Creation and In Vivo evaluation of a porous electrode for pacing in a coronary vein: an assessment of the potential for improved electrical performance and chronic stability of coronary venous pacing leads.

Abstract

In this work, a porous electrode was fabricated and evaluated in a chronic animal study on a coronary venous pacing lead in order to assess its potential for mitigating chronic lead dislodgements and reducing the characteristic rise in pacing thresholds after implant, both of which being important issues that impact safety and efficacy of implanted cardiac resynchronization therapy systems. Eight test leads were assembled with a porous tip electrode with an average pore size of approximately 30 micrometers, created via a novel fabrication method, and eight control leads were assembled with a standard solid tip electrode design. Both groups were created without steroid-eluting collars and without a capacitive coating on the tip electrodes in order to isolate the affects of electrode porosity. Leads were implanted in canines, and electrical data and x-rays of lead position were taken regularly throughout the 60-day study. Tissue histology was performed for each lead. Significantly lower (p<0.05) mean rise in pacing threshold after implant was observed at day 3 and day 21 for the test group leads (with porous electrodes) as compared to the control group leads. Despite the higher surface area of the porous tip electrodes, pacing impedance was not statistically different between the groups throughout the study, a result likely due to decreased chronic inflammatory response at the surface of porous electrodes. The test group had no lead retractions after day 3 as determined by inspection of x-ray radiographs, while 3-6 (of 8) control group leads retracted after day 3, a result likely due to anchoring of the lead tip due to observed tissue growth into porous electrodes. Mean fibrous capsule thickness at pre-defined measurement points on the tip electrode was not statistically different between the groups, which correlates with the nearly equal mean pacing thresholds for the groups at day 60. The lack of lead retractions for the test groups leads after day 3 is a promising result which should be investigated further, along with investigations of lead extraction force and further electrical data evaluations, using larger sample sizes and more challenging implant conditions.