title: Comparison of simultaneous versus sequential defibrillation pulsing techniques using a nonthoracotomy system.
abstract: The defibrillation threshold (DFT) using simultaneous (SIML) versus sequential (SEQ) pathways for shock delivery was compared in 16 patients with an implanted cardioverter defibrillator. All patients had three-lead nonthoracotomy systems (NTL) using a left chest subcutaneous patch, a right ventricular endocardial lead, and a lead in the coronary sinus (n = 5) or superior vena cava (n = 11). The DFT were determined 2-44 days (17 +/- 17 days) after implantation. The DFT was defined as the lowest energy shock that resulted in successful defibrillation. The first pathway tested was SIML in 12 and SEQ in 4 patients with output beginning at or above the intraoperative DFT, routinely 18 J. The second pathway was tested beginning 2-4 J above the DFT of the first tested pathway. All shocks were delivered in 2-4 J decrement or increment steps. The SEQ pathway shocks resulted in a significantly lower DFT than SIML pathway shocks (14 +/- 6 vs 18 +/- 6 J; P < 0.01). There was no difference in the time delay after ventricular fibrillation initiation before shock delivery for the successful defibrillation between SIML versus SEQ pathways (7 +/- 2 secs for both pathways). In 7 of 16 patients, defibrillation using SEQ pathway resulted in a > 5 J lowering of DFT, while only one patient had > 5 J lowering of DFT using SIML shocks (P < 0.05). These results have important implications for selecting the optimal pathway for implantable cardioverter defibrillator therapy with a multilead NTL system.
authors.affiliation: Clinical Cardiac Electrophysiology Laboratory, Hospital of University of Pennsylvania, Philadelphia.
authors.forename: H H
authors.initials: HH
authors.lastname: Hsia
authors.forename: R B
authors.initials: RB
authors.lastname: Kleiman
authors.forename: B T
authors.initials: BT
authors.lastname: Flores
authors.forename: F E
authors.initials: FE
authors.lastname: Marchlinski
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003331:Coronary Vessels; D017147:Defibrillators, Implantable; D004554:Electric Countershock / Q000379:methods*; D004867:Equipment Design; D005260:Female; D006352:Heart Ventricles; D006801:Humans; D008297:Male; D008875:Middle Aged; D017180:Tachycardia, Ventricular / Q000628:therapy; D013908:Thoracotomy; D014683:Vena Cava, Superior; D014693:Ventricular Fibrillation / Q000628:therapy