients who experience MACEs within 30-days. The authors compared the miss rates to a benchmark of <1% set by a group of emergency department clinicians as an acceptable threshold for MACE.
- The NRI was calculated to assess the degree of improvement in classifying patients with HEAR scores ≤1 after including their troponin test results.
- MACE at 30 days occurred in 0.9% (4/447) of patients with a HEAR score ≤1 (2 deaths, 2 MIs, and 0 revascularizations)
- Both deaths occurred due to complications from malignancies that were unrelated to ACS
- In patients with a HEAR score of 0, the MACE rate was 1.2% (1/82; 95%CI 0.03% to 6.6%) while 0.8% (3/365; 95%CI 0.2% to 2.4%) of patients with a HEAR score of 1 had MACE
- Among patients with a HEAR score >1, 5.3% (178/3362) had a MACE at 30 days (12 deaths, 151 MIs, and 81 revascularizations)
- Patients with HEAR scores >1 were significantly older and had higher rates of obesity and smoking than those with HEAR scores ≤1 (p<0.001).
- The sensitivity and NPV for ruling out MACE in very low-risk patients (HEAR score ≤1) was similar and excellent with or without troponin testing
- Sensitivity was 97.8% for HEAR score ≤1 without troponin (95%CI: 94.5%-99.4%) and 99.4% for HEAR score ≤1 with troponin (95%CI: 96.9%-100.0%)
- NPV was 99.1% for HEAR score ≤1 without troponin (95%CI: 97.7%-99.8%) and 99.7% for HEAR score ≤1 with troponin (95%CI: 98.1%-100.0%).
- The miss rate using HEAR score ≤1 without troponin was 2.2% (95% CI: 0.6%-5.5%). Although the sensitivity and miss rate are important to consider when evaluating the accuracy of using the HEAR score without troponin to identify a very low-risk group of patients when risk stratifying patients according the HEART Pathway, the measure that clinicians may be more interested in considering is the false omission rate. The false omission rate using HEAR ≤1 without troponin was 0.9% (95% CI: 0.2%-2.3%), which is the chance that a patient may experience a MACE after having been identified as very low-risk.
- Patients were first classified as very low risk (HEAR score ≤1) or not very low risk (HEAR > 1) for MACE based on the HEAR score only. With the addition of the troponin testing results, patients with HEAR scores ≤1 but with elevated troponin were no longer classified as very low risk
- Troponin testing in patients with HEAR scores ≤1 correctly reclassified two patients with MACE (two MIs) and was elevated among seven patients without MACE, yielding an Net Reclassification Improvement Index (NRI) of 0.9% (95%CI 0.7 to 2.4%).
- Asks a clinically important question about a very common emergency medicine patient complaint
- Employed a robust pre planned statistical analysis with an innovative medical record prompt taking into consideration many confounding variables in the analysis
- Performed a sensitivity analysis including only patients with complete follow-up which did not change results
- No patients died with the use of HEAR score ≤1 without troponin testing, making the estimates of NPV of MACE conservative in this trial
- First trial to identify a large cohort of chest pain patients who are very low risk for ACS and unlikely to benefit from any troponin testing
- It was not a randomized controlled trial (RCT) and as such the time series design has many limitations inherent to its lack of representiveness and randomization
- As well described by the authors, the analysis was done on a smaller subset of a larger cohort which can amplify the effects of verification and selection biases
- Using electronic data to identify events as opposed to say, actually following up with patients may be less accurate and may have missed positive MACE. It is also possible that safety events related to the index visit occurred beyond the 30-day follow-up period
- Specifically looked at chest pain patients, and not anginal equivalents such as nausea, weakness etc.
- All three facilities were using a high-sensitivity cardiac Troponin I as their troponin assay in this study
- Although MACE in patients with a HEAR score ≤1 without troponin was 0.9%, it is important to realize that the 95% CI for MACE extended from 0.2% to 2.3%. This would require further testing and additional validation before adopting this strategy to exclude ACS with HEAR score ≤1 without troponin testing.
- As the authors correctly state, patients using cocaine or other stimulant medications should have troponin testing, as they are higher risk than very low-risk patients with more frequent increases in troponin values. Additionally, I would add, in patients who don’t go to the doctor, they wouldn’t state that they have medical problems when in fact some of them do. This is important to consider as this can falsely lower risk stratification scores
- Not all chest pain is ACS, and I suspect in clinical practice there are many not ordering troponin testing on patients with chest pain that is non-concerning for this entity (i.e., young patient, with no medical problems, with musculoskeletal chest wall pain)
Author Conclusion: “These data suggest that patients with HEAR scores of 0 and 1 represent a very low-risk group that may not require troponin testing to achieve a missed MACE rate <1%”
Clinical Take Home Point:
Using a HEAR score ≤1 without troponin testing to safely disposition patients is certainly interesting, has face validity, and worth validating. However, with 95% CI crossing >2% for MACE at 30d, I am not sure we are at a place where potentially missing this many events would be considered standard care or even safe from a medicolegal perspective.
Guest Post By:
Jonathan Gravel, MD
Academic Family/Emergency Physician
Mount Sinai Hospital and Michael Garron Hospital in Canada
More Thoughts on This Topic Checkout:
- Journal Feed: HEAR Score
- REBEL EM: HEART Score – New ED Chest Pain Risk Stratification Score
- EM Docs: The Heart Pathway
- EM Cases: Low Risk Chest Pain & High Sensitivity Troponin
- Gibbs J et al. Chest Pain Evaluation in the Emergency Department: Risk Scores and High-Sensitivity Cardiac Troponin. Curr Cardiol Rep 2020. PMID: 32472247
- Amsterdam EA et al. Testing of Low-Risk Patients Presenting to the Emergency Department with Chest Pain: A Scientific Statement from the American Heart Association. Circulation 2010. PMID: 20660809
- Pauker SG et al. The Threshold Approach to Clinical Decision Making. NEJM 1980. PMID: 7366635
- Mahler SA et al. The HEART Pathway Randomized Trial: Identifying Emergency Department Patients with Acute Chest Pain for Early Discharge. Circ Cardiovasc Qual Outcomes 2015. PMID: 25737484
Post Peer Reviewed By: Salim R. Rezaie, MD (Twitter: @srrezaie)
Jonathan Gravel, MD
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