Characteristics and clinical implication of mitral annular disjunction in apparently normal hearts: a cardiac magnetic resonance study.

Background: While mitral annular disjunction (MAD) is associated with mitral valve prolapse (MVP) and ventricular arrhythmia (VA), its prevalence and clinical implication in subjects with normal heart remain unclear. Therefore, this study aimed to assess the incidence and characteristics of MAD in apparently normal hearts (ANH) confirmed by comprehensive cardiac magnetic resonance (CMR), and to explore its impact on myocardial contraction and potential association with VA.

Methods: This retrospective cohort study was conducted on 444 patients who underwent CMR at a tertiary care center between January 2017 and March 2023. The study included both outpatient and inpatient individuals, who were consecutively enrolled. These patients were divided into two cohorts: a primary cohort consisting of 374 ANH individuals, and a control cohort of 70 isolated MVP patients. MAD was assessed by two radiologists on CMR. Demographic characteristics and medical history were collected from an electronic medical record database. The endpoints were composite events, defined as sudden cardiac deaths (SCD), aborted SCD, ablation therapy for VA, and implantation of an implantable cardioverter-defibrillator (ICD). Cardiac function parameters were analyzed using cvi42 software. The key statistical analysis was performed using the univariate and multivariate logistic regression. A P value <0.05 was considered statistically significant.

Results: The final analysis included 374 ANH individuals [185 female (49.5%)] with an average age of 35.5±16.1 years (range, 9-76 years). The prevalence of MAD in the ANH group was 43.9%, commonly located at the anterior (7.4%), antero-lateral (6.5%) and inferior wall (41.7%), and was infrequent at the inferolateral wall (2.7%). There were no statistically significant differences in the history of syncope and hypertension between ANH individuals with and without MAD (P=0.83 and P=0.45, respectively). There were 131 patients (35.0%) experienced VA in the 374 ANH individuals. Multivariable logistic regression analysis showed that VA and female sex were independently associated with MAD (P=0.001 and P=0.03, respectively), while cardiac strain parameters were not (all P>0.05). The ANH patients with VA, when compared to those without VA, showed a higher frequency of inferolateral MAD (5.2% vs. 1.3%, P=0.04) and a longer MAD (3.1±1.1 vs. 2.2±1.5 mm, P=0.006), respectively, and these two factors were independently associated with the higher risk for VA.

Conclusions: MAD is a common finding in normal adult hearts when assessed by CMR. Although MAD at the inferolateral wall is rare, it is found to be associated with VA. Based on our findings, further investigation may be warranted for patients with MAD at the inferolateral wall, particularly when arrhythmic symptoms are present.