BATON ROUGE — Radiation therapy is a common treatment for cancer, but it could also help treat dangerous heart rhythms.

The first clinical trial in humans using proton beam therapy had encouraging results.

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 when a typical pulse should be 60 to 100.

“So I told the wife, I said, 'I think we need to go to the doctor,'" Thomsen said.

Thomsen soon learned he had 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,” Dr. Konstantinos Siontis, a cardiovascular medicine specialist, said.

The condition can even be fatal. It is essentially a short circuit caused by scar tissue on the heart, a common treatment for V-tach is catheter ablation. Doctors enter the heart through blood vessels using a catheter to create tiny scars with heat energy and block the irregular signals.

Thomsen had several of these complex ablations.

"The symptoms came back. I was in the hospital a couple two or three times after that,” Thomsen said.

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

"I got nothing to lose. And the way it was, it wasn't working good,” Thomsen said.

"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,” Radiation oncologist Dr. Kenneth Merrell said.

Unlike a catheter ablation, proton beam therapy is completely noninvasive.

"So 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,” Merrell said.

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

"It made it so it was working,” Thomsen said.