Sensing characteristics of unipolar and bipolar orthogonal floating atrial electrodes: morphology and spectral analysis.

We investigated wave morphology and spectral energy distributions of signals picked up by floating atrial unipolar and bipolar orthogonal sensing electrodes. Our data show that atrial P and QRS waves from unipolar floating electrodes are comparable. On the other hand, atrial P and QRS waves from bipolar orthogonal floating electrodes are significantly different. Even at high and mid right atrial locations, QRS waves are either absent or much smaller in amplitude and lower in frequency content than P waves. We conclude that the bipolar orthogonal floating atrial electrode is superior to the unipolar one for sensing due to its P to QRS wave discriminating power, which makes complex input filters or algorithms unnecessary. Our data support the idea that physiologic pacing with a VDD or VAT pacemaker is possible using a single pass lead.