Paired Comparisons of Steroid-Eluting and Nonsteroid Endocardial Pacemaker Leads in Dogs: Electrical Performance and Morphologic Alterations

• Published in: Pacing and clinical electrophysiology 1988-07, Vol.11 (7), p.1085-1094
• Main Authors: RADOVSKY, A.S., VAN VLEET, J.F., STOKES, K.B., TACKER JR, W.A.
• Format: Article
• Language: English
• Subjects: Animals; artificial; Dexamethasone - administration & dosage; Dexamethasone - analogs & derivatives; Dogs; Efficiency; electrodes; Electrodes, Implanted; Equipment Design; implanted; myocardium; pacemaker; Pacemaker, Artificial; pathology
• ISSN: 0147-8389; 1540-8159
• DOI: 10.1111/j.1540-8159.1988.tb03955.x

The effects of steroid elution from endocardial pacemaker electrodes on electrical performance and the thickness and cellularity of the reactive fibrous connective (issue formed around the stimulating electrode (peri‐electrode tissue) were determined. Comparison was made with a nonsteroid electrode implanted in the same cardiac chamber (right ventricle) in each of six dogs for 6 weeks. Paired Students t‐tests showed that steroid‐eluting leads had significantly (P < .05): (1) lower voltage stimulation thresholds (as determined in sequential measurements made on the conscious animals during the experiment and on the anesthetized dogs at termination of the study); (2) less fibrous connective tissue formation around the electrode surfaces; and (3) fewer cells per unit area of peri‐electrode fibrous connective tissue. There were also fewer (P < .10) mast cells in the reactive connective tissue surrounding steroid‐eluting leads. The thinner reactive connective tissue surrounding the steroid‐eluting electrodes was correlated with lower voltage stimulation thresholds(r = 0.7. P < .01). This is consistent with the hypothesis that the effect of the peri‐electrode connective tissue is to increase the virtual surface area of the electrode, decreasing current density in adjacent stimulatable tissue. The relatively fewer total cells and mast cells in the peri‐electrode connective tissue of the steroideluting electrodes suggest that the observed differences in fibrous connective tissue thickness, and therefore voltage stimulation threshold, may be related to a relatively decreased population of inflammatory ceils due to the anti‐inflammatory properties of the steroid.