Iatrogenic air embolism: influence of air bubble size on cerebral infarctions in an experimental in vivo and numerical simulation model

BACKGROUND

Cerebral infarctions resulting from iatrogenic air embolism (AE), mainly caused by small air bubbles, are a well-known and often overlooked event in endovascular interventions. Despite their significance, the underlying pathophysiology remains largely unclear.

METHODS

In 24 rats, AEs were induced using a microcatheter, positioned in the carotid artery via femoral access. Rats were divided into two study groups, based on the size of the bubbles (85 and 120 µm) and two sub-groups, differing in air volume (0.39 and 0.64 µl). Ultra-high-field magnetic resonance imaging (MRI) was performed 1.5 hours after intervention. MRI findings including the number, single volume and total volume of the infarctions were assessed. A software-based numerical simulation was performed to qualitatively assess the microvascular pathomechanisms.

RESULTS

In the study groups 22 of 24 rats (92%) revealed cerebral infarctions. The number of infarctions per rat was higher for the smaller bubbles, for the lower (medians: 5 vs 3; p=0.049) and higher air volume sub-groups (medians: 6 vs 4; p=0.012). Correspondingly, total infarction volume was higher for the smaller bubbles (1.67 vs 0.5 mm³; p=0.042). Simulations confirmed the results of the experiments and suggested that fusion of microbubbles to larger bubbles is the underlying pathomechanism of vascular occlusions.

CONCLUSION

In iatrogenic AE, the size of the bubbles can have a major impact on the number and total volume of cerebral infarctions. These findings can help to better understand the pathophysiology of this frequent, often underestimated adverse event in endovascular interventions.

Systematic Review on Customized and Non-customized Device Techniques for the Endovascular Repair of the Aortic Arch

PURPOSE

Open repair remains the standard of care for aortic arch pathologies. However, endovascular management became an attractive alternative for high-risk patients. This study aimed to assess the outcomes of the available endovascular techniques for aortic arch pathology management.

MATERIALS AND METHODS

A search of the English literature (2000-2022) using PubMed, EMBASE, via Ovid, and CENTRAL databases (February 1, 2022) was performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. Studies reporting on patients with aortic arch pathologies managed with custom-made devices ([CMDs] fenestrated or branched thoracic endovascular aortic repair [F/BTEVAR]) and non-CMDs (parallel graft or surgeon-modified FTEVAR) were eligible. Studies reporting on hybrid or open repair were excluded. Studies' quality was assessed using the Newcastle-Ottawa Scale. Primary outcomes were technical success, 30 day mortality, and cerebrovascular events (CVEs). Secondary outcomes were re-intervention and mortality during follow-up.

RESULTS

Thirty studies (2135 patients) were included. Treatment indications were mainly dissections (652 cases [48.0%, 652/1358]; 90 type A, 506 type B; 364 acute, 163 chronic) and aneurysms (46.9%, 582/1239). Five studies (211 patients) reported on FTEVAR and 10 (388 patients) on BTEVAR. For FTEVAR, technical success rate was 98.3%. Thirty-day mortality was 3.8% and CVE rate was 12.3%. Ten deaths (9.7%) and 19 re-interventions (9%) were recorded during follow-up (24 months). Regarding BTEVAR, technical success rate was 98.7%, and 30 day mortality and CVE rates were 5.4% and 11.0%, respectively. During follow-up (27 months), 64 deaths (18.7%) and 33 re-interventions (9.6%) were recorded. Parallel graft technique was reported in 11 studies (901 patients). Technical success rate was 76.4%. Thirty-day mortality was 3.9% and 32 (4.3%) CVEs were recorded. Thirty-five deaths (4.4%) and 43 re-interventions (5.5%) were reported during follow-up (27 months). Surgeon-modified FTEVAR was described in 5 studies (635 patients). Technical success rate was 91.6%. At 30 days, 15 deaths (2.3%) and 22 CVEs (3.5%) were recorded. During follow-up (19 months), 26 deaths (4.2%) and 21 re-interventions (3.6%) were detected.

CONCLUSIONS

Endovascular arch repair presented a variable technical success; >95% for F/BTEVAR; ≤90% for non-CMDs. Acceptable 30 day mortality rates were reported. Cerebrovascular event rates ranged up to 10%. These findings, adjacent to the estimated midterm mortality and re-interventions, set the need for further improvement.

CLINICAL IMPACT

Endovascular arch repair gains popularity as a valuable alternative, especially in patients considered unfit for open repair. According the available literature, any endovascular technique, including custom-made or off-the-shelf solutions, may be applied successfully, with acceptable early mortality. However, the perio-operative cerebrovascular event rate is still an issue, indicating the need for further advancements.

Prospective evaluation of upper extremity access and total transfemoral approach during fenestrated and branched endovascular repair

OBJECTIVE

Total transfemoral (TF) access has been increasingly used during fenestrated-branched endovascular aortic repair (FB-EVAR). However, it is unclear whether the potential decrease in the risk of cerebrovascular events is offset by increased procedural difficulties and other complications. The aim of this study was to compare outcomes of FB-EVAR using a TF vs upper extremity (UE) approach for target artery incorporation.

METHODS

We analyzed the clinical data of consecutive patients enrolled in a prospective, nonrandomized clinical trial in two centers to investigate the use of FB-EVAR for treatment of complex abdominal aortic aneurysms (CAAA) and thoracoabdominal aortic aneurysms (TAAA) between 2013 and 2022. Patients were classified into TF or UE access group with a subset analysis of patients treated using designs with directional branches. End points were technical success, procedural metrics, 30-day cerebrovascular events defined as stroke or transient ischemic attack, and any major adverse events (MAEs).

RESULTS

There were 541 patients (70% males; mean age, 74 ± 8 years) treated by FB-EVAR with 2107 renal-mesenteric TAs incorporated. TF was used in175 patients (32%) and UE in 366 patients (68%) including 146 (83%) TF and 314 (86%) UE access patients who had four or more TAs incorporated. The use of a TF approach increased from 8% between 2013 and 2017 to 31% between 2018 and 2020 and 96% between 2021 and 2022. Compared with UE access patients, TF access patients were more likely to have CAAAs (37% vs 24%; P = .002) as opposed to TAAAs. Technical success rate was 96% in both groups (P = .96). The use of the TF approach was associated with reduced fluoroscopy time and procedural time (each P < .05). The 30-day mortality rate was 0.6% for TF and 1.4% for UE (P = .67). There was no early cerebrovascular event in the TF group, but the incidence was 2.7% for UE patients (P = .035). The incidence of MAEs was also lower in the TF group (9% vs 18%; P = .006). Among 237 patients treated using devices with directional branches, there were no significant differences in outcomes except for a reduced procedural time for TF compared with UE access patients (P < .001).

CONCLUSIONS

TF access was associated with a decreased incidence of early cerebrovascular events and MAEs compared with UE access for target artery incorporation. Procedural time was decreased in TF access patients irrespective of the type of stent graft design.

Utilizing a long sheath to minimize atheroma manipulation (minimal manipulation approach) during Zone 1 and 2 thoracic endovascular aortic repair with a shaggy aorta

We have adopted a simple and reproducible approach, "minimal manipulation approach," since January 2021 in five patients to minimize the risk of thromboembolic events during Zone 1 and 2 thoracic endovascular aortic repair (TEVARs) with shaggy aorta. The approach consists of two parts: ① Use of a 65-cm-long sheath (dry seal) to deliver the endografts without touching the protruding atheroma. Covering the atheroma with the first endograft delivered at Zone 3 to the mid-descending aorta (paving the aorta), and second endograft insertion and deployment through the paved aorta with first endograft. ② Protection of the left subclavian artery using balloon catheter during TEVAR. No in-hospital mortality was recorded, and none of the patients had stroke, spinal cord ischemia, or distal embolic events.

Open Versus Zone 0/1 Endovascular Aortic Repair for Arch Aneurysm: A Propensity Score-Matched Study from the National Clinical Database in Japan

BACKGROUND

Although open surgical repair (OSR) is the gold standard for treating arch aneurysms, thoracic endovascular aortic repair (TEVAR) may be a less invasive alternative. However, it remains unclear which of the 2 methods yields better outcomes. In this study, we compared the perioperative outcomes of both procedures for arch aneurysms using a nationwide surgical database.

METHODS

Data of patients who underwent elective aortic repair for true arch aneurysms were extracted from the National Clinical Database of Japan. Patients who underwent OSR and Zone 0/1 TEVAR were matched in a 1:1 ratio using propensity scores and their mortality and morbidity rates were compared.

RESULTS

A total of 2,815 and 1,125 patients underwent OSR and Zone 0/1 TEVAR, respectively. After propensity score matching, 1,058 patients were included in both groups. Compared with OSR, Zone 0/1 TEVAR was associated with a significantly higher incidence of stroke (5.8 vs. 10.0%, P < 0.001) and paraplegia/paraparesis (1.6 vs. 4.4%, P < 0.001). However, there were no significant differences in the 30-day and operative mortality rates between the 2 groups (2.2 vs. 2.7% and 4.5 vs. 5.4%, respectively). In the Zone 0/1 TEVAR group, postoperative computed tomography was performed in 92.4% of patients, and types I and III endoleaks were identified in 6.4% and 1.1% of patients, respectively.

CONCLUSIONS

Zone 0/1 TEVAR has higher incidences of stroke and paraplegia/paraparesis than OSR, with a risk of postoperative endoleaks. Resolving these problems is the key for expanding the application of Zone 0/1 TEVAR and in the meantime OSR remains the gold standard for surgically fit patients.

Iatrogenic Air Embolisms During Endovascular Interventions: Impact of Origin and Number of Air Bubbles on Cerebral Infarctions

PURPOSE

Cerebral infarctions caused by air embolisms (AE) are a feared risk in endovascular procedures; however, the relevance and pathophysiology of these AEs is still largely unclear. The objective of this study was to investigate the impact of the origin (aorta, carotid artery or right atrium) and number of air bubbles on cerebral infarctions in an experimental in vivo model.

METHODS

In 20 rats 1200 or 2000 highly calibrated micro air bubbles (MAB) with a size of 85 µm were injected at the aortic valve (group Ao), into the common carotid artery (group CA) or into the right atrium (group RA) using a microcatheter via a transfemoral access, resembling endovascular interventions in humans. Magnetic resonance imaging (MRI) using a 9.4T system was performed 1 h after MAB injection followed by finalization.

RESULTS

The number (5.5 vs. 5.5 median) and embolic patterns of infarctions did not significantly differ between groups Ao and CA. The number of infarctions were significantly higher comparing 2000 and 1200 injected MABs (6 vs. 4.5; p < 0.001). The infarctions were significantly larger for group CA (median infarction volume: 0.41 mm3 vs. 0.19 mm3; p < 0.001). In group RA and in the control group no infarctions were detected. Histopathological analyses showed early signs of ischemic stroke.

CONCLUSION

Iatrogenic AEs originating at the ascending aorta cause a similar number and pattern of cerebral infarctions compared to those with origin at the carotid artery. These findings underline the relevance and potential risk of AE occurring during endovascular interventions at the aortic valve and ascending aorta.

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.

Avoiding Stroke in Patients Undergoing Endovascular Aortic Arch Repair: JACC Review Topic of the Week

As the bottleneck of endovascular aortic arch repair, early postoperative stroke remains a devastating complication in high-risk patients and a critical concern for the development of optimal endovascular techniques and devices. The incidence of early postoperative stroke varies widely among currently available endovascular techniques and devices, with reported rates ranging from 0.0% to 42.9%, and is significantly influenced by the severity of the patient's preexisting aortic atherosclerotic burden, air released from the endovascular device, and a variety of factors leading to cerebral perfusion insufficiency. Currently, preidentification of high-risk patients and careful perioperative management appear to play a critical role in reducing stroke incidence. Specific intraoperative prevention methods are still lacking, but embolic protection devices and carbon dioxide or high-volume saline flushing of endovascular devices appear promising. Detailed preoperative stroke risk stratification and screening for optimal endovascular techniques and devices for aortic arch treatment are unmet clinical needs.

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.

Evaluation and Management of Complications of Endovascular Aneurysm Repair of the Thoracic Aorta

Thoracic endovascular aortic repair (TEVAR) has become the standard of care for descending thoracic aortic pathology as the procedure has a historically low rate of reintervention and a high rate of success. However, TEVAR can be associated with complications such as endoleak, upper extremity limb ischemia, cerebrovascular ischemia, spinal cord ischemia, and post-implantation syndrome. An 80-year-old man with a history of complex thoracic aortic aneurysms underwent repair of a large thoracic aneurysm with a frozen elephant trunk procedure in 2019 at an outside institution. The proximal aortic graft extended to the arch and the innominate and left carotid artery were implanted into the distal portion of the graft. The endograft, extending from the proximal graft to the descending thoracic aorta, was fenestrated to maintain left subclavian artery flow. In an attempt to gain a seal at the fenestration, a Viabahn graft (Gore, Flagstaff, AZ, USA) was inserted. A type III endoleak was identified postoperatively at the fenestration, and a second Viabahn graft was required to gain a seal during the initial hospitalization. In 2020, an endoleak persisted at the fenestration on follow-up imaging, but the aneurysmal sac was stable. No intervention was recommended. The patient later presented to our institution with three days of chest pain. A type III endoleak at the level of the subclavian fenestration persisted with significant enlargement of the aneurysm sac. The patient underwent an urgent repair of the endoleak. This consisted of covering the fenestration with an endograft and left carotid to subclavian bypass. Subsequently, the patient developed a transient ischemic attack (TIA) due to kinking and extrinsic compression by the large aneurysm sac of the proximal left common carotid artery, requiring a right carotid to left carotid-axillary graft bypass. This report with a literature review discusses TEVAR complications and outlines methods to approach them. TEVAR complications and their management should be firmly understood to improve overall treatment outcomes.

Technical tips and clinical experience with the Terumo Relay®Branch aortic endovascular graft

Advances in thoracic endovascular aortic repair (TEVAR) are enabling the treatment of increasingly proximal pathology. While the practice of vascular surgery has thus far been mostly limited to TEVAR in zone 2 or more distally, there are emerging devices for zone 1 and zone 0 repair that do not require any further arch debranching compared with a zone 2 repair. Moreover, such devices set forth repair options for patients unable to tolerate the insult of open surgery. One zone 0 device under evaluation is the Terumo Relay^®Branch (Terumo, Tokyo, Japan) endovascular graft, which is an off-the-shelf device based on the Relay^®Pro platform (Terumo). This double branch device uniquely features a large gate, facilitating easy cannulation that contains two locking portal stents for the innominate artery (IA) and left common carotid artery (LCCA) branch grafts. Within our institution, we have had excellent technical success with Relay^®Branch (Terumo) device deployments as part of the Early Feasibility Study, and other centers outside of the USA have published results with this device in small patient series. Notably, there is still a concerning stroke rate associated with the Relay^®Branch (Terumo) device, with permanent stroke rates higher than expected but similar to those for open repair. Thus, these interventions must be undertaken with careful patient selection, thorough planning, and with the guidance of a proficient endovascular aortic team. In this article, we will outline the necessary preoperative workup, highlight device features, and detail the operative strategy, with tips for technical success. These guidelines from our experience will help facilitate successful utilization of this device when it becomes widely available in practice.

Three-year follow-up of aortic arch endovascular stent grafting with the Nexus device: results from a prospective multicentre study

OBJECTIVES

Endovascular aortic arch stent grafting with branched devices has shown initial promising results. The aim of this prospective, multicentre study was to evaluate 3-year outcomes of aortic arch stent grafting with NEXUS® Aortic Arch Stent Graft System (Nexus), a single-branch, bi-modular, off-the-shelf aortic arch stent graft system in high-risk patients.

METHODS

Patients treated with Nexus, either under the feasibility clinical study or as compassionate use procedures in 5 centres, were included in this study. The primary end point was overall survival. The secondary end points included the incidence of procedure-related unplanned intervention, stroke, paraplegia and endoleak. Clinical and radiologic follow-up was performed at each study site at 30 days, 6 months and on a yearly basis thereafter up to 3 years postoperatively.

RESULTS

We analysed data from a total of 28 patients. The overall median follow-up was 1132 (interquartile range: 809-1537). There were no device or procedure-related deaths between 1 and 3 years. Overall survival at 1 and 3 years was 89% and 71%, respectively. The cumulative incidence of unplanned reintervention at 1 and 3 years was 11% and 29%, respectively. There were no reports of stroke, paraplegia, aneurysm rupture, myocardial infarction or new aortic valve insufficiency. In this study's 1-3 year follow-up period, 1 type Ib (4%), 1 type II (4%) and 2 type III (8%; between Nexus' distal end and Thoracic endovascular aortic repair (TEVAR) extensions) endoleak were detected.

CONCLUSIONS

Endovascular aortic arch exclusion with the single-branch, off-the-shelf Nexus system provides promising clinical and radiologic results at 3-year follow-up in a high-risk patient cohort.

Thoracic Endovascular Aortic Repair with Supra-Aortic Trunk Revascularization is Associated with Increased Risk of Periprocedural Ischemic Stroke

BACKGROUND

Ischemic stroke is a devastating complication of thoracic endovascular aortic repair (TEVAR). This risk may be higher in more proximal aneurysms that require arch manipulation. The purpose of this study is to (1) describe 30-day stroke and death rates in patients undergoing TEVAR, (2) compare stroke rates in patients undergoing TEVAR for arch versus descending aneurysm pathology, and (3) identify predictive factors associated with stroke after TEVAR.

METHODS

The Vascular Quality Initiative registry was queried (2015-2021) for TEVAR procedures performed for degenerative aneurysms. Our primary outcomes were any stroke or death at 30 days. Patient-, procedure-, and hospital-level predictors of stroke were assessed using multivariable Poisson regression.

RESULTS

Among 3,072 patients with degenerative aneurysms (197 [6.4%] arch versus 2,875 [93.6%] descending) treated with elective TEVAR, the median age was 73 years (interquartile range 67-79) and 54.8% were male. Within the arch aneurysm group, there were 27.4% zone 0, 22.8% zone 1, and 49.8% zone 2 interventions. Overall 30-day stroke and death rates were 3.2% and 3.8%. The distribution of stroke events was bilateral (52.9%), left carotid (20.7%), left vertebrobasilar (11.5%), right carotid (9.2%), and right vertebrobasilar (5.7%). Although mortality was similar between groups, the rate of ischemic stroke was higher for patients undergoing TEVAR for arch aneurysm versus descending aneurysms (7.1% arch versus 2.9% descending, P = 0.001). Factors that were associated with ischemic stroke after TEVAR included age (>79 years, relative risk [RR] 1.79, 95% confidence interval [CI] 1.08-2.98 vs. <79 years), dependent functional status (RR 1.73, 95% CI 1.07-2.78), procedural time (RR 1.25, 95% CI 1.15-1.36), and endovascular intervention for supra-aortic trunk revascularization (RR 2.66, 95% CI 1.06-6.70 versus no intervention).

CONCLUSIONS

Ischemic stroke risk after TEVAR was increased for arch aneurysms compared to descending aneurysms. More proximal zone coverage and endovascular interventions on the supra-aortic trunks were associated with increasing risk for stroke. Adequate preparation for stroke prevention is necessary prior to TEVAR with supra-aortic trunk revascularization.

Cytokine changes in cerebrospinal fluid following vascular surgery on the thoracic aorta

There is growing evidence that surgery can drive an inflammatory response in the brain. However, the mechanisms behind this response are incompletely understood. Here, we investigate the hypotheses that 1. Cerebrospinal fluid (CSF) cytokines increase after vascular surgery and 2. That these changes in CSF cytokines are interrelated. Patients undergoing either open or endovascular elective surgery of the thoracic aorta were invited to participate in this study. Cerebrospinal fluid samples were taken before surgery and on the first post-operative day. These were analysed for the presence of ten cytokines by immunoassay to examine for post-operative changes in cytokine levels. After surgery, there were significant increases in six out of the ten measured CSF cytokines (IL-1β, 2, 6, 8, 10 and 13). This included changes in both putative pro-inflammatory (IL-1β, 6 and 8) and putative anti-inflammatory (IL-2, 10 and 13) cytokines. The greatest increases occurred in IL-6 and IL-8, which showed a 63-fold and a 31-fold increase respectively. There was strong intercorrelation between CSF cytokines after the operation. Following surgery on the thoracic aorta, there was a marked increase in CSF cytokines, consistent with a potential role in neuroinflammation. The ten measured cytokines showed intercorrelation after the operation, indicating that a balance between multiple pro- and anti-inflammatory cytokines may be present.

Comparison of two surgical approaches for acute type A aortic dissection: hybrid debranching versus total arch replacement

Background

The goal of this study was to determine the clinical outcomes of total arch replacement with frozen elephant trunk surgery and hybrid debranching surgery for acute type A aortic dissection patients.

Methods

From January 2017 to December 2019, the clinical data of acute type A aortic dissection patients were retrospectively collected and analyzed. There were 142 patients underwent total arch replacement with frozen elephant trunk surgery and 35 patients underwent hybrid debranching surgery.

Result

The age, the body mass index and the renal insufficiency of patients in the hybrid group were higher than those in the total arch replacement (TAR) group (all P < 0.01). The operation time, the cardiopulmonary bypass time and the aortic occlusion time of patients in the TAR group were significantly longer than those in the hybrid group (all P < 0.01). Patients in the debranching group had shorter ventilator-assisted breathing time, shorter postoperative hospital stay time and shorter intensive care unit (ICU) stay time. The incidence of pulmonary infection and transient neurological dysfunction were lower, and the transfusions of red blood cells and plasma during the perioperative period were smaller. The survival rates at 2 years were 91.9% and 85.9% in the TAR and hybrid groups, respectively.

Conclusion

Hybrid debranching operation is a safe and effective method for acute type A aortic dissection. Compared with TAR surgery, hybrid debranching surgery has the characteristics of less trauma, rapid recovery and lower incidence of complication.

Midterm Outcomes of an Adjustable Puncture Device for In Situ Fenestration During Thoracic Endovascular Aortic Repair

OBJECTIVE

To evaluate the midterm outcomes of in situ fenestration (ISF) with an adjustable puncture device for aortic arch branch preservation during thoracic endovascular aortic repair (TEVAR).

METHODS

From October 2016 to April 2019, patients with complicated type B aortic dissection, thoracic aortic aneurysm > 5.5 cm in diameter, or aortic penetrating ulcer with a base > 20 mm or depth > 15 mm, who received TEVAR requiring a proximal sealing beyond zone 3 and underwent ISF using an adjustable puncture device, were included. After the procedure, patients were monitored at one, three, six, and 12 months, and annually thereafter. Peri-operative and follow up data were collected and analysed.

RESULTS

Fifty of 51 patients (98%) received successful ISFs. One, two, or three aortic arch branches were preserved in 44, six, and one patient, respectively. Intra-operatively, eight type Ia endoleaks and one type II endoleak were found on angiography. One patient died of cerebral hernia three days post-procedure from a severe stroke; one patient suffered from transient paraplegia but recovered in two weeks; one patient had a non-disabling stroke. The median follow up was 31 months (22.5 - 36.5 months). At six month follow up, all nine unmanaged endoleaks had disappeared. One new type Ia endoleak was identified in a patient at the one month follow up which resolved spontaneously one year later. All revascularised arteries were patent at the last follow up. No fractures, migrations, or bridging stent kinks were found.

CONCLUSION

In this largest mechanical based ISF study to date, an adjustable puncture device was shown to facilitate the procedure of ISF during endovascular repair of aortic diseases involving the aortic arch, with high success. The midterm outcome demonstrates the efficacy and safety of the device in assisting with preservation of aortic arch branches.

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.

Cerebral Emboli Monitoring Using Transcranial Doppler Ultrasonography in Adults and Children: A Review of the Current Technology and Clinical Applications in the Perioperative and Intensive Care Setting

Transcranial Doppler (TCD) ultrasonography is the only noninvasive bedside technology for the detection and monitoring of cerebral embolism. TCD may identify patients at risk of acute and chronic neurologic injury from gaseous or solid emboli. Importantly, a window of opportunity for intervention-to eliminate the source of the emboli and thereby prevent subsequent development of a clinical or subclinical stroke-may be identified using TCD. In this review, we discuss the application of TCD sonography in the perioperative and intensive care setting in adults and children known to be at increased risk of cerebral embolism. The major challenge for evaluation of emboli, especially in children, is the need to establish the ground truth and define true emboli identified by TCD. This requires the development and validation of a predictive TCD emboli monitoring technique so that appropriately designed clinical studies intended to identify specific modifiable factors and develop potential strategies to reduce pathologic cerebral embolic burden can be performed.

Cerebral Ischemia after Stenting of Coarctation of the Aorta

Percutaneous stenting angioplasty of native coarctation of the aorta is considered a low-risk procedure with high success rate. The incidence of cerebral complications, especially ischemic complications, is very low. We report a case of a 15-year-old boy who underwent a percutaneous stenting angioplasty for a coarctation of the aorta and developed a cerebral infraction 4 hours after the procedure.

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.

Stroke rate after thoracic endovascular aortic repair using de-airing of stentgrafts with high-volume of saline solution

Background: Our aim was to determine the rate of ischemic stroke following thoracic endovascular aortic repair (TEVAR) after reducing gas volume released during stentgraft deployment by de-airing of thoracic stentgrafts with high-volume of 0.9% heparinized saline solution. Patients and methods: A single center retrospective analysis of all consecutive patients undergoing TEVAR from 2014 to 2019 was performed. All thoracic stentgrafts were flushed with 120 ml 0.9% heparinized saline solution before implantation, according to our institutional protocol. Endpoints were in-hospital rates of ischemic stroke and spinal cord ischemia (SCI), and all-cause mortality. Results: One hundred and fifty-four patients (mean age: 66.8 ± 13.6 years, 64.9% males) were treated with TEVAR during the study period. Indications for treatment were thoracic aortic aneurysms (n = 75, 48.7%), acute type B aortic dissections (n = 46, 29.9%), aortic arch aneurysms and penetrating aortic ulcers (n = 28, 18.2%), and blunt traumatic aortic injuries (n = 5, 3.2%). Timing of procedure was urgent in 75 patients (48.7%). Proximal landing zone were zone 0-1-2 (n = 75, 48.7%), zone 3 (n = 66, 42.9%) and zone 4 (n = 13, 8.4%). Supra-aortic vessels were revascularized with custom-made fenestrated stentgrafts in 9 patients (5.8%), using chimney technique in 4 patients (2.6%), and with debranching procedures in 19 patients (12.3%). Left subclavian artery was covered without revascularization in 46 patients (29.9%). In-hospital stroke occurred in two patients (1.3%) and SCI in another two patients (1.3%). In-hospital mortality rate was 0.6%. No further in-hospital events were noted. Conclusions: De-airing of stentgrafts with high-volume of 0.9% heparinized saline solution seems to be safe and can be used as an adjunct to keep occurrence of neurological events after TEVAR as low as possible.

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.

Primary Stroke and Failure-to-Rescue Following Thoracic Endovascular Aortic Aneurysm Repair

OBJECTIVE

To characterize the impact, on failure to rescue, of cerebrovascular accident as a first postoperative complication after thoracic endovascular aortic aneurysm repair (TEVAR).

DESIGN

A retrospective cohort study using of National Surgical Quality Improvement Program Participants User File.

SETTING

United States hospitals taking part in the National Surgical Quality Improvement Program.

PARTICIPANTS

Patients >18 years, who underwent TEVAR for nonruptured thoracic aortic aneurysm between 2005 and 2018, and developed one or more major postoperative complications within 30 days after surgery.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Out of 3,937 patients who underwent TEVAR for nonruptured thoracic aneurysm, 1,256 (31.9%) developed major postoperative complications (stroke incidence: 11.4% [143/1256]). In adults <65 years old, the occurrence of stroke as the primary complication, relative to the occurrence of other complications, was associated with ten times greater risk of failure to rescue (29.4% v 4.6%; odds ratio [OR]: 10.10; 95% confidence interval [CI] 2.45-41.56; p < 0.001). The effect size was relatively lower when stroke occurred but was not the primary complication (20.0% v 4.6%; OR: 7.55; 95% CI 1.37-41.71; p = 0.020). In patients ≥65 years, the occurrence of stroke as the primary complication did not carry the similar prognostic value.

CONCLUSION

Younger patients who developed stroke were up to ten times more likely to die, relative to patients who developed other major complications. Survival was substantially reduced when stroke was the primary complication. The authors' findings imply that to maximize the survival of patients undergoing TEVAR, efforts may be needed to predict and prevent stroke occurrence as a primary postoperative morbidity event.

Comparison of Cerebral Embolic Events Between Right and Left Upper Extremity Access During Fenestrated/Branched Endovascular Aortic Repair

Purpose:

To evaluate the incidence and outcomes of cerebral embolic events when using right (RUE) vs left upper extremity (LUE) access for fenestrated/branched endovascular aneurysm repair (f/bEVAR).

Materials and Methods:

A retrospective review was conducted of 290 consecutive patients enrolled in a physician-sponsored Investigational Device Exemption study to evaluate f/bEVAR between 2013 and 2018. Of these, 270 patients (93%) had an upper extremity access with 12-F sheaths, including 205 patients (mean age 75±8 years; 147 men) with LUE and 65 patients (mean age 73±8 years; 42 men) with RUE access. Outcome measures were technical success, procedural metrics, major adverse events (MAEs), any stroke or transient ischemic attack (TIA), and mortality.

Results:

Technical success was higher (p=0.04) for LUE (99.6%) vs RUE access (98.4%). Patients treated via RUE access more often had extent I-III thoracoabdominal aortic aneurysms (57% vs 39%, p=0.03). Procedural metrics were similar for LUE vs RUE sides, including endovascular time (255±80 vs 246±83 minutes, respectively; p=0.23), fluoroscopy time (84±32 vs 90±35 minutes, respectively; p=0.80), and contrast volume (156±57 vs 153±56 mL, respectively; p=0.82). Total radiation exposure was significantly higher for LUE vs RUE access (2463±1912 vs 1757±1494 mGy, respectively; p=0.02). There were 2 deaths (1%) at 30 days or during hospital admission, both unrelated to access site complications. MAEs occurred in 32% of patients who had LUE and 26% of those who had RUE access (p=0.44). Five patients (2%) had embolic stroke and none had TIA. Embolic strokes were ipsilateral to the access side in 4 patients and affected the posterior circulation in 3. Two patients (1%) had hemorrhagic strokes. The incidence of stroke was 3% for LUE and 2% for RUE access (p>0.99).

Conclusion:

Fenestrated/branched stent-graft repair was associated with low rates of cerebral embolic events and no significant difference between the right vs left upper extremity approach.

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.

Use of a Dual-Filter Cerebral Embolic Protection Device in Thoracic Endovascular Aortic Repair

BACKGROUND

The risk of periprocedural stroke after thoracic endovascular aortic repair (TEVAR) ranges from 3% to 8%. Although cerebral embolic protection devices (CEPD) are widely utilized in transcatheter aortic valve replacement, there are currently no Food and Drug Administration approved CEPDs for use in TEVAR. We report our initial experience with the off-label use of a dual-filter CEPD in patients undergoing TEVAR.

METHODS

Two patients at high risk for embolic stroke underwent TEVAR for descending thoracic aortic aneurysms (DTAAs) at a single institution. A dual-filter CEPD (Sentinel; Boston Scientific, Marlborough, MA) was used in an off-label fashion in both cases. Patient 1 was a 62-year-old woman with a 6.2-cm DTAA, extending from the left subclavian artery (LSCA) to the diaphragm (Zones 3-5) and associated with extensive atherosclerotic disease of the aortic arch. Patient 2 was a 78-year-old woman with a 6.3-cm DTAA, extending from the LSCA (Zone 2) to the sixth intercostal space (Zone 4) with associated mural thrombus. Given the proximity of the aneurysm to the LSCA, a left carotid-subclavian bypass was performed for planned LSCA coverage.

RESULTS

Through a percutaneous right radial artery approach using a 6F sheath, the Sentinel dual-filter CEPD was delivered over a 0.014″ guidewire into the thoracic aorta. Under fluoroscopic guidance, the 2 filters were sequentially deployed in the innominate and left common carotid arteries, respectively. Appropriately sized devices were successfully delivered and deployed in the proximal and distal landing zones, respectively. Two devices were used for each patient. Completion angiograms showed successful exclusion of the DTAAs in both cases, without evidence of endoleak. The CEPD filters were retrieved in standard fashion without difficulty. Pathology demonstrated successful capture of embolic debris and fibrin clot in both patients. Neither patient exhibited neurological deficits or device-related complications. Both patients remained neurologically intact at 1- and 2-month follow-up, respectively. Surveillance angiograms revealed successful exclusion of the aneurysm without any evidence of endoleak.

CONCLUSIONS

We report the novel off-label use of a dual-filter CEPD in 2 patients undergoing TEVAR. Pathological confirmation of embolic debris in the filters makes this a potential tool for stroke prevention during TEVAR in high-risk patients.

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.

Engaging patients and caregivers in establishing research priorities for aortic dissection

Objectives:

The aim of this study was to establish the top 10 research uncertainties in aortic dissection together with the patient organization Aortic Dissection Association Scandinavia using the James Lind Alliance concept.

Methods:

A pilot survey aiming to identify uncertainties sent to 12 patients was found to have high content validity (scale content validity index = 0.91). An online version of the survey was thereafter sent to 30 patients in Aortic Dissection Association Scandinavia and 45 caregivers in the field of aortic dissection. Research uncertainties of aortic dissection were gathered, collated and processed.

Results:

Together with research priorities retrieved from five different current guidelines, 94 uncertainties were expressed. A shortlist of 24 uncertainties remained after processing for the final workshop. After the priority-setting process, using facilitated group format technique, the ranked final top 10 research uncertainties included diagnostic tests for aortic dissection; patient information and care continuity; quality of life; endovascular and medical treatment; surgical complications; rehabilitation; psychological consequences; self-care; and how to improve prognosis.

Conclusion:

These ranked top 10 important research priorities may be used to justify specific research in aortic dissection and to inform healthcare research funding decisions.

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.