Niebauer M J, Babbs C F, Geddes L A, Carter J E, Bourland J D
Jpn Heart J. 1984 Sep;25(5):773-81. doi: 10.1536/ihj.25.773.
The overdose shock strengths required to depress ventricular contraction were determined for damped sinusoidal current in 7 metabolically supported, isolated contracting canine hearts. Each heart was suspended in an isoresistive and isotonic solution-through which the defibrillating shocks were delivered. Defibrillation thresholds were determined with standard damped sine wave shocks of 4.4-5.5 msec duration. Then overdose shocks were delivered and the depressant effect on systolic left ventricular pressure was measured for shocks of 3-12 times threshold current. The minimum (threshold) current and energy densities required to defibrillate were 59.5 +/- 4.6 mA/cm2 (average) and 3.12 +/- 0.2 mJ/cm3. Increasing the shock strength above threshold produced a concomitant reduction of postshock left ventricular systolic pressure. The current and energy densities required to produce 50% depression (TD50) of left ventricular systolic pressure were 5.0 and 24.1 times the threshold current and energy densities respectively, indicating a wide safety margin using this criterion.
在7个代谢支持的离体收缩犬心脏中，测定了抑制心室收缩所需的过剂量电击强度，采用阻尼正弦电流。每个心脏悬浮在等电阻和等渗溶液中，通过该溶液施加除颤电击。用持续时间为4.4-5.5毫秒的标准阻尼正弦波电击测定除颤阈值。然后施加过剂量电击，并测量3-12倍阈值电流电击对左心室收缩压的抑制作用。除颤所需的最小（阈值）电流和能量密度分别为59.5±4.6 mA/cm2（平均值）和3.12±0.2 mJ/cm3。将电击强度增加到阈值以上会导致电击后左心室收缩压相应降低。产生左心室收缩压50%抑制（TD50）所需的电流和能量密度分别是阈值电流和能量密度的5.0倍和24.1倍，这表明使用该标准有很大的安全余量。
