Is it safe to cover the left subclavian artery when placing an endovascular stent in the descending thoracic aorta?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether the left subclavian artery may be safely covered with a descending thoracic aortic stent without a prior carotid-subclavian artery bypass or transposition procedure. Altogether 2612 abstracts were identified. Forty-five non-randomized control trials and 213 non-controlled papers were found using the reported search and all these were read in full to search for coverage of the left subclavian artery. From these papers, 20 represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. We identified 20 studies with more than 10 cases of left subclavian artery coverage without prior revascularisation. Aggregating the data from all these studies we found 498 covered left subclavian arteries. Complications included 13 strokes (2.6%), 8 cases of paraplegia or paraparesis (1.6%) and 6 endoleaks due to subclavian backflow (1.2%). Of note there were 51 cases of ischaemia or other symptoms attributable to poor blood flow (10%), which resulted in 20 post-procedural revascularisations (4%). In three studies the mean pressure drop in the left arm was between 36 and 48 mmHg after left subclavian occlusion. We conclude that coverage of the left subclavian artery has a low, but not insignificant, incidence of side-effects. This incidence must be balanced with the urgency of the procedure and may be acceptable in emergency or salvage situations. However, in non-emergency cases we recommend that the carotid arteries, the vertebral arteries and the Circle of Willis are fully assessed by tests such as duplex ultrasound, angiography, CT or MRI scanning. An absent right vertebral artery, diseased carotid arteries or an incomplete Circle of Willis is a contraindication to left subclavian artery coverage without prior transposition or bypass grafting of the left subclavian artery.