الفهرس 
ANATOMY OF SUPERIOR VENA CAVAOnly 14 pages are availabe for public view
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Abstract
Superior vena cava syndrome is an array of symptoms caused by the impairment of blood flow through the superior vena cava to the right atrium.
Symptoms that prompt suspicion of this syndrome include dyspnea, coughing, and swelling of the face, neck, upper trunk and extremities. In rare instances, patients may complain of hoarseness, chest pain, dysphagia, and hemoptysis.
Physical signs that may be noted on presentation are neck vein distention, thoracic vein distention, edema of the face or upper extremities, plethora, and tachypnea. Rarely, cyanosis, Horner’s syndrome, and a paralyzed vocal cord may also be present.
SVCS is usually a sign of locally advanced bronchogenic carcinoma. Survival depends on the status of the patient’s disease. Most non-Hodgkin’s lymphoma patients with SVCS respond to appropriate chemotherapy or to combined modality regimens.
Since superior vena cava syndrome was first described by William Hunter in 1757, the spectrum of underlying conditions associated with it has shifted from tuberculosis and syphilitic aneurysms of the ascending aorta to malignant disorders.
Almost 95% of SVCS cases described in published modern series are due to cancer; the most common cause is small cell bronchogenic carcinoma, followed by squamous cell carcinoma of the lung, adenocarcinoma of the lung, non-Hodgkin’s lymphoma, and large cell carcinoma of the lung.
Non-malignant causes of SVCS are thrombosis that is associated with intra-caval catheters or pacemaker wires. A rare cause of SVCS is fibrosing mediastinitis, either idiopathic or associated with histoplasmosis. Behcet’s disease contributes about 50% of causes of SVCS in Egypt while the other 50% had SVCS with malignant etiology, mostly bronchogenic carcinoma.
The severity of the syndrome depends on the rapidity of onset of the obstruction and its location. The more rapid the onset, the more severe the symptoms because the collateral veins do not have time to distend to accommodate an increased blood flow.
If the obstruction is above the entry of the azygos vein, the syndrome is less pronounced because the azygous venous system can readily distend to accommodate the shunted blood with less venous pressure developing in the head, arms, and upper thorax. If the obstruction is below the entry of the azygos vein, more florid symptoms and signs are seen because the blood must be returned to the heart via the upper abdominal veins and the inferior vena cava, which requires higher venous pressure.
The initial evaluation of the patient should include a chest radiograph to look for mediastinal masses and associated findings, such as pleural effusion, lobar collapse, or cardiomegaly.
Computed tomography (CT) scanning of the thorax yields the most useful diagnostic information and can define the anatomy of the involved mediastinal nodes. Venous patency and the presence of thrombi are assessed by using contrast and rapid scanning techniques.
Depending on local expertise, contrast or nuclear venography, magnetic resonance imaging, and ultrasound may be valuable in assessing the site and nature of the obstruction.
Other investigations can be used in malignant causes, as biopsy specimen which should be taken from the most accessible site that is clinically involved with disease. It may include bronchoscopy, biopsy of palpable cervical or supraclavicular lymph nodes, needle biopsy of a lung mass or mediastinal nodes using either CT or ultrasound guidance, mediastinoscopy, mediastinotomy, median sternotomy, video-assisted thoracoscopy, or conventional thoracotomy.
The treatment of superior vena cava syndrome depends on the etiology of the obstruction, the severity of the symptoms, the prognosis of the patient, and patient preferences and goals for therapy. Radiation therapy or chemotherapy should be withheld until the etiology of the obstruction is clear.
Surgical treatment of benign SVC syndrome is effective over the long term, with secondary endovascular interventions to maintain graft patency. Straight spiral saphenous vein graft remains the conduit of choice for surgical reconstruction, with results superior to those with other types of grafts.
Endovascular treatment is effective over the short term, with frequent need for repeat interventions. It does not adversely affect future open surgical reconstruction and may prove to be a reasonable primary intervention in selected patients. Patients who are not suitable for or who fail endovascular intervention merit open surgical reconstruction.