Kommerell's diverticulum is an aneurysm originating from an aberrant subclavian artery from the descending aorta. As compared with the occurrence of an aberrant right subclavian artery originating from the descending thoracic aorta in a patient with a left-sided aortic arch, noted in the original reported case,1 an aberrant right subclavian artery from a right-sided aortic arch is much less common, occurring in approximately 0.1% of affected individuals.2 This malformation carries the risk of rupture or dissection; thus, various surgical methods have been presented including a hybrid approach,3 although the surgical strategy remains controversial and it is important to select an appropriate approach for individual patients. Conventional treatment for this malformation includes complete removal of Kommerell's diverticulum, with or without reconstruction of the subclavian artery via a median sternotomy and thoracotomy, although that is thought to be associated with high rates of mortality and morbidity. Herein, we report a case of Kommerell's diverticulum associated with an aberrant left subclavian artery and right-sided aortic arch in which we performed a single-stage total arch replacement using that open stent graft through only a median sternotomy.
A 72-year-old man was referred to our hospital because of an expanding dilated descending thoracic aneurysm. There was no dysphagia or respiratory discomfort, and physical examination findings were unremarkable. Enhanced computed tomography (CT) revealed a right-sided aortic arch and dilated descending aorta, 53 mm in diameter, from which an aberrant left subclavian artery originated as the fourth aortic arch branch (Figs. 1A, B). The first aortic branch was the left carotid artery, followed by the right carotid artery, right subclavian artery, and finally the aberrant left subclavian artery, which arose from Kommerell's diverticulum (Figs. 1C, D). Because the aneurysm showed rapid dilation, surgical treatment was considered. Initially, we intended to perform an endovascular repair with bypass of the cervical branches, although that was later ruled impossible because of the sharp angle of the arch and anatomical position of the branches. Thus, we decided to perform a total arch replacement with a frozen elephant trunk using newly available aortic stent graft (J Graft open stent graft; Japan Lifeline Co, Ltd, Tokyo, Japan) to avoid a right thoracotomy.
Through a median sternotomy with a Y-collar skin incision, cardiopulmonary bypass was established by cannulation of the ascending aorta and bicaval venous drainage after dissection of the three arch vessels and distal portion of the aberrant left subclavian artery. At the same time, an artificial conduit (part of the four-branched prosthetic graft) was anastomosed to the left axillary artery in an end-to-side fashion. During cooling, the ascending aorta was cross-clamped and a proximal anastomosis was performed with the end of the prosthetic graft in an everted position. With the patient under hypothermia at a core temperature of 25°C, antegrade cerebral perfusion was started through the artificial conduit anastomosed to the left subclavian artery, with balloon-tipped catheters inserted into the right and left common carotid arteries, and right subclavian artery. Next, the proximal end of the left common carotid artery was closed with mattress sutures using Teflon felts; then, the distal portion of the aorta was opened under circulatory arrest of the lower body. The J Graft was inserted between the right common carotid artery and left common carotid artery (after the second branch) and deployed. After fixation of the end of the graft, distal anastomosis of the four-branched prosthetic graft was performed, followed by a restart of cardiopulmonary bypass and declamping of the aorta. During rewarming, the aortic arch was reconstructed in the order of the left common carotid artery, right common carotid artery, and right subclavian artery. An artificial conduit anastomosed to the left subclavian artery was passed through the left chest cavity and anastomosed to a branch of the prosthetic graft. Finally, coil embolization was performed through the catheter via the distal portion of the left axillary artery (Fig. 2A). The postoperative course was uneventful. The patients was extubated 40 hours after operation and the duration of intensive care unit was 60 hours. Postoperative CT scanning revealed complete exclusion of Kommerell's diverticulum (Fig. 2B).
Various treatment approaches have been proposed for Kommerell's diverticulum with a right-sided aortic arch and aberrant left subclavian artery, including surgery via a median sternotomy alone (usually total arch replacement with an elephant trunk and subsequent thoracic endovascular aortic repair), thoracotomy alone, and a median sternotomy plus a thoracotomy or clamshell approach (total arch replacement with replacement of Kommerell's diverticulum), as well as a hybrid endovascular repair method.2,3
A total arch replacement procedure with replacement of Kommerell's diverticulum via a thoracotomy and median sternotomy has been conventionally applied for aneurysmal formation in cases of Kommerell's diverticulum to prevent its rupture or dissection. However, that has been found to be associated with high rates of mortality and morbidity.2 To reduce the invasiveness of such a radical approach, various two-stage methods have been proposed.3 Although thoracic endovascular aortic repair with a cervical vessel bypass is less invasive, it is technically difficult and sometimes impossible to perform because of a sharply angled aortic arch because of the risk of an endoleak.
For the present case, we adopted a single-stage procedure via a median sternotomy alone without a right thoracotomy, because replacement of Kommerell's diverticulum via a right thoracotomy can be difficult and is associated with high morbidity due to the anatomical position. The advantages of the present procedure were secure fixation of the proximal stent portion and a secure distal anastomosis to avoid bleeding. Furthermore, anatomical antegrade reconstruction of the cervical vessels was possible via our approach. Because of avoidance of a thoracotomy and well-controlled hemostasis, the patient quickly recovered without complications.
Seven previous reports of treatment of Kommerell's diverticulum with a right-sided aortic arch and aberrant left subclavian artery via only a median sternotomy have been presented4–10 (Table 1). In one of those, a distal anastomosis was performed via a median sternotomy after removal of Kommerell's diverticulum. In four reports, TAR associated with various kinds of cervical branch bypasses was performed. In one of those with open stent graft, hand-made open stent was used with cervical vessel debranching.4 In the other three, an open stent procedure was used with commercially available devices.8–10 In two of those reports,8,9 the aberrant left subclavian artery was ligated under direct vision, whereas another report noted use of coil embolization for its occlusion. In the present case, we used coil embolization because it was too difficult to dissect the origin of the aberrant artery due to its deep position. Minimal dissection around an aberrant left subclavian artery might reduce the complexity of the operative procedure. We consider that our novel approach makes surgery for this uncommon complex pathology as simple as a conventional total arch replacement procedure.
In conclusion, although choice of the specific type of intervention must be based on patient anatomy and comorbid conditions, our results in the present case show that a total arch replacement with an open stent graft for Kommerell's diverticulum with a right-side aortic arch and aberrant left subclavian artery is a safe and effective option. Furthermore, it allows avoidance of a right thoracotomy and second-stage interventional procedure.
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