True bipolar and integrated bipolar sensing and detection by implantable defibrillators.

INTRODUCTION

Sensing and detection can be performed in true bipolar or integrated bipolar configuration by implantable defibrillators. New Medtronic generators (Medtronic Inc., Minneapolis, MN, USA) can be configured so that the sensing function of the device can be either true bipolar or integrated bipolar. We compared the sinus rhythm R-wave amplitude and detection time of induced ventricular fibrillation (VF) at implant (acute phase), and sinus rhythm R-wave amplitude 3 months or more after the implant (chronic phase) in these two configurations.

METHODS

Twenty-eight patients were studied in the acute phase, and a subgroup of 15 patients was tested in the chronic phase. The generators were Medtronic model numbers D224VRC, D224TRK, D224DRG, D284VRC, D284TRK, and D284DRG. The leads were Medtronic 6947 or 6935. Sensing was evaluated by recording the electrogram and measuring the R-wave peak-to-peak amplitude in the two configurations. Detection was evaluated by measuring the detection time in the two configurations in two consecutive inductions. The detection time was measured on programmer paper from the marker of the T shock to the marker of VF.

RESULTS

The acute-phase values were: R wave in true bipolar configuration 13.9 ± 7.1 mV, R wave in integrated bipolar configuration 13.6 ± 6.9 mV (p = 0.38),VF detection time in true bipolar configuration 3.12 ± 0.39 seconds, and VF detection time in integrated bipolar configuration 3.17 ± 0.39 seconds (p = 0.52).

CONCLUSIONS

Sensing and detection at implant were not significantly different between the true bipolar and the integrated bipolar configurations for the tested leads and generators.