【Overview】.
It is the most common primary benign cardiac tumor, accounting for 50% of benign cardiac tumors. Li Yun, Department of Thoracic Surgery, The Third Affiliated Hospital of Sun Yat-sen University
It occurs mostly in middle age, and the male:female ratio is about 1:2~3.
It is mostly found in the left atrium, accounting for 75%, followed by the right atrium, accounting for 20%, and less frequently in the ventricle.
It has the tendency to recur and infiltrate locally.
Etiology
It originates from the mesenchymal tissue with multi-directional differentiation potential under the endocardium during embryonic development.
The atrial septal fossa is rich in these cells and is therefore a good site for tumor development.
Pathology
Gross pathology: usually with a tip, the appearance is translucent jelly-like and colorful. The cells are mostly oval or round, lobed or grape-shaped, varying in size from 1 cm to 10 cm, brittle and easily detached into fragments.
Light microscopy: The cells are mostly indeterminate mucous cells filled with mucus-like stroma, mostly single, but may appear as multinucleated giant cells with abundant small blood vessels.
Electron microscopy: The surface of tumor cells is rich in microvilli or cytoplasmic prominence, and the tumor cells are filled with fine fibers – a remarkable ultramorphological feature of mucinous tumor.
Clinical manifestations
Symptoms.
Obstruction: Most commonly, the tumor obstructs the mitral or tricuspid valve orifice, causing blood flow obstruction. In a few cases, it can cause mitral or tricuspid valve insufficiency. Characteristics of obstruction symptoms – intermittent episodes, transient syncope, and signs are not constant and may change with position changes.
Embolism: Mucinous tumors of the left heart may cause embolism of the body circulation. Right heart mucinous tumor can cause pulmonary artery embolism and pulmonary hypertension.
Systemic symptoms: Mucinous tumor hemorrhage, degeneration, and necrosis cause fever, joint pain, weight loss, urticaria, and malaise.
Signs.
Left atrial mucinous tumor – diastolic or systolic murmur is heard in the apical region, and the second heart sound in the pulmonary valve region is enhanced.
The loudness and nature of the murmur may change with postural changes.
In the case of right atrial mucinous tumor causing tricuspid valve orifice obstruction, jugular vein anger, hepatomegaly, ascites, and lower limb edema may occur.
Laboratory tests]
Routine hematology: anemia.
Biochemistry: increased serum protein electrophoresis α2 and β globulin.
Erythrocyte sedimentation rate is increased.
Imaging examination
X-ray: left atrial mucinous tumor often shows enlarged left atrium and right ventricle and pulmonary stasis.
Echocardiography: Sensitivity is over 99%. It can clearly show the tumor size, scope, activity with heart diastole and contraction and the effect of tumor on heart valves.
Left atrial mucinous tumor is seen in the left heart cavity as an abnormal dotted sheet of reflective light mass, active between the left atrium and left ventricle, returning to the left atrial cavity during systole and reaching the mitral valve orifice into the left ventricle during diastole, with reduced slope of the anterior mitral valve leaflet and enlarged left atrium.
The right atrial mucinous tumor abnormally reflects light masses in the right heart cavity, in the right atrium during systole, and moves with the tricuspid valve toward the right ventricle during diastole or enters the right ventricular cavity through the tricuspid valve orifice. The right atrium and right ventricle are enlarged.
CT and MRI: It shows the heart cavity, myocardial wall, pericardium and the relationship with surrounding structures.
[Auxiliary examinations
ECG: There may be atrial and ventricular enlargement, first- and second-degree atrioventricular block, and electrocardiographic changes of incomplete right bundle branch block. Atrial fibrillation may also occur. In more severe cases, there may be ST-T changes.
Cardiovascular angiography and digital subtraction cardiovascular angiography (DSA): to show the expansion of the tumor outside the heart chambers, the extent of the lesion and the relationship with the surrounding tissue structures.
【Diagnosis
Fever, joint pain, weight loss and other systemic symptoms; intermittent episodes of palpitations, shortness of breath, transient syncope and other obstructive symptoms; hemiplegia, aphasia, coma and other embolic manifestations.
The nature and loudness of the murmur may change with the change of position.
Echocardiography shows that the tumor moves with the contraction and diastole of the heart. Cardiac angiography may show intra-cardiac occupying lesions, etc. to confirm the diagnosis.
Differential diagnosis
Left atrial mucinous tumor should be distinguished from mitral stenosis, and right atrial mucinous tumor should be distinguished from chronic constrictive pericarditis, tricuspid stenosis and pulmonary stenosis.
Mitral stenosis.
It is mostly seen in middle-aged and elderly patients with a history of rheumatic fever, palpitations and shortness of breath after activity, and paroxysmal dyspnea at night.
On physical examination, the left atrium and right ventricle are enlarged, and a diastolic rumble-like murmur is heard in the mitral valve auscultation area, which does not change with body position and has no fluttering sound.
The echocardiogram showed thickening and calcification of the mitral valve leaflets, stenosis of the valve orifice, and a “fish-mouth” shape, and enlargement of the left atrium and right ventricle.
The electrocardiogram showed widened and bimodal P waves and increased right ventricular voltage, often with atrial fibrillation.
When differentiating right atrial mucinous tumor from chronic constrictive pericarditis, tricuspid stenosis and pulmonary stenosis, systolic and diastolic murmurs can be heard between the 3rd and 4th intercostal spaces on the left edge of the sternum, and the correlation between symptoms, murmurs and postural changes has differential diagnostic value.
Treatment
Once the diagnosis is confirmed, the tumor should be removed surgically immediately.
Restrict the activities and strictly rest in bed to avoid sudden death caused by tumor blocking the atrioventricular valve orifice due to position change or embolism caused by tumor debris dislodging.
If there are systemic symptoms, actively deal with them and operate as soon as possible.
In case of acute pulmonary edema, actively improve cardiac function with cardiac stimulation and diuresis, and operate as early as possible or as an emergency.
When embolism occurs, wait for the condition to stabilize and then actively operate.
Surgical methods.
Routinely establish extracorporeal circulation.
A right atrial septal incision or a combined left and right atrial incision is used if necessary.
The mucinous tumor is excised along with a portion of the septal tissue attached to the tip.
The septal incision is repaired with direct sutures or patches.
[Complications
Embolism: mostly seen in cerebral embolism.
Acute heart failure, with acute pulmonary edema in severe cases.
Arrhythmia: mainly manifested as atrial arrhythmia or partial conduction block.
Tumor recurrence: It is common within 2 years after surgery, and the site is usually located in the original heart cavity. The basal infiltration of recurrent mucinous tumor is more extensive, and the growth rate is faster than the initial tumor.
Metastasis: rare, mainly brain metastasis.