Clinical predictors of defibrillation thresholds with an active pectoral pulse generator lead system

Active pectoral pulse generators are used routinely for initial ICD placement because they reduce DFTs and simplify the implantation procedure. Despite the common use of these systems, little is known regarding the clinical predictors of defibrillation efficacy with active pulse generator lead configurations. Such predictors would be helpful to identify patients likely to require higher output devices or more complicated implantations. This was a prospective evaluation of DFT using a uniform testing protocol in 102 consecutive patients with an active pectoral can and dual coil transvenous lead. For each patient, the DFT was measured with a step-down protocol. In addition, 34 parameters were assessed including standard clinical echocardiographic and radiographic measures. Multivariate stepwise regression analysis was performed to identify independent predictors of the DFT. The mean DFT was 9.3 +/- 4.6 J and 93% (95/102) of patients had a DFT < or = 15 J. The QRS duration, interventricular septum thickness, left ventricular mass, and mass index were significant but weak (R < 0.3) univariate predictors of DFT. The left ventricular mass was the only independent predictor by multivariate analysis, but this parameter accounted for < 5% of the variability of DFT measured (adjusted R2 = 0.047, P = 0.017). The authors concluded that an acceptable DFT (< 15 J) is observed in > 90% of patients with this dual coil and active pectoral can lead system. Clinical factors are of limited use for predicting DFTs and identifying those patients who will have high thresholds.