The effect of dofetilide on ventricular defibrillation thresholds.
INTRODUCTION
High defibrillation threshold (DFT) with an inadequate defibrillation safety margin remains an infrequent but troubling problem associated with defibrillator implantation. Dofetilide is a selective class III antiarrhythmic drug that reduces DFTs in a canine model. We hypothesized that dofetilide would reduce DFTs in humans, obviating the need for complex lead systems.


METHODS AND RESULTS
Sixteen consecutive patients with DFTs > or =20 J delivered energy at implant-received dofetilide therapy and underwent follow-up DFT testing acutely following drug loading and/or chronically (128 +/- 94 days). Amiodarone was discontinued in four patients at implantation. With dofetilide, DFTs decreased from 28 +/- 4 J to 19 +/- 7 J (P < 0.0001), resulting in a safety margin of 15 +/- 8 J for the implanted devices. Five patients subsequently had spontaneous arrhythmias terminated successfully with shocks.


CONCLUSION
Dofetilide reduces DFTs sufficiently to prevent the need for more complex lead systems. This strategy should be considered when an inadequate defibrillation safety margin is present.