Differences in encapsulating lead tissue in patients who underwent transvenous lead removal

The aim of our study was to characterize specific tissue reaction of encapsulating lead tissue in patients who underwent transvenous lead removal and evaluate condition of the outer leads' insulation.

Fifty-six leads (27 atrial, 24 ventricular, 5 implantable cardioverter-defibrillators) were removed from 31 patients (mean age 70 years). Indications for removal were chronic pocket infection (CPI) (9 patients ), infective endocarditis (IE) (6), and non-infective indications (NI) (16). Leads with their surrounding tissue were fixed in paraformaldehyde. Tissues were embedded in paraffin wax, stained with haematoxylin-eosin, and examined histologically. The outer leads' insulations were examined in stereomicroscope. The mean lead age encapsulated by connective tissue sheath was 89, whereas encapsulated by granulation tissue was 47.34 months (P= 0.03). Calcification was present in 13 patients. Haemosiderine was observed only in patients with severe abrasion with perforation in the pocket (P= 0.04). Vasculogenesis was present in one (6%) with NI, five (56%) with CPI, and three (50%) with IE (P= 0.02) and was associated with elevated white blood cells (WBC) (P= 0.04). Eosinophilia was associated with elevated WBC (P= 0.04). The most frequently observed are third level of degradation (severe with perforation) in the intracardiac part of the silicone leads. Insulation damage due to environmental stress cracking concerned all leads with polyurethane overlay.

Granulation in encapsulating tissue was present in patients with younger leads. Vasculogenesis was observed more often in IE and CPI patients, which might indirectly indicate thickness of the sheath. Eosinophila may indicate allergic component of inflammation. Insulation damage frequently concerned the intracardiac part.