Mavacamten is a medication used to treat hypertrophic cardiomyopathy. Its metabolism is dependent on the hepatic CYP2C19 enzyme. CYP2C19-poor metabolisers (individuals who have two CYP2C19 loss-of-function alleles) have higher exposure to mavacamten, increasing the risk of side effects.

Long QT syndrome is characterised by QT prolongation on an electrocardiogram. It is associated with ventricular arrhythmias and sudden death, often triggered by adrenergic activation. 

Brugada syndrome is an inherited arrhythmia condition that may manifest as syncope or sudden death (often during sleep) secondary to ventricular fibrillation in patients with a structurally normal heart. 

Short QT syndrome is a rare inherited arrhythmia syndrome characterised by an abnormally short QT interval, which increases the risk of cardiac arrhythmias and sudden cardiac death. It is caused by pathogenic genetic variants that alter the function of ion channels responsible for currents that generate the cardiac action potential. 

Lymphoedema is an accumulation of subcutaneous fluid caused by dysfunction of the lymphatic drainage system, which most commonly presents as swelling (oedema). The term ‘primary lymphoedema’ refers to chronic swelling due to an intrinsic anomaly affecting the lymphatic system, which is often genetic in origin. It is distinct from secondary lymphoedema, in which lymphatic dysfunction occurs as a consequence of another underlying pathology (for example, malignancy, infection, trauma, surgery or radiotherapy).

Familial restrictive cardiomyopathy is characterised by left ventricular diastolic dysfunction (abnormal filling of the left ventricle in diastole) in the presence of normal left ventricular systolic function and normal or near-normal myocardial thickness. The right ventricle may also exhibit restrictive behaviour.

Hypertrophic cardiomyopathy is a heart muscle disease characterised by increased left ventricular wall thickness, with or without right ventricular hypertrophy, or mass that cannot be solely explained by abnormal loading conditions. It is associated with increased risks of sudden (arrhythmic) cardiac death, thrombo-embolic disease and progressive heart failure, and has an estimated prevalence of 1 in 500.

A thoracic aortic aneurysm is an atypical dilatation of a section of the aorta caused by an underlying weakness in the aortic wall. Causes of thoracic aortopathy can be acquired, inflammatory, congenital or inherited as part of a genetic predisposition. Most of the pathogenic variants that cause familial predisposition to thoracic aortic aneurysm and dissection are inherited in an autosomal dominant pattern.

Catecholaminergic polymorphic ventricular tachycardia is a rare inherited arrhythmia syndrome that can present with syncopal episodes during exercise or at times of intense emotion. It is an important diagnosis to make due to the associated high risk of cardiac arrest and sudden death.

Dilated cardiomyopathy is characterised by the systolic impairment and dilation of the left ventricle. It can be the result of a wide variety of aetiological mechanisms (acquired or inherited, or a combination of the two). When considered as a single group, dilated cardiomyopathy is a common cause of heart failure and the most common reason for heart transplantation.