Current Density Distribution by Ring and Diagonally Arranged Half‐Ring Electrodes in Bipolar and Overlapping Biphasic Impulse Stimulation

Background: We have studied the acute and long‐term efficacy of overlapping biphasic impulse (OLBI) stimulation for atrial pacing with VDD pacemakers and demonstrated the feasibility of DDD pacing in OLBI with diagonally arranged half‐ring (Half‐Ring) electrodes. We made two three‐dimensional computational analysis models to verify our clinical studies. Methods and Results: Model I was composed of a heart, a pacemaker, and a human body. Model II was a cube with dimensions of 20 by 20 by 20 mm quarried from Model I for the detailed study of current density distributions. Laplace's equation was solved using the finite element method and the current density J was calculated. For Model I, the distal and proximal voltages were ?10 V, 0 V in bipolar and ?5 V, +5 V in OLBI, using Ring electrodes. In Model II, the actual measurements of electrode impedances obtained from the clinical study (1,180 Ω for Ring and 630 Ω for Half‐Ring) were added to the analysis conditions. Model I showed that OLBI produced more concentrated current density distributions than those by bipolar. According to Model II, at the atrial myocardium position current density produced by Half‐Ring was larger than that by Ring electrodes, 70 μA/mm² versus 30 μA/mm² in OLBI configuration. It also indicated that even if electrode impedances were equal between Half‐Ring and Ring electrodes, the maximum current density produced by Half‐Ring would be greater than that by Ring electrodes. Conclusions: It was considered that OLBI configuration with Half‐Ring electrodes provides more effective current density distributions. (PACE 2010; 33:1063–1073)