Which Patients Are Safe to Discharge?

Using a single undetectable hs-troponin after three hours of symptom onset or a negative delta two-hour hs-troponin regardless of symptom onset, in combination with normal serial ECGs, not only rules out myocardial infarction in the vast majority of patients but also lowers the posttest probability of 30-day MACE to below 2 percent, a level below which ancillary testing may cause more harm than the risk of ACS itself.⁵

The addition of the HEART score to the pathway lowers the predicted 30-day MACE rate to less than 1 percent.¹¹ Using this decision tool identifies patients considered safe for early discharge. While the HEART score was initially designed to predict the likelihood of ACS in ED patients presenting with acute chest pain, it has now been robustly validated using both conventional and hs-troponin to predict 30-day MACE, leading to a 2018 ACEP Level B recommendation for its use in patients being evaluated for non–ST-elevation acute coronary syndrome or suspected ACS.³

Which Delta HS-Troponin Is Best?

The one-hour delta troponin algorithms perform well; however, the rule-out delta and rule-in delta are often different by only a few nanograms, which may be within the variation of the assay itself.¹² Consequently, misclassification on the basis of assay variation alone may occur. The studies validating one-hour algorithms were done in ideal conditions with samples being batch-tested on a single analyzer with the same lot of reagents. In the real world with multiple analyzers testing samples over time, assay variation is likely to be higher than observed in published studies. With two-hour delta troponins, there is less risk of misclassification from assay variation. Three-hour algorithms have not been shown to be any more accurate than two-hour algorithms.¹³

Is Ancillary Testing After the Initial ED Visit Necessary?

With such a highly sensitive pathway using hs-troponins and HEART score, ancillary testing after the initial ED workup has come under scrutiny. Exercise treadmill stress tests have a false-positive rate as high as 80 percent, leading to unnecessary angiograms, cardiac stents, and even bypass surgery.¹⁴ In ED patients with chest pain and no evidence of acute myocardial infarction, stress testing is associated with higher rates of invasive procedures without reductions in death or myocardial infarction.¹⁵

The 2018 ACEP clinical policy recommends against routine use of ancillary testing prior to discharge in low-risk patients in whom myocardial infarction has been ruled out.³ It argues that limiting complex, expensive, and time-consuming testing can reduce patient cost, emergency department and hospital length of stay, and patient anxiety caused by unnecessary stress testing and potentially false-positive results, once adequate acute myocardial infarction rule-out and risk stratification have occurred.

The American Heart Association guideline recommends that hospital systems establish an agreed-on standard approach to minimize medicolegal risk.¹⁶ Sit down with your cardiologists and hash this out so there is an agreed-upon algorithm that makes sense based on the literature. An algorithm for low-risk chest pain patients that includes hs-troponin and does not include routine ancillary testing is the most reasonable approach based on the current body of literature. Efforts should also be focused on patient education so they understand their incredibly low risk of MACE as well as the significant risks of ancillary testing.

What’s the bottom line? A single undetectable hs-troponin after three hours of symptom onset or a delta two-hour hs-troponin T less than 4 ng/L plus normal serial ECGs and a HEART score of 0–3 rules out acute myocardial infarction and lowers the predicted 30-day MACE to well below 1 percent, a threshold below which ancillary testing may lead to more harm than benefit.

Does clinician judgment (ie, gestalt) matter anymore? On one hand, gestalt is inherent in part of the HEART score (“suspicious” history). However, data on how gestalt performs out of the context of clinical decision tools are emerging, so this remains an open question.