Stark G, Sterz F, Stark U, Bachernegg M, Decrinis M, Tritthart H A
Department of Internal Medicine, Karl-Franzens-University, Graz, Austria.
J Cardiovasc Pharmacol. 1993 Jun;21(6):955-9. doi: 10.1097/00005344-199306000-00016.
Frequency-dependent depressant effects of a drug on slow channels in the atrioventricular (AV) node are important in its efficacy against supraventricular tachycardias. Verapamil terminates reentrant supraventricular arrhythmias by depressing conduction through the AV node. Similar effects have been described for adenosine. We compared the use-dependent effects of both drugs on AV nodal conduction in isolated guinea pig hearts perfused by the method of Langendorff. Adenosine 3 microM and verapamil 0.01 microM caused a comparable prolongation of AV conduction time (AVCT) and reduction in sinus rate (SR). The time dependence of drug-induced changes in AV conduction was characterized after the atrial pacing rate was changed abruptly. The basic cycle length was shortened abruptly from 240 to 180 ms. The resulting time constant for adenosine (tau = 467 +/- 187 beats, mean +/- SD) was significantly (p < 0.05) longer than that for verapamil (tau = 264 +/- 121 beats). At a pacing cycle length of 180 ms, the rate-dependent conduction slowing tended to be more pronounced in the presence of adenosine than of verapamil. Adenosine had more pronounced frequency-dependent effects on AV conduction than did the calcium channel blocker verapamil. This may explain the higher clinical efficacy of adenosine in supraventricular tachycardias in which the AV node forms a part of the reentrant circuit.
药物对房室（AV）结慢通道的频率依赖性抑制作用对其抗室上性心动过速的疗效很重要。维拉帕米通过抑制房室结传导来终止折返性室上性心律失常。腺苷也有类似作用。我们采用Langendorff灌流法，比较了这两种药物对离体豚鼠心脏房室结传导的使用依赖性作用。3微摩尔的腺苷和0.01微摩尔的维拉帕米可使房室传导时间（AVCT）延长及窦性心率（SR）降低程度相当。在心房起搏频率突然改变后，对药物诱导的房室传导变化的时间依赖性进行了表征。基础周期长度从240毫秒突然缩短至180毫秒。腺苷的时间常数（τ = 467 ± 187次搏动，均值 ± 标准差）显著（p < 0.05）长于维拉帕米（τ = 264 ± 121次搏动）。在起搏周期长度为180毫秒时，腺苷存在时速率依赖性传导减慢往往比维拉帕米存在时更明显。腺苷对房室传导的频率依赖性作用比钙通道阻滞剂维拉帕米更显著。这可能解释了腺苷在房室结构成折返环路一部分的室上性心动过速中临床疗效更高的原因。
