Cardiovascular alterations induced by chronic transvenous implantation of an automatic defibrillator electrode catheter in dogs.

Six dogs (three large, three small) had defibrillator electrode catheters implanted transvenously via the right jugular vein for 17 weeks. The dogs remained healthy throughout the study. At necropsy, the lead-induced cardiovascular alterations were characterized by (1) formation of a thin white fibrous sheath over portions of the lead along its course in the veins, right atrium and right ventricle; (2) adhesion of parts of the sheathed segments of the lead to the adjacent venous intima or endocardium of the right atrium, tricuspid valve and right ventricle; (3) endocardial fibrosis with foci of cartilaginous metaplasia in areas traumatized by the lead; (4) thrombus formation at ends of sheathed segments of the lead but lack of pulmonary embolism; and (5) partial penetration of the myocardium at the apex of the right ventricle by the end of the lead in two of the small dogs. The lead-induced lesions were similar in type and severity to those produced by chronically-implanted pacemaker leads.