A 32-year-old with exertional dyspnea has a crescendo-decrescendo systolic murmur that increases with Valsalva; what is the most likely diagnosis?

• A. Aortic regurgitation
• B. Aortic stenosis
• C. Hypertrophic cardiomyopathy
• D. Patent ductus arteriosus

Answer: (C)

A crescendo-decrescendo systolic murmur that worsens with Valsalva in a young adult with exertional dyspnea points to hypertrophic cardiomyopathy with dynamic left ventricular outflow tract obstruction. In HCM, thickened septum narrows the LV outflow tract, and the obstruction becomes more pronounced when preload falls (as with Valsalva or standing), making the murmur louder even though the ventricle has less filling. Increasing preload, such as with squatting or leg lifting, tends to lessen the obstruction and soften the murmur. This pattern helps distinguish it from other causes: aortic regurgitation is a diastolic murmur; aortic stenosis is a systolic murmur typically seen in older patients and not characteristically amplified by Valsalva; patent ductus arteriosus causes a continuous murmur.