The murmur of hyperopic obstructive cardiomyopathy is decreased in which of the following
**Core Concept**
The underlying principle being tested is the pathophysiology of **hypertrophic obstructive cardiomyopathy (HOCM)**, specifically how the murmur associated with this condition changes under different conditions. HOCM is characterized by asymmetric septal hypertrophy, which can cause left ventricular outflow tract obstruction.
**Why the Correct Answer is Right**
The murmur of HOCM is typically a harsh, systolic ejection murmur best heard at the lower left sternal border. It is caused by turbulent flow across the narrowed left ventricular outflow tract. The murmur decreases with maneuvers that increase left ventricular volume, such as squatting, which reduces the outflow tract obstruction by increasing the size of the left ventricle.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because the murmur of HOCM typically increases with maneuvers that decrease left ventricular volume, such as standing or the Valsalva maneuver, not decreases.
**Option B:** Incorrect as isometric exercise, such as squatting, decreases the murmur by increasing left ventricular volume.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that the murmur of HOCM is dynamic and changes with maneuvers that alter left ventricular volume or contractility. Squatting increases venous return, which in turn increases left ventricular volume and reduces the dynamic outflow obstruction, thereby decreasing the murmur's intensity.
**Correct Answer:** D. Squatting.