Revascularisation of the left subclavian artery for thoracic endovascular aortic repair

Background

The thoracic aorta is the largest blood vessel in the chest. It originates from the heart and supplies blood to the whole body. It can be affected by several diseases, including an aneurysm, which is an enlargement of a weakened section of the aorta, and dissection, which occurs when a tear in the aortic lining causes blood to flow between the layers of the wall of the aorta, forcing the layers apart. The traditional treatment of these conditions is open surgical repair. Thoracic endovascular aortic repair (TEVAR) has evolved as an alternative treatment for a wide variety of aortic diseases. It is less invasive than open surgery, and involves inserting an artificial graft (a tube composed of fabric) into the thoracic aorta through an artery in the groin (the femoral artery), to help reinforce the aortic wall. A significant proportion of patients with thoracic aortic disease have abnormalities close to, or involving the origin of the left subclavian artery (LSA; one of the branches of the thoracic aorta). In these situations, the aortic stent graft needs to be placed close to the LSA, thereby blocking the blood vessel opening. This can potentially result in reduced blood supply to the brain and spinal cord, causing stroke and spinal cord ischaemia (spinal cord stroke). This review aimed to look at the value of a surgical bypass, which can provide an alternative route for blood supply (revascularisation) to the brain and spinal cord in cases of TEVAR, where the LSA is covered.

Controversy exists as to whether routine revascularisation of the LSA, with a surgical bypass, results in improved outcomes in patients undergoing TEVAR, as measured by a reduced risk of stroke and paraplegia (paralysis of the legs). Even though preemptive LSA revascularisation has theoretical advantages, it is not without risks, including nerve damage, bleeding, and graft infection. The Society for Vascular Surgery Practice Guidelines recommend routine revascularisation of the LSA in non-emergency TEVAR, where the LSA origin is covered. However, this recommendation was based on very low-quality evidence.

We undertook a comprehensive, systematic search of the pertinent literature to identify the best available evidence and had planned to synthesise outcome data from randomised controlled trials (RCTs), in order to assist clinicians and patients to make evidence-based decisions.

Study characteristics and key results

We did not identify any RCTs investigating our study question (evidence current until June 2015). The best available evidence comes from non-randomised comparative studies. There is a need for high quality RCTs providing more robust evidence.

Quality of the evidence

It was not possible to evaluate the quality of evidence in the absence of studies eligible for the review.

Authors' conclusions: 

High quality RCT evidence for or against routine or selective revascularisation of the LSA in TEVAR is not currently available. It is not possible to draw conclusions with regard to the optimal management of LSA coverage in TEVAR, and whether routine revascularisation, which was defined as the intervention of interest in our review, confers beneficial effects, as indicated by reduced mortality, cerebrovascular events, and spinal cord ischaemia. This review highlights the need for continued research to provide RCT evidence and define the role of LSA revascularisation in the context of TEVAR with coverage of the LSA.

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Background: 

Controversy exists as to whether revascularisation of the left subclavian artery (LSA) confers improved outcomes in patients undergoing thoracic endovascular aortic repair (TEVAR). Even though preemptive revascularisation of the LSA has theoretical advantages, including a reduced risk of ischaemic damage to vital organs, such as the brain and the spinal cord, it is not without risks. Current practice guidelines recommend routine revascularisation of the LSA in patients undergoing elective TEVAR where achievement of a proximal seal necessitates coverage of the LSA, and in patients who have an anatomy that compromises perfusion to critical organs. However, this recommendation was based on very low-quality evidence.

Objectives: 

To assess the comparative efficacy of routine LSA revascularisation versus either selective or no revascularisation in patients with descending thoracic aortic disease undergoing TEVAR with coverage of the LSA origin.

Search strategy: 

The Cochrane Vascular Trials Search Co-ordinator (TSC) searched the Specialised Register (June 2015). In addition, the TSC searched the Cochrane Register of Studies (CENTRAL (2015, Issue 5)).Trials databases were also searched (June 2015).

Selection criteria: 

We had planned to consider all randomised controlled trials (RCTs) that compared routine revascularisation of the LSA with selective or no revascularisation, in patients undergoing TEVAR.

Data collection and analysis: 

Two review authors independently assessed the title and abstract of articles identified through literature searches. An independent third review author was consulted in the event of disagreement. We had planned for two review authors to independently extract data and assess the risk of bias of identified trials using the criteria recommended in the Cochrane Handbook for Systematic Reviews of Interventions.

Main results: 

We did not identify any RCTs relevant to our review topic. Therefore, no quantitative analysis was conducted.

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