Circulation. 2021 Mar 23. doi: 10.1161/CIRCULATIONAHA.120.052380. Online ahead of print.
Background: High-sensitivity cardiac troponin assays enable myocardial infarction to be ruled out earlier, but the safety and efficacy of this approach is uncertain. We investigated whether an early-rule out pathway is safe and effective for patients with suspected acute coronary syndrome. Methods: We performed a stepped-wedge cluster randomized controlled trial in the Emergency Departments of seven acute care hospitals in Scotland. Consecutive patients presenting with suspected acute coronary syndrome between December 2014 and December 2016 were included. Sites were randomized to implement an early rule-out pathway where myocardial infarction was excluded if high-sensitivity cardiac troponin I concentrations were <5 ng/L at presentation. During a prior validation phase, myocardial infarction was ruled out where troponin concentrations were <99th centile at 6-12 hours after symptom onset. The co-primary outcome was length of stay (efficacy), and myocardial infarction or cardiac death after discharge at 30 days (safety). Patients were followed for 1 year to evaluate safety and other secondary outcomes. Results: We enrolled 31,492 patients (59±17 years, 45% women) with troponin concentrations <99th centile at presentation. Length of stay was reduced from 10.1±4.1 to 6.8±3.9 hours (adjusted geometric mean ratio 0.78, 95% confidence interval [CI] 0.73 to 0.83, P<0.001) following implementation, and the proportion of patients discharged increased from 50% to 71% (adjusted odds ratio [aOR] 1.59, 95% CI 1.45 to 1.75). Non-inferiority was not demonstrated for the 30-day safety outcome (upper limit of one-sided 95% CI for adjusted risk difference 0.70%, non-inferiority margin 0.50%, P=0.068), but the observed differences favoured the early rule-out pathway (0.4% [57/14,700] versus 0.3% [56/16,792]). At 1 year, the safety outcome occurred in 2.7% (396/14,700) and 1.8% (307/16,792) of patients before and after implementation (aOR 1.02, 95% CI 0.74 to 1.40, P=0.894), and there were no differences in hospital reattendance or all-cause mortality. Conclusions: Implementation of an early rule-out pathway for myocardial infarction reduced length of stay and hospital admission. Whilst non-inferiority for the safety outcome was not demonstrated at 30 days, there was no increase in cardiac events at 1 year. Adoption of this pathway would have major benefits for patients and healthcare providers. Clinical Trial Registration: URL: https://www.clinicaltrials.gov Unique Identifier: NCT03005158.