Effect of intravenous amiodarone on myocardial repolarization and refractoriness: a new method of assessment.
Amiodarone is a benzofuran derivative with depressant effects on all electrically active cardiac tissues and important antiarrhythmic properties after long-term dosing. We evaluated its short-term effects on myocardial repolarization and refractoriness in eight patients. The duration of repolarization was evaluated by a new method, the paced evoked-response system, which records the dominantly local repolarization that follows a controlled (paced) depolarization from the same site. Intravenous amiodarone (5 mg/kg) prolonged the latency of the stimulus peak-evoked T wave interval an average of 39.4 msec (+15% of control) 10 min after infusion. In animal experiments these changes correlated well with simultaneous increases in the paced monophasic action potentials obtained with suction electrode catheters. There was also a lengthening of the effective refractory period of the atrioventricular node from 270 +/- 20 to 295 +/- 25 msec. Atrial and ventricular refractoriness were not altered. Amiodarone early activity at the atrial and ventricular level apparently differs from that long-term therapy and appears to favor changes in action potential duration and not changes in refractoriness.
D000200:Action Potentials / Q000187:drug effects; D000638:Amiodarone / Q000494:pharmacology*; D000818:Animals; D001572:Benzofurans / Q000494:pharmacology*; D004285:Dogs; D004562:Electrocardiography; D005071:Evoked Potentials / Q000187:drug effects; D005260:Female; D006321:Heart / Q000187:drug effects*; D006801:Humans; D008297:Male; D008875:Middle Aged
D001572:Benzofurans; D000638:Amiodarone