Fan W, Gotoh M, Chen P S
Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, California 90048, USA.
Pacing Clin Electrophysiol. 1995 Jun;18(6):1279-84. doi: 10.1111/j.1540-8159.1995.tb06969.x.
In six open chest dogs, we determined the upper limit of vulnerability (ULV) and defibrillation threshold (DFT) by an up-down algorithm when the pacing site was at the right atrium, at the left ventricular apex, and at the left ventricular base. Monophasic shocks (6 ms) were given to epicardial patches at 20 and 40 ms before the peak of the T wave to bracket the mid-upslope. In an additional six closed-chest dogs, we determined the ULV and the DFT with transvenous leads with an 8-ms biphasic waveform. The S1 pacing site was at the right ventricular apex and the right atrium, and the shocks were given at 20 ms and 40 ms before the peak of the T wave, and on the peak of T wave. The same test was repeated after intravenous procainamide infusion (20 mg/Kg loading, then 2 mg/min maintenance). In the first six dogs, the ULV determined when pacing was given to the left ventricular apex, the left ventricular base, and the right atrium was 4.2 +/- 1.7 J, 4.4 +/- 2.1 J, and 3.9 +/- 1.5 J, respectively; values that were not significantly different from the DFT of 4.8 +/- 1.9 J, 4.5 +/- 1.9 J, and 4.2 +/- 1.3 J, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
在6只开胸犬中，当起搏部位分别位于右心房、左心室心尖部和左心室基部时，我们采用上下算法确定了易损性上限（ULV）和除颤阈值（DFT）。在T波峰值前20和40毫秒时，向心外膜贴片给予6毫秒的单相电击，以覆盖上升支中部。在另外6只闭胸犬中，我们使用8毫秒双相波形的经静脉导线确定了ULV和DFT。S1起搏部位位于右心室心尖部和右心房，电击分别在T波峰值前20毫秒和40毫秒以及T波峰值时给予。静脉输注普鲁卡因酰胺（负荷量20毫克/千克，然后以2毫克/分钟维持）后重复相同测试。在前6只犬中，当起搏部位为左心室心尖部、左心室基部和右心房时，确定的ULV分别为4.2±1.7焦耳、4.4±2.1焦耳和3.9±1.5焦耳；这些值分别与DFT的4.8±1.9焦耳、4.5±1.9焦耳和4.2±1.3焦耳无显著差异。（摘要截断于250字）
