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Radiation therapy may improve heart function by reducing inflammatory immune cells
In diseased hearts, low-dose radiation therapy appears to improve heart function. This research by Washington University School of Medicine in St. Louis could lead to new treatments for heart failure. Two mouse hearts with heart failure are shown. The right side of the heart received radiation treatment and is beating more efficiently than the left side, which did not receive treatment.Credit: Attila Kovacs
Cardiologists and radiation oncologists at Washington University School of Medicine in St. Louis recommend radiation therapy (a strategy typically used for cancer) to treat patients with life-threatening abnormal heart rhythms called ventricular tachycardia. pioneered the use of
Now, after studying the cardiac effects of radiation in these small numbers of patients and modeling the effects of low-dose radiation in heart failure mice, the research team shows that low-dose radiation therapy improves cardiac function in a variety of ways. I discovered that it seems like. of heart failure. Although more studies are needed before researchers can evaluate this treatment for patients with heart failure, the study suggests that the effects of radiation on damaged hearts with high levels of inflammation may be more diverse than previously understood. , suggesting that it could possibly be beneficial.
The study, published Nov. 28 in the journal Medical Science, suggests that low-dose radiation therapy improves heart function, at least in part, by reducing the number of inflammatory immune cells within the heart muscle. .
“Radiotherapy used to treat ventricular tachycardia targets specific locations within the heart. However, most of the rest of the heart receives low-dose exposure,” said co-senior author and said Ali Javaheri, MD, specialist and assistant professor of medicine. “We wanted to understand the effects of low-dose radiation on patients’ hearts. Even when treating dangerous arrhythmias, we were concerned that it could negatively impact overall cardiac function. We were surprised to find the opposite; at least in the short term, cardiac function appeared to improve after radiation therapy.”
According to the Centers for Disease Control and Prevention, approximately 6.2 million American adults are currently living with heart failure. More than half of heart failure patients hospitalized with this disease die within five years of their initial hospitalization, demonstrating the need for better treatments. When the heart malfunctions, it gradually loses its ability to adequately supply oxygenated blood to the body. Heart failure, a complex condition, can have a variety of triggers, including previous heart attacks, viral infections, and chronic arrhythmias such as ventricular tachycardia.
A group of nine patients with ventricular tachycardia was evaluated with cardiac MRI before and after radiotherapy, and MRI showed improvement in cardiac function immediately after radiotherapy. In particular, the patients’ hearts showed an increase in the pumping ability of the left ventricle, which supplies blood throughout the body. Because the improvement was seen several days after treatment, it is unlikely that this was due to a reduction in the arrhythmia, which occurs gradually over the next few weeks or months.
The researchers also studied the effects of similar low-dose radiation on the hearts of groups of mice with heart failure from three different causes. Similar to what was observed in human patients, the researchers found that cardiac function, particularly left ventricular function, improved in mice that received radiation therapy. In mice with advanced heart failure, radiation therapy improved survival, showing that improved cardiac function led to improved survival.
Researchers found that the hearts of mice that received radiation malfunctioned, had less fibrosis (or scar tissue), and fewer cardiac macrophages, a type of immune cell that causes inflammation in the heart. did. In general, irradiated hearts had fewer rapidly proliferating cells, such as immune cells and fibroblasts, which tend to contribute to worsening heart failure. In contrast, normal heart muscle cells generally do not divide much, if at all.
“For example, we know that rapidly dividing cells, such as cancer cells, tend to be more susceptible to radiation-induced death,” said co-author Carmen Bergom, MD, radiation oncologist. Associate Professor) said. “The effects we are observing in these hearts are probably more complex than a simple reduction in rapidly dividing inflammatory immune cells. We will investigate more deeply to see what else is going on. As we continue to conduct research, we are pleasantly surprised to see evidence that these low doses of radiation to the heart may reduce inflammation and help rebuild the heart in beneficial ways. .”
To further understand the effects of radiation on the heart, researchers plan to continue studying patients who have already received radiation therapy for ventricular tachycardia. In this study, MRI showed that heart function improved. Next, the researchers plan to conduct more advanced studies to see if there is evidence of reduced inflammation in human hearts, similar to what they found in mice.
