Description and prevalence of ventricular mitral annular disjunction: variation of normality or pathological variant?

Introduction and objectives: The aim of this study was to investigate a new variation of the atrial wall-mitral annulus-ventricular wall junction along the mural mitral leaflet and commissures: the ventricular mitral annular disjunction (v-MAD). This new variant is characterized by spatial displacement of the mitral leaflet hinge line by more than 2 mm toward the left ventricle.Methods: We examined a cohort of autopsied human hearts (n = 224, 21.9% females, 47.9 ± 17.6 years) from patients without known cardiovascular disease to identify the presence of v-MAD.Results: More than half (57.1%) of the hearts showed no signs of MAD in the mural mitral leaflet or mitral commissures. However, v-MAD was found in 23.6% of cases, located within 20.1% of mural leaflets, 2.2% in superolateral commissures, and 1.3% in inferoseptal commissures. V-MAD was not uniformly distributed along the mitral annulus circumference, with the most frequent site being the P2 scallop (19.6% of hearts). The v-MAD height was significantly greater in mural leaflets than in commissures (4.4 mm ± 1.2 mm vs 2.1 mm ± 0.1 mm; P < .001). No specific variations in mitral valve morphology or anthropometrical features of donors were associated with the presence or distribution of v-MADs. Microscopic examinations revealed the overlap of the thin layer of atrial myocardium over ventricular myocardium in areas of v-MAD.Conclusions: Our study is the first to present a detailed definition and morphometric description of v-MAD. Further studies should focus on the clinical significance of v-MAD to elucidate whether it represents a benign anatomical variant or a significant clinical anomaly.