title: Electrophysiologic changes induced by external transthoracic countershock.
abstract: The purpose of this study was to characterize the electrophysiological effects of suprathreshold transthoracic shocks. Dogs were anesthetized and two consecutive shocks (10 joules/gk) were applied one minute apart. Ventricular extrasystoles were observed in six of the 11 dogs tested, A-V block in three, ventricular tachycardia in three, and asystole in one. Forty eight hours later the hearts were removed. Conventional electrophysiological techniques revealed the following: 1) injured cells had loss of resting potential, triangularization of the action potential and depressed upstrokes; 2) the functional refractory period was shortened, with an increase in time dependence; 3) action potential alternans; 4) discrete areas of marked depression of conduction; 5) re-excitation with premature stimulation and 6) histological evidence of sub-epicardial injury. These studies suggest that the application of suprathreshold shocks may induce electrophysiological changes potentially inducing tachyarrhythmias.
mesh_terms: D000818:Animals; D001145:Arrhythmias, Cardiac / Q000503:physiopathology*; D005117:Cardiac Complexes, Premature / Q000503:physiopathology; D004285:Dogs; D004554:Electric Countershock; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology; D006352:Heart Ventricles / Q000503:physiopathology; D008297:Male; D013610:Tachycardia / Q000503:physiopathology