Cancer, the abnormal growth of cells into tumors, requires aggressive treatment such as chemotherapy, the use of drugs, and radiation, the use of high-energy waves, in order to kill the cells. Although both treatments can effectively treat cancer, they cannot target only the abnormal cells. This means that many healthy cells become damaged during treatment, resulting in side effects. Some chemotherapy agents and the use of radiation increases the risk for heart attack during treatments; however, many side effects affecting the heart occur months or even years after treatment, known as late effects.
Radiation therapy targeted to the chest cavity can cause damage to the cells within the heart muscle. Some chemotherapy drugs, such as those classified as anthracyclines, can also damage the cells in the heart. Over time the damaged cells weaken the heart and can lead to a condition known as cardiomyopathy, characterized by an enlarged heart.
Cardiomyopathy inhibits the heart’s ability to pump as it should and can lead to additional heart problems such as abnormal heartbeats, according to the American Heart Association. Because the heart cannot contract as strongly as it needs to, the chambers retain blood which increases the risk for the formation of blood clots.
Congestive Heart Failure
Anthracyclines can also damage the cells in the left ventricle of the heart. Blood flows through the four chambers of the heart in one direction. Oxygen-poor blood returning from the body enters the right atrium and flows to the right ventricle which pumps the blood to the lungs to receive oxygen. The left atrium receives oxygenated blood from the lungs and sends it to the left ventricle which pumps the blood out to the body.
Damage to cells in the left ventricle cause the outside wall to become thin and stiff inhibiting the chambers ability to contract, especially during times of physical exertion. Weak left ventricle contractions cause blood to backflow into the left atrium and further into the blood vessels of the lungs. This leads to a condition known as congestive heart failure, in which the heart fails to pump enough blood to meet the body’s needs, according to MayoClinic.com.
Heart Valve Damage
Radiation treatments can also damage the heart valves. The unidirectional flow of blood through the heart occurs due to the presence of heart valves, which open and close as the chambers of the heart contract and relax. Radiation most commonly causes damage to the mitral valve that separates the left atrium and left ventricle, and the aortic valve that separates the left ventricle and the aorta, according to Candlelighters Childhood Cancer Foundation. Damage to the heart valves can cause thick and stiff valves that inhibit the flow of blood or weak valves that allow blood to backflow.
Premature Coronary Artery Disease
Radiation treatments can increase the risk for premature onset of coronary artery disease. Coronary artery disease occurs when plaque--a fatty substance--builds up on the walls of blood vessels leading to the heart. Damaged blood vessels, caused by high blood pressure or radiation, attract plaque. The buildup of plaque interferes with the flow of blood to the heart and can cause chest pain and lead to a heart attack.