HEART RHYTHM DISORDERS AS A RESULT OF CHANGES IN IONIC CHANNELS

Abstract

The electrical activity of the heart under physiological conditions begins with the
excitation of the cells of the sinoatrial (SA) node. Slow diastolic depolarization of SA
node cells results in an action potential that propagates through the atria,
atrioventricular (AV) node, His–Purkinje system, and ventricular myocardium, causing
excitation. Thus, due to electromechanical coupling, sequential contraction of the atria
and ventricles occurs. The action potential of cardiomyocytes consists of 5 successive
phases: 1) the fast depolarization phase (phase 0) begins during the entry of Na + ions
into the cell through fast sodium channels; 2) early rapid repolarization phase (phase
1);