Search

Background and Objectives: The cushioning effect of large, healthy arteries reduces pulsatile afterload to the heart, reduces pulsatility in the microvasculature of target organs, and promotes coronary/cerebral perfusion [1]. With age, large arteries become stiffer, which increases both pulse wave velocity (PWV) and pulse pressure (PP). This results in isolated systolic hypertension [2], which is characterized by increased systolic blood pressure (SBP) with normal or low diastolic blood pressure (DBP) leading to left ventricular afterload. This study aims to replicate, experimentally, arterial stiffness of hypertensive patients, and proposes a novel thoracic endograft for restoring the arterial cushioning function. Methods: The experimental setup comprised of two stiff descending aorta silicone replicas (DASR 1&2), pulse duplicator, heated blood mimicking fluid, pressure and flow sensors. An internal annular viscoelastic cushion, referred to as the ‘WaveGraft’, was deployed in DASR2. Firstly, pulsatile flow was directed through DASR1, (stiff vessel only), then it was diverted through DASR2 (vessel including WaveGraft). Results: When compared to the stiff vessel replica (DASR1), the WaveGraft (DASR2) data showed significant reduction in PWV(−60%), SBP(−9%) and PP(−35%), while DBP increased by 10%. An increase in diastolic perfusion by up to 150%, was observed from the recorded data. Conclusion: This work successfully replicated, key features of aortic hemodynamics in hypertension, linked to the increase in arterial stiffness. The WaveGraft concept showed great potential in altering blood pressure, flowrates and PWV, which may become an important clinical tool in the management of isolated systolic hypertension, heart failure, chronic kidney disease and other chronic conditions.

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.

Complex thoraco-abdominal aortic aneurysm (TAAA) patients remain a challenge irrespective of treatment choice. The Streamliner Multilayer Flow Modulator (SMFM) is an alternative modality of treatment and it is conceptually at variance with conventional treatment modes. Preliminary results show that treatment of infra-renal AAA, juxta-renal AAA, Stanford Type B dissection and Crawford Type V by the SMFM device were most successful. Large volumes of more than 450cm 3 in pathologies such as Crawford Type II and Type IV, should be labelled as a contraindication for use of the SMFM. C-reactive protein, haemoglobin, aneurysm volume and maximum diameter all play major roles in successful treatment. The greater the length of the aorta to be covered and the greater the number of stents utilized, the greater the risk of adverse events and mortality. Patient requiring a reintervention with an additional SMFM(s) within 200 days of primary treatment increases mortality. Both length of the pathology and rate of reintervention indicate a severe aortic pathology burden and its aggressive nature. The SMFM harnesses the body's innate physiological processes to modulate the aneurysm, with no risk of critical shuttering or loss of native side branches. The SMFM offers less operative trauma, shorter procedure times and reduced hospital stays. It offers simplicity, consistency and reproducibility in one treatment. However, the SMFM is not a solution for patients living on borrowed time. It is a promising disruptive technology, only in safe hands and must be utilized under strict instructions for use.

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.

Objective/backgroundTo investigate experimentally the arterial wall/device compliance mismatch of four stent-graft devices and a multilayer flow modulator within the supra- and infrarenal locations for the treatment of abdominal aortic aneurysms (AAA).MethodsFive devices (MFM, EndurantII, Excluder, Zenith, and Fortron) were tested under physiological flow conditions within a flow simulator system comprising of a patient-specific thin-walled flexible AAA perfusion model with replicated intraluminal thrombus, supported by the spinal column. Devices were submitted to circumferential force tests and implanted in the perfusion model for circumferential arterial pressure/diameter measurements. Parameters, including radial resistive force, supra-/infrarenal compliance, pulsatile arterial energy loss (PAEL), pulse wave velocity (PWV), and wave reflection coefficient (Γ), were computed to characterise the devices' performance.ResultsThe Zenith and EndurantII devices had the highest radial resistive force (up to 3 N/cm), while the Fortron device had the lowest (0.11 N/cm). Supra- and infrarenal compliance varied between 6.9–5.1 × 10−4/mmHg and 4.8–5.4 × 10−4/mmHg, respectively. Two devices (EndurantII and Excluder) significantly decreased infrarenal compliance by 13–26% (p

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.

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.

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.

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

Background: Our aim was to describe our experience of the multilayer flow modulator (Cardiatis, Isnes, Belgium) used in the treatment of renal artery aneurysms. Case report: A female patient, aged 42 years underwent treatment of a renal artery aneurysm using the multilayer flow modulator. Contrast-enhanced computed tomography revealed a 23.9 mm type III renal artery aneurysm at the bifurcation of the upper and lower pole vessels, with four side branches. Follow up was assessed by postoperative computed tomography scan at 6 and 19 months postoperatively. There were no immediate postoperative complications or mortality. A normal estimated glomerular filtration rate of > 90 ml/min, which was recorded preoperatively, decreased to 77 ml/min on the day of surgery, and returned to > 90 ml/min 1 day postoperatively. The aneurysm initial decreased in size by 23% at 6 months, and by 16% at 19 months. Overall aneurysm shrinkage was 36% (8.6 mm), with all four side-branches remaining patent throughout follow up. Conclusion: The MFM may provide less operative trauma for patients where complex surgical intervention is the only other feasible treatment option. Longer follow-up, a larger sample size, and comparative studies are required to prove the efficacy of this emerging technology.

Abdominal aortic aneurysm (AAA) represents an asymptomatic cardiovascular type of disease, that is diagnosed in elder people over 60 years old. It is characterised by a ballooning of the abdominal aorta, which grows, at different rates in different patients. If left untreated, it will rupture causing severe internal bleeding, which can lead to shock or death [1]. Medical devices such as bifurcated stent grafts (SG) are used for the treatment of this disease. To help improve SG performance, biomedical engineers design benchtop models for testing.

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 cm 3 . 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.

Abdominal Aortic Aneurysms (AAA) is one of the major cardiovascular diseases that can lead to death if left untreated. An AAA is defined as a permanent and irreversible localised dilation of the infrarenal aorta. Aneurysms can result from accidents, arteriosclerosis, and high blood pressure or as a congenital disease. There are currently two surgical treatments for acute AAA, open surgery or minimally invasive repair (also known as the endovascular repair procedure). The objective of both methods is to isolate the aneurysm sac from the systemic blood pressure and flow to minimise the risk of arterial wall rupture [1]. Preliminary results for endovascular procedures have been promising with short-term results comparable with conventional surgical repair. This is especially the case for patients with small and medium sized AAAs. Long-term results are not so encouraging with stent graft migration, endoleaks, material failure and aneurysm rupture all being reported [2]. A well known complication with this endovascular procedure is the late migration of the graft in which most of the migrations are diagnosed after the first 12 months after the procedure. Multi-factors, including iliac bifurcation angle, stent graft size, blood pressure, stent graft wall compliance, iliac branch curvature, and neck length have been reported to influence device migration. The drag force acting on the bifurcated stent grafts (SG) is one of the main reasons for stent graft migration [3].Copyright © 2012 by ASME

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.