Zienciuk Agnieszka, Lubiński Andrzej, Królak Tomasz, Lewicka-Nowak Ewa, Kempa Maciej, Pazdyga Anna, Raczak Grzegorz
Department of Cardiology, Medical Academy, Gdańsk, Poland.
Kardiol Pol. 2007 May;65(5):495-500; discussion 501-2.
An increased defibrillation threshold (DFT) may limit the efficacy of an implantable cardioverter-defibrillator (ICD) in termination of life-threatening ventricular arrhythmias. A search for methods of decreasing DFT has been ongoing since the introduction of ICD into clinical practice.
To assess the effects of various shock polarities on DFT.
The study group consisted of 19 patients (8 females and 11 males, mean age 52+/-17 years) who received devices (Biotronik, Germany) with a single-coil defibrillation lead. In all patients the value of DFT was assessed using a normal shock polarity as well as using a reversed polarity shock, starting from the energy lower than that measured during normal DFT testing. The impedance of the defibrillation system using two different polarities was also measured. The effects of demographic and clinical parameters on defibrillation parameters were also examined.
When using normal shock polarity, the mean DFT value was 12+/-5 J (range 3.1-20 J) and impedance was 64+/-12 Omega. When shock polarity was reversed, the mean DFT value was 9.2+/-5.0 J (range 2-20 J) and impedance was 67+/-11 Omega. In 11 (58%) patients the polarity change caused a marked (by 37%) decrease in the mean DFT value - from 11.5+/-5.1 J to 7.2+/-3.8 J. In 5 patients DFT reduction was > or = 5 J. There was no relationship between demographic or clinical parameters and defibrillation efficacy using the two tested shock polarities.
The reversal of shock polarity reduces DFT in more than half of patients. In patients with a high DFT the use of reversed polarity of defibrillating impulse may reduce DFT, which widens the safety margin and makes implantation of additional leads unnecessary. Because clinical parameters have no value in predicting the effects of polarity changes on DFT, the efficacy of reversed polarity shock has to be assessed individually in each patient.
除颤阈值（DFT）升高可能会限制植入式心脏复律除颤器（ICD）终止危及生命的室性心律失常的疗效。自ICD引入临床实践以来，一直在探索降低DFT的方法。
评估不同电击极性对DFT的影响。
研究组由19例患者（8例女性和11例男性，平均年龄52±17岁）组成，这些患者接受了带有单线圈除颤导线的设备（德国百多力公司）。在所有患者中，DFT值的评估采用正常电击极性以及反向电击极性，起始能量低于正常DFT测试时测得的能量。还测量了使用两种不同极性时除颤系统的阻抗。同时研究了人口统计学和临床参数对除颤参数的影响。
使用正常电击极性时，平均DFT值为12±5J（范围3.1 - 20J），阻抗为64±12Ω。当电击极性反转时，平均DFT值为9.2±5.0J（范围2 - 20J），阻抗为67±11Ω。11例（58%）患者极性改变导致平均DFT值显著降低（降低37%），从11.5±5.1J降至7.2±3.8J。5例患者DFT降低≥5J。人口统计学或临床参数与使用两种测试电击极性时的除颤效果之间无相关性。
电击极性反转可使一半以上患者的DFT降低。对于DFT较高的患者，使用反向除颤脉冲极性可降低DFT，这拓宽了安全范围，无需植入额外导线。由于临床参数对预测极性改变对DFT的影响无价值，因此必须对每位患者单独评估反向电击极性的疗效。
