Effect of implantable cardioverter/defibrillator lead placement in the right ventricle on defibrillation energy requirements. A combined experimentaland clinical study

Objectives: The effect of implantable cardioverter/defibrillator (ICD) lead placement in the right ventricle (RV) on defibrillation efficacy has not b een thoroughly investigated. Therefore, the goal of this combined experimen tal and clinical study was to evaluate the effect of a septal and a non-sep tal position of the right ventricular endocardial spring lead on defibrilla tion energy. Methods: In 12 isoflurane-anaesthetized swine and subsequently in 8 patients who underwent ICD implantation, two different positions of t he distal spring lead in the RV were investigated in randomized order: non- septal position (free wall of the RV) and septal position (interventricular septum). For each position, separate 50% probability determinations of ene rgy (E-50). peak voltage (V-50) and peak current (A(50)) were calculated us ing the three reversal up/down defibrillation procedure. The E-50, V-50, A( 50) and impedance (I) were averaged and compared using the two-sided t-test for paired samples. Results: Both the experimental study and the clinical study demonstrated that placing the distal defibrillation lead near to the septum rather than near to the ventricular free wall resulted both in the s wine and in the patients in significantly lower E-50 -31.6%/ - 37.1%, V-50- 16.1%/-20.9% and A(50) -10.0%/ - 24.2%, respectively. Defibrillation impeda nces were significantly reduced only in the experimental study. Conclusions : Defibrillation efficacy depends on the position of the distal spring elec trode in the RV. A septal position significantly reduces the energy require ments compared to a non-septal position. The decrease in energy requirement s might be explained by an increase in current flow through the septum and the posterolateral wall of the left ventricle. (C) 1998 Elsevier Science B. V. All rights reserved.