Functional and morphological predictors of left ventricular fibrosis in patients with mitral annular disjunction in cardiac magnetic resonance imaging

Mitral annular disjunction (MAD) is characterised by a separation of the mitral valve hinge point and the left ventricular (LV) myocardium and significantly increases the risk of ventricular arrhythmias and sudden cardiac death. Potential underlying mechanisms of arrhythmias include the combination of LV fibrosis serving as the arrhythmic substrate and mechanical stretch acting as a triggering factor.

To investigated functional and morphological predictors of left ventricular (LV) fibrosis in patients with MAD.

Cardiac magnetic resonance (CMR) reports and images of 111 patients with inferolateral MAD were reviewed; MAD distance, presence and size of mitral valve prolapse (MVP), midmyocardial replacement fibrosis of the basal inferolateral LV wall as well as the movement pattern of the basal inferolateral LV segment were analysed. Longitudinal and radial systolic displacement of the basal inferolateral LV segment was judged as homogeneous or accelerated by visual impression by two independent investigators. Differences between patients with and without LV fibrosis was calculated using Pearson's chi-squared test for categorical variables and ANOVA or Wilcoxon rank-sum as appropriate for continuous variables. Univariable and multivariable logistic regression models were used to identify patient characteristics independently associated with fibrosis of the basal inferolateral LV wall.

Median age was 52 years (interquartile range [IQR] 36-69) and 47% were female. Midmyocardial replacement fibrosis of the basal inferolateral LV wall was present in 27 (24%) patients. Patients with fibrosis were older (63.0 years [IQR 53.0-70.0] vs. 47.5 years [IQR 34.0-67.5], p=0.011), more likely to have MVP (24 [89%] vs. 58 [69%], p=0.041), had larger anterior (3.0 mm [IQR 0.0-4.0] vs. 0.0 mm [IQR 0.0-3.0], p=0.010), larger posterior prolapse size (4.0 mm [IQR 2.0-7.0] vs. 2.5 mm [IQR 0.0-4.5], p=0.016), larger median MAD distance (6.0mm [IQR 5.0-9.0] vs. 5.0mm [IQR3.0-8.0], p=0.018) and were more likely to exhibit an accelerated longitudinal motion of the basal inferolateral LV wall (20 [74%] vs. 26 [31%], p<0.001) (Table 1). Multivariable logistic regression revealed that age (odds ratio [OR] 1.06, confidence interval [CI] 1.03-1.10, p=0.001) and accelerated longitudinal motion of the basal inferolateral LV wall (OR 10.59, CI 2.84-39.49, p<0.001) were the only significant predictors of replacement fibrosis (Table 2). Finally, posterior MVP distance (OR 1.29, CI 1.02-1.62, p=0.032) and MAD size (OR 1.28, CI 1.05-1.56, p=0.017) were associated with an accelerated motion of the basal inferolateral LV segment.

Age and accelerated longitudinal motion of the basal inferolateral LV segment predict replacement fibrosis of the basal inferolateral wall in patients with MAD. MAD size and posterior MVP size are significantly associated with this accelerated movement pattern.