Although pacemakers and implantable cardioverter-defibrillators (ICDs) sustain and save many lives and have a low malfunction rate, their performance should be monitored, especially ICDs, which have a significantly higher malfunction rate than pacemakers, according to two studies in the April 26 issue of JAMA.
Pacemakers and ICDs are two of the most clinically significant and complex medical innovations of the past century. Yet, despite millions of implants worldwide and their increasingly frequent use, surprisingly little is known about their reliability and the rate at which they malfunction, according to background information in the article. Because pacemakers and ICDs represent "life-sustaining" therapies for many patients, the U.S. Food and Drug Administration (FDA) requires manufacturers to submit annual reports detailing the number of device implants and malfunctions that have occurred.
William H. Maisel, M.D., M.P.H., of Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, and colleagues from the U.S. FDA analyzed the manufacturer's pacemaker and ICD annual reports for the years 1990-2002 to determine the reported number, rate, and reasons for pacemaker and ICD malfunctions and to assess trends in their performance.
The researchers found that from 1990 to 2002, 2.25 million pacemakers and 415,780 ICDs were implanted in the United States. During this period, 17,323 devices (8,834 pacemakers and 8,489 ICDs) were explanted due to confirmed malfunction. The average annual total device malfunction replacement rate was 6.8 per 1,000 device implants. Overall, the annual average ICD malfunction replacement rate was significantly higher than the pacemaker malfunction replacement rate (20.7 vs. 4.6 replacements per 1,000 implants). Battery/capacitor abnormalities and electrical issues accounted for half of the total device failures. Sixty-one deaths (30 pacemaker patients, 31 ICD patients) were attributable to device malfunction.
The annual pacemaker malfunction replacement rate decreased significantly during the study, while the ICD malfunction replacement rate, after decreasing from 1993 to 1996, increased markedly during the latter half of the study. More than half of the reported ICD malfunctions occurred in the last 3 years of the study.
The researchers write that because ICDs are substantially more sophisticated than pacemakers, it is not surprising that they have a higher device malfunction replacement rate.
"Routine device checks at regular intervals remain the best way for physicians to monitor ongoing device performance in individual patients. Technological advances that allow for remote wireless monitoring or monitoring via the Internet may become increasingly important. Despite this newly recognized increase in ICD malfunction replacement rate, ICDs effectively reduce mortality in specific high-risk populations. These devices have prevented innumerable sudden deaths, and they remain an important therapy for patients at high risk for sudden cardiac death," the authors write.
(JAMA. 2006;295:1901-1906. Available pre-embargo to the media at www.jamamedia.org.)
Editor's Note: The study was funded by the FDA. Dr. Maisel is a paid consultant for the FDA.
ICD Malfunction Rate Fluctuates Over Past 6 Years
A meta-analysis of data from 3 international registries that includes information on pacemaker and ICD implants suggests that the ICD malfunction rate increased more than 4 fold from 1998 to 2002, but then decreased substantially from 2002-2004, according to another study in this issue of JAMA.
William H. Maisel, M.D., M.P.H., of Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, conducted the meta-analysis of relevant pacemaker and ICD registries to determine malfunction rates and trends. Three registries meeting the selection criteria were identified -- one registry from North America, one from Denmark, and one from the United Kingdom -- and included 2.1 million pacemaker person-years and 14,821 ICD person-years of observation. The annual number of patients with pacemakers and ICDs at risk of device failure and the annual number of generator malfunctions (1983-2004 for pacemakers, 1988-2004 for ICDs) were determined.
There were 2,981 pacemaker and 384 ICD generator malfunctions. Pacemaker reliability improved markedly during the 1980s and the pacemaker malfunction rate remained low during the remainder of the study. Implantable cardioverter-defibrillator reliability improved during the first 10 study years. From 1998-2002, however, the ICD malfunction rate increased more than 4-fold, before decreasing substantially in the latter 2 years of the study. Overall, the average annual ICD malfunction rate was about 20-fold higher than the pacemaker malfunction rate (26.5 vs. 1.3 malfunctions per 1,000 person-years). Battery malfunctions were the most common cause of device failure.
"Given the number of pacemaker and ICD malfunctions, and the transient but notable increase in ICD malfunction rate, ongoing surveillance of pacemaker and ICD performance is clearly required. Active device registries, as used in this study, can provide important insights into device performance trends," the author writes. "Efforts should be directed at improving the reliability of these important devices."
(JAMA. 2006;295:1929-1934. Available pre-embargo to the media at www.jamamedia.org.)
Editor's Note: Dr. Maisel is an FDA consultant, although this study was conducted without FDA financial support. There are no additional financial disclosures.
Pacemaker and ICD Malfunction -- An Incomplete Picture
In an accompanying editorial, Bruce L. Wilkoff, M.D., of Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, comments on the studies in this issue of JAMA on pacemakers and ICDs.
"These investigations contribute important new data to the information mosaic involving pacemakers and ICDs and should enable clinicians and patients to make better informed decisions about these devices. However, these studies involve large patient groups and not individuals. Each patient and each device system pose unique issues. The information provided by these studies provides a landscape that should help physicians, patients, manufacturers, and regulators make the best possible decisions for individual patients and for society."
(JAMA. 2006;295:1944-1946. Available pre-embargo to the media at www.jamamedia.org.)
Editor's Note: Dr. Wilkoff reports that he served as a consultant for, and received research and institutional programmatic support from, Medtronic, Guidant, and St. Jude Medical.
Materials provided by JAMA and Archives Journals. Note: Content may be edited for style and length.
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