Lang J, Timour Q, Lancon J P, Aupetit J F, Bertrix L, Faucon G
Department of Medical Pharmacology, Claude Bernard University, Lyon, France.
Fundam Clin Pharmacol. 1989;3(3):281-94. doi: 10.1111/j.1472-8206.1989.tb00457.x.
The cardiac adrenergic system is known to have practically no influence on conduction velocity in the ventricles under normal conditions. The effects of isoproterenol and propranolol were investigated on depression of intraventricular conduction induced by a class IC antiarrhythmic drug, cibenzoline, in anaesthetized, closed-chest dogs. In addition to electrocardiogram for measurement of QRS duration in sinus rhythm, conduction time was measured in the ventricular contractile tissue between an electrode advanced to the apex and a pacing electrode near the base, at 400- and 200-ms pacing periods. Effective refractory period (ERP) was measured concurrently according to the extrastimulus method. After intraventricular conduction had been slowed down by cibenzoline IV administered (loading dose of 3 mg/kg plus infusion of 0.2 mg/kg/min over 15 min), isoproterenol was infused or propranolol injected by the intravenous route also (0.5 mn/micrograms/kg/min over 5 min and 0.4 mg/kg, respectively). When conduction time has been raised by 75/150% (depending on the pacing rate), isoproterenol appears to attenuate and propranolol to aggravate substantially the impairment of conduction, whereas the reduction undergone by ERP does not differ from usual. Thus, reentrant arrhythmias might be prevented by isoproterenol and triggered by propranolol. Intraventricular conduction, when depressed, therefore, is sensitive to adrenergic drugs, probably because of the enhanced influence of polarization of the fibres in the presence of a sodium conductance impairment.
已知在正常情况下，心脏肾上腺素能系统对心室传导速度几乎没有影响。研究了异丙肾上腺素和普萘洛尔对IC类抗心律失常药物西苯唑啉诱导的麻醉开胸犬室内传导抑制的影响。除了在窦性心律下测量QRS波时限的心电图外，还在400毫秒和200毫秒的起搏周期下，测量了从心尖推进的电极与靠近心底的起搏电极之间心室收缩组织的传导时间。同时根据额外刺激法测量有效不应期（ERP）。静脉注射西苯唑啉（负荷剂量3mg/kg，在15分钟内以0.2mg/kg/分钟的速度输注）使室内传导减慢后，也通过静脉途径输注异丙肾上腺素或注射普萘洛尔（分别在5分钟内以0.5μg/kg/分钟的速度输注和注射0.4mg/kg）。当传导时间增加75/150%（取决于起搏频率）时，异丙肾上腺素似乎可减轻而普萘洛尔则会显著加重传导障碍，而ERP的缩短与通常情况并无差异。因此，异丙肾上腺素可能预防折返性心律失常，而普萘洛尔可能引发此类心律失常。因此，当室内传导受到抑制时，其对肾上腺素能药物敏感，这可能是因为在存在钠电导损害的情况下，纤维极化的影响增强。
