Early noninvasive cardiac testing after emergency department evaluation for suspected acute coronary syndrome

Importance Professional guidelines recommend noninvasive cardiac testing (NIT) within 72 hours of an emergency department (ED) evaluation for suspected acute coronary syndrome. However, there is inexact evidence that this strategy reduces the risk of future death or acute myocardial infarction (MI).

Objective To evaluate the effectiveness of early NIT in reducing the risk of death or acute MI within 30 days.

Design, Setting, and Participants This retrospective, multicenter cohort study within the Kaiser Permanente Southern California integrated health care delivery system compared the effectiveness of early noninvasive cardiac testing vs no testing in patients with chest pain and in whom acute MI was ruled out who presented to an ED from January 2015 to December 2017. Patients were followed up for up to 30 days after emergency department discharge.

Exposures Noninvasive cardiac testing performed within 3 days of an ED evaluation for suspected acute coronary syndrome.

Main Outcomes and Measures The primary outcome was composite risk of death or acute MI, within 30 days of an ED discharge.

Results A total of 79 040 patients were evaluated in this study, of whom 57.7% were female. The mean (SD) age of the cohort was 57 (16) years, and 16 164 patients (21%) had completed early NIT. The absolute risk of death or MI within 30 days was low (<1%). Early NIT had the minor benefit of reducing the absolute composite risk of death or MI (0.4% [95% CI, −0.6% to −0.3%]), and, separately, of death (0.2% [95% CI, −0.2% to −0.1%]), MI (−0.3% [95% CI, −0.5% to −0.1%]), and major adverse cardiac event (−0.5% [95% CI, −0.7% to −0.3%]). The number needed to treat was 250 to avoid 1 death or MI, 500 to avoid 1 death, 333 to avoid 1 MI, and 200 to avoid 1 major adverse cardiovascular event within 30 days. Subgroup analysis revealed a number needed to treat of 14 to avoid 1 death or MI in the subset of patients with elevated troponin.

Conclusions and Relevance Early NIT was associated with a small decrease in the risk of death or MI in patients admitted to the ED with suspected acute coronary syndrome, but this clinical strategy may not be optimal for most patients given the large number needed to treat.