Jones G K, Poole J E, Kudenchuk P J, Dolack G L, Johnson G, DeGroot P, Gleva M J, Raitt M, Bardy G H
Department of Medicine, University of Washington School of Medicine, Seattle 98195, USA.
Circulation. 1995 Nov 15;92(10):2940-3. doi: 10.1161/01.cir.92.10.2940.
The active can unipolar implantable cardioverter-defibrillator (ICD) has been shown to defibrillate efficiently, but its current 80-cc size limits use in the pectoral position in many patients. Decreasing can size will facilitate pectoral insertion and will soon be feasible as an inevitable consequence of technological advancements. However, decreasing the can size has the potential to compromise unipolar defibrillation efficacy. It is the purpose of this study, therefore, to prospectively and randomly compare unipolar defibrillation efficacy with 80-cc, 60-cc, and 40-cc can sizes in patients immediately before ICD surgery in anticipation of advances in technology that will make smaller ICDs possible.
Twenty-four consecutive patients underwent prospective, randomized evaluation of the effect of ICD can size on defibrillation efficacy during standard ICD surgery. Each patient had the unipolar defibrillation threshold (DFT) measured with 80-cc, 60-cc, or 40-cc active can placed in the left subcutaneous infraclavicular region. The system included a 10.5F tripolar right ventricular electrode that served as the shock anode. The shock waveform used in each instance was a single capacitor biphasic 65% pulse delivered from a 120-microF capacitor. Stored energy at the DFT for the 80-cc, 60-cc, and 40-cc cans were 8.1 +/- 4.7 J, 8.7 +/- 5.8 J, and 9.5 +/- 4.8 J, respectively. There was no statistical significant difference between the DFTs for the three unipolar can electrodes (P = 39). Leading edge voltage also did not differ significantly among the three unipolar cans (356 +/- 92 V, 365 +/- 110 V, and 387 +/- 94 V, respectively, P = .29). There was, however, a slight progressive increase in resistance with decreasing can size (57 +/- 7 omega, 60 +/- 9 omega, and 65 +/- 9 omega, respectively, P < .001).
Decreasing can volume from 80 cc to 60 cc to 40 cc does not compromise unipolar defibrillation efficacy despite a slight rise in shock resistance. These findings indicate that technological advances that allow for smaller-volume ICDs will not compromise defibrillation efficacy for unipolar systems.
有源单极植入式心律转复除颤器（ICD）已被证明能有效除颤，但其目前80立方厘米的体积限制了在许多患者胸壁位置的使用。减小外壳体积将便于在胸壁植入，并且随着技术进步这很快将成为可能。然而，减小外壳体积有可能损害单极除颤效果。因此，本研究的目的是在ICD手术前，对患者前瞻性、随机地比较80立方厘米、60立方厘米和40立方厘米外壳体积的单极除颤效果，以期待技术进步能使更小的ICD成为可能。
24例连续患者在标准ICD手术期间接受了关于ICD外壳体积对除颤效果影响的前瞻性、随机评估。每位患者在左锁骨下皮下区域分别放置80立方厘米、60立方厘米或40立方厘米的有源外壳来测量单极除颤阈值（DFT）。该系统包括一个10.5F三极右心室电极作为电击阳极。每次使用的电击波形是由一个120微法电容器释放的单电容双相65%脉冲。80立方厘米、60立方厘米和40立方厘米外壳在DFT时的储存能量分别为8.1±4.7焦耳、8.7±5.8焦耳和9.5±4.8焦耳。三种单极外壳电极的DFT之间无统计学显著差异（P=0.39）。三种单极外壳的前沿电压也无显著差异（分别为356±92伏、365±110伏和387±94伏，P=0.29）。然而，随着外壳体积减小电阻略有逐渐增加（分别为57±7欧姆、60±9欧姆和65±9欧姆，P＜＜0.001）。
尽管电击电阻略有上升，但将外壳体积从80立方厘米减小到60立方厘米再减小到40立方厘米不会损害单极除颤效果。这些发现表明，允许使用更小体积ICD的技术进步不会损害单极系统的除颤效果。
