1323062 - Mitral Annulus Disjunction Arrhythmic Syndrome

A 60-year-old woman with history of mitral valve prolapse (MVP) presented with a month of palpitations.

Diagnostic Techniques and Their Most Important Findings:

Initial evaluation ruled out pulmonary thromboembolism, anemia, and thyroid disease. Electrocardiography showed premature ventricular complexes (PVCs). Holter monitoring showed 0.1% PVCs and a 46-beat run of ventricular tachycardia (VT) lasting 21 seconds at 128 bpm (Figure 1). Transthoracic echocardiography (TTE) showed normal left ventricular ejection fraction (LVEF), systolic curling motion of the posterolateral LV wall, MVP of the posterior leaflet, and mild mitral regurgitation (MR) (Figure 2). Cardiac magnetic resonance (CMR) with and without intravenous contrast showed normal LV size and function, MVP of the posterior leaflet, a 6 mm distance between the left atrial wall-mitral valve leaflet junction and the top of the LV wall in end-systole, and no late gadolinium enhancement (LGE) (Figure 3).

Learning Points from this Case: PVCs and VT had the same morphology, likely arising from the posteromedial papillary muscle. While TTE showed curling motion of the posterolateral LV wall and MVP, poor image quality limited further assessment. CMR showed separation of the left atrial wall-mitral valve leaflet junction from the top of the LV wall in systole, confirming the diagnosis of mitral annulus disjunction (MAD). Given normal EF, no LGE, and nonsevere arrhythmia, the patient received metoprolol.

MAD is defined as atrial displacement of the mitral valve hinge point from the LV myocardium and has been associated with MVP and sudden cardiac death (SCD). TTE findings include curling motion of the basolateral LV wall, MVP, and separation of the mitral annulus from the LV wall in end-systole. Using CMR to assess MAD in MVP increased the detection of MAD almost three-fold. Despite lack of reference standards on CMR, Dejgaard et al defined MAD in his study as a distance ≥1.0 mm measured from the left atrial wall-mitral valve leaflet junction to the top of the LV wall in end-systole in 3-chamber long axis. LGE was found in 38% of MAD, and 21% of patients had LGE in the posteromedial papillary muscle. Palpitations are the most reported symptom, and PVCs and nonsustained VT are detected in up to 87% and 22% of patients, respectively. Markers for severe arrhythmic events (aborted cardiac arrest and sustained VT) included lower EF, young age, and papillary muscle fibrosis. The hypothesis that arrhythmia is caused by papillary muscle fibrosis and stretch is supported by observations of PVCs arising from the papillary muscles and mitral annulus.

In conclusion, multimodality imaging with CMR increases the detection of MAD and may reveal a myocardial source of arrhythmias. Contrast-enhanced CMR can aid in identifying fibrosis of the papillary muscles or LV wall, allowing risk stratification and prevention of severe arrhythmic events and SCD. Early diagnosis and characterization with CMR can help guide management and improve patient outcomes.