Hypertrophic cardiomyopathy--pathology and pathogenesis

Area of Science:

• Cardiovascular Genetics
• Molecular Cardiology
• Pathology

Background:

• Familial hypertrophic cardiomyopathy (HCM) is an inherited cardiac disease characterized by ventricular muscle thickening.
• Genetic mutations in sarcomeric proteins are implicated, affecting myofibril formation and myocyte arrangement.
• The genetic basis involves genes on chromosomes 1, 14, and 15, encoding beta heavy chain myosin, troponin T, and alpha tropomyosin.

Purpose of the Study:

• To investigate the phenotypic variability of familial hypertrophic cardiomyopathy.
• To analyze the spectrum of heart weight increase and ventricular involvement in affected individuals.
• To explore associated pathological findings such as fibrosis and endocardial thickening.

Main Methods:

• Analysis of 75 hearts from patients with familial hypertrophic cardiomyopathy.
• Assessment of total heart weight and patterns of ventricular wall thickening (diffuse, symmetric, asymmetric).
• Histopathological examination for myocyte disarray, fibrosis, and arterial changes.

Main Results:

• Heart weight ranged from near normal to over 800g, with variable ventricular involvement.
• Diffuse and symmetric hypertrophy occurred in 42%, while asymmetric forms commonly affected the anteroseptal region (31%).
• Fibrosis, dysplastic arterial changes, and subaortic endocardial thickening were observed in a significant proportion of cases.

Conclusions:

• Familial hypertrophic cardiomyopathy exhibits significant phenotypic heterogeneity, even within families with the same genetic abnormality.
• Understanding the varied presentation is crucial for diagnosis and management.
• Associated pathologies like fibrosis and endocardial thickening can mimic other cardiac conditions.