Cardiac tumors are classified into primary and secondary tumors. Among primary cardiac tumors, 25% are malignant, most commonly sarcomas, while 75% are benign, with 50% being myxomas.
Pathology
Myxomas originate from subendocardial mesenchymal cells with multipotent differentiation potential. These cells are abundant in the fossa ovalis region of the atrial septum, making it the most common site of occurrence. As the tumor grows, it projects into the cardiac chamber as a pedunculated mass, often attached to the atrial septum or atrial wall via a stalk. The tumor moves with the cardiac cycle. It is typically oval or round in shape, sometimes lobulated or resembling a cluster of grapes. It appears translucent, gelatinous, and shiny, with varied colors including light yellow, pale green, or dark purple interspersed with red hemorrhagic areas. Myxomas are fragile, and fragments breaking off into the bloodstream may lead to systemic or pulmonary arterial embolism.
Although most myxomas are benign, a small number of cases may undergo malignant transformation into myxosarcomas or present with distant metastases.
The primary pathophysiological alteration caused by cardiac myxomas is obstruction of normal blood flow by the tumor protruding into the cardiac chamber. Left atrial myxomas often lead to mitral valve obstruction, impairing the opening and closing of the valve.
Clinical Manifestations and Diagnosis
The clinical presentation of cardiac myxomas is highly variable, depending on the tumor's location, size, growth rate, stalk length, and associated complications such as detachment, hemorrhage, or necrosis.
Obstruction of Blood Flow
The most common clinical symptom of left atrial myxomas is atrioventricular valve obstruction, resulting in palpitation and dyspnea, which mimic mitral valve disease. Physical examination often reveals diastolic or systolic murmurs at the apex and accentuation of the second heart sound in the pulmonary valve area. In cases of highly mobile tumors, the intensity and nature of the murmur may change with positional changes. Right atrial myxomas causing tricuspid valve obstruction may present with symptoms such as jugular vein distension, hepatomegaly, ascites, and lower limb edema, resembling tricuspid valve stenosis or constrictive pericarditis. On auscultation, diastolic murmurs may be heard at the left sternal border in the fourth or fifth intercostal space. Highly mobile myxomas can suddenly obstruct the atrioventricular valve orifice, leading to syncope, seizures, or even sudden death.
Systemic Reactions
Systemic immune responses triggered by tumor hemorrhage, degeneration, or necrosis may include fever, weight loss, anemia, loss of appetite, joint pain, urticaria, fatigue, elevated erythrocyte sedimentation rate, and changes in serum protein electrophoresis.
Arterial Embolism
A minority of cases may develop embolic phenomena, manifesting as hemiplegia, aphasia, coma, acute abdominal pain (mesenteric artery embolism), limb pain, or ischemia (limb artery embolism). In some instances, the diagnosis is made only after pathologic examination of embolic specimens following embolectomy.
Other Manifestations
Left atrial myxomas may cause chest X-rays to show signs of left atrial and right ventricular enlargement, pulmonary congestion, and features resembling mitral valve disease. Electrocardiograms (ECGs) typically indicate similar findings to mitral valve disorders, but atrial fibrillation is rare in myxoma patients. The clinical presentation of left atrial myxomas can easily be confused with rheumatic mitral valve disease. However, myxoma cases often lack a history of rheumatic fever, have a shorter disease course, and exhibit symptoms and signs that may vary with positional changes. Most cases demonstrate sinus rhythm on ECG. Echocardiography has a very high diagnostic accuracy in these cases, revealing a cloud-like mobile echo mass. In left atrial myxomas, the mass is located within the atrial cavity during ventricular systole and moves to the mitral valve orifice during diastole.
Treatment
Definitive diagnosis of myxoma warrants early surgical removal of the tumor to restore cardiac function, prevent malignancy, sudden atrioventricular valve obstruction leading to sudden death, or embolic events caused by tumor fragmentation.
Tumor resection is performed using cardiopulmonary bypass and is often approached via the right atrium and atrial septum for optimal tumor removal. If necessary, a bi-atrial incision may be used. The tumor, along with its attachment to the atrial septum or wall, is excised en bloc, followed by direct suture repair or patch reconstruction of the atrial septal defect. During surgery, precautions are taken to avoid manipulating or compressing the heart prior to establishing bypass, as this could dislodge tumor fragments and cause embolism. Careful inspection of all cardiac chambers is necessary to rule out multiple myxomas or residual fragments.
Outcomes of surgical treatment are excellent, with a low operative mortality rate. However, recurrence is possible in a small number of cases, warranting regular postoperative follow-up.