Radiation therapy is a common treatment for cancer, but could it also help treat dangerous heart rhythms?

Experts at Mayo Clinic recently completed the first clinical trial in humans using proton beam therapy, a type of radiation, to treat patients with potentially life-threatening arrhythmias. And they say initial results are encouraging.

Watch: Using proton beam therapy on the heart

Journalists: Broadcast-quality video (2:11) is in the downloads at the end of this post. Please courtesy: "Mayo Clinic News Network." Read the script.

When Roger Thomsen had his first episode several years ago, the 69-year-old retired repairman felt lightheaded. He checked his pulse. His heart rate was around 200 beats per minute. A typical pulse is 60 to 100.

"I told the wife, I said, 'I think we need to go to the doctor,'" Roger says.

Roger soon learned he has a heart condition called ventricular tachycardia, also called V-tach or VT.

"Ventricular tachycardia is an abnormal rapid rhythm arising from the bottom chambers of the heart that can cause significant symptoms to patients," says Dr. Konstantinos Siontis, a Mayo Clinic electrophysiologist.

It can even be fatal. Essentially a short circuit caused by scar tissue on the heart, a common treatment for V-tach is a catheter ablation. Doctors enter the heart through blood vessels using a catheter to create tiny scars with heat energy and block the irregular signals. Roger had several of these complex ablations. 

"The symptoms came back. I was in the hospital a couple two, three times after that," Roger says.

So a couple of years ago, Roger enrolled in a clinical trial at Mayo Clinic. He would be one of the first of a handful of patients with V-tach to have a precise form of radiation typically used in cancer treatments, called proton beam therapy, used on the heart.

"Got nothing to lose. And the way it was, it wasn't working good," Roger says.

"Proton beam is a unique type of radiation that's actually a charged particle. It's able to deliver the energy of radiation at a specific depth or target in tissue without any exit dose beyond," says Dr. Kenneth Merrell, a Mayo Clinic radiation oncologist.

"With catheter ablation, there are certain areas within the heart that can be difficult to access," says Dr. Siontis.

And unlike a catheter ablation, proton beam therapy is completely noninvasive.

"The patient does not require anesthesia. They can walk into the treatment area and walk out the same day within about 30 minutes to an hour of completing the treatment," says Dr. Siontis.

It's nearly a year since Roger has had an abnormally rapid heart rhythm.

"It made it so it was working," Roger says. Which is the type of result the research team at Mayo says could bring new hope for some patients with V-tach.

"This was an encouraging first step," says Dr. Siontis.

While more study is needed, researchers are excited for the future. "Most likely, this will be another tool in the tool belt for us to use in patients," says Dr. Merrell.

The full results of the clinical trial using proton beam therapy to treat VT have yet to be published. The team at Mayo plans to present them later this year.

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