American researchers have reported some success using radiation to treat patients experiencing irregular heartbeats.

The highly experimental treatment has only been tried on a small number of patients. But doctors are preparing to carry out the first major study to test its effectiveness on large groups of people.

Scientists working on the treatment say early research suggests radiation may reprogram misfiring heart cells to control heartbeats like younger, healthier cells do.

An irregular heartbeat, known medically as ventricular tachycardia, is a major cause of sudden heart attacks worldwide. In the United States, the condition is blamed for about 300,000 deaths each year.

Treating the condition with radiation is extremely unusual. Even doctors treating cancer patients are trained to avoid targeting the heart. There is concern that the radiation could cause additional harm. But doctors studying the treatment say they have seen such good results they are looking forward to expanding their research.

The scientific team says the treatment would be targeted at patients with life-threatening irregular heartbeats who have tried other methods without success.

The study will attempt to see whether a one-time radiation treatment can be a safe and effective way to treat irregular heartbeat patients who have not been helped by other methods.

Dr. Stacey Rentschler is a developmental biologist who treats heart patients at the Washington University in St. Louis. She told The Associated Press the treatment "may actually rejuvenate sick tissue." Rentschler called that result "pretty exciting."

One patient who agreed to receive the experimental treatment is Jeff Backus of Louisville, Kentucky. He was unable to solve his heart problems with other treatment methods.

Backus had already gone through a lengthy operation to keep his heart beating normally. Doctors put a piece of equipment, called a defibrillator, inside his body to assist his heart when needed. But Backus' poor health continued. He would sometimes pass out and awaken to severe chest pain. Backus said the defibrillator had to save him by shocking his heart back into normal beating.

"You're always in the back of your mind thinking, ‘Is it going to happen?'" Backus told the AP. He decided to try the experimental radiation treatment in February. So far, he is doing well, and the method, he said, "gave me some hope."

The heart's electrical system normally makes it beat at a rate anywhere from 60 to 100 times a minute. Ventricular tachycardia is a super-fast heartbeat that affects the organ's ability to pump blood. The condition can develop after damage from a past heart attack.

The main treatment method involves doctors putting small catheters inside the heart to identify and burn misfiring tissue, which can block bad signals. Some patients, however, are too sick to receive the catheter treatment. And for others, like Backus, the problem often returns.

The idea for the radiation treatment came from Dr. Phillip Cuculich, a heart specialist at Washington University. Cuculich teamed up with Dr. Clifford Robinson, who specializes in exact targeting of cancer while avoiding nearby healthy tissue.

Robinson said he was never aiming for the heart during cancer treatments and instead always tried to miss the organ. But he agreed to try and warned patients about possible long-term risks. He said his first patient told him, "You're concerned about something that might happen 10 or 20 years from now? I'm worried about tomorrow." "That was really eye-opening," he added.

Cuculich and Robinson reported their first successes in 2017 and 2019. Experiments with small numbers of severely sick patients showed major improvement. They say some patients are doing well up to six years later.

The treatment has not been approved by the U.S. Food and Drug Administration. But Cuculich and Robinson have received permission to treat about 80 people on a case-by-case basis. The team has also taught the method to many hospitals in the U.S. and other countries that have agreed to try it.

I'm Bryan Lynn.

The Associated Press reported on this story. Bryan Lynn adapted the report for VOA Learning English.

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rejuvenate – v. to make someone of something look or feel young and energetic again

exciting – v. making you feel very excited and enthusiastic

short-circuit – v. to cause a fault in an electrical connection

catheter – n. a long, very thin tube used to take liquids out of the body