The following module was designed to supplement medical students’ learning in the clinic. Please take the time to read through each section by clicking the headings below. Information on superior vena cava (SVC) syndrome is provided.

By the end of the tutorial, the following objectives should be addressed:

1. Describe the anatomy of the superior vena cava (SVC) and its role in venous drainage
2. Appreciate the pathophysiology underlying the development of SVC syndrome
3. Describe the possible causes of SVC syndrome
4. Describe the common signs and symptoms of SVC obstruction
5. Understand the general approach to diagnosis of SVC syndrome
6. Understand the imaging techniques used in the investigation of SVC syndrome
7. Understand the important factors to consider when treating SVC obstruction
8. Appreciate the variability in prognosis for patients with malignancy associated SVC syndrome

Superior vena cava (SVC) syndrome refers to the impediment of blood flow through the SVC caused by thrombosis, invasion, or compression by pathology involving nearby anatomical structures (ex. lymph nodes, right upper lobe of the lung, etc) [1]. SVC obstruction is considered a medical emergency that requires rapid assessment and management [2,3].

This module reviews the relevant anatomy, pathophysiology, etiology, clinical features, diagnostic approach, and management of SVC syndrome in patients with malignancy.

The superior vena cava (SVC) (Figure 1) is a vertically oriented vessel located in the superior mediastinum that extends from the confluence of the right and left brachiocephalic veins to the right atrium [3,4]. The SVC acts as a conduit that drains venous blood from the head, neck, upper extremities, and upper thorax into the right atrium [3].

Located in the mediastinum are other tributary veins of the SVC that play an important role in the pathophysiology underlying the development of SVC syndrome. These include (Figure 2): the azygos, internal mammary, lateral thoracic, paraspinous, and esophageal veins [1].

Impediment of blood flow in the superior vena cava (SVC) can be caused by: [1]

• Thrombosis in the SVC,
• Invasion, or
• Extrinsic pressure exerted by pathology involving nearby anatomical structures (ex. lymph nodes, right upper lobe of the lung, etc)

An obstructed SVC triggers the formation of venous collaterals as alternate routes for returning venous blood flow [1]. Collateral veins may be derived from SVC tributaries (see “Anatomy Review”) [1].

The clinical features of SVC syndrome manifest when the degree of obstruction is no longer adequately compensated for by the formation of venous collaterals. In patients with aggressive pathology leading to the rapid development of SVC obstruction, the signs and symptoms of SVC syndrome may present relatively early as there is insufficient time to establish collateral flow. Conversely, insidious disease processes (ex. fibrosing mediastinitis) may remain asymptomatic for years. [1]

The edema resulting from SVC obstruction often has minimal clinical consequence, although it can lead to the narrowing of nasopharyngeal passages and potentially cause stridor, dyspnea, hoarseness, cough, and dysphagia [1]. Cerebral edema is an extremely rare complication that can also occur due to SVC obstruction, with serious consequences including cerebral ischemia, herniation, and death [1].

Acute SVC obstruction may give rise to temporary drops in cardiac output that is usually rapidly restored by collateral flow and elevated venous pressure [1]. Hemodynamic disturbances are more likely due to mass effect on the heart rather than directly from the SVC obstruction [1].

The majority (60-85%) of superior vena cava (SVC) obstructions are due to malignant processes involving intrathoracic structures [1,3]. However, as the incidence of thrombosis induced SVC syndrome is rising due to the increased usage of intravascular devices, benign causes are now responsible for 15-40% of SVC obstructions [1,2,3].

The table below summarizes benign and malignant etiologies for SVC obstruction and the percentage of total cases each etiology accounts for: [1]

The signs and symptoms of superior vena cava (SVC) syndrome differs depending on the degree of SVC obstruction.  Patient presentation can range from asymptomatic in partial SVC obstructions, to the classic clinical features of central venous obstruction in complete SVC obstructions. [3]

The signs and symptoms of central venous obstruction are: [1,3]

• Dyspnea – most common symptom, present in 63% of patients [3]
• Facial edema – may worsen with recumbency
• Superficial distension of veins in the neck and/or chest wall
• Neurological symptoms may be observed in patients with cerebral edema
• Other symptoms include cough, hoarseness, dysphagia, arm swelling, and chest pain

“The 3 D’s” is a helpful mnemonic for recalling the major clinical features of SVC syndrome: [2]

• Dyspnea
• Distension (edema of face with erythema, edema of arms)
• Dilated chest wall veins

Superior vena cava (SVC) syndrome can often be diagnosed clinically in patients with overt presentations [1,3].  The following section will outline the appropriate clinical approach to investigating a patient with suspected SVC syndrome.

History

In SVC syndrome, special attention should be paid to the following areas on history taking [2]:

• Description of dyspnea
• Duration of symptoms
• Characterize cough (productive, hemoptysis, duration)
• Description of facial swelling (alleviating and aggravating factors)
• General health, review of systems
• Past Medical History (history of respiratory disease, CVS disease, smoking)

Physical Exam

In addition to performing the full physical examination, particular attention should be paid to the following areas [2]:

• Respiratory exam
• Clubbing
• Tracheal displacement
• Stridor
• Lymphadenopathy
• Examination of chest wall (skin colour, veins)

Imaging

SVC syndrome can often be diagnosed clinically in patients with overt presentations [1,3].  However, patients with minor signs and symptoms that are suggestive of SVC obstruction require further diagnostic imaging [1,3].

The following is a suggested algorithm for selecting the imaging modality appropriate for the initial evaluation of a patient with suspected SVC obstruction: [1]

The following section will focus on the management of superior vena cava (SVC) syndrome in patients with underlying malignancy. The main goals of therapy for malignancy related SVC syndrome are to relieve symptoms and to treat the primary malignancy [1,3].

Currently, there is a lack of evidence-based recommendations for the treatment of SVC syndrome [1].  The general approach to acute management is dependent upon the severity of symptoms, the characteristics of the primary malignancy, and the expected patient outcomes [1,2].  Present guidelines emphasize that histologic diagnosis take precedence over initiation of anti-tumor therapy, the only exceptions are patients who present with severe symptoms (central airway obstruction, respiratory compromise, or CNS depression) [1].  These patients require emergent treatment with endovenous stent placement and radiotherapy to prevent respiratory failure and death [1].  Based on this approach, a simplified treatment algorithm is depicted below: [1]

Also note that: [1]

• Short-term high-dose corticosteroid therapy is indicated in steroid-responsive malignancies and patients with laryngeal edema.
• The practicality of radiotherapy (RT) has been debated based on recent studies which assert that the majority of symptom relief is reliant on the formation of venous collaterals rather than RT.
• Diuretics may also be administered although the clinical evidence for improvement is equivalent to corticosteroid therapy alone or in combination with diuretics.

The patient prognosis of malignancy related superior vena cava (SVC) syndrome is highly variable depending on the primary malignancy implicated [1]. In general, the average life expectancy is approximately six months [1].

1. Drews RE, Rabkin DJ. Malignancy-related superior vena cava syndrome. In: UpToDate, Post TW (Ed), UpToDate, Waltham, MA. (Accessed on July 21, 2014).
2. Ingledew P. Oncology emergencies for medical students, PowerPoint presentation, FVCC, Surrey.
3. Nickloes TA. (2012). Superior vena cava syndrome. Retrieved July 21, 2014 from http://emedicine.medscape.com/article/460865-overview
4. Drake RL, Vogl W, Michell AW. Gray’s Anatomy for Students 2nd Edition. Elsevier Inc.; 2009.