Reiter M J, Lindenfeld J, Tyndal C M, Breckinridge S, Mann D E
Department of Medicine, University of Colorado Health Sciences Center, Denver 80262.
J Am Coll Cardiol. 1989 Jan;13(1):180-4. doi: 10.1016/0735-1097(89)90568-8.
The effects of transthoracic and internal defibrillation on the bipolar ventricular pacing threshold in 20 anesthetized dogs were examined. Ventricular pacing was accomplished with a computer-controlled, constant voltage pacemaker that permitted rapid determination of pacing threshold. Defibrillation at various energy levels was administered during ventricular pacing and after ventricular fibrillation of 5, 15, 30, 45, 60 or 120 s duration in the 20 dogs. Defibrillation during pacing or within 15 s after initiation of ventricular fibrillation did not significantly increase threshold, regardless of defibrillation energy or mode of delivery. Defibrillation after ventricular fibrillation lasting greater than or equal to 30 s increased (p less than 0.05) threshold determined 6 s after defibrillation. The increase in threshold (in volts) determined 6 s after defibrillation was an exponential function of fibrillation duration (30 s = 0.30 +/- 0.09 V; 45 s = 0.53 +/- 0.13 V; 60 s = 2.24 +/- 1.05 V), but was independent of defibrillation energy or mode of delivery. Threshold returned to control values 15 to 30 s after defibrillation. Cardiopulmonary bypass to maintain coronary perfusion prevented the increase in pacing threshold even after ventricular fibrillation of up to 2 min duration. Pacing threshold is not increased by transthoracic or internal defibrillation, but is increased by ventricular fibrillation of sufficient duration to create substantial myocardial hypoxemia.
研究了经胸和体内除颤对20只麻醉犬双极心室起搏阈值的影响。采用计算机控制的恒压起搏器进行心室起搏，该起搏器可快速测定起搏阈值。在20只犬的心室起搏期间以及持续5、15、30、45、60或120秒的心室颤动后，给予不同能量水平的除颤。无论除颤能量或发放方式如何，起搏期间或心室颤动开始后15秒内除颤均未显著增加阈值。心室颤动持续大于或等于30秒后除颤，会使除颤后6秒测定的阈值升高（p<0.05）。除颤后6秒测定的阈值升高（以伏特为单位）是颤动持续时间的指数函数（30秒=0.30±0.09伏；45秒=0.53±0.13伏；60秒=2.24±1.05伏），但与除颤能量或发放方式无关。除颤后15至30秒，阈值恢复到对照值。即使在长达2分钟的心室颤动后，通过体外循环维持冠状动脉灌注也可防止起搏阈值升高。经胸或体内除颤不会增加起搏阈值，但足够长时间的心室颤动导致严重心肌缺氧时会增加起搏阈值。
