Addition of a Defibrillation Electrode in the Low Right Atrium to a Right Ventricular Lead Does Not Reduce Ventricular Defibrillation Thresholds

Abstract

Transvenous unipolar active can defibrillation systems have proven to be effective in treating ventricular tachyarrhythmias. However, a further reduction of ventricular defibrillation thresholds (V-DFT) would increase the longevity, reduce the size of pulse generators, and help to avoid additional leads in patients with inacceptable high V-DFTs. In a finite difference computer model, the extension of the right ventricular (RV) defibrillation coil into the low right atrium led to a 40% reduction of unipolar V-DFT. To evaluate this finding, we conducted a prospective, randomized study in 11 patients receiving an ICD. Extension of the RV electrode was simulated by adding a second coil placed in the low right atrium with the same polarity. Using a binary search protocol, V-DFT was determined with and without the additional electrode in each patient. Total shock impedance was significantly lower in the two coil (low RA) configuration, compared to the single coil (RV) configuration. Corresponding values were 49.9 +/- 6.7 Ohm and 61.1 +/- 9.3 Ohm, respectively (P < 0.01, paired t-test). However, there was no reduction, but even a nonsignificant increase in V-DFTs. Mean V-DFT in the RV configuration was 12.0 +/- 5.6 J and 16.3 +/- 7.8 J in the low RA configuration (P = 0.09, paired t-test). Despite a reduction in total impedance, the addition of a defibrillation coil in the low right atrium does not reduce ventricular defibrillation thresholds.

Dual- versus single-coil implantable defibrillator leads: review of the literature

“…In five studies enrolling the total number of 279 tested patients, no statistically significant difference in DFTs between dual-coil and single-coil leads was reported [24][25][26][27][28]. The mean DFTs for dual-coil leads ranged from 7.4 ± 5.2 to 16.3 ± 7.8 J, compared to DFTs with singlecoil leads ranging from 6.0 ± 3.4 to 12 ± 5.6 J.…”

“…Some studies suggest placement of the SVC coil in the low right atrium may increase DFT due to negative current vector effects [28,47]. Conversely, other studies failed to show clinically significant differences in DFT with SVC-coil placement in the right atrium-superior vena cava position versus higher placements (innominate vein-superior vena cava).…”

Defibrillation Waveform Duration Adjustment Increases the Proportion of Acceptable Defibrillation Thresholds in Patients Implanted with Single-Coil Defibrillation Leads

“…The method of DFT testing used in this study differs from other protocols used in previous studies [11,13,14,18]. It is mostly driven by the need of simplification of the implant procedure, a decrease in number of ventricular fibrillation inductions and rapid determination of safety margins.…”

Are Dual‐Coil ICD Leads Obsolete?

“…As reviewed by Neuzner and Carlsson, there were five reports involving 279 patients (including three randomized studies; Refs. ) that demonstrated no statistically significant difference in DFTs between dual‐coil and single‐coil leads in pectoral ICDs.…”