By LINDSEY TANNER, AP Medical Writer
CHICAGO (AP) - A new study has linked widely used, more sophisticated heart defibrillators with a slightly increased risk of hospitalization and death.
The study led by a Cleveland Clinic researcher questions the value of a costly pacemaking feature in the newer defibrillators similar to the kind of device implanted in Vice President Dick Cheney last year.
It doesn't challenge the benefit of implanted defibrillators, which zap rapidly irregular heartbeats back to normal. The devices have been shown to prevent cardiac arrest.
Most of the newer model defibrillators also feature built-in pacemakers, which help maintain a normal heart rhythm. But most patients who need defibrillators are likely only to need less sophisticated devices equipped with a backup pacemaker, the research suggests. The backup pacemaker stimulates the lower heart chamber when the beat becomes too slow.
The researchers found increased risks with newer models featuring pacemakers that supply electrical impulses to both upper and lower heart chambers.
The newer, dual-chamber devices can be programmed to continuously regulate the heartbeat -- even though most people who get them don't need that much help, said researcher Dr. Bruce Wilkoff of the Cleveland Clinic.
Many doctors assumed the extra help would be beneficial for defibrillator patients, since previous research showed that stand-alone dual-chamber pacemakers helped other heart patients do better, Wilkoff said during a Thursday teleconference.
But in the study, within one year of getting the implants, 26.7 percent of the dual-chamber patients died or were hospitalized with heart failure, compared with 16.1 percent of patients who got only backup pacemaking help.
The researchers halted the study early because of the poor results, which could translate into thousands of hospitalizations or deaths worldwide each year.
"Bigger is not always better; more sophisticated is not always an improvement," Wilkoff said.
An estimated 80,000 defibrillators have been implanted worldwide this year. While about three-fourths of them are the more sophisticated devices, only about 5 percent of patients need the extra help, Wilkoff said.
The study, which involved 37 medical centers, appears in the Dec. 25 issue of the Journal of the American Medical Association.
A study earlier this year suggesting that millions of heart patients could benefit from defibrillators raised concerns about the costs. The new study could help fine-tune which patients could get by with the less expensive models, said Dr. Sidney Smith, the American Heart Association's chief science officer.
Smith noted the new study included many patients with mild heart failure and didn't address whether dual-chamber devices would be better than less costly ones for the sickest heart patients.
Wilkoff's research involved 506 people with heart disease or previous heart attacks, though none required continuous pacemaking help. All had defibrillators containing the more sophisticated pacemakers, but the continuous dual-chamber action was activated in only half the patients.
Wilkoff said dual-chamber devices may be more risky because continuously stimulating the right ventricle, one of the heart's lower chambers, may make the pumping action less efficient.
Defibrillators with pacemaking features are generally small, flat metal devices that come in different shapes and sizes. The devices alone can cost between $16,000 and $25,000. The more sophisticated ones are at the upper end of that range and also can cost about $5,000 extra to implant, Wilkoff said.
The sophisticated devices have other benefits, including helping doctors track heart function, but the results suggest that fewer should be used, Wilkoff said. In most cases, those that are implanted should be programmed to provide only backup pacemaking help, he said.
Michael Coyle of St. Jude Medical Inc., which made the devices used in the study and funded the research, said the results show "that careful attention must be paid to the programming of pacemaker functions" to minimize effects in defibrillator patients who don't need the extra help.
Johns Hopkins' Dr. David Kass, a paid consultant for Guidant Inc., which makes similar devices, said in a JAMA editorial that more data are needed to determine if the "simpler solution" is best.