Lead externalization is a problem where the lead wires of the device pokes through the insulation. The findings of a Danish study suggest that “lead externalizations” with St. Jude Medical’s recalled Riata and Riata ST defibrillator leads are associated with electrical failures and gets worse over time. Lead externalization is a problem where the lead wires of the device pokes through the insulation; this defect is what prompted the recall in the first place, according to Mass Device.
Heart Rhythm published the study, titled “Prospective Nationwide Fluoroscopic and Electrical Longitudinal Follow-up of Recalled Riata Defibrillator Leads in Denmark” this month. Researchers followed 295 Danish patients who were implanted with Riata leads at least 5.1 years ago. There were 34 initial cases of externalized conductors and 19 electrical abnormalities. Researchers followed the patients until death, lead discontinuation with fluoroscopy or a new screening in 2013 with fluoroscopy and device interrogation. The study was led by Dr. Jacob Larsen of Denmark’s Aalborg University Hospital.
20 cases of electrical abnormalities among 276 patients who have normal electrical function
Among the group of patients who started the study with externalized conductors, 27 experienced an increase in length of externalization by 4mm after 1.1 years. After 1.1 years, there were 8 more cases of over externalized conductor and 2 cases that were borderline. Dr. Larsen’s team found an incidence rate of 3.7 per 100 person-years.
After one year, there were 20 cases of electrical abnormalities among 276 patients who had normal electrical function previously, yielding an incidence rate of 7.1 per 100 person-years. Patients who started off with externalized conductors were more than 4 times as likely to develop electrical abnormalities, the study found.
The development of EC is a dynamic process despite long lead dwell time
“The development of EC is a dynamic process despite long lead dwell time. EC are associated with a higher risk of electrical abnormalities. Therefore, lead replacement should be considered, especially in patients with long life expectancy,” the authors wrote.
St. Jude is also conducting an ongoing study over the recalled leads. According to Mass Device, the study is larger with 776 patients in multiple facilities; the prospective study showed that leads with externalized conductors led to electrical failure 3.1 percent of the time. This compares to 2 percent in patients without externalized conductor leads.
Larsen says his study does not prove that lead externalizations caused electrical abnormalities, or whether this issue is a marker for “potentially failing ‘stressed’ leads,” he said to Heartwire. “We cannot tell from the available data. But the data strongly suggest that a recalled Riata lead with visible externalization is associated with a higher risk of electrical abnormalities in the clinical setting,” wrote Larsen.