Spinal cord protection during TEVAR: primum non nocere Free

Spinal cord ischaemia (SCI), including both paraplegia and paraparesis, remains a devastating complication after thoracic endovascular aortic repair (TEVAR). Both the European [European Association for CardioThoracic Surgery (EACTS), European Societyfor Vascular Surgery (ESVS)] and American [Society for Vascular Surgery (SVS)] cardio-thoracic and vascular surgical societies currently report several factors that have been associated with an increased incidence of SCI after TEVAR [1–4]. These include prior abdominal aortic aneurysm repair (both open surgical and endovascular), extensive aortic stent graft coverage (ESVS: >200 mm, SVS: >150 mm), prolonged hypotension, severe atherosclerosis of the thoracic aorta, occlusion of the left subclavian artery and/or hypogastric arteries, chronic renal failure, or intentional coverage of the coeliac artery (CA). These factors may determine the high-risk of SCI after TEVAR and have led to the recommendation of prophylactic cerebrospinal fluid drainage (CSFD) in high-risk patients, next to other haemodynamical adjuncts to protect the spinal cord.

The indication for prophylactic CSFD in the study by Seike et al. [4] mainly concurred with the factors described in these documents (e.g. extensive aortic coverage >8 thoracic vertebrae, previous downstream aortic repair and shaggy aorta). Moreover, the authors considered coverage of the Adamkiewicz artery as an increased risk for SCI. However, in contrast with the recommendations, a patent CA was covered to obtain an adequate distal landing zone if needed. The authors focused on TEVAR for dTAAs and compared a high-risk cohort that underwent prophylactic CSFD (n = 89) with a ‘normal-risk’ cohort without CSFD (n = 115). Incidence rates of SCI were similar in both groups, both before and after propensity score matching, considering the length of descending aortic and CA coverage as well. The results of SCI in high-risk patients versus ‘normal-risk’ patients were 9.0% vs 4.9% (P = 0.403) in the overall cohort and 5.1% vs 7.3% (P = 0.697) in the matched cohorts. These comparative findings seem to support the selective use of prophylactic CSFD during TEVAR.

Seike et al. [4] concluded: ‘… prophylactic CSFD did not have a significant effect for the prevention of SCI after TEVAR for dTAA’. However, as high-risk patients received CSFD and had a non-statistically significant difference in SCI incidence as compared to the ‘normal-risk’ cohort without CSFD, CSFD may as well have prevented SCI occurrence in the high-risk patients. This is in line with the recommendations for prophylactic CSFD in these patients, based on previous observations [1–3]. Such conclusions could be considered speculative, as CSFD was selectively performed in high-risk patients only, and this aspect may have biased the results. Nevertheless, we agree with the title that an aggressive—or routine—use of CSFD for the prevention of SCI after TEVAR is not supportive and that this should be tailored towards the individual patient at the high risk of SCI occurrence.

Prophylactic CSFD is not without risk and the risk–benefit ratio should therefore be carefully weighed and investigated. CSFD might induce iatrogenic SCI, cause spinal infections, haematomas or catheter fractures or retainment. A randomized controlled trial powered to compare SCI rates and CSFD-related complications after TEVAR, in patients at the high risk of SCI occurrence, might be resolutive in this regard. However, given the available evidence in favour of CSFD in high-risk patients, this may be challenging from an ethical standpoint.

Regarding spinal cord protection during thoracic aortic surgery, important differences between open surgical repair and TEVAR need to be emphasized. Several issues related to open surgical repair such as time of aortic cross-clamping, left heart bypass use and increase of anterior spinal artery pressures by immediately oversewing or occluding back bleeding from spinal arteries after opening the aorta are related to the risk of SCI [1]. During TEVAR, authors have highlighted that coverage of 2 out of 4 inflow sources to the spinal cord (e.g., left subclavian artery coverage and intercostal arteries) is highly relevant with regard to the occurrence of SCI, especially combined with prolonged hypotension, while coverage of a single territory is less relevant [5]. In patients without factors that increase the risk of ‘simple’ TEVAR for dTAAs and that cover only 1 out of the 4 inflow sources, CSFD may thus be guided by close postoperative monitoring and symptom occurrence, in line with the conclusions by Seike et al. [4]. In this study, a patent CA was covered to obtain an adequate landing zone if needed. However, a recent meta-analysis investigated the clinical impact of CA coverage during TEVAR and reported high rates of spinal cord ischaemia (pooled estimate of 95% CI 2–9), suggesting that CA coverage should be avoided during TEVAR, if possible [6].

As mentioned before, several haemodynamical adjuncts to improve spinal cord perfusion need to be adopted first when treating patients with TEVAR. Aiming to achieve stable mean arterial pressures ∼80 mmHg, or even increasing to >90 mmHg in high-risk patients, next to haemoglobin management strategies, or even the admission of steroids or naloxone, depends on local protocols [3, 7]. Another adjunct in branched endovascular thoraco-abdominal aneurysm repairs is temporary aneurysm sac perfusion [8].

Interestingly, the reversibility of SCI has been reported in the literature, owing to the immediate application of haemodynamical adjustments and/or CSFD. In this study, 3 postoperative therapeutic CSFD were reported. In our experience, SCI occurred in limited cases but was usually definitive, despite several haemodynamical adjuncts and optimization. This created caution towards the report of reversible SCI after TEVAR in literature. However, reversibility may depend on the extent and severity of the ischaemic symptoms included in the definition of SCI (e.g., paraplegia, paraparesis) and on the definition of improvement or recovery. Different practices (e.g., clinical evaluation at different time intervals, detection by somatosensory or motoric evoked potentials) may also lead to different perceptions regarding the reversibility of SCI after TEVAR. This further underlines the importance of reporting, analysing and comparing worldwide patient data to further improve strategies aimed at the reduction of adverse outcomes of patients treated with TEVAR.

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