title: Low-energy transvenous cardioversion defibrillation of atrial tachyarrhythmias in the canine: an assessment of electrode configurations and monophasic pulse sequencing.
abstract: Prevention of recurrent atrial fibrillation and flutter remains a difficult clinical problem. Consequently, development of an easily implantable automatic atrial cardioverter defibrillator is appealing. In this context we have examined the feasibility of intracavitary low-energy shocks delivered via transvenously positioned electrodes for termination of induced atrial tachyarrhythmias in canine models. This study extends these observations with use of single-pathway (5 msec pulse duration) and dual-pathway sequential (5/5 msec, 0.2 msec separation) shocks of varying leading edge voltages (100 to 400 V) in a closed-chest canine talc-pericarditis model. Bipolar 9.5 French electrode catheters (electrode surface areas, 0.62 cm2) were positioned at the superior vena cava-right atrium (SVC-RA) junction (labeled SVC) and right ventricular (RV) apex, with a subcutaneous plate over the chest wall. For single-pathway shocks, overall treatment effectiveness was comparable among the three vectors tested (RV apex to SVC, 35%; RV apex to subcutaneous plate, 17%; and SVC to subcutaneous plate, 35%). Furthermore, there was no evident relationship between leading edge voltage and shock effectiveness. In contrast, although each of the dual-pathway shock vector combinations tested also showed similar overall effectiveness, there was an apparent dose-response effect as leading edge voltage increased. The SVC (common) to RV apex (pulse 1) and subcutaneous plate (pulse 2) achieved 60% effectiveness at 400 V (approximately 4 joules). Thus this study provides additional evidence favoring feasibility of low-energy transvenous atrial cardioversion defibrillation. However, further refinement of energy delivery is essential for the implantable automatic atrial cardioverter defibrillator concept to become clinically accepted.
authors.affiliation: Department of Medicine, University of Minnesota, Minneapolis.
authors.forename: D G
authors.initials: DG
authors.lastname: Benditt
authors.forename: D
authors.initials: D
authors.lastname: Dunbar
authors.forename: J
authors.initials: J
authors.lastname: Fetter
authors.forename: S
authors.initials: S
authors.lastname: Sakaguchi
authors.forename: K G
authors.initials: KG
authors.lastname: Lurie
authors.forename: S W
authors.initials: SW
authors.lastname: Adler
mesh_terms: D000818:Animals; D001281:Atrial Fibrillation / Q000628:therapy*; D001282:Atrial Flutter / Q000628:therapy*; D002304:Cardiac Pacing, Artificial; D017147:Defibrillators, Implantable; D004285:Dogs; D004554:Electric Countershock / Q000379:methods*; D004567:Electrodes, Implanted; D004867:Equipment Design; D005240:Feasibility Studies