13th International Congress
THE "NEW FRONTIERS"
OF ARRHYTHMIAS 1998

January 24-31, 1998
Marilleva, Trento, Italy

RT-26

Effects of changing pacing pulse polarity, magnitude, and morphology on driven beats

Morton M. Mower.
The Johns Hopkins University School of Medicine, Baltimore, USA

Introduction

Standard monophasic cathodal pulses, 1/2 to 1 msec, and approximately 2 volts have long been used for pacing the heart because they do work, are energy efficient, and there was no obvious reason to believe that the use of some other kind of pulse might be beneficial^1,2. Also, there was an underlying feeling that once heart muscle had been stimulated, excitation and contraction probably ensued in a fairly stereotypical fashion.

During pacing for heart failure clinical studies^3-5 using a widely separated bipolar lead system (each leg of which was used to pace separate sites on the myocardium), it appeared that the impulse arising from the anodal electrode might have different conduction and excitation properties from that arising from the cathode. Accordingly, a direct examination of these properties was made in Langendorff-perfused rabbit hearts, and the global effects measured by gated-MRI wall tension images⁶ obtained in whole canine preparations.