Cardiomyopathy Health Article

Definition

Cardiomyopathy is a type of heart disease in which the heart muscle is abnormally enlarged, thickened and/or stiffened. As a result, the heart muscle's ability to pump blood is usually impaired.

Description

When the heart muscle enlarges and is unable to pump effectively, its function declines. This is called congestive heart failure. Congestive heart failure results in a reduction in oxygen delivery to the tissues and a backup of fluid into those tissues. Fluid in the lungs can cause shortness of breath with exertion and a need to sleep with the head elevated. Fluid buildup in other areas can manifest itself as swelling of the feet and ankles or swelling and pain in the liver. Congestive heart failure once carried a grim prognosis, but new advances in medical treatment have improved that prognosis significantly.

People with cardiomyopathy can develop an abrupt buildup of fluid in the lungs, called acute pulmonary edema. This is a medical emergency. In addition to intravenous medications that remove fluid, support blood pressure, and strengthen the heart's pumping function, acute pulmonary edema is also treated with oxygen and sometimes the temporary use of a respirator.

Almost anything that can damage the heart muscle fibers can produce cardiomyopathy and congestive heart failure. Long-standing high blood pressure, diabetes, heart attacks, alcohol, drugs, and certain viruses are all causes of cardiomyopathy.

In a person with cancer, cardiomyopathy and its symptoms are generally due to the adverse effects of treatment.

Causes

Among the causes of cardiomyopathy in cancer patients is radiation therapy to the chest, which is often employed for breast cancer, cancer of the esophagus or lymphoma. Children who receive radiation therapy to the spinal column can suffer late effects to their hearts. The radiation can damage the heart muscle, leading to cardiomyopathy and heart failure. It can also damage the coronary arteries, leading to angina or a heart attack.

More commonly, cardiomyopathy in a cancer patient is an adverse effect of chemotherapy. Among the chemotherapeutic drugs known to be toxic to the heart are:

• Doxorubicin
• Daunorubicin
• Mitoxantrone
• Cyclophosphamide
• Fluorouracil
• Vincristine
• Vinblastine
• Busulfan
• Mitomycin C
• Cisplatin
• Amsacrine
• Paclitaxel
• Docetaxel
• Interferons
• Aldesleukin
• Trastuzumab

The drugs most frequently associated with cardiotoxicity are doxorubicin and daunorubicin, which are anthracyclines. The total cumulative dose of anthracyclines a person receives determines the likelihood of developing chronic cardiomyopathy. In a few cases, these agents will cause an acute cardiotoxic effect, with symptoms such as abnormal heart rhythms and electrocardiogram changes.

Patients receiving anthracyclines have nuclear imaging scans of their hearts before starting treatment, during treatment and after treatment, since the adverse effects can be delayed. These studies measure the heart's ejection fraction, which is the percentage of blood volume pumped with each heartbeat. A normal ejection fraction is around 60%. In other words, 60% of the blood that collects in the heart between heartbeats is pumped out with each beat. Anthracyclines can cause a significant reduction in ejection fraction and therefore in heart function.

Often used for colon, breast, and head and neck cancers, 5-fluorouracil can cause cardiotoxicity, mostly in those patients with existing coronary artery disease or those who are also receiving radiation therapy to the chest. Cyclophosphamide, often used in those who have had bone marrow transplants, is another cause of cardiomyopathy. The taxanes, paclitaxel and docetaxel, are newer agents often used for breast and ovarian cancers. Taxanes can cause slowing of the heart rate, but this is not usually serious or prolonged.

Trastuzumab is a monoclonal antibody used in some patients with breast cancer. About 30% of women have overexpression of human epidermal growth factor receptors, called HER-2, on the surface of their cancer cells. Trastuzumab selectively attacks those receptors. Heart muscle also has some HER-2 receptors, which is believed to be the reason that trastuzumab can cause cardiomyopathy. Trastuzumab is often used in conjunction with anthracyclines or taxanes, both of which have effects on the heart, and patients on these drugs must be carefully monitored for signs of heart disease.

The diagnosis of cardiomyopathy is made on the basis of the history and physical examination, along with tests of heart function. Occasionally, biopsies of the heart muscle are performed to confirm the diagnosis.

Other forms of damage to the heart can occur with cancer and its treatments. Some cancers can metastasize to the heart muscle or the valves within the heart. Cancers that spread to the pericardium, the outer lining of the heart, can induce fluid collections called pericardial effusions.

High-output cardiac failure is an unusual form of heart failure that results when the body senses a lowered total blood volume. This can occur with anemia, a side effect of many treatments, or with large tumors that have large numbers of blood vessels, drawing blood away from the general circulation.

Amyloidosis is a condition in which abnormal proteins are deposited in tissues throughout the body, including the heart. Amyloidosis is seen with multiple myeloma.

Abnormal heart rhythms can occur due to toxic effects of chemotherapeutic drugs and perhaps radiation treatments on the electrical conducting system of the heart.