H ypertrophic obstructive cardiomyopathy (HOCM) affecting both the right and left ventricular (RV and LV) outflow tracts is rare, and the mechanism of obstruction is different in each ventricle. A 21-year-old man with a family history of HOCM and sudden death was referred with breathlessness (New York Heart Association grade II) and occasional presyncope. There had been no discharges of an implantable defibrillator inserted 2 years earlier, and the sole medication was a ␤-blocker. A

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... c echocardiogram revealed marked, bilateral ventricular hypertrophy. Doppler revealed a 70 mm Hg LV outflow gradient and obstruction of the right outflow tract at rest. Right and left heart catheterization, with simultaneous central aortic and LV pressure recording, revealed a 100 mm Hg subaortic gradient (Figure, a) and a 75 mm Hg subpulmonic gradient at rest (Figure, b and c). Ventriculography confirmed that the obstruction of the LV outflow was due to systolic anterior mitral valve movement (Figure, d and e), whereas RV outflow obstruction was due to massive hypertrophy of the crista supraventricularis (Figure, f).