People with the most common pacemaker (search) types are more likely than similar people without pacemakers to die from or be hospitalized for gradual heart failure (search), sometimes within six months, according to a large study confirming doctors' belief the life-saving devices actually harm some patients.
Experts say the tens of thousands of patients with pacemakers should not panic. They should have the pacemaker checked every several months, contact the doctor if heart failure symptoms such as shortness of breath and fatigue develop, and possibly have the pacemaker's timing adjusted.
For some patients, replacing the pacemaker with a new type designed to prevent damaging strain on the heart's key pumping chamber could prevent heart failure, said Dr. Michael Sweeney, director of heart devices implantation at Brigham and Women's Hospital in Boston.
"The way we've practiced cardiac pacing for the last three decades must be abandoned," said Sweeney, who was not involved in the study.
About 175,000 pacemakers are implanted in this country each year.
Sweeney said about 90 percent stimulate one or two of the heart's right chambers to contract when beating slows down, but don't allow the four chambers to beat in the same order as a healthy heart. That out-of-sync beating puts extra stress on the heart's main pumping chamber, the left ventricle, and in some patients causes congestive heart failure, in which the heart gradually stops pumping effectively.
In the study of more than 23,000 New Jersey hospital patients, those with a pacemaker that stimulated both the right chambers of the heart had a 36 percent higher risk of hospitalization or death from heart failure than a comparison group of people in similar health but without a pacemaker. Among patients who had a pacemaker implanted that only stimulated one right chamber, there was a 59 percent higher risk.
"I think it makes sense that when you're making the heart contract in an abnormal way, you're increasing risk of developing heart failure," said the lead investigator, Dr. Ronald Freudenberger, director of the Department of Heart Failure and Transplant Cardiology at Robert Wood Johnson Medical School in New Brunswick.
The study, in the March issue of The American Journal of Cardiology, was based on hospital records and death certificates from a huge database of New Jersey patients.
From 1997 through 1999, 11,426 patients with no history of heart failure had pacemakers implanted at New Jersey's 85 hospitals. Freudenberger's team combed the next three years of records for those patients and a matched group without a pacemaker. All had an average age of 75 and were similar in race, sex and prevalence of some heart-related conditions, such as high blood pressure and past heart attack.
"I think the paper's important because it adds another piece of evidence to a now almost completely filled-in picture," showing the need for pacemakers to make hearts beat in a normal pattern, Sweeney said.
Dr. Stephen Hammill, head of the Mayo Clinic's heart rhythm service and president of the Heart Rhythm Society, said a smaller study following patients with different types of pacemakers found their risk of heart failure rose the more the device kept the lower heart chambers out of sync.
Hammill said a new pacemaker that stimulates both the lower heart chambers appears to help the heart pump blood more efficiently and limits fluid buildup in the body, a dangerous symptom of heart failure.
Sweeney is running a study of such pacemakers — which cost about $10,000, roughly double other devices, excluding hospital and surgeon fees — to prove whether they limit heart failure development. He expects results in about three years.
Dr. Anne Bolger, a cardiologist and professor of clinical medicine at University of California-San Francisco, said because hospital discharge reports exclude many details on patients' health, some unseen difference between the two patient groups — such as family history of heart failure — could have affected the study's outcome. But she said because so many people were in the study, it could prompt research on how best to match pacemaker types to individual patients.