Silent Cerebral Ischemia After Thoracic Endovascular Aortic Repair: A Neuroimaging Study

The impact of increasing saline flush volume to reduce the amount of residual air in the delivery system of aortic prostheses-a randomized controlled trial

Background

Air embolism is a known risk during thoracic endovascular aortic repair (TEVAR) and is associated with an incomplete deairing of the delivery system despite the saline lavage recommended by the instructions for use (IFU). As the delivery systems are identical and residual air remains frequently in the abdominal aortic aneurysm sac, endovascular aortic repair (EVAR) can be used to examine the effectiveness of deairing maneuvers. We aimed to evaluate whether increasing the flush volume can result in a more complete deairing.

Methods

Patients undergoing EVAR were randomly assigned according to flushing volume (Group A, 1× IFU; Group B, 4× IFU). The Terumo Aortic Anaconda and Treo and Cook Zenith Alpha Abdominal stent grafts were randomly implanted in equal distribution (10-10-10). The quantity of air trapped in the aneurysm sac was measured using a pre-discharge computed tomography angiography (CTA). Thirty patients were enrolled and equally distributed between the two groups, with no differences observed in any demographic or anatomical factors.

Results

The presence of air was less frequent in Group A compared to that in Group B [7 (47%) vs. 13 (87%), p = .02], and the air volume was less in Group A compared to that in Group B (103.5 ± 210.4 vs. 175.5 ± 175.0 mm3, p = .04). Additionally, the volume of trapped air was higher with the Anaconda graft type (p = .025).

Discussion

These findings suggest that increased flushing volume is associated with a higher amount of trapped air; thus, following the IFU might be associated with a reduced risk of air embolization. Furthermore, significant differences were identified between devices in terms of the amount of trapped air.

Clinical trial registration

[NCT04909190], [ClinicalTrials.gov].

Neurological event rates and associated risk factors in acute type B aortic dissections treated by thoracic aortic endovascular repair

OBJECTIVES

Thoracic endovascular aortic repair is the method of choice in patients with complicated type B acute aortic dissection. However, thoracic endovascular aortic repair carries a risk of periprocedural neurological events including stroke and spinal cord ischemia. We aimed to look at procedure-related neurological complications within a large cohort of patients with type B acute aortic dissection treated by thoracic endovascular aortic repair.

METHODS

Between 1996 and 2021, the International Registry of Acute Aortic Dissection collected data on 3783 patients with type B acute aortic dissection. For this analysis, 648 patients with type B acute aortic dissection treated by thoracic endovascular aortic repair were included (69.4% male, mean age 62.7 ± 13.4 years). Patients were excluded who presented with a preexisting neurologic deficit or received adjunctive procedures. Demographics, clinical symptoms, and outcomes were analyzed. The primary end point was the periprocedural incidence of neurological events (defined as stroke, spinal cord ischemia, transient neurological deficit, or coma). Predictors for perioperative neurological events and follow-up outcomes were considered as secondary end points.

RESULTS

Periprocedure neurological events were noted in 72 patients (11.1%) and included strokes (n = 29, 4.6%), spinal cord ischemias (n = 21, 3.3%), transient neurological deficits (n = 16, 2.6%), or coma (n = 6, 1.0%). The group with neurological events had a significantly higher in-hospital mortality (20.8% vs 4.3%, P < .001). Patients with neurological events were more likely to be female (40.3% vs 29.3%, P = .077), and aortic rupture was more often cited as an indication for thoracic endovascular aortic repair (38.8% vs 16.5%, P < .001). In patients with neurological events, more stent grafts were used (2 vs 1 stent graft, P = .002). Multivariable logistic regression analysis showed that aortic rupture (odds ratio, 3.12, 95% confidence interval, 1.44-6.78, P = .004) and female sex (odds ratio, 1.984, 95% confidence interval, 1.031-3.817, P = .040) were significantly associated with perioperative neurological events.

CONCLUSIONS

In this highly selected group from dedicated aortic centers, more than 1 in 10 patients with type B acute aortic dissection treated by thoracic endovascular aortic repair had neurological events, in particular women. Further research is needed to identify the causes and presentation of these events after thoracic endovascular aortic repair, especially among women.

Assessment of Thoracic Endovascular Aortic Repair Using Relay Proximal Scallop: Results of a French Prospective Multicentre Study

OBJECTIVE

A proximal scallop design allows aortic arch repair without complex endovascular manipulation in the aortic arch. The aim was to assess the safety and efficacy at one year of the Relay proximal scallop stent graft.

METHODS

A prospective multicentre study evaluated consecutive patients treated with the Relay proximal scallop stent graft in 10 French aortic centres. All consecutive patients eligible for elective thoracic endovascular repair with proximal scallop in the 10 participating centres between January 2015 and July 2018 were included. Primary endpoints were 30 day mortality, stroke, and spinal cord ischaemia (SCI) rates. Outcomes including safety and efficacy, technical and clinical success, all cause death, neurological events, vessel patency, and device specific complications were analysed. Survival and survival without severe complications were estimated using Kaplan-Meier estimates.

RESULTS

Ten aortic centres treated 40 patients for thoracic aortic aneurysm (45%), penetrating atherosclerotic aneurysm (30%), and dissection (25%). Half of the procedures (50%) targeted zone 0 of the aortic arch (zone 0 in 17.5% and zones 0/1 in 32.5%), 37.5% targeted zone 2 (35% zone 2 alone; 2.5% zones 1/2), and 15% targeted zone 1 (12.5% zone 1 alone). Median follow up was one year. Thirty day mortality, stroke, and SCI rates were 10%, 5%, and 0% respectively. Primary technical success was 95%. Type Ia, Ib, and III endoleaks rates were 5.4%, 0%, and 0% respectively at one month. The overall mortality rate at one year was 17.5%. Aneurysm expansion was > 5 mm in one case at one year associated with type Ia endoleak (3%). There was no supra-aortic trunk thrombosis, one (2%) graft kink, and no migration.

CONCLUSION

One year outcomes showed that the Relay proximal scallop stent graft is an acceptable answer to thoracic aortic disease to deal with short proximal landing zones.

Cerebral embolic protection during transcatheter heart interventions

Stroke remains a devastating complication of transcatheter aortic valve replacement (TAVR), with the incidence of clinically apparent stroke seemingly fixed at around 3% despite TAVR's significant evolution during the past decade. Embolic showers of debris (calcium, atheroma, valve material, foreign material) are captured in the majority of patients who have TAVR using a filter-based cerebral embolic protection device (CEPD). Additionally, in systematic brain imaging studies, the majority of patients receiving TAVR exhibit new cerebral lesions. Mechanistic studies have shown reductions in the volume of new cerebral lesions using CEPDs, yet the first randomised trial powered for periprocedural stroke within 72 hours of a transfemoral TAVR failed to meet its primary endpoint of showing superiority of the SENTINEL CEPD. The present review summarises the clinicopathological rationale for the development of CEPDs, the evidence behind these devices to date and the emerging recognition of cerebral embolisation in many non-TAVR transcatheter procedures. Given the uniqueness of each of the various CEPDs under development, specific trials tailored to their designs will need to be undertaken to broaden the CEPD field, in addition to evaluating the role of CEPD in non-TAVR transcatheter heart interventions. Importantly, the cost-effectiveness of these devices will require assessment to broaden the adoption of CEPDs globally.

Carbon dioxide flushing versus saline flushing of thoracic aortic stents (INTERCEPTevar): protocol for a multicentre pilot randomised controlled trial

INTRODUCTION

Thoracic endovascular aortic repair (TEVAR) carries a 3%-6.1% stroke risk, including risk of 'silent' cerebral infarction (SCI). Stent-grafts are manufactured in room air and retain air. Instructions for use recommend saline flushing to 'de-air' the system prior to insertion, but substantial amounts of air are released when deploying them, potentially leading to downstream neuronal injury and SCI. Carbon dioxide (CO2) is more dense and more soluble in blood than air, without risk of bubble formation, so could be used in addition to saline to de-air stents. This pilot trial aims to assess the feasibility of a full-scale randomised controlled trial (RCT) investigating the neuroprotective benefit against SCI with the use of CO2-flushed aortic stent-grafts.

METHODS AND ANALYSIS

This is a multicentre pilot RCT, which is taking place in vascular centres in the UK, USA and New Zealand. Patients identified for TEVAR will be enrolled after informed written consent. 120 participants will be randomised (1:1) to TEVAR-CO2 or TEVAR-saline, stratified according to TEVAR landing zone. Participants will undergo preoperative neurocognitive tests and quality of life assessments, which will be repeated at 6 weeks, or first outpatient appointment, and 6 months. Inpatient neurological testing will be performed within 48 hours of return to level 1 care for clinical stroke or delirium. Diffusion-weighted MRI will be undertaken within 72 hours postoperatively (1-7 days) and at 6 months to look for evidence and persistence of SCI. Feasibility will be assessed via measures of recruitment and retention, informing the design of a full-scale trial.

ETHICS AND DISSEMINATION

The study coordination centre has obtained approval from the London Fulham Research Ethics Committee (19/LO/0836) and Southern Health and Disability Ethics Committee (NZ) and UK's Health Regulator Authority (HRA). The study has received ethical approval for recruitment in the UK (Fulham REC, 19/LO/0836), New Zealand (21/STH/192) and the USA (IRB 019-264, Ref 378630). Consent for entering into the study will be taken using standardised consent forms by the local study team, led by a local PI. The results of the trial will be submitted for publication in an open access journal.

TRIAL REGISTRATION NUMBER

NCT03886675.

Investigation of Experimental Endovascular Air Embolisms Using a New Model for the Generation and Detection of Highly Calibrated Micro Air Bubbles

BACKGROUND

Air embolism (AE), especially when affecting the brain, is an underrated and potentially life-threatening complication in various endovascular interventions. This study aims to investigate experimental AEs using a new model to generate micro air bubbles (MAB), to assess the impact of a catheter on these MAB, and to demonstrate the applicability of this model in vivo.

MATERIALS AND METHODS

Micro air bubbles were created using a system based on microfluidic channels. The MAB were detected and analyzed automatically. Micro air bubbles, with a target size of 85 µm, were generated and injected through a microcatheter. The MAB diameters proximal and distal to the catheter were assessed and compared. In a subsequent in vivo application, 2000 MAB were injected into the aorta (at the aortic valve) and into the common carotid artery (CCA) of a rat, respectively, using a microcatheter, resembling AE occurring during cardiovascular interventions.

RESULTS

Micro air bubbles with a highly calibrated size could be successfully generated (median: 85.5 µm, SD 1.9 µm). After passage of the microcatheter, the MAB were similar in diameter (median: 86.6 µm) but at a lower number (60.1% of the injected MAB) and a substantially higher scattering of diameters (SD 29.6 µm). In vivo injection of MAB into the aorta resulted in cerebral microinfarctions in both hemispheres, whereas injection into the CCA caused exclusively ipsilateral microinfarctions.

CONCLUSION

Using this new AE model, MAB can be generated precisely and reproducibly, resulting in cerebral microinfarctions. This model is feasible for further studies on the pathophysiology and prevention of AE in cardiovascular procedures.

A New Era of Diagnosis and Therapy in Acute Aortic Syndromes: The Mainz-Essen Experience (Part II)-Management and Outcomes

Over the years, the cardiovascular department of Johannes Gutenberg University in Mainz-West-German Heart Centre in Essen (Germany) designed and implemented the hybrid operating room (2003) along with advanced endovascular and surgical procedures, including the frozen elephant trunk technique. For the study purpose, the Mainz-Essen experience on acute aortic syndromes was summarized by considering original articles from single-center or multicenter studies performed at West German Heart Centre, Essen, Germany, or at the cardiovascular department of Johannes Gutenberg University, Mainz, Germany. We present the 35-year-long Mainz-Essen research, education, and patient management journey in creating an integrated multidisciplinary "Aortic Center" in the heart of Europe.

Cerebral microbleeds following thoracic endovascular aortic repair

BACKGROUND

Stroke and neurological injury are a complication of thoracic endovascular aortic repair (TEVAR). Cerebral microbleeds (CMBs) are common in patients with white matter damage to the brain secondary to chronic vasculopathy. The aim of this study was to examine the occurrence of CMBs after TEVAR, and to evaluate their association with patient and procedural factors.

METHODS

Patients who underwent TEVAR between September 2018 and January 2020 in two specialist European aortic centres were analysed. All patients underwent postoperative susceptibility-weighted MRI. The location and number of CMBs were identified, and analysed with regard to procedural aspects, clinical outcome, and Fazekas score as an indicator of pre-existing vascular leucoencephalopathy.

RESULTS

Some 91 patients were included in the study. A total of 1531 CMBs were detected in 58 of 91 patients (64 per cent). In the majority of affected patients, CMBs were found bilaterally (79 per cent). Unilateral CMBs in the right or left hemisphere occurred in 16 and 5 per cent of patients respectively (P < 0.001). More CMBs were found in the middle cerebral than in the vertebrobasilar/posterior and anterior cerebral artery territories (mean(s.d.) 3.35(5.56) versus 2.26(4.05) versus 0.97(2.87); P = 0.045). Multivariable analysis showed an increased probability of CMBs after placement of TEVAR stent-grafts with a proximal diameter of at least 40 mm (odds ratio (OR) 6.85, 95 per cent c.i. 1.65 to 41.59; P = 0.007) and in patients with a higher Fazekas score on postoperative T2-weighted MRI (OR 2.62, 1.06 to 7.92; P = 0.037).

CONCLUSION

CMBs on postoperative MRI are common after endovascular repair in the aortic arch. Their occurrence appears to be associated with key aspects of the procedure and pre-existing vascular leucoencephalopathy.

Actual incidence of cerebral infarction after thoracic endovascular aortic repair: a magnetic resonance imaging study

 

OBJECTIVES

The actual incidence of cerebral infarction (CI), including asymptomatic infarction, owing to thoracic endovascular aortic repair (TEVAR) has not been reported in detail. This study was performed to investigate the incidence of post-TEVAR CI by using diffusion-weighted magnetic resonance imaging (DW-MRI) and to determine the risk factors for both symptomatic and asymptomatic CI.

METHODS

We examined 64 patients undergoing TEVAR at our institute between April 2017 and November 2020. Aortic atheroma was graded from 1 to 5 by preoperative computed tomography. Cerebral DW-MRIs were conducted 2 days after the procedure to diagnose postoperative CI.

RESULTS

A total of 44 new foci were detected by post-interventional cerebral DW-MRI in 22 patients (34.4%). Only one patient developed a symptomatic stroke (1.6%), and TEVAR was successfully completed in all cases. Debranching of the aortic arch and left subclavian artery occlusion with a vascular plug was performed in 19 (29.7%) and 12 (18.8%) patients, respectively. The number of patients with proximal landing zones 0–2 was significantly higher in the CI group than in the non-CI group (68.2% vs 11.9%; P < 0.001). The following risk factors were identified for asymptomatic CI: aortic arch debranching (P < 0.001), left subclavian artery occlusion (P = 0.001) and grade 4/5 aortic arch atheroma (P = 0.048).

CONCLUSIONS

Over one-third of the patients examined by cerebral DW-MRI after TEVAR were diagnosed with CI. High-grade atheroma and TEVAR landing in zone 0–2 were found to be positively associated with asymptomatic CI.

Clinical trial registration

02-014.

Narrative review on endovascular techniques for left subclavian artery revascularization during thoracic endovascular aortic repair and risk factors for postoperative stroke

OBJECTIVES

The aim of this study was to present a narrative review on endovascular techniques (ET) for revascularization of the left subclavian artery (LSA) during zone 2 thoracic endovascular aortic repair (TEVAR) and on risk factors for postoperative stroke following TEVAR procedures.

METHODS

Non-systematic search of the literature from the PubMed, Ovid and Scopus databases to identify relevant English-language articles fully published in the period 1 January 2010-1 August 2020.

RESULTS

Current general agreement is that LSA revascularization should be always attempted in the elective setting. Under urgent circumstances, it can be delayed but might be considered during the same session on a case-by-case basis. Three ET are currently available: (i) chimney/snorkels (also known as parallel grafts), (ii) fenestrations or branches and (iii) proximal scallops. The main issue with ET is the potential for increased peri-operative stroke risk owing to increased manipulation within the aortic arch. Also, they are relatively novel and further assessment of their long-term durability is needed. Intra-operative embolism and loss of left vertebral artery perfusion are hypothesized as the main causes of stroke in patients undergoing TEVAR.

CONCLUSIONS

The overall risk of stroke seems higher without LSA revascularization during zone 2 TEVAR. As LSA revascularization might have a direct effect in preventing posterior stroke, it should be routinely performed in elective cases, while a case-by-case evaluation can be made under urgent circumstances. While ET can provide effective options for LSA revascularization during zone 2 TEVAR, they are novel and need further durability assessment. Stroke after TEVAR is a multifactorial pathological process and preventing TEVAR-related cerebral injury remains a significant unmet clinical need.

Silent Brain Infarction After Endovascular Arch Procedures: Preliminary Results from the STEP Registry

OBJECTIVE

Few data exist concerning the rate of silent cerebral ischaemic events following endovascular treatment of the aortic arch. The objective of this work was to quantify these lesions using the STEP registry (NCT04489277).

METHODS

This multicentre retrospective cohort study included consecutive patients treated with an aortic endoprosthesis deployed in Ishimaru zone 0-3 and brain diffusion weighted magnetic resonance imaging (DW-MRI) within seven days following the procedure. DW-MRI was performed to identify the location and number of new silent brain infarctions (SBI). All endografts were carbon dioxide flushed prior to implantation.

RESULTS

The study population included 91 patients (mean age, 69 years; men, 64%) from two academic centres treated between September 2018 and January 2020. The procedure was elective in 71 patients (78%). The treatment was performed for a dissection, degenerative aneurysm, or other aortic disease in 44 (49%), 34 (37%), and 13 (14%) patients, respectively. Endografts were deployed in zone 0, 1, 2 or 3 in 23 (25%), 10 (11%), 47 (52%), and 11 (12%) patients, respectively. Endografts were branched (25%), fenestrated (17%), or tubular (58%). At 30 days, there were no deaths or clinical strokes. On cerebral DW-MRI, a total of 245 SBI were identified in 45 patients (50%). Lesions were in the left hemisphere in 63% of the patients (153/245), predominantly in the middle territory (94/245). Deployment in zone 0-1 (p = .026), placement of a branched or fenestrated endograft (p = .038), a proximal endoprosthesis diameter ≥ 40 mm (p = .038), and an urgent procedure (p = .005) were significantly associated with the presence of SBI on univariable analysis, while urgent procedure was found to be an independent predictor on multivariable analysis (binary logistic regression) (p = .002).

CONCLUSION

SBI following endovascular repair of the aortic arch is frequent, although there were no clinical strokes. Innovative strategies to reduce the risk of embolisation need to be developed.

A randomized trial comparing axillary versus innominate artery cannulation for aortic arch surgery

BACKGROUND

Cerebral protection remains the cornerstone of successful aortic surgery; however, there is no consensus as to the optimal strategy.

OBJECTIVE

To compare the safety and efficacy of innominate to axillary artery cannulation for delivering antegrade cerebral protection during proximal aortic arch surgery.

METHODS

This randomized controlled trial (The Aortic Surgery Cerebral Protection Evaluation CardioLink-3 Trial, ClinicalTrials.gov Identifier: NCT02554032), conducted across 6 Canadian centers between January 2015 and June 2018, allocated 111 individuals to innominate or axillary artery cannulation. The primary safety outcome was neuroprotection per the appearance of new severe ischemic lesions on the postoperative diffusion-weighted-magnetic resonance imaging. The primary efficacy outcome was the difference in total operative time. Secondary outcomes included 30-day all-cause mortality and postoperative stroke.

RESULTS

One hundred two individuals (mean age, 63 ± 11 years) were in the primary safety per-protocol analysis. Baseline characteristics between the groups were similar. New severe ischemic lesions occurred in 19 participants (38.8%) in the axillary versus 18 (34%) in the innominate group (P for noninferiority = .0009). Total operative times were comparable (median, 293 minutes; interquartile range, 222-411 minutes) for axillary versus (298 minutes; interquartile range, 231-368 minutes) for innominate (P for superiority = .47). Stroke/transient ischemic attack occurred in 4 (7.1%) participants in the axillary versus 2 (3.6%) in the innominate group (P = .43). Thirty-day mortality, seizures, delirium, and duration of mechanical ventilation were similar in both groups.

CONCLUSIONS

diffusion-weighted magnetic resonance imaging assessments indicate that antegrade cerebral protection with innominate cannulation is safe and affords similar neuroprotection to axillary cannulation during aortic surgery, although the burden of new neurological lesions is high in both groups.

Brain Protection in the Endo-Management of Proximal Aortic Aneurysms

Neurological brain injury (NBI) remains the most feared complication following thoracic endovascular aortic repair (TEVAR), and can manifest as clinically overt stroke and/or more covert injury, detected only on explicit neuropsychological testing. Microembolic signals (MES) detected on transcranial Doppler (TCD) monitoring of the cerebral arteries during TEVAR and the high prevalence and incidence of new ischaemic infarcts on diffusion-weighted magnetic resonance imaging (DW-MRI) suggests procedure-related solid and gaseous cerebral microembolisation to be an important cause of NBI. Any intervention that can reduce the embolic burden during TEVAR may, therefore, help mitigate the risk of stroke and the covert impact of ischaemic infarcts to the function of the brain. This perspective article provides an understanding of the mechanism of stroke and reviews the available evidence regarding potential neuroprotective strategies that target high-risk procedural steps of TEVAR to reduce periprocedural cerebral embolisation.

Retrospective Comparative Study on Differences in Presence of Gas in the Aneurysm Sac after Endovascular Aortic Aneurysm Repair in Early Postoperative Period between Carbon Dioxide Flushing Technique and Saline Flushing of the Delivery System

BACKGROUND

Presence of gas is a frequent finding on early postoperative computed tomography angiography (CTA) after endovascular aortic aneurysm repair (EVAR) with unclear clinical relevance. The aim of this study is to examine and compare the presence of gas within the aneurysm sac following EVAR on early postoperative CTA after the use of carbon dioxide (CO₂) flushing technique with saline flushing alone.

METHODS

A retrospective analysis of patients undergoing standard, fenestrated EVAR (fEVAR) or branched EVAR (bEVAR) with flushing of the delivery system with CO₂ between January 2016 and August 2018 was undertaken. Data of a previous report using standard saline flushing were included. Patients were classified into 2 main groups: group 1 with saline flushing and group 2 with CO₂ flushing and 3 subgroups according to the type of endograft. The presence, position, and volume of gas in the postoperative CTA (within 10 days) was examined and analyzed in terms of anatomical and procedural risk factors.

RESULTS

Group 1 included 210 patients (mean age 73 ± 8, 84% males), while group 2 included 300 patients (mean age 70 ± 11, 68% males). Presence of gas was more common in group 1 (83, 39% vs. 64, 21%, P = 0.000). Volume of gas was larger in group 1 [0.41 mL (0.01-2.7) vs. 0.2 mL (0.02-1), P = 0.001). In standard EVAR with saline flushing (subgroup 1a), 59 patients (45%) had presence of gas with CO₂ flushing (subgroup 2a); 35 patients (25%) had presence of gas (P = 0.005). The mean gas volume was larger in subgroup 1a compared to 2a (0.40 ± 0.47 vs. 0.15 ± 0.17 mL, P = 0.000). The location of the gas was more frequent in contact with the anterior wall of the aorta in both groups, standard EVAR subgroups and fEVAR subgroups. The presence of gas in group 2 was associated with larger preoperative size of the aortic diameter (P = 0.03) and larger perfused lumen diameter (P = 0.05). The type of the graft was not associated with the presence of gas in the aneurysm sac on postoperative CTA. However, the presence of gas was more frequent in standard EVAR than fEVAR and bEVAR. Endoleak type II was not associated with the presence of gas.

CONCLUSIONS

CO₂ flushing of stent grafts during standard and complex EVAR prior to deployment reduces the frequency and volume of gas on postoperative CTA. This study indicates that the CO₂ flushing technique may effectively exchange trapped air for a less harmful gas in endografts.

Distribution of Air Embolization During TEVAR Depends on Landing Zone: Insights From a Pulsatile Flow Model

Purpose: To analyze the distribution of air bubbles in the supra-aortic vessels during thoracic stent-graft deployment in zones 2 and 3 in an aortic flow model. Materials and Methods: Ten identical, investigational, tubular, thoracic stent-grafts were deployed in a glass aortic flow model with a type I arch: 5 in zone 2 and 5 in zone 3. A pulsatile pump generated a flow of 5 L/min with systolic and diastolic pressures (±5%) of 105 and 70 mm Hg, respectively. The flow rates (±5%) were 300 mL/min in the subclavian arteries, 220 mL/min in the vertebral arteries, and 400 mL/min in the common carotid arteries (CCAs). The total amounts of air released in each supra-aortic branch and in the aorta were recorded. Results: The mean amounts of air measured were 0.82±0.23 mL in the zone-2 group and 0.94±0.28 mL in the zone-3 group (p=0.49). In the zone-2 group compared with zone 3, the amounts of released air were greater in the right subclavian artery (0.07±0.02 vs 0.02±0.02 mL, p<0.01) and right CCA (0.30±0.8 vs 0.18±07 mL, p=0.04). There were no differences between the groups concerning the mean amounts of air measured in the right vertebral and all left-side supra-aortic branches. The amount of air released in the descending aorta was significantly higher in the zone-3 group vs the zone-2 group (0.48±0.12 vs 0.13±0.08 mL, p<0.01). Small bubbles were observed continuously during deployment, whereas large bubbles appeared more commonly during deployment of the proximal stent-graft end and after proximal release of the stent-graft. Conclusion: Air is released into all supra-aortic branches and the descending aorta during deployment of tubular thoracic stent-grafts in zones 2 and 3 in an aortic flow model. Higher amounts of air were observed in right-side supra-aortic branches during deployment in zone 2, whereas significantly greater amounts of air were observed in the descending aorta during deployment in zone 3.

Air Embolism During TEVAR: Liquid Perfluorocarbon Absorbs Carbon Dioxide in a Combined Flushing Technique and Decreases the Amount of Gas Released From Thoracic Stent-Grafts During Deployment in an Experimental Setting

Purpose:To investigate the influence of flushing thoracic stent-grafts with carbon dioxide and perfluorocarbon on the amount of gas released during stent-graft deployment in thoracic endovascular aortic repair (TEVAR). Materials and Methods: Ten TX2 ProForm thoracic stent-grafts were deployed into a water-filled container with a curved plastic pipe and flushed sequentially with carbon dioxide, 20 mL of liquid perfluorocarbon (PFC), and 60 mL of saline. Released gas was measured using a calibrated setup. The volume of released gas was compared with the results of an earlier published reference group, in which identical stent-grafts were flushed with 60 mL saline alone as recommended in the instructions for use. Results: The average amount of gas released in the test group was 0.076 mL, significantly lower (p<0.001) than the mean 0.79 mL of gas released in the reference group. Big bubbles appearing at the tip of the sheath when deployment was started were seen in all grafts of the reference group but in only 2 of the test group stent-grafts. Small bubbles were less frequent in the test group. Conclusion: The amount of gas released from thoracic stent-grafts during deployment can be influenced by different flushing techniques. The use of PFC in addition to the carbon dioxide flushing technique reduces the volume of gas released during deployment of tubular thoracic stent-grafts to a few microliters. This significant effect is presumably based on the high solubility of carbon dioxide in perfluorocarbon and could be a potential future approach to lower the risk of cerebral injury and stroke from air embolism during TEVAR.

Bubble Counter for Measurement of Air Bubbles During Thoracic Stent-Graft Deployment in a Flow Model

BACKGROUND

The aim of our study was to describe and validate the use of a bubble counter in an aortic flow model assessing the distribution of air bubbles in the supra-aortic vessel during thoracic stent-graft deployment.

MATERIALS AND METHODS

In an aortic flow model made by glass, identical tubular thoracic stent grafts (Zenith TX2 ProForm; Cook Medical, Bjaeverskov, Denmark) were deployed distal to the left subclavian artery. Four steps were defined during deployment: (1) introduction of the stent graft in the arch; (2) deployment of the stent graft; (3) proximal release of the stent graft; and (4) retrieval of the introduction system. On both sides, the common carotid and the vertebral artery were connected together, and the air bubbles were measured with one bubble counter probe per side. The number of air bubbles, as well as their size and distribution, is analyzed during these four steps for the left and right sides with a bubble counter.

RESULTS

Ten thoracic stent grafts were included in the study. The total number of air bubbles measured during all steps was significantly higher on the left side (1091 ± 255 versus 545 ± 288, P < 0.00001). During the third step, significantly higher numbers of bubbles were observed on the left side (P = 0.0000001) compared with the right side. The analysis of all bubbles by size revealed that a higher number of bubbles ranged 100-200 μm (P < 0.02) and 200-300 μm (P < 0.03) on the left side. Small bubbles were observed during all steps of deployment, whereas large bubbles appeared more commonly during the second and third steps.

CONCLUSIONS

A significant number of air bubbles are released during deployment of tubular thoracic stent grafts distally of the left subclavian artery in an aortic flow model. The distribution of air bubbles is bilateral with a higher number of air bubbles released on the left side.

Cerebral embolization, silent cerebral infarction and neurocognitive decline after thoracic endovascular aortic repair

Background

Silent cerebral infarction is brain injury detected incidentally on imaging; it can be associated with cognitive decline and future stroke. This study investigated cerebral embolization, silent cerebral infarction and neurocognitive decline following thoracic endovascular aortic repair (TEVAR).

Methods

Patients undergoing elective or emergency TEVAR at Imperial College Healthcare NHS Trust and Guy's and St Thomas' NHS Foundation Trust between January 2012 and April 2015 were recruited. Aortic atheroma graded from 1 (normal) to 5 (mobile atheroma) was evaluated by preoperative CT. Patients underwent intraoperative transcranial Doppler imaging (TCD), preoperative and postoperative cerebral MRI, and neurocognitive assessment.

Results

Fifty-two patients underwent TEVAR. Higher rates of TCD-detected embolization were observed with greater aortic atheroma (median 207 for grade 4–5 versus 100 for grade 1–3; P = 0·042), more proximal landing zones (median 450 for zone 0–1 versus 72 for zone 3–4; P = 0·001), and during stent-graft deployment and contrast injection (P = 0·001). In univariable analysis, left subclavian artery bypass (β coefficient 0·423, s.e. 132·62, P = 0·005), proximal landing zone 0–1 (β coefficient 0·504, s.e. 170·57, P = 0·001) and arch hybrid procedure (β coefficient 0·514, s.e. 182·96, P &lt; 0·001) were predictors of cerebral emboli. Cerebral infarction was detected in 25 of 31 patients (81 per cent) who underwent MRI: 21 (68 per cent) silent and four (13 per cent) clinical strokes. Neurocognitive decline was seen in six of seven domains assessed in 15 patients with silent cerebral infarction, with age a significant predictor of decline.

Conclusion

This study demonstrates a high rate of cerebral embolization and neurocognitive decline affecting patients following TEVAR. Brain injury after TEVAR is more common than previously recognized, with cerebral infarction in more than 80 per cent of patients.

Detection of vulnerable atherosclerotic plaque during thoracic endovascular aortic repair using nonobstructive angioscopy

An angioscope was used to observe the intima of the aorta in an 82-year-old patient who had undergone thoracic endovascular aortic repair. The aortic angioscopic findings showed vulnerable plaques from the ascending aorta to the aortic arch that had not been visualized using preoperative computed tomography. After deploying a stent graft from zone 1 to zone 4, the proximal edge of the stent graft was adjacent to the ruptured plaque with mixed thrombi. In spite of these findings, the patient had an uneventful recovery. Angioscopy may have the potential to stratify the risk of thoracic endovascular aortic repair-related complications.

S-100β and Antioxidant Capacity in Cerebrospinal Fluid during and after Thoracic Endovascular Aortic Repair

Background

Thoracic Endovascular Aortic Repair (TEVAR) has substantially decreased the mortality and major complications from aortic surgery. However, neurological complications such as spinal cord ischemia may still occur after TEVAR. S-100β is a biomarker of central nervous system injury, and oxidant injury plays an important role in neurological injury. In this pilot study, we examined the trends of S-100β and antioxidant capacity in the CSF during and after TEVAR.

Methods

We recruited 10 patients who underwent elective TEVAR. CSF samples were collected through a lumbar catheter at the following time points: before the start of surgery (T0) and immediately (T1) and 24 (T2) and 48 hours (T3) after the deployment of the aortic stent. S-100β and CSF antioxidant capacity were analyzed with the use of commercially available kits.

Results

We observed that the level of S-100β in all of the subjects at 24 hours after the deployment of the aortic stent (T2) increased. However, the levels of S-100β at T1 and T3 were comparable to the baseline value. The antioxidant capacity remained unchanged. No patient had a clinical neurologic complication.

Conclusions

Our observations may indicate biochemical/subclinical central nervous system injury attributable to the deployment of the aortic stent.

Axillary versus innominate artery cannulation for antegrade cerebral perfusion in aortic surgery: design of the Aortic Surgery Cerebral Protection Evaluation (ACE) CardioLink-3 randomised trial

INTRODUCTION

Neurological injury remains the major cause of morbidity and mortality following open aortic arch repair. Systemic hypothermia along with antegrade cerebral perfusion (ACP) is the accepted cerebral protection approach, with axillary artery cannulation being the most common technique used to establish ACP. More recently, innominate artery cannulation has been shown to be a safe and efficacious method for establishing ACP. Inasmuch as there is a lack of high-quality data comparing axillary and innominate artery ACP, we have designed a randomised, multi-centre clinical trial to compare both cerebral perfusion strategies with regards to brain morphological injury using diffusion-weighted MRI (DW-MRI).

METHODS AND ANALYSIS

110 patients undergoing elective aortic surgery with repair of the proximal arch requiring an open distal anastamosis will be randomised to either the innominate artery or the axillary artery cannulation strategy for establishing unilateral ACP during systemic circulatory arrest with moderate levels of hypothermia. The primary safety endpoint of this trial is the proportion of patients with new radiologically significant ischaemic lesions found on postoperative DW-MRI compared with preoperative DW-MRI. The primary efficacy endpoint of this trial is the difference in total operative time between the innominate artery and the axillary artery cannulation group.

ETHICS AND DISSEMINATION

The study protocol and consent forms have been approved by the participating local research ethics boards. Publication of the study results is anticipated in 2018 or 2019. If this study shows that the innominate artery cannulation technique is non-inferior to the axillary artery cannulation technique with regards to brain morphological injury, it will establish the innominate artery cannulation technique as a safe and potentially more efficient method of antegrade cerebral perfusion in aortic surgery.

TRIAL REGISTRATION NUMBER

NCT02554032.

A systematic review of postoperative cognitive decline following open and endovascular aortic aneurysm surgery

OBJECTIVES Postoperative cognitive decline (POCD) is a well-recognised neurological phenomenon following major surgery. Most commonly seen in elderly patients, it has direct links to increased long-term morbidity and reduced quality of life. Its incidence following open and endovascular abdominal and thoracic aneurysm surgery is unclear. The purpose of this systematic review is to collate available evidence for POCD following abdominal and thoracic aortic surgery, and to identify continuing controversies directing future research. METHODS A MEDLINE search was conducted following the recommendations of the PRISMA guidelines. Terms searched for included but were not limited to: aortic surgery, delirium, postoperative cognitive decline/dysfunction thoracic aortic surgery, abdominal aortic surgery. Reference lists were searched for additional studies. RESULTS Five observational studies were identified from the literature search. Variation in study methods, cognitive test batteries and thresholds set by the study coordinators did not allow for pooled results. In those studies that did find evidence of decline, risk was linked to age over 65 years, presence of postoperative delirium and decreased years in education. CONCLUSIONS Evidence thus far suggests that POCD can affect patients following major aortic, non-cardiothoracic as well as cardiothoracic surgery. Future research should focus on using a validated repeatable battery of cognitive tests and a single defined threshold for POCD to allow pooled analysis and more robust conclusions. Larger, adequately powered studies are required to re-evaluate the effect of aortic aneurysm surgery on postoperative cognitive function.

Air bubbles are released by thoracic endograft deployment: An in vitro experimental study

Purpose:

Embolic stroke is a dreaded complication of thoracic endovascular aortic repair. The prevailing theory about its cause is that particulate debris from atherosclerotic lesions in the aortic wall are dislodged by endovascular instruments and embolize to the brain. An alternative source of embolism might be air trapped in the endograft delivery system. The aim of this experimental study was to determine whether air is released during deployment of a thoracic endograft.

Methods:

In an experimental benchtop study, eight thoracic endografts (five Medtronic Valiant Thoracic and three Gore TAG) were deployed in a water-filled transparent container drained from air. Endografts were prepared and deployed according to their instructions for use. Deployment was filmed and the volume of air released was collected and measured in a calibrated syringe.

Results:

Air was released from all the endografts examined. Air volumes ranged from 0.1 to 0.3 mL for Medtronic Valiant Thoracic and from <0.025 to 0.04 mL for Gore TAG. The largest bubbles had a diameter of approximately 3 mm and came from the proximal end of the Medtronic Valiant device.

Conclusion:

Air bubbles are released from thoracic endografts during deployment. Air embolism may be an alternative cause of stroke during thoracic endovascular aortic repair.

Air Embolism During TEVAR

Purpose: To investigate the amount of gas released from Zenith thoracic stent-grafts using standard saline flushing vs the carbon dioxide flushing technique. Methods: In an experimental bench setting, 20 thoracic stent-grafts were separated into 2 groups of 10 endografts. One group of grafts was flushed with 60 mL saline and the other group was flushed with carbon dioxide for 5 minutes followed by 60 mL saline. All grafts were deployed into a water-filled container with a curved plastic pipe; the deployment was recorded and released gas was measured using a calibrated setup. Results: Gas was released from all grafts in both study groups during endograft deployment. The average amount of released gas per graft was significantly lower in the study group with carbon dioxide flushing (0.79 vs 0.51 mL, p=0.005). Conclusion: Thoracic endografts release significant amounts of air during deployment if flushed according to the instructions for use. Application of carbon dioxide for the flushing of thoracic stent-grafts prior to standard saline flush significantly reduces the amount of gas released during deployment. The additional use of carbon dioxide should be considered as a standard flush technique for aortic stent-grafts, especially in those implanted in proximal aortic segments, to reduce the risk of air embolism and stroke.

Multivariate Analysis of Risk Factors of Cerebral Infarction in 439 Patients Undergoing Thoracic Endovascular Aneurysm Repair

The aim of the study is to identify the potential risk factors of cerebral infarction associated with thoracic endovascular aneurysm repair (TEVAR). TEVAR was developed as a less invasive surgical alternative to conventional open repair for thoracic aortic aneurysm treatment. However, outcomes following TEVAR of aortic and distal arch aneurysms remain suboptimal. Cerebral infarction is a major concern during the perioperative period. We included 439 patients who underwent TEVAR of aortic aneurysms at a high-volume teaching hospital between July 2006 and June 2013. Univariate and multivariate logistic regression analyses were performed to identify perioperative cerebral infarction risk factors. Four patients (0.9%) died within 30 days of TEVAR; 17 (3.9%) developed cerebral infarction. In univariate analysis, history of ischemic heart disease and cerebral infarction and concomitant cerebrovascular disease were significantly associated with cerebral infarction. "Shaggy aorta" presence, left subclavian artery coverage, carotid artery debranching, and pull-through wire use were identified as independent risk factors of cerebral infarction. In multivariate analysis, history of ischemic heart disease (odds ratio [OR] 6.49, P = 0.046) and cerebral infarction (OR 43.74, P = 0.031), "shaggy aorta" (OR 30.32, P < 0.001), pull-through wire use during surgery (OR 7.196, P = 0.014), and intraoperative blood loss ≥800 mL (OR 24.31, P = 0.017) were found to be independent risk factors of cerebral infarction. This study identified patient- and procedure-related risk factors of cerebral infarction following TEVAR. These results indicate that patient outcomes could be improved through the identification and management of procedure-related risk factors.

Carbon Dioxide Flushing Technique to Prevent Cerebral Arterial Air Embolism and Stroke During TEVAR

Purpose: To describe the technique of carbon dioxide (CO2) flushing of thoracic stent-grafts to reduce the risk of cerebral air embolism. Technique: To remove room air, thoracic stent-grafts were preoperatively flushed 2 minutes with carbon dioxide from a cylinder connected to the flushing chamber of the captor valves of Zenith custom-made endografts; this was followed by the standard saline flush. Thirty-six patients undergoing thoracic endovascular aortic repairs (TEVAR) involving the ascending aorta and the aortic arch received CO2-flushed Zenith endografts. One patient with a highly calcified arch experienced a minor stroke. Conclusion: Arterial air embolism is a potentially underappreciated problem of aortic endografting, especially in the proximal segments of the aorta. CO2 flushing may have the potential to reduce air embolization during TEVAR.

A Staged Hybrid Procedure to Manage Complex Cerebral Hypoperfusion in Aortic Arch Aneurysm

We report the management of a patient who had an open-surgical repair following traumatic avulsion of the supra-aortic trunks (SAT) 30 years prior to presentation with a large arch aneurysm and poor cerebral collaterals. "Simple" thoracic endovascular aneurysm repair (TEVAR) was not an option because it would have excluded the collateral circulation to the carotid and vertebral arteries. We devised a two-stage hybrid procedure to repair this challenging aneurysm.