Radiation therapy can affect any part of the heart. Different forms of radiation cardiotoxicity result, depending on which area was damaged. This section covers the most common types of radiation cardiotoxicity.
Radiation therapy to the heart can cause irritation and inflammation of the pericardium, a fluid-filled space surrounding the heart. Such inflammation, known as pericarditis, can occur at any time after the start of radiation, from immediately to months or years after treatment. Symptoms of pericarditis include shortness of breath and chest pain that may be eased by leaning forward. If the inflammation is significant, it can also spread to the heart muscle, and is termed "myopericarditis."
Radiation therapy can cause pericardial effusion, or the development of a fluid collection in the pericardial sac. Such fluid buildup can cause shortness of breath, chest pressure and lightheadedness. It may need to be removed.
Radiation therapy can injure and scar the muscle cells of the heart. This scarring can cause the heart muscle to become weak or stiff. These conditions are known as cardiomyopathies. Weakening or stiffening of the heart muscle can make it difficult for the heart to pump enough blood to meet the body's needs, a condition called heart failure. One of the main symptoms is fluid buildup in the body, especially the lungs and legs. Cardiomyopathy and heart failure from radiation therapy generally develop many years after treatment.
The coronary arteries supply blood to the heart. Any disruption in this blood supply can interfere with the heart's pumping function. Coronary arteries can become blocked or clogged with atherosclerosis or plaque. A significant blockage or sudden blockage in the coronary arteries can be very serious. This can lead to severe damage or death of heart tissue and is known as a heart attack (also called myocardial infarction). Common symptoms of a heart attack include shortness of breath, and chest pain or pressure that can come and go or be constant. These symptoms can be observed during or made worse by exertion. Less common symptoms are sweating, nausea, weakness, lightheadedness, and fatigue. If you think you are having a heart attack, dial 911 at once.
Radiation therapy in the area of the heart can injure the coronary arteries. This injury can speed up atherosclerosis and increase the risk of a heart attack. Coronary artery disease caused by radiation therapy generally develops many years after treatment. However, with radiation, the development of heart disease occurs earlier than normal. As a result, patients who receive radiation therapy in the area of the heart can develop coronary artery disease at younger ages than normally expected. So it is important for these individuals to be screened for heart disease. Your doctor may recommend stress testing to assess your heart.
The heart contains four valves that help blood move through the heart normally. They open to let blood flow forward and close to prevent blood from flowing backward. Radiation therapy can cause thickening, fibrosis, and calcium buildup of the valves. This prevents the valves from fully closing, leading to backward flow (regurgitation). This can also cause thickening and narrowing of the valves, which prevents opening and limits forward flow (stenosis). Both regurgitation and stenosis can occur many years after radiation therapy. Common signs are shortness of breath (worse with exertion), swelling in the ankles, fatigue, weakness, chest pressure, and lightheadedness.
Normal heart function relies on a series of coordinated electrical events inside the heart that occur at the right time and in the right order. This rhythm repeats tens to hundreds of thousands of times throughout the day and is controlled by the heart's electrical wiring system (conduction system). Radiation therapy can damage the conduction system and disturb the rhythm of the heart.
Any disturbance in the heart's rhythm is called an arrhythmia. With some arrhythmias, heart rhythm is abnormally fast, and with others, the rhythm is too slow. Arrhythmias caused by radiation therapy are not common. However, when they do develop, they can be slow arrhythmias and occur months to years after treatment. Early on, they may be fast rhythms (for example atrial fibrillation, supraventricular tachycardia).