In pediatric hypertrophic cardiomyopathy, which description best characterizes the condition?

• A. Ventricle walls are stiff.
• B. The heart rate is always normal in HCM.
• C. The condition only affects the left ventricle.
• D. Heart muscle is unusually thick.

Answer: (D)

Hypertrophic cardiomyopathy in children is defined by an unusual thickening of the heart muscle. The key feature is that the myocardium is abnormally thick, often unevenly distributed (asymmetric thickening), which reduces the chamber size and makes the ventricle stiff during diastole. This thickening can occur in the left ventricle and septum, and it can lead to diastolic dysfunction and sometimes outflow tract obstruction. While stiffness and diastolic issues arise from the thickened walls, the best way to describe the condition is simply that the heart muscle is unusually thick.

Heart rate in HCM is not defined as always normal; it can be normal or elevated and may change with symptoms or exertion. The disease most often involves the left ventricle, but it is not limited to it and can affect other regions as well, so saying it affects only the left ventricle isn’t accurate.