Sensing lead insulation fractures following implantable cardioverter-defibrillator placement

The insulation of implantable cardioverter-defibrillator (ICD) sensing leads can fracture, causing device malfunction. Before March 1989, 32 patients received silicon CPI K54 sensing leads. Of these, four (12.5%) experienced discharges while in sinus rhythm. Subsequent ICD interrogation revealed that abdominal muscular contraction triggered discharges in two patients, but no abnormal sensing could be elicited in the other two patients. These patients subsequently were found to have sensing lead fractures. All sensing leads appeared intact radiographically but at reoperation were found to have insulation fractures 2-4 cm from the pin. The mechanism of fracture appears to be related to chronic intermittent lead compression between the anterior abdominal wall musculature and the ICD generator. Since March 1989, 134 patients have undergone ICD implantation with improved CPI 4312 sensing leads; none of these patients has experienced sensing lead fractures. The insulation of these leads is 2.5 times thicker than the K54 (1.0 mm vs. 0.4 mm). Patients with K54 sensing leads are at an increased risk for sensing lead insulation fracture and merit close surveillance. More importantly, sensing lead fractures must be considered in patients who present with inappropriate ICD discharges.