People age 80 and older who get a pacemaker or defibrillator are more likely to die in the hospital after the procedure than younger patients, raising questions about the risks of these implants when used in very elderly people, U.S. researchers said.

Most clinical trials looking at implantable heart devices involve people in their 50s and 60s even though about a fifth of these implants are used in people older than 80, a group often overlooked in medical studies, the researchers said.

As such, little had been known about the benefits of these devices in people older than 80, according to the researchers.

The researchers analyzed data from 26,887 adults with heart failure who underwent implantation of a defibrillator or cardiac resynchronization therapy device in 2004 or 2005.

Younger patients appeared better able to withstand the implants, they said. The study found a death rate in the hospital of 0.7 percent among patients younger than 80, compared to 1.2 percent in those aged 80 to 85 and 2.2 percent in those older than 85.

Patients age 80 and older accounted for nearly 18 percent of the procedures.

"It has become increasingly apparent that certain patient subgroups may not benefit from device implantation," Jason Swindle, who was at Saint Louis University School of Medicine when the study was conducted, reported in the journal Archives of Internal Medicine.

For example, Swindle and colleagues said using implantable cardioverter defibrillators, or ICDs, in patients with kidney failure and in those with advanced heart failure does not help them live any longer.

ICDs detect dangerous heart rhythms and automatically shock an errant heartbeat back into a normal rhythm. Pacemakers correct an abnormally slow heart beat.

Implants that combine features of both, called cardiac resynchronization therapy devices, are used to get the heart to contract in a stronger, more coordinated fashion.

Implantable heart devices, made by companies like Boston Scientific Corp, St. Jude Medical and Medtronic, represent a global market of $10 billion.

While many studies have shown the devices help save lives, the average age of patients in major clinical trials ranged from 58 to 67 years, with few 80-year-olds included.

In general, the researchers said, older people were more likely than younger people to die after an implant. They also found older patients had slightly more complications related to the device procedure.

"Given trends in the demographics of heart failure and the costs of device therapy, additional studies are required to clarify the appropriateness of device implantation in older patients with heart failure, as well as the merits of less invasive options," the team wrote.

Nearly 22 million people worldwide have heart failure, in which the heart struggles to pump blood around the body.