What is the structural heart change in hypertrophic obstructive cardiomyopathy?

• A. Asymmetric septal hypertrophy
• B. Concentric LVH
• C. Global dilation
• D. Primary valvular regurgitation

Answer: (A)

In hypertrophic obstructive cardiomyopathy, the defining structural change is asymmetric thickening of the interventricular septum, especially the basal anterior portion. This focal septal hypertrophy narrows the left ventricular outflow tract during systole and creates dynamic obstruction that can worsen with lower preload or higher contractility. This pattern distinguishes it from other causes of thickened ventricles, such as concentric LVH seen with long-standing hypertension or athletic remodeling, which involve uniform thickening rather than focal septal prominence. Global dilation points to dilated cardiomyopathy, and primary valvular regurgitation is a valve problem rather than a myocardial structural change.