Fidelis Lead Fracture Risk

Abstract & Commentary

By John P. DiMarco, MD, PhD, Professor of Medicine, Division of Cardiology, University of Virginia, Charlottesville

Source: Parkash R, et al. Sprint Fidelis lead fractures in patients with cardiac resynchronization therapy devices: Insight from the Resynchronization/Defibrillation for Ambulatory Heart Failure (RAFT) study. Circulation 2012;126:2928-2934.

The Medtronic Sprint Fidelis Lead (Model 6949) is known to have a high rate of lead fracture. In this paper, the authors look at survival of the Sprint Fidelis lead in the setting of a third lead for cardiac resynchronization.

The Resynchronization/Defibrillation for Ambulatory Heart Failure (RAFT) trial was a randomized trial that enrolled patients between 2003 and 2009. The Sprint Fidelis lead was the most common implant during the period between 2004 and 2007. Although not specifically mentioned in this paper, it may be assumed that the Medtronic Sprint Quattro Lead was used in most of the other cases. Patients in RAFT were randomized between either a cardiac resynchronization therapy (CRT) device or a standard implantable cardioverter defibrillator (ICD) device. Implant was via standard techniques. During follow-up, lead fractures were classified if two of the following three criteria were noted: 1) an impedance rise > 50% or > 500 ohms in 1 week, 2) a short V-V interval count > 10 per day or 300 per month, and 3) inappropriate shock or shocks because of noise recorded on the electrogram.

The RAFT study randomized 1798 patients who were then followed for a median of 39 months. Of these, 818 received a Sprint Fidelis Lead as their initial right ventricular lead. The characteristics of patients who received a Fidelis vs a non-Fidelis lead were similar. There was no difference in the composite clinical outcome of mortality or heart failure hospitalizations between the two groups. Device-related hospitalizations occurred slightly more frequently in the Fidelis group (33.9%) compared to the non-Fidelis group (31.5%). Lead fractures were much more common in the Fidelis patients. There were a total of 47 lead fractures in the entire study, with 45 of these (95.7%) occurring in the Fidelis group. The annual rate of Fidelis fracture was 1.65% per year with an increasing frequency over time. In 30 of these 45 patients, the fractures led to one or more inappropriate shocks. Compared to patients who received a standard ICD, patients who received a CRT device had an increased risk of developing a lead fracture with a hazard ratio of 2.42.

The authors then speculate that there may be several mechanisms for the increased risk of fracture in the patients who received a CRT device. The factors they list include the increased bulk of the leads, which may lead to higher likelihood of lead interaction; the effect of CRT on overall ejection fraction and exercise tolerance; and finally, the likelihood that noise was more likely to be detected in patients with a high frequency of pacing such as used in CRT patients. The authors conclude that although lead fractures did not affect mortality or hospitalization in the study, fractures were frequent and there was an increased risk of fracture in CRT patients.

Commentary

The RAFT trial provides an interesting opportunity to look in isolation at the effects of adding an additional lead on fractures of a model prone to fracture. In the Fidelis experience, conductor fractures occur mostly either near the distal ring or in the pocket near the proximal tie down. It is likely that the fact that three tie downs have to be placed in a relatively confined area in the floor of the pocket may contribute to the stress on the lead and the increased failure rate observed here. This is also supported by the recent observation that failures of Sprint Fidelis leads are more common after generator exchanges during which the proximal portion of the lead is again manipulated.1

Many patients with Fidelis leads are now reaching the elective replacement indicator for their devices. Physicians who elect to leave the Fidelis lead in place should be aware of the increased risk of damage at the level of the tie down area during the generator replacement and should try to only gently manipulate the lead to avoid an increased risk of fracture.

Reference

1. Lovelock JD, et al. Generator exchange is associated with an increased rate of Sprint Fidelis lead failure. Heart Rhythm 2012;9:1615-1618.