True bipolar defibrillator leads have increased sensing latency and threshold compared with the integrated bipolar configuration

True Bipolar Sensing Latency. Background: Dual-coil implantable defibrillator (ICD) leads with true bipolar pacing and sensing (quadripolar leads) have been introduced to provide improved sensing characteristics without sacrificing defibrillation efficacy. Electrode configuration has been shown to have little effect on the amplitude or slew rate of the intracardiac electrogram, but does have an effect on the duration of the sensed electrogram. Closer spacing of the electrodes and smaller surface area of the anode may, therefore, result in a different latency of sensing relative to the onset of the QRS complex. Methods: We tested the difference in ventricular sensing latency between integrated bipolar and true bipolar electrode configurations in 40 patients undergoing ICD implantation for standard indications (Medtronic Sprint Quattro lead in 26 and St. Jude Riata in 16). In addition, we compared R wave amplitude, pacing threshold, impedance, and slew rate. Results: Sensing latency was significantly longer in the true bipolar configuration (Medtronic Sprint Quattro 45.2 +/- 14.7 msec in the true bipolar configuration, vs 37.4 +/- 18.2 msec in the integrated bipolar configuration, and St. Jude Riata, 43.5 +/- 9.8 msec true bipolar, vs 33.8 +/- 10.1 msec integrated bipolar, P < 0.01). There was no difference in R wave amplitude or slew rate. Pacing threshold and impedance were also greater in the true bipolar configuration than in the integrated bipolar configuration. Conclusion: The true bipolar configuration has a longer sensing latency than the integrated bipolar configuration. In some patients, this may require a longer programmed AV delay to avoid ventricular pseudofusion.