Basic Science for the Clinical Electrophysiologist Cardiac Ion Channels

The analysis of the molecular basis of the inherited cardiacarrhythmias has been the driving force behind the iden-tification of the ion channels that generate the action poten-tial. The genes encoding all the major ion channels have cloned and sequenced. The studies have revealed greater complexity than heretofore imagined. Many ion channels function as part of macromolecular complexes in which many components are assembled at specific sites within the mem-brane. This review describes the generation of the normal cardiac action potential. The properties of the major ionic currents are the examined in detail. Special emphasis is placed on the functional consequences of arrhythmia-associated ion channel mutations. The review concludes with a glimpse of the directions in which this new electrophysiol-ogy may lead. The Cardiac Action Potentia