INTRAPATIENT COMPARISON OF ATRIAL AND VENTRICULAR SENSING, PACING THRESHOLD, AND IMPEDANCE : BENEFITS WITH STEROID-ELUTING LEADS

We compared the atrial and ventricular bioelectrical effects relating to pacing threshold, pacing impedance, and pacing energy in each of 58 patients to determine the importance of pacing impedance in safe low energy stimulations. The study was conducted during 4 years of follow-up. Of the 58 patients in our study, 31 were stimulated in both chambers with steroid-eluting leads (Capsure 4503 and 4003) and 27 with platinum electrode catheters (Target Tip 4511 and 4011). The two groups were homogeneous in sex, age, cardiopathy, and reason for implant. At 6 months, the mean impedance values for the Target Tip were: 358 ± 72 Ω for the atrium and 443 ± 87 Ω for the ventricle (P < 0.00002): after 1 year, atrium = 386 ± 77 Ω, ventricle = 439 ± 42 Ω (P < 0.04); at 2 years, atrium = 409 ± 86 Ω, ventricle = 510 ± 94 Ω (P < 0.0001); at 3 years, atrium = 428 ± 81 Ω, ventricle = 494 ± 67 Ω (P < 0.02); and at 4 years, atrium = 424 ± 71 Ω and ventricle = 501 ± 69 Ω (P < 0.003). The mean impedance value (for the Capsure) was: atrium = 351 ± 43 Ω, ventricle = 431 ± 81 Ω at 6 months (P < 0.03); at 1 year, atrium = 359 ± 38 Ω, ventricle = 446 ± 83 Ω (P < 0.01); at 2 years, atrium = 304 ± 124 Ω, ventricle = 459 + 108 Ω (P <0.0003); at 3 years, atrium = 359 ± 108 Ω, ventricle = 461 ± 89 Ω (P < 0.02); and at 4 years, atrium = 419 ± 133 Ω and ventricle = 515 ± 75 Ω (P < 0.03;. In view of the chronic threshold, low energy stimulation was used at follow-up. The mean low energy stimulation values programmed for Target Tip were: atrium = 2.5 V/0.35 ms, ventricle = 2.5 V/0.30 ms; for Capsure, atrium = 2.5 V/0.25 ms, ventricle = 2.5 V/0.25 ms. The mean stimulation energy value was 31% higher in the atrium than in the ventricle with Capsure leads, and 39% higher with Target Tip. Pacing impedance was lower in the atrium than in the ventricle with both leads. Energy consumption in the atrium is significantly greater than in the ventricle with both leads, particularly with Target Tip.