Bacteria Bedevil Heart Implants
MONDAY, Aug. 27, 2001 (HealthDayNews) -- Potentially deadly bacteria can hide undetected in heart implants, evading scans and blood tests, new research shows.
A study by Duke University cardiologists says Staphylococcus aureus infections of pacemakers and other permanent rhythm-correcting devices often don't cause symptoms or appear on chest scans. What's more, they say people who suffer these infections and fail to have the devices removed are almost three times more likely to die in the near term than those who receive new implants.
Ideally, doctors would use prolonged doses of antibiotics to treat heart patients with staph infections. However, that approach offers no guarantee that it will rid the devices of germs. So while removing and replacing cardiac implants is costly and carries a small but definite risk of death, it's the best option when the source of the infection is the device itself, or when the source isn't known or when the infection persists after treatment, the researchers say.
Cardiologists have long understood that pacemakers and implantable cardioverter-defibrillators (ICDs,) -- like the rhythm-correcting device Vice President Dick Cheney relies on to keep his heart beating in good time -- are prone to serious and sometimes fatal infections. As many as one in five pacemaker patients and 1.3 percent of people with ICDs suffer these complications, studies show. In 1998 alone, 170,000 pacemakers and 26,000 ICDs, were installed in this country, reports the American Heart Association.
What's alarming in the latest work is that these infections may be more concealed than experts previously suspected, says Dr. Timothy J. Gardner, chief of cardiothoracic surgery at the University of Pennsylvania. The findings appear in the Aug. 28 issue of the journal Circulation: Journal of the American Heart Association.
Gardner, a spokesman for the American Heart Association, says the results raise a difficult dilemma for practitioners: When can patients with staph infections safely be treated with antibiotics and when should their implants be removed?
"If you had a young, healthy person in whom you felt there was an infected unit, it would probably be worthwhile taking the thing out, putting in a temporary unit, then putting a new one in" after a course of antibiotics to kill of the germs, Gardner says. "But if someone is quite elderly, switching could be a big risk. It seems like a fairly drastic move if you're not sure they have a life-threatening infection."
Not to mention expensive. Each implant procedure costs $20,000 or more, including the price of the hardware, doctors' fees and hospital care.
Still, the Duke researchers say if the source of staph in the bloodstream is unclear, there's a good chance the implant is contaminated. "At that point we would advocate that [the implant] was probably infected, and it should come out," says lead study author Dr. Anna Lisa Chamis, a Duke cardiology fellow.
Chamis and her colleagues followed 33 adults with staph infections of the blood, or bacteremia, who had received either pacemakers, ICDs or both.
Fifteen, or 45 percent, were found to have staph infestation of their implants and another 25 percent had possible infections. While nine of the confirmed cases had none of the telltale signs of infection in the tissue around the device, when cultures of the area were taken, five proved positive for the microbes.
A dozen of the staph infections appeared within a year of implantation, considered "early," and in nine cases the germs spread to the devices. The remaining 21 cases were "late," since they occurred more than a year after implantation. Among those, six were confirmed to have spread to the implant and nine more may have.
Doctors took out the implants in 12 of the 33 patients with staph infections, treating the rest with antibiotics alone. But those who kept their implants were nearly three times as likely to die over the six-year study as those who had them removed and replaced with new, sterile devices. Some of those deaths were related to infection.
Overall, the researchers say the implants themselves were the likely source of staph infection in about 18 percent of cases, and the devices were more likely to be the culprit in those with early infections .
The study only looked at patients with Staphylococcus aureus, a common hospital-acquired infection that can cause pneumonia, sores and other ailments. Yet the researchers say that germ and others may be contaminating other implanted devices such as catheters and stents.
What To Do: For more on ICDs, try the American Heart Association. To learn more about pacemakers, check About.com.
