A prospective randomized cross-over comparison of mono- and biphasic defibrillation using nonthoracotomy lead configurations in humans.

INTRODUCTION

For current implantable defibrillators, the nonthoracotomy approach to implantation fails in a substantial number of patients. In a prospective randomized cross-over study the defibrillation efficacy of a standard monophasic and a new biphasic waveform was compared for different lead configurations.

METHODS AND RESULTS

Intraoperatively, in 79 patients receiving nonthoracotomy defibrillation leads, the defibrillation threshold was determined in the initial lead configuration for the mono- and biphasic waveform. In each patient, both waveforms were used alternately with declining energies (20, 15, 10, 5 J) until failure of defibrillation occurred. Three different initial lead configurations were tested in different, consecutive, nonrandomized patients using a bipolar endocardial defibrillation lead alone (A; n = 36) or in combination with a subcutaneous defibrillation patch (B; n = 24) or array (C; n = 19) lead. The lowest successful defibrillation energy with the biphasic waveform was less than, equal to, or higher than with the monophasic waveform in 64%, 28%, and 8% of patients, respectively, and on average significantly lower with the biphasic waveform for all three lead configurations (A: 11.3 +/- 4.4 J vs 14.5 +/- 4.5 J; B: 9.7 +/- 4.7 J vs 15.1 +/- 4.5 J; C: 7.9 +/- 4.5 J vs 12.4 +/- 4.9 J). Defibrillation efficacy at 20 J was significantly improved by the biphasic waveform (91% vs 76%).

CONCLUSION

In combination with nonthoracotomy defibrillation leads, the biphasic waveform of a new implantable cardioverter defibrillator showed superior defibrillation efficacy in comparison to the standard monophasic waveform. Defibrillation thresholds were improved for lead systems with and without a subcutaneous patch or array lead.