Can radiation for cancer affect the heart?

Can radiation for cancer affect the heart?

Effect of radiation on the heart can be on the heart muscle causing a form of heart muscle disease known as restrictive cardiomyopathy or on the covering of the heart causing a condition known as constrictive pericarditis. In addition to this, radiation can cause damage to the blood vessels supplying the heart and sometimes the valves within the heart. Left sided heart valves are more often involved than those on the right side of the heart.

When radiation has damaged the blood vessels of the heart, it can lead to blocks and a heart attack. It may take a long period, of the order of decades for the effects to manifest. Sometimes it may be silent as well. Chance of involvement of the heart is higher when the radiation is given to cancer in the chest region near the heart. In case of damage to blood vessel, it is known to be more in those with usual risk factors for heart attack like obesity, high blood pressure, diabetes and smoking. Aggressive management of risk factors should be done, preferably even before giving the radiation treatment.

Treatment once the blood vessel damage is noted is similar to that of a regular heart attack. But the risks for coronary artery bypass surgery have been noted to be higher. Hence coronary angioplasty with removal of blocks by a balloon attached to a thin tube, introduced through a small hole made in the groin is preferred. Medicated stents give better results than bare metal stents in this scenario. Stents are thin spring like material implanted in the blood vessel after removal of blocks to prevent re-closure of the vessel after angioplasty.

When both radiation and chemotherapy are given to the same person, the chance for damage to the heart is more. But this does not mean that treatment should be denied for a potentially life threatening disease like cancer. Adequate precautions can be taken to minimize the damage and monitoring for early detection can help in early treatment. Modern radiation equipment can minimize collateral damage to the heart by special techniques by focusing the radiation beam to the cancer cells thus avoiding injury to heart.

High energy radiation treatment could affect the function of an implanted cardiac pacemaker or defibrillator. Pacemaker is a device used to give regular electrical signals to the heart when its own natural pacemaker is defective or the heart beats is low due to other reasons. Defibrillator is a device used to shock the heart back into action when it has stopped functioning due to very fast and disorganized electrical activity. Radiation treatment for cancer with high energy levels could interact with the material in the head of the linear accelerator used for radiation treatment and release neutrons. Such high energy radiation is more likely to be used for treatment of cancers in the chest or abdomen.

In one study, the interference was lower, about one in ten for pacemakers while it was about one third for implanted defibrillators. The positive news in the study was that when lower energy radiation treatment which would not cause the release of neutrons (energy less than 10 MV) into the body was used, there was zero chance for impairment of device function. Another positive point in the study was that no delayed effects on device function was noted, meaning that whatever effect occurs, will be recognizable soon after the radiation treatment.

It is also heartening to note that no deaths were reported due to device malfunction, though there were episodes of slow/fast heart beating and fall in blood pressure during the device malfunction. It may be noted that only 7 percent of the 249 courses of radiation treatment in those with cardiac implantable electronic devices (CIED) had device malfunction, possibly indicating that only a fraction of them needed really high energy treatment capable of releasing neutrons within the body.