Hybrid endovascular treatment of an aberrant right subclavian artery with Kommerell aneurysm

Introduction

Perturbations in the embryologic development of the right subclavian artery and dorsal aorta lead to the anatomic variant of an aberrant right subclavian artery (ARSA) often associated with an aortic outpouching or Kommerell diverticulum (KD).^1–3 The ARSA courses posterior to the esophagus, leading to “dysphagia lusoria.”^4,5 Given historically high rates of aneurysm rupture and mortality, early repair is indicated.^6–8 Since the first repair via thoracotomy (1971), ⁹ advancements in endovascular therapy now offer new therapeutic options. Successful aneurysm exclusion can now be accomplished with thoracic endovascular stent grafting following open carotid-subclavian bypass to maintain flow to the upper extremities, offering decreased mortality and complication rates. ¹⁰ We present a successful repair of a symptomatic (dysphagia, weight loss) ARSA with KD using this hybrid open-endovascular approach.

Case report

Discussion

ARSA was first described in 1735 by Hunauld ¹¹ during necropsy. ARSA can be found in 0.4–1.2%, while an aberrant LSA is 0.05%. ¹ This aberrant anatomy is the result of abnormal regression of the dorsal right fourth aortic arch from which, in addition to the right seventh intersegmental artery, the right subclavian artery normally takes its origin. In this anomaly, the right seventh intersegmental artery forms from the remnant dorsal aortic arch to give rise to the aberrant right subclavian artery. This often develops as an outpouching of the aorta, distal to the LSA, known as a Kommerell diverticulum. The right subclavian artery then crosses midline, behind the esophagus and spine, and only rarely traveling anterior to the trachea and esophagus.^2,3 Due to its location posterior to the esophagus, intermittent dysphagia, termed “dysphagia lusoria”, may occur.^4,5

Most ARSA are found incidentally on imaging, although symptoms may present as “dysphagia lusoria”, shortness of breath or chest pain.^1,12 Austin and Wolfe ⁶ described these as atherosclerotic lesions in 88%, with 25% associated with aneurysms elsewhere. The natural history of KD involves risk of rupture and death, as with other aneurysms, occurring in up to 50% of patients managed conservatively. Current recommendations therefore are to pursue early definitive repair.^6–8

The first surgical repair was described by Campbell et al. ⁹ in 1971 and since then, standard of care has been a thoracotomy for ARSA/ KD repair. More recent case reports describe endovascular stent grafts, with or without hybrid approaches to carotid-subclavian bypass.^7,12,13 A recent review by Yang et al. ¹⁰ looked at a combined series of 39 patients, 24 of whom underwent endovascular repair of an aberrant subclavian artery and/or a KD. Of these 24 patients, 10 were repaired with stent-grafting and distal artery ligation; eight were repaired with distal occlusion devices; two patients had a stent-graft deployed within the ARSA, when not associated with a KD; the remaining four patients had occlusion of the proximal origin with either distal occlusion or ligation. Comparison of patient outcomes demonstrated that thoracic endovascular stent grafting with distal ARSA ligation and reconstruction offered a significant decrease in mortality and higher rate of aneurysm regression than patients with endovascular stent grafting and distal occlusion devices, or stent-grafting within the ARSA. Endoleak and complication rates between these groups were similar, however. When compared to thoracotomy, decreased mortality and complication rates were noted.^6,10,14,15 Although long-term results are lacking, a series by Kopp et al. ¹⁶ demonstrated symptom-free intervals of 82 and 92 months in two patients who had endovascular repair. ¹⁶

During surgical intervention for an ARSA +/− KD, it is imperative to remember that there may be other associated anatomic variants, to avoid inadvertent injury to these structures. These variants may include a non-recurrent right laryngeal nerve, a right-sided thoracic duct, right-sided aortic arch, a bovine arch or take-off of the common carotid arteries from a common origin, a left vertebral artery arising from aortic arch and coarctation of the aorta.^17–19

Despite the promising results of endovascular intervention for ARSA/ KD, these procedures may be limited by small size of access arteries, tortuous aorta and ARSA. Also aortic arch anatomy may prohibit subclavian artery exclusion due to graft coverage of the left carotid artery and inability to avoid endoleak,^110,20,21 which was the indication for left carotid-subclavian bypass in this patient. Most authors advocate performing left carotid-subclavian bypass if vertebrobasilar circulation is insufficient after right carotid subclavian bypass ²² or if it is anticipated that partial or complete coverage of the LSA orifice will be necessary for aneurysm exclusion.^12,16,23,24

Another limitation of thoracic stent grafting for KD exclusion is that it does not allow for ARSA resection, which may lead to persistence of “dysphagia lusoria”. Although this patient presented predominately with dysphagia, a hybrid endovascular approach to aneurysm exclusion was pursued to avoid the complications and mortality associated with thoracotomy and aortic cross-clamping^14,15 given his advanced age and poor nutritional status. If symptoms of dysphagia persisted, open resection of the KD would be considered.

In conclusion, thoracic endovascular stent grafting to exclude the ARSA/KD, with distal ligation of the right subclavian artery and revascularization of the upper extremities, is evolving as the new standard of therapy for patients with ARSA and KD. Careful pre-operative planning is necessary to minimize cerebral-vascular and peripheral complications, and to provide appropriate exclusion of the KD. This case supports the growing literature that demonstrates decreased morbidity and mortality for the hybrid endovascular approach to this complex problem.