Correlation between structural changes and acute thrombogenicity in transcatheter pericardium valves after crimping and balloon deployment

Early thrombus formation including hypo-attenuated leaflet thrombosis after surgical bioprosthetic aortic valve replacement

OBJECTIVE

To assess the occurrence, predictors, and outcomes of hypo-attenuated leaflet thickening (HALT) and thrombus outside the prosthetic valve following surgical aortic valve replacement.

METHODS

A total of 118 patients underwent surgical aortic valve replacement with bioprosthetic valves between July 2020 and June 2022. Sixty-two (52.5%) patients, which is a fairly high number of patients, underwent cardiac computed tomography and transthoracic echocardiography one week after surgery. Patients were divided into two groups, those with HALT (n = 14) and those without HALT (n = 48).

RESULTS

Of the 62 patients who underwent cardiac computed tomography, HALT was observed in 14 (22.5%) patients during the very early postoperative phase. Reduced leaflet motion was observed in two of the 14 patients. The low-attenuation areas were located outside the prosthetic valve in 10 cases (71.4%) in the HALT group and in 14 cases (29.2%) in the non-HALT group. More than 50% of patients (57.1%) with HALT and 79.2% without HALT were administered warfarin. Neither in-hospital deaths nor postoperative thromboembolic events were observed during hospitalization. No patient had a mean pressure gradient > 20 mmHg in either group.

CONCLUSION

HALT was observed in one-fifth of the cases after surgical aortic valve replacement during the very early postoperative phase in an institution wherein administration of continuous heparin infusion after surgery is a standard practice. HALT did not affect the early prognosis or incidence of cerebral infarction.

Development of Antithrombogenic ECM-Based Nanocomposite Heart Valve Leaflets

Thrombogenicity, which is commonly encountered in artificial heart valves after replacement surgeries, causes valvular failure. Even life-long anticoagulant drug use may not be sufficient to prevent thrombogenicity. In this study, it was aimed to develop a heart valve construct with antithrombogenic properties and suitable mechanical strength by combining multiwalled carbon nanotubes within a decellularized bovine pericardium. In this context, the decellularization process was performed by using the combination of freeze–thawing and sodium dodecyl sulfate (SDS). Evaluation of decellularization efficiency was determined by histology (Hematoxylin and Eosin, DAPI and Masson’s Trichrome) and biochemical (DNA, sGAG and collagen) analyses. After the decellularization process of the bovine pericardium, composite pericardial tissues were prepared by incorporating −COOH-modified multiwalled carbon nanotubes (MWCNTs). Characterization of MWCNT incorporation was performed by ATR-FTIR, TGA, and mechanical analysis, while SEM and AFM were used for morphological evaluations. Thrombogenicity assessments were studied by platelet adhesion test, Calcein-AM staining, kinetic blood clotting, hemolysis, and cytotoxicity analyses. As a result of this study, the composite pericardial material revealed improved mechanical and thermal stability and hemocompatibility in comparison to decellularized pericardium, without toxicity. Approximately 100% success is achieved in preventing platelet adhesion. In addition, kinetic blood-coagulation analysis demonstrated a low rate and slow coagulation kinetics, while the hemolysis index was below the permissible limit for biomaterials.

Early and mid-term results of transcatheter aortic valve implantation and valve durability assessment

This study aimed to evaluate the early and mid-term outcomes of transcatheter aortic valve implantation (TAVI) and to assess valve durability. A total of 146 consecutive patients who underwent TAVI for severe aortic stenosis between October 2013 and August 2018 were retrospectively reviewed. All patients (mean age, 84 ± 6 years; age range 53-98 years; 42 males [28.7%]) had multiple comorbidities, with a mean logistic EuroSCORE of 30.9 ± 17.4%. Eighteen patients (12.3%) were aged 90 years or over. Five in-hospital deaths (3.4%) occurred, and 36 patients (24.7%) experienced major TAVI-related complications. With the transfemoral approach, 10 patients had major vascular complications, which mostly occurred with first-generation devices (n = 9) but less commonly with new-generation low-profile devices (P = 0.0078). During a follow-up period of 580 ± 450 (11-1738) days, 29 late deaths occurred. The survival rate was 86.0%, 78.0%, and 61.7% at 1, 2, and 3 years, respectively. Multivariate Cox hazard regression analysis revealed that more-than-moderate tricuspid regurgitation was the only independent risk factor for late deaths due to any cause (hazard ratio, 3.145; 95% confidence interval, 1.129-8.762; P = 0.0283). No statistically significant differences between post-TAVI before discharge from the hospital and at 4 years after TAVI were observed with respect to aortic valve area (1.76 ± 0.49 cm² vs. 1.64 ± 0.38 cm²; P = 0.1871) and mean pressure gradient (10.0 ± 4.6 mmHg vs. 7.9 ± 3.3 mmHg; P = 0.5032). TAVI was a feasible method with acceptable early and mid-term outcomes and valve durability for at least 4 years in poor-risk patients. Further close follow-up is essential to evaluate late outcomes and valve durability.

Transcatheter Aortic Valve Thrombogenesis: A Foreign Materials Perspective

PURPOSE

The initiation of thrombus formation in transcatheter aortic valves (TAVs) is not well understood. The foreign material components of a TAV may play a key role in TAV thrombogenesis. The goal of this study was to evaluate the thrombogenic potential of a TAV (entire valve) and its stent (with skirt).

METHODS

Blood was collected from eight human donors with citrate anticoagulation and later reconstituted with calcium chloride. A low-volume steady flow loop (flow rate = 0.8 L/min) was designed to facilitate three separate conditions (experimental duration = 1 h) per donor blood: (1) control (n = 8), (2) stent-with-skirt (leaflets removed from a 23 mm SAPIEN XT valve; n = 8) and (3) entire valve (an intact 23 mm SAPIEN XT valve; n = 8). Samples were collected at the start and end of each experiment. Serum D-Dimer and thrombin-antithrombin (TAT) concentrations were measured as markers of thrombogenicity.

RESULTS

There was no significant change in serum D-Dimer and TAT concentration with time for the control group. An increasing trend in D-Dimer and TAT concentration was observed with time for the stent-with-skirt group. Interestingly, there was a decreasing trend in serum D-Dimer and TAT concentration with time for the entire valve (leaflet dominating) group. Moreover, changes in D-Dimer and TAT concentration were significantly different between the stent-with-skirt and entire valve (leaflet dominating) groups.

CONCLUSION

Stent-with-skirt was found to impart the most prominent thrombogenic effect, indicating the significance of blood-stent and blood-skirt interactions in TAV thrombosis.

Degeneration of Bioprosthetic Heart Valves: Update 2020

The implantation of bioprosthetic heart valves (BHVs) is increasingly becoming the treatment of choice in patients requiring heart valve replacement surgery. Unlike mechanical heart valves, BHVs are less thrombogenic and exhibit superior hemodynamic properties. However, BHVs are prone to structural valve degeneration (SVD), an unavoidable condition limiting graft durability. Mechanisms underlying SVD are incompletely understood, and early concepts suggesting the purely degenerative nature of this process are now considered oversimplified. Recent studies implicate the host immune response as a major modality of SVD pathogenesis, manifested by a combination of processes phenocopying the long‐term transplant rejection, atherosclerosis, and calcification of native aortic valves. In this review, we summarize and critically analyze relevant studies on (1) SVD triggers and pathogenesis, (2) current approaches to protect BHVs from calcification, (3) obtaining low immunogenic BHV tissue from genetically modified animals, and (4) potential strategies for SVD prevention in the clinical setting.

Assessment of Long-Term Structural Deterioration of Transcatheter Aortic Bioprosthetic Valves Using the New European Definition

BACKGROUND

The durability of transcatheter aortic bioprosthetic valves is a crucial issue, but data are scarce, especially beyond 5 years of follow-up. We aimed to assess long-term (7 years) structural valve deterioration (SVD) and bioprosthetic valve failure of transcatheter aortic bioprosthetic valves.

METHODS AND RESULTS

Consecutive patients with at least 5-year follow-up available undergoing transcatheter aortic valve implantation from April 2002 to December 2011 in 5 French centers were included. Incidence of SVD and bioprosthetic valve failure were defined according to newly standardized criteria of the European Association of Percutaneous Cardiovascular Interventions/European Society of Cardiology/European Association for Cardio-Thoracic Surgery and reported as cumulative incidence function to account for the competing risk of death. One thousand four hundred three consecutive patients were included with a mean age of 82.6±7.5 years and with a mean logistic EuroSCORE (European System for Cardiac Operative Risk Evaluation) of 21.3±7.5%. A balloon-expandable valve was used in 83.7% of cases. Survival rates were 83.5% (95% CI, 81.4%-85.5%) and 18.6% (95% CI, 15.3%-21.8%) at 1 and 7 years, respectively. Median duration of follow-up was 3.9 years. Bioprosthetic valve failure occurred in 19 patients with a 7-year cumulative incidence of 1.9% (95% CI, 1.4%-2.4%). SVD occurred in 49 patients (moderate, n=32; severe, n=17) with a 7-year cumulative incidence of moderate and severe SVD of 7.0% (95% CI, 5.6%-8.4%) and 4.2% (95% CI, 2.9%-5.5%), respectively. Five patients had aortic valve reintervention (1.0%; 95% CI, 0.4%-1.6%) including 1 case of surgical aortic valve replacement and 4 redo-transcatheter aortic valve implantation. The incidences of SVD and bioprosthetic valve failure were not significantly different between balloon and self-expandable prostheses.

CONCLUSIONS

The long-term assessment of transcatheter aortic bioprosthetic valves durability is limited by the poor survival of our population beyond 5 years. Further studies are warranted, particularly in younger and lower-risk patients.

Postimplant biological aortic prosthesis degeneration: challenges in transcatheter valve implants

Surgical aortic valve replacement (SAVR) is highly effective and can be achieved with relatively low risk in patients with severe aortic stenosis. Bioprostheses have been used most frequently during the past 60 years. However, the function of biological valves usually declines after 10-15 years from implant when structural valve degeneration occurs often mandating a reoperation once valve dysfunction becomes haemodynamically significant. Known for many years by surgeons and cardiologists taking care of patients with SAVR, the issue of postimplant structural valve degeneration has been recently highlighted also in patients with transcatheter aortic valve implant (TAVI). There is growing concern that TAVI valves exhibit structural valve degeneration due to inherent challenges of the deployment mode. The impact on postimplant degeneration of TAVI valves compared to SAVR has still to be understood and defined. Based on the ongoing process of expanding TAVI indications, several potential shortcomings and caveats, learned during the last 60 years of SAVR experience, should be taken into consideration to refine this technique.

Antithrombotic Therapy in Transcatheter Aortic Valve Replacement

Transcatheter aortic valve replacement (TAVR) has recently emerged as an effective alternative to medical treatment or surgical aortic valve replacement in all symptomatic patients with severe aortic stenosis and high or prohibitive risk and in intermediate risk when transfemoral access is feasible. Patients undergoing TAVR are often at high risk for either bleeding or cerebrovascular complications, or both, so adjuvant antithrombotic therapies are commonly used before, during and after the procedure. Today, there is no clear evidence on the best antithrombotic regimen in this context. In this review, we will try to go through the mechanisms involved in bleeding and embolic complications and we will discuss the current points of antithrombotic treatment in patients during and after TAVR, with or without oral anticoagulation (OAC) indication.

The Red Kangaroo pericardium as a material source for the manufacture of percutaneous heart valves

BACKGROUND

The kangaroo pericardium might be considered to be a good candidate material for use in the manufacture of the leaflets of percutaneous heart valves based upon the unique lifestyle. The diet consists of herbs, forbs and strubs. The kangaroo pericardium holds an undulated structure of collagen.

MATERIAL AND METHOD

A Red Kangaroo was obtained after a traffic fatality and the pericardium was dissected. Four compasses were cut from four different sites: auricular (AUR), atrial (ATR), sternoperitoneal (SPL) and phrenopericardial (PPL). They were investigated by means of scanning electron microscopy, light microscopy and transmission electron microscopy.

RESULTS

All the samples showed dense and wavy collagen bundles without vascularisation from both the epicardium and the parietal pericardium. The AUR and the ATR were 150±25μm thick whereas the SPL and the PPL were thinner at 120±20μm. The surface of the epicardium was smooth and glistening. The filaments of collagen were well individualized without any aggregation, but the banding was poorly defined and somewhat blurry.

CONCLUSION

This detailed morphological analysis of the kangaroo pericardium illustrated a surface resistant to thrombosis and physical characteristics resistant to fatigue. The morphological characteristics of the kangaroo pericardium indicate that it represents an outstanding alternative to the current sources e.g., bovine and porcine. However, procurement of tissues from the wild raises supply and sanitary issues. Health concerns based upon sanitary uncertainty and reliability of supply of wild animals remain real problems.

Principles of TAVR valve design, modelling, and testing

INTRODUCTION

Transcatheter aortic valve replacement (TAVR) has emerged as an effective minimally-invasive alternative to surgical valve replacement in medium- to high-risk, elderly patients with calcific aortic valve disease and severe aortic stenosis. The rapid growth of the TAVR devices market has led to a high variety of designs, each aiming to address persistent complications associated with TAVR valves that may hamper the anticipated expansion of TAVR utility.

AREAS COVERED

Here we outline the challenges and the technical demands that TAVR devices need to address for achieving the desired expansion, and review design aspects of selected, latest generation, TAVR valves of both clinically-used and investigational devices. We further review in detail some of the up-to-date modeling and testing approaches for TAVR, both computationally and experimentally, and additionally discuss those as complementary approaches to the ISO 5840-3 standard. A comprehensive survey of the prior and up-to-date literature was conducted to cover the most pertaining issues and challenges that TAVR technology faces.

EXPERT COMMENTARY

The expansion of TAVR over SAVR and to new indications seems more promising than ever. With new challenges to come, new TAV design approaches, and materials used, are expected to emerge, and novel testing/modeling methods to be developed.

Assessment of structural valve deterioration of transcatheter aortic bioprosthetic balloon-expandable valves using the new European consensus definition

AIMS

Durability of transcatheter aortic bioprosthetic valves remains a major issue. Standardised definitions of deterioration and failure of bioprosthetic valves have recently been proposed. The aim of this study was to assess structural transcatheter valve deterioration (SVD) and bioprosthetic valve failure (BVF) using these new definitions.

METHODS AND RESULTS

All TAVI patients implanted up to September 2012 with a minimal theoretical five-year follow-up were included. Systematic clinical and echocardiographic follow-up was performed annually. New standardised definitions were used to assess durability of transcatheter aortic bioprosthetic valves. From 2002 to 2012, 378 patients were included. Mean age and logistic EuroSCORE were 83.3±6.8 years and 22.8±13.1%. Thirty-day mortality was 13.2%. Nine patients had SVD including two severe forms and two patients had definite late BVF. The incidence of SVD and BVF at eight years was 3.2% (95% CI: 1.45-6.11) and 0.58% (95% CI: 0.15-2.75), respectively.

CONCLUSIONS

Even though limited by the poor survival of the very high-risk/compassionate early population, our data do not demonstrate any alarm concerning transcatheter aortic valve durability. Careful prospective assessment in younger and lower-risk patients and comparison with surgical bioprosthetic valves are required for further assessment of the long-term durability of transcatheter valves.

Bioprosthetic aortic valve durability in the era of transcatheter aortic valve implantation

The main limitation of bioprosthetic valves is their limited durability, which exposes the patient to the risk of aortic valve reintervention. Transcatheter aortic valve implantation (TAVI) is considered a reasonable alternative to surgical aortic valve replacement (SAVR) in patients with intermediate or high surgical risk. TAVI is now rapidly expanding towards the lower risk populations. Although the results of midterm durability of the transcatheter bioprostheses are encouraging, their long-term durability remains largely unknown. The objective of this review article is to present the definition, mechanisms, incidence, outcome and management of structural valve deterioration of aortic bioprostheses with specific emphasis on TAVI. The structural valve deterioration can be categorised into three stages: stage 1: morphological abnormalities (fibrocalcific remodelling and tear) of bioprosthesis valve leaflets without hemodynamic valve deterioration; stage 2: morphological abnormalities and moderate hemodynamic deterioration (increase in gradient and/or new onset of transvalvular regurgitation); and stage 3: morphological abnormalities and severe hemodynamic deterioration. Several specifics inherent to the TAVI including valve oversizing, manipulation, delivery, positioning and deployment may cause injuries to the valve leaflets and increase leaflet mechanical stress, which may limit the long-term durability of transcatheter bioprostheses. The selection of the type of aortic valve replacement and bioprosthesis should thus take into account the ratio between the demonstrated durability of the bioprostheses versus the life expectancy of the patient. Pending the publication of robust data on long-term durability of transcatheter bioprostheses, it appears reasonable to select SAVR with a bioprosthesis model that has well-established long-term durability in patients with low surgical risk and long life expectancy.

[Antiplatelet or anticoagulative strategies after surgical/interventional valve treatment]

At the end of August 2017 the European Society of Cardiology (ESC) and the European Association for Cardio-Thoracic Surgery (EACTS) published new joint guidelines for the treatment of valvular heart disease. These guidelines incorporate the scientific progress since the last version of the guidelines published in 2012. This article reviews current guideline recommendations for antiplatelet and anticoagulative therapy after surgical/interventional treatment of the aortic and mitral valves and discusses the underlying scientific evidence.