The molecular basis of cardiac arrhythmias in patients with cardiomyopathy.

Cardiac arrhythmias are a leading cause of mortality and morbidity in Western society. In some specific instances, these arrhythmias are caused by abnormalities of cardiac ion channels, such as sodium, calcium, and potassium channels, which carry ionic currents and are fundamental determinants of cardiac excitability. Abnormalities of these ion channels are attributed to mutations in the genes encoding the channel protein and cause altered function of channels, which can predispose to arrhythmias. During heart failure, many channels also malfunction because of altered expression, resulting in lethal arrhythmias.