United States: A new study suggests that radiation therapy, a conventional approach used against cancer, may help treat patients with a life-threatening abnormal heart rhythm called ventricular tachycardia.
Cardiologists and radiation oncologists at Washington University School of Medicine in St. Louis repurposed the use of radiation therapy.
The research team discovered that low-dose radiation therapy appears to improve heart function in various forms of heart failure. This results after analysing the cardiac effects of radiation in a small number of individuals and modelling the effects of low-dose radiation in mice with heart failure.
The study, published in the journal Med, suggests that low-dose radiation therapy improves heart function, at least in part, by reducing the number of inflammatory immune cells in the heart muscle.
“The radiation therapy used to treat ventricular tachycardia is targeted to a specific location in the heart; however, a large portion of the rest of the heart gets a low-dose exposure,” stated co-senior author and cardiologist, Mr. Ali Javaheri, Assistant Professor of medicine.
“We wanted to understand the effects of that low-dose radiation on these patients’ hearts. There was concern that it could be harmful to overall heart function, even though it treats dangerous arrhythmia. We were surprised to find the opposite: Heart function appeared to be improved after radiation therapy, at least in the short term,” Mr. Javaheri added.
A group of nine patients with ventricular tachycardia were evaluated with cardiac MRI before and after radiation treatment, with the MRIs showing improved heart function soon after radiation. This enhancement was particularly notable in the left ventricle, responsible for supplying blood to the entire body.
The positive effects were observed within days after treatment, so it was deemed unlikely to be due to the reduction of the arrhythmia, which happens more gradually over the ensuing weeks and months.
Moreover, the researchers extended their study to mice with heart failure induced by three different causes. The mice treated with low-dose radiation exhibited improved heart function, especially in the left ventricle, similar to human patients.
In mice with progressive heart failure, radiation therapy increased the survival of the animals, indicating that improvements in heart function translated to improved survival.
The researchers found that the failing mouse hearts that received radiation had reduced fibrosis (scar tissue) and reductions in cardiac macrophages, a type of immune cell that can drive inflammation in the heart.
In general, the irradiated hearts had fewer cells that proliferate quickly such as immune cells and fibroblasts, which tend to contribute to worsening heart failure. On the other hand, normal cardiac muscle cells generally do not divide often.
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