How to minimize air embolisms during thoracic endovascular aortic repair with Relay Pro?

Investigation of air bubble behaviour after gas embolism events induced in a microfluidic network mimicking microvasculature

Gas embolism is a medical condition that occurs when gas bubbles are present in veins or arteries, decreasing blood flow and potentially reducing oxygen delivery to vital organs, such as the brain. Although usually reported as rare, gas embolism can lead to severe neurological damage or death. However, presently, only limited understanding exists regarding the microscale processes leading to the formation, persistence, movement, and resolution of gas emboli, as modulated by microvasculature geometrical features and blood properties. Because gas embolism is initially a physico-chemical-only process, with biological responses starting later, the opportunity exists to fully study the genesis and evolution of gas emboli using in vitro microfluidic networks mimicking small regions of microvasculature. The microfluidics networks used in this study, which aim to mimic microvasculature geometry, comprise linear channels with T-, or Y-junction air inlets, with 20, 40, and 60 μm widths (arterial or venous), and a 30 μm width honeycombed network (arterial) with three bifurcation angles (30°, 60°, and 90°). Synthetic blood, equivalent to 46% haematocrit concentrations, and water were used to study the modulation of gas embolism-like events by liquid viscosity. Our study shows that (i) longer bubbles with lower velocity occur in narrower channels, e.g., with 20 μm width; (ii) the resistance of air bubbles to the flow increases with the higher haematocrit concentration; and lastly (iii) the propensity of gas embolism-like events in honeycomb architectures increases for more acute, e.g., 30°, bifurcation angles. A dimensionless analysis using Euler, Weber, and capillary numbers demarcated the conditions conducive to gas embolism. This work suggests that in vitro experimentation using microfluidic devices with microvascular tissue-like structures could assist medical guidelines and management in preventing and mitigating the effects of gas embolism.

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].

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.

Hemodynamic effects of stent-graft introducer sheath during thoracic endovascular aortic repair

Thoracic endovascular aortic repair (TEVAR) has become the standard treatment of a variety of aortic pathologies. The objective of this study is to evaluate the hemodynamic effects of stent-graft introducer sheath during TEVAR. Three idealized representative diseased aortas were designed: aortic aneurysm, coarctation of the aorta, and aortic dissection. Computational fluid dynamics studies were performed in the above idealized aortic geometries. An introducer sheath routinely used in the clinic was virtually placed into diseased aortas. Comparative analysis was carried out to evaluate the hemodynamic effects of the introducer sheath. Results show that the blood flow to the supra-aortic branches would increase above 9% due to the obstruction of the introducer sheath. The region exposed to high endothelial cell activation potential (ECAP) expands in the scenarios of coarctation of the aorta and aortic dissection, which indicates that the probability of thrombus formation may increase during TEVAR. The pressure magnitude in peak systole shows an obvious rise, and a similar phenomenon is not observed in early diastole. The blood viscosity in the aortic arch and descending aorta is remarkably altered by the introducer sheath. The uneven viscosity distribution confirms the necessity of using non-Newtonian models, and high-viscosity region with high ECAP further promotes thrombosis. Our results highlight the hemodynamic effects of stent-graft introducer sheath during TEVAR, which may associate with perioperative complications.

Results of endovascular aortic arch repair using the Relay Branch system

OBJECTIVES

Our goal was to evaluate results of endovascular aortic arch repair using the Relay Branch system.

METHODS

Forty-three patients with thoracic aortic pathology involving the aortic arch have been treated with the Relay Branch system (Terumo Aortic, Sunrise, FL, USA) in 10 centres. We assessed in-hospital mortality, neurological injury, treatment success according to current reporting standards and the need for secondary interventions. In addition, outcome was analysed according to the underlying pathology: non-dissective disease versus residual aortic dissection (RAD) (defined as remaining dissection after previous type A repair, chronic type B aortic dissections).

RESULTS

In-hospital mortality was 9% (0% in patients with RAD). Disabling stroke occurred in 7% (0% in patients with RAD); non-disabling stroke occurred in 19% (7% in patients with RAD). Early type IA and B endoleak formation occurred in 4%. Median follow-up was 16 ± 18 months. During the follow-up period, 23% of the patients died. Aortic-related deaths were low (3% in patients with RAD).

CONCLUSIONS

The results of endovascular aortic arch repair using the Relay Branch system in a selected patient population with regard to technical success are good. In-hospital mortality is acceptable, the number of disabling strokes is low and technical success is high. Non-disabling stroke is a major concern, and every effort has to be taken to reduce this to a minimum. The best outcome is seen in patients with underlying RAD. Finally, more data are needed.

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.

Early results of a low-profile stent-graft for thoracic endovascular aortic repair

PURPOSE

To assess outcomes of a low-profile thoracic stent-graft in the treatment of thoracic aortic pathologies.

METHODS

A retrospective analysis of all consecutive patients with aortic thoracic pathologies treated with the RelayPro device in two university hospitals between October 2018 and July 2019.

RESULTS

23 patients (65% men; mean age 63.4 ± 15 years) were treated. Pathologies included aortic dissections (n = 10), 5 residual type A (22%) and 5 type B (22%), 6 degenerative aortic aneurysms (26%), 4 penetrating aortic ulcers (17%), and aortic erosion, intramural hematoma and aortic rupture (n = 1 and 4% in each case). Two cases (9%) were emergent and two urgent. Proximal landing was achieved in zones 0 (4%), 1 (4%), 2 (43%), and 3 (26%). Five grafts were frozen elephant trunk extensions. Technical success was 100% with accurate device deployment in the intended landing zone of the aortic arch in all 23 patients and with no Ia/III endoleaks and three (13%) type II endoleaks. Apposition was adequate in 96%. Two patients had post-implantation syndromes (one fever, one leukocytosis). Mean follow-up was 11.6 ± 3.7 months (range, 2-16) with no other complications, secondary interventions or conversions to open surgery. There was no 30-day mortality and no aortic-related mortality; all-cause mortality was 4% during follow-up.

CONCLUSION

A 3-4 French reduced profile in the current generation of stent-grafts facilitates TEVAR particularly in patients with smaller vessels access. Early safety and effectiveness outcomes are favorable, even in endpoints such as deployment accuracy and apposition which may be surrogates for longer-term clinical success and durability.

Fenestrated and Scalloped Endovascular Grafts in Zone 0 and Zone 1 for Aortic Arch Disease

BACKGROUND

The aim of this study is to present midterm results of thoracic endovascular aortic repair (TEVAR) using scalloped or fenestrated custom-made endovascular grafts (CMEGs) in aortic arch Zones 0 and 1.

METHODS

A retrospective review of prospectively collected data involving consecutive patients with aortic arch disease treated by scalloped or fenestrated Relay Plus stent grafts (Terumo Aortic, Sunrise, FL) landed in Zones 0 and 1. Patient demographics, operative details, clinical outcomes, and complications were analyzed.

RESULTS

Between February 2014 and February 2020, 14 patients (9 male and 5 female) with a median age of 66 years (range 48-84) underwent scalloped or fenestrated TEVAR to preserve flow to the supra-aortic trunks (SATs). In 6 cases the landing zone was Zone 0 and in 8, Zone 1. Target vessels for the scallops were left common carotid artery in 8 cases (Zone 1) and innominate artery (IA) in 1 (Zone 0). All 5 fenestrations were designed to preserve the IA (Zone 0). Technical success was 100% with no endoleaks on completion angiography. One fatal perioperative stroke (7%) occurred in a patient with a fenestration for the IA and atherosclerotic plaques in the arch. During median follow-up of 37.5 (3-72) months, no other patient died, and all the target vessels and cervical revascularizations remained patent. There was no paraplegia, no retrograde dissection, and no other complication. Two patients (14%) with scallops in Zone 1 developed late endoleak: 1 type Ib at 6 months and 1 type Ia endoleak at 12 months. There were no endoleaks at all in the group of fenestrated endografts (Zone 0).

CONCLUSIONS

When anatomy allows, endovascular treatment using scalloped or fenestrated CMEGs in Zones 0 and 1 is a feasible technique to treat patients with aortic arch disease involving the SATs.