Acute and Chronic Pulse‐Width Thresholds in Solid Versus Porous Tip Electrodes

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Abstract
Sixty‐one patients given programmable pacemakers at initial implantation have been followed for a mean of 18 months (3‐42) wilh 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 mm 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), 6907 11 mm2 (n = 3) or 6917 myocardial electrodes (area 12 mm2) (n = 1). At acute impant, the ball tip and porous tip electrodes had the lowest stimuialion 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. (PACE, Vol. 5, Septemher‐October, 1982)

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