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Tumors of the Heart
Neoplastic involvement of the heart can be divided into primary cardiac tumors arising in the heart and secondary cardiac tumors that have metastasized to the heart. Primary cardiac tumors can be further stratified into benign and malignant tumors. Secondary involvement of the heart is relatively common, with 10% to 20% of patients dying of disseminated cancer having metastatic involvement of the heart or pericardium. Surgical resection is seldom possible or advisable for these tumors, and surgical intervention is usually limited to drainage of malignant pericardial effusions, diagnostic biopsies, or both. There are uncommon cases of metastatic disease limited to the heart for which resection is reasonable.
Primary tumors of the heart are uncommon but not rare. In unselected autopsy series, the incidence of primary cardiac neoplasm ranges between 0.0017% and 0.19%. Approximately 75% of primary cardiac tumors are benign and 25% are malignant. Approximately 50% of the benign tumors are myxomas, and approximately 75% of the malignant tumors are sarcomas. The clinical incidence of these tumors is approximately 1 in 500 cardiac surgical cases and, with the exception of myxomas, most surgeons will rarely encounter primary cardiac tumors. The purpose of this chapter is to summarize useful information for the evaluation and management of patients with primary and secondary cardiac tumors and to provide a reference for additional study on these subjects.
Historical Background
Cardiac tumors were a postmortem diagnosis until the first antemortem diagnosis of a cardiac tumor was made in 1934 when Barnes diagnosed a cardiac sarcoma using electrocardiography and biopsy of a metastatic lymph node. In 1936, Beck successfully resected a teratoma external to the right ventricle, and Mauer removed a left ventricular lipoma in 1951. Treatment of cardiac tumors was profoundly influenced by two events: the introduction of cardiopulmonary bypass in 1953 by John Gibbon allowing safe and reproducible approach to the cardiac chambers and the introduction of cardiac echocardiography allowing safe and noninvasive diagnosis of an intracardiac mass. The first echocardiographic diagnosis of an intracardiac tumor was made in 1959. A large right atrial myxoma was removed by Bahnson in 1952 using caval inflow occlusion but the patient expired 24 days later. Crafoord in Sweden first successfully removed a left atrial myxoma in 1954 using cardiopulmonary bypass, and Kay in Los Angeles first removed a left ventricular myxoma in 1959. By 1964, 60 atrial myxomas had been removed successfully with a steady increase because of increasing safety of cardiopulmonary bypass and increased use of echocardiography for detection. Operations are currently routinely performed on the vast majority of patients with atrial myxoma with minimal mortality. Primary malignant tumors, however, continue to represent a challenge.
Primary Benign Tumors
Myxomas
Definition, Incidence, and Prevalence
Myxomas are the most common primary cardiac tumors. They are benign. Although they have been reported in both sexes and in all age groups, they most often occur in women in the third to sixth decade of life. Myxomas are usually sporadic, but at least 7% occur as part of an autosomal dominant syndrome. In the latter situation, the myxoma is a component of a larger syndrome referred to as the Carney complex . In the Carney complex, myxomas are associated with spotty pigmentation of the skin and endocrine hyperactivity. Myxomas that arise as part of the Carney complex affect both sexes equally and at any age. They arise as single or multiple lesions in all chambers of the heart, and tend to recur after surgical excision.
Morphology
Arising from the endocardium, myxomas usually extend into a cardiac chamber. They are generally polypoid, pedunculated lesions with a smooth surface that may be covered with thrombus. The tumors range in size from 1 to 15 cm, but they are most commonly about 5 cm in diameter with a weight of approximately 70 g. Myxomas are thought to arise from pluripotent mesenchymal cells. Histologically, they consist of a matrix of acid mucopolysaccharide. The cells are polygonal or spindle-shaped and may form capillary-like channels that can communicate with arteries and veins located at the base of the tumor.
Myxomas most commonly occur in the atria. Approximately 75% arise in the left atrium, and 15% to 20% arise in the right atrium. Most left atrial myxomas are located on the border of the fossa ovalis, but they can originate from any place on the atrial wall. The remaining myxomas are located in the ventricles. Myxomas arising from cardiac valves are rare ( Fig. 103-1 ).
Clinical Characteristics
Patients with myxomas can have a variety of symptoms. In the sporadic form, classic findings include emboli, congestive heart failure caused by obstruction of cardiac blood flow, and constitutional symptoms. These sequelae are related to the location, size, and mobility of the tumor.
Because most myxomas arise in the left atrium, systemic embolization is common, occurring in 30% to 50% of cases. Left ventricular myxomas have an even higher propensity to embolize. Right atrial myxomas rarely display clinical manifestations of emboli. Embolic material from myxomas can compromise blood flow to any organ, but the brain is most commonly affected. Myxoma should be included in the differential diagnosis of any systemic embolic event, and any embolic material removed should undergo histologic evaluation.
Patients with myxomas can also display signs and symptoms related to cardiac obstruction. Typically, the findings are related to the tumor's ability to impede filling of the ventricles; in such instances, signs and symptoms may mimic those of mitral or tricuspid valve stenosis. Less commonly, the tumors impede atrioventricular (AV) valve leaflet coaptation, causing valvular regurgitation. Much less frequently, ventricular tumors obstruct ventricular outflow and cause findings similar to those of aortic or pulmonic stenosis. Constitutional symptoms include fever, malaise, rash, weight loss, and myalgia. Abnormal laboratory values, including elevated erythrocyte sedimentation rate, anemia, thrombocytopenia, and an elevated C-reactive protein, are common. These constitutional symptoms and laboratory findings are not related to tumor size or location. Many patients with myxomas are however asymptomatic. The myxoma may be detected by routine screening echocardiography performed for other indications. Asymptomatic myxomas should be excised to prevent emboli, valvular dysfunction, or constitutional symptoms.
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