title: A second defibrillator chest patch electrode will increase implantation rates for nonthoracotomy defibrillators.
abstract: Nonthoracotomy defibrillator systems can be implanted with a lower morbidity and mortality, compared to epicardial systems. However, implantation may be unsuccessful in up to 15% of patients, using a monophasic waveform. It was the purpose of this study to prospectively examine the efficacy of a second chest patch electrode in a nonthoracotomy defibrillator system. Fourteen patients (mean age 62 +/- 11 years, ejection fraction = 0.29 +/- 0.12) with elevated defibrillation thresholds, defined as > or = 24 J, were studied. The initial lead system consisted of a right ventricular electrode (cathode), a left innominate vein, and subscapular chest patch electrode (anodes). If the initial defibrillation threshold was > or = 24 J, a second chest patch electrode was added. This was placed subcutaneously in the anterior chest (8 cases), or submuscularly in the subscapular space (6 cases). This resulted in a decrease in the system impedance at the defibrillation threshold, from 72.3 +/- 13.3 omega to 52.2 +/- 8.6 omega. Additionally, the defibrillation threshold decreased from > or = 24 J, with a single patch, to 16.6 +/- 2.8 J with two patches. These changes were associated with successful implantation of a nonthoracotomy defibrillator system in all cases. In conclusion, the addition of a second chest patch electrode (using a subscapular approach) will result in lower defibrillation thresholds in patients with high defibrillation thresholds, and will subsequently increase implantation rates for nonthoracotomy defibrillators.
authors.affiliation: Department of Medicine, Georgetown University Medical Center, Washington, D.C., USA.
authors.forename: A J
authors.initials: AJ
authors.lastname: Solomon
authors.forename: J F
authors.initials: JF
authors.lastname: Swartz
authors.forename: D J
authors.initials: DJ
authors.lastname: Rodak
authors.forename: H J
authors.initials: HJ
authors.lastname: Moore
authors.forename: R L
authors.initials: RL
authors.lastname: Hannan
authors.forename: C M
authors.initials: CM
authors.lastname: Tracy
authors.forename: R D
authors.initials: RD
authors.lastname: Fletcher
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017147:Defibrillators, Implantable; D004554:Electric Countershock / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods*; D004566:Electrodes; D006801:Humans; D008875:Middle Aged