Overview: Trauma is a major cause of death in children and results primarily from motor vehicle accidents, although firearm injury (Fig. 83-1) and child abuse are other important causes of traumatic death. Survival of a child with a traumatic aortic injury until arrival at the emergency department is rare, accounting for one to two cases per year at large metropolitan level I pediatric trauma centers. Operative treatment involves fewer than 0.14% of all trauma patients, and only 6% of all traumatic ruptures of the aorta occur in patients younger than 16 years.^2,3 The outcome of traumatic aortic injury in the pediatric population is directly related to timely diagnosis, proper treatment, and hemodynamic status at the time of presentation.

Imaging: Chest radiographic findings such as pleural capping at the left lung apex, obscuration of the aortic arch, mediastinal widening, pleural effusion, pneumothorax, pulmonary contusion, tracheal and nasogastric tube deviation, and upper rib and clavicle fracture in the setting of blunt trauma should raise clinical suspicion for an aortic injury (Fig. 83-2). Historically, the definitive diagnosis of traumatic aortic injury was made by conventional catheter angiography. Today, computed tomographic angiography (CTA) has supplanted catheter angiography as the diagnostic method of choice.^4,5 CTA allows speedy and precise visualization of the traumatic aortic injury. Care should be taken to identify the location of aortic rupture, active extravasation of arterial contrast, a dissection flap extending to major aortic branches, hemothorax and hemopericardium, and other organ and musculoskeletal injuries.

Treatment and Imaging Follow-up: The goals of treatment of pediatric traumatic aortic rupture are identical to those in adults. The mainstay of treatment is operative repair of the aorta.⁶ Patients for whom surgery poses a high risk have been treated successfully with endovascular stent grafts, with deployment during adenosine-induced cardiac arrest. CTA should be performed immediately after stent placement, with a follow-up study in 48 hours to document the stability of the repair. Rarely, observational management for an intimal tear has been utilized in patients with comorbidities too severe to allow intervention.

Overview: Pulmonary embolism (PE) is an uncommon but potentially fatal disease in children.⁷ In pediatric patients with deep venous thrombosis and PE, the mortality rate from all causes has been reported to be as high as 16%, whereas the mortality rate directly attributable to deep venous thrombosis or PE was 2.2%.⁸ The most common risk factor for PE in children is catheter thrombosis, which develops in as many as 50% of patients with central venous catheters.⁹ Other risk factors are peripartum asphyxia, dehydration, septicemia, trauma and burns, surgery, hemolysis, malignancy, and renal disease such as nephrotic syndrome. Rarely, PE can be seen in the setting of intracranial venous sinus thrombosis and Klippel-Trénaunay syndrome. Abnormal coagulation factors associated with adult PE that also have been reported in children are antiphospholipid antibodies, factor V Leiden mutation, and deficiencies in protein S, protein C, and antithrombin III.¹⁰

Clinical diagnosis of PE often is difficult because most cases of venous thrombosis in children are silent. Symptoms of PE may be masked by intrinsic lung disease or other underlying illness. In one series, 40% of proven cases of PE were negative in the d-dimer assay. Therefore a negative d-dimer assay in pediatric patients cannot exclude PE. A high level of clinical suspicion in the presence of risk factors is imperative.

Imaging: Traditionally, catheter pulmonary angiography was considered the diagnostic gold standard.¹¹ In current clinical practice, catheter pulmonary angiography has been replaced by noninvasive CT pulmonary angiography (CTPA) performed with high-speed multidetector CT. The accuracy of the detection of PE by CTPA in an adult population has been studied in the Prospective Investigation of Pulmonary Embolism Diagnosis II trial.¹² With use of CT technology available before 2003, the sensitivity and specificity in this trial were reported as 83% and 96%, respectively. With advances in CT technology in the past decade that have improved spatial resolution, increased scan speed, and reduced contrast dose and radiation exposure, the diagnostic accuracy for PE likely is improved. Other imaging methods include nuclear ventilation-perfusion scanning and magnetic resonance pulmonary angiography.

As in adult patients, CTPA increasingly is being used to diagnose PE in children (Fig. 83-3), although its accuracy in children has not been studied by rigorous clinical trials. CTPA in children is technically challenging because of the small size of their pulmonary arteries, their inability to cooperate in holding their breath, and concerns about radiation exposure. The principal strategy for reducing radiation dose is to lower exposure factors such as x-ray tube voltage and tube current. Both maneuvers increase image noise and confound visual detection of PE. As a result, the CTPA protocol for children requires meticulous attention to optimize spatial resolution, scan speed, and exposure factors.

Treatment and Follow-up: Anticoagulation is the mainstay of medical therapy for persons with a PE. Thrombolytic therapy is reserved for persons with hemodynamic instability. Surgical pulmonary thrombectomy has been successfully performed in persons with central or saddle emboli.

PE can be caused by materials other than bland thrombus. Septic emboli can be the result of endocarditis and of thrombophlebitis. Lemierre syndrome describes jugular vein thrombosis associated with anaerobic infection of the head and neck (classically by Fusobacterium necrophorum), and more than 50% of these cases are complicated by septic emboli to the lungs.¹³ Tumor emboli may come from Wilms tumor, neuroblastoma, and hepatocellular carcinoma, because occasionally these tumors invade the inferior vena cava. Rarely, tumor emboli originate from primary cardiac tumors, such as atrial myxomas. Foreign bodies that embolize to the lungs include broken catheter tips and guide wires, misplaced embolization coils, and other endovascular devices. Finally, fat emboli may occur after major orthopedic trauma or surgery. In these situations, CT and magnetic resonance imaging (MRI) may help locate the source of emboli.

Overview: SVC syndrome (SVCS) is a clinical manifestation of gradual obstruction of SVC flow, leading to elevated central venous pressure of the upper extremities and the head, interstitial edema and swelling of the upper body, and development of venous collaterals to the inferior vena cava (IVC). In children, SVCS is a medical emergency because swelling of the neck can compress and obstruct their small airway more easily than in adults. The most common pediatric cause of SVCS is extrinsic compression of the SVC by non-Hodgkin lymphoma.¹⁴ The SVC can be compressed by other mediastinal masses, including germ cell tumor, infectious lymphadenopathy, aortic aneurysm, and mediastinal fibrosis.¹⁵ Luminal occlusion (Fig. 83-4) can be the result of a thrombus forming around a central venous catheter or pacemaker wires, or of venous thrombosis secondary to Behçet syndrome (see Chapter 82). Intrinsic stenosis of the SVC can be caused by scarring from a chronic indwelling catheter and by infusion of caustic agents. Finally, SVC flow may be obstructed within the atrial baffle after the atrial switch procedure or the Mustard-Senning procedure¹⁶ (see Chapter 76). Obstruction of the SVC above the azygos return precludes decompression by retrograde flow into the azygos vein and leads to more severe symptoms.

Imaging and Treatment: The gold standard for the diagnosis of SVCS is catheter venography, with which the level of SVC obstruction, the presence of venous collaterals, and the central venous pressure can be assessed. Noninvasive tomographic techniques such as CT and MR venography can define the SVC stenosis and are helpful in evaluating any extrinsic mass.¹⁷ An advantage of MRI is that venography can be done without use of a contrast agent through use of phase-contrast or time-of-flight inflow enhancement techniques. Treatment of SVCS depends on the underlying cause. Radiation or chemotherapy that reduces the tumor size may relieve the SVC obstruction. Thrombosed central venous catheters should be removed. Residual thrombosis may be treated with selective thrombolysis, and residual stenosis may be stented.

Overview: Reasons for acquired obstruction of the IVC are similar to those of the SVC. Thrombosis of the IVC can be the result of catheter access, placement of a caval filter, severe illness including sepsis and dehydration, and other hypercoagulopathy. The IVC can be obstructed at its entrance to the right atrium by abdominal tumors, such as Wilms tumor, neuroblastoma, hepatoblastoma, and hepatocellular carcinoma. The Budd-Chiari syndrome classically is attributed to hepatic venous obstruction, but the intrahepatic portion of the IVC can be involved, resulting in symptoms of hepatomegaly, ascites, and abdominal pain (Fig. 83-5).¹⁸ Obstruction is caused by thrombus or an IVC web.

Imaging and Treatment: Imaging evaluation can be performed with abdominal ultrasound, CT, and MRI, with the investigation focused on the location and severity of the obstruction and on the presence of a thrombus or extrinsic mass. Treatment is directed to correcting the underlying conditions. In the short term, patency of the IVC can be maintained with an endovascular stent.

Overview: Although a true SVC aneurysm is very rare, dilation of the SVC is more commonly seen in persons with elevated central venous pressure as a result of right heart failure or severe tricuspid valve regurgitation.¹⁹ Dilation of the SVC also is associated with mediastinal lymphatic malformation, although the pathophysiology is not known.²⁰ Patients with saccular SVC aneurysms may be at risk for SVC thrombosis and PE.

Imaging and Treatment: Surgical resection of an SVC aneurysm has been performed successfully. CT and MRI can help aid surgical planning by defining the extent of the aneurysm and detecting involvement of other draining veins.

Overview: Acquired pulmonary vein stenosis in children is uncommon but can be seen in children with complications of surgical repair of congenital pulmonary vein anomalies. Children who undergo repairs for total anomalous pulmonary venous connection (Fig. 83-6) and scimitar syndrome are at increased risk for acquired pulmonary vein stenosis. Pulmonary vein stenosis develops in up to 10% of infants who undergo repair of total anomalous pulmonary venous connection²¹; these patients often are very ill from pulmonary edema and poor oxygen saturation, with a mortality rate as high as 50%. The prognosis is worse for patients who have coexisting complex cardiac anomalies, often as part of the heterotaxy syndrome. Other acquired causes of pulmonary vein stenosis include mediastinal fibrosis and extrinsic compression by mediastinal tumors.

Imaging and Treatment: Catheter angiography is used to define the location of the pulmonary venous obstruction, and the severity of the stenosis can be evaluated by measuring the pressure gradient across the stenosis. With three-dimensional imaging capability, CTA and magnetic resonance angiography (MRA) often can identify the obstruction better than catheter angiography. CTA has the added advantage of evaluating the pulmonary parenchyma and airways for additional complications.

Pulmonary vein stenosis has been treated with angioplasty, endovascular stent placement, and surgical repair.21,22 Despite immediate postoperative success, restenosis often occurs, and mortality is not substantially improved. The pathophysiology of pulmonary vein restenosis is not well understood. Medial fibrosis of the injured pulmonary veins, endothelial ingrowth into the stent, and abnormal reactivity of the pulmonary vascular bed have been proposed as possible mechanisms of restenosis.

Overview: Pulmonary varices are rare aneurysmal dilations of the pulmonary veins²³ and may be congenital or acquired. Acquired pulmonary varices usually are the result of pulmonary venous hypertension, caused by central pulmonary vein stenosis, mitral regurgitation, mitral stenosis, and coarctation. Pulmonary varices generally are benign and require no specific treatment. They usually regress with correction of the underlying abnormality. However, it is important to distinguish pulmonary varices from pulmonary arteriovenous malformations, which can have a similar appearance. Pulmonary arteriovenous malformations carry the risk of stroke and other embolic events and require surgical removal or catheter embolization.

Imaging: Both CTA and MRA can detect pulmonary varices. In difficult cases, catheter angiography may be needed to differentiate varices from arteriovenous malformations.

Overview: Primary neoplasms of the great vessels are very rare; fewer than 400 cases have been reported in adults. Most of these malignant tumors are sarcomas. Of primary neoplasms that involve the aorta, fewer than 140 cases have been reported; most are undifferentiated sarcomas, with angiosarcoma being the next most common type of neoplasm.²⁴ These primary tumors have not been described in children. Secondary involvement of the great vessels by invasion or compression from a nearby, nonvascular tumor or by radiation vasculitis from radiation treatment can occur. Examples of secondary tumors include mediastinal lymphoma, germ cell tumor, teratoma, rare types of sarcomas, and mediastinal metastasis.^25,26

Imaging and Treatment: Because most great vessel tumors occur as a result of other disease processes, the tumor cell types and origins usually are known (see Chapter 81). The primary roles of imaging are to determine favorable sites for biopsy, evaluate the extent and the degree of vascular obstruction in preparation for vascular intervention, and monitor changes in vascular involvement after treatment. In most cases, CT or MRI is used for these purposes.²⁷ Treatment and imaging follow-up depend on the cell type and tumor staging.

Overview: Pseudoaneurysm and stenosis can develop as complications of surgical repair or interventional treatment of pediatric thoracic great vessels, of which coarctation is the best studied. The average restenosis rates are 15% and 2% for balloon angioplasty and surgical repair of coarctation, respectively (Fig. 83-7).²⁸ Other surgical procedures that can be complicated by aneurysm or stenosis are surgical aortopulmonary and central shunts.²⁹ The Blalock-Taussig shunt, which classically connects the right subclavian artery to the right pulmonary artery, can lead to stenosis or obstruction of the right pulmonary artery (Fig. 83-8). The Potts shunt, which connects the descending aorta to the left pulmonary artery, often results in left pulmonary artery stenosis. The Waterston shunt connects the ascending aorta to the pulmonary trunk. Control of shunt flow is difficult, and excessive flow can create a massive aneurysm of the pulmonary artery (Fig. 83-9). For these reasons, both Potts and Waterston shunts are rarely used today.

Imaging and Treatment: Noninvasive imaging by CTA or MRA has largely supplanted catheter angiography for the purpose of detecting and characterizing these thoracic vascular lesions before surgical or interventional treatment. Catheterization is reserved for angioplasty and stenting of stenotic lesions and for stent graft deployment to exclude an aneurysm.