Related conditions:
Breast cancer, esophageal cancer, lymphoma, metastases from primary cancers
Definition:
Cardiomyopathy is a disease in which the heart muscle is abnormally enlarged, thickened, or stiffened, decreasing its ability to pump blood. According to the World Health Organization, cardiomyopathies can be divided into three types: dilated, restrictive, and hypertrophic, both primary (or idiopathic) and secondary. Cardiomyopathy in cancer patients involves the secondary type of cardiomyopathy, due to a specific cause, usually chemotherapeutic agents such as doxorubicin as well as radiation, which is often employed for lymphoma or cancer of the breast or esophagus. In addition, metastases to the heart muscle from a cancer found elsewhere in the body can result in a restrictive form of cardiomyopathy.
Risk factors: Risk factors for cardiomyopathy in cancer patients include radiation and chemotherapy.
Etiology and the disease process: Both doxorubicin and bleomycin cause a dilated type of cardiomyopathy in which both the left and right ventricles are enlarged. The drugs most frequently associated with cardiotoxicity are doxorubicin (Adriamycin) and daunorubicin, which are anthracyclines. The total dose of anthracyclines a person receives determines the probability of developing chronic cardiomyopathy. Other chemotherapeutic drugs that can cause dilated cardiomyopathy include mitoxantrone, interferon, aldesleukin, trastuzumab (a monoclonal antibody), bleomycin, cyclophosphamide, 5-fluorouracil, vincristine, vinblastine, busulfan, mitomycin C, cisplatin, amsacrine, paclitaxel, and docetaxel. In dilated cardiomyopathy due to chemotherapeutic agents, the left ventricle typically demonstrates global hypokinesis, whereas the right ventricle has a less severe abnormality of contractility. Because of the ventricular dilatation, both mitral and tricuspid regurgitation are common, and patients with this condition also exhibit reduced ejection fractions. Decreased cardiac output, decreased stroke volume, and decreased systolic function are seen as well. Mural thrombi may also be present due to akinesis of the cardiac apex.
Radiation to the chest can cause a restrictive form of cardiomyopathy. In this condition the normal heart muscle is replaced by abnormal tissue. This abnormal tissue restricts the diastolic relaxation of the heart muscle so that the heart has normal ventricular size and contractility but aberrant diastolic relaxation leading to elevation of end diastolic pressures of the ventricles.
Incidence: The incidence of congestive heart failure secondary to cardiomyopathy from epirubicin is 0.7 percent. Doxorubicin is more cardiotoxic than epirubicin, and the incidence of congestive heart failure ranges from 3 to 4 percent.
Symptoms: In restrictive cardiomyopathy, the signs and symptoms are related to congestive failure and arrhythmias. In dilated cardiomyopathy due to chemotherapeutic agents, occasionally these agents will cause an acute cardiotoxic effect, with symptoms such as abnormal heart rhythms and electrocardiogram changes.
Screening and diagnosis: Chest X ray demonstrates the paradox of a huge heart with clear lungs in dilated cardiomyopathy. In the restrictive form of cardiomyopathy, the chest X ray often shows a normal-size heart with pulmonary congestion. Because the resultant abnormal physiology of restrictive cardiomyopathy is similar to that of constrictive pericarditis, distinction between these two entities is difficult. Magnetic resonance imaging (MRI), like computed tomography (CT), demonstrates a pericardial thickness greater than 4 millimeters in all patients with constrictive pericarditis, but this is rarely seen in restrictive cardiomyopathy.
In restrictive cardiomyopathy, the electrocardiogram shows low voltage in the late stages, and echocardiography shows decreased diastolic function with normal to decreased ejection fractions. In dilated cardiomyopathy, echocardiography always demonstrates a decreased ejection fraction because of an enlarged left ventricle with global hypokinesis. Systolic function is normal in restrictive cardiomyopathy, whereas it is always decreased in dilated cardiomyopathy. The reverse is true with diastolic function, where it is normal in dilated cardiomyopathy but decreased in restrictive cardiomyopathy. Gated myocardial scintigraphy shows decreased left ventricular ejection fraction, shortened ventricular ejection time, and decreased rate of ejection in dilated cardiomyopathy. Because marked focal wall abnormalities are usually absent in dilated cardiomyopathy, this may help distinguish it from end-stage coronary artery disease, which can manifest with focal-wall motion abnormalities.
Treatment and therapy: Nuclear medicine techniques have become important in monitoring left and right ventricular function in patients receiving chemotherapeutic agents that are cardiotoxic, including anthracyclines such as doxorubicin and daunorubicin. Gated myocardial scintigraphy is reproducible, allowing for serial assessment of ejection fractions and the selection of patients who may best tolerate the medication. Gated myocardial scintigraphy is especially important in monitoring patients to determine the onset of cardiac toxicity. Many clinicians allow the ejection fraction to fall to 0.45 in patients receiving doxorubicin before discontinuing therapy. Newer forms of anthracyclines called liposome encapsulates have been shown to be less toxic to the heart and still effective against cancer.
Prognosis, prevention, and outcomes: Lifestyle changes can reduce symptoms of heart failure from cardiomyopathy. Reducing salt and fluid intake and avoiding alcohol are beneficial as well as a judicious exercise plan to increase stamina without overtaxing a failing heart. Some patients whose cardiomyopathy progresses despite medication may be candidates for cardiac transplant.
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