Sudden cardiac death due to an anomalous posterior papillary muscle.

Anomalies of the mitral subvalvular apparatus can include differing types of papillary muscles and chordae tendinae. Direct insertion of the anomalous papillary muscle or chordae tendinea into the anterior mitral leaflet and fusion to the ventricular septum are common findings related to these anomalies. Anomalous papillary muscles or chordae, especially those that insert directly into the mitral leaflets, play a role in obstructing left ventricular outflow by restricting the mobility of the leaflets and/or tethering them toward the septum, thus narrowing the left ventricular outflow tract (LVOT). The incidence of mitral valve anomalies associated with LVOT is probably underestimated. This topic is frequently studied, however, especially in the pediatric cardiac surgery milieu, because LVOT obstruction could have a surgical solution. We report a case of an 18-year-old woman affected by epilepsy since 5 months of age who was found dead in her bedroom. An uncommon anomalous papillary muscle/chordae was the main autopsy finding. This malformation causes direct continuity between an accessory papillary muscle and a mitral leaflet, resulting in a long rigid area that can cause dynamic late-systolic intraleft-ventricular obstruction. In our case, in the absence of any other pathologic findings or major structural abnormalities, we speculate that a malignant cardiac arrhythmia provoked by the accessory papillary muscle could be the cause of death.