The SVC carries approximately one-third of the cardiac venous return, constituting one of the great veins of the human body. It measures approximately 7 cm in length and is formed by the confluence of the right and left brachiocephalic veins. The azygos venous arch drains into the SVC posteriorly, just before it enters into the right atrium. Surrounding structures include the right phrenic nerve, the vagus nerve, and the pulmonary artery, as well as the pleura, the ascending aorta, the azygos arch, and the sternocostal junction. Half of the SVC is suspended with the pericardium: anteriorly it is free of any attachments, while posteriorly it lies in close relation to the left atrium, the right pulmonary artery, and the posterior and lateral pericardium [7]. Within the anterior-superior and middle mediastina, this great vein is bound by several anatomical structures that may play a role in the pathophysiology of the SVC syndrome. The wall of the SVC is fairly thin and easily compressible by any external masses, such as tumors, enlarged lymph nodes , or aortic aneurysms [5].

After the decrease in the incidence of tuberculous and syphilitic mediastinitis in the 1900s with the advent of antibiotic use, malignant tumors became the predominant cause of SVC syndrome (78–93% of cases). Non-small cell and small cell carcinoma, lymphoma, and thymoma are among the leading malignant causes of SVC syndrome [5]. Benign causes are responsible for approximately 40% of all SVC syndrome cases [8], of which indwelling catheters and pacemakers are responsible for up to 71%. Central intravenous catheterization and the use of cardiac pacemakers have significantly increased over the past 20 years. Up to 33% of patients who undergo these common procedures develop upper extremity and central venous thrombosis. Subsequently, SVC syndrome is reported in around 1–3% of patients with indwelling catheters and up to 3.3% of those with cardiac pacemakers. Some studies have suggested that this may be due to catheters placed in suboptimal positions or their short length size [9]. It is also thought that such procedures cause intimal injury predisposing to thrombosis [6]. Other benign causes include mediastinal fibrosis, granulomatous diseases, histoplasmosis, mediastinal radiation, venous thrombosis, hypercoagulable states, Bechet’s syndrome, tuberculosis lymphangitis, retrosternal goiter , and very rarely surgical iatrogenic injuries with oversewing of the junction of the right and left brachiocephalic veins [8, 10].

When the flow through the SVC is reduced by more than 60%, blood preferentially is redirected into smaller venous collaterals leading to several hemodynamic changes [11] (Fig. 42.3). Most patients with SVC syndrome are between 50 and 70 years of age with a male predominance [6]. The majority of patients with SVC syndrome remain asymptomatic throughout their lifetime; however, some of them present with features of edema in the head and neck region (60–100%), upper extremity edema (14–75%), distended neck/chest veins (27–86%), or facial plethora. The resultant interstitial edema and venous hypertension can also cause respiratory symptoms, such as cough (38–70%), dyspnea (23–74%), hoarseness, or stridor. Neurologic sequelae may be evident in up to 10% of cases, including syncope, cerebral edema, headaches, confusion, cerebrovascular accidents, and herniation [12].

Several scores have been devised to classify the degree of SVC syndrome [11]:

Taking a detailed clinical history and proper physical examination will most often lead to the diagnosis of SVC syndrome. The next step in the investigation consists of radiographic imaging. A chest x-ray is ordered initially, and around 84% of the chest x-rays show some sort of abnormal findings (widened superior mediastinum or pleural effusions) [5]. However, normal findings do not preclude the diagnosis of SVC syndrome. Venous duplex scanning has been found to be a helpful noninvasive tool in screening for SVC obstruction. An internal thoracic vein flow reversal is diagnostic of SVC syndrome [13]. It can also provide information about resolution of disease and return of normal flow pattern after treatment [14]. The duplex scanning may reveal bilateral jugular and subclavian vein thrombosis or engorged neck veins with abnormal venous flow pattern and loss of flow variation with respiration.

More accurate imaging techniques are computed tomography angiography and contrast-enhanced venography that confer higher sensitivity and specificity (>90%) [5]. They have been widely used in the diagnosis of SVC syndrome and in depicting the degree of central venous obstruction (Fig. 42.4). CT has the added benefit of identifying different benign and malignant structural causes. It can also delineate the small collateral pathways and venous shunts. On the other hand, venography is the gold standard in mapping out the venous circulation in preparation for endovascular or surgical repair . Stanford and Doty classified SVC syndrome into four types according to degree of stenosis and direction of flow through the azygous system [8, 15]. These patterns can identify those at risk for major life-threatening consequences and the need for immediate intervention [15].

Magnetic resonance venography (MRV) is another modality that has gained popularity in the diagnosis of central venous obstruction. Abnormal anatomical variations and compressing structures can easily be identified with this noninvasive modality. It can also outline the central venous circulation and associated collateral pathways [5].

Contrast-induced renal complications may limit the use of some of these diagnostic radiographic techniques. Some relative contraindications to venography include active cellulitis and iodinated contrast allergy. Patients who have aneurysm clips or specific non-MR compatible pacemakers should not undergo MRV.

Tissue diagnosis remains one of the most important factors, especially in malignant SVC syndrome. Specific treatment options rely on the histopathology of the obstructing mass discovered on imaging. Biopsy of lymph nodes, fluid cytology, and more invasive procedures such as bronchoscopy, mediastinoscopy, or thoracoscopy may be needed to identify the type of tumor involved and determine the staging of the disease [5]. It should be kept in mind that invasive diagnostic techniques come with higher morbidity and complication rates in patients with SVC obstruction as compared to those without it [16].

There are no established guidelines for the treatment of SVC syndrome. The clinical management should be tailored to each patient and the associated radiographic/pathologic findings. The management will depend on the acuity of the presentation, the severity of the symptoms, the etiology and degree of stenosis, and finally the life expectancy. The decision to intervene or proceed to palliation should be promptly reached. The approach to treatment can thus be divided into medical, surgical, or endovascular.