New temporary atrial and ventricular pacing leads for patients after cardiac operations

Abstract

We have studied two new temporary pacing leads (Medtronic 6491 and 6492) intended for pacing after cardiac operations. The conductor has stainless steel strands coated with polyethylene connected to a 4 mm 2 surface area, stainless steel, smooth, tapered electrode. A soft 4-0 coiled polypropylene fiber served as a fixation mechanism in the heart. The study included 15 children (aged 3 months to 7 years, body weight 4.4 to 20 kg) with a variety of congenital heart defects and 15 adults (aged 45 to 78 years) with coronary artery disease ( n = 13) and aortic valve disease ( n = 2). A pair of leads each was placed in a bipolar fashion in the right atrial wall and nonsystemic ventricle in the children (median implant duration 12 days) and in the right atrial wall only in the adults (median implant duration 9 days). The atrial current threshold values in children increased from 0.61 ± 0.34 mA immediately after implant to 2.08 ± 1.86 mA at explant ( p < 0.002). In the adults the threshold values increased from 0.95 ± 1.44 mA immediately after implant to 2.76 ± 2.76 mA at explant ( p < 0.002). In the ventricle the threshold values increased from 0.38 ± 0.13 mA immediately after implant to 2.22 ± 1.63 mA at explant ( p < 0.002). Tissue resistance immediately after implant measured 809 ± 182 Ω in the atrium and increased to 820 ± 204 Ω at explant (children, p = not significant). Corresponding values in adults were 778 ± 190 Ω and 599 ± 91 Ω ( p < 0.004). In the ventricle resistances changed from 1019 ± 143 Ω to 876 ± 137 Ω ( p < 0.05). P wave amplitudes measured 1.8 ± 1.5 mV immediately after implant and decreased to 1.6 ± 1.2 mV at explant ( p = not significant, children) and 2.0 ± 1.3 mV to 1.8 ± 1.1 mV ( p = not significant, adults). R wave amplitudes were 13.1 ± 3.0 mV immediately after implant and fell to 8.7 ± 4.5 mV at explant ( p < 0.005). Thus threshold values, tissue resistances, and electrogram amplitudes assured a safe pacemaker function. The small diameter and pliable texture of these leads provided a smooth surgical handling. They were found particularly suitable in children. (J T HORAC C ARDIOVASC S URG 1995;110:1725-31)