A rare variant of the mitral subvalvular apparatus: intermediate accessory papillary muscle with aberrant chordal attachment

Abstract

Variations of the mitral valve subvalvular apparatus are rare and may include accessory papillary muscles with diverse morphological features. Although the presence of accessory papillary muscles in the left ventricle has been previously described, their relationship with the tendinous cords and their leaflet attachment patterns have not been sufficiently characterized. A 62-year-old male underwent a forensic autopsy. Cardiac examination revealed an accessory papillary muscle located between the anterior and posterior papillary muscles in the left ventricle. This structure was independently attached to the ventricular wall by two distinct bases. A tendinous cord originating from this muscle was observed to extend to an atypical region of the anterior mitral leaflet, corresponding to the clear zone, which is not a usual site of chordal attachment. This case demonstrates a rare variation consisting of an accessory papillary muscle located between the two main papillary muscles, accompanied by a tendinous cord inserting outside the typical chordal attachment regions of the anterior mitral leaflet. Recognition of such variations may contribute to a better understanding of the morphological diversity of the mitral valve subvalvular apparatus and may be important in the planning of surgical and interventional procedures.

Keywords

• accessory papillary muscle
• intermediate papillary muscle
• mitral valve
• subvalvular apparatus

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