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Radiation therapy examined as future treatment for AF, hypertension
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Early-stage studies indicate that radiation therapy could become a noninvasive alternative treatment for atrial fibrillation and treatment-resistant hypertension.
Researchers presented new data on potential CV applications of radiation therapy, traditionally used for treatment of cancer, at the 56th Annual Meeting of the American Association of Physicists in Medicine.
Radiotherapy for AF
In a feasibility study, researchers tested on four patients a special cardiac MRI to determine whether it is possible to image a beating heart well enough to ensure that radiation therapy for AF would impact the affected tissue and not healthy surrounding tissue.
If the technology comes to fruition, it could replace catheter ablation for treatment of AF, Paul Keall, PhD, professor of medicine at the University of Sydney, Australia, said during a press conference.
“Catheter ablation is a 5-hour procedure involving anesthesia [and] fluoroscopy, and it is invasive, with side effects in about 6% of treatments,” Keall said. “Typically the health care costs [per procedure] are about $50,000. With radiotherapy, potentially we could do this treatment in under an hour noninvasively without additional imaging doses.
“What really enables this technology is the integration of MRI with cancer radiotherapy systems or linear accelerators. The marriage of these two systems enables real-time imaging of the heart, with which we can use to target the atria in the heart to disrupt the electrical signals that are causing the [AF],” Keall said.
Those signals come from the pulmonary vein, so an ablation line at each pulmonary vein antrum would be the target for the radiation therapy, Keall and colleagues wrote in an abstract.
The researchers found that the mean respiratory motion of the target area on MRI was 8.4 mm superior–inferior, 1.7 mm anterior-posterior and 0.3 mm left-right, while cardiac motion was small (<2 mm). That means that real-time MRI tracking of the pulmonary veins is feasible, Keall said.
Radiotherapy for hypertension
Radiotherapy is also being tested as a possible treatment for refractory hypertension, Peter G. Maxim, PhD, assistant professor in the department of radiation oncology at Stanford University School of Medicine and Cancer Institute, said at the press conference.
Maxim and colleagues evaluated whether stereotactic radiotherapy to the renal sympathetic plexus would be safe and effective in pigs.
“We have demonstrated in a preclinical study that radiation therapy for the treatment of high [BP] may be beneficial to a huge patient population,” Maxim said.
Radiation therapy would work by disrupting the signals in the nerves wrapped around the renal arteries which play a critical role in elevated norepinephrine levels, which in turn play a critical role in elevated BP, Maxim said.
At 6 months, all animals survived without evidence of renal dysfunction, skin changes or behavioral changes suggesting discomfort, according to the researchers. During the study period, plasma norepinephrine levels were reduced by a mean of 63% and a median of 73.5%, they found.
For more information:
Ipsen S. Abstract MO-A-BRD-8.
Maxim P. Abstract WE-E-BRE-2. Both presented at: the 56th AAPM Annual Meeting & Exhibition; July 20-24, 2014; Austin, Texas.
Disclosure: Maxim reports receiving research funding from RaySearch Laboratories. Keall reports no relevant financial disclosures.