Background. Mitral annular disjunction (MAD) represents the detachment of the posterior mitral leaflet hinge-point from the ventricular myocardium. Recently, evidence has emerged linking MAD to severe ventricular arrhythmias. However, its prevalence and prognostic implications in patients with ST-segment elevation myocardial infarction (STEMI) are unknown.

Purpose. To investigate the prevalence of MAD by cardiac magnetic resonance imaging (CMR) and its association with serious arrhythmias in the setting of acute STEMI.

Methods. STEMI patients (n=621) enrolled in the MARINA-STEMI study (NCT04113356) underwent CMR 4 days (interquartile range (IQR) 2-5) after primary percutaneous coronary intervention. The presence of MAD, defined as disjunction ≥1mm and its longitudinal extent were obtained on long-axis cine-images; infarct characteristics were derived from late gadolinium enhancement. The primary clinical endpoint was defined as composite of ventricular fibrillation, sustained ventricular tachycardia (VT), aborted cardiac arrest and sudden cardiac death (SCD) (severe arrhythmic events (SArE)) occurring during index hospitalization (5 days, IQR 5-6).

Results. A total of 307 patients (49%) had MAD. Mean longitudinal MAD-distance was 4.6±1.7mm and the P3-segment was affected most frequently (n=263, 64% of MAD-patients). MAD-patients had a significantly smaller infarct size, lower prevalence of microvascular obstruction (MVO) and intramyocardial hemorrhage (IMH) as well as a higher ejection fraction (all p<0.03). During hospitalization, SArE occurred in 15 patients (9 with vs. 6 without MAD, p=0.407). In binary logistic regression, development of SArE was not dependent on MAD-extent (p=0.272). After dichotomization at different MAD-extents by deciles, SArE occurred significantly more often in patients with MAD-extent ≥5.5mm (9th decile, 6% vs. 2%, p=0.045).

Conclusion. MAD is a rather common finding in patients presenting with STEMI. Although presence of MAD was associated with less severe myocardial tissue damage, patients with MAD of greater extent were at increased risk of serious arrhythmias during index hospitalization. Further confirmation and longer follow-up are necessary to define the exact role of MAD in STEMI patients.