A multifilamented electrode in the middle cardiac vein reduces energy requirements for defibrillation in the pig

Objective-To compare the defibrillation efficacy of a novel lead system pla ced in the middle cardiac vein with a conventional non-thoracotomy lead sys tem. Methods-In eight pigs (weighing 35-71 kg), an electrode was advanced transv enously to the right ventricular apex (RV), with the proximal electrode in the superior caval vein (SCV). Middle cardiac vein (MCV) angiography was us ed to delineate the anatomy before a three electrode system (length 2 x 25 mm + 1 x 50 mm) was positioned in the vein. An active housing (AH) electrod e was implanted in the left pectoral region. Ventricular fibrillation was i nduced and biphasic shocks were delivered by an external defibrillator. The defibrillation threshold was measured and the electrode configurations ran domised to: RV --> AH, RV+MCV --> AH, MCV --> AH, and RV --> SCV+AH. Results-For these configurations, mean (SD) defibrillation thresholds were 27.3 (9.6) J, 11.9 (2.9) J, 15.2 (4.3) J, and 21.8 (9.3) J, respectively Bo th electrode configurations incorporating the MCV had defibrillation thresh olds that were significantly less than those observed with the RV --> AH (p < 0.001) and RV --> SCV+AH (p < 0.05) configurations. Necropsy dissection showed that the MCV drained into the coronary sinus at a location close to its orifice (mean distance = 2.7 (2.2) mm). The MCV bifurcated into two mai n branches that drained the right and left ventricles, the left branch bein g the dominant vessel in the majority (6/7) of cases. Conclusions-Placement of specialised defibrillation electrodes within the m iddle cardiac vein provides more effective defibrillation than a convention al tight ventricular lead.