Which condition characteristically presents with a systolic murmur that decreases in intensity with squatting?

• A. Hypertrophic obstructive cardiomyopathy
• B. Aortic stenosis
• C. Mitral valve prolapse
• D. Pulmonary embolism

Answer: (A)

Dynamic LV outflow tract obstruction in hypertrophic obstructive cardiomyopathy makes the systolic murmur highly sensitive to preload and afterload. Squatting increases venous return and systemic vascular resistance, raising LV volume and afterload. With a larger, less obstructed LV cavity, the contact between the anterior mitral leaflet and the septum during systole is reduced, the outflow gradient lessens, and the murmur becomes softer. This distinct pattern—murmur softening with squatting due to reduced obstruction—helps distinguish HOCM from other causes of systolic murmurs where changing preload/afterload doesn’t produce this same reliable attenuation.