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

January 24-31, 1998
Marilleva, Trento, Italy

RT-24

Significant reduction of atrial floating pacing capture thresholds using a conventional monophasic impulse and a novel pacing electrode configuration.
First results

W.M. Hartung, D. Hartung, A. Auricchio, C. Geller, A. Goette, H.-D. Esperer, S. Hobrack, H. Klein.
University Hospital Magdeburg, Department of Internal Medicine, Division of Cardiology, Magdeburg, Germany

Introduction

Sequential atrio-ventricular pacing is considered to be the best pacing mode available in the absence of permanent atrial arrhythmias. DDD pacemakers however require implantation of two separate leads. The idea of a single lead AV-sequential pacemaker system is not new, and AV synchrony can be achieved with such a system. Atrial signals are recorded via two sensing electrodes along the axis of the single floating lead¹. Studies with the first single-lead-DDD-pacemaker were reported by Wainright et al in 1983². The "Crown of Thorns" electrode had three radial spines which projected from the main shaft to the atrial myocardium. Although atrial pacing was possible, complications prevented it from becoming generally used. Therefore, a new concept was developed to stimulate the atrium by means of an electrical field via floating electrodes on a lead using conventional bipolar or unipolar impulse configuration^3,4. Results, however, were disappointing because of unacceptably high capture thresholds. Therefore, we developed a concept of using two different overlapping electrical fields⁵. "Overlapping Biphasic Impulse" ("OLBI")-stimulation creates a partial increase in electrical field density, thereby reducing atrial capture thresholds. A significant difference between atrial and phrenic nerve capture thresholds was achieved⁶. However, it requiers relatively sophisticated technology.

Cardiac defibrillation has tought us that a three electrode configuration resulting in splitting of the electrical field causes a reduction of the DFT^7,8. Our hypothesis then was: splitting of the electrical field with a single monophasic impulse generated between three electrodes significantly reduces atrial capture thresholds and we called this bidirectional monophasic impulse stimulation or BIMOS-stimulation. The purpose of our study was to test this novel pacing configuration comparing BIMOS thresholds with conventional unipolar and bipolar pacing.