Anomalous Attachment of the Posterior Mitral Annulus to the Crest of the Left Ventricle in Patients With Mitral Annular Disjunction (MAD) and Mitral Valve Prolapse.

The purpose of this study is to determine the site of attachment of the posterior mitral annulus to the left ventricle in patients with mitral annular disjunction (MAD) and mitral valve prolapse (MVP). The posterior annulus normally attaches to the inlet of the left ventricle. Some histological findings suggest that the disjunctive annulus may instead attach anomalously to the left ventricular (LV) crest in patients with MVP. We used cardiac magnetic resonance imaging to determine the site of attachment of the posterior mitral annulus (crest vs inlet) in 25 patients with MVP with MAD (MAD+ group) and 24 patients with MVP without MAD (MAD- group). The site of annular attachment was determined in the 3-chamber view during diastole. Our data demonstrate complete separation in mitral annular attachment site between MAD+ and MAD- groups. All patients in the MAD+ group demonstrated annular attachment to the LV crest, whereas all those in the MAD- group demonstrated annular attachment to the LV inlet (p <0.001). The presence of anomalous annular attachment in MAD+, but not MAD- patients, suggests this anatomic abnormality represents a feature of the MAD phenotype rather than the myxomatous phenotype. Anomalous annular attachment may potentially influence the arrhythmic potential of MAD.