While there are a number of possible causes, three are particularly common in the UK. The first is Hypertrophic Cardiomyopathy (HCM), a genetic heart muscle condition in which the walls of the heart’s left ventricle become abnormally thickened. This can obstruct blood flow from the heart, causing loss of consciousness and a dangerous arrhythmia leading to cardiac arrest. The second is Long QT Syndrome, an often-unrecognised inherited condition affecting the heart’s electrical system that can predispose young people to life-threatening arrhythmias. Episodes are most commonly triggered by physical exertion or emotional stress. The third is commotio cordis, an electrical disturbance triggered by a sharp blow to the chest at a critical moment in the heart’s cycle. It can occur in contact sports such as football, cricket, rugby, and martial arts, as well as any situation involving a forceful blow to the chest.
