Idiopathic internal mammary artery aneurysm in the setting of aberrant right subclavian artery.

Aneurysms of the internal mammary artery are extremely rare. Immediate treatment is necessary because of the high risk of rupture that can be life-threatening. Here we describe a case of idiopathic internal mammary artery aneurysm in a 54-year-old woman in the setting of aberrant right subclavian artery. The aneurysm was successfully treated with coil embolization without complications.

Aneurysms of the internal mammary artery (IMA) are extremely uncommon. Multiple case reports have described occurrence of these aneurysms after sternotomy, with complicated central venous catheter or pacemaker lead placement, and in connective tissue disorders (Ehlers-Danlos, Marfan, and Loeys-Dietz syndromes).2, 3, 4, 5, 6 However, very few case reports describe an idiopathic IMA aneurysm.1, 7 These aneurysms have variable presentations, including hemothorax, hemoptysis, and anterior mediastinal mass, or they can be found incidentally. The patient's consent for publication was obtained.

Case report

The patient is a 54-year-old woman with a past medical history significant for hypertension, diabetes mellitus, and end-stage renal and liver disease and a past surgical history significant for right upper extremity arteriovenous fistula. The patient presented to the Division of Vascular Surgery with an incidental computed tomography (CT) finding of a 2.4-cm right IMA aneurysm during evaluation for combination kidney-liver transplantation. A chest CT scan taken 20 months earlier showed the aneurysm size at 1.5 cm. CT angiography of the chest was performed at the time of presentation and showed the IMA aneurysm at 2.4 cm and an aberrant right subclavian artery (Fig 1). The patient denied any significant trauma or procedures to the chest. She did have a right-sided transjugular catheter placement for dialysis before her fistula but denied any trouble or difficulty during insertion. The patient was referred to the cardiothoracic surgery service for possible open repair of the aberrant right subclavian artery and IMA aneurysm, but because of the mild degree of dysphagia caused by the aberrant right subclavian artery, no further treatment was recommended. Therefore, endovascular repair of the right IMA aneurysm with coil embolization was performed.

Fig 1

Computed tomography (CT) angiography showing the internal mammary artery (IMA) aneurysm and the aberrant right subclavian artery.

Diagnostic angiography using a right common femoral artery approach demonstrated an aberrant right subclavian artery. This was cannulated using a VS catheter and Glidewire (Terumo Medical Corporation, Somerset, NJ). Injection arteriography through the tip of the VS catheter demonstrated a common trunk of the IMA and thoracodorsal arteries (Fig 2). Over Glidewire, a 90-cm 6F Raabe guiding sheath was advanced and successfully cannulated the proximal portion of the aberrant right subclavian artery, then a 5F multipurpose catheter was advanced over the Glidewire and successfully cannulated the proximal portion of the right IMA. Glidewire was then exchanged for a 0.014-inch soft wire, over which a 2.5F microcatheter was advanced in an attempt to cannulate the outflow artery of the IMA. Despite multiple attempts, the outflow could not be cannulated. Therefore, the microcatheter was removed, and a Gelfoam slurry was prepared; 2 mL of slurry was administered through the multipurpose catheter to embolize the IMA aneurysm. This was followed by reintroduction of the microcatheter, through which eight microcoils of 3 to 4 mm were placed in the inflow tract to the IMA aneurysm. Completion arteriography demonstrated minimal flow through the IMA (Fig 3).

Fig 2

Angiogram showing the common trunk of internal mammary artery (IMA) and thoracodorsal arteries. The IMA aneurysm is also demonstrated.

Fig 3

Coil embolization of internal mammary artery (IMA) aneurysm.

There were no perioperative complications, and the patient was discharged home the same day. The 30-day follow-up CT scan showed successful embolization, stable aneurysm sac, and complete thrombosis of the right IMA aneurysm.

Discussion

The anatomic course of the IMA makes it vulnerable to severe deceleration or penetrating injuries. These injuries can result in pseudoaneurysms of the IMA. Connective tissue disorders or infections are also frequent causes of IMA aneurysm. Idiopathic IMA aneurysm without a history of trauma or connective tissue disorders as described in our case is extremely rare. Although the IMA aneurysm in this case could be due to trauma during right transjugular venous catheter insertion, it is highly unlikely because of the uneventful placement. In the past 15 years, two idiopathic IMA aneurysms were described in the literature and were treated successfully using an open approach with uneventful recovery.1, 2, 3, 4, 5, 6, 7 The variable presentations of these aneurysms create a diagnostic dilemma. CT angiography and conventional angiography are required to delineate the IMA aneurysm and to plan the appropriate intervention. In this case, symptoms of IMA aneurysm were absent, and the aneurysm was found incidentally on chest CT during evaluation for transplantation. Whenever the diagnosis of IMA aneurysm is made, prompt therapy is highly recommended to prevent life-threatening complications, given that the majority of these pathologic processes are pseudoaneurysms in nature.

Multiple treatment options are described in the literature (open surgical repair, stent deployment, and coil embolization).1, 6, 7, 8 The Table summarizes previously reported IMA aneurysms regarding location, etiology, treatment, and outcome. Despite the lack of long-term results, an endovascular approach by coil embolization or stent deployment has become the treatment option of choice because of its minor invasiveness. However, open surgical repair is recommended in selected cases (large aneurysms causing compressive symptoms and the need for histologic examination).

Table

Previously reported internal mammary artery (IMA) aneurysms

Study	Location	Etiology	Treatment	Outcome
Okura et al1	Right IMA aneurysm	Idiopathic	Open ligation and resection	Uneventful recovery
Phan et al3	Left IMA aneurysm	Ehlers-Danlos syndrome	Thoracotomy (ligation of left IMA and hemothorax evacuation)	Uneventful recovery
Ohman et al4	Right IMA aneurysm	Loeys-Dietz syndrome	Coil embolization	Uneventful recovery
Common et al5	Left IMA aneurysm	Marfan syndrome	Coil embolization	Uneventful recovery
Burke et al6	Left IMA aneurysm	SMAD3 mutation	Coil embolization	Uneventful recovery
Heyn et al7	Left IMA aneurysm	Idiopathic	Open surgical resection	Uneventful recovery
Present case report	Right IMA aneurysm	Idiopathic	Coil embolization	Uneventful recovery

An aberrant right subclavian artery is the most common congenital abnormality of the aortic arch. Although it is mostly asymptomatic, the retroesophageal and retrotracheal course can result in progressive dysphagia, dyspnea, and aneurysmal formation. In our case, the aberrant right subclavian artery was causing mild dysphagia that did not require any intervention. The presence of an aberrant right subclavian artery in this case helped in reducing the risk of stroke associated with endovascular treatment of the arch vessels.

Conclusions

This case demonstrates that an endovascular approach with coil embolization is safe and feasible in treating right IMA aneurysm in the setting of an aberrant right subclavian artery.