Evidence of use of multilayer flow modulator stents in treatment of thoracoabdominal aortic aneurysms and dissections

Multilayer Stent for Emergency Treatment of Acute Type B Aortic Dissection: A Case Report

PURPOSE

We report the case of an acute type B dissection with high-risk features treated with multilayer stent.

CASE REPORT

A 50-year-old female patient presented to the emergency department with an acute type B aortic dissection. Conservative medical treatment did control blood pressure but did not alleviate her dissection symptoms. She was treated endovascularly with multilayer stents extensively covering the whole dissected area. HThe aortic arch side branches, visceral arteries and renal arteries remained patent after treatment. The recovery was uneventful, and she was discharged the day after the intervention. At 6- and 12-month follow-up, the patient remained asymptomatic, the true lumen volume increased and all side branches remained patent.

CONCLUSION

We present a case of the use of a multilayer stent for acute type B aortic dissection. This technique allows to treat the whole dissection with low risk of paraplegia or side branch occlusion. Long-term results of ongoing clinical studies should confirm the place of the multilayer stent as a treatment option for type B aortic dissection.

Aneurysm Sac Pressure during Branched Endovascular Aneurysm Repair versus Multilayer Flow Modulator Implantation in Patients with Thoracoabdominal Aortic Aneurysm

Open thoracoabdominal repair is the gold standard in the TAAA treatment. However, there are endovascular techniques, that sometimes may be an alternative, such as branched endovascular aneurysm repair (BEVAR) or implantation of the multilayer flow modulator (MFM). In this study, we aimed to assess differences in the aneurysm sac pressure (ASP) between patients undergoing BEVAR and MFM implantation. The study included 22 patients with TAAA (14 patients underwent BEVAR, while eight MFM implantation). The pressure sensor wire was placed inside the aneurysm. A measurement of ASP and aortic pressure (AP) was performed during the procedure. The systolic pressure index (SPI), diastolic pressure index (DPI), and pulse pressure index (PPI) were calculated as a quotient of the ASP and AP values. After the procedure, SPI and PPI were lower in the BEVAR group than in the MFM group. During a procedure, a drop in SPI and PPI was noted in patients undergoing BEVAR, while no changes were revealed in the MFM group. This indicates that BEVAR, but not MFM, is associated with a reduction in systolic and pulse pressure in the aneurysm sac in patients with TAAA.

[Chronic type B aortic dissection-what to do?]

BACKGROUND

Chronic type B aortic dissection requires optimal medical therapy. However, secondary complications like organ or extremity malperfusion or development of aneurysmal dilatation require interventional therapy.

OBJECTIVES

Presentation of different endovascular treatment options for complications of chronic type B aortic dissection.

MATERIALS AND METHODS

Analysis of current literature with regard to indications, techniques, results, and differential indications of interventional techniques for the treatment of chronic type B aortic dissection complications.

RESULTS

Endovascular implantation of an aortic stent graft is interventional standard therapy for treatment of aneurysmal dilatation of the aorta following type B dissection. Technical problems are the proximal and distal landing zones and the treatment of persistent flow in the false lumen.

CONCLUSION

Endovascular treatment of chronic complicated type B aortic dissection is increasingly used compared to open surgical treatment because not only are more complex stent grafts (fenestrated and branched devices) available but also because of newly developed techniques for effective occlusion of flow in the false lumen (e.g., candy plug).

Endovascular treatment of complicated aortic aneurysms using a modified flow-diverting strategy: Mid- to long-term outcome from a multicenter cohort study

OBJECTIVES

Frequently reported adverse events following flow-diverting stents' treatment of aortic aneurysms indicate further refinements of this technique are required. This study aims at evaluating the clinical efficacy of an improved flow-diverting strategy.

METHODS

A modified flow-diverting procedure was utilized in selected patients, in which stent-grafts were used to cover the non-branched segment of the aneurysmal lesion while flow-diverting multilayered bare metal stents were applied to cover the reno-visceral segment. The safety and efficacy of this joint procedure were assessed by regular follow-up.

RESULTS

We screened 497 patients and included 67 cases (mean age: 67.07 ± 12.14 years; 53 males) between February 2012 and March 2018. The median number of stent-grafts and bare metal stents used in the procedure were 1 (range: 1 to 3) and 3 (range: 2 to 4), respectively. During a mean follow-up period of 34.54 ± 20.28 months, aneurysm maximum diameter decreased from 64.79 ± 10.31 to 59.32 ± 10.20 mm (p = 0.002), while sac thrombosis ratio increased from 26.01±10.99% to 98.46±4.84% (p<0.001). Aneurysm-related death or conversion to open repair was documented in three patients. The majority side-branches (198/201) remained patent during follow-up. Overall clinical success rate reached 91.04% (61/67).

CONCLUSIONS

The joint procedure is characterized by significant aneurysm thrombosis along with high aneurysm stabilization/shrinkage and side-branches' patency rate. It might represent a potential improvement of the flow-diverting strategy in treating complex aortic lesions, yet large-scale, prospective, and randomized trials are anticipated to draw a robust conclusion.

ADVANCES IN KNOWLEDGE

The joint procedure could potentially exclude complex aortic aneurysms from circulation while maintaining the collateral branches.

The Technological Advancement to Engineer Next-Generation Stent-Grafts: Design, Material, and Fabrication Techniques

Endovascular treatment of aortic disorders has gained wide acceptance due to reduced physiological burden to the patient compared to open surgery, and ongoing stent-graft evolution has made aortic repair an option for patients with more complex anatomies. To date, commercial stent-grafts are typically developed from established production techniques with simple design structures and limited material ranges. Despite the numerous updated versions of stent-grafts by manufacturers, the reoccurrence of device-related complications raises questions about whether the current manfacturing methods are technically able to eliminate these problems. The technology trend to produce efficient medical devices, including stent-grafts and all similar implants, should eventually change direction to advanced manufacturing techniques. It is expected that through recent advancements, especially the emergence of 4D-printing and smart materials, unprecedented features can be defined for cardiovascular medical implants, like shape change and remote battery-free self-monitoring. 4D-printing technology promises adaptive functionality, a highly desirable feature enabling printed cardiovascular implants to physically transform with time to perform a programmed task. This review provides a thorough assessment of the established technologies for existing stent-grafts and provides technical commentaries on known failure modes. They then discuss the future of advanced technologies and the efforts needed to produce next-generation endovascular implants.

Late surgical conversion of failed Multilayer Flow Modulator stenting in thoraco-abdominal aneurysms

OBJECTIVES

The aim of this study was to report the outcomes of open or hybrid repair of failed thoraco-abdominal aortic aneurysm endovascular treatment with Multilayer Flow Modulator (MFM) stents.

METHODS

All patients who underwent open or hybrid repair of a failed MFM aortic treatment were retrospectively analysed. Perioperative and postoperative data, as well as midterm survival, were assessed.

RESULTS

Between 2013 and 2020, 39 patients received an open or hybrid conversion after endovascular treatment. Five of them [13%; 4 males; median age 68 years (interquartile range 66-76)] were previously treated with aortic MFM stents (Cardiatis, Isnes, Belgium). Among these, the median interval between index repair and conversion was 84 months (interquartile range 75-84). The median aneurysm diameter was 9.6 cm (interquartile range 8-10). Renovisceral vessels steno-occlusion was highly prevalent: 2 renal arteries were occluded; 3 coeliac trunks, 2 renal arteries and 1 superior mesenteric artery had a >70% ostial stenosis. Open standard thoraco-abdominal aneurysm conversion was performed in 3 fit patients, while a hybrid approach with visceral debranching and tube endografting was performed in 2 high-risk patients. Two patients (2 open repairs) died intraoperatively, and 1 (hybrid repair) postoperatively. The 2 successfully treated patients are alive at 4- and 34-month follow-up, respectively, with patent visceral branches.

CONCLUSIONS

Open or hybrid thoraco-abdominal aortic aneurysm treatment after failed endovascular aortic repair with MFM stents might be the only surgical option to address sac enlargements and ruptures or branch-related failures. However, both procedures had a poor prognosis due to both the impaired preoperative patient's status and the surgical complexity in the presented series.

A Case of Multilevel Aortic Disease Treated Using Cardiatis Multilayer Flow Modulator

A recent systematic review and meta-analysis shows that synchronous and metachronous thoracic and abdominal aortic aneurysms are present in 19.2% of cases. The management remains controversial: elective simultaneous TEVAR and EVAR could increase morbidity due to increased aortic coverage during a single procedure, longer operative times, increased blood loss, and greater contrast exposure. Conversely, simultaneous thoracic endovascular aortic repair (TEVAR) and endovascular aneurysms repair (EVAR) prevent the need for two interventions, reduces future access site complications, and obviates interval aortic complications.

We present a case of a multilevel aortic disease treated in three stages: EVAR, TEVAR, and exclusion of an increasing aortic visceral penetrating aortic ulcer through a multilayer flow modulator endograft with an optimal result.

Experimental Analysis of Pressure and Flow Alterations During and After Insertion of a Multilayer Flow Modulator into an AAA Model with Incorporated Branch

PURPOSE

The multilayer flow modulator (MFM) device has been used for the treatment of abdominal aortic aneurysm (AAA) for over a decade. Although several clinical studies have been published, criticism and concern over the device efficacy remain, as no quantitative analysis that describes its mechanism has been performed yet. The aim of this study was to experimentally evaluate the effect of MFM device deployment on aneurysmal pressure and branch perfusion.

MATERIALS AND METHODS

An experimental flow and pressure monitoring system was developed to analyze the MFM deployment procedure performed by a qualified radiologist in AAA geometries with and without side branch. Particle image velocimetry experiments were then conducted on models with and without MFM device to evaluate and compare flow patterns and local flow velocity and vorticity in the aneurysm.

RESULTS

The experiments revealed no significant change in pressure and flow rate during and after deployment of the MFM device. The flow rate of the incorporated branch was fully preserved. On both models, the aneurysmal flow velocity was significantly reduced. In addition, the device modified local flow patterns, reducing vorticity and better feeding the incorporated branch.

CONCLUSION

This experimental study provides the basis for a better understanding of the mechanism of the MFM device, which allows intra-aneurysmal flow to decrease while preserving incorporated branch flow and reducing the risk of type II endoleak. The experimental system developed for this study was effective in simulating an endovascular procedure and studying the safety and effectiveness of endovascular devices.

Multilayer stents affect the final diameter of aortic aneurysms and maintain renal artery patency for a short time in a swine experimental model

OBJECTIVES

We sought to analyze the hemodynamic effects of the multilayer flow-modulated stent (MFMS) in Thoracoabdominal aortic aneurysms (TAAAs).

METHODS

The hemodynamic effects of MFMS were analyzed in aortic thoracoabdominal aneurysms in experimental swine models. We randomly assigned 18 pigs to the stent or control groups and underwent the creation of an artificial bovine pericardium transrenal aneurysm. In the stent group, an MFMS (Cardiatis, Isnes, Belgium) was immediately implanted. After 4 weeks, we evaluated aneurysm sac thrombosis and renal branch patency by angiography, duplex scan, and morphological analysis.

RESULTS

All the renal arteries remained patent after re-evaluation in both groups. Aneurysmal sac thrombosis was absent in the control group, whereas in the stent group it was present in 66.7% of aneurysmal sacs (p=0.061).The mean final aneurysm sac diameter was significantly lower in the stent group (mean estimated reduction, 6.90 mm; p=0.021). The proximal neck diameter decreased significantly in the stent group (mean difference, 2.51 mm; p=0.022) and grew significantly in the control group (mean difference, 3.02 mm; p=0.007). The distal neck diameter increased significantly in the control group (mean difference, 3.24 mm; p=0.017). There were no significant findings regarding distal neck measurements in the stent group.

CONCLUSION

The MFMSs remained patent and did not obstruct the renal arteries within 4 weeks. In the stent group, the device was also associated with a significant decrease in aneurysmal sac diameter and a large proportion (albeit non-significant) of aneurysmal sac thrombosis.

Results of a three-year follow-up after endovascular therapy with multilayer flow modulator in complex thoracoabdominal aortic aneurysm: A case report

OBJECTIVES

Studies on the short-, medium and long-term effects of flow guiding stents are still limited. In this case report, we present three-year follow-up of the multilayer flow modulator stent in a 55-year-old patient with Crawford Type 2 thoracoabdominal aortic aneurysm.

METHODS

A 55-year-old male patient with Crawford Type 2 thoracoabdominal aortic aneurysm had applied to our medical center. The aneurysm involved coeliac truncus and superior mesenteric artery and extended to the renal artery ostia. Multilayer flow modulator stent was successfully placed, and follow-up CT (Computed tomography) angiographic examination images recorded intermittently (36 months).

RESULTS

After three years, it was observed that the left renal artery was thrombosed and the left kidney went to atrophy. Other major vascular branches were observed to be open. During this time, the aneurysm was completely closed with thrombus, but the diameter of the aneurysm continued to increase.

CONCLUSIONS

Multilayer flow modulator stents are safe in complex aortic aneurysms. The device increases the thrombus load in the aortic aneurysm and maintains the flow of the main vascular branches. But re-interventions, dilatation of the aneurysm sac and visceral branch obstructions are still challenging for multilayer flow modulator stents.

Endovascular repair during complex thoracic aortic dissection using a micropore stent graft: Midterm follow-up clinical outcomes

Objective

This study explored the clinical efficacy and hemodynamic effects of the micropore stent graft (MSG) that could promote aortic remodeling and preserve important organ branches.

Methods

We conducted a retrospective analysis of 26 patients who underwent endovascular repair using an MSG for DeBakey types I and III TAD at our center between December 2014 and December 2017. The main efficacy parameters were rupture of the false lumen or dissection‐related death, conversion to open repair, secondary reintervention, branch vessel patency, and the hemodynamic effects of TAD at 12 months.

Results

Dissection rupture, dissection‐related mortality, conversion to open repair, and secondary reintervention rates at 12 months were 0, 3.9, 0, and 0%, respectively. In the 24 patients with more than 6 months of follow‐up, micropore stents were implanted to cover 39 openings in aortic arch branches, 91.7% (22/24) presented with complete thrombosis in the false lumen, 8.3% (2/24) presented with partial thrombosis in the false lumen, 35.2% (6/17) presented with a thrombus in the false lumen that was completely absorbed, and all 39 branches were patent. After surgery, pressure peak value and fluctuation along with the degree and range of unstable blood flow in the aortic lumen decreased.

Conclusions

For type I and type III thoracic artic dissection, endovascular treatment with an MSG may be a safe and effective treatment option with a good midterm outcome.

Hemodynamic Effects of Multiple Overlapping Uncovered Stents on Aortic Dissection: Surgical Strategies and Implications for False Lumen Thrombosis

PURPOSE

Multiple overlapping uncovered stents (MOUS) are employed to promote false lumen thrombosis in the aortic dissections (AD), when the tears are in close vicinity to the branch vessels. However, the overall rate of false lumen thrombosis remains unsatisfactory. This study was performed to investigate the hemodynamic influence of MOUS on aortic dissection to shed some light on the mechanism of post-stenting false lumen thrombosis.

METHODS

An anatomically accurate computational fluid dynamics model was developed to investigate the hemodynamics of AD. A parametric study was carried out to demonstrate the hemodynamic influence of MOUS in various post-surgery scenarios featuring the representative surgical strategies involving MOUS.

RESULTS

The use of reduced-porosity MOUS slowed the blood flow in the false lumen and decreased the wall shear stress. MOUS depressed the false lumen and enlarged the true lumen, without significantly altering the blood outflow distribution among the branch vessels. Compared with MOUS-alone and stent graft-alone scenarios, the combination of MOUS and stent graft generated a substantially large region of stagnant flow. The active flow was confined to an area in close vicinity to the tears covered by the MOUS, which perfuse the right renal artery in the false lumen.

CONCLUSIONS

MOUS helps to generate a favored hemodynamic environment for thrombus formation in the false lumen. Application of MOUS along with covered stent grafts may represent a more effective treatment for AD than utilizing MOUS or stent graft alone.

Multilayer flow modulator enhances vital organ perfusion in patients with type B aortic dissection

Management of aortic dissections (AD) is still challenging, with no universally approved guideline among possible surgical, endovascular, or medical therapies. Approximately 25% of patients with AD suffer postintervention malperfusion syndrome or hemodynamic instability, with the risk of sudden death if left untreated. Part of the issue is that vascular implants may themselves induce flow disturbances that critically impact vital organs. A multilayer mesh construct might obviate the induced flow disturbances, and it is this concept we investigated. We used preintervention and post-multilayer flow modulator implantation (PM) geometries from clinical cases of type B AD. In-house semiautomatic segmentation routines were applied to computed tomography images to reconstruct the lumen. The device was numerically reconstructed and adapted to the PM geometry concentrically fit to the true lumen centerline. We also numerically designed a pseudohealthy case, where the geometry of the aorta was extracted interpolating geometric features of preintervention, postimplantation, and published representative healthy volunteers. Computational fluid dynamics methods were used to study the time-dependent flow patterns, shear stress metrics, and perfusion to vital organs. A three-element Windkessel lumped parameter module was coupled to a finite-volume solver to assign dynamic outlet boundary conditions. Multilayer flow modulator not only significantly reduced false lumen blood flow, eliminated local flow disturbances, and globally regulated wall shear stress distribution but also maintained physiological perfusion to peripheral vital organs. We propose further investigation to focus the management of AD on both modulation of blood flow and restoration of physiologic end-organ perfusion rather than mere restoration of vascular lamina morphology. NEW & NOTEWORTHY The majority of aortic dissection modeling efforts have focused on the maintenance of physiological flow using minimally invasive placed grafts. The multilayer flow modulator is a complex mesh construct of wires, designed to eliminate flow disruptions in the lumen, regulate the physiological wall stresses, and enhance endothelial function and offering the promise of improved perfusion of vital organs. This has never been fully proved or modeled, and these issues we confirmed using a dynamic framework of time-varying arterial waveforms.