Which finding on echocardiography indicates left ventricular outflow tract obstruction in hypertrophic cardiomyopathy?

Which finding on echocardiography indicates left ventricular outflow tract obstruction in hypertrophic cardiomyopathy?

• A. Mitral regurgitation without LVOT involvement.
• B. Fixed aortic stenosis due to calcification.
• C. Dynamic LVOT gradient with systolic anterior motion of the mitral valve.
• D. Pulmonary valve stenosis with right ventricular outflow obstruction.

Answer: (C)

In hypertrophic cardiomyopathy, the outflow obstruction is dynamic rather than fixed. The thickened septum narrows the left ventricular outflow tract, but the obstruction worsens when the mitral valve leaflet moves toward the septum during systole—this is systolic anterior motion (SAM) of the mitral valve. The combination of SAM and the dynamic obstruction creates a high-velocity, late-systolic Doppler jet across the LV outflow tract with a measurable gradient that can vary with preload and contractility. On echocardiography you’ll see the anterior mitral leaflet moving toward the septum in systole, often with accompanying mitral regurgitation from the abnormal leaflet motion, and a dynamic LVOT gradient that can increase with maneuvers like standing or Valsalva. This pattern specifically points to LVOT obstruction in hypertrophic cardiomyopathy. Fixed obstructions, such as a calcified aortic valve, produce a constant gradient and are not driven by SAM, while right-sided outflow issues or MR without LVOT involvement do not explain the LVOT obstruction.

In hypertrophic cardiomyopathy, the outflow obstruction is dynamic rather than fixed. The thickened septum narrows the left ventricular outflow tract, but the obstruction worsens when the mitral valve leaflet moves toward the septum during systole—this is systolic anterior motion (SAM) of the mitral valve. The combination of SAM and the dynamic obstruction creates a high-velocity, late-systolic Doppler jet across the LV outflow tract with a measurable gradient that can vary with preload and contractility. On echocardiography you’ll see the anterior mitral leaflet moving toward the septum in systole, often with accompanying mitral regurgitation from the abnormal leaflet motion, and a dynamic LVOT gradient that can increase with maneuvers like standing or Valsalva. This pattern specifically points to LVOT obstruction in hypertrophic cardiomyopathy. Fixed obstructions, such as a calcified aortic valve, produce a constant gradient and are not driven by SAM, while right-sided outflow issues or MR without LVOT involvement do not explain the LVOT obstruction.