CoreValve® transcatheter self-expandable aortic bioprosthesis

Parameterization, algorithmic modeling, and fluid-structure interaction analysis for generative design of transcatheter aortic valves

Heart valves play a critical role in maintaining proper cardiovascular function in the human heart; however, valve diseases can lead to improper valvular function and reduced cardiovascular performance. Depending on the extent and severity of the valvular disease, replacement operations are often required to ensure that the heart continues to operate properly in the cardiac system. Transcatheter aortic valve replacement (TAVR) procedures have recently emerged as a promising alternative to surgical replacement approaches because the percutaneous methods used in these implant operations are significantly less invasive than open heart surgery. Despite the advantages of transcatheter devices, the precise deployment, proper valve sizing, and stable anchoring required to securely place these valves in the aorta remain challenging even in successful TAVR procedures. This work proposes a parametric modeling approach for transcatheter heart valves (THVs) that enables flexible valvular development and sizing to effectively generate existing and novel valve designs. This study showcases two THV configurations that are analyzed using an immersogeometric fluid-structure interaction (IMGA FSI) framework to demonstrate the influence of geometric changes on THV performance. The proposed modeling framework illustrates the impact of these features on THV behavior and indicates the effectiveness of parametric modeling approaches for enhancing THV performance and efficacy in the future.

Transcatheter Aortic Valve Replacement with a Self-Expanding Prosthesis

The self-expanding transcatheter heart valve (Medtronic Cardiovascular Corevalve and Evolut) is a supra-annular, trileafet porcine pericardial valves on a diamond lattice nickel-titanium alloy frame. The TAVR device has undergone significant improvements in design and procedural techniques to further increase safety, efficacy, and durability since they it was first released. Unique design characteristics, as well as patient and procedural factors, favor self-expanding over balloon-expandable prostheses in certain situations. The self-expanding transcatheter heart valve has proven to be an excellent option for severe aortic stenosis patients with any level of surgical risk and preliminary data suggest a comparable durability to surgical tissue valves.

Challenging Anatomies for TAVR-Bicuspid and Beyond

Transcatheter aortic valve replacement has emerged as the standard treatment for the majority of patients with symptomatic aortic stenosis. As transcatheter aortic valve replacement expands to patients across all risk groups, optimal patient selection strategies and device implantation techniques become increasingly important. A significant number of patients referred for transcatheter aortic valve replacement present with challenging anatomies and clinical indications that had been historically considered a contraindication for transcatheter aortic valve replacement. This article aims to highlight and discuss some of the potential obstacles that are encountered in clinical practice with a particular emphasis on bicuspid aortic valve disease.

Immersogeometric fluid-structure interaction modeling and simulation of transcatheter aortic valve replacement

The transcatheter aortic valve replacement (TAVR) has emerged as a minimally invasive alternative to surgical treatments of valvular heart disease. TAVR offers many advantages, however, the safe anchoring of the transcatheter heart valve (THV) in the patients anatomy is key to a successful procedure. In this paper, we develop and apply a novel immersogeometric fluid-structure interaction (FSI) framework for the modeling and simulation of the TAVR procedure to study the anchoring ability of the THV. To account for physiological realism, methods are proposed to model and couple the main components of the system, including the arterial wall, blood flow, valve leaflets, skirt, and frame. The THV is first crimped and deployed into an idealized ascending aorta. During the FSI simulation, the radial outward force and friction force between the aortic wall and the THV frame are examined over the entire cardiac cycle. The ratio between these two forces is computed and compared with the experimentally estimated coefficient of friction to study the likelihood of valve migration.

TAVI for Pure Native Aortic Regurgitation: Are We There Yet?

Treatment of degenerative aortic stenosis has been transformed by transcatheter aortic valve implantation (TAVI) over the past 10-15 years. The success of various technologies has led operators to attempt to broaden the indications, and many patients with native valve aortic regurgitation have been treated 'off label' with similar techniques. However, the alterations in the structure of the valve complex in pure native aortic regurgitation are distinct to those in degenerative aortic stenosis, and there are unique challenges to be overcome by percutaneous valves. Nevertheless some promise has been shown with both non-dedicated and dedicated devices. In this article, the authors explore some of these challenges and review the current evidence base for TAVI for aortic regurgitation.

Impact of annular and supra-annular CoreValve deployment locations on aortic and coronary artery hemodynamics

CoreValve is widely used in transcatheter aortic valve replacement, but the impact of its deployment location on hemodynamics is unexplored despite a potential role in subsequent aortic and coronary artery pathologies. The objectives of this investigation were to perform fluid-structure interaction (FSI) simulations for a 29 mm CoreValve deployed in annular vs supra-annular locations, and characterize resulting hemodynamics including velocity and wall shear stress (WSS). Patient-specific geometry was reconstructed from computed tomography scans and CoreValve was deployed using a finite element approach. FSI simulations were then performed using a boundary conforming method and realistic boundary conditions. Results showed that CoreValve deployment location impacts hemodynamics in the ascending aorta and flow patterns in the coronary arteries. During peak-systole, annularly deployed CoreValve produced a jet-like flow structure impinging on the outer-curvature of the ascending aorta. Supra-annularly deployed CoreValve having a lateral tilt of 10° led to a more centered jet impinging further downstream. At mid-systole, valve leaflets of the annularly deployed CoreValve closed asymmetrically leading to disorganized flow patterns in the ascending aorta vs those from the supra-annular position. Supra-annularly deployed CoreValve also led to high-velocity para-valvular flow supplying the coronary arteries. CoreValve in the supra-annular position significantly (P < 0.05) elevated WSS within the first few diameters of both coronary arteries as compared to the annular position for many time points quantified. These results afforded by the advanced simulation methods may have important clinical implications given the role of aortic hemodynamics in dilation and the pro-atherogenic nature of WSS alterations in the coronary arteries.

One-Year Outcomes of Transcatheter Aortic Valve Implantation Using the Direct Aortic Approach

BACKGROUND

The direct aortic (DA) approach allows for transcatheter aortic valve implantation (TAVI) in patients with difficult peripheral vascular anatomy. The CoreValve ADVANCE Direct Aortic (ADVANCE DA) study was performed to assess the outcomes of DA TAVI with the CoreValve System (Medtronic, Minneapolis, MN) in routine practice.

METHODS

Patients were selected for the DA approach by local cardiac surgical teams, and TAVI was performed with patients under general anesthesia. Safety events were adjudicated according to the Valve Academic Research Consortium-2 definitions by an independent clinical events committee. All imaging data, including that from multislice computed tomography and follow-up echocardiography, were analyzed by an independent core laboratory.

RESULTS

From September 2012 to February 2014, 100 patients were enrolled (52.0% male, age 81.9 ± 5.9 years, The Society of Thoracic Surgeons Score 5.9 ± 3.2%) at 9 centers in Europe. Peripheral vascular disease was present in 51.0% of patients, and 38.0% had diabetes. Of the 100 patients enrolled, 92 underwent TAVI. At 30 days after TAVI, 98.1% were free of moderate or severe paravalvular leak. At 1 year, 16 patients had died (Kaplan-Meier rate 17.9%), 1 (1.1%) patient had had a stroke, classified as nondisabling, and 15 (17.0%) patients had received a permanent pacemaker. Most patients experienced improved quality of life as measured by the Kansas City Cardiomyopathy Questionnaire overall summary score (mean change from baseline to 1 year, 39.6 ± 26.3; p < 0.01).

CONCLUSIONS

The DA approach provides a feasible alternative for patients with challenging anatomic features that may otherwise preclude use of the TAVI procedure.

Self-expandable CoreValve implantation without contrast media

Transcatheter aortic valve implantation has been designed to treat high-risk surgical patients affected by severe aortic stenosis, many of whom are affected by chronic kidney disease. To perform transcatheter self-expandable valve implantation, multiple contrast injections are required to monitor the procedure, so these patients are at increased risk of acute kidney injury. We described self-expandable transcatheter aortic valve implantation without contrast media in an 80-year-old man affected by severe aortic stenosis and endstage chronic kidney disease.

An up-to-date overview of the most recent transcatheter implantable aortic valve prostheses

Over the past decade transcatheter aortic valve implantation (TAVI) has evolved towards the routine therapy for high-risk patients with severe aortic valve stenosis. Technical refinements in TAVI are rapidly evolving with a simultaneous expansion of the number of available devices. This review will present an overview of the current status of development of TAVI-prostheses; describes the technical features and applicability of each device and the clinical data available.

Robot-assisted real-time magnetic resonance image-guided transcatheter aortic valve replacement

BACKGROUND

Real-time magnetic resonance imaging (rtMRI)-guided transcatheter aortic valve replacement (TAVR) offers improved visualization, real-time imaging, and pinpoint accuracy with device delivery. Unfortunately, performing a TAVR in a MRI scanner can be a difficult task owing to limited space and an awkward working environment. Our solution was to design a MRI-compatible robot-assisted device to insert and deploy a self-expanding valve from a remote computer console. We present our preliminary results in a swine model.

METHODS

We used an MRI-compatible robotic arm and developed a valve delivery module. A 12-mm trocar was inserted in the apex of the heart via a subxiphoid incision. The delivery device and nitinol stented prosthesis were mounted on the robot. Two continuous real-time imaging planes provided a virtual real-time 3-dimensional reconstruction. The valve was deployed remotely by the surgeon via a graphic user interface.

RESULTS

In this acute nonsurvival study, 8 swine underwent robot-assisted rtMRI TAVR for evaluation of feasibility. Device deployment took a mean of 61 ± 5 seconds. Postdeployment necropsy was performed to confirm correlations between imaging and actual valve positions.

CONCLUSIONS

These results demonstrate the feasibility of robotic-assisted TAVR using rtMRI guidance. This approach may eliminate some of the challenges of performing a procedure while working inside of an MRI scanner, and may improve the success of TAVR. It provides superior visualization during the insertion process, pinpoint accuracy of deployment, and, potentially, communication between the imaging device and the robotic module to prevent incorrect or misaligned deployment.

Real-time magnetic resonance imaging-guided transcatheter aortic valve replacement

OBJECTIVES

To demonstrate the feasibility of Real-time magnetic resonance imaging (rtMRI) guided transcatheter aortic valve replacement (TAVR) with an active guidewire and an MRI compatible valve delivery catheter system in a swine model.

METHODS

The CoreValve system was minimally modified to be MRI-compatible by replacing the stainless steel components with fluoroplastic resin and high-density polyethylene components. Eight swine weighing 60-90 kg underwent rtMRI-guided TAVR with an active guidewire through a left subclavian approach.

RESULTS

Two imaging planes (long-axis view and short-axis view) were used simultaneously for real-time imaging during implantation. Successful deployment was performed without rapid ventricular pacing or cardiopulmonary bypass. Postdeployment images were acquired to evaluate the final valve position in addition to valvular and cardiac function.

CONCLUSIONS

Our results show that the CoreValve can be easily and effectively deployed through a left subclavian approach using rtMRI guidance, a minimally modified valve delivery catheter system, and an active guidewire. This method allows superior visualization before deployment, thereby allowing placement of the valve with pinpoint accuracy. rtMRI has the added benefit of the ability to perform immediate postprocedural functional assessment, while eliminating the morbidity associated with radiation exposure, rapid ventricular pacing, contrast media renal toxicity, and a more invasive procedure. Use of a commercially available device brings this rtMRI-guided approach closer to clinical reality.

Right anterior mini-thoracotomy direct aortic self-expanding trans-catheter aortic valve implantation: A single center experience

OBJECTIVE

Transcatheter aortic valve implantation (TAVI) has been designed to treat elderly patients with severe aortic stenosis at high risk for surgery. These patients are also often affected by severe iliac-femoral arteriopathy, rendering the trans-femoral approach unusable. We report our experience with the direct-aortic approach to treat these patients.

METHODS

From May 2008 to November 2013 two hundred and thirty-two patients (131 female, 56%) with severe symptomatic aortic stenosis and no reasonable surgical option due to excessive risk were evaluated for TAVI at our department. Of these patients, 202 were deemed eligible for TAVI. Of this group, 50 underwent CoreValve implantation by the direct aortic approach through a right anterior mini-thoracotmy (28 female, 56%), mean age 81.2±6.9. A combined team of cardiologists, cardiac surgeons with expertise in hybrid procedures, and anesthetists performed all the procedures.

RESULTS

Twenty-eight (56%) patients were female and 11 (22%) were redo at TAVI. We used a 23-mm CoreValve Evolute in 3 patients (6%), and the most used valve size was the 29mm in 46% of patients. Mean hemodynamic trans-aortic gradient was less than 5mmHg. The paravalvular regurgitation was ≤ grade 1 in 46 patients as assessed by peri-procedural transesophageal echocardiography (TEE). Seven patients (7/43, 16%) required a permanent pacemaker implantation; 30-day mortality was 6% (3 patients). Seven patients (14.8%) died during follow-up. Actuarial survival at 2years is 84.7±5.3%.

CONCLUSIONS

Transcatheter aortic valve implantation with the direct aortic approach is safe and feasible, offering a new attractive option to treat selected high-risk patients with severe aortic stenosis and peripheral vasculopathy, including those requiring a re-do procedure.

Self-expanding prostheses for transcatheter aortic valve replacement

Transcatheter aortic valve replacement (TAVR) has emerged as an alternative to surgical aortic valve replacement in patients who are considered high surgical risk or inoperable due to advanced age and comorbidities. Randomized trial and registry data have demonstrated the safety and efficacy of TAVR in such patients. Currently available transcatheter heart valves (THVs) employ either balloon-expandable or self-expanding designs, and several new designs have shown promising early results. Differences in valve design may offer specific advantages for accurate deployment and minimizing complications. This article reviews several designs of self-expanding THVs that are currently available or have undergone successful implantation in humans. Additional studies are required to compare the relative performance of these devices.

Direct aortic transcatheter valve implantation via mini-thoracotomy using the Medtronic CoreValve

Transcatheter aortic valve implantation using the Medtronic CoreValve is a well-established procedure. Although previously carried out only through the common femoral artery, today it is possible to perform the procedure through different arterial alternative access sites. A direct aortic approach through the ascending aorta could be carried out via a right anterior mini-thoracotomy in the second intercostal space. The pericardium is opened to expose the aorta. Two purse-string sutures are then placed on the ascending aorta and a standard retrograde CoreValve implantation is performed with the standard delivery system. Advantages, contraindications, surgical technique and results are discussed.