SUPERIOR VENA CAVA SYNDROME (SVCS)

DEFINITION clinical expression of obstruction of blood flow through the SVC developing quickly or gradually in case of pathological process in the superior mediastinum causing compression, invasion or thrombosis Characteristic symptoms and signs may develop quickly or gradually when this thin-walled vessel is compressed, invaded or thrombosed by processes in the superior mediastinum.

ANATOMY AND PATHOPHYSIOLOGY Thin – walled Compliant Easily compressible Vulnerable to any space occupying process in its vicinity Extensive collateral system (azygos venous system, internal mammary veins, lateral thoracic veins, paraspinous veins, esophageal venous network, subcutaneous veins) Maintains blood at a low pressure When the SVC is fully or partially obstructed, extensive venous collateral circulation may develop. The azygos venous system is the most important alternative pathway. Other collateral systems are: … The engorgement of subcutaneous veins in the neck and thorax is a typical physical finding in SVCS. Despite these collateral pathways, venous pressure is almost always elevated in the upper compartment if there is obstruction of the SVC.

The SVC is the major drainage vessel for venous blood from the head, neck, upper extremities and upper thorax.

It is located in the middle mediastinum and is surrounded by relatively rigid structures such as sternum, trachea, right bronchus, aorta, pulmonary artery and the perihilar and paratracheal lymph nodes. The SVC is completely encircled by chains of lymph nodes that drain all the structures of the right thoracic cavity and the lower part of the left thorax. The length of the SVC is 6-8cm and the width is 1,5 to 2cm.

The SVC extends from the junction of the right and left innominate veins to the right atrium. The azygos vein, the main auxiliary vessel, enters the SVC posteriorly.

ETIOLOGY Malignant conditions – 85% Lung cancer – underlying process in 70% Small cell lung cancer – the most common histologic subtype Lymphoma involving the mediastinum (8%) Other primary mediastinal malignancies: thymoma, germ cell tumors Metastatic mediastinal tumors (breast cancer, testis cancer) Malignant disease is the most common cause of SVCS. 85% of patients with SVCS suffer from different oncologic conditions with the most common one – lung cancer with the most often histologic subtype – small cell cancer. 5-15% of lung cancer patients develop clinical manifestation of SVCS. Lymphoma involving the mediastinum is the cause of SVCS in about 3-8% of the patients. Hodgkin’s lymphoma commonly involves the mediastinum but it rarely causes SVCS.

ETIOLOGY Nonmalignant conditions Thrombosis ( central vein catheters, pacemakers) Mediastinal fibrosis (e.g. due to radiotherapy or histoplasmosis) The increasing use of these devices for the delivery of chemotherapy agents or for hyperalimentation contributes to the development of SVCS in cancer patients.

ETIOLOGY IN CHILDREN Mainly iatrogenic (70%) – secondary to cardiovascular surgery for congenital heart diseases, ventriculoatrial shunt for hydrocephalus, SVC catheterization for parenteral nutrition Congenital anomalies of the cardiovascular system Mediastinal tumors (lymphomas in 75%) Obstruction of SVCS in pediatric age group is rare and has a different etiologic spectrum. The causative factors are mainly iatrogenic secondary to… Two thirds of the tumors causing SVCS in childhood are lymphomas.

SYMPTOMS Dyspnea 63% Facial swelling or 50% Head fullness Cough 24% Arm swelling 18% Chest pain 15% Dysphagia 9% Hoarseness SVCS usually has an insidious onset and progresses to typical symptoms and signs. Dyspnea is the most common symptom.

PHYSICAL FINDINGS Venous distention of neck 66% Venous distention of chest wall 54% Facial edema 46% Cyanosis 20% Edema of arms 14% Exophtalmus Symptoms and signs may be aggravated by bending forward, stooping or lying down.

DIAGNOSTIC PROCEDURES Chest film (superior mediastinal widening, pleural effusion, right hilar mass, bilateral diffuse infiltrates, cardiomegaly, calcified paratracheal nodes, mediastinal (anterior) mass) CT (more detailed information about the SVC, its tributaries and other critical structures such as bronchi and the cord) MRI Contrast venography (valuable if surgical bypass is considered for the obstructed vena cava); an alternative – radionuclide technetium-99m venography Clinical identification of SVCS is simple because the symptoms and signs are typical and unmistakable. Chest film shows a mass in most affected patients. The most common radiographic abnormalities are:… Computed tomography provides more detailed… The additional information is necessary because the involvement of these structures requires prompt action for relief of pressure. Magnetic resonance imaging is noninvasive modality. Contrast venography is controversial. It provides important information for determining if the vena cava is completely obstructed or remains patent and is extrinsically compressed. Some authors state that venography is relatively contraindicated because the interruption of the integrity of the vessel wall, in the presence of increased pressure, may result in excessive bleeding. Radionuclide technetium venography is minimally invasive method.

DIAGNOSTIC PROCEDURES Procedures that help to establish the histologic diagnosis are the priority! Sputum cytology Thoracocentesis (if there is pleural effusion) Supraclavicular lymph node biopsy Bronchoscopy (brushing, washing, biopsy samples) Percutaneous transthoracic fine-needle biopsy under CT or fluoroscopic guidance Mediastinoscopy Bone marrow biopsy Thoracotomy Small cell lung cancer and non-Hodgkin’s lymphoma ogten involve the bone marrow. If all other procedures failed, thoracotomy is diagnostic.

MANAGEMENT The treatment should be selected according to the histologic disorder and stage of the primary process! Goals: relieve symptoms attempt cure of the primary malignant process

METHODS Radiotherapy Chemotherapy Thrombolytic therapy Anticoagulants Transluminal angioplasty and endoprosthesis insertion Surgery General measures

RADIATION THERAPY Radiosensitive cancers (non-small cell lung cancer) Contraindications to chemotherapy Combination therapy: chemo- and radiotherapy (lymphomas, small cell lung cancer) Unknown histologic diagnosis in case of the deteriorating patient clinical status Radiotherapy is is used as the initial treatment if a histologic diagnosis cannot be established and the clinical status of the patient is deteriorating. The syndrome may be the earliest manifestation of invasive involvement of additional critical structures in the thorax, such as the bronchi. Under such circumstances prompt treatment with irradiation may be required without any delay.

CHEMOTHERAPY Provides both local and systemic therapeutic activity Chemosensitive carcinomas Lymphomas Small cell lung cancer * Alone or in conjunction with radiotherapy

INVASIVE METHODS Percutaneus transluminal angioplasty using baloon technique Insertion of expandable wire stents With or without thrombolytic therapy Successful in opening catheter induced SVC obstructions

SURGERY Bypass grafts In oncologic patients - considered only after other therapeutic methods have been exhausted Experience with successful direct bypass graft for SVC obstruction is limited.

TROMBOLYTIC THERAPY Streptokinase Urokinase Recombinant tissue-type plasminogen activator *May cause lysis of the thrombus early in its formation Successful experience with thrombolytic agents is limited to the treatment of catheter-induced SVCS.

Anticoagulants Heparin Oral anticoagulants * May reduce the extent of the thrombus and prevent progression

GENERAL MEASURES Bed rest with the head elevated Oxygen Steroids General measures may temporarily relieve the symptoms of SVCS. Bed rest with the head elevated plu oxygen administration can reduce cardiac output and venous pressure. Diuretic therapy and reduced-salt diet to reduce edema may have an immediate palliative effect but the risk of thrombosis enhanced by dehydration should not be ignored. Steroids may improve obstruction by decreasing a possible inflammatory reaction associated with tumor or with irradiation.

PROGNOSIS Strongly correlates with the prognosis for the underlying disease Average survival for cancer patients: 7-8 months 5 months for lung cancer patients Average survival in case of primary benign process: 9 years