Chicago A new study has linked widely used, more sophisticated heart defibrillators with a slightly increased risk of hospitalization and death.
The study questions the value of a costly pacemaking feature in the newer defibrillators similar to the device implanted last year in Vice President Dick Cheney.
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 models 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 the 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, because previous research showed stand-alone dual-chamber pacemakers helped other heart patients do better, Wilkoff said Thursday.
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.
The study appears in the Dec. 25 issue of the Journal of the American Medical Assn.
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 cheaper models, said Dr. Sidney Smith, the American Heart Assn.'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 may make the pumping action less efficient.
Defibrillators with pacemaking features are generally small, flat metal devices.
The devices alone can cost between $16,000 and $25,000. The more sophisticated ones are at the upper end of that range and 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.