RESUMO
The effects of amiodarone on transmural dispersion of ventricular effective refractory periods (ERPs) in the normal and hypertrophic canine heart were investigated in vivo. By using the programmed stimulation protocol, the ERPs of epicardium (Epi), midmyocardium (Mid) and endocardium (Endo) were measured by inserting specially-designed electrodes into the three myocardial layers before and after mainlining of amiodarone. No significant ERPs-dispersion was observed in the three layers before and after mainlining of amiodarone in the normal group. In contrast, ERPs of all the three layers were prolonged in the hypertrophic heart, while the ERPs-dispersion was reduced significantly after mainlining of amiodarone. The ERPs-dispersion was significantly increased in the hypertrophic heart but not in the normal heart using "long-short" and "short-long" interval stimulation technique. It was concluded that (1) the differences in ERPs-dispersion among the three layers were significant in hypertrophic heart, and differences were not significant in normal canine heart;(2) ERPs of each three-myocardial layers were significantly prolonged after using amiodarone, but the ERPs-dispersion decreased in hypertrophic heart and (3) the programmed extrastimulus technique of "long-short" and "short-long" intervals increased the transmural ERPs-dispersion in the hypertrophic heart.
RESUMO
The effects of amiodarone on transmural dispersion of ventricular effective refractory periods (ERPs) in the normal and hypertrophic canine heart were investigated in vivo. By using the programmed stimulation protocol, the ERPs of epicardium (Epi), midmyocardium (Mid) and endocardium (Endo) were measured by inserting specially-designed electrodes into the three myocardial layers before and after mainlining of amiodarone. No significant ERPs-dispersion was observed in the three layers before and after mainlining of amiodarone in the normal group. In contrast, ERPs of all the three layers were prolonged in the hypertrophic heart, while the ERPs-dispersion was reduced significantly after mainlining of amiodarone. The ERPs-dispersion was significantly increased in the hypertrophic heart but not in the normal heart using "long-short" and "short-long" interval stimulation technique. It was concluded that (1) the differences in ERPs-dispersion among the three layers were significant in hypertrophic heart, and differences were not significant in normal canine heart; (2) ERPs of each three-myocardial layers were significantly prolonged after using amiodarone, but the ERPs-dispersion decreased in hypertrophic heart and (3) the programmed extrastimulus technique of "long-short" and "short-long" intervals increased the transmural ERPs-dispersion in the hypertrophic heart.
RESUMO
The effect of acute ischemia on the electrophysiological characteristics of the three layers myocardium of canine in vivo was investigated. Twelve canines were divided into two groups randomly: acute ischemia (AI) group and sham operation (SO) group. By using the monophasic action potential (MAP) technique, MAP and effective refractory period (ERP) of thethree layers myocar dium were measured by specially designed plunge needle electrodes and the transmural dispersion of repolarization (TDR) and transmural dispersion of ERP (TDE) were analyzed. The results showed that in the AI group, MAP duration (MAPD) was shortened from 201.67±21.42 ms to 169.50±13.81 ms (P＜0.05), but ERP prolonged to varying degrees and TDE increased during ischemia.In the SO group, MAPD and ERP did not change almost. Among of the three layers myocardium of canine, MAPD was coincident in two groups. It was concluded that during acute ischemia, MAPD was shortened sharply, but there was no significant difference among of the three layers myocardium. The prolonged ERP was concomitant with increased TDE during acute ischemia, which may play an important role in the occurrence of arrhythmias induced by acute ischemia. These findings may have important implications in arrhythmogenesis.
RESUMO
The effect of acute ischemia on the electrophysiological characteristics of the three layers myocardium of canine in vivo was investigated. Twelve canines were divided into two groups randomly: acute ischemia (AI) group and sham operation (SO) group. By using the monophasic action potential (MAP) technique, MAP and effective refractory period (ERP) of the three layers myocardium were measured by specially designed plunge needle electrodes and the transmural dispersion of repolarization (TDR) and transmural dispersion of ERP (TDE) were analyzed. The results showed that in the AI group, MAP duration (MAPD) was shortened from 201.67 +/- 21.42 ms to 169.50 +/- 13.81 ms (P < 0.05), but ERP prolonged to varying degrees and TDE increased during ischemia. In the SO group, MAPD and ERP did not change almost. Among of the three layers myocardium of canine, MAPD was coincident in two groups. It was concluded that during acute ischemia, MAPD was shortened sharply, but there was no significant difference among of the three layers myocardium. The prolonged ERP was concomitant with increased TDE during acute ischemia, which may play an important role in the occurrence of arrhythmias induced by acute ischemia. These findings may have important implications in arrhythmogenesis.