Differential Bipolar Sensing of a Dual Chamber Pacemaker

Abstract

Differential bipolar sensing was evaluated in 10 consecutive patients with symptomatic heart block managed with dual chamber pacing. During pacemaker implantation atrial and ventricular electrograms were recorded using unipolar (UP) and differential bipolar (DBP) sensing amplifiers. The mean peak-to-peak amplitudes of the UP and DBP atrial electrograms were 3.3 +/- 1.2 mV and 4.2 +/- 1.2 mV, respectively. The difference was statistically significant (p less than 0.05). The mean peak-to-peak amplitudes of the ventricular electrograms were, respectively, 6.8 +/- 1.5 mV and 7.5 +/- 1.4 mV (p less than 0.01). Within 6 weeks after pacemaker implantation, patients visited the outpatient clinic. Isometric exercise tests were performed during UP and DBP sensing of the pacing system. Myopotential sensing in the ventricle occurred in nine patients during UP sensing and in none of the patients during DBP sensing (p less than 0.01) at a sensitivity setting of 0.5 mV. In addition, chest wall stimulation was performed to assess the effects of far-field signals on the ventricular sensing circuit of the pulse generator. Chest wall stimuli inhibited ventricular output during UP sensing in all 10 patients, whereas during DBP sensing inhibition of the ventricular channel occurred in three patients and then only at high output (greater than 8 V) settings. The susceptibility of the pacing system to crosstalk was also determined. However, neither during UP sensing nor during DBP sensing could cross-stimulation or cross-inhibition be demonstrated. In conclusion, DBP sensing is superior to UP sensing in terms of myopotential and far-field sensing.(ABSTRACT TRUNCATED AT 250 WORDS)