Conduction Disturbances Caused by High Current Density Electric Fields

• Published in: Circulation research 1990-05, Vol.66 (5), p.1190-1203
• Main Authors: Yabe, Seitaro, Smith, William M, Daubert, James P, Wolf, Patrick D, Rollins, Dennis L, Ideker, Raymond E
• Format: Article
• Language: English
• Subjects: Animals; arrhythmia; Biological and medical sciences; Cardiac Pacing, Artificial; Diseases of the cardiovascular system; Dogs; electric fields; Electroshock; Heart Block - etiology; Heart Conduction System - physiology; Medical sciences; membrane current; Radiotherapy. Instrumental treatment. Physiotherapy. Reeducation. Rehabilitation, orthophony, crenotherapy. Diet therapy and various other treatments (general aspects); Time Factors
• ISSN: 0009-7330; 1524-4571
• DOI: 10.1161/01.res.66.5.1190

During internal defibrillation, potential gradients greater than 100 V/cm occur near defibril-lation electrodes. Such strong fields may cause deleterious effects, including arrhythmias. This study determined 1) the effects of such strong fields on the propagation of activation and 2) whether these effects were different for monophasic and biphasic shocks. Voltages and potential gradients during the shock, as well as activation sequences before and after the shock, were mapped from 117 epicardial electrodes placed over a 3×3-cm area on the right ventricle in six dogs. Pacing at a cycle length of 350 msec was given from a long narrow electrode on the right side of the mapped area to generate parallel activation isochrones. A monophasic shock, 10 msec in duration, or a biphasic shock with both phases 5 msec in duration was delivered 300 msec after the last paced stimulus via a mesh electrode on the left side of the mapped area as the cathode, with the anode on the right atrium. Shocks of 70–850 V were given, and the potential gradient and current density at each recording electrode were calculated from the measured potentials and fiber orientation by using a finite element method. Pacing was resumed 200 msec after the shock, and activation sequences were mapped for up to 5 minutes. Potential gradients ranged from 1 to 189 V/cm with high fields on the left side and low fields on the right side of the mapped area. Where the potential gradient was weak, the first activation sequence after the shock was similar to that before the shock, but activation blocked without conducting into areas where the gradient was greater than 64±4 (mean±tSD) V/cm for monophasic and greater than 71±6 V/cm for biphasic shocks. These values are significantly different (p