Deadly heart rhythm halted by noninvasive radiation therapy

Radiation therapy often is used to treat cancer patients. Now, doctors have shown that radiation therapy — aimed directly at the heart — can be used to treat patients with a life-threatening heart rhythm. They treated five patients with irregular heart rhythms, called ventricular tachycardia, who had not responded to standard treatments. The therapy resulted in a dramatic reduction in the number of ventricular tachycardia episodes.

A novel strategy to treat a life-threatening irregular heart rhythm called ventricular tachycardia relies on noninvasive radiation therapy, which is typically directed at cancerous tumors. Noninvasive imaging techniques show irregular heart tissue mapped with the location of misfiring electrical signals, allowing doctors to direct radiation at the specific area of the heart triggering the problem. Pictured is a cross section of a patient’s chest. The problematic heart tissue is highlighted in color.

The patients had not responded to standard treatments and collectively experienced more than 6,500 episodes of ventricular tachycardia in the three months before they were treated with radiation therapy. In ventricular tachycardia, the heart beats exceedingly fast and its chambers often fall out of sync, interfering with blood flow and placing patients at risk of sudden cardiac death. When delivered directly to problematic areas of the heart muscle, the radiation therapy resulted in a dramatic reduction in the number of ventricular arrhythmia events in these patients, as measured by their implanted defibrillators.

An analysis of the patients’ experiences is reported Dec. 14 in The New England Journal of Medicine. There have been two previous cases reported of treating ventricular tachycardia with radiation therapy, but this is the first to do so in an entirely noninvasive process, from imaging to treatment.

“As a radiation oncologist who specializes in treating lung cancer, I’ve spent most of my career trying to avoid irradiating the heart,” said senior author Clifford G. Robinson, MD, an associate professor of radiation oncology. “But I also have been exploring new uses for stereotactic body radiation therapy that we use almost exclusively for cancer.”

At the same time, cardiologist and first author Phillip S. Cuculich, MD, an associate professor of medicine, was looking for new ways to treat ventricular tachycardia in patients who did not respond to conventional treatments. Ventricular tachycardia is estimated to cause 300,000 deaths per year in the U.S. and is the leading cause of sudden cardiac death. Standard therapy includes medication and invasive procedures that involve threading a catheter through a vein into the heart and selectively burning the tissue that causes the electrical circuits of the heart to misfire.

“These patients have defibrillators implanted to act like a paramedic and save their lives if a bad heart rhythm starts up,” Cuculich said. “The device recognizes a dangerous arrhythmia and can deliver a life-saving electrical shock. While it’s wonderful that we can stop people from dying in that situation, the shock can be a traumatic event. Patients understand that they have just avoided death. And when this happens repetitively, often without warning, it can be devastating for patients.”

 

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