Inside-out insulation failure of a defibrillator lead with abrasion-resistant coating Charles D. Swerdlow, MD, FHRS, Robert M. Kass, MD, Ali Khoynezhad, MD, PhD, Stephen Tang, MD From the Cedars-Sinai Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California. Clinical report A 78-year-old woman had a cardiac resynchronization implantable cardioverter-defibrillator implanted in January 2008 for nonischemic cardiomyopathy with New York Heart Association class III heart failure, left ventricular ejection fraction 22%, and left bundle branch block. A St Jude Medical Model 7121 Durata right ventricular lead (St Jude Medical, St Paul, MN) and a Medtronic Model D224TRK Consulta generator (Medtronic, Minneapolis, MN) were implanted. Three months later, ejection fraction improved to 47% and heart failure improved to class I. In July 2010, a combination of recent short intervals ≤140 ms and rapid, repetitive oversensing triggered the Lead Integrity Alert. 1 Interrogation showed an inappropriate detection of ventricular tachycardia treated with antitachy- cardia pacing. Stored electrograms showed nonphysiological signals, some of which occurred synchronously with the cardiac cycle, timing with the T wave. Pacing threshold was 1.0 V, the R wave was stable at 10 mV, and both pacing and high-voltage impedances were within nominal ranges. However, the weekly minimum pacing impedance decreased by approximately 150 Ω (from 470 to 320 Ω) in February 2010. Differential real-time and telemetry Holter recordings isolated the nonphysiological signals to the cable to the ring electrode rather than the helix to the tip electrode (Figure 1A). Corresponding recordings from shock channels determined that simultaneous nonphysiological signals were present on the distal coil, but not the proximal coil. Additional diagnostic steps excluded other causes of oversensing. Initially, the patient declined lead replacement. But when frequent oversensing caused the percentage of biventricular pacing to decrease below 90% in late 2012, lead replacement was recommended to preserve resynchronization. Cine- fluoroscopy (Figure 1B) showed no exteriorized cables or mechanical lead-lead interaction. Explanted lead In January 2013, the lead was extracted by using a 14-F laser sheath without an outer sheath. After obtaining separate vascular access, lasing was performed at binding sites in the innominate vein and at the proximal coil. Then the lead tip came free with gentle traction/countertraction, and the lead was withdrawn smoothly into the laser sheath, without resistance; the sheath and the lead were removed together. Four locations on the lead showed visible damage. We arbitrarily labeled them zones 1–4 from distal to proximal. Figure 2A shows the distal 3 zones. Figures 2B–2D show progressively magnified views of the lead near the proximal end of the distal coil (zone 1). Figure 2B shows that the distal end of the outer tubing, composed of a silicone-polyurethane copolymer (Optim™, St. Jude Medical), does not extend to the coil. Instead, the tubing and the coil are separated with silicone backfill. At the coil’s proximal margin, the ring- electrode cable has abraded inside-out through the silicone wall of its surrounding lumen. The upward arrow shows the cable’s intact blue ethylene tetrafluoroethylene (ETFE) insulation. The downward arrow indicates where the cable has abraded through the ETFE, revealing the underlying conductor, which contacts the distal coil. In Figure 2C, the arrow indicates where the cable to the distal coil also abraded through the wall of its lumen, with the ETFE tubing intact. Figure 2D shows that the exposed cable filars are flat, rather than round, as a result of abrasion against the coil. Figure 3A is an intraoperative photograph taken imme- diately after explant. The inside-out abrasion extends prox- imally from zone 1 to zone 2 (7.6–8.5 cm from the tip). Between them, ETFE insulation is visible immediately beneath the Optim tubing on cables to both the ring electrode and the distal coil. The ring electrode cable is also visible in an oval-shaped defect in the tubing (1.5 Â 3 mm). There is a crack in the trough between the defect and the ridge immediately distal to it. The tubing adjacent to the defect is discolored by underlying deposits of the biological material. Figure 3B shows zone 2 after the removal of the tubing. The ring electrode cable exits its silicone lumen near the proximal end of the removed tubing, defining the proximal boundary of the abrasion (downward arrow). The upward arrow indicates biological deposits that were under the tubing until it was removed. KEYWORDS Lead failure; Implantable cardioverter-defibrillator ABBREVIATIONS ETFE ¼ ethylene tetrafluoroethylene (Heart Rhythm 2013;10:1063–1066) Dr Swerdlow is a consultant to St Jude Medical and Medtronic. Address reprint requests and correspondence: Dr Charles D. Swerdlow, Cedars- Sinai Heart Institute, Cedars-Sinai Medical Center, 414 N Camden Dr, Ste 1100, Beverly Hills, CA 90210. E-mail address: swerdlow@ucla.edu. 1547-5271/$-see front matter B 2013 Heart Rhythm Society. All rights reserved. http://dx.doi.org/10.1016/j.hrthm.2013.03.024