Cardiomyopathy

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.

Treatments

The treatment of cardiomyopathy in cancer patients consists of removing the cause when possible and using cardiac medications to reduce symptoms.

Since the most common cause of cardiomyopathy in cancer patients is due to the use of anthracyclines, oncologists keep a careful record of the total dose administered to patients over the course of their treatment, and stop the drug before the known toxic dose has been reached.

Newer forms of anthracyclines have been formulated which are called liposome encapsulates. These have been shown to be less toxic to the heart and still effective against cancer. Administering anthracyclines weekly, rather than every three to four weeks, and giving the dose more slowly both seem to reduce the cardiac toxicity. The simultaneous administration of drugs that might protect the heart is under study, but their use is not yet recommended routinely.

The treatment of an established cardiomyopathy and heart failure due to cancer treatment is a combination of medications that are used for heart failure of any origin. One of these is digoxin, which improves the heart's pumping function in addition to other beneficial effects. Diuretics, often called water pills, flush water and salt from the body and are used to reduce swelling. Angiotensin-converting enzymes or ACE inhibitors comprise the third group of drugs useful for heart failure. These relax the arteries, which reduces the work that the heart must do to effectively pump blood. The fourth group of medications includes beta-blockers, which slow the heart rate and reduce its workload. This combination of medications has significantly improved the prognosis for people with heart failure.

Lifestyle changes can reduce symptoms of heart failure. Reducing salt and fluid intake and avoiding alcohol are beneficial. A judicious exercise plan can increase stamina without overtaxing a failing heart. Many people who have undergone cancer treatment also have coronary artery disease, which can aggravate the symptoms of heart failure caused by chemotherapy toxicity. Patients whose cancer prognosis is good can sometimes benefit from treatment of their coronary artery disease.

Some patients whose cancer is cured but whose cardiomyopathy progresses despite medication are candidates for heart transplant.

Alternative and complementary therapies

Naturopaths might prescribe hawthorn for symptoms of congestive heart failure. No studies have demonstrated either benefit or harm from this preparation.

Acupuncture and acupressure are sometimes beneficial in reducing symptoms of shortness of breath and may offer some relief to those with heart failure due to cardiomyopathy. The pressure point for the heart is said to be on the palm of the hand, over the bones between the fourth and fifth fingers.

Resources

BOOKS

Dodd, Marylin J. Managing the Side Effects of Chemotherapy and Radiation Therapy: A Guide for Patients and Their Families. San Francisco: University of California at San Francisco School of Nursing, 1996.

McKay, Judith, and Nancee Hirano. The Chemotherapy and Radiation Therapy Survival Guide (Chemotherapy and Radiation Therapy Survivor's Guide, 2nd Ed). Oakland: New Harbinger Publications, 1998.

Moore, Katen, and Libby Schmais. Living Well with Cancer: A Nurse Tells You Everything You Need to Know About Managing the Side Effects of Your Treatment. New York: Putnam Publishing Group, 2001.

PERIODICALS

Ginsburg, A.D. "Doxorubicin-induced Cardiomyopathy." New England Journal of Medicine 340, no. 8 (February, 1999): 654.

OTHER

Heart Center Online Home Page. 6 June 2001 <http://www.heartcenteronline.com/> This website serves cardiologists and their patients and has sections on pericardiocentesis, pericarditis and tamponade.

Marianne Vahey, M.D.

Acute pulmonary edema

—An abrupt collection of fluid in the lungs due to failure of the heart muscle to pump blood properly.

Angiotensin converting enzyme inhibitors

—Medications that lower blood pressure and reduce the work load of the heart muscle.

Beta-blockers

—Medications that relax blood vessels and slow the heart rate.

Congestive heart failure

—A condition that results from inadequate pumping action of the heart muscle, causing fluid buildup in lungs and tissues.

Diuretics

—Medications, often called water pills, that eliminate excess water and salts from the body.

Ejection fraction

—The percentage of the blood sitting in the heart between heartbeats that gets pumped to the body with each heartbeat.