Shock to the Heart


Fears Rise Over Safety Of Implanted Defibrillators

A couple of years ago, my father, who’s now almost 74 and has had congestive heart failure for nearly 10 years, received an implantable defibrillator. His “ejection fraction”—the amount of blood his heart pumps out to his body with each heartbeat—had dropped to a dangerously low level, and studies have shown that patients with such severe heart damage who have these devices implanted have a 24 percent reduced risk of death and a 35 percent reduced risk of being hospitalized with heart failure.

Of course, there’s just one small problem: The defibrillator might not work. These devices are meant to “shock” the patient’s heart back to a steady rhythm if it develops a dangerous arrhythmia, but it’s been hard to miss the headlines recently about some implantable cardioverter defibrillators (ICDs) failing to work as they should. In December, Medtronic, one of the leading manufacturers of ICDs, paid 4 million out of pocket to settle product-liability lawsuits (some 2,600 cases) related to its Marquis line of ICDs, which had potential battery shortage problems. Other Medtronic models have been linked to at least four deaths when they failed to charge properly and didn’t deliver the needed shocks in time.

And in October, Medtronic suspended sales of its Sprint Fidelis lead—a wire that connects the device to the heart—because of the risk of a fracture of the lead inside the heart, causing a massive electrical jolt. These malfunctions had been linked to at least five deaths. (Last April, a study estimated that 40 percent of defibrillator leads fail within eight years—significantly higher than what had been believed.) Other device manufacturers have been plagued by malfunction news and recalls as well.

Not surprisingly, all this news has my dad—as well as the hundreds of thousands of other cardiac patients sporting ICDs inside their chests (about 170,000 implanted in 2005 alone)—a little nervous. If it were just a matter of the ICD not shocking you in time, well, at least you wouldn’t be any worse off than if you hadn’t had the device implanted at all. But a massive electric shock inside your heart when you’re just going calmly about your day is another thing entirely.

So is my dad safe with this thing inside his chest? Is he safer than he was without it? And do these recalls change anything about the need for ICDs?

The use of the term “recall” is part of what has consumers like my father scared. Usually, when a product is recalled—think defective tires or cribs—you need to return it to the manufacturer or otherwise dispose of it right away. After all, it’s not safe to have the recalled tires on your car or your baby in a recalled crib. But that’s not quite the case with ICDs.

“The problem with the term ‘recall’ is that it creates the alarm that a recalled device cannot be left in. That’s not true. In fact there are often more risks involved with extracting a device and re-implanting another than there would be if the device was simply left in and closely monitored. So we recommend instead using the term ‘safety alert’ or ‘advisory,’” explained Dr. Anne B. Curtis, president of the Heart Rhythm Society and professor of medicine at the University of Florida.

So now doctors are trying to rename these alerts “ICD advisories.” And studies have indeed found that it’s probably safer to keep devices listed on these advisories right where they are rather than take them out. A study published in the April 26, 2006, edition of the Journal of the American Medical Association (JAMA) found an 8 percent complication rate (and a 5.8 percent major complication rate) from ICD removal surgery, including two deaths. But for some patients with particular heart conditions, it can be better to take the ICD out—such as those with a problem called hypertrophic cardiomyopathy, which can put more stress on the lead and cause it to break.

For patients who do elect to continue with their ICDs, experts agree it’s important to have these devices regularly checked. “Routine device checks at regular intervals remain the best way for physicians to monitor ongoing device performance in individual patients,” wrote Dr. William H. Maisel of Boston’s Beth Israel Deaconess Medical Center and Harvard Medical School in the April 2006 JAMA report. Wireless monitoring technology embedded in many defibrillators can even be checked for signs of malfunction via the Internet.

“Despite this newly recognized increase in ICD malfunction replacement rate, ICDs effectively reduce mortality in specific high-risk populations,” Maisel added. “These devices have prevented innumerable sudden deaths, and they remain an important therapy for patients at high risk for sudden cardiac death.”

In other words—don’t panic. Consult with your doctor and your device manufacturer about monitoring options and any particular conditions you may have that could place you at special risk of problems. But also understand that overall, ICDs have prevented and continue to prevent countless sudden cardiac deaths every year.

In the very near future, doctors may also be fine-tuning just who gets these implanted devices. That’s because as many as one-third of people with ICDs don’t actually need them. A test for heart-rhythm abnormalities called microvolt T-wave alternans has been shown in studies to help identify people who can benefit from ICDs, and those who might not.

Scientists at the University of Michigan, for example, found that patients who met the current guidelines for receiving an ICD, but had normal T-wave alternans (MTWA) results, were no less likely to die during the follow-up period than people with similar test results who hadn’t gotten ICDs. On the other hand, people with abnormal MTWA results were 55 percent more likely to die if they did not receive a defibrillator than those who did get one.

“This is the first study to demonstrate that a subset of patients who meet current criteria for defibrillator placement may not benefit at all from ICDs,” said Dr. Paul Chan, senior author and a fellow in cardiovascular medicine at the University of Michigan Medical School. “Use of the MTWA test could truly help us tell which ICD candidates will benefit most.”

About the Author

Gina Shaw is the medical writer for The Washington Diplomat.