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ICD and Pacemaker Malfunctions

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December 27, 2006

ICD and Pacemaker Malfunctions

  1. Hugh Calkins, MD

Two studies tracked temporal trends in malfunction rates.

  1. Hugh Calkins, MD

Pacemakers and implantable cardioverter-defibrillators (ICDs) are becoming much more prevalent, prompting Maisel and colleagues to review FDA annual reports of malfunctions submitted by device manufacturers from 1990 to 2002. Malfunctions were defined as situations in which a device was explanted after an observed malfunction, returned to the manufacturer, and then confirmed by the manufacturer to be malfunctioning. Deaths were attributed to device malfunction only if the malfunction immediately led to a witnessed death and the manufacturer subsequently confirmed the malfunction.

Of 2.25 million pacemakers and 415,780 ICDs implanted, 8834 and 8489, respectively, malfunctioned. Most malfunctions (80%) were due to hardware abnormalities, most often electrical issues or battery/capacitor problems. Device software was implicated in only 4% of malfunctions. For pacemakers, the rate of malfunction-related replacements per 1000 implants peaked at 9.0 in 1993 and then declined to a nadir of 1.4 in 2002; for ICDs, the rate peaked in 1993 at 38.6, hit a nadir in 1996 at 7.9, and eventually rebounded to 36.4 in 2001. Overall, the annual rate of malfunction-related replacements was significantly higher for ICDs than for pacemakers (20.7 vs. 4.6 per 1000 implants). Sixty-one deaths were attributed to device malfunctions (30 from pacemakers, 31 from ICDs); device-related mortality risk was significantly higher with ICDs than with pacemakers (risk ratio, 5.6).

In a separate meta-analysis, Maisel synthesized malfunction data from three prospective device registries: one each from North America (1974–1993), Denmark (1994–2004), and the U.K. (1977–2004). Collectively, the registries tracked about 478,000 pacemaker and 21,000 ICD implantations, and documented 2981 pacemaker and 384 ICD generator malfunctions. The pacemaker malfunction rate declined dramatically during the 1980s, and the reduced rate was sustained. In contrast, the ICD malfunction rate declined gradually through 1998, increased fourfold from 1998 to 2001, and declined again through 2004. Overall, the mean annual malfunction rate was dramatically higher for ICDs than for pacemakers (26.5 vs. 1.3 per 1000 person-years). Malfunctions were most often caused by battery failures.

Comment

These studies document the sustained reliability of pacemakers (a mature technology) and somewhat troubling, but possibly temporary, increases in malfunction rates for ICDs (a newer technology). ICDs are getting smaller and more sophisticated, so the increase in malfunctions is not surprising. Among the other study limitations noted by an editorialist are that the analyzed malfunctions did not include the “weak link” in pacemaker and ICD systems — namely, the lead, which is prone to insulation breaks and stress fractures, as well as to deterioration related to changes in a patient's cardiac condition. Furthermore, this study might have underrepresented even the types of malfunctions that were considered, given the strict criteria used for reported malfunctions. Careful, complete, ongoing monitoring of all aspects of device performance is obviously critical. Toward that end, manufacturers, the FDA, and professional societies are working to develop guidelines for the monitoring and management of device malfunctions (e.g., see recommendations from the Heart Rhythm Society). For now, we must remember that although pacemakers and ICDs are complex devices that can malfunction, they have saved an enormous number of lives, and their overall benefits are well-established.

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