Riata family of implantable cardioverter defibrillator leads have demonstrated in situ conductor externalization, prompting a class I recall and the Food and Drug Administration recommendation for fluoroscopic screening. The natural history of externalized Riata leads, however, remains unclear. In this study, we examined the rate of electrical failure in Riata leads with externalized cables. We reviewed medical and implantable cardioverter defibrillator records of all 329 patients with Riata leads who underwent fluoroscopic screening from December 2011 to March 2012 at the University of Pittsburgh Medical Center hospitals. Externalization was present in 76 patients (23%); of whom, 24 (32%) had the Riata lead replaced shortly after screening. The remaining 52 patients were followed for 7.9 ± 2.9 months, during which 5 patients were lost to follow-up and 2 patients exhibited electrical lead failure resulting in lead replacement, an electrical failure rate of 6.4% per year in externalized leads. In conclusion, prospective follow-up data on externalized Riata leads suggest an electrical failure rate in excess of 6% per year. This high failure rate warrants consideration of prophylactic replacement of externalized Riata leads. Further studies examining the natural history of Riata leads are warranted.
The Riata (St. Jude Medical Inc., Sylmar, California) family of implantable cardioverter defibrillator (ICD) leads were placed under class I recall by the Food and Drug Administration in December 2011 because of high rates of lead cable externalization and higher than expected electrical failure rates. Our group and others have reported on the feasibility of fluoroscopic screening of asymptomatic patients with Riata leads. In addition, the Food and Drug Administration subsequently recommended in August 2012 that all patients with Riata leads undergo fluoroscopic screening for cable externalization. The natural history of externalized Riata leads remains ill defined, however, specifically as to whether externalized leads are more likely to fail electrically. We therefore prospectively followed all patients with indwelling active Riata leads at our institution, examining the primary outcome of electrical lead failure in identified externalized leads.
Methods
All patients followed within the University of Pittsburgh Medical Center network of hospitals with an active Riata ICD lead were identified and offered voluntary fluoroscopic and electrical screening of their ICD lead. Details of the fluoroscopic and electrical screening protocol used at the University of Pittsburgh Medical Center have been previously published. All patients found to have a Riata lead with evidence of externalization were included in the present prospective analysis, which was approved by the Institutional Review Board of the University of Pittsburgh. Patient demographic and clinical characteristics were extracted from the electronic medical records. Electrical failure was defined as one of the following lead characteristics compared with baseline value at time of last normal follow-up or at the time of fluoroscopic screening: (1) R waves of <2.0 mV that also represented ≥50% decrease in R-wave amplitude, (2) ≥50% increase or decrease in pace/sense or high-voltage lead impedance, (3) ≥50% increase in pacing threshold, or (4) new electrical oversensing in the near-field or far-field ICD lead channels.
Results
A total of 584 patients (age 71 ± 13 years, 34% women) with active Riata leads were offered voluntary fluoroscopic and electrical screening at our institution ( Figure 1 ). Of these patients, 329 underwent screening and 76 (age 67 ± 15 years, 30% women) were noted to have evidence of cable externalization by fluoroscopy. At the time of screening, there was no evidence of failure in adjacent leads (other than the Riata lead). The decision to replace externalized Riata leads after initial discovery at fluoroscopic screening was made in 24 patients (32%). Reasons for immediate lead replacement included pacemaker dependence (n = 7), patient preference (n = 10), coincidental need for device revision (e.g., device at elective replacement indicator at the time of screening, n = 4), and evidence of electrical failure at the time of screening (n = 3, details provided later). The remaining 52 patients with cable externalization opted for a conservative approach with clinical follow-up. During 7.9 ± 2.9 months of mean follow-up from screening, 5 patients were lost to follow-up and 4 patients underwent lead replacement. Reasons for subsequent lead replacement included patient preference (n = 1), concomitant lead revision at time of device generator change out (n = 1), and electrical failure (n = 2). Two patients died during follow-up, neither of whom had any evidence of electrical failure at the time of death.
A total of 21 patients with externalized Riata leads but no evidence of electrical failure underwent lead replacement shortly after screening. The practice at our institution has been to recommend this approach to patients who are pacemaker dependent (n = 7 in the present study) because of the unknown natural history of the externalized Riata lead. The remaining 14 patients who were not pacemaker dependent opted for replacement after discussion with their treating electrophysiologist. Incidentally, 4 of those patients were already scheduled for a procedure, including generator change for battery depletion (n = 3) and upgrade to a cardiac resynchronization therapy device (n = 1).
Of the 76 patients found to have externalized Riata leads at screening, 3 patients (3.9%) had an evidence of electrical failure and underwent immediate lead replacement. Two patients had ≥50% decrease in R waves to <2.0 mV, and 1 patient had noise on the near-field ventricular electrogram. The electrically failing leads were dual-coil Riata 8 F 1581 models (n = 2) and dual-coil Riata ST 7 F 7001 model (n = 1). The mean dwell time since implantation of these 3 leads was 6.1 ± 0.7 years.
During prospective follow-up, 4 patients underwent replacement of externalized Riata leads: 1 patient received a new ICD lead at the time of generator change and 1 patient opted to undergo complete removal of the ICD when the existing device battery was depleted. The other 2 patients developed evidence of electrical failure. One patient had R waves decreasing from 11.8 mV at screening to 2.6 mV 5 months into follow-up, with subsequent T-wave oversensing and inappropriate antitachycardia pacing. The dwell time of this lead was 7.5 years. The second patient’s pace/sense impedance increased from 722 Ω at screening to 1,216 Ω 14 months into follow-up. This patient also became pacemaker dependent during this time and the right ventricular pacing threshold increased from 1.25 V at 0.5 ms at screening to 1.75 V at 0.5 ms. The dwell time of this lead was 7.3 years. Both leads that failed electrically during follow-up were dual-coil 8 F model 1581 Riata leads. The rate of electrical failure of externalized Riata leads was therefore 2 (4.3%) of 47 during a mean follow-up time of 7.9 ± 2.9 months from fluoroscopic screening, or 6.4% per year.
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