Effect of amiodarone on conduction and refractoriness of the His-Purkinje system in the human heart.

Although the antiarrhythmic aspect of amiodarone has been extensively studied, its effects on His-Purkinje system conduction and refractoriness have not been systematically investigated in human beings. In 24 patients, anterograde His-Purkinje system conduction (HV intervals) and variables of His-Purkinje system refractoriness using the ventricular extrastimulus (V2) technique were analyzed before and after long-term therapy with amiodarone. The mean duration of amiodarone therapy at the time of repeat study was 16.2 +/- 7.7 weeks (range 11 to 42). The anterograde His-Purkinje system conduction time (HV interval) measured 49.6 +/- 9.5 ms (range 40 to 80) before and 60.6 +/- 10.7 ms (range 45 to 90) after amiodarone (p less than 0.005). During retrograde refractory period studies, the longest V1V2 interval at which a retrograde His bundle potential (H2) emerged from the V2 electrogram (relative refractory period of the His-Purkinje system) was consistently longer after amiodarone as compared with the control period (376.4 +/- 46.6 versus 318.8 +/- 33.1 ms, p less than 0.005). Similarly, the shortest and longest His-Purkinje system conduction times ( V2H2 interval) at comparable V1V2 intervals were uniformly and significantly prolonged after administration of the drug. Amiodarone also abolished macroreentry in the His-Purkinje system in six of the nine patients who showed such reentry during the control period. The effective refractory period of the ventricular myocardium was also increased from a mean of 227.1 +/- 13.9 to 259.2 +/- 20.2 ms (p less than 0.005) in this series of patients.(ABSTRACT TRUNCATED AT 250 WORDS)