Most cardiac deaths are due to ventricular fibrillation, an abnormal heart rhythm that interferes with the heart muscle's ability to effectively generate a blood pressure. Ventricular fibrillation can cause death if not immediately treated. Almost all victims of sudden cardiac death have some form of structural heart disease. Studies of younger athletes who died during exercise have shown some form of congenital heart disease, usually either a disease of heart muscle called hypertrophic cardiomyopathy or a defect in blood vessels supplying the heart.
Hypertrophic cardiomyopathy is characterized by an abnormally thick heart muscle.
Since it is often genetically transmitted, the disorder is often found in multiple family members. Unfortunately, these young people may present with sudden cardiac death as their first symptom. Coronary blood vessel anomalies result from an abnormally located artery. This malformation can interfere with blood flow to the heart muscle. In contrast to younger victims, sudden cardiac death in those over age 35 is most often caused by blockage of cardiac blood vessels by fatty deposits, or coronary atherosclerosis.