Comparison of bipolar and integrated sensing for redetection of ventricular fibrillation

Background Implantable cardioverter-defibrillation function is critically d ependent on reliable sensing of intracordiac signals. Lead systems that use integrated sensing, in which the distal shocking coil is part of both the sensing and shocking pathways, may be prone to undersensing of ventricular fibrillation, especially during redetection after a failed first shock. To assess the effect of endocardial lead system on redetection, we compared a dedicated rate-sensing lead and 2 generations of integrated sensing defibri llator leads with a uniform testing algorithm and pulse generator. Methods The study group consisted of 72 patients when implantable cardiover ier-defibrillator implatation. Three transvenous rate-sensing leads were ev aluated: a standard pacing lead, incorporating true bipolar sensing without ventricular coils, or an integrated shocking and sensing lead (Endotak C) with either 6-mm (60 series) or 12-mm (70 series) spacing between the sensi ng tip and shocking coil. Redetection was assessed from a failed first shoc k lust below defibrillation threshold. Results Compared with the dedicated bipolar lead, redetection was prolonged with the 60 series lead (8.3 +/- 3.6 vs 6.6 +/- 2.3 seconds, P = .04). Mor eover, prolonged redetection (>8 seconds) was observed in 41% of patients w ith 60 series leads compared with only 11% with dedicated bipolar leads (P < .01). No significant effects on redetection were noted with an integrated lead with greater spacing between the tip and coil (70 series). Conclusions Delayed redetection is frequently noted with an integrated lead with close spacing between the tip and coil. Detailed evaluation of detect ion and redetection of these leads should be performed at the time of pulse generator replacement.