Edel P Kavanagh

How Does the Multilayer Flow Modulator Work? The Science behind the Technical Innovation

The mechanism of action of the Multilayer Flow Modulator (MFM; Cardiatis, Isnes, Belgium) in the treatment of abdominal aortic aneurysm (AAA) still remains elusive to most endovascular specialists. The crosslinks between pressure, wall stress, shear stress, wall displacement, blood flow vortex development, and aneurysm wall dysplasia are concepts that are not commonplace in the clinical vernacular. In the absence of a keen understanding of biomechanics, common practice dictates that one should adhere to a more simplified measure of rupture risk and so maximum aortic diameter remains the parameter most commonly used to determine rupture risk. An arbitrary line of 5.5 cm has been drawn for aortic diameter, beyond which the risk of rupture is such that intervention is required to prevent death. However, experienced clinicians can attest to the fact that the majority of elective aneurysm repairs are in patients whose aortic diameters far exceed the 5.5cm threshold. In fact, aneurysms with diameters more than double the cutoff value remain intact prior to elective repair, while on the other hand, up to 23% of aortic aneurysms have been reported to rupture at diameters below 5 cm. These inconsistencies lead one to believe that a 2-dimensional (2D) marker such as diameter may be too basic a measure and really only of historic relevance. Mounting evidence suggests that an aneurysm growth rate based on 3-dimensional (3D) volume measurements of the AAA and intraluminal thrombus (ILT) is significantly associated with the need for aortic repair, while the same does not hold for growth rates determined by 2D indices of maximum diameter and ILT thickness. Further still, more sophisticated tools, such as finite element (FE) modeling, computational fluid dynamics (CFD), and individualized fluid suture interaction models using 4-dimensional measurements allow for more patient-specific rupture risk analysis. Although these are not common in clinical practice, these biomechanical tools have confirmed the inaccuracy of aneurysm diameter as a predictor of rupture risk. For example, Fillinger et al. demonstrated that peak wall stress is superior to diameter in assessing rupture risk of patient-specific AAAs. These studies used large cohorts to determine statistical significance of their results and concluded that not only is peak wall stress significantly higher in those cases that

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.

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 SMFMs 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.

Kinetics of endothelialization of the multilayer flow modulator and single-layer arterial stents.

The multilayer flow modulator (MFM; Cardiatis, Isnes, Belgium) is a self-expandable mesh of braided cobalt alloy wires, used for treatment of aortic and peripheral aneurysms. To further improve our understanding of this novel technology, the endothelialization kinetics of the MFM was investigated and compared with those of two marketed single-layer stents. Five porcine animal models were used in which a total of 19 stents were implanted in the iliac and carotid arteries between one and five weeks before sacrifice. All 19 stents were successfully delivered. For all devices, nonsignificant signs of inflammation or thrombosis were noted, and there was no evidence of local intolerance. The MFM developed a thin layer of endothelial cells earlier and was associated with less neointimal development than the two single-layer stents. A differing phenomenon of integration was also revealed and hypothesized as endothelialization from adhesion of circulating endothelial progenitor cells, as well as adhesion from the arterial wall, and also by the differences in trauma exposed to the arterial wall.

Assessment of Biocompatibility of the Multilayer Flow Modulator withDiffering Thread Designs

Background: The Multilayer Flow Modulator (MFM) (Cardiatis, Isnes, Belgium) is a self-expandable mesh of cobalt alloy wires used for the treatment of aortic aneurysms. The impact of design thread count and duration of implantation on the biocompatibility of the MFM in porcine animal models was assessed in this study. Methods: Eight mini-piglets received 26 MFM devices (12 with 56 threads, 14 with 80-96 threads) in the iliac, carotid, and renal arteries. Animals were sacrificed and specimens explanted at 1, 3, and 6 months, at which time histological and ultrastructural analyses were carried out. Results: The MFM was successfully deployed in 25 of the 26 implanted cases. The 56 thread devices were well tolerated locally and yielded fewer signs of inflammation and neo intimal hyperplasia. Percentage stenosis was 16.9% ± 5.1% for the 56 thread devices versus 33.4% ± 10.2% for the 80-96 thread devices (p=0.001) at 3 months, and 21.7% ± 9.9% for the 56 thread devices versus 33.6% ± 12.4% for the 80-96 thread devices (p=0.004) at 6 months. The 5 devices selected for SEM examination were well deployed, integrated into the vessel wall and endothelialized, and had patent side branches. Conclusions: No significant stenosis formation or inflammatory response was recorded in any of the implanted animals. The 80-96 thread devices elicited a greater intra-arterial response than the 56 thread devices, although the values for both groups remained within the normal range for stented carotid, renal, or iliac arteries. Further preclinical and clinical studies will extend assessment of the long-term safety and effectiveness of the MFM

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 patients 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.

Long-Term Outcomes of Open Repair of Inflammatory and Atherosclerotic Abdominal Aortic Aneurysms

Background: Abdominal aortic aneurysms (AAA) are a common vascular disease mostly affecting those over the age of 65 years. Open surgical repair (OSR) is considered the gold standard for the treatment of AAA, however longterm mortality and morbidity still remain high in patients with inflammatory AAA, when compared to atherosclerotic AAA. The aim of this study was to evaluate long-term outcomes of both inflammatory and atherosclerotic AAA after OSR. Methods: Out of 837 aortic interventions, 149 patients were identified as having undergone open surgical repair for AAA between 2003 and 2013. Of the 149 patients, histopathological data was available for 92 patients with open AAA repair. Kaplan-Meier curves were analysed to evaluate probability of survival. Results: Patients with inflammatory AAA were younger (70 years) by an average of 2 years compared to atherosclerotic AAA (72 years). Morbidity and length of intensive care stay were insignificantly different in both groups. Inflammatory AAA were associated with higher all cause survival rate (82%) compared to atherosclerotic AAA (68%) (P=0.008) after ten years. Conclusion: There was no difference in clinical outcomes between both atherosclerotic AAA and inflammatory AAA, which is due to the technique used. IAAA were associated with lower mortality rates and improved all cause survival at ten years post open surgical repair.

Topical Wound Oxygen Versus Conventional Compression Dressings in the Management of Refractory Venous Ulcers

Topical wound oxygen (TWO2) proposes an innovative therapy option in the manage‐ ment of refractory non‐healing venous ulcers (RVU) that aims to accelerate wound healing. TWO2 accelerates epithelialisation. This leads to the development of a higher tensile strength collagen, which lessens scarring and the risk of recurrence. Sixty‐seven limbs with 67 ulcers were managed using TWO2 therapy, and 65 limbs with 65 ulcers were managed using conventional compression dressings (CCD). The proportion of ulcers completely healed by 12 weeks was 76% in patients managed with TWO2, compared to 46% in patients managed with CCD (p < 0.0001). The mean reduction in ulcer surface area at 12 weeks was 96% in the TWO2 therapy group, compared to 61% in patients managed with CCD. The median time to full ulcer healing was 57 days in the TWO2 group, in contrast to 107 days in patients managed with CCD (p < 0.0001). TWO2 patients had a significantly improved Quality‐Adjusted Time Spent Without Symptoms of disease and Toxicity of treatment (Q‐TWiST) compared to CCD patients, denoting an improved outcome (p < 0.0001). TWO2 reduces the time needed for RVU healing and is successful in pain alleviation and MRSA elimination. TWO2 therapy radically degrades recurrence rates. Utilising diffused oxygen raises the capillary partial pressure of oxygen (Po2) levels at the wound site, stimulating epithelialisation, and granulation of new healthy tissue. Taking the social and individual aspects of chronic venous ulceration into account, the use of TWO2 can provide an overwhelmingly improved quality of life for long‐time sufferers of this debilitating disease.

TCT-810 “The Phantom Streamlinear” as a Therapeutic Option in the Management of Total Body Thoraco-abdominal Aortic Pathology[TAAA]. Early Results.

RESULTS A total of 15 studies (3 prospective studies, 3 observational reviews and 9 case reports) were included. The mean age of patients was 68.85years (þ/-12.34 years), mean aneurysm diameter was 6.67cm ( 1.57cm). Technical success reported in 15 studies was 77.2 %. Aneurysm related survival at one year was 78.7% ( 3.92%). One year all-cause survival was 53.7 % ( 3.94%). There were no reported cases of spinal cord ischemia or renal insult.