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SVC SYNDROME
This document provides information on superior vena cava syndrome (SVC syndrome), including its anatomy, etiology, pathophysiology, clinical presentation, investigations, and classifications. It describes the normal anatomy of venous drainage from the head, neck and upper extremities via the brachiocephalic veins, internal jugular veins, subclavian veins and superior vena cava. SVC syndrome occurs when the superior vena cava becomes obstructed, most commonly due to lung cancer. This disrupts normal venous blood flow and leads to swelling, cyanosis and other symptoms as collateral circulation develops through veins like the azygos vein. The classification and presentation of symptoms depends on the level and severity of obstruction.
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SVC SYNDROME
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- 2. Anatomy of venousdrainage Etiology Pathophysiology Clinical features Investigations Treatment
- 3. Anatomy SVC originates inthe chest, behind the first right sternocostal articulation, from the confluence of two main collector vessels: Right and Left brachiocephalic veins which receive the ipsilateral internal jugular and subclavian veins. Internal jugular vein collects-----head and deep sections of the neck Subclavian vein---superior limbs, superior chest and superficial head and neck.
- 4. After the brachiocephalicconvergence, the SVC follows the right lateral margin of the sternum in an inferoposterior direction. Finally, it enters the pericardium superiorly and flows into the right atrium; No valve divides the SVC from right atrium. The SVC’s length ranges from 6 to 8 cm. Its diameter is usually 20-22 mm.
- 5. The blood pressureranges from -5 to 5 mmHg and the flow is discontinuous depending on the heart pulse cycle. The SVC receives a single affluent vein: the azygos vein. The azygos vein joins the SVC from the right side, at its mid length, above the right bronchus.
- 6. Azygos vein Azygos veintransports deoxygenated blood from the posterior walls of the thorax and abdomen into the superior venacava. It is formed by the union of Ascending lumbar veins with Right subcostal veins At the level of the 12th thoracic vertebra, Ascending in the posterior mediastinum, and arching over the right main bronchus posteriorly at the root of the right lung to join the superior vena cava. This "arch of the azygos vein― is an important anatomic landmark.
- 7. A major tributaryis the hemiazygos vein, a similar structure on the opposite side of the vertebral column. Other tributaries include Bronchial veins, Pericardial veins, and Posterior right intercostal veins. It communicates with the vertebral venous plexuses.
- 8. Hemiazygos vein It runssuperiorly in the lower thoracic region, just to the left side of the vertebral column. Hemiazygos vein and the accessory hemiazygos vein, when taken together, essentially serve as the left-sided equivalent of the azygos vein. It usually begins in the left ascending lumbar vein or renal vein, and passes upward through the left crus of the diaphragm to enter the thorax.
- 9. It continues ascendingon the left side of the vertebral column, and at the level of the 9th thoracic vertebra, it passes rightward across the column, behind the aorta, esophagus, and thoracic duct, to end in the azygos vein. The hemiazygos may or may not be continuous superiorly with the accessory hemiazygos vein. It receives the 9th, 10th, and 11th posterior intercostal veins and the subcostal vein of the left side, and some esophageal and mediastinal veins.
- 10. Accessory hemiazygos vein Receivesthe posterior intercoastal veins from the 4th, 5th, 6th, and 7th ICS. It either crosses the body of 8th thoracic vertebra to join the azygous vein or ends in the hemiazygos. When this vein is small, or altogether absent, the left superior intercostal vein may extend as low as the 5th or 6th ICS.
- 11. Posterior intercostal veins Thereare eleven posterior intercostal veins on each side. The 1st posterior intercostal vein, drains into the brachiocephalic vein or the vertebral vein. The 2nd and 3rd (and often 4th) posterior intercostal veins drain into the superior intercostal vein. The remaining posterior intercostal veins drain into the azygos vein on the right, or the hemiazygos vein and accessory hemiazygous on the left.
- 14. SVC obstruction In SVCobstruction, the azygos vein is responsible for the most important collateral circulation. According to the expected collateral pathways, the SVC can be divided into two segments: Supra-azygos or preazygos and Infra-azygos or postazygos SVC.
- 15. There are fourpossible collateral systems which were first described in 1949 by McIntire and Sykes. They are represented by 1. Azygos venous system, 2. Internal thoracic venous system, 3. Vertebral venous system and 4. External thoracic venous system. McIntire FT, Sykes EM jr. Obstruction of the superior vena cava: Ann Intern Med 1949; 30:925. 1.
- 16. 1. Azygos venous systemis the only direct path into the SVC. 2. Internal thoracic vein is the collector between SVC and inferior vena cava (IVC) via epigastric and iliac veins. 3. Vertebral veins with intercostals, lumbar and sacral veins, represent the posterior network between SVC and IVC. 4. External thoracic vein system is the most superficial and it is represented by axillary, lateral thoracic and superficial epigastric veins.
- 17. Etiology May be relatedto various etiological factors. Malignancies are predominant (95%) while, in the past, infectious diseases used to be common. During the last century, progression in antibacterial therapies and improvement in social conditions have led to a consistent decrease in the benign origin. Incidence of iatrogenic SVCS is currently increasing.
- 18. SVCS etiology Malignant Lung cancer Lymphomas Thymoma Mediastinalgerm cell tumors Mediastinal metastases Mesothelioma Leiomyosarcoma and angiosarcoma Neoplastic thrombi Anaplastic thyroid cancer
- 20. Benign Fibrosing mediastinitis (idiopathic orradiationinduced) Infectious diseases – Tubercolosis, Histoplasmosis, Echinococcosis, Syphilis, Aspergillosis, Blastomycosis, Filariasis, Nocardiosis. 1. 2. 3. 4. 5. 6. 7. 8. Thrombosis (nonneoplastic) Lymphadenopaties 1. sarcoidosis, 2. Behçet’s syndrome, 3. Castelman’s disease… Aortic aneurysm Substernal goiter Pericardial, thymic, bronchogenic cysts Iatrogenic 1. Pacemaker and defibrillator placement 2. Central venous catheters
- 21. Pathophysiology Pathogenetic basis ofSVCS is obstruction to the blood flow. It can result from intrinsic or extrinsic obstacles. Intrinsic—uncommon, caused by thrombosis or invading tissue. Extrinsic factors develop from compression or stricture of the vein. In physiologic conditions, blood return to the right atrium is facilitated by the pressure gradient between the right atrium and venae
- 22. When obstruction ofthe SVC occurs, the vascular resistances rise and the venous return decreases. SVC pressure may increase consistently. When SVC shows a significant stenosis (3/5 of the lumen or more), blood flow is redirected through the collateral circulation in order to bypass the obstruction and restore the venous return. images. Sy WM, Lao RS. Collateral pathways in superior vena cava obstruction as seen on gamma Br J Radiol 1982; 55:294-300 The timing of the obstruction development is important for its clinical implications.
- 23. In acute impairments,the blood flow is not rapidly distributed through the collateral network so symptoms arise markedly. In the case of slow-growing diseases, the collateral venous network has enough time to expand in order to receive the circulating volume. For this reason, long-lasting, severe SVC obstruction can sometimes be found without significant symptoms
- 24. Clinical presentation The SVCwall does not offer resistance to compression. When SVC lumen reduction is greater than 60%, hemodynamic changes occur: Proximal dilatation, Congestion and Flow slowdown. 1. 2. 3. The clinical signs of this condition are mainly represented by Cyanosis (due to venous stasis with normal arterial oxygenation) and Edema of the upper chest, arms, neck and face (periorbital initially).
- 25. Swelling is usuallymore important on the right side, because of the better possibility of collateral circulation in the left brachiocephalic vein compared to the contralateral. Vein varicosities of the proximal tongue and dark purple ears are also typical. Other signs or symptoms are: 1. Coughing, 2. Epistaxis, 3. Hemoptysis, 4. Dysphagia, 5. Dysphonia and 6. Hoarseness (caused by vocal cord congestion), 7. Esophageal, Retinal and Conjuntival bleeding.
- 29. In the caseof significant cephalic venous stasis--1. Headache, 2. Dizziness, 3. Buzzing, 4. Drowsiness, 5. Stupor, Lethargy and even coma may be encountered. Headache is a common symptom and it is usually continuous and pressing, exacerbated by coughing.
- 30. Epilepsy has beenoccasionally reported as well as psychosis, probably due to carbon dioxide accumulation. Dyspnea can be directly related to1. Mediastinal mass or 2. Pleural effusion or 3. Cardiocirculatory impairment. Supine position may worsen the clinical scenarios.
- 31. The clinical seriousnessis related to several factors: 1. Level of obstruction and rapidity of development, determining the effectiveness of collateral circulation 2. Impairment of lymphatic drainage (pulmonary interstitial edema or pleural effusion) 3. Involvement of other mediastinal structures (compression or invasion of heart, pulmonary artery and central airways, phrenic nerve paralysis…)
- 32. Superficial dilated vascularroutes are the main sign of collateral circulation and appear swollen and nonpulsating. In case of marked obesity, superficial veins can be missing at inspection. Variety of collateral circulation and the differences in the venous rearrangement are expression of the SVC obstruction site. Anatomic classification includes three levels of obstruction: 1. Obstruction of the upper SVC, proximal to the azygos entry point. 2. Obstruction with azygos involvement. 3. Obstruction of the lower SVC, distal to the azygos entry point.
- 33. Obstruction of theupper SVC, proximal to the azygos entry point. In this situation, there is no impediment to normal blood flow through the azygos vein which opens into the patent tract of the SVC. Venous drainage coming from the head neck, shoulders and arms cannot directly reach the right atrium. A longer but effective way is provided by several veins, the most important being the right superior intercostal vein.
- 34. From the superiortract of the SVC, blood flow is reversed and directed to the azygos, mainly through the right superior intercostal vein. Azygos collateral system is eminently deep; therefore the presence of superficial vessels is usually lacking, even if possible in the area of the internal thoracic vein’s superficial tributaries. Volumetric increase of the vessels can be consistent and capacity may increase up to 8 times. The efficiency of this collateral route is reliable, thus the clinical compensation is unbalanced only in the case of a rapid development of the obstruction or if the stenosis is more than 90%.
- 36. Obstruction with azygos involvement. Inthis case, the azygos vein cannot be available as collateral pathway and the only viable blood return is carried by minor vessels to IVC (cava-cava or anazygotic circulation). From the internal thoracic veins, blood is forced to the intercostal veins, then to azygos and hemiazygos veins. The flow is thus reversed into the ascending lumbar veins to the iliac veins.
- 37. Direct anastomosis betweenthe azygos’ origin and the IVC and between hemiazygos and left renal vein are also active. In addition, the internal thoracic veins can flow into the superior epigastric veins. From the superior epigastric veins, blood is carried to the inferior epigastric veins across the superficial system of the cutaneous abdominal veins and finally to the iliac veins. Another course is between the thoraco-epigastric vein (collateral of the axillary vein) and the external iliac vein.
- 38. In these conditions,the collateral circulation is partly deep and partly superficial. Physical examination often reveals SVC obstruction. The reversed circulation through the described pathways, remains less efficient than the azygos system and venous hypertension is usually more severe. For this reason, this kind of SVC obstruction is often related to important symptoms, dyspnea and pleural effusion. The ensuing slow blood flow may be responsible for
- 40. Obstruction of thelower SVC, distal to the azygos entry point. In this condition, the obstruction is just below the azygos arch. The blood flow is distributed from the superior body into the azygos and hemiazygos veins, in which the flow is inverted, to the IVC tributaries.
- 41. In this typeof case, the superficial collateral system is not always evident but the azygos and hemiazygos congestion and dilatation are usually important. The hemodynamic changes lead to edema and cyanosis of the upper chest and pleural effusion. Pleural effusion is often slowly-growing and rightsided, probably due to anatomical reasons: There is a wider anastomosis between hemiazygos and IVC than between azygos and IVC.
- 43. Classification of SVCS Thereare three main classification proposals which follow different methods of categorization. Doty and Standford’s classification (anatomical) 1. Type I: stenosis of up to 90% of the supra-azygos SVC 2. Type II: stenosis of more than 90% of the supraazygos SVC 3. Type III: complete occlusion of SVC with azygos reverse blood flow 4. Type IV: complete occlusion of SVC with the involvement of the major tributaries and azygos vein
- 45. Yu’s classification (clinical) 1. Grade0: asymptomatic (imaging evidence of SVC obstruction) 2. Grade 1: mild (plethora, cyanosis, head and neck edema) 3. Grade 2: moderate (grade 1 evidence + functional impairment) 4. Grade 3: severe (mild/moderate cerebral or laryngeal edema, limited cardiac reserve) 5. Grade 4: life-threatening (significant cerebral or laryngeal edema, cardiac failure) 6. Grade 5: fatal
- 46. Bigsby’s classification (operativerisk) Low risk High risk The low risk patients present: No dyspnea at rest, No facial cyanosis in the upright position, No change of dyspnea and No worsening of facial edema and Cyanosis, during the supine position. The high risk patients present facial cyanosis or dyspnea at rest in the sitting position.
- 47. Diagnosis Physical examination isoften crucial: Presence of edema and superficial venous network of the upper chest may support the clinical diagnosis. Imaging studies are however required. Most cases are suspected at the standard chest Xray and the most common radiological findings are right mediastinal widening and pleural effusion.
- 48. CT with multislicedetector is the most useful tool in the evaluation of the mediastinal syndromes. Intravenous contrast should be administered, in order to provide high-quality vascular imaging. Contrast enhanced multidetector CT may show Site of the obstruction, Some aspects of the primary disease and Eventual intraluminal thrombi. The contrast flow can also help to distinguish the extent of the collateral network
- 51. MRI plays aside role; it is indicated when CT cannot be performed (e.g. pregnancy, endovenous contrast intollerance). Invasive venography – Now arely used due to the huge improvement in vascular CT imaging. It is currently performed only as a preliminary to operative procedures such as stent placement. Once the thoracic imaging is obtained, the work-up should include brain, abdominal and bone studies in view of the probable malignant nature of the primary lesion. Recently Fluorodeoxyglucose-Positron Emission Tomography has gained an important role.
- 52. The histological diagnosisremains the key factor for the causative treatment, in the case of neoplastic etiology. Superficial adenopathies have to be carefully investigated in order to find a possible source of tissue and the easiest target for biopsy. The invasive diagnostic procedure varies largely depending on the suspected malignancy and its site.
- 53. The biopsy canbe obtained through Traditional bronchoscopy or Echo-guided endoscopy, Superficial node biopsy, Mediastinoscopy, Mediastinotomy, Transthoracic needle biopsy, Thoracoscopy, Cervical or supraclavicular biopsies; Thoracotomy and sternotomy are rarely indicated.
- 54. Treatment Therapy should becausative. Syndrome management recognizes different levels of priority depending on the 1. Severity of symptoms, 2. Etiology and 3. Prognosis. The therapeutic plan is usually targeted to clinical palliation. In fact, most cases are diagnosed as advanced-stage malignancies.
- 55. Supportive Care Elevate thepatient’s head to decrease the hydrostatic pressure and thereby the edema. Oxygen, Glucocorticoid therapy (dexamethasone, 4 mg every 6 hours) is commonly prescribed, although its effects have not been formally well studied, Glucocorticoids reduce the tumor burden in lymphoma and thymoma and are therefore more likely to reduce the obstruction in pts with lymphoma or thymoma than in those with other types of tumor.
- 56. Loop diuretics arealso commonly used, but it is unclear whether venous pressure distal to the obstruction is affected by small changes in right atrial pressure. In malignancy, the treatment can have palliative or, rarely, curative intent. Chemotherapy is usually employed in lymphomas, small-cell lung cancer and germ cell tumors. Besides chemotherapy, radiotherapy is widely used in the treatment of non-small cell lung cancer.
- 57. Some cases mustbe approached as an emergency. In this type of situation, the treatment of choice is usually endovascular with the aim of restoring blood flow as soon as possible. Acute lifethreatening presentation is the only situation in which radiotherapy before histological diagnosis can be considered. However, this approach should be avoided, whenever possible. RT prior to biopsy may obscure the histologic diagnosis.
- 58. Current guidelines stressthe importance of accurate histologic diagnosis prior to starting therapy, and the upfront use of endovascular stents in severely symptomatic patients to provide more rapid relief than can be achieved using RT. Kvale PA, Selecky PA, Prakash UB, American College of Chest Physicians. Palliative care in lung cancer: ACCP evidencebased clinical practice guidelines (2nd edition). Chest 2007; 132:368S.
- 59. Important exceptions tothis general approach are pts who present with stridor due to central airway obstruction or severe laryngeal edema, and those with coma from cerebral edema. These situations represent a true medical emergency, and these patients require immediate treatment (stent placement and RT) to decrease the risk of sudden respiratory failure and death.
- 60. For pts whohave obstruction of the SVC resulting from intravascular thrombus associated with an indwelling catheter, removal of the catheter is indicated, in conjunction with systemic anticoagulation to limit extension of thrombus. Radiation therapy — RT provides considerable relief by reducing tumor burden Symptomatic improvement is usually apparent within 72 hours. Relief of symptoms may not be achieved for up to four weeks, and approximately 20 percent of pts do not obtain symptomatic relief from RT
- 61. The benefits ofRT are often temporary, with many patients developing recurrent symptoms before dying of the underlying disease Particularly if symptoms are severe, more rapid palliation can be achieved through the use of an intraluminal stent, followed by RT for disease control. Stent placement is also effective in relieving symptoms in patients who fail to respond to RT.
- 62. Endovascular stents The placementof an endovascular stent restores venous return and provides rapid and sustained symptom palliation in pts with SVC syndrome. The technical success rate is in the range of 95 to 100%, and over 90% of pts report relief of symptoms Endovascular stenting provides fast functional relief.
- 63. Indications It is auseful procedure for pts with severe symptoms (eg, stridor) who require urgent intervention. Can be placed before a tissue diagnosis is available, For rapid symptom palliation in pts with NSCLC and mesothelioma and for those with recurrent disease who have previously received systemic therapy or RT.
- 64. Complications Reported in 3to 7% of patients. Early complications include Infection, Pulmonary embolus, Stent migration, Hematoma at the insertion site, Bleeding, and Rarely, perforation or rupture of the SVC.
- 65. Late complications include Bleeding (1 to 14 percent) and Death (1 to 2 percent) from anticoagulation and Stent failure with reocclusion. Stent failure is most often caused by thrombus or tumor ingrowth. However, since most pts with malignancy related SVC syndrome have a short life expectancy, the stent usually remains patent until death.
- 66. If reocclusion doesoccur, it can be treated with a second stent or thrombolytic therapy, with good secondary patency rates. Need for long-term anticoagulation — Short-term anticoagulation/antiplatelet therapy is often recommended But whether long-term treatment is necessary is an area of uncertainty
- 67. Surgical intervention Although effectiveand a/w relatively few complications, surgical bypass is rarely performed in pts with malignant cause of SVC syndrome because of the success of endovascular stenting. Surgical management is more often undertaken in patients with benign causes of SVC syndrome. Surgical resection of mediastinal tumor and reconstruction of the SVC is rarely considered in view of its morbidity and mortality and the limited life expectancy of most pts who present with this complication.
- 68. One possible exceptionis malignant thymoma and thymic carcinoma, which are relatively resistant to chemotherapy and radiation The main proposal for SVC resection is direct infiltration in thymomas or in N0-N1 non-small cell lung cancer. In case of infiltration of < 30% of the SVC circumference, direct suture is favored
- 69. Larger involvements requirea prosthetic repair. Armoured PTFE grafts and biologic material are the preferred choices. Morbidity after SVC surgical procedures is high and the post-operative care must be intensive. Long-term patency of a SVC by-pass graft is uncertain but, usually, the slow onset of the graft thrombosis favors the development of effective collateral circulation.