Scientists at the Washington University School of Medicine have made an intriguing discovery that could see radiation therapy become a less invasive treatment for heart arrhythmia. The technique seems to activate the heart cells to revert to a younger state and repair the tissue.
Arrhythmia is a condition where the heart beats in an irregular fashion, which can lead to potentially dangerous health problems. It’s a result of issues with the way electrical signals are sent through the tissue, and one of the main treatments is called catheter ablation. This invasive procedure involves threading thin tubes through arteries into the heart, making a small burn to create scar tissue that interrupts the signals.
A few years ago, the Washington University team discovered a far less invasive alternative – radiation therapy, of the kind often used to treat cancer patients. When directed at the heart, the treatment was found to improve arrhythmia symptoms, just as well as, or perhaps even better than, catheter ablation.
It was assumed that the radiation was creating similar scarring to the catheter ablation process, but observations suggested that other factors were at work. Radiation therapy seemed to improve the symptoms within days, instead of the months it can take with catheter ablation. So for the new study the researchers investigated what else might be happening.
They examined the hearts of patients from the first test, who had either died or undergone heart transplants, and found that scarring alone couldn’t account for the improvements. Follow-up tests on mouse hearts showed that activity seemed to have temporarily ramped up in a signaling pathway called Notch. That increases sodium ion channels in the heart muscle, reducing arrhythmia.
Intriguingly, the Notch pathway is normally inactive in adults. It plays a key role during development of the electrical system of the heart, before going quiet in the heart during adulthood. Reactivating it with radiation seems to revert the tissue back into a healthier, “younger” state for a short time. The beneficial effects, however, were seen to persist in human patients for at least two years.
“Radiation does cause a type of injury, but it’s different from catheter ablation,” says Julie Schwarz, co-author of the study. “As part of the body’s response to that injury, cells in the injured portion of the heart appear to turn on some of these early developmental programs to repair themselves. It’s important to understand how this works because, with that knowledge, we can improve the way we’re treating these patients and then apply it to other diseases.”
The team plans to continue investigating the technique as a potential treatment for arrhythmia, and whether smaller doses could be used.
The research was published in the journal Nature Communications.
Source: Washington University