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

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: 0.8-5.2 mV) 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 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.