Which cardiomyopathy is characterized by thickened ventricular walls and small chamber size due to sarcomere protein gene mutations?

Which cardiomyopathy is characterized by thickened ventricular walls and small chamber size due to sarcomere protein gene mutations?

• A. Dilated cardiomyopathy
• B. Restrictive cardiomyopathy
• C. Arrhythmogenic right ventricular cardiomyopathy
• D. Hypertrophic cardiomyopathy

Answer: (D)

Thickened ventricular walls with a small chamber size due to mutations in genes encoding sarcomeric proteins is hypertrophic cardiomyopathy. The disease arises from defects in the heart’s contractile machinery, such as mutations in beta-motors, myosin-binding protein C, or troponin components, which cause abnormal sarcomere function. This leads to asymmetric septal hypertrophy, myofiber disarray on microscopic exam, and diastolic dysfunction as the stiffened ventricle fills poorly. The outflow tract can be dynamically obstructed during systole, contributing to symptoms like dyspnea or chest pain and increasing the risk of sudden cardiac death in some patients. This pattern distinguishes it from dilated cardiomyopathy, which features enlarged, poorly contracting chambers; restrictive cardiomyopathy, where filling is impaired due to a stiff ventricle without the primary thickening from sarcomeric mutations; and arrhythmogenic right ventricular cardiomyopathy, which primarily affects the right ventricle with fibrofatty replacement rather than concentric left ventricular thickening.

Thickened ventricular walls with a small chamber size due to mutations in genes encoding sarcomeric proteins is hypertrophic cardiomyopathy. The disease arises from defects in the heart’s contractile machinery, such as mutations in beta-motors, myosin-binding protein C, or troponin components, which cause abnormal sarcomere function. This leads to asymmetric septal hypertrophy, myofiber disarray on microscopic exam, and diastolic dysfunction as the stiffened ventricle fills poorly. The outflow tract can be dynamically obstructed during systole, contributing to symptoms like dyspnea or chest pain and increasing the risk of sudden cardiac death in some patients. This pattern distinguishes it from dilated cardiomyopathy, which features enlarged, poorly contracting chambers; restrictive cardiomyopathy, where filling is impaired due to a stiff ventricle without the primary thickening from sarcomeric mutations; and arrhythmogenic right ventricular cardiomyopathy, which primarily affects the right ventricle with fibrofatty replacement rather than concentric left ventricular thickening.