LONDON (Reuters) - Kidneys transplanted from victims of heart attacks and other cardiac deaths are just as good as those from brain-dead patients and could offer a valuable extra source of donor organs, British scientists said on Thursday.

The researchers said fears that kidneys from heart death victims may be inferior for transplants are unfounded and they should be treated as equal to kidneys from brain-dead donors.

"The shortage of donor organs remains one of the key challenges faced by the international transplant community," said Andrew Bradley of Addenbrooke's Hospital in Cambridge, who led the study. "In view of our findings, cardiac-death donors represent an extremely important and overlooked source of high-quality donor kidneys."

Around 80,000 people in the United States and 7,000 people in Britain are currently waiting for a kidney donation.

Since the 1970s, the majority of organs for transplantations in Britain and other developed nations have been from brain-dead donors — people who suffered massive, irreversible brain injuries and needed artificial life support to stay alive.

But in the last decade there has been a fall in the numbers of these donors — partly as a result of better care of patients with severe head injuries and fewer deaths from road accidents.

In Britain, the number of cardiac-death donors has risen to 32 percent of all donations in 2009 from just three percent in 2000, the researchers said in their study in the Lancet journal.

Bradley's team looked at the quality of kidneys after cardiac death versus brain death using data from Britain's transplant registry. They found no differences in how well kidneys from cardiac-death donors or brain-death donors were accepted in first-time recipients, and no differences in kidney function in one to five years after the transplant.

"Cardiac-death donor kidneys last as long and work as well as brain-death donor kidneys and should be regarded as comparable," said Dominic Summers of Cambridge University's department of surgery, who also worked on the study.

He said the research should encourage more use of organs from heart death victims around the world.

"Cardio-death donation has started to be used in the United States, the UK, the Netherlands and Australia. Hopefully this work will encourage further expansion in these countries and demonstrate that it is a hugely valuable source of organs for the rest of the world," he told Reuters.

In a commentary on the study in the Lancet, Peter Morris of Britain's Centre for Evidence in Transplantation said the study's findings were "persuasive" and showed that using cardiac-death donor organs was "an acceptable practice."

"Potential recipients of kidneys from cardiac-death donors can be reassured that their transplant outcome is not jeopardised by the source of the kidney," he added.