Arrhythmia monitoring and outcome after myocardial infarction (BIO|GUARD-MI): a randomized trial.

Objectives: Cardiac arrhythmias predict poor outcome after myocardial infarction (MI). We studied if arrhythmia monitoring with an insertable cardiac monitor (ICM) can improve treatment and outcome.

Design: BIO|GUARD-MI was a randomized, international open-label study with blinded outcome assessment.

Setting: Tertiary care facilities monitored the arrhythmias, while the follow-up remained with primary care physicians.

Participants: Patients after ST-elevation (STEMI) or non-ST-elevation MI with an ejection fraction >35% and a CHADS-VASc score ≥4 (men) or ≥5 (women).

Interventions: Patients were randomly assigned to receive or not receive an ICM in addition to standard post-MI treatment. Device-detected arrhythmias triggered immediate guideline recommended therapy changes via remote monitoring.

Main Outcome Measures: MACE, defined as a composite of cardiovascular death or acute unscheduled hospitalization for cardiovascular causes.

Results: 790 patients (mean age 71 years, 72% male, 51% non-STEMI) of planned 1,400 pts were enrolled and followed for a median of 31.6 months. At 2 years, 39.4% of the device group and 6.7% of the control group had their therapy adapted for an arrhythmia [hazard ratio (HR) = 5.9,  < 0.0001]. Most frequent arrhythmias were atrial fibrillation, pauses and bradycardia. The use of an ICM did not improve outcome in the entire cohort (HR = 0.84, 95%-CI: 0.65-1.10;  = 0.21). In secondary analysis, a statistically significant interaction of the type of infarction suggests a benefit in the pre-specified non-STEMI subgroup. Risk factor analysis indicates that this may be connected to the higher incidence of MACE in patients with non-STEMI.

Conclusions: The burden of asymptomatic but actionable arrhythmias is large in post-infarction patients. However, arrhythmia monitoring with an ICM did not improve outcome in the entire cohort. Post-hoc analysis suggests that it may be beneficial in non-STEMI patients or other high-risk subgroups.

Clinical Trial Registration: [https://www.clinicaltrials.gov/ct2/show/NCT02341534], NCT02341534.