When Implanted Heart Devices Fail
The Odds -- and Consequences -- of Pacemaker, ICD Breakdowns
April 25, 2006 -- Implanted electronic heart devices can fail. When they do,
bad things can happen -- even to patients whose pacemakers and ICDs are still
ticking, new studies show.
Implanted pacemakers straighten out a wobbly heart rhythm. Implanted
cardioverter-defibrillators (ICDs) jump-start a helplessly fluttering heart.
These state-of-the-art electronic devices save lives. But they're complex
machines that can -- and do -- break down.
What's the risk of this happening? And when manufacturers announce recalls
of problem ICD models, what's the risk of having your implant replaced?
The new studies now open a window on this crucial information. They appear
in the April 26 issue of the Journal of the American Medical
Association, along with an editorial by Bruce L. Wilkoff, MD, director of
cardiac pacing and tachyarrhythmia devices for The Cleveland Clinic.
"These devices have improved in reliability, but people are just now
becoming aware of the fact they are not perfect," Wilkoff tells WebMD.
"This is a small problem that solves a very big problem. Cardiac deaths are
the most common reason people die in the U.S. today. We have an incredibly
successful treatment, but there are costs both in money and in
The Risk of Pacemaker, ICD Failure
William H. Maisel, MD, MPH, director of the pacemaker and device service at
Boston's Beth Israel Deaconess Hospital in Boston, analyzed device malfunctions
reported to the U.S. FDA. He also analyzed pacemaker and ICD implant patients
followed in three different studies in the U.S., the U.K., and Denmark.
"We wondered whether the increasing complexity of these devices has been
associated with decreased reliability," Maisel tells WebMD.
Maisel and colleagues looked at reports of pacemaker and ICD malfunctions
reported to the FDA between 1990 and 2002. During this time, there were 2.2
million pacemakers in use, and more than 415,000 ICDs. There were 17,000
reports of devices that had to be replaced. Hardware problems caused most of
Reassuringly, the annual rate of pacemaker replacement due to malfunction
went down, suggesting these devices became more reliable," Maisel says.
"ICD malfunction declined during the first part of study, from 1994-1998,
then increased from 1998-2002. This suggests that ICDs became less reliable as
they became more complicated."
The usual problem with FDA data is that the FDA adverse-event reporting
system is voluntary. Might missing reports have skewed the data?
"Combined, the studies included patients implanted with several hundred
thousand pacemakers and thousands of ICDs," Maisel says. "The results
were amazingly consistent with the FDA reports. They also showed that the
pacemaker malfunction rate has declined significantly. The ICD malfunction rate
also declined notably from the 1980s to the mid-1990s, but again we saw an
increase in the ICD malfunction rate from 1990 to 1992. The rate of malfunction
for ICDs increased more than fourfold from 1998-2001."