Hypertrophic cardiomyopathy anatomic abnormalities

Editors-In-Chief: C. Michael Gibson, M.S., M.D. [mailto:mgibson@perfuse.org]

Overview
Individuals with HCM have some degree of left ventricular hypertrophy. In approximately 2/3rds of cases this is an asymmetric hypertrophy, involving the inter-ventricular septum, and is known as asymmetric septal hypertrophy (ASH). This is in contrast to the symmetric and concentric hypertrophy seen in aortic stenosis or hypertension.

Left Ventricle
The degree of ventricular hypertrophy is variable ranging from diffuse involvement of both ventricles to isolated involvement of a portion of one segment of the LV.

Data from two large registries indicates that;
 * 55% of cases involve the septum and anterolateral free wall,
 * 20% involve the entire septum alone,
 * 10% are limited to the basal septum and 15% are limited to the apical or distal LV (Yamaguchi variant).

Some genetic variants may manifest very little overt LVH but are still associated with an increased risk of sudden cardiac death (SCD).

Outflow Tract
The left ventricular outflow tract is often small.

Mitral Valve
The mitral valve maybe elongated and enlarged.