Sprint Fidelis defibrillator leads were recalled in 2007 due to a high failure rate. Among the clinical adverse events associated with this lead failure, the most devastating was the delivery of multiple inappropriate shocks during sinus rhythm due to oversensing of make-brake potentials. In patients with a functional Fidelis lead at generator replacement, the manufacturer recommended to either continue to use the existing lead or replace it with a new defibrillator lead. We evaluated an alternative to prevent inappropriate shocks triggered by oversensing from a fractured Fidelis lead after cardiac resynchronization therapy-defibrillator (CRT-D) generator replacement.
Three elderly patients (mean age 81± 5 yrs) with a functional Fidelis lead (6949) and a bipolar left ventricular (LV) lead (4194) underwent CRT-D generator replacement. These patients were not good candidates for defibrillator lead replacement due to the comorbidity and venous access occlusion. During the procedure, the pace/sense IS-1 connector pin of the functional Fidelis lead was intentionally inserted into the LV port of the new CRT-D generator while the existing bipolar LV lead IS-1 connector pin was inserted into the right ventricular (RV) pace/sense port. After such switching, the existing LV bipolar lead was used for pacing/sensing RV, while the Fidelis lead was used for pacing LV only. As the existing Fidelis lead is no longer used for sensing ventricular electrical activities, the oversening issue has been eliminated even if this lead fails.
During a follow-up of 3±2 years after CRT-D generator replacement and switching of Fidelis lead pace/sense pin with bipolar LV lead, in-office interrogations and remote monitoring showed normal device function including biventricular pacing, ventricular tachyarrhythmia detection and appropriate antitachycardia therapy.
In CRT-D patients with a functional Fidelis lead and a bipolar LV lead, switching of Fidelis lead pace/sense pin with bipolar LV lead during generator replacement did not affect device function. This approach could potentially prevent inappropriate shocks triggered by oversensing due to future lead fracture.