Anomalous papillary muscle insertion into mitral valve leaflet: Autopsy study and implications

Area of Science:

• Cardiovascular Pathology
• Cardiac Anatomy
• Forensic Pathology

Background:

• Anomalous papillary muscle (APM) insertion into the anterior mitral valve leaflet is a rare cardiac finding.
• While often associated with hypertrophic cardiomyopathy (HCM), APM can occur independently and its hemodynamic significance is not always clear.
• Interpreting APM at autopsy is challenging due to the dynamic nature of left ventricular outflow tract (LVOT) obstruction.

Purpose of the Study:

• To analyze autopsy cases of APM to understand its prevalence, types, and association with cardiac morphology and cause of death.
• To investigate the characteristics of APM, including insertion site, origin, number of bellies, and associated heart measurements.
• To provide guidance on assessing the significance of APM during post-mortem examinations.

Main Methods:

• Retrospective analysis of autopsy cases, including systematic examination of hearts.
• Identification and classification of APM based on insertion site and type.
• Correlation of APM findings with heart weight, left ventricle (LV) thickness, LV endocardial fibrosis, age, sex, and cause/manner of death.
• Histological examination in select cases.

Main Results:

• APM prevalence was found to be 0.9% in systematically examined hearts.
• Type II APM was most frequent (n=8), followed by Type III (n=7) and Type I (n=5).
• Subjects who died of natural causes with APM were older and had heavier hearts compared to those with non-natural deaths, but LV thickness did not differ significantly.

Conclusions:

• APM is a rare cardiac anomaly that can be easily missed during autopsy.
• The mere presence of APM does not necessarily imply significant pathology or hemodynamic compromise.
• Proper assessment considering various morphological and clinical factors is crucial for determining the significance of APM at autopsy.