Cha Y M, Peters B B, Chen P S
Department of Medicine, University of California, San Diego.
J Am Coll Cardiol. 1994 Jun;23(7):1688-92. doi: 10.1016/0735-1097(94)90676-9.
This study was performed to test the hypothesis that sodium channel activity is important in determining ventricular vulnerability to electric shocks.
It is unknown whether sodium channel activity determines the upper limit of vulnerability.
The ventricles of 10 open chest dogs were paced at 300-, 500-, or 1,000-ms cycle lengths. The shock strength associated with a 50% probability of reaching the upper limit of vulnerability (ULV50) and the shock strength associated with a 50% probability of defibrillation (DFT50) were then determined by means of an up-down algorithm. Lidocaine (9.2-mg/kg body weight loading dose and 285-micrograms/kg per min maintenance dose) was then given, and the ULV50 and the DFT50 were redetermined after 1 h of stable infusion.
The mean (+/- SD) lidocaine concentration was 11.9 +/- 2.4 micrograms/ml. At baseline, the ULV50 tested with each S1 cycle length was not significantly different from the DFT50. During lidocaine infusion, the ULV50 determined with cycle lengths of 300 and 500 ms (18.9 +/- 11.3 and 16.1 +/- 8.9 J, respectively) were significantly (p < 0.05) higher than those simultaneously determined for the DFT50 (11.2 +/- 4.1 and 10.9 +/- 5.6 J, respectively). However, when determined with an S1 cycle length of 1,000 ms, the ULV50 (10.4 +/- 4.1 J) was not found to be significantly different from the DFT50 (10.3 +/- 5.3 J). Lidocaine infusion increased (p < 0.05) QRS duration and the effective refractory periods for cycle lengths of 300 and 500 ms but not 1,000 ms.
The effect of lidocaine on the upper limit of vulnerability is use dependent. These results are compatible with the hypothesis that sodium channel activity is important in determining ventricular vulnerability to electrical shocks.
本研究旨在验证钠通道活性在决定心室对电击的易损性方面很重要这一假设。
钠通道活性是否决定易损性的上限尚不清楚。
对10只开胸犬的心室以300毫秒、500毫秒或1000毫秒的周期长度进行起搏。然后通过上下算法确定与达到易损性上限（ULV50）的50%概率相关的电击强度以及与除颤（DFT50）的50%概率相关的电击强度。随后给予利多卡因（9.2毫克/千克体重负荷剂量和285微克/千克每分钟维持剂量），在稳定输注1小时后重新确定ULV50和DFT50。
利多卡因的平均（±标准差）浓度为11.9±2.4微克/毫升。在基线时，每个S1周期长度测试的ULV50与DFT50无显著差异。在输注利多卡因期间，以300毫秒和500毫秒周期长度确定的ULV50（分别为18.9±11.3焦耳和16.1±8.9焦耳）显著（p<0.05）高于同时确定的DFT50（分别为11.2±4.1焦耳和10.9±5.6焦耳）。然而，当以1000毫秒的S1周期长度确定时，未发现ULV50（10.4±4.1焦耳）与DFT50（10.3±5.3焦耳）有显著差异。输注利多卡因使300毫秒和500毫秒周期长度的QRS时限和有效不应期增加（p<0.05），但1000毫秒周期长度的未增加。
利多卡因对易损性上限的影响是使用依赖性的。这些结果与钠通道活性在决定心室对电击的易损性方面很重要这一假设相符。
