Riata ICD Lead Defects
Abstract & Commentary
By John P. DiMarco, MD, PhD
Professor of Medicine, Division of Cardiology, University of Virginia, Charlottesville
Source: Liu J, et al. Fluoroscopic screening of asymptomatic patients implanted with the recalled riata lead family. Circ Arrhythm Electrophysiol 2012;5: 809-814.
More than 200,000 Riata family implantable cardioverter-defibrillator (ICD) leads from St. Jude Medical were implanted worldwide. Recently, the FDA issued a Class I recall on this lead because of the appearance of defects in the lead insulation that may lead to externalization of the conductor wires. Although the initial company statement estimated the frequency of conductor problems with Riata leads at less than 1%, subsequent reports have reported much higher rates of externalization. In this study, the authors offered voluntary fluoroscopic and electrical screening of their ICD leads to all patients who received Riata lead implants in the University of Pittsburgh Medical Center network of hospitals. Of 369 active Riata lead patients, 245 agreed to screening and were included in the study. Cine fluoroscopy of the lead was performed in three views. Lead conductor externalization was defined as the appearance of conductors outside the lead body in one or more of the views. Lead electrical performance was analyzed using standard techniques. Isometric testing was also performed to look for electrogram abnormalities that might be detected by this technique.
Among the 245 patients screened, 190 (78%) leads showed no conductor separation, 53 (22%) leads exhibited clear externalization, and in two patients the fluoroscopic imaging was inconclusive. Externalization was not seen in leads that had been implanted for less than 3 years, in 13% of leads with implant durations of 3 to 5 years, and in 26% of those with implant durations of longer than 5 years. Riata lead externalization was seen in all projections in 59% of patients, but was missed in at least one view in the remaining 41%. Patients with externalized conductors tended to be younger (62 ± 13 years or 66 ± 12 years), but this difference is not clinically helpful. Externalized leads showed a trend toward a decrease in R-wave amplitude, but this and other measures of electrical integrity remained in the normal range. Only one patient with externalized cables exhibited new noise on the right ventricular electrogram during isometric maneuvers. Far field noise was common in patients both with externalized cables and without externalized cables.
The authors conclude that cine fluoroscopic screening of asymptomatic patients with Riata leads will yield more than 20% rates of cable externalization. This appears to be a time-dependent phenomena. The relationship of externalized conductors to true electrical failure is still uncertain.
Over the last few years, we have seen several large scale Class 1 recalls of ICD leads or generators. Clinical decision making in such patients is often difficult since a number of factors must be carefully weighed. These include the expected rate of failure, the consequences of a failure, the risks of intervention, and the clinical characteristics of the patient. Intuitively, one might think generator recalls to be less problematic since the surgery required for replacement is fairly simple, but even with generator changes the risk for infection, erosion, or lead damage are not trivial. Lead replacements involve yet higher risks whether the lead is extracted. With previous recalls, more patient deaths and permanent injuries were caused by attempts at extraction than were documented to be due to the lead failures themselves. It should also be remembered that the longer a lead is in place, the greater the risk for extraction, so extracting early may be an attractive option, particularly at the time of an elective generator replacement in some situations.
In this paper, the authors show a high rate of externalized conductor wires in the Riata family of ICD leads. My laboratory and several others have made similar observations. Several questions, however, still remain. Will the rate of externalization continue to increase over longer implant durations? This seems likely but the authors here suggest a plateau may have been reached after about 6 years. What fraction of externalized conductors will actually go on to fail electrically? The externalized Riata lead conductor at least initially has a second layer of ETFE insulation and it’s possible this may provide sufficient insulation long term. Careful longitudinal follow-up data from leads with externalized conductors are certainly needed. The recent FDA statement advises either fluoroscopic screening or chest radiography, but my experience and the data here suggest a plain chest X-ray is not sufficiently accurate. Should everyone have fluoroscopy and, if so, how frequently? Is the high frequency of externalized conductors just a sign that the silicone insulation in this lead will be dangerously susceptible to both “inside-out” abrasion from lead motion and “outside-in” abrasion from contact with other leads, the generator, ligaments or bone? Until we get the better answers to all these questions, managing patients with Riata leads will remain largely guesswork.