Unipolar and bipolar right atrial appendage electrodes: comparison of sensing characteristics

To optimize atrial sensing and reject far-field signals (i.e., ventricular potentials seen in the atrium), the atrial amplitudes of electrograms (EGMs) should be as high as possible and the ventricular amplitudes as low as possible. To compare clinical sensing results obtained with unipolar and bipolar electrodes, endocardial EGMs were recorded on a high-speed multichannel recorder with a paper speed of 200 mm/second and frequency cutoffs at 0.1 and 2,000 Hz. Forty acute unipolar and 18 acute bipolar electrodes (in different patients), three matched pairs of unipolar and bipolar electrodes, and seven coronary sinus electrodes were measured. Unipolar and bipolar right atrial appendage (RAA) electrode EGMs were compared for 1) amplitude of EGM, 2) slew rate (dv/dt); and 3) amplitude of the ventricular EGM as measured through the RAA electrode. Unipolar RAA EGMs were compared with unipolar coronary sinus EGMs. Three bipolar leads were measured as unipolar and bipolar simultaneously. Bipolar atrial EGMs had equal amplitudes (unipolar, 4.2 +/- 2.1 mV, versus bipolar, 5.9 +/- 2.5; NS), higher slew rates (unipolar, 2.6 +/- 1.6 V/second, versus bipolar, 4.4 +/- 2.1; P less than 0.005), and lower ventricular (far-field) amplitudes (unipolar, 1.1 +/- 1.1 mV, versus bipolar, 0.7 +/- 0.6; P less than 0.02) when compared with unipolar RAA electrodes. This observation was confirmed in the measurement of the matched pairs atrial/ventricular amplitude ratio (unipolar, 4.7 +/- 2.2, versus bipolar, 8.7 +/- 2.0; P less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)