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Myocardial action potential and action of antiarrhythmic drugs

Author
Jonathan C Makielski, MD, FACC
Section Editor
Samuel Lévy, MD
Deputy Editor
Brian C Downey, MD, FACC

CARDIAC EXCITABILITY

Cardiac excitability refers to the ease with which cardiac cells undergo a series of events characterized by:

Sequential depolarization and repolarization

Communication with adjacent cells

Propagation of the electrical activity in a normal or abnormal manner

The heartbeat arises from organized flow of ionic currents through ion-specific channels in the cell membrane, through the myoplasm and gap junctions that connect cells, and through the extracellular space (figure 1) [1,2]. Abnormal excitability leading to arrhythmia can arise from acquired or inherited abnormalities of these elements. Acquired abnormalities in cardiomyopathy are called electrical remodeling. Inherited abnormalities arise from mutations in genes encoding the subunits and associated proteins of these channels and have been associated with familial arrhythmic syndromes and sudden cardiac death. Examples include the congenital long QT syndrome (sodium and potassium current), the Brugada syndrome (mainly sodium current), and congenital heart block (sodium current). (See "Genetics of congenital and acquired long QT syndrome" and "Brugada syndrome: Epidemiology and pathogenesis" and "Etiology of atrioventricular block", section on 'Familial disease'.)

           
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Literature review current through: Nov 2017. | This topic last updated: Jan 30, 2017.
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