A comparison of peak QRS potential detection using unipolar and bipolar cardiac pacemaker lead systems

Abstract The use of bipolar lead systems with demand cardiac pacemakers has been criticized because the small interelectrode distance was thought to decrease sensitivity to cardiac electrical potentials. This study was done to determine if the reduced interelectrode distance inherent in bipolar systems is a limiting factor with the new small surface area electrodes. Three bipolar electrodes of differing surface areas were placed in the right ventricule of 10 anesthetized dogs. Bipolar sensing was compared with unipolar sensing. The results demonstrated three factors which determine the amplitude of the potentials detected: (1) surface area of the electrode; (2) position of the indifferent ring electrode in the bipolar system; and (3) pacemaker sensing circuit impedance. Electrode surface area was the most important determinant and impedance was the least. No significant peak QRS potential differences were detected when bipolar and unipolar sensing with the newer small surface area electrodes were compared.