| Abstrakt: |
Sixty-one patients given programmable pacemakers at initial implantation have been followed for a mean of 18 months (3–42) with non-invasive measurements of myocardial pulse-width threshold. Fifty of the patients had CPI 0505/0522 (Microlith-P/Microthin-PI) pacemakers with either Cordis 322–462 8 mm² ball tip (n=12), Cordis 322–620 17.5 mm² (n=23), or CPI 4116 porous tip electrodes (stimulation area 7.5 mm² and sensing area 50 mm²) (n=15). Eleven patients had Medtronic 5985 (Spectrax-SX) pacemakers with either Medtronic 6907-R 8 mm² ring tip (n=7), 690711 mm² (n=3) or 6917 myocardial electrodes (area 12 mm²) (n=1). At acute implant, the ball tip and porous tip electrodes had the lowest stimulation thresholds, but the differences were only statistically significant in comparison with the 17.5 mm² electrode (p<0.01). Chronically there were no significant differences between the various electrodes (p>0.1), but the ball tip electrode tended to give best long-term results, and the porous tip electrode the poorest. Thirty-eight of the 61 patients (62.3%) had chronic pulse-width thresholds of 0.1 ms or less at ≈ 5 V output, indicating that pulse-width programming is a useful way to conserve battery energy. However, at some stage of the study, six of the patients (9.8%) had a pulse-width threshold of 0.5 ms or more. Pulse width should therefore not be set too narrow in standard nonprogrammable pacemakers. [ABSTRACT FROM AUTHOR] |
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