70% of sudden cardiac deaths are caused by arrhythmias, often referred to as malignant arrhythmias, with the most common ones being ventricular tachycardia and ventricular fibrillation. A small portion is caused by severe bradycardia. This condition is generally seen in patients with structural heart diseases, such as acute myocardial infarction, severe dilated cardiomyopathy, hypertrophic cardiomyopathy, or patients in the late stages of valvular insufficiency or stenosis. It can also occur in patients with severe electrolyte disturbances, who are prone to malignant arrhythmias.