TUESDAY, April 24 (HealthDay News) -- Life-saving implantable pacemakers or defibrillators pose a risk for developing deadly infections, a new study suggests.

More than 4.2 million people in the United States had a permanent pacemaker or defibrillator implanted between 1993 and 2008, and heart-device infections increased 210 percent during that time, according to the study.

"These infections tend to occur in very vulnerable patients who have other medical conditions that may partially contribute to developing an infection," said study author Dr. Andrew Wang, a cardiologist at Duke University Hospital in Durham, N.C.

Pacemakers help control abnormal heart rhythms. Defibrillators use shocks to help manage life-threatening heart-rhythm abnormalities that can cause sudden cardiac death.

The findings appear in the April 25 issue of the Journal of the American Medical Association.

Heart-device-related infections, which are caused by bacteria, grow more dangerous when they spread to the heart valve or other organs. Treating these infections requires prolonged antibiotic therapy, removal of the device and possibly device reimplantation, but repeat surgeries also can be risky. Hospital charges for this complication are at least $146,000, the authors said.

Researchers set out to determine how common and lethal these infections are, and which heart patients are at greatest risk. Using data from 61 centers in 28 countries, they found that of 2,760 people with an infection of the heart's lining or valves (endocarditis), an implantable heart device was the cause in 177 cases.

Endocarditis carries an increased risk of death compared to other heart-device-related infections.

Overall, device-related infections were more common in older men, who were about 71 on average. The infection reached the heart valve in 66 people in the study. Other complications included heart failure and persistent blood infections.

Factors such as longer hospital stays and medical procedures unrelated to the implantable device also increase the likelihood of infection. Health-care-associated infection was seen in 81 of the patients with an implantable cardiac device, the study showed.

Device removal sometimes carries more risks than benefits. "It comes down to a decision as to whether the device infection can be cleared without having to remove it," Wang said. "In general, most experts feel removing the device is necessary."

Infections are more likely to be fatal when the valve is involved, but those people who have the infected device removed at the time of the initial infection do live longer, the study showed.

Preventing these infections is a challenge, Wang said. Knowing the signs and symptoms can help identify device infections early. There may be skin inflammation if it is an infection of the pacemaker leads or wires. There also are systemic signs of infection, including low-grade fever, weight loss and night sweats. Earlier detection lowers risk of infection spreading to a valve, but some strains of bacteria are stealthier than others, he said.

This risk is "real and sobering," said Dr. Gregory Crooke, a cardiac surgeon at Maimonides Medical Center in New York City. "It is not insignificant. Catch it as early as possible and intervene as early as possible."

Hardware removal is preferable to antibiotics, Crooke said.

"Removal of the infected device is simpler than open heart surgery, which is what will be needed if the infection spreads to the valve," he said.

Crooke said prevention starts when the device is first implanted. Doctors need to take all precautions to make sure it is done in a sterile and hygienic environment.

Dr. Ranjit Suri, director of the Electrophysiology Service and Cardiac Arrhythmia Center at Lenox Hill Hospital in New York City, agreed. "We should do everything in our power to prevent these infections starting with using pristine sterile techniques," he said.

"We should try and limit our exposure to pathogens in the hospital by prevention techniques, including hand washing and shortening a patient's stay in the hospital," Suri said. "The longer they stay in the hospital, the higher their risk of infection."

If a patient does develop an infection, "there is clearly a survival advantage with removal of the whole system," Suri added. "Antibiotics themselves won't sterilize the infection."

More information

Learn more about bacterial endocarditis at the American Heart Association.