Situation: A 45-year-old man with hypertrophic cardiomyopathy (HCM) is admitted to the coronary care unit after fainting at home. Echocardiography shows a thickened septum with left ventricular outflow tract obstruction. He has vomited repeatedly for 2 days. His daughter asks who is most often affected by sudden cardiac death from HCM. Which group should the nurse name?

HCM is a leading cause of sudden cardiac death in young people and athletes. Calcific aortic stenosis affects older adults, peripartum cardiomyopathy occurs around delivery, and heavy alcohol use causes dilated cardiomyopathy.

Clinical context
This patient has hypertrophic cardiomyopathy (HCM) with left ventricular outflow tract obstruction, which is a high-risk substrate for fatal ventricular arrhythmias. The daughter’s question targets the population in which HCM most often causes sudden cardiac death (SCD).

Why the answer is young people, including competitive athletes
HCM is characterized by abnormal thickening of the left ventricular myocardium, most often due to mutations in sarcomere genes, and this hypertrophy is not explained by pressure overload or coronary disease ^[3]. The thickened, disorganized myocardium creates electrical instability, and when outflow tract obstruction is present, hemodynamic stress during exertion further increases the risk of fatal ventricular arrhythmia ^[3]. HCM is consistently identified as the most common structural cause of sudden cardiac death in individuals younger than 35 years, particularly competitive athletes. ^[1][2][3]

A meta-analysis of autopsy-based studies in young individuals aged ≤35 years found that HCM is a leading structural abnormality associated with SCD, although the proportion varies depending on the population studied ^[2]. In athletes, the diagnostic challenge is that intense training can produce physiological left ventricular hypertrophy that mimics HCM, so careful differentiation is required before attributing risk ^[1]. Despite that diagnostic complexity, the epidemiologic link between HCM and SCD in young athletes remains strong ^[1][3][4].

Why the other options are incorrect

Option	Condition	Typical population	Key distinction from HCM
1. Adults with long-term heavy alcohol intake	Dilated cardiomyopathy	Middle-aged and older adults	Chronic alcohol toxicity causes ventricular dilation and systolic dysfunction, not asymmetric septal hypertrophy with outflow obstruction.
3. Older adults with calcified aortic valves	Calcific aortic stenosis	Older adults	Calcification of the aortic valve produces pressure overload and concentric hypertrophy, but the primary pathology is valvular, and SCD risk is more gradual.
4. Women in late pregnancy or soon after delivery	Peripartum cardiomyopathy	Late pregnancy to postpartum period	This is a dilated, systolic heart failure syndrome unique to the peripartum window, not a genetic hypertrophic condition.

Key point! HCM causes SCD through ventricular arrhythmia triggered by myocardial disarray, fibrosis, and outflow tract obstruction during exertion. The highest-risk demographic is young people and competitive athletes, not older adults or peripartum women.

Watch out! Do not confuse physiological athlete’s heart with HCM. Both can show left ventricular hypertrophy on echocardiography, but HCM typically shows asymmetric septal hypertrophy, a non-dilated left ventricle, and evidence of outflow tract obstruction, whereas physiological hypertrophy is symmetric and regresses with detraining ^[1].