Stent-graft coverage of the left subclavian artery (LSA) is often performed during TEVAR treatment of thoracic aortic pathologies and, consequently, debranching of the LSA is frequently performed in such settings. The carotid-subclavian bypass (CSB) is undoubtedly the cervical bypass option preferred by most surgeons for this purpose.1,2 The technique was first described by Lyons and Galbraith in 1957,3 and popularized by Diethrich et al. who reported their large experience in a well-known article published 10 years later.4 In the ensuing decades, CSB became the overwhelming favorite of surgeons everywhere performing LSA revascularization for management of arterial occlusive disease and, more recently, in the context of zone-2 TEVAR. Well- documented good results would seem to justify such preference,5 but some level of concern has been voiced consistently over the years about some technical complexities and potential complications such as phrenic nerve and thoracic duct injuries.6 My own personal experience substantiated these reservations early on, prompting adoption of an alternative operative solution with use of the carotid-axillary bypass (CAB),7 an operation first reported by Shumacker in 1973.8 In my hands, it has produced equivalent results to the carotid-subclavian technique in terms of efficacy and durability, and with the additional appeal of distinct practical advantages – mainly because the axillary artery tends to be an easier vessel to expose and handle, and through the avoidance of complications resulting from damage to anatomical structures that are often in harm’s way when exposing the LSA.
Technical aspects
Courtesy of Dr. Criado
Figure 3: Left carotid-axillary bypass performed as a preliminary staged procedure 3 days prior to undertaking zone-2 TEVAR for repair of an extensive descending TAA.
We have essentially used the same basic technique since first adopting CAB in the mid 1980s.7 Unlike the single-incision CSB, targeting the axillary artery as the recipient vessel necessitates 2 incisions, one in the neck inferiorly and parallel to the anterior border of the sternocleidomastoid muscle, and an infraclavicular incision for surgical exposure of the axillary artery (Fig. 1). Most vascular surgeons are quite familiar with the latter because of experience with axillo-femoral bypass. Vessel exposure involves splitting the fibers of the pectoralis major muscle, and division of the pectoralis minor, which (I believe) facilitates these maneuvers. A ringed PTFE vascular graft remains the preferred conduit, carefully tunneled behind the internal jugular vein, and immediately under the clavicle. This operative step does carry a small risk of venous injury. However, I have not found it to be a major problem as the hemorrhage – when it does occur – can be relatively easily controlled by applying firm pressure from above and below the clavicle for a few minutes.
End-to-side anastomoses proximally and distally are constructed in routine manner (Fig. 2). We do not use carotid shunting for this procedure.
Occasionally one may want to combine a carotid endarterectomy with the cervical bypass, in which case the proximal vascular graft anastomosis is constructed at the endarterectomy site (Fig. 3). Close attention must be paid to careful length-tailoring the conduit to achieve the desirable gently curving course without undue tension or redundancy.
Proximal ligation of the LSA, often performed during the CSB, cannot be a component of the carotid-axillary operation because of inaccessibility. Some experts look upon this as a disadvantage, but I tend to view such limitation as advantageous because it eliminates the potential for a misplaced ligation distal to the left vertebral artery origin which present-day CTA studies show it to be the case more frequently than previously suspected. If interruption of the LSA is deemed necessary, it is arguably best to use an endovascular (retrograde trans-brachial) approach with precise deployment of a vascular plug device under angiographic guidance (Fig. 4). ■
Dr. Criado is at MedStar Union Memorial Hospital, Baltimore.
References
1. J Endovasc Ther 2002;9(suppl 2):1132-1138.
2. Ann Cardiothorac Surg 2013;2:247-260.
3. Ann Surg 1957;146:487-494.
4. Am J Surg 1967;114:800-808.
5. J Vasc Surg 2008;48:555-560.
6. Ann Vasc Surg 2008;22:70-78.
7. J Vasc Surg 1995;22:717-723.
8. Surg Gynecol Obstet 1973;136:447-8.
9. J Vasc Surg 1999;30:1106-1112.
