Characteristic feature of hyperophic obstructive cardiomyopathy is:-

Hyperophic cardiomyopathy (HCM) is a common (incidence, 1 in 500), clinically heterogeneous, genetic disorder characterized by myocardial hyperophy, poorly compliant left ventricular myocardium leading to abnormal diastolic filling, and (in about one third of cases) intermittent ventricular outflow obstruction. The essential feature of HCM is massive myocardial hyperophy,usually without ventricular dilation. The classic pattern involves dispropoionate thickening of the ventricularseptum relative to the left ventricle free wall (with a ratio of septum to free wall greater than 3 : 1), termed asymmetric septal hyperophy. In about 10% of cases, the hyperophy is concentric and symmetrical. On longitudinal sectioning, the normally round-to-ovoid left ventricular cavity may be compressed into a "banana-like" configuration by bulging of the ventricular septum into the lumen. Although marked hyperophy can involve the entire septum, it is usually most prominent in the subaoic region. The left ventricular outflow tract often exhibits a fibrous endocardial plaque associated with thickening of the anterior mitral leaflet. The most impoant histologic features of HCM myocardium are: (1) massive myocyte hyperophy (2) haphazard disarray of bundles of myocytes, individual myocytes, and contractile elements in sarcomeres within cells (termed myofiber disarray). (3) interstitial and replacement fibrosis Mutations causing HCM are found most commonly in the gene encoding b-myosin heavy chain (b-MHC), followed by the genes coding for cardiac TnT, a-tropomyosin, and myosin-binding protein C (MYBP-C).