ELECTROGRAM SIGNALS RECORDED FROM ACUTE AND CHRONIC PACEMAKER IMPLANTATION SITES IN PACEMAKER PATIENTS

Electrogram signals recorded from typical pacemaker implantation sites may be useful for a variety of pacemaker system functions including p acemaker follow-up, atrial and ventricular sensing (event detection), and triggered electrogram storage. We quantified the electrical charac teristics of pacemaker pocket electrograms using a subcutaneous electr ode array (SEA) in a population of 48 patients undergoing initial or r eplacement pacemaker implantation. SEA recorded intrinsic R wave ampli tudes measured peak to peak averaged 118 mu V and 65 mu V for the two recorded SEA electrograms and were significantly different (P < 0.001) ; paced R wave amplitudes averaged 180 mu V and 110 mu V. P wave ampli tudes averaged 39 mu V and 26 mu V. No statistically significant diffe rence in amplitudes were observed between acute versus chronic pacemak er pocket or indication for pacing (AV block, sick sinus syndrome). Si gnal to noise ratios, using R wave amplitude as signal, were lower in the SEA electrogram on average (11 dB) compared to the intracardiac el ectrogram (27 dB), but sufficient for diagnostic assessment. R wave/P wave ratios for SEA signals were lower than surface and intracardiac v alues 3.1 and 2.7 compared to a range of 6.2-9.8, indicating a relativ e enhancement of P waves to R waves in SEA signals. In summary, SEA el ectrograms are of sufficient amplitude and signal quality (signal to n oise ratio) to hold promise for future implantable device features suc h as electrogram telemetry, enhanced sensing, and diagnostic data stor age.