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Anomalous Papillary Muscle Insertion as a Cause of Mitral Regurgitation: Multimodality Imaging-Based Diagnosis.

December 2020 1 Digvijay Nalawade, DM Nikhil Borikar, DM Parag Bawaskar , DM Ajay Chaurasia, DM Congenital mitral valve lesions are rare and estimated to affect 5 of 100 000 of the general population.1 Various classification systems are used to group anomalies affecting the mitral valve apparatus.1 However, some lesions have an atypical appearance, which prevents them from being grouped into any particular classification. We herein report a case of mitral regurgitation (MR) due to anomalous papillary muscle insertion into posterior mitral leaflet (PML) with absent chordae. A 55-year-old healthy male with no cardiovascular risk factors presented to our institute with several-month history of gradually progressive dyspnoea on exertion. On physical examination, significant findings were soft S1, normal S2, and a pansystolic murmur at the apex. His ECG was unremarkable. Transthoracic echocardiogram showed a dilated left atrium with severe eccentric MR and normal left ventricular ejection fraction. The motion of PML was restricted (Carpentier type 31; Figure [A]), and the MR jet was directed toward the PML (Figure [B]; Movie I in the Data Supplement), which raised suspicion of rheumatic heart disease. However, the anterior mitral leaflet was normal in thickness and motion with normal chordal attachments, which prompted us to consider other diagnoses. On further evaluation, we found that the anterolateral papillary muscle was elongated and directly inserted into the PML (Figure [C]). The mitral valve opening was normal, unlike a parachute mitral valve, which has an association with similar papillary muscle abnormality but with an eccentric opening (Figure [D]).2 We performed transesophaegal echocardiography for a detailed evaluation of the mitral valve apparatus. There was no commissural fusion, calcification, or subvalvular involvement, thus excluding the diagnosis of rheumatic heart disease (Movie II in the Data Supplement). Transesophaegal echocardiography images revealed that the P1/ P2 segments of PML were directly attached to the papillary muscle without any intervening chordae (Figure [E] and [F]; Movies III and IV in the Data Supplement). Cardiac magnetic resonanace images confirmed that one head of the anterolateral papillary muscle had direct insertion into the ventricular surface of PML without any intervening chordae and was partly tethered to the lateral LV wall, resulting in restricted motion of the PML (Figure [G] and [H]; Movie V in the Data Supplement). The patient underwent successful mitral valve replacement with preservation of chordeopapillary support and remained asymptomatic at 6-month follow-up. Congenital mitral valve anomalies are complex and involve multiple parts of the mitral valve apparatus. Detailed segmental and multimodality imaging is useful to characterize these anomalies and to help plan surgical repair. Embryologically, an incomplete process of delamination of the trabecular ridge from the ventricular wall leads to morphological variations of the papillary muscles.3 Anomalous insertion of the papillary muscle directly into the anterior mitral leaflet resulting in left ventricular outflow tract obstruction is known in patients with hypertrophic cardiomyopathy.3 However, our case represents a unique congenital anomaly, with 2 well-developed © 2020 American Heart Association, Inc. CARDIOVASCULAR IMAGES