A PROSPECTIVE EVALUATION OF 2 DEFIBRILLATION SAFETY MARGIN TECHNIQUESIN PATIENTS WITH LOW DEFIBRILLATION ENERGY-REQUIREMENTS

Low-Energy Defibrillation. Introduction: In patients undergoing defibr illator implantation, an appropriate defibrillation safety margin has been considered to be either 10 J or an energy equal to the defibrilla tion energy requirement. However, a previous-clinical report suggested that a larger safety margin may be required in patients with a low de fibrillation energy requirement. Therefore, the purpose of this prospe ctive study was to compare the defibrillation efficacy of the two safe ty margin techniques in patients with a low defibrillation energy requ irement. Methods and Results: Sixty patients who underwent implantatio n of a defibrillator and who had a low defibrillation energy requireme nt (less than or equal to 6 J) underwent six separate inductions of ve ntricular fibrillation, at least 5 minutes apart, For each of the firs t three inductions of ventricular fibrillation, the first two shocks w ere equal to either the defibrillation energy requirement plus 10 J (1 4.6 +/- 1.0 J), Or to twice the defibrillation energy requirement (9.9 +/- 2.3 J). The alternate technique was used for the subsequent three inductions of ventricular fibrillation. For each induction of ventric ular fibrillation, the first shock success rate was 99.5% +/- 4.3% for shocks using the defibrillation energy requirement plus 10 J, compare d to 95.0% +/- 17.2% for shocks at twice the defibrillation energy req uirement (P = 0.02). The charge time (P < 0.0001) and the total durati on of ventricular fibrillation (P < 0.0001) were each approximately 1 second longer with the defibrillation energy requirement plus 10 J tec hnique. Conclusion: This study is the first to compare prospectively t he defibrillation efficacy of two defibrillation safety margins. In pa tients with a defibrillation energy requirement less than or equal to 6 J, a higher rate of successful defibrillation is achieved with a saf ety margin of 10 J than with a safety margin equal to the defibrillati on energy requirement.