Successful Treatment of Giant Left Subclavian Artery Pseudoaneurysm Abutting the Arch of the Aorta and Descending Aorta.

A 28-year-old woman presented with 3-month history of fever of unknown origin and progressively increasing cough. She was diagnosed with pulmonary tuberculosis on bronchial lavage cultures. A chest X-ray performed on follow-up showed a new opacity in the left apical area of the chest. Computed tomography scan of chest showed a large 10 cm pseudoaneurysm of the left subclavian artery 1 cm from its take off from the arch of the aorta. The pseudoaneurysm was approached through a left posterolateral thoracotomy and opened following a proximal and distal control. A 3 cm longitudinal defect was identified in the subclavian artery within its intrathoracic portion. This was debrided and repaired with an autologous pericardial patch. The patient had an uneventful recovery and remained well on follow-up.

INTRODUCTION

A true aneurysm is a localized dilatation of an artery including all its walls. In contrast, a pseudoaneurysm is a hematoma formed by the leakage of blood following a breach in the arterial wall. The blood is contained by surrounding soft tissue or adventitia, and a patent lumen connects the pseudoaneurysm and artery.

Pseudoaneurysms have been associated with atherosclerosis,[1] trauma caused by central vein cannulation,[2] thoracic outlet syndrome,[3] clavicular fractures,[4] and infection (mycobacterial, syphilitic, and bacterial). Computed tomography (CT) scans provide sufficient evidence for their diagnosis. They represent about 0.1% of all peripheral arterial aneurysms.[5]

A large subclavian artery pseudoaneurysm is a rare but possibly lethal condition.[6] These aneurysms most commonly occur after iatrogenic injury to the subclavian artery and can rupture, thrombose, embolize, or cause symptoms by local compression.[7] Subclavian artery pseudoaneurysms are difficult to manage because of their proximity to vital intrathoracic structures and cannot be readily compressed due to the potential for damage of downstream organs. The risk of rupture with pseudoaneurysms is also high since they lack support from the arterial wall.

Subclavian artery pseudoaneurysms usually require surgical repair. Usually, in a case of right subclavian artery aneurysm (SAA), a median sternotomy is performed and in a case of left SAA, lateral thoracotomy is preferred. In the modern era, it is also possible to manage subclavian artery pseudoaneursyms using intraluminal stents.[8]

CASE REPORT

A 32-year-old woman presented to the clinic with fever of unknown origin and a progressively increasing cough for the past 3 months. She also had hoarseness of voice and complained of odynophagia for the past 3 weeks.

Further history revealed that her fever had started intermittently approximately 10 months ago. A month later, she became pregnant but it was an ectopic pregnancy that ruptured after 6 weeks. She was admitted to the hospital and underwent a laparoscopic exploration. Cultures taken from the fallopian tube were positive for Mycobacterium tuberculosis. During her 10 day hospital stay, she developed sepsis and an adult respiratory distress syndrome. She was shifted to Intensive Care Unit and a central line was placed in her left subclavian vein. Her tracheal cultures revealed growth of Pseudomonas aeruginosa. Her blood cultures revealed the presence of Enterobacter cloacae. Bronchial lavage confirmed diagnosis of pulmonary tuberculosis (TB) and the absence of any malignancy. Antibiotics and anti-TB medications were started. The patient subsequently improved and was discharged home.

The patient was a mother of two children, both born of vaginal deliveries without complications. She had no other comorbidities and had no family history of TB.

She presented again 2 months later complaining of vomiting, headache, exertional dyspnea, inability to talk, and difficulty opening left eye. There was also a history of significant weight loss over the past month. A brain magnetic resonance imaging revealed disseminated central nervous system TB. Her anti-TB regiment was adjusted by increasing the number of drugs. She was noted to have a left-sided hemiparesis but gradually recovered and was discharged home.

Approximately 2 months later, the patient represented with a complaint of hoarseness of voice and odynophagia. A chest radiograph revealed a superior mediastinal mass on the left. A follow-up CT scan of the chest showed a large subclavian artery pseudoaneurysm measuring 74 mm × 57 mm size on the left not involving the aortic arch but adjacent to the aortic knuckle. A CT angiogram [Figure 1] confirmed a large left subclavian artery pseudoaneurysm.

Figure 1

Computed tomography angiogram of the thoracic aorta showing large pseudoaneurysm arising from the left subclavian artery measuring about 74 mm × 57 mm

Her hoarseness and odynophagia were attributed to compression effects of the aneurysm on the trachea, esophagus, and recurrent laryngeal nerves. It was also noted that her radial artery blood pressures on the right side were higher than that on the left. Upon speculation, cause of the aneurysm could have been because of either TB or injury by central venous pressure line.

The preoperative diagnosis was left subclavian artery pseudoaneurysm possibly mycotic or related to central line injury.

Repair of the aneurysm was performed through a left posterolateral thoracotomy incision and the fourth intercostal space was entered. Pleural adhesions were excised and a large mass was visible. CT angiogram had revealed a 1 cm distance of the mass's origin from the aorta so dissection around left subclavian artery was done to achieve the proximal control. The aneurysmal sac was opened and found to be a pseudoaneurysm [Figure 2]. Distal control was achieved. A pericardial patch was used to repair the 3 cm longitudinal defect in the left subclavian artery wall. Multiple mediastinal lymph nodes and the excised wall were sent for histopathology. Lymph nodes were reported as showing chronic granulomatous inflammation without necrosis (most likely due to Tb) and were negative for fungal hyphae or any malignancy. The excised wall showed a completely necrosed tissue.

Figure 2

Repairing wall of subclavian artery after opening of the aneurysm

The patient tolerated the procedure well. She had an uneventful recovery and was discharged within a week. She was followed for another 2 months and was doing well when last seen.

DISCUSSION

Intrathoracic SAAs can be asymptomatic or present with symptoms such as chest pain, shoulder pain, dysphagia, hoarseness, Horner's syndrome, or venous congestion. Extrathoracic SAAs most commonly present as tender pulsatile masses in the superior fossa, and Horner's syndrome can also be a presentation of an extrathoracic arterial aneurysm.[39]

Surgery is the main treatment for SAAs.[3] Location of the aneurysm determines the surgical approach taken. For extrathoracic SAAs, supraclavicular incision is adequate for aneurysmectomy. An intrathoracic SAA on the right side is best managed by median sternotomy whereas lateral thoracotomy is preferred for the left intrathoracic SAAs.[1] Resection or aneurysmorrhaphy is preferred over simple ligation because continued growth and rupture of ligated aneurysm have been reported.[1] In many patients with a proximal left SAA, the orifice of the subclavian artery is fragile and dilated so reconstruction by anastomosis or direct closure of the artery with a patch graft can be challenging.[1] Pericardial patch was used in this case because of its durability and lower risk for infection or rejection.

Recently, as a less invasive alternative to surgical repair, endovascular stent-graft treatment has become possible.[8] However, experience with the use of stent's for SAA's remains limited because of its relative infrequency.[10] In this case, stenting was not considered as a method for treatment due to lack of expertise available and the impending risk of rupture.

CONCLUSION

We described a rare and challenging case of a patient with a presumed mycotic pseudoaneurysm of the left subclavian artery.

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Conflicts of interest

There are no conflicts of interest.