Histological findings around electrodes in pacemaker and implantable cardioverter-defibrillator patients: comparison of steroid-eluting and non-steroid-eluting electrodes.

AIMS: To analyse histological findings surrounding the electrodes in pacemaker/implantable cardioverter-defibrillator (PM/ICD) patients. To compare histology around steroid-eluting and non-steroid ventricular pacing electrodes. METHODS AND
RESULTS: In autopsied PM/ICD patients histopathological findings around the electrodes were determined. Seventy patients were studied, PM(58), ICD(12), mean age 75.1 ± 9.3 years. The implantation-death interval was 4.0 ± 3.3 years. Most causes of death were cardiac (PM 52%, ICD 58%). The majority of atrial electrodes were attached to the endocardium and most ventricular electrodes were found in the myocardium (P ≤ 0.001). The maximum thickness of the fibrous electrode sheath was greatest for the ICD ventricular electrodes. Some electrodes were covered with fibrin thrombi and granulation tissue, most frequently in the ICD ventricular electrodes. The fibrous sheath usually contained chronic inflammatory cells and in some cases particles of foreign material, foreign body giant cells, and haematogenous pigment. The tissue around steroid-eluting ventricle PM electrodes was compared with the tissue around the non-steroid-eluting ventricle PM electrodes; granulation tissue, foreign material, giant cells being found more frequently around the steroid-eluting electrodes. The fibrous sheath was slightly thinner in the steroid-eluting electrodes. The histology around four coronary sinus electrodes was described.
CONCLUSIONS: Atrial electrodes were attached more superficially to the endocardium while PM and ICD ventricular electrodes were more frequently embedded in the myocardium. The electrodes were covered by a connective tissue sheath as a result of thrombus organization. This process persisted most frequently around ICD ventricular electrodes. Only borderline differences were found between the histological findings around steroid-eluting and non-steroid-eluting PM ventricular electrodes.