St. Jude Medical’s Riata and Riata ST defibrillator leads were recalled in the past due to “lead externalizations”, a defect where the wires protrude through the insulation. Now, a Danish study has linked this issue to a higher risk of electrical failures that worsens with time.
The study was led by Dr. Jacob Larsen of Denmark’s Aalborg University Hospital and published this month in Heart Rhythm entitled “Prospective Nationwide Fluoroscopic and Electrical Longitudinal Follow-up of Recalled Riata Defibrillator Leads in Denmark”. The cohort consisted of 295 Danish patients implanted with Riata leads at least 5.1 years ago. Initially, 34 patients had lead externalizations and 19 had electrical abnormalities. The patients received follow-up for the study until death, lead discontinuation with fluoroscopy or a new screening in 2013 with fluoroscopy and device interrogation.
“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.
After 1.1 years, 27 of the patients who started the study with externalized conductors had an increased length of externalization by 4 mm. There were 8 more cases of clear externalized conductors and 2 borderline cases after 1.1 years, leading to an incidence rate of 3.7 per 100 person-years.
Among the 276 patients who started out without any electrical abnormalities, 20 developed problems with electrical function with an incidence rate of 7.1 per 100 person-years. Researchers found that patients were more than 4 times as likely to develop electrical abnormalities if they started off with externalized conductors.
According to Mass Device, St. Jude is also conducting an ongoing study over the Riata leads. The study is larger than the Danish one, 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 told Heartwire that his study does not prove a causal relationship between lead externalizations and electrical abnormalities, or whether this issue is a marker for “potentially failing ‘stressed’ leads,” He wrote that “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,”