Continuing Education Activity

Superior vena cava (SVC) syndrome is a collection of clinical signs and symptoms resulting from either partial or complete obstruction of blood flow through the SVC. This obstruction is most commonly a result of thrombus formation or tumor infiltration of the vessel wall. The superior vena cava is formed by the junction of the left and right innominate (brachiocephalic) veins and is tasked with returning blood from the head, neck, upper extremities, and torso back to the heart. Today, this syndrome is most commonly seen secondary to malignancy, although there has been a more recent rise in benign etiologies. This activity describes the causes, pathophysiology, and presentation of superior vena cava syndrome and highlights the role of the interprofessional team in its management.

Objectives:

• Describe the causes of superior vena cava syndrome.
• Review the pathophysiology of superior vena cava syndrome.
• Summarize the treatment options for superior vena cava syndrome.
• Explain the importance of improving care coordination among interprofessional team members to improve outcomes for patients affected by superior vena cava syndrome.

Introduction

Superior vena cava (SVC) syndrome is a collection of clinical signs and symptoms resulting from either partial or complete obstruction of blood flow through the SVC. This obstruction is most commonly a result of thrombus formation or tumor infiltration of the vessel wall. The superior vena cava is formed by the junction of the left and right innominate (brachiocephalic) veins and is tasked with returning blood from the head, neck, upper extremities, and torso back to the heart. Today, this syndrome is most commonly seen secondary to malignancy, although there has been a more recent rise in benign etiologies. The resulting venous congestion produces a clinical scenario relating to increased upper body venous pressures. The most common signs and symptoms include face or neck swelling, upper extremity swelling, dyspnea, cough, and dilated chest vein collaterals.[1][2][3]

Etiology

SVC syndrome saw a dramatic decrease throughout the twentieth century. Today, the majority of SVC syndromes are the result of mediastinal malignancies, primary among which are small cell bronchogenic carcinoma. The second most commonly associated malignancy is non-Hodgkins lymphoma, followed by metastatic tumors. In addition, benign or nonmalignant causes of superior vena cava syndrome now comprise at least 40% of cases. Iatrogenic thrombus formation or SVC stenosis is a growing etiology due to pacemaker wires and semipermanent intravascular catheters used for hemodialysis, long-term antibiotics, or chemotherapy.[4][5]

Epidemiology

An estimated 15,000 cases of SVC syndrome occur each year in the United States, with studies pointing to increasing frequency due to the concomitant rise in the use of semipermanent intravascular catheters. The incidence of SVC syndrome reported in the literature range from 1 in 650 to 1 in 3100 patients.

Pathophysiology

The SVC is part of the low-pressure venous system containing thin walls susceptible to damage by a variety of pathologic mechanisms. These mechanisms can be divided into three categories which are compromised vessel anatomy, impaired venous flow, and diminished vessel wall integrity. These mechanisms often coexist in patients presenting with SVC syndrome. Extrinsic compression and obstruction of the SVC by a mass in the mediastinum is the most common cause of SVC syndrome. This is often associated with malignancy; however, there are a variety of nonmalignant masses as well as dilation of the overlying aorta that can cause compression. A growing proportion of SVC syndromes are now associated with occlusive venous thrombus formation that compromises venous flow back to the heart. The increasing use of indwelling intravascular devices such as catheters and pacemakers and implantable cardioverter-defibrillator (ICD) leads have played a major role in this growth. Resultant venous wall inflammation, fibrosis, and eventual thrombus lead to stenosis of the vessel itself.[6][7][8]

History and Physical

The diagnosis of SVC syndrome is made largely based on a patient’s history and physical findings, which often develop over a period of days to weeks. This insidious onset is a result of a collateral vascular network that exists to divert blood to the lower body, where it is then returned to the heart through the inferior vena cava, azygous vein, and the intercostals. The clinical findings in SVC syndrome are closely linked to venous congestion and the resultant elevation in venous pressures seen in the upper body. A careful physical examination is often sufficient to rule out a cardiogenic origin to the patient’s symptoms. The most common presenting symptoms of SVC syndrome are face/neck swelling, distended neck veins, cough, dyspnea, orthopnea, upper extremity swelling, distended chest vein collaterals, and conjunctival suffusion. Other less common symptoms of SVC syndrome include stridor, hoarseness, dysphagia, pleural effusion, head plethora, headache, nausea, lightheadedness, syncope, change in vision, altered mental status, upper body edema, cyanosis, papilledema, stupor, and coma. Some rare but serious clinical consequences reported in SVC syndrome include cerebral edema and upper respiratory compromise secondary to edema of the larynx and pharynx.

Evaluation

Patients with high clinical suspicion for SVC syndrome should undergo imaging of the upper body and vasculature. Ultrasound of the jugular, subclavian, and innominate veins can help to identify a thrombus within the vessel lumen. Radiographic imaging and MRI also play a critical role in providing additional information as to the location, severity, and etiology of the SVC obstruction. CT of the chest with the presence of collateral vessels is associated with a diagnostic sensitivity of 96% and a specificity of 92%. Venography is widely accepted as the gold standard for visualizing and diagnosing a venous obstruction. This modality should be used concomitantly with endovascular intervention for patients with a severe presentation of SVC syndrome.[9][10]

Treatment / Management

Following a clinical diagnosis, supportive therapy and medical management are commonly initiated. This involves elevation of the patient’s head as a simple maneuver with the goal of decreasing venous pressure. Further management is guided by the patient’s underlying SVC syndrome etiology. For patients with thrombus related to an indwelling intravascular device, removal should be considered along with anticoagulation therapy and catheter-directed thrombolysis. Multidisciplinary treatment planning for those with obstruction due to malignancy is important as tumor type, and staging can help to guide appropriate chemotherapy or radiation therapy. Open surgical repair through bypass grafting with spiral saphenous vein, femoral vein, polytetrafluoroethylene (PTFE) graft, or Dacron graft have traditionally been considered to overcome SVC obstruction. However, this is now reserved for cases in which recanalization through endovascular repair is either not possible or has previously failed. With expanding treatment options for both benign and malignant etiology, endovascular therapy is now widely considered the first-line treatment for SVC syndrome. Less invasive endovascular management can offer patients immediate relief of symptoms. Acute or subacute thrombus can be managed with catheter-based thrombolysis or thrombectomy prior to venoplasty and stent placement. [11][12][13]

Differential Diagnosis

• Cardiac tamponade
• Mediastinitis
• Thoracic aortic aneurysm
• Tuberculosis

Pearls and Other Issues

A widely accepted and standardized set of criteria outlining presentation severity does not exist for SVC syndrome.

The Kishi Scoring System for Signs and Symptoms of SVC syndrome grades severity based on the patient’s clinical presentation.

Included in this scoring system are the patient’s neurologic symptoms, laryngopharyngeal or thoracic symptoms, nasal and facial signs or symptoms, as well as the presence of venous dilatation.

Enhancing Healthcare Team Outcomes

Because there are many causes of SVCS, the condition is best managed by an interprofessional team of health care workers that include a vascular surgeon, interventional radiologist, radiation therapist, oncologist, pain specialist, and cardiac surgeon. The nurse plays a vital role in the monitoring of these patients. Many of them have cerebral and laryngeal edema and need close monitoring. The pharmacist should be fully aware of the drugs used to manage SVCS, which include corticosteroids and diuretics. Because many of these patients have an unpredictable course, radiation is often administered as a palliative measure to shrink the tumor and relieve the symptoms. Patients with Hodgkin's cancer are managed with chemotherapy. [14][15] [Level 3]

Outcomes

The prognosis of patients with SVCS depends on the cause. For patients with a benign cause of SVCS, the life expectancy is not changed, but for malignant cases, there is a significant drop in survival. Individuals who have features of cerebral and laryngeal edema can develop life-threatening symptoms and suddenly die. Patients with SVCS as a result of lung cancer usually live less than 24 months. For those who do not respond to radiation treatment, the survival is less than a year.[16][17][18] [Level 5]