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 ≥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.