A 15-year-old male with a history of familial hypertrophic cardiomyopathy (HCM) presented to discuss participation in exercise and competitive sports. He was diagnosed with HCM at age 2 and subsequent echocardiograms showed marked septal hypertrophy and a resting left ventricular outflow tract (LVOT) gradient of 36 mm Hg. He was started on beta-blockade therapy and has remained on monotherapy since. At age 9 years, cardiac magnetic resonance imaging showed a septal wall thickness of 32 mm with late gadolinium enhancement. His resting LVOT gradients have been stable over the years in the moderate range, and he has remained asymptomatic. An implantable cardioverter-defibrillator (ICD) was inserted due to his hypertrophy burden and a family history of sudden cardiac death.
The patient participated in gym class but not in competitive sports in middle school. In high school, he joined the golf team but has not participated in gym class because of uncertainty around the intensity of exercise that would be considered "safe." He engages in low to moderate-intensity recreational activity, including weightlifting, jogging, skiing, and pick-up basketball games. He does not have any physical limitations or symptoms with exercise. He has no other medical history. His examination was notable for a 3/6 grade systolic ejection murmur that increases with squat-to-stand.
The patient's paternal uncle died suddenly in his 50's while jogging. The patient's father has a primary prevention ICD, but it has never fired. The patient's 2 siblings each have primary prevention subcutaneous ICDs. Genetic testing identified a pathogenic variant in the MYH7 gene that was also present in his father and 2 siblings.
Electrocardiogram showed left ventricular hypertrophy with repolarization abnormalities (Figure 1). Transthoracic echocardiography showed left atrial dilation, interventricular septum measuring 30 mm, systolic anterior motion of the mitral valve with peak gradient of 48 mm Hg at rest, and moderate to severe mitral regurgitation with an ejection fraction of 70% (Videos 1, 2, 3, and 4).