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(Circulation. 1997;96:267-273.)
© 1997 American Heart Association, Inc.

Articles

A Population-Based Method for the Estimation of Defibrillation Energy Requirements in Humans

Assessment of Time-Dependent Effects With a Transvenous Defibrillation System

David Newman, MD; Aiala Barr, PhD; Mary Greene, RN, MSc; David Martin, MD; Miney Ham, MSc; Sally Thorne, RN; ; Paul Dorian, MD

From the Division of Cardiology (D.N., A.B., M.G., M.H., P.D.), St. Michael's Hospital, University of Toronto, Telectronics Pacing Systems Inc (S.T.), Denver, Colo, COR Medical (S.T.), Toronto, Canada, and the Lahey-Hitchcock Medical Center (D.M.), Burlington, Mass.

Correspondence to Dr David Newman, MD, St. Michael's Hospital, Division of Cardiology, 30 Bond St, Toronto, ON, Canada, M5B 1W8. E-mail newmand{at}SMH.Toronto.on.ca

Background A weighted logistic regression analysis was developed to allow pooling of patient data for the study of the stability of defibrillation energy requirements with a new nonthoracotomy lead defibrillation system.

Methods and Results One hundred twenty patients were prospectively studied with a single-model nonthoracotomy implantable cardioverter defibrillator (ICD) system at the time of implant and at 3 months. The pooled data of all shocks delivered to all patients were fitted to a logistic function to construct a defibrillation voltage/energy dose-response relationship. The crude logit curve was weighted in quartiles according to the average shock energy delivered per patient. Shocks at implant (n=802; 6.6±2.5 shocks/patient) and follow-up (n=292; 2.4±1.2 shocks/patient) were analyzed. The modeled voltage/energy required for 50% successful defibrillation (95% CI) in the pooled data was 367 V (273, 461) and 9.8 J (6.7, 12.9) at implant and 338 V (264, 412) and 10.5 J (8, 13.0) at follow-up. The conventional measure of lowest successful voltage/energy (95% CI) was 430 V (411, 449) and 12.1 J (11, 13.2) at implant and 415 V (391, 439) and 11.3 J (10, 12.6) at follow-up. There were no statistically significant differences between implant and follow-up energy requirements with either method.

Conclusions The nonthoracotomy lead system used in this study demonstrated stability of defibrillation energy requirements at implant and 3-month follow-up. A new technique for the estimation of the defibrillation energy dose-response relationship was derived by using a weighted logistic regression analysis.

Key Words: defibrillation • modeling, mathematical • electrophysiology • arrhythmia • defibrillator, implantable