(P085) STANDARD VERSUS INTENSIVE MONITORING POST-MYOCARDIAL INFARCTION LOOKING FOR NEW-ONSET ATRIAL FIBRILLATION OR FLUTTER: FINDINGS FROM THE SIMPL-AF TRIAL

Background: Atrial fibrillation (AF) in association with acute coronary syndrome (ACS) often necessitates a change in therapeutics (e.g. anticoagulation) to avert long-term adverse outcomes.(e.g. stroke). However, paroxysmal AF can be asymptomatic and go undetected. We sought to evaluate whether a long-term ECG monitoring strategy is superior to conventional follow-up for AF detection in patients following ACS.

METHODS AND RESULTS: SIMPL-AF (NCT03345615) was a multi-center, prospective, open-label randomized clinical trial. Patients 19 years of age or older with no evidence of AF, who presented to hospital with a myocardial infarction (MI) were enrolled from two tertiary care centers. Patients were randomized in a 2:1 allocation to intensive monitoring with a 30-day external loop recorder or standard care before hospital discharge, and followed for 12-months after discharge. The primary outcome was newly detected AF or atrial flutter (AFL) ≥30 seconds within 30 days of enrolment. Secondary outcomes included actionable AF/AFL (defined as anticoagulation prescription or treatment), ventricular tachycardia (VT), pauses >3 seconds, oral anticoagulation prescription, and adverse events at 1-year. Data were analyzed by intention-to-treat. 195 participants were randomized to intensive monitoring (n=130) or standard care (n=65). Mean age was 63.5±11.3 years, 77% male, with a mean CHA2DS2-VASc score of 3.4±1.2. Patients were admitted with ST elevation MI (STEMI; 68%), non-STEMI (32%), and 96% underwent percutaneous intervention. After discharge, patients randomized to intensive monitoring wore the device for a median of 20 days. New-onset AF/AFL was detected in 10 patients (7.7%) randomized to intensive monitoring, and 0 patients randomized to standard care (Figure 1, log-rank p=0.023). The rate ratio of newly detected AF/AFL within 30 days using an extended monitoring device was 4.50 (95% confidence interval 1.1-30.6, p=0.039). In univariable analyses, current smoking history and left main coronary disease were predictors of newly detected AF/AFL with intensive monitoring. Of the 10 patients with newly diagnosed AF/AFL, 4 were deemed actionable (3 anticoagulation, 1 ablation). Ventricular arrhythmias were detected in 25 patients (19%), with significant pauses detected in 4 patients (3%). Over a median follow-up of 367 days (IQR 144-375 days), adverse events included emergency room visits (12%), recurrent AMI (2%), and death (2%). There were no significant differences in adverse events between groups.

Conclusion: Intensive monitoring was superior to conventional follow-up for detecting new-onset AF/AFL following presentation with ACS. Only 40% of AF/AFL episodes detected led to changes in anticoagulation prescription or other treatment. Although the yield is low, intensive monitoring can identify actionable AF following ACS.