GLOSSARY

Hypertrophic cardiomyopathy (HCM) is a genetic disease of the heart muscle characterised by abnormal thickening of the left ventricular wall (usually 15 millimetres or more) without an explanatory cause such as hypertension, and it is one of the most common causes of sudden cardiac death in young athletes.

Characteristics

• Prevalence: about 1 in 500 people; many are undiagnosed.
• Genetics: autosomal dominant; mutations in genes for sarcomere proteins (such as MYH7 and MYBPC3); each child of an affected person has a 50 percent chance of inheriting it.
• Asymmetric thickening: often of the interventricular septum.
• Myocyte disarray and fibrosis, which form the substrate for lethal arrhythmias.
• Left ventricular outflow tract (LVOT) obstruction: in about two-thirds of patients at rest or with exertion.

Symptoms

Many are asymptomatic; others have