Bardy G H, Poole J E, Kudenchuk P J, Dolack G L, Mehra R, DeGroot P, Raitt M H, Jones G K, Johnson G
Department of Medicine, University of Washington, Seattle.
Circulation. 1995 Jan 1;91(1):91-5. doi: 10.1161/01.cir.91.1.91.
Improving unipolar implantable cardioverter-defibrillator (ICD) effectiveness has favorable implications for ICD safety, efficacy, and size. Advances in defibrillation efficacy would accelerate ICD ease of use by decreasing device size and by minimizing morbidity and mortality related to an improved defibrillation safety margin. The specific purpose of the present study was to determine whether unipolar defibrillation efficacy could be improved further in humans by lowering biphasic waveform capacitance.
We prospectively and randomly compared the defibrillation efficacy of a 60-microF and a 120-microF capacitance asymmetrical 65% tilt biphasic waveform using a unipolar defibrillation system in 38 consecutive cardiac arrest survivors before implantation of a presently available standard transvenous defibrillation system. The right ventricular defibrillation electrode had a 5-cm coil located on a 10.5F lead and was used as the anode. The system cathode was the electrically active 108-cm2 surface area shell (or "can") of a prototype titanium alloy pulse generator placed in a left infraclavicular pocket. The defibrillation pulse was derived from either a 60-microF or a 120-microF capacitance and was delivered from RV-->CAN. Defibrillation threshold (DFT) stored energy, delivered energy, leading-edge voltage and current, pulse resistance, and pulse width were measured for both capacitances examined. The 60-microF capacitance biphasic pulse resulted in a stored-energy DFT of 8.5 +/- 4.1 J and a delivered-energy DFT of 8.4 +/- 4.0 J. In 34 of 38 patients (89%), the stored-energy DFT was < 15 J. Leading-edge voltage at the DFT was 517 +/- 128 V. Mean pulse impedance for the 60-microF waveform was 60.6 +/- 7.1 omega. The 120-microF capacitance biphasic pulse resulted in a stored-energy DFT of 10.1 +/- 7.4 J and a delivered-energy DFT of 10.0 +/- 7.2 J (P = .13 and .13, respectively). In 28 of 38 patients (74%), the stored-energy DFT was < 15 J (P = .052). Leading-edge voltage at the DFT with the 120-microF capacitance pulse was 386 +/- 142 (P < .00001). Mean pulse impedance for the 120-microF waveform was 60.7 +/- 7.0 omega (P = .80).
The results of the present study suggest that a relatively small capacitance, 60 microF, can be used for unipolar defibrillation systems without compromising defibrillation energy requirements compared with more typical ICD capacitance values, but this will require a higher circuit voltage. The use of lower capacitance also provides a modest increase in the percent of patients who have very low energy defibrillation requirements, an important issue should maximum ICD energy be decreased from the present level of 34 J. Such a move to smaller output devices could allow significant decreases in device size, a necessary feature of making cardioverter-defibrillator implantation comparable to that of standard pacemaker surgery.
提高单极植入式心脏复律除颤器（ICD）的有效性对ICD的安全性、疗效和尺寸具有积极影响。除颤疗效的进步将通过减小设备尺寸以及将与改善的除颤安全裕度相关的发病率和死亡率降至最低来加速ICD的易用性。本研究的具体目的是确定通过降低双相波形电容是否可以进一步提高人体单极除颤疗效。
在植入当前可用的标准经静脉除颤系统之前，我们使用单极除颤系统对38例连续心脏骤停幸存者进行了前瞻性随机比较，比较了60微法和120微法电容的不对称65%倾斜双相波形的除颤疗效。右心室除颤电极在一根10.5F的导线上有一个5厘米的线圈，用作阳极。系统阴极是置于左锁骨下口袋的原型钛合金脉冲发生器的108平方厘米电活性表面积外壳（或“罐体”）。除颤脉冲源自60微法或120微法电容，从右心室传输至罐体。对所检查的两种电容测量除颤阈值（DFT）、存储能量、输送能量、前沿电压和电流、脉冲电阻以及脉冲宽度。60微法电容的双相脉冲导致存储能量DFT为8.5±4.1焦耳，输送能量DFT为8.4±4.0焦耳。在38例患者中的34例（89%），存储能量DFT＜15焦耳。DFT时的前沿电压为517±128伏。60微法波形的平均脉冲阻抗为60.6±7.1欧姆。120微法电容的双相脉冲导致存储能量DFT为10.1±7.4焦耳，输送能量DFT为10.0±7.2焦耳（P分别为0.13和0.13）。在38例患者中的28例（74%），存储能量DFT＜15焦耳（P = 0.052）。120微法电容脉冲在DFT时的前沿电压为386±
