Detection of ventricular fibrillation by transvenous defibrillating leads: Integrated versus dedicated bipolar sensing

Introduction: Dedicated bipolar sensing has been suggested to be safer than integrated bipolar sensing due to an increased incidence of failure to redetect ventricular fibrillation after an unsuccessful shock with leads that use integrated bipolar sensing. We compared sensing characteristics during ventricular fibrillation of simultaneously recorded dedicated and integrated bipolar electrograms. Methods and Results: Thirty patients undergoing transvenous defibrillator implantation with a Transvene lead were studied, Simultaneous recordings were made from the dedicated bipole and the integrated bipole from the distal tip to the coil (interelectrode distance 18.3 mm). The mean detection time and number of undetected beats for the initial episode of ventricular fibrillation were 2804 +/- 569 msec and 0.9 +/- 0.8 using the dedicated recordings and 2938 +/- 546 msec and 1.4 +/- 1.1 (P = 0.026) using the integrated recordings. The mean redetection times and number of undetected beats following a failed first shock (n = 13) were 2468 +/- 225 msec and 0.8 +/- 1.1 for the dedicated recordings and 3042 +/- 498 msec (P < 0.0003) and 4,2 +/- 4.2 (P < 0.005) for the integrated recordings. Frequency analysis of the ventricular fibrillation electrograms demonstrated that the signal energy in the dedicated electrograms was significantly greater than the energy in the integrated electrograms (P < 0.0001). There was a significant negative relationship between detection times and the ventricular fibrillation signal energy, There was no independent effect of recording type (dedicated versus integrated). Conclusion: There are only minor differences in detection/redetection of ventricular fibrillation between dedicated and integrated (with tip to coil spacing of 18.3 mm) recording configurations, Detection times during ventricular fibrillation are related to the signal variance or energy recorded, Differences in the sensing performance of the two recording configurations can be explained by the differences in signal energy between the dedicated and integrated recordings that occur during ventricular fibrillation.