Hypertrophic cardiomyopathy (HCM)
Short orientation
Hypertrophic cardiomyopathy is an inherited myocardial disease defined by unexplained left ventricular hypertrophy (usually wall thickness ≥ 15 mm in adults) in the absence of another cause (for example, long‑standing hypertension or valve disease).
It is commonly asymmetric (septal) and may produce dynamic left ventricular outflow tract obstruction (LVOTO) from systolic anterior motion (SAM) of the mitral valve.
HCM is an important cause of exertional syncope and sudden cardiac death (especially in young people and athletes); emergency clinicians must recognise acute complications, avoid therapies that worsen LVOTO and escalate promptly.
Epidemiology and genetics
- Prevalence ≈ 1:500; phenotypic expression and penetrance are variable.
- More than 50% of genotyped cases have an autosomal dominant sarcomeric mutation; many patients remain genotype‑negative.
- New diagnoses require specialist cardiology follow‑up and consideration of family screening.
Pathophysiology relevant to the ED
HCM reduces LV cavity size and impairs diastolic filling, leading to raised LV end‑diastolic pressure and breathlessness. Dynamic LVOTO occurs when a hypertrophied septum and flow forces pull the anterior mitral leaflet anteriorly during systole (SAM), producing a variable, load‑dependent gradient and often mitral regurgitation.
Hypertrophied myocardium has increased oxygen demand and microvascular dysfunction, predisposing to ischaemia and arrhythmia. Fibrosis creates an arrhythmogenic substrate for ventricular tachycardia/fibrillation and sudden cardiac death.