What physical exam finding is typical for hypertrophic cardiomyopathy?

Hypertrophic cardiomyopathy (HCM) is characterized by a thickening of the heart muscle, particularly affecting the interventricular septum. This structural change can lead to dynamic outflow tract obstruction, which is a hallmark of the condition. The typical physical examination finding associated with HCM is a harsh systolic crescendo-decrescendo murmur, best heard at the left sternal border.

This murmur occurs due to turbulent blood flow as it moves through the narrowed left ventricular outflow tract, especially during systole when the heart contracts. The intensity of this murmur can change with the position of the patient; for instance, when the patient stands up or performs a Valsalva maneuver, the murmur may increase in intensity due to decreased venous return and decreased left ventricular volume, accentuating the outflow tract obstruction.

Understanding this murmur's characteristics helps differentiate HCM from other heart conditions, as well as assists in guiding further diagnostic workup and management strategies.