Heart Rhythm: Some Riata deaths linked to high-voltage failures
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In December 2011, St. Jude Medical released a medical device advisory detailing estimates of failures related to its Riata and Riata ST silicone endocardial defibrillation leads. The Sylmar, Calif.-based company added that it was conducting a prospective study to evaluate the incidence and long-term performance of leads with externalized conductors. The FDA soon after upgraded its recall of the leads to Class I, citing potential risk of serious injury or patient death if affected devices malfunction.
Robert G. Hauser, MD, of the Minneapolis Heart Institute Foundation, and colleagues questioned whether electrical malfunctions were at fault. “While much interest has been directed toward externalized conductors, it is an electrical malfunction, such as failure to pace or defibrillate, that poses the greatest risk to patients,” the authors noted. “These malfunctions may not be heralded by detectable signs of failure, and they can result in failure to deliver life-supporting or lifesaving therapy.”
Hauser and colleagues searched the FDA Manufacturer and User Facility Device Experience database on Feb. 10, for deaths associated with Riata, Riata ST and Quattro Secure leads. They included Minneapolis-based Medtronic’s Quattro Secure model 6947 ICD leads for contrast. They estimated that approximately 79,000 Riata and Riata ST implants and 231,000 Quattro Secure leads remain active.
Using the definition of lead-related death as a sudden or unexpected death that was accompanied by evidence of lead malfunction, they identified 133 deaths through the database (71 Riata and Riata ST and 62 Quattro Secure). Twenty percent of those deaths were related to lead failure; 22 were linked to Riata or Riata ST lead failures and five to Quattro Secure lead failures. They found that four Riata and three Riata ST deaths were associated with can abrasions; they wrote that these defects led to short-circuits and failure to deliver therapy. None of the Quattro Secure leads had can abrasions.
“Abnormal high-voltage impedances were the hallmark of catastrophic Riata and Riata ST lead failure, often resulting in failure to defibrillate,” Hauser and colleagues wrote. “Excluding can abrasions, 13 Riata and Riata ST lead-related deaths involved high-voltage conductors as signified by a high or low impedance.”
Based on their analysis, the authors concluded that Riata and Riata ST leads are prone to high-voltage failure. These failures, and not externalized conductors, resulted in 22 deaths, they suggested.
“Electrical shorts are particularly lethal because they may occur abruptly during shock delivery, and thus failure to defibrillate may be the first and only sign of lead failure,” they wrote. They added that because can abrasions are not detected through noninvasive monitoring until they have an electrical abnormality, those monitoring the devices should scrutinize coil-to-can electrograms for artifacts that may be caused by shorts.
They also called for test methods to identify potentially life-threatening defects and alert patients and caregivers, and recommended that hospitals and ICD surveillance clinics design protocols for managing patients with malfunctioning leads.
Hauser and colleagues highlighted limitations to their study, including the lack of clinical data, incomplete data and the fact that many leads were not returned to manufacturers for analyses. They wrote that in the U.S. post-marketing surveillance system, hospitals and physicians under-report adverse events, suggesting that the deaths are underestimated.
“Our findings do not support the prophylactic replacement of normally functioning Riata or Riata ST leads,” the authors emphasized. “Physicians and hospitals are encouraged to return failed leads to the manufacturer for analysis together with detailed clinical information, including pulse generator diagnostic data and electrograms.”