Abstract 3256: Effect of SVC Coil Usage and SVC Electrode Spacing on Defibrillation Thresholds
Background: Prior studies of active pectoral implantable defibrillator (ICD) lead systems demonstrated a lowering of defibrillation thresholds (DFTs) with the addition of a superior vena cava (SVC) coil. Fixed tilt waveforms were evaluated in these studies, and theoretic modeling suggests that impedance based “tuned” waveform durations may be beneficial by directly changing t he phase durations. The impacts of such tuned waveforms, as well as intercoil spacing, have not been studied previously.
Methods: This acute, paired-sample, double randomized study included 113 ICD patients, mean age 67 ±13 years, 80% male, LVEF 31±11%, NYHA Class I (12%), II (33%) and III (25%). The patients were randomized at implant into two groups, one with 17 cm intercoil spacing ICD lead and a second with 21 cm intercoil spacing. Patients were also randomized to begin DFT testing with either SVC ON or OFF. DFT testing was performed at implant using a Binary Search Method with the right ventricular (RV) leads placed in the RV apex.
Results: DFT peak voltage (423±120 V vs. 438±118 V, p=0.045) and shock impedance (41±7 Ω vs. 60±13Ω, p<0.0001) were significantly reduced with the SVC coil ON. There was no significant reduction in the delivered energy (8.8±5.1 J vs. 8.7±4.8, p=0.8) and a trend towards a reduction of stored energy (9.8±5.6 J vs. 10.2±5.8 J, p=0.073) with SVC ON. Subgroup analysis showed that adding the SVC coil reduced the stored energy DFT only when the single RV coil resistance was ≥ 60Ω. The mean benefit was 1.6 J (p =0.0015). In contrast, intercoil distance had no significant effect on DFTs (Table⇓).
Conclusions: The addition of an SVC coil to the shocking pathway reduces the voltage DFTs while not affecting delivered energy requirements. Impedance adjusted waveform durations may be particularly helpful for high impedance pathways. However, intercoil distance had no significant effect on defibrillation parameters.