Clinical predictors of defibrillation energy requirements in patients treated with a nonthoracotomy defibrillator system

Many factors can influence defibrillation energy requirements (DER) in patients with a nonthoracotomy defibrillator. No large studies, however, have correlated clinical characteristics with the DER. In this study, 124 patients underwent the same DER protocol with the identical biphasic waveform, nonthoracotomy lead system, and lead configuration. These patients were 63 ± 12 years old (mean ± SD); 99 were men; the ejection fraction was 0.32 ± 0.13 and 36 were taking an antiarrhythmic medication. New York Heart Association congestive heart failure class I was present in 28, class II in 70, and class III in 26 patients. Male sex (454 ± 94 V vs 406 ± 91 V for female sex) was associated with a significantly higher DER (p = 0.02) and an increased risk of a DER>550 V (p = 0.047). No other clinical variable was associated with the DER or a DEr>550 V. In conclusion, women tend to have lower DERs than men.