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 protoc...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 amioda- rone, 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.展开更多
The traditional critical membrane potential (CMP), -55—-60mV, which corresponds to effective refractory period (ERP), was anew investigated in guinea pig ventricular muscle fibres. The electrical and contractile resp...The traditional critical membrane potential (CMP), -55—-60mV, which corresponds to effective refractory period (ERP), was anew investigated in guinea pig ventricular muscle fibres. The electrical and contractile responses to the stimulus during repolarization of action potential (AP), particularly from+10 to -60 mV, were observed. One third of 35 tested cells displayed testing action potential (TAP) and local response at≥-54 mV when they were stimulated by testing pulses in 37℃ normal Tyrode's solution. Potential level of TAP which occurred earliest was at -30 mV and that of local response which appeared earliest was at 0 mV during repolarization among 95 systematic tests. Most of the TAPs belonged to the slow response potential type. The ratio of TAP evoked at ≥-54 mV initial membrane potential (IMP) was as high as 86% when the experiment was carried out in 37℃ 1.5 mmol KC1/L Tyrode's solution. In view of distribution of IMPs of TAPs, the CMP of ERP in guinea pig ventricular muscle fibres was more positive than traditional CMP measured by Hoffman et al. in dog, sheep Purkinje fibres and had a quite changeable range. The CMP of every cell in ventricular muscle was not all the same, and their CMPs approximated to normal distribution. There was no sharp line separating ERP from relative refractory period in myocardium. Higher temperature and low [K]_0 were the important factors elevating CMP of ERP.展开更多
文摘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 amioda- rone, 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.
文摘The traditional critical membrane potential (CMP), -55—-60mV, which corresponds to effective refractory period (ERP), was anew investigated in guinea pig ventricular muscle fibres. The electrical and contractile responses to the stimulus during repolarization of action potential (AP), particularly from+10 to -60 mV, were observed. One third of 35 tested cells displayed testing action potential (TAP) and local response at≥-54 mV when they were stimulated by testing pulses in 37℃ normal Tyrode's solution. Potential level of TAP which occurred earliest was at -30 mV and that of local response which appeared earliest was at 0 mV during repolarization among 95 systematic tests. Most of the TAPs belonged to the slow response potential type. The ratio of TAP evoked at ≥-54 mV initial membrane potential (IMP) was as high as 86% when the experiment was carried out in 37℃ 1.5 mmol KC1/L Tyrode's solution. In view of distribution of IMPs of TAPs, the CMP of ERP in guinea pig ventricular muscle fibres was more positive than traditional CMP measured by Hoffman et al. in dog, sheep Purkinje fibres and had a quite changeable range. The CMP of every cell in ventricular muscle was not all the same, and their CMPs approximated to normal distribution. There was no sharp line separating ERP from relative refractory period in myocardium. Higher temperature and low [K]_0 were the important factors elevating CMP of ERP.
