The Medtronic Sprint Fidelis leads (models 6930, 6931, 6948, 6949) are 6.6-F bipolar high-voltage implantable cardioverter–defibrillator electrodes that were first introduced in September 2004. In October 2007, Fidelis leads were removed from the market. We sought to determine the time-dependent hazard of the Fidelis failure rate to date. A retrospective chart review was conducted in all patients who underwent implantation of a Sprint Fidelis lead (426 leads) at our center. We primarily implanted models 6931 and 6949. With 1,056 years of combined follow-up (average 2.3 ± 1), 38 of 426 (8.92%) Sprint Fidelis leads failed (3.6%/year). The hazard of fracture increased exponentially over time by a power of 2.13 (95% confidence interval [CI] 1.98 to 2.27, p <0.001) and the 3-year survival was 90.8% (95% CI 87.4 to 94.3). If a Fidelis lead was functioning normally at 1 year, the chance it would survive another year was 97.4% (95% CI 95.7 to 99.1); if functioning at 2 years, the chance of surviving another year was 94.7% (95% CI 91.8 to 97.7); and if functioning at 3 years, the chance of surviving 1 more year was 86.7% (95% CI 78.8 to 95.5). Other commonly used implantable cardioverter–defibrillator leads showed no evidence of increased failure rates. In conclusion, to date, the hazard of Fidelis lead fracture is increasing exponentially with time and, based on our data, occurring at a higher rate than the latest manufacturer’s performance update. Further accumulative data are needed because it remains unknown if the fracture rate will level off or continue to increase.
During the previous year, 3 clinical studies have reported a higher Fidelis lead fracture rate than was indicated in the Medtronic performance update of 2009. The primary objectives of this study were to determine the performance of the Fidelis leads at a tertiary referral center and to determine if the hazard of Fidelis failure is changing with time. A secondary objective was to determine the failure rate of Fidelis leads compared to other implanted implantable cardioverter–defibrillator (ICD) leads used at our hospital during the same period.
Methods
A retrospective chart review was conducted on all patients who underwent implantation of a Sprint Fidelis (Minneapolis, Minnesota) lead at our center. We primarily implanted models 6931 and 6949. A lead was considered fractured based on the definition proposed by Farwell et al : a sudden increase in long-term pacing or defibrillation impedance (>20% increase over a 24-hour period) and/or inappropriate shock(s) secondary to sensing of electrical noise artifacts from nonphysiologic make-break potentials. Clinical and device data were obtained from the patient clinic and hospital record. Age, gender, vein of access, previous ipsilateral device implantation, most recent left ventricular ejection fraction (LVEF), and lead fracture and survival data were recorded for fractured leads. For nonfractured leads, age, gender, most recent LVEF, and survival data were recorded.
Survival function and cumulative hazard for lead fracture were estimated using the Nelson-Aalen estimator with confidence intervals (CIs) based on log transformation. To assess whether the cumulative hazard was changing over time, the log of the cumulative hazard was plotted against the log of follow-up time in months. An ordinary least squares regression model was fit to these data to quantify the rate of change of the cumulative hazard of lead fracture over time. As another approach to depict the change in risk over time, conditional survival curves, calculated based on the Nelson-Aalen estimator, which began follow-up at 1 year, 2 years, and 3 years, were derived.
Results
From September 2004 to July 2007, 426 Sprint Fidelis leads (292 model 6949, 132 model 6931, and 2 model 6948) were implanted at our center. Median follow-up time was 2.3 ± 1.0 years and 78 patients died. Total follow-up was 1,056 years. As of March 28, 2009, 38 lead fractures occurred 233 to 1,466 days after implantation ( Table 1 ). Four of the 38 patients with lead fracture died; however, no known deaths related to lead fracture were realized. From January 2004 to January 2009, a spectrum of other ICD leads was implanted, with a very low lead-fracture rate. Table 2 lists fracture rates of individual lead models where >50 implantations were performed. Among ICD leads with <50 implantations, no fractures were noted.
| Patient | Age at Implantation (years)/Gender | Age of Lead at Fracture (days) | Presentation | Most Recent LVEF | Indication | Outcome |
|---|---|---|---|---|---|---|
| 1 | 56/M | 1,152 | IS–1 | 25 | CAD | SC, LR, Ext |
| 2 | 56/M | 344 | alert–1 | 25 | CAD | SC, LR |
| 3 | 59/M | 1,293 | IS–2 | 25 | CAD–2 | DC, LR |
| 4 | 63/M | 1,060 | IS–12 | 30 | CAD | SC, LR |
| 5 | 65/M | 356 | IS–1 | 25 | CAD | BIV, LR ⁎ |
| 6 | 67/M | 959 | alert | 35 | CAD | SC, LR |
| 7 | 68/M | 885 | IS–2 | 25 | CAD | SC, LR |
| 8 | 68/M | 1,385 | IS–8 | 50 | CAD | DC, LR |
| 9 | 68/F | 1,271 | IS–7 | 35 | CAD–2 | DC, LR |
| 10 | 69/M | 829 | alert | 55 | CAD | SC, LR, Ext |
| 11 | 70/M | 372 | IS–21 | 25 | CAD | BIV, LR ⁎ |
| 12 | 71/M | 233 | failure to pace | 32 | CAD | DC, LR, Ext |
| 13 | 72/M | 619 | failure to pace | 35 | CAD | SC, LR, PM Dep |
| 14 | 73/M | 326 | IS–9 | 45 | CAD | SC, LR, Ext |
| 15 | 73/M | 313 | IS–15 | 45 | CAD | SC, LR |
| 16 | 74/F | 797 | alert | 33 | CAD | SC, LR |
| 17 | 74/M | 1,292 | IS–54 | 30 | CAD–2 | DC, OFF ⁎ |
| 18 | 75/M | 781 | alert | 20 | CAD | DC, LR, Ext |
| 19 | 77/M | 938 | IS–5 | 50 | CAD–2 | SC, LR |
| 20 | 82/M | 593 | failure to pace | 30 | CAD | DC, LR, PM Dep |
| 21 | 31/M | 926 | IS–2 | 55 | IDC | SC, LR, Ext |
| 22 | 52/F | 533 | — | 65 | IDC | BIV, LR |
| 23 | 58/M | 1,061 | IS–11 | 50 | IDC | BIV, OFF |
| 24 | 60/M | 727 | IS–8 | 28 | IDC | DC, LR |
| 25 | 64/M | 1,219 | alert | 20 | IDC | SC, LR, Ext |
| 26 | 65/M | 598 | — | 10 | IDC | BIV, LR |
| 27 | 67/F | 1,112 | alert | 28 | IDC | BIV, LR, Ext |
| 28 | 70/F | 961 | alert | 30 | IDC | SC, LR ⁎ |
| 29 | 71/M | 260 | oversensing | 25 | IDC | DC, LR |
| 30 | 74/F | 818 | — | 35 | IDC | DC, LR |
| 31 | 76/M | 1,313 | IS–4 | 23 | IDC | BIV, LR |
| 32 | 82/F | 1,466 | IS–42 | 35 | IDC | BIV, LR |
| 33 | 21/M | 662 | IS–43 | 60 | HC | SC, LR |
| 34 | 22/F | 948 | IS–1 | 55 | HC | SC, LR, Ext |
| 35 | 54/F | 1,336 | IS–1 | 70 | HC–2 | SC, LR |
| 36 | 14/F | 728 | oversensing | 60 | LQTS–2 | SC, LR, Ext |
| 37 | 35/M | 692 | alert | 65 | VT–2 | SC, LR, Ext |
| 38 | 51/M | 1,237 | IS–6 | 45 | VT–2 | SC, LR |
| Implanted Lead Model | No. Implanted | Total Fractured (%) |
|---|---|---|
| Model 6947 (Medtronic) | 221 | 1 (0.45%) |
| Model 0185 (Boston Scientific) | 290 | 0 (0.0%) |
| Model 0184 (Boston Scientific) | 67 | 0 (0.0%) |
| Model 0158 (Boston Scientific) | 72 | 0 (0.0%) |
| Model 1581 (St. Jude Medical) | 113 | 2 (1.76%) |
| Model 7121 (St. Jude Medical) | 71 | 0 (0.0%) |
Table 3 lists clinical characteristics of the fractured and nonfractured Sprint Fidelis leads. Among the 38 Sprint Fidelis lead fractures, 8 patients (21.1%) had previous ipsilateral device implantation and 35 (92.1%) underwent implantation by axillary vein access. Twenty patients (52.6%) underwent implantation due to ischemic heart disease, 12 (31.6%) for idiopathic dilated cardiomyopathy, 1 (2.6%) for long QT syndrome, 3 (7.9%) for hypertrophic cardiomyopathy, and 2 (5.3%) for sustained idiopathic ventricular tachycardia with normal heart function. Of the 38 patients, there were 8 in whom a secondary prevention strategy was employed. There were 4 deaths (10.5%) in this population, none of which was felt to be related to the Fidelis fracture. There were 74 deaths (19.1%) in the nonfractured population during the same period.
| Fractured Fidelis | Nonfractured Fidelis Leads | |
|---|---|---|
| No. | 38 | 388 |
| Age at implantation (years), mean ± SD | 61.7 ± 16.7 | 67.6 ± 14.8 |
| Model 6949 (%) | 25 (66%) | 267 (69%) |
| Model 6931 (%) | 13 (33%) | 119 (31%) |
| Model 6948 (%) | 0 (0%) | 2 (0.5%) |
| Men (%) | 28 (74%) | 289 (74%) |
| Most recent LVEF (%), mean ± SD | 37 ± 14.9 (average 169 days after implantation) | 30 ± 14 (average 294 days after implantation |
| Age of lead at most recent follow-up (days), mean ± SD | 852 ± 355 | 897 ± 379 |
| Deaths (%) | 4 (10.5%) | 74 (19.1%) |
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