Intraoperative comparison of a subthreshold test pulse with the standard high-energy shock approach for the measurement of defibrillation lead impedance.
There are two methods to measure shocking lead impedance: delivery of high-energy shocks that require patient sedation, and the painless measurement of impedance from subthreshold test pulses. The aim of this study was to compare the two methods.


METHODS
The study included 131 patients implanted with a standard DR (n = 71) or VR (n = 60) ICD connected to either single-coil (n = 39) or dual-coil (n = 92) defibrillation leads. The noninvasive high-energy impedance test was done using a 17 J shock after induction of ventricular tachyarrhythmias and compared to a 0.4 microJ test pulse used by the ICD for the subthreshold measurements.


RESULTS
Defibrillation lead impedance measurements were not significantly different between patients with the same shocking vector configuration. In patients with a single-coil defibrillation lead the impedance was 62 +/- 9 Omega with the high-energy shock and 62 +/- 8 Omega with the subthreshold test pulses (P = 0.13). Patients with a dual-coil configuration recorded average impedances of 40 +/- 5 Omega from both tests (P = 0.44). While there was no difference in values recorded within each lead configuration, there was a significant difference in impedance between the single-coil and the dual-coil patient groups (P = 0.001).


CONCLUSIONS
There was no significant difference between shocking lead impedances measured with the high-energy shock or the subthreshold test pulses. This offers the possibility of noninvasive, low-energy serial measurements of shocking lead impedance at follow-up visits and removing the need for sedation.
Schuchert
Andreas
A
University-Hospital Hamburg-Eppendorf, Germany. schuchert@uke.uni-hamburg.de
Winter
Joachim
J
Binner
Ludwig
L
Kühl
Martin
M
Meinertz
Thomas
T
D017147:Defibrillators, Implantable / Q000592:standards*; D004554:Electric Countershock / Q000592:standards*; D017097:Electric Impedance; D004566:Electrodes / Q000592:standards; D004869:Equipment Safety; D005060:Europe; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D011446:Prospective Studies; D017180:Tachycardia, Ventricular / Q000628:therapy*