Lead insulation failure, a serious complication: risk factors and management.

“OUTSIDE-IN” ABRASIONS: A NEW PHENOMENA — MORE QUESTIONS THAN ANSWERS We may divide abrasions according to mechanism into “outside-in” and “inside-out” abrasions. The “outside-in” abrasions are well known in the pocket as the result of friction between leads or between the lead and the device, as well as in the venous system, with tearing surfaces among leads, first rib, and clavicle. However, “outside-in” abrasions most frequently appear in the intracardiac part of the lead and are associated with infective endocarditis (IE) [2]. The outer insulation abrasion remains electrically signless unless concomitant inner insulation failure occurs and in the device control both oversensing and undersensing may be observed [3]. The Banacha classification was established to morphologically describe abrasions analysed with an optical microscope, and to facilitate comparison and analysis. The classification distinguishes three levels of silicone in vivo damage: mild, moderate, and severe, all in two subtypes: a and b [2]. A severe abrasion with conductor exposure may be assessed clinically (Fig. 1A) [4]. Insulation abrasion more often concerned patients with sub-pectorally or abdominally implanted devices. Risk factors of intracardiac abrasions are implantation of two or more leads in the heart cavities, and in the case of atrial leads: passive fixation, longer mean dwell time (time from implantation), and three or more procedures proceeding lead extraction [2]. Severe abrasions with conductor exposure were associated with the number of extracted leads, dwell time, location of the lead in the coronary sinus, and excessive lead length in the cardiac chambers [4]. The most important observation was that, irrespective of the abrasion level of degradation in the intracardiac part of the lead, they were associated with IE development [2]. The process of outside-in abrasion may be INTRODUCTION Endocardial leads are the most important parts of cardiovascular implantable electronic device systems. The endocardial lead parts are located in the tissue of the pocket, in the venous system, and finally in the right heart cavities. The three different microenvironments present different impacts on lead body parts, especially the outermost insulation. Lead design also concerns the outer insulation, which has been evaluated since implantation of the first pacemaker. In the current paper we present the different mechanisms of insulation failure of the leads available on the market, and of leads that have been withdrawn from the market but still exist in living patients. The outer lead insulation may dictate the lead reliability. Silicone, polyurethane, fluoropolymers (PTFE, ETFE), and co-polymer silicone-polyurethane (Optim) are materials widely used as insulation of endocardial leads. Insulation breach and abrasions may occur anywhere along the lead. The lead parameters: abnormal sensing amplitudes, abnormal and variant pacing thresholds, and lead impedance abnormalities may be indicators of lead failure. The insulation characteristics of typical damage, lead failure symptoms, and lead management are crucial for patients, theirs doctors, scientists, and manufacturers.