Time trends in the intracardiac potential recorded by pacemaker telemetry:Comparison between steroid-eluting small area electrodes

We assessed the time course of electrograms sensed both in the atrium and v entricle by two different steroid-eluting electrodes: Medtronic Capsure SP (with an area of 5.5 mm(2)) and Z (with an area of 2.2 mm(2)). We considere d 68 unipolar electrodes: 31 atrial (19 Capsure SP 4523 and 12 Capsure Z 45 33) and 37 ventricular (24 Capsure SP 4023 and 23 Capsure Z 4033) implanted in 47 consecutive patients (30 men and 27 women, with an age of 72 +/- 9.4 years). The pacemaker model was Medtronic Elite 7077-7086 (DDD-DDDR) in 25 patients and Medtronic Legend 8419-8424 (VVIR-AAIR) in 22 patients. The en docavitary signal (all patients had spontaneous rhythm) was telemetrically obtained by a Medtronic 9790 device and acquired on a personal computer at implantation and 7, 30, and 280 days thereafter. The signal was studied bot h in the time domain and in the frequency domain by spectral analysis. The following parameters were calculated: amplitude (A): peak-to-peak value of the complex; slew rate (SR) peak negative first derivative; F0: frequency a t which the power spectrum reaches its maximum value; and bandwidth (Bw): e xpressed as the distance between the -3 dB points and statistically analyze d by a two-way analysis of variance with factors "time" (four measurements) and "electrode" (Capsule SP and Z) and repeated measurements on the former . Ventricular sensing: no time or electrode effect (P > 0.1 in all comparis ons) was found for F-0, Bw, or SR, while a time effect [P < 0.04] not depen dent on the type of electrode was found for the amplitude of the signal. In particular, a significant increase was found between the measurement at 6 months and that at implantation (P < 0.004). Atrial sensing: A, F0, and ban dwidth were not affected by time or electrode (P > 0.09), while SR behaved differently over time (P < 0.05) in the two electrodes (the Capsure Z showe d an increase at sixth month [P < 0.04] compared to implantation). In concl usion, the Medtronic Capsure SP and Z electrodes proved to be valid and sub stantially equivalent as far as concerns the measurement of the intracardia c potential despite the difference between their surface areas. Further stu dies should be devised to assess whether transitory decreases of atrial Bw in the first month of follow-up observed in a few patients for both electro des could be responsible for clinical episodes of sensing deficit.