Hypertrophic Cardiomyopathy: The Daily PANCE Blueprint

The answer is B. Hypertrophic cardiomyopathy

Exertional syncope in a young athlete plus a systolic murmur that gets LOUDER with standing and Valsalva is hypertrophic cardiomyopathy — an autosomal dominant sarcomere disorder producing asymmetric septal hypertrophy that obstructs left ventricular outflow. The murmur behaves the way it does because the obstruction is dynamic: anything that shrinks the left ventricular cavity (standing, Valsalva, dehydration) brings the hypertrophied septum and the anterior mitral leaflet closer together and worsens the obstruction, so the murmur intensifies. Anything that fills the ventricle (squatting, handgrip, leg raise) opens the outflow tract and quiets the murmur. That maneuver response is the whole question. Aortic stenosis is the classic trap — it also gives a crescendo-decrescendo systolic murmur, but it radiates to the carotids, produces a delayed, weak pulse (pulsus parvus et tardus), and gets softer with Valsalva because less blood is crossing the fixed valve. Mitral valve prolapse does move with these maneuvers but produces a midsystolic click with a late murmur, and a ventricular septal defect gives a harsh holosystolic murmur that also softens with Valsalva. Confirm with echocardiography, and remember that HCM is the leading cause of sudden cardiac death in young athletes — restrict competitive sport, screen first-degree relatives, and avoid preload-reducing agents such as diuretics, nitrates, and vasodilators.