Effect of a Single Element Subcutaneous Array Electrode Added to a Transvenous Electrode Configuration on the Defibrillation Field and the Defibrillation Threshold

Abstract

Even with the use of biphasic shocks, up to 5% of patients need an additional subcutaneous lead to obtain a defibrillation safety margin of at least 10 J. The number of patients requiring additional subcutaneous leads may even increase, because recent generation devices have a < 34 J maximum output in order to decrease their size. In 20 consecutive patients, a single element subcutaneous array lead was implanted in addition to a transvenous lead system consisting of a right ventricular (RV) and a vena cava superior lead using a single infraclavicular incision. The RV lead acted as the cathode; the subcutaneous lead and the lead in the subclavian vein acted as the anode. The biphasic defibrillation threshold was determined using a binary search protocol. Patients were randomized as to whether to start them with the transvenous lead configuration or the combination of the transvenous lead and the subcutaneous lead. In addition, a simplified assessment of the defibrillation field was performed by determining the interelectrode area for the transvenous lead only and the transvenous lead in combination with the subcutaneous lead from a biplane chest X ray. The intraoperative defibrillation threshold was reconfirmed after 1 week, after 3 months, and after 12 months. The mean defibrillation threshold with the additional subcutaneous lead was significantly (P = 0.0001) lower (5.7 +/- 2.9 J) than for the transvenous lead system (9.5 +/- 4.6 J). With the subcutaneous lead, the impedance of the high voltage circuit decreased from 48.9 +/- 7.4 omega to 39.2 +/- 5.0 omega. In the frontal plane, the interelectrode area increased by 11.3% +/- 5.5% (P < 0.0001) and in the lateral plane by 29.5% +/- 12.4% (P < 0.0001). The defibrillation threshold did not increase during follow-up. Complications with the subcutaneous electrode were not observed during a follow-up of 15.8 +/- 2 months. The single finger array lead is useful in order to lower the defibrillation threshold and can be used in order to lower the defibrillation threshold.

Incidence and clinical predictors of low defibrillation safety margin at time of implantable defibrillator implantation

“…A distal shock coil far from apex may elevate DFTs [41,42], and implanting the RV lead near septum and apex may lower DFTs [43][44][45]. Adding a shock coil in the middle cardiac vein [46][47][48][49][50] or azygous vein or implanting a subcutaneous array electrode [51][52][53][54] may be a more successful strategy for low DSM patients who failed to convert ventricular fibrillation with maximum delivered energy, especially in right-sided implant patients. The extra shock coil and subcutaneous array can substantially improve the shocking vector or waveform to obtain an adequate DSM.…”

Cardiac Amyloidosis Treated with an Implantable Cardioverter Defibrillator and Subcutaneous Array Lead System: Report of a Case and Literature Review

“…32, 8, E63-E65 (2009) helps encompass the septum and the left ventricular free wall in the defibrillation field, leading to more widespread current distribution. 11,12 Exact positioning of the SQ array is less critical than the positioning of a patch electrode. 11 In our patient, the ICD was placed on the right side of the chest because of the presence of a fistula in the left forearm.…”

Distal Right Ventricular Coil Position Reduces Defibrillation Thresholds

“…However, high DFTs still are encountered in a substantial minority of patients, 10 and this finding has been associated with an adverse prognosis 11 . Implantation of a subcutaneous array sometimes is required to achieve an adequate safety margin for defibrillation, but it may be associated with increased surgical morbidity 12,13 . As a result, there has been substantial interest in developing simpler methods to improve defibrillation efficacy that do not require implantation of additional electrodes.…”