Endovascular management of chronic symptomatic aortic dissection with the Streamliner Multilayer Flow Modulator: Twelve-month outcomes from the global registry.

OBJECTIVE: Reported are initial 12-month outcomes of patients with chronic symptomatic aortic dissection managed by the Streamliner Multilayer Flow Modulator (SMFM; Cardiatis, Isnes, Belgium). Primary end points were freedom from rupture- and aortic-related death, and reduction in false lumen index. Secondary end points were patency of great vessels and visceral branches, and freedom of stroke, paraplegia, and renal failure. METHODS: Out of 876 SMFM implanted globally, we have knowledge of 542. To date, 312 patients are maintained in the global registry, of which 38 patients were identified as having an aortic dissection (12.2%). Indications included 35 Stanford type B dissections, two Stanford type A and B dissections, and one mycotic Stanford type B dissection. RESULTS: There were no reported ruptures or aortic-related deaths. All cause survival was 85.3% Twelve-month freedom from neurologic events was 100%, and there were no incidences of end-organ ischemia, paraplegia or renal insult. Morphologic analysis exhibited dissection remodeling by a reduction in longitudinal length of the dissected aorta, and false lumen volume. A statistically significant reduction in false lumen index (P = .016) at 12 months, and a borderline significant increase in true lumen volume (P = .053) confirmed dissection remodeling. CONCLUSIONS: The SMFM is an option in management of complex pan-aortic dissection. Results highlight SMFM implantation leads to dissection stabilization with no further aneurysm progression, and no retrograde type A dissection. Thoracic endovascular aneurysm repair by SMFM ensued in freedom from aortic rupture, neurologic stroke, paraplegia and renal failure. Further analysis of the global registry data will inform long-term outcomes.

Computational fluid analysis of symptomatic chronic type B aortic dissections managed with the Streamliner Multilayer Flow Modulator.

OBJECTIVE: Managing symptomatic chronic type B aortic dissection (SCTBAD) by the Streamliner Multilayer Flow Modulator (SMFM) stent (Cardiatis, Isnes, Belgium) is akin to provisional structural support to induce complete attachment of the dissection flap, but with the ability of aortic remolding. This study investigated the SMFM's capability to enact healing of SCTBAD. METHODS: Clinical data for 12 cases comprising preoperative and postoperative treatment of SCTBAD were obtained from a multicenter database hosted by the Multilayer Flow Modulator Global Registry, Ireland. A biomechanical analysis, by means of computational fluid dynamics modeling, of the hemodynamic effects and branch patency associated with the use of the SMFM was performed for all cases. The mean length of the dissections was 30.23 ± 13.3 cm. There were 30 SMFMs used, which covered 69 aortic branches. RESULTS: At 1-year follow-up, the true lumen volume increased from 175.74 ± 98.83 cm3 to 209.87 ± 128.79 cm3; the false lumen decreased from 135.2 ± 92.03 cm3 to 123.19 ± 110.11 cm3. The false lumen index decreased from 0.29 ± 0.13 (preoperatively) to 0.21 ± 0.15 (postoperatively). The primary SMFM treatment of SCTBAD increased carotid perfusion by 35% ± 21% (P = .0216) and suprarenal perfusion by 78% ± 32% (P = .001). The wall pressure distribution blended along the newly enlarged true lumen, whereas the false lumen wall pressure decreased by 6.23% ± 4.81% for the primary group (cases 1-7) and by 3.84% ± 2.59% for the secondary group (cases 8-12). CONCLUSIONS: SMFM reduces the false lumen wall pressure through flow modulation. It preserves patency of all branches, minimizing the incidence of short-term complications. The SMFM is a valuable option in managing primary SCTBAD, without midterm complications.

A computational assessment of the hemodynamic effects of crossed and non-crossed bifurcated stent-graft devices for the treatment of abdominal aortic aneurysms.

There are several issues attributed with abdominal aortic aneurysm endovascular repair. The positioning of bifurcated stent-grafts (SG) may affect SG hemodynamics. The hemodynamics and geometrical parameters of crossing or non-crossing graft limbs have not being totally accessed. Eight patient-specific SG devices and four pre-operative cases were computationally simulated, assessing the hemodynamic and geometrical effects for crossed (n= 4) and non-crossed (n= 4) configurations. SGs eliminated the occurrence of significant recirculations within the sac prior treatment. Dean's number predicted secondary flow locations with the greatest recirculations occurring at the outlets especially during the deceleration phase. Peak drag force varied from 3.9 to 8.7N, with greatest contribution occurring along the axial and anterior/posterior directions. Average resultant drag force was 20% smaller for the crossed configurations. Maximum drag force orientation varied from 1.4° to 51°. Drag force angle varied from 1° to 5° during one cardiac cycle. 44% to 62% of the resultant force acted along the proximal centerline where SG migration is most likely to occur. The clinician's decision for SG positioning may be a critical parameter, and should be considered prior to surgery. All crossed SG devices had an increased spiral flow effect along the distal legs with reductions in drag forces.

Insights from complex aortic surgery with a Streamliner device for aortic arch repair (STAR).

OBJECTIVE: Aortic arch aneurysms and thoracoabdominal aortic arch aneurysms are technically challenging to manage by established surgical and endovascular methods. The Streamliner Multilayer Flow Modulator device (Cardiatis, Isnes, Brussels, Belgium) offers an unorthodox option for these high-risk cases. The Streamliner device for aortic arch repair (STAR) study investigated complex aneurysm cases managed by the Streamliner Multilayer Flow Modulator device and offers an analytic solution for a clinical dilemma. METHODS: Six cases were included, with a 1-year follow-up, comprising 4 pure arch aneurysms and 2 thoracoabdominal aortic arch aneurysms Crawford type I, from a multicenter database hosted by the Streamliner Multilayer Flow Modulator Global Registry. A total of 50% of cases were performed under instructions for use. All were American Society of Anesthesiology IV and originated from zone 0. All cases were computationally analyzed, which consisted of (1) simulating the treatment on the basis of the postoperative data, (2) repositioning the stents for the failed technical cases, and (3) assessing the effects of overlapping devices on branch patency. RESULTS: Correct device placement induced aneurysm flow streamlining, which reduced the dynamic pressure by 23% to 66%, whereas incorrect placements promoted Failure Mode I with 58% and 16% dynamic pressure increases and aneurysm volume expansion up to 23%. Overlapped devices improved distal perfusion by increasing arch branch outflows from 5% to 24%. The Streamliner Multilayer Flow Modulator device does not benefit a sac volume greater than 400 cm3. CONCLUSIONS: The Streamliner Multilayer Flow Modulator device is a new technology that can manage complex aortic arch aneurysms and thoracoabdominal aortic arch aneurysms with favorable clinical outcomes if it is performed under instructions for use. Careful procedure planning and perioperative virtual stent placement will avoid foreshortening, prevent inadequate stent overlap lengths, and provide insight into the sufficient numbers of required implanted devices.

Endovascular management of renal artery aneurysms using the multilayer flow modulator.

OBJECTIVE: Our aim was to describe our experience of the Multilayer Flow Modulator (MFM, Cardiatis, Isnes, Belgium) used in the treatment of type III renal artery aneurysms (RAA). METHODS: This is a single-centre study. 3 patients (2 men and 1 woman; mean age 59 years; range 41-77 years) underwent treatment of a type III renal artery aneurysm using the MFM. The indications were a 23.9 mm type III RAA at the bifurcation of the upper and lower pole vessels, with 4 side branches; a 42.4 mm type III saccular RAA at the renal hilum; and a 23 mm type III RAA at the origin of the artery, supplying the upper pole. RESULTS: Patients had a mean follow-up of 27 months, and were assessed by perioperative renal function tests, and repeat postoperative CT scan. There were no immediate postoperative complications or mortality. The first patient's aneurysm shrank by 8.6 mm, from 23.9 to 15.3 mm over 19 months, with all 4 side branches remaining patent. The largest aneurysm at 42.4 mm completely thrombosed, while the renal artery remained patent to the kidney. The final patient refused to have any follow-up scans but had no deterioration in renal function below 30 mL/min, and no further symptoms reported. CONCLUSIONS: The MFM is safe and effective in the management of patients with complex renal artery aneurysms. The MFM can be used to treat branched or distal renal artery aneurysms with exclusion of the aneurysm from the circulation, while successfully preserving the flow to the side branches and kidney. Initial results are promising, however, longer follow-up and a larger cohort are required to prove the effectiveness of this emerging technology.

Systematic Review and Patient-Level Meta-analysis of the Streamliner Multilayer Flow Modulator in the Management of Complex Thoracoabdominal Aortic Pathology.

PURPOSE: To examine the safety and short-term efficacy of the Streamliner Multilayer Flow Modulator (SMFM) in the management of patients with complex thoracoabdominal aortic pathology who are unfit for alternative interventions. METHODS: Biomedical databases were systematically searched for articles published between 2008 and 2015 on the SMFM. A patient-level meta-analysis was used to evaluate aneurysm-related survival. Secondary outcomes were all-cause survival, stroke, spinal cord ischemia, renal impairment, and branch vessel patency. Other considerations were the impact of compliance with the instructions for use (IFU) on clinical outcome. Mean values and Kaplan-Meier estimates are presented with the 95% confidence interval (CI). RESULTS: Fifteen articles (3 multicenter cohort studies, 3 observational cohort studies, and 9 case reports) were included, presenting 171 patients (mean age 68.8±12.3 years; 139 men). The mean aneurysm diameter was 6.7±1.6 cm (95% CI 6.4 to 6.9 cm). Technical success reported in 15 studies was 77.2%. Aneurysm-related survival at 1 year was 78.7% (95% CI 71.7% to 84.4%). One-year all-cause survival was 53.7% (95% CI 46.0% to 61.3%). There were no reported cases of spinal cord ischemia, renal insult, or stroke. CONCLUSION: The SMFM can be safely utilized in some patients with complex thoracoabdominal pathologies provided operators adhere to the IFU. The SMFM is a novel technology with no long-term published data on its sustained effectiveness and a lack of comparative studies. Randomized clinical trials, registries, and continued assessment are essential before this flow-modulating technology can be widely disseminated.

The Effects That Cardiac Motion has on Coronary Hemodynamics and Catheter Trackability Forces for the Treatment of Coronary Artery Disease: An In Vitro Assessment.

The coronary arterial tree experiences large displacements due to the contraction and expansion of the cardiac muscle and may influence coronary haemodynamics and stent placement. The accurate measurement of catheter trackability forces within physiological relevant test systems is required for optimum catheter design. The effects of cardiac motion on coronary flowrates, pressure drops, and stent delivery has not been previously experimentally assessed. A cardiac simulator was designed and manufactured which replicates physiological coronary flowrates and cardiac motion within a patient-specific geometry. A motorized delivery system delivered a commercially available coronary stent system and monitored the trackability forces along three phantom patient-specific thin walled compliant coronary vessels supported by a dynamic cardiac phantom model. Pressure drop variation is more sensitive to cardiac motion than outlet flowrates. Maximum pressure drops varied from 7 to 49 mmHg for a stenosis % area reduction of 56 to 90%. There was a strong positive linear correlation of cumulative trackability force with the cumulative curvature. The maximum trackability forces and curvature ranged from 0.24 to 0.87 N and 0.06 to 0.22 mm(-1) respectively for all three vessels. There were maximum and average percentage differences in trackability forces of (23-49%) and (1.9-5.2%) respectively when comparing a static pressure case with the inclusion of pulsatile flow and cardiac motion. Cardiac motion with pulsatile flow significantly altered (p value <0.001) the trackability forces along the delivery pathways with high local percentage variations and pressure drop measurements.

Stent graft performance in the treatment of abdominal aortic aneurysms: the influence of compliance and geometry.

The long-term success of the endovascular procedure for the treatment of Abdominal Aortic Aneurysms (AAAs ) depends on the secure fixation of the proximal end and the geometry of the stent-graft (SG) device. Variations in SG types can affect proximal fixation and SG hemodynamics. Such hemodynamic variations can have a catastrophic effect on the vascular system and may result from a SG/arterial wall compliance mismatch and the sudden decrease in cross-sectional area at the bifurcation, which may result in decreased distal perfusion, increased pressure wave reflection and increased stress at the interface between the stented and non-stented portion of the vessel. To examine this compliance mismatch, a commercial SG device was tested experimentally under a physiological pressure condition in a silicone AAA model based on computed tomography scans. There was a considerable reduction in compliance of 54% and an increase in the pulse wave velocity of 21%, with a significant amount of the forward pressure wave being reflected. To examine the SG geometrical effects, a commercial bifurcated geometry was compared computationally and experimentally with a geometrical taper in the form of a blended section, which provided a smooth transition from the proximal end to both iliac legs. The sudden contraction of commercial SG at the bifurcation region causes flow separation within the iliac legs, which is known to cause SG occlusion and increased proximal pressure. The blended section along the bifurcation region promotes a greater uniformity of the fluid flow field within the distal legs, especially, during the deceleration phase with reduced boundary layer reversal. In order to reduce the foregoing losses, abrupt changes of cross-section should be avoided. Geometrical tapers could lead to improved clinical outcomes for AAA SGs.

Hemodynamic variations due to spiral blood flow through four patient-specific bifurcated stent graft configurations for the treatment of abdominal aortic aneurysms.

Endovascular repair is now a recognised procedure for treating abdominal aortic aneurysms. However, post-operative complications such as stent graft migration and thrombus may still occur. To assess these complications numerically, the correct input boundary conditions, which include the full human aorta with associated branching, should be included. Four patient-specific computed tomography scanned bifurcated stent grafts (SGs) were modelled and attached onto a full human aorta, which included the ascending, aortic arch and descending aortas. Two of the SG geometries had a twisted leg configuration, while the other two had conventional nontwisted leg configurations. Computational fluid dynamics was completed for both geometries and the hemodynamics assessed. The complexity of the flow patterns and secondary flows were influenced by the inclusion of the full human aorta at the SG proximal section. During the decelerating phase significant recirculations occurred along the main body of all SG configurations. The inclusion of the full human aorta did not impact the velocity contours within the distal legs and there was no difference in drag forces with the SG containing the full human aorta and those without. A twisted leg configuration further promoted a spiral flow formation along its distal legs.

In vitro evaluation of the effects of intraluminal thrombus on abdominal aortic aneurysm wall dynamics.

The optimum time to treat abdominal aortic aneurysms (AAAs) still remains an uncertain issue. The decision to intervene does not take in account the effects that wall curvature, intraluminal thrombus (ILT) properties and thickness have on rupture. The role of ILT in aneurysm dynamics and rupture has been controversial. In vitro testing of four silicone AAA models incorporating the ILT and aortic bifurcation was studied under physiological conditions. Pressures (P) and diameters (D) were analysed for models with and without ILT at different locations. The diametral strain, compliance and P/D curves were influenced by the presence, elastic stiffness and thickness of the ILT. In this case, the inclusion of ILT reduced the lumen area by 77% that resulted in a 0.5-81% reduction in compliance depending on ILT properties. With an increase in ILT stiffness from 0.05 to 0.2 MPa, the compliance was reduced by 81%. In the region of maximum diameter, there was a reduction of diametral strain and compliance except for the softer ILT which was more compliant throughout the proximal region. The shifting of the maximum diametral strain and compliance to the proximal neck was pronounced by an increase in ILT stiffness, thus creating a possible rupture site.