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Effects of Initial Polarity on Defibrillation Threshold with Biphasic Pulses
Author(s) -
NATALE ANDREA,
SRA JASBIR,
DHALA ANWER,
JAZAYERI MOHAMMAD,
DESHPANDE SANJAY,
AXTELL KATHI,
AKHTAR MASOOD
Publication year - 1995
Publication title -
pacing and clinical electrophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.686
H-Index - 101
eISSN - 1540-8159
pISSN - 0147-8389
DOI - 10.1111/j.1540-8159.1995.tb03837.x
Subject(s) - defibrillation , defibrillation threshold , medicine , cathode , pulse (music) , anode , ventricular fibrillation , polarity (international relations) , electromagnetic coil , cardiology , lead (geology) , fibrillation , electrode , biomedical engineering , nuclear magnetic resonance , voltage , electrical engineering , atrial fibrillation , chemistry , physics , cell , biochemistry , geomorphology , engineering , geology
Background : Previous studies have shown that the polarity of epicardial patches significantly affects the defibrillation efficacy of monophasic shocks. Howevar, whether this improvement can he extended to different pulsing methods and lead systems, such as biphasic shocks using endocardial defibrillating electrodes, is unknown. Methods : Twenty consecutive patients undergoing testing and permanent implant using an Endotak lead system with a biphasic device were included in the study. In each patient the defibrillation threshold was determined delivering biphasic pulses with the distal coil as the cathode and the proximal coil as the anode during the positive phase and with the polarity reversed. The initial electrode polarity tested was chosen randomly. The defibrillation threshold was defined as the lowest pulse amplitude that effectively terminated ventricular fibrillation induced with 60‐H z alternating current. For each biphasic pulse peak voltage, pulse duration, resistance, and stored energy were recorded. Results : Of the 20 patients, 12 (60%) had lower defibrillation threshold when the proximal coil was negative, whereas only 2 patients had a lower defibrillation threshold when the distal coil was negative. In four patients a subcutaneous patch would have been required if only the biphasic pulse with the distal coil as negative had been tested. The mean stored defibrillation threshold energy was lower with the configuration using the proximal coil as cathode (16.3 ±8.8 J vs 21.5 ±11 J; P < 0.01). Conclusion : Change in the initial polarity of biphasic shocks may influence defibrillation efficacy and should, therefore, be assessed in each patient to achieve a more satisfactory safety margin and minimize the use of more invasive lead configurations.