## **Core Concept**
Hypertrophic obstructive cardiomyopathy (HOCM) is characterized by a dynamic obstruction of the left ventricular outflow tract (LVOT), often due to asymmetric septal hypertrophy. This condition leads to a distinctive heart murmur.

## **Why the Correct Answer is Right**
The murmur in HOCM is typically a systolic ejection murmur that starts after the first heart sound and peaks late in systole. It is dynamic and can change with maneuvers that affect ventricular volume or contractility. The murmur is due to the obstruction of the LVOT.

## **Why Each Wrong Option is Incorrect**
- **Option A:** The murmur in HOCM increases with maneuvers that decrease left ventricular volume (e.g., standing, Valsalva maneuver) or increase contractility (e.g., dobutamine). This is correct regarding HOCM.
- **Option B:** The murmur decreases with maneuvers that increase left ventricular volume (e.g., squatting, leg raising) or decrease contractility (e.g., beta-blockers). This is also correct.
- **Option C:** The murmur is often best heard at the apex and radiates to the axilla. This statement might seem correct but can be misleading; the murmur is typically best heard at the lower left sternal border.
- **Option D:** The statement that the murmur does not change with auscultation in different positions or with maneuvers is incorrect regarding HOCM, as the murmur's intensity does change.

## **Clinical Pearl / High-Yield Fact**
A key clinical feature of HOCM is that the murmur's intensity can be decreased by interventions that increase venous return (and thus ventricular volume), such as squatting. Conversely, maneuvers that decrease venous return (e.g., standing) increase the murmur's intensity.

## **Correct Answer:** . murmur is often best heard at the apex and radiates to the axilla.