Comparison of spontaneous atrial fibrillation electrogram potentials with the P-wave electrogram amplitude in dual chamber pacing with unipolar atrial sensing

Abstract

Aims Although bipolar sensing is recommended and desirable in patients with dual chamber pacemakers (DDD) and intermittent atrial fibrillation (AF) it is a clinical reality that some patients who are given unipolar atrial leads without a prior history of AF may develop intermittent AF during follow-up. It was therefore the purpose of this prospective study to compare the electrogram amplitudes of AF potentials with sinus rhythm P-wave potentials as a relevant factor for appropriate mode switching in dual chamber pacing with unipolar atrial sensing. Methods and Results Forty-two patients with dual chamber pacemakers, unipolar atrial leads and intermittent AF were studied. Aside from measuring the P-wave potential, it was possible in 14 patients (4 women, 10 men; mean age: 61·8 (±13·3) years) additionally to document spontaneous AF electrogram potentials using pacemaker telemetry. A prospective survey study was performed including a 6 month follow-up period with an outpatient clinic visit every 2-3 weeks. The mean P-wave electrogram amplitude was 3·4 (±1·8)mV (range: 1·4-7·4) compared with the mean amplitude during AF of 2·04 (±1·26)mV (range: 0·8-5·2mV) indicating a significant attenuation of 40% during AF (P<0·0001). A linear correlation regression analysis revealed that there was a significant correlation between the P-wave and the AF amplitude (P<0·0001), with a correlation coefficient of r=0·867. Conclusion Once it is known that a substantial reduction exists in AF electrogram amplitude, compared with the P wave electrogram potential, an estimate can be made of whether AF potentials will be sensed, if the programming of atrial sensitivity is congruent with the P-wave characteristics and the presence or absence of myopotential triggering. © 2000 The European Society of Cardiology.