Kontos M C, Ellenbogen K A, Wood M A, Damiano R J, Akosah K O, Nixon J V, Stambler B S
Division of Cardiology and Cardiothoracic Surgery, Medical College of Virginia, Virginia Commonwealth University, Richmond, USA.
Am J Cardiol. 1997 Jan 1;79(1):48-52. doi: 10.1016/s0002-9149(96)00674-1.
Peak current flow across the heart determines the success of defibrillation and is inversely dependent on impedance between defibrillation electrodes. Factors associated with elevated impedance in patients with implantable defibrillators using nonthoracotomy lead systems have not been well described. Clinical and echocardiographically derived variables were analyzed in 41 patients in whom implantation of a nonthoracotomy lead system was attempted. Lead impedance was measured at end-expiration with 5-J monophasic shocks. Successful defibrillation with or without addition of a subcutaneous patch with < or = 20 J with a monophasic waveform was required for nonthoracotomy lead placement. Patients were divided into 2 groups based on impedance: low (< or = 47 ohms, n = 30) and high (>47 ohms, n = 11). Twenty-four patients had successful defibrillator implantation using a transvenous lead alone, 13 required placement of a subcutaneous patch, and 4 required epicardial patch placement. The mean left ventricular end-diastolic and end-systolic volumes were significantly smaller (p = 0.01 for both) in patients in the low- versus high-impedance groups and were significantly correlated with impedance (r = 0.44, p <0.005 for both). Impedance was not significantly different between patients with successful defibrillation using a transvenous lead alone compared with those who required either subcutaneous or epicardial patches. Thus, impedance using a nonthoracotomy lead system with monophasic shocks is significantly correlated with both end-systolic and end-diastolic volumes, but elevated impedance does not predict increased defibrillation energy requirements.
流经心脏的峰值电流决定了除颤的成功率，且与除颤电极之间的阻抗呈反比。对于使用非开胸导联系统的植入式除颤器患者，与阻抗升高相关的因素尚未得到充分描述。对41例尝试植入非开胸导联系统的患者的临床和超声心动图衍生变量进行了分析。在呼气末用5焦耳单相电击测量导联阻抗。非开胸导联放置需要使用单相波形、能量≤20焦耳进行除颤，无论是否添加皮下贴片，除颤成功即可。根据阻抗将患者分为两组：低阻抗组（≤47欧姆，n = 30）和高阻抗组（>47欧姆，n = 11）。24例患者仅使用经静脉导联成功植入除颤器，13例需要放置皮下贴片，4例需要放置心外膜贴片。低阻抗组患者的平均左心室舒张末期和收缩末期容积明显较小（两者p = 0.01），且与阻抗显著相关（r = 0.44，两者p <0.005）。仅使用经静脉导联成功除颤的患者与需要皮下或心外膜贴片的患者之间的阻抗无显著差异。因此，使用非开胸导联系统和单相电击时，阻抗与收缩末期和舒张末期容积均显著相关，但阻抗升高并不能预测除颤能量需求增加。
