Cardiomyopathy in cancer patients
Cardiomyopathy in cancer patients refers to a condition where the heart muscle becomes enlarged, thickened, or stiffened, typically as a secondary effect of cancer treatments such as chemotherapy and radiation. This type of cardiomyopathy can manifest as either dilated or restrictive, with dilated cardiomyopathy being commonly associated with chemotherapeutic agents like doxorubicin and bleomycin, while restrictive cardiomyopathy can result from radiation to the chest or metastases affecting the heart. Patients with a history of coronary heart disease, high blood pressure, or harmful lifestyle choices such as smoking and high alcohol consumption are at increased risk.
Symptoms may include signs of congestive heart failure and arrhythmias, often requiring careful monitoring through imaging techniques like echocardiography and nuclear medicine assessments. The incidence of congestive heart failure linked to these therapies varies, with doxorubicin showing a higher cardiotoxicity rate compared to epirubicin. Treatment approaches focus on managing heart function and may involve lifestyle changes, medication, or even cardiac transplantation in severe cases. Understanding and monitoring the risks associated with cancer treatments are essential for improving the prognosis and quality of life in affected patients.
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Cardiomyopathy in cancer patients
ALSO KNOWN AS: Doxorubicin-induced cardiomyopathy, secondary cardiomyopathy, bleomycin-induced cardiomyopathy, radiation-induced cardiomyopathy
RELATED CONDITIONS: Breast cancer, esophageal cancer, lymphoma, metastases from primary cancers
DEFINITION: Cardiomyopathy is when the heart muscle is abnormally enlarged, thickened, or stiffened, decreasing its ability to pump blood. 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. Additionally, metastases to the heart muscle from 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. Individuals are at a higher risk of cardiomyopathy if they have a history of coronary heart disease or high blood pressure. Additionally, drinking alcohol, smoking, and using drugs increases risk.
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 Rubex), daunorubicin (Cerubidine), epirubicin (Ellence), and idarubicin (Idamycin), 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, stroke volume, and systolic function are also seen. 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 restrictive cardiomyopathy, the chest X-ray often shows a normal-sized heart with pulmonary congestion. The distinction between these two entities is difficult because the resultant abnormal physiology of restrictive cardiomyopathy is similar to that of constrictive pericarditis. Magnetic resonance imaging (MRI), like computed tomography (CT), demonstrates a pericardial thickness greater than four millimeters in all patients with constrictive pericarditis, but this is rare 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 demonstrates a decreased ejection fraction because of an enlarged left ventricle with global hypokinesis. Systolic function is normal in restrictive cardiomyopathy but always decreased in dilated cardiomyopathy. The reverse is true with diastolic function, which 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 ejection rate 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 essential in monitoring left and right ventricular function in patients receiving cardiotoxic chemotherapeutic agents, including anthracyclines such as doxorubicin and daunorubicin. Gated myocardial scintigraphy is reproducible, allowing serial assessment of ejection fractions and selecting 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. Modern anthracyclines called liposome encapsulates are less toxic to the heart and 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 and 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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