The importance of tissue science and valve design in relation to durability and hemodynamics of the DurAVR aortic heart valve

Introduction

Clinical evidence highlighting the efficacy and safety of transcatheter aortic valve replacement (TAVR) and the 2019 Food and Drug Administration (FDA) approval for TAVR in low-risk (younger) patients has created a demand for durable and long-lasting bioprosthetic heart valve (BHV) leaflet materials. Over the life of an implanted BHV mechanical stress, immunogenicity, calcification, and hemodynamic dysfunction lead to failure via structural valve deterioration (SVD). Consequently, the durability of the bioprosthetic materials selected for valve manufacture is of utmost importance.

Technology

The ADAPT™ tissue engineering process, an anti-calcification preparation that transforms xenograft tissue (bovine pericardium) into a durable valve bioscaffold, shows significant clinical benefits in mitigating the interrelated mechanisms leading to SVD. The novel acellular, biostable and non-calcifying biomaterial has recently been molded into a single-piece 3D biomimetic valve (DurAVR™) with excellent early clinical results and the potential to meet the growing demand of durable BHVs for the treatment of aortic stenosis.

Discussion

The unique design of the DurAVR biomimetic valve in combination with the superior biostability of ADAPT tissue could advance the BHV space by providing superior performance and durability to aortic stenosis patients in need of TAVR.

Partial Heart Transplantation in Adult Cardiac Surgery

Many young adults require heart valve replacements. Current options for valve replacement in adults include mechanical valves, bioprosthetic valves, or the Ross procedure. Of these, mechanical and bioprosthetic valves are the most common options, although mechanical valve usage predominates in younger adults due to durability, while bioprosthetic valve usage predominates in older adults. Partial heart transplantation is a new method of valvular replacement that can deliver durable and self-repairing valves and allow adult patients freedom from anticoagulation therapy. This procedure involves transplantation of donor heart valves only, permitting expanded utilization of donor hearts as compared with orthotopic heart transplantation. In this review, we discuss the potential benefits of this procedure in adults who elect against the anticoagulation regimen required of mechanical valve replacements, although it has not yet been clinically established. Partial heart transplantation is a promising new therapy for the treatment of pediatric valvular dysfunction. This is a novel technique in the adult population with potential utility for valve replacement in young patients for whom anticoagulation therapy is problematic, such as women who wish to become pregnant, patients with bleeding disorders, and patients with active lifestyles.

Transcatheter Heart Valves: A Biomaterials Perspective

Heart valve disease is prevalent throughout the world, and the number of heart valve replacements is expected to increase rapidly in the coming years. Transcatheter heart valve replacement (THVR) provides a safe and minimally invasive means for heart valve replacement in high-risk patients. The latest clinical data demonstrates that THVR is a practical solution for low-risk patients. Despite these promising results, there is no long-term (>20 years) durability data on transcatheter heart valves (THVs), raising concerns about material degeneration and long-term performance. This review presents a detailed account of the materials development for THVRs. It provides a brief overview of THVR, the native valve properties, the criteria for an ideal THV, and how these devices are tested. A comprehensive review of materials and their applications in THVR, including how these materials are fabricated, prepared, and assembled into THVs is presented, followed by a discussion of current and future THVR biomaterial trends. The field of THVR is proliferating, and this review serves as a guide for understanding the development of THVs from a materials science and engineering perspective.

Stent and leaflet stresses across generations of balloon-expandable transcatheter aortic valves

OBJECTIVES

Transcatheter aortic valve replacement (TAVR) is established therapy for severe aortic stenosis patients with intermediate-, high- and prohibitive-risk for surgery. A significant challenge when expanding TAVR to low-risk and younger patients is the unknown long-term durability. High leaflet stresses have been associated with surgical bioprosthetic valve degeneration. In this study, we examined the impact of changes in valve design across 3 generations of same-sized TAVR devices on stent and leaflet stresses.

METHODS

The 26-mm Edwards SAPIEN, 23, 26 and 29 mm SAPIEN XT (XT) and 26 mm SAPIEN 3 (S3) (n = 1 each) underwent micro-computed tomography (micro-CT) scanning. Dynamic finite element computational simulations of 23-26 mm SAPIEN, 23-29 mm XT and 23-29 mm S3 were performed with physiological loading and micro-CT or scaled geometries.

RESULTS

Peak stresses were concentrated in the commissure area and along the bottom of the suture, representing areas most likely to develop structural valve degeneration across TAVR generations. Latest-generation S3 showed greatest 99th percentile principal stress on commissural leaflets for 26 and 29 mm, and increased stresses over XT for 23 mm. Percentage of higher stress areas within the leaflets steadily increased across generations, 3.8%, 3.9% and 5.7%, respectively, for 26 mm SAPIEN, XT and S3 with similar trend for 29-mm valves.

CONCLUSIONS

Using computational simulations based on high-fidelity modelling of balloon-expandable TAVRs, our study demonstrated that maximum stress areas existed in similar leaflet locations across SAPIEN generations, while the latest model S3 had the highest magnitude for both 26- and 29-mm valves. S3 also had the largest area of higher stresses than other generations, which would be prone to degeneration. Our study coupled with future long-term clinical outcomes >10 years will provide insight on biomechanics of TAVR degeneration.

Transcatheter Aortic Valve Replacement versus Surgical Aortic Valve Replacement: A Review of Aortic Stenosis Management

Severe aortic stenosis (AS) affects 3.4% of the elderly over 60 years of age. It presents with exertional dyspnea, syncope, angina, and progression to irreversible congestive heart failure. Early intervention produces a better outcome in preventing the clinical deterioration of AS. The choice of intervention is transcatheter aortic valve implantation or surgical aortic valve replacement (SAVR). The decision should be made after evaluating an individual case based on its clinical features and the user’s experience with transcatheter aortic valve replacement (TAVR). We reviewed available data to illustrate the types of ASs, the background of interventions, current guidelines for TAVR, and its comparison with SAVR in terms of adverse effects.

Transcatheter versus surgical aortic valve replacement in low and intermediate risk patients with severe aortic stenosis: systematic review and meta-analysis of randomized controlled trials and propensity score matching observational studies

Background

To compare the outcome of transcatheter aortic valve replacement (TAVR) with surgical aortic valve replacement (SAVR) in low and intermediate risk patients with severe aortic stenosis (AS). Randomized controlled trials (RCT) and propensity score matching (PSM) studies compare TAVR with SAVR in patients at low and intermediate surgical risk.

Methods

Two authors searched relevant literature independently, then extracted data from the included studies, and assessed risk of bias and quality of study separately according to different study designs, besides that, the extracted data was analyzed via utilization of GRADE system to evaluate the quality of evidence separately.

Results

Overall 15 studies (5 RCTs, 10 PSM studies) with total 12,057 patients were selected. Mortality and disabling stroke during follow-up period were comparable between TAVR and SAVR (RR 1.09, 95% CI: 0.81 to 1.46; RR 0.7, 95% CI: 0.45 to 1.07, respectively), TAVR revealed to be superior to SAVR regarding acute kidney injury (AKI), and onset of new atrial fibrillation (AF) (RCT: high certainty; AKI in PSM: moderate certainty, AF in PSM: low certainty). These results of RCT and PSM studies are consistent. In RCT review, SAVR was better in the following aspects: aortic valve (AV) re-intervention (high certainty), vascular complications, pacemaker implantation (moderate certainty), but comparable in the following aspects: myocardial infarction (MI), aortic insufficient (AI) (moderate certainty), major bleeding (low certainty). In PSM review, SAVR revealed a better result in AI and vascular complications (high certainty), but in the aspects of AV re-intervention, pacemaker implantation, major bleeding and MI (low certainty), it was comparable.

Conclusions

TAVR is comparable to SAVR in terms of mortality and disabling stroke in severe AS patients at low and intermediate risk, but higher proportion of AV re-intervention observed in TAVR. Those results should encourage caution when extending the indications of TAVR into low risk patients, especially for young low risk patients.

Systematic review registration

PROSPERO CRD 42018112626.

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.