Mitral Annular Disjunction: Pathophysiology, Pro-Arrhythmic Profile and Repair Pearls

Abstract

Mitral annular disjunction (MAD) is a structural abnormality defined by a distinct separation of the mitral valve annulus—left atrial wall continuum and the basal aspect of the posterolateral left ventricle. This anomaly is often observed in patients with myxomatous mitral valve prolapse. Importantly, MAD has been strongly associated with serious ventricular arrhythmias and predisposes to sudden cardiac death. Therefore, we have to emphasize the need to diagnose this morphologic and functional abnormality in routine practice in order to facilitate optimal mitral valve repair and minimize patient risks. Nevertheless, clinical knowledge regarding MAD still remains limited. In the present review, we aim to shed light on several aspects of MAD, including distinct anatomical and pathophysiological characteristics, imaging modalities, association with ventricular arrhythmias, and current methods of treatment.

Mitral annular disjunction identified peripartum: A case highlighting key features of a recently classified syndrome

“…The Padua hypothesis theorises that the increased pulling of the posteromedial papillary muscle in mid‐systole by the mitral leaflets draws the adjoining postero‐basal left ventricular wall harshly to the apex 12 . This exaggerated force eventually leads to tissue damage and the formation of scar tissue, 12 which is evident with MAD in post mortem studies, 1,13 via other imaging modalities 2,3,6 and also histologically 1,3 . The interface between scar tissue and unaffected tissue, along with the repetitive mechanical stretch, is the hypothesised origin of the ventricular arrhythmias in MAD 13 …”

“…This exaggerated force eventually leads to tissue damage and the formation of scar tissue, 12 which is evident with MAD in post mortem studies, 1,13 via other imaging modalities 2,3,6 and also histologically 1,3 . The interface between scar tissue and unaffected tissue, along with the repetitive mechanical stretch, is the hypothesised origin of the ventricular arrhythmias in MAD 13 When using TTE to identify MAD, the four main parameters to be considered are: MV annulus to LV disjunction diameter (PLAX). Pickelhaube's sign. A paradoxical increase in mitral annular diameter during systole. Mitral regurgitation (MR) identification of MR jet direction and quantitation of MR severity. …”

“…By this criterion, the patient in this case study would be graded as type III, as the MAD was measured as 8.5 mm. Importantly, Karangelis et al 13 found that a disjunction of ≥8.5 mm strongly predisposes patients to ventricular tachycardia.…”

“…Quantifying the paradoxical systolic diameter increase is another TTE measurement for MAD (shown in Figure 5). MAD causes the PM annulus to move with the left atrium during the cardiac cycle instead of the standard movement with the left ventricle 8,13 . This produces a greater annular diameter in end‐systole, in contrast to normal where the end‐diastolic diameter is greater 6,13 …”

“…1,3 The interface between scar tissue and unaffected tissue, along with the repetitive mechanical stretch, is the hypothesised origin of the ventricular arrhythmias in MAD. 13 Key Imaging Features of MAD When using TTE to identify MAD, the four main parameters to be considered are:…”