Long-term performance of heart valve prostheses

Successful Reversal of Late, Severe Thrombotic Bioprosthetic Mitral Valve Stenosis With Anticoagulation Therapy

Late bioprosthetic valve thrombosis (bPVT) is a rare and potentially life-threatening complication following valve replacement with thrombus formation leading mostly to valvular stenosis or embolic phenomena. Clinically, it manifests as symptoms of fatigue, dyspnea, or reduced exercise capacity. The existing treatment guidelines lack clear recommendations for managing this specific presentation. In this case study, we present a distinct clinical scenario wherein the use of anticoagulation, specifically apixaban, successfully reversed very late, severe thrombotic stenosis in a 78-year-old woman with a Medtronic Hancock II porcine mitral valve (Dublin, Ireland). This case highlights the need to consider bPVT as an alternative etiology to valve degeneration in the setting of late bioprosthetic valve stenosis. Additionally, it demonstrates how apixaban therapy may serve as a viable treatment modality in these scenarios.

Left atrial Thrombus formation after discontinuation of anticoagulation in patient with severe bioprosthetic mitral stenosis

BACKGROUND

Mitral valve stenosis can be a highly symptomatic condition with significant complications if left untreated. In such cases, mitral valve replacement with a bioprosthetic or mechanical valve may be a viable solution to prevent progressive disease. Current guidelines do not recommend continued anticoagulation beyond 6 months for patients who have undergone bioprosthetic valve replacement without a separate indication for anticoagulation. With this case discussion we aim to 1) Review the current indications for anticoagulation for bioprosthetic mitral valves in patients without atrial fibrillation and 2) Discuss the constellation of comorbidities that may affect the decision to begin anticoagulation therapy.

CASE PRESENTATION

We present a case describing a 55-year-old male with end-stage renal disease, coronary artery disease with coronary artery bypass graft surgery, and bioprosthetic mitral valve replacement 2 years prior with rapid degeneration of the replaced valve and on warfarin without a clear indication for anticoagulation. The patient was admitted for symptomatic, severe mitral stenosis and consideration of transcatheter mitral valve-in-valve replacement. During hospital admission, warfarin was discontinued and replaced with prophylactic anticoagulation. However, 8 days after warfarin cessation an intraoperative transesophageal echocardiography revealed a newly developed large left atrial thrombus leading to cancellation of the planned operation.

CONCLUSIONS

This patient developed a left atrial thrombus after discontinuing warfarin in the setting of rapidly deteriorating bioprosthetic valve stenosis and vascular comorbidities. The decision to discontinue warfarin was made in concordance with current guidelines, which do not indicate systemic anticoagulation post 3-6 months after bioprosthetic valve replacement without separate indication for anticoagulation. This case identifies the need to investigate rebound hypercoagulability and further risk stratify comorbidities which may independently increase the risk of clot formation in the setting of severe mitral valve stenosis.

Sacrificial scaffold-assisted direct ink writing of engineered aortic valve prostheses

Heart valve disease has become a serious global health problem, which calls for numerous implantable prosthetic valves to fulfill the broader needs of patients. Although current three-dimensional (3D) bioprinting approaches can be used to manufacture customized valve prostheses, they still have some complications, such as limited biocompatibility, constrained structural complexity, and difficulty to make heterogeneous constructs, to name a few. To overcome these challenges, a sacrificial scaffold-assisted direct ink writing approach has been explored and proposed in this work, in which a sacrificial scaffold is printed to temporarily support sinus wall and overhanging leaflets of an aortic valve prosthesis that can be removed easily and mildly without causing any potential damages to the valve prosthesis. The bioinks, composed of alginate, gelatin, and nanoclay, used to print heterogenous valve prostheses have been designed in terms of rheological/mechanical properties and filament formability. The sacrificial ink made from Pluronic F127 has been developed by evaluating rheological behavior and gel temperature. After investigating the effects of operating conditions, complex 3D structures and homogenous/heterogenous aortic valve prostheses have been successfully printed. Lastly, numerical simulation and cycling experiments have been performed to validate the function of the printed valve prostheses as one-way valves.

Scientific Evolution of Artificial Heart Valves: A Narrative Review

Cardiovascular disorders have always been the top contributors to the number of mortality occurring worldwide. But the last few decades have seen a drop in those numbers as the lives of millions of people have been saved due to ground-breaking advances in both therapeutic and surgical treatment modalities. Achieving this level of scientific glory in cardiology was a challenging feat. The credit goes to the scientists and physicians of the previous century who, despite their time's technological limitations, made discoveries and laid a solid foundation for modern medicine. Valvular complications are a major part of the global burden of cardiac diseases. The ongoing development of heart valve replacements remains a fascinating subject, as it continues to progress. Valve replacements comprise either mechanical heart valves or bioprosthetic heart valves. Both types of valves have their merits and demerits; their usage depends mostly on individual patient requirements. This article aims to review the evolution of the implantation of heart valves, and it is the objective of this article to give credit to scientists and physicians for their contributions. The article highlights the research gaps in finding more durable materials and the scope of further research in creating a heart valve that can be universally used for better patient outcomes.

MarioHeart: Novel In-Vitro Flow Model for Testing Heart Valve Prostheses and Anticoagulant Therapies

Mechanical heart valve (MHV) prostheses present a risk of thromboembolic complications despite antithrombotic therapy. Further steps in the development of more hemocompatible MHVs and new anticoagulants are impeded due to the lack of adequate in-vitro models. With the development of a novel in-vitro model (MarioHeart), a pulsatile flow similar to the arterial circulation is emulated. The MarioHeart design owns unique features as 1) a single MHV within a torus with low surface/volume ratio, 2) a closed loop system, and 3) a dedicated external control system driving the oscillating rotational motion of the torus. For verification purposes, a blood analog fluid seeded with particles was used to assess fluid velocity and flow rate using a speckle tracking method on high-speed video recordings of the rotating model. The flow rate resembled the physiological flow rate in the aortic root, in both shape and amplitude. Additional in-vitro runs with porcine blood showed thrombi on the MHV associated with the suture ring, which is similar to the in-vivo situation. MarioHeart is a simple design which induces well-defined fluid dynamics resulting in physiologically nonturbulent flow without stasis of the blood. MarioHeart seems suitable for testing the thrombogenicity of MHVs and the potential of new anticoagulants.

Mid-term follow-up and outcomes of patients with prosthetic heart valves: a single-centre experience

BACKGROUND

Patients with prosthetic heart valves (PHV) require long-term follow-up, usually within a physiologist led heart valve surveillance clinic. These clinics are well established providing safe and effective patient care. The disruption of the COVID-19 pandemic on services has increased wait times thus we undertook a service evaluation to better understand the patients currently within the service and PHV related complications.

METHODS

A clinical service evaluation of the heart valve surveillance clinic was undertaken to assess patient demographics, rates of complications and patient outcomes in patients who had undergone a PHV intervention at our institute between 2010 and 2020.

RESULTS

A total of 294 patients (mean age at time of PHV intervention: 71 ± 12 years, 68.7% male) were included in this service evaluation. Follow-up was 5.9 ± 2.7 years (range: 10 years). 37.1% underwent baseline transthoracic echo (TTE) assessment and 83% underwent annual TTE follow-up. Significant valve related complications were reported in 20 (6.8%) patients. Complications included a change in patient functional status secondary to significant PHV regurgitation (0.3%) or stenosis (0.3%), PHV thrombosis (0.3%) or infective endocarditis (3.7%). Significant valve related complications resulted in ten hospital admission (3.4%), two re-do interventions (0.6%), and four deaths (1.3%).

CONCLUSIONS

This service evaluation highlights the large number of patients requiring ongoing surveillance. Only a small proportion of patients develop significant PHV related complications resulting in a low incidence of re-do interventions and deaths.

Isolated aortic valve replacement with bio-prostheses in patients age 50 to 65 years: a decade of statewide data on cost and patient outcomes

BACKGROUND

Guidelines for choice of replacement valve-mechanical versus bio-prosthetic, are well established for patients aged <50 and >65 years. We studied the trends and implications of aortic valve replacement (AVR) with mechanical versus bioprosthetic valve in patients aged 50 to 65 years.

METHODS

STS and cost database of 17 centers for isolated AVR surgery were analyzed by dividing them into bioprosthetic valve (BV) or mechanical valve (MV) groups.

RESULTS

From 2002 to 2011, 3,690 patients had AVR, 18.6% with MV and 81.4% with BV. Use of BV for all ages increased from 71.5% in 2002 to 87% in 2011. There were 1127 (30.5%) patients in the age group 50-65 years. Use of BV in this group almost doubled, 39.6% in 2002 to 76.8% in 2011. Mean age of patients in BV group was higher (59.2±4.2 years vs. 56.7±4.3 years, P≤0.0001). Preoperative renal failure, heart failure and chronic obstructive pulmonary disease favored use of BV, whereas preoperative atrial fibrillation favored AVR with MV. Mortality (MV 2.2% vs. BV 2.36%) and other postoperative outcomes between the groups were similar. Cost of valve replacement increased for both groups (MV $26,191 in 2002 to $42,592 in 2011; BV $27,404 in 2002 to $44,257 in 2011).

CONCLUSIONS

Use of bioprostheses for AVR has increased; this change is more pronounced in patients aged 50-65 years. Specific preoperative risk factors influence the choice of valve for AVR. Postoperative outcomes between the two groups were similar. Long-term implications of this changing practice, in particular, reoperation for bioprosthetic valve degeneration should be examined.

The effectiveness and safety of pulmonary autograft as living tissue in Ross procedure: a systematic review

BACKGROUND

Reports on effectiveness and safety after the implant of pulmonary autograft (PA) living tissue in Ross procedure, to treat both congenital and acquired disease of the aortic valve and left ventricular outflow tract (LVOT), show variable durability results. We undertake a quantitative systematic review of evidence on outcome after the Ross procedure with the aim to improve insight into outcome and potential determinants.

METHODS

A systematic search of reports published from October 1979 to January 2021 was conducted (PubMed, Ovid Medline, Ovid Embase and Cochrane library) reporting outcomes after the Ross procedure in patients with diseased aortic valve with or without LVOT. Inclusion criteria were observational studies reporting on mortality and/or morbidity after autograft aortic valve or root replacement, completeness of follow-up >90%, and study size n≥30. Forty articles meeting the inclusion criteria were allocated to two categories: pediatric patient series and young adult patient series. Results were tabulated for a clearer presentation.

RESULTS

A total of 342 studies were evaluated of which forty studies were included in the final analysis as per the eligibility criteria. A total of 8,468 patients were included (7,796 in pediatric cohort and young adult series and 672 in pediatric series). Late mortality rates were remarkably low alongside similar age-matched mortality with the general population in young adults. There were differences in implantation techniques as regard the variability in stress and the somatic growth that recorded conflicting outcomes regarding the miniroot vs the subcoronary approach.

DISCUSSION

The adaptability of lung autograft to allow for both stress variability and somatic growth make it an ideal conduit for Ross's operation. The use of the miniroot technique over subcoronary implantation for better adaptability to withstand varying degrees of stress is perhaps more applicable to different patient subgroups.

Care of the patient after valve intervention

This review aims to outline the current evidence base and guidance for care of patients post-valve intervention. Careful follow-up, optimisation of medical therapy, antithrombotics, reduction of cardiovascular risk factors and patient education can help improve patient outcomes and quality of life. Those with mechanical valves should receive lifelong anticoagulation with a vitamin K antagonist but in certain circumstances may benefit from additional antiplatelet therapy. Patients with surgical bioprosthetic valves, valve repairs and transcatheter aortic valve implantation also benefit from antithrombotic therapy. Additionally, guideline-directed medical therapy for coexistent heart failure should be optimised. Cardiovascular risk factors such as hyperlipidaemia, hypertension and diabetes should be treated in the same way as those without valve intervention. Patients should also be encouraged to exercise regularly, eat healthily and maintain a healthy weight. Currently, there is not enough evidence to support routine cardiac rehabilitation in individuals post-valve surgery or intervention but this may be considered on a case-by-case basis. Women of childbearing age should be counselled regarding future pregnancy and the optimal management of their valve disease in this context. Patients should be educated regarding meticulous oral health, be encouraged to see their dentist regularly and antibiotics should be considered for high-risk dental procedures. Evidence shows that patients post-valve intervention or surgery are best treated in a dedicated valve clinic where they can undergo clinical review and surveillance echocardiography, be provided with heart valve education and have access to the multidisciplinary valve team if needed.

Bacitracin and isothiocyanate functionalized silver nanoparticles for synergistic and broad spectrum antibacterial and antibiofilm activity with selective toxicity to bacteria over mammalian cells

Silver nanoparticles functionalized with bacitracin (BA), a cyclic peptide and isothiocyanate (ITC), a natural plant product, was fabricated. The particle size of AgNP-BA&ITC was optimized using full factorial design. The optimized particles were of 10-15 nm in size as seen under TEM and showed chemical signature of both bacitracin as well as isothiocynate in FTIR spectroscopy. XRD analysis confirmed the crystalline nature of these particles. Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS) showed 21 mg/g silver content in AgNP-BA &ITC. These nanoparticles exhibited MIC in the range of 12.5-25 μg/mL and > 3 log₁₀ reduction in cell viability for both Gram positive and Gram-negative bacteria. They clearly demonstrated biofilm inhibition (BIC₉₀ = 150-400 μg/mL) as well as were capable of eradicating both young and mature preformed biofilms as observed by live/dead imaging and crystal violet assay. Further cytotoxicity assay suggests high selectivity (IC₅₀/MIC₉₀ value = 15.2-30.4) of these particles. The results in the present investigation provide role of these novel nanoparticles having substantially low silver content with reduced toxicity and good antibacterial and antibiofilm activity for external wound healing applications.

Neurologic complications of nonrheumatic valvular heart disease

Valvular heart disease (VHD) is frequently associated with neurologic complications. Cerebral embolism is the most common, since thrombus formation results from the abnormalities in the valvular surfaces and the anatomic and physiologic changes associated with valve dysfunction, including atrial or ventricular enlargement, intracardiac thrombi, and cardiac dysrhythmias. Prosthetic heart valves, particularly mechanical valves, are very thrombogenic, which explains the high risk of thromboembolism and the need for long-term anticoagulation. Transcatheter aortic valve replacement (TAVR) has emerged as a nonoperative alternative to surgical aortic valve replacement for patients with intermediate or high surgical risk, and the procedure also has a risk of cerebral ischemia. In addition, anticoagulation, the mainstay of treatment to prevent cerebral embolism, has known potential for hemorrhagic complications. The emergence of new oral anticoagulants with similar effectiveness to warfarin and a better safety profile has facilitated the management of patients with atrial fibrillation. However, their application in patients with mechanical heart valves is still evolving. The prevention and management of these complications requires an understanding of their natural history to balance the risks posed by valvular heart disease, as well as the risks and benefits associated with the treatment.

History, development and clinical perspectives of sutureless and rapid deployment surgical aortic valve replacement

Degenerative aortic stenosis is the most frequent valvular heart disease in industrialized countries. Conservative treatment may beneficially influence symptoms but is never successful. Surgical aortic valve replacement (SAVR) was the only recognized treatment option to provide substantially prolonged survival until 2008. Operative mortality of isolated SAVR has been reported as low as 0.5% to 1% in experienced institutions, while long-term survival is close to that observed in a control healthy population of similar age. A multitude of studies have demonstrated the beneficial effects of SAVR with regard to improvement in quality of life and physical performance in the majority of symptomatic patients. In the last decade, transcatheter aortic valve implantation (TAVI) has emerged as an equal treatment modality, first in patients with high surgical risk and more recently in patients with intermediate and low surgical risk. Paravalvular regurgitation and the higher rate of pacemaker implantation remain points of consideration. Additionally, the long-term durability of TAVI devices and occurrence of stroke late after TAVI require additional analyses. Sutureless (SU-SAVR) and rapid deployment valve (R-SAVR) were designed to simplify and accelerate a conventional or less invasive surgical procedure while allowing complete excision of the calcified native valve. From 3 different implants tested more than 10 to 15 years ago, only two are available on the market today: the Perceval^® valve from Liva Nova and the Intuity^® sutureless prosthesis from Edwards Lifesciences. There has been extensive experience with these two devices in previous years and the results obtained are comparable to those observed following the use of conventional implants. The sutureless devices may be of particular interest for more complex and combined surgical procedures. This review summarizes the sutureless (SU-SAVR) and rapid deployment valve technologies and presents a clinical outlook for the patient population managed with these devices.

Bovine Pericardium of High Fibre Dispersion Has High Fatigue Life and Increased Collagen Content; Potentially an Untapped Source of Heart Valve Leaflet Tissue

Bioprosthetic heart valves (BHVs) are implanted in aortic valve stenosis patients to replace the native, dysfunctional valve. Yet, the long-term performance of the glutaraldehyde-fixed bovine pericardium (GLBP) leaflets is known to reduce device durability. The aim of this study was to investigate a type of commercial-grade GLBP which has been over-looked in the literature to date; that of high collagen fibre dispersion (HD). Under uniaxial cyclic loading conditions, it was observed that the fatigue behaviour of HD GLBP was substantially equivalent to GLBP in which the fibres are highly aligned along the loading direction. It was also found that HD GLBP had a statistically significant 9.5% higher collagen content when compared to GLBP with highly aligned collagen fibres. The variability in diseased BHV delivery sites results in unpredictable and complex loading patterns across leaflets in vivo. This study presents the possibility of a shift from the traditional choice of circumferentially aligned GLBP leaflets, to that of high fibre dispersion arrangements. Characterised by its high fatigue life and increased collagen content, in addition to multiple fibre orientations, GLBP of high fibre dispersion may provide better patient outcomes under the multi-directional loading to which BHV leaflets are subjected in vivo.

Periprocedural and long-term safety and feasibility of direct oral anticoagulants in patients with biological valve undergoing radiofrequency catheter ablation for atrial fibrillation: a prospective multicenter study

BACKGROUND

Direct oral anticoagulants (DOACs) are contraindicated in patients with atrial fibrillation (AF) and mechanical cardiac valves. However, safety and efficacy are controversial in patients with biological cardiac valves.

OBJECTIVE

We report the safety and feasibility of periprocedural and long-term treatment with DOACs in patients with biological valves undergoing ablation for AF.

METHODS

A total of 127 patients with AF and biological cardiac valve undergoing CA on uninterrupted DOAC were matched by gender and age with 127 patients with AF and biological cardiac valves undergoing CA on uninterrupted warfarin. All patients were anticoagulated for at least 3-4 weeks prior to ablation with either rivaroxaban (70%) or apixaban (30%), which were continued for at least 3 months and subsequently based on CHA₂DS₂-VASc score.

RESULTS

Mean age of the study population was 63.0 ± 10.9 with 66% being male. The majority of patients on NOACs had aortic valve replacement (59%), while mitral valve was replaced in 41% of patients, which did not differ from the matched cohort on coumadin (aortic valve 57% and mitral valve 43%, (p = 0.8) (p = 0.8), respectively). The CHADS₂ score was ≥ 2 in 90 patients (71.0%) on DOAC and 86 patients in (68%) the control (p = 0.6) group. Patients underwent ablation predominantly with uninterrupted rivaroxaban [89 (70%)], while the remaining 38 patients (30%) underwent ablation while on apixaban. Two groin hematomas were observed periprocedurally in both groups. No stroke/transient ischemic attack (TIA) was observed both periprocedurally and at long-term follow-up in either group.

CONCLUSION

Periprocedural and long-term administration of DOACs in patients with biological cardiac valves undergoing AF ablation appears as safe as warfarin therapy.

Alternative mechanical heart valves for the developing world

Due to the prevalence of rheumatic heart disease in the developing world, mechanical heart valves in the younger patient population remain the prostheses of choice if repair is not feasible. Despite their durability, mechanical valves are burdened by coagulation and thromboembolism. Modern design tools can be utilized during the design process of mechanical valves, which allow a more systematic design approach and more detailed analysis of the blood flow through and around valves. These tools include computer-aided design, manufacturing, and engineering, such as computational fluid dynamics and finite element analysis, modern manufacturing techniques such as additive manufacturing, and sophisticated in-vitro and in-vivo tests. Following this systematic approach, a poppet valve was redesigned and the results demonstrate the benefits of the method. More organized flow patterns and fewer complex fluid structures were observed. The alternative trileaflet valve design has also been identified as a potential solution and, if a similar design approach is adopted, it could lead to the development of an improved mechanical heart valve in the future. It is imperative that researchers in developing countries continue their search for a mechanical heart valve with a reduced thromboembolic risk, requiring less or no anticoagulation.

Indications for echocardiography of replacement heart valves: a joint statement from the British Heart Valve Society and British Society of Echocardiography

Echocardiography plays a vital role in the follow-up of patients with replacement heart valves. However, there is considerable variation in international guidelines regarding the recommended time points after implantation at which routine echocardiography should be performed. The purpose of routine echocardiography is to detect early structural valve deterioration in biological valves to improve the timing of redo interventions. However, the risk of valve deterioration depends on many valve-related factors (valve design and patient prosthesis mismatch) and patient-related factors (age, diabetes, systemic hypertension, renal dysfunction and smoking). In this statement, the British Heart Valve Society and the British Society of Echocardiography suggest practical guidance. A plan should be made soon after implantation, but this may need to be modified for individual patients and as circumstances change. It is important that patients are managed in a multidisciplinary valve clinic.

Non-vitamin K antagonist oral anticoagulants in atrial fibrillation patients with bioprosthetic valves

INTRODUCTION

The non-vitamin K antagonist oral anticoagulants (NOACs), which include dabigatran, apixaban, edoxaban and rivaroxaban, are preferred over vitamin K antagonists for stoke prevention in most patients with non-valvular atrial fibrillation. The NOACs are contraindicated in atrial fibrillation patients with rheumatic mitral stenosis or mechanical heart valves. There is evidence that bioprosthetic heart valves are less thrombogenic than mechanical heart valves, but it is unknown whether the risk of thromboembolism in atrial fibrillation patients with bioprosthetic valves differs from that in patients without such valves.

AREAS COVERED

The authors present a review of the efficacy and safety evidence surrounding the use of NOACs for stroke prevention in atrial fibrillation patients with bioprosthetic heart valves.

EXPERT COMMENTARY

While the data is limited, there is no significant difference in thromboembolic, and bleeding outcomes in patients with AF and bioprosthetic heart valves treated with NOAC therapy. Future studies are required before definitive conclusions can be drawn regarding the safety and efficacy of NOAC therapy in AF patients bioprosthetic heart valves.

Acute Presentation of Bioprosthetic Mitral Valve Thrombosis in a Patient on Venoarterial Extracorporeal Membranous Oxygenation

The management of patients presenting with bioprosthetic valve thrombosis presents a major clinical challenge from a diagnostic and management standpoint. This patient population becomes especially challenging to manage when presenting with cardiogenic shock and additional risks for bleeding. In this clinical conference, the authors present the case of a 64-year-old male who developed intraoperative bioprosthetic mitral valve thrombosis and cardiogenic shock necessitating support with venoarterial extracorporeal membrane oxygenation. The discussion focuses on the diagnostic challenges with transesophageal echocardiography and the difficulty in determining the proper approach to systemic anticoagulation.

Replacing the Anterior Mitral Valve Leaflet With Autologous Jugular Vein in a Sheep Model

BACKGROUND

This study evaluated the use of an autologous vein graft, supported by expanded polytetrafluoroethylene (ePTFE) chordae tendineae, to replace an anterior mitral valve leaflet.

METHODS

A double-layered autologous jugular vein graft, supported by ePTFE chords, was used to create an anterior mitral valve leaflet in 21 sheep. Mitral valve function was monitored with echocardiography for up to 10 months. Surviving sheep were euthanized between 6 and 10 months later, and vein implants were examined histologically.

RESULTS

One sheep died intraoperatively. Fourteen sheep had trace to mild mitral regurgitation (MR), 5 had mild to moderate MR, and 1 had moderate to severe MR. Ten sheep died between 2 days and 6.2 months. Echocardiography at 6 months showed MR progression in 8 of 11 sheep. The vein leaflet developed intimal fibroplasia and fibrous proliferation in response to the increased stress on the tissue, but the vein remained flexible without shortening or contracture. The 6- to 10-month vein implants showed viability with intact endothelium, myofibroblasts, collagen, and elastin. A normal healing pattern was seen at the suture lines, and no calcification was observed in the vein leaflet apart from the ePTFE sutures.

CONCLUSIONS

Autologous vein has the potential to function as a mitral valve leaflet substitute because it adapted morphologically and remained viable in the intracardiac position. Technical refinement in creating and implanting the leaflet is needed to improve the progression of MR.

Anticoagulation After Heart Valve Replacement or Transcatheter Valve Implantation

Valvular heart disease is prevalent and represents a significant contributor to cardiac morbidity and mortality. Several options for valve replacement exist, including surgical replacement and transcatheter valve implantation. Prosthetic valves lead to increased risk of thromboembolic disease; therefore, antithrombotic therapy after valve replacement is indicated. For patients with mechanical prostheses, indefinite vitamin K antagonist and antiplatelet therapy are the mainstays of treatment. There is no consensus regarding optimal antithrombotic therapy after bioprosthetic valve replacement, although vitamin K antagonist therapy of varying duration in addition to antiplatelet therapy is recommended by guidelines. Dual-antiplatelet therapy is commonly used after transcatheter valve implantation; however, alternative antithrombotic regimens are being studied. Further studies are needed to identify the optimal regimen, intensity, and duration of antithrombotic therapy after surgical bioprosthetic valve replacement and transcatheter valve implantation.

The echocardiography of replacement heart valves

This is a practical description of how replacement valves are assessed using echocardiography. Normal transthoracic appearances including normal variants are described. The problem of differentiating normal function, patient-prosthesis mismatch and pathological obstruction in aortic replacement valves with high gradients is discussed. Obstruction and abnormal regurgitation is described for valves in the aortic, mitral and right-sided positions and when to use echocardiography in suspected infective endocarditis. The roles of transoesophageal and stress echocardiography are described and finally when other imaging techniques may be useful.

Considerations and Recommendations for the Introduction of Objective Performance Criteria for Transcatheter Aortic Heart Valve Device Approval

In the United States, new surgical heart valves can be approved on the basis of objective performance criteria (OPC). In contrast, the US Food and Drug Administration traditionally requires stricter criteria for transcatheter heart valve (THV) approval, including randomized, clinical trials. Recent US Food and Drug Administration approval of new-generation THVs based on single-arm studies has generated interest in alternative study approaches for THV device approval. This review evaluates whether THV device approval could follow a pathway analogous to that of surgical heart valves by incorporating OPC and provides several considerations and recommendations. Factors to be taken into account in the construction of OPC include the maturity of THV technology, variability in transcatheter aortic valve replacement practice, end points included as OPC, follow-up terms for specific OPC, patient populations to which these OPC apply, and (statistical) methods for OPC development. We recommend that approval of THV devices in the United States for low- and intermediate-risk patients or for new indications should provisionally rely on data from randomized, clinical trials. However, it is recommended that formal OPC be applied for approval of new-generation THVs for use in high- and extreme-risk patient populations.

Contemporary outcomes after surgical aortic valve replacement with bioprostheses and allografts: a systematic review and meta-analysis

Many observational studies have reported outcomes after surgical aortic valve replacement (AVR), but there are no recent systematic reviews and meta-analyses including all available bioprostheses and allografts. The objective of this study is to provide a comprehensive and up-to-date overview of the outcomes after AVR with bioprostheses and allografts reported in the last 15 years. We conducted a systematic literature review (PROSPERO register: CRD42015017041) of studies published between 2000–15. Inclusion criteria were observational studies or randomized controlled trials reporting on outcomes of AVR with bioprostheses (stented or stentless) or allografts, with or without coronary artery bypass grafting (CABG) or valve repair procedure, with study population size n ≥ 30 and mean follow-up length ≥5 years. Fifty-four bioprosthesis studies and 14 allograft studies were included, encompassing 55 712 and 3872 patients and 349 840 and 32 419 patient-years, respectively. We pooled early mortality risk and linearized occurrence rates of valve-related events, reintervention and late mortality in a random-effects model. Sensitivity, meta-regression and subgroup analyses were performed to investigate the influence of outliers on the pooled estimates and to explore sources of heterogeneity. Funnel plots were used to investigate publication bias. Pooled early mortality risks for bioprostheses and allografts were 4.99% (95% confidence interval [CI], 4.44–5.62) and 5.03% (95% CI, 3.61–7.01), respectively. The late mortality rate was 5.70%/patient-year (95% CI, 4.99–5.62) for bioprostheses and 1.68%/patient-year (95% CI, 1.23–2.28) for allografts. Pooled reintervention rates for bioprostheses and allografts were 0.75%/patient-year (95% CI, 0.61–0.91) and 1.87%/patient-year (95% CI, 1.52–2.31), respectively. There was substantial heterogeneity in most outcomes. Meta-regression analyses identified covariates that could explain the heterogeneity: implantation period, valve type, patient age, gender, pre-intervention New York Heart Association class III/IV, concomitant CABG, study design and follow-up length. There is possible publication bias in all outcomes. This comprehensive systematic review and meta-analysis provides an overview of the outcomes after AVR with bioprostheses and allografts reported during the last 15 years. The results of this study can support patients and doctors in the prosthetic valve choice and can be used in microsimulation models to predict patient outcomes and estimate the cost-effectiveness of AVR with bioprostheses or allografts compared with current and future heart valve prostheses.

The effects of decellularization and cross-linking techniques on the fatigue life and calcification of mitral valve chordae tendineae

In cases of severely diseased mitral valves (MV), the required treatment is often valve replacement. Bioprosthetic and stentless replacement valves are usually either fully or partially composed of animal derived tissue treated with a decellularization process, a cross-linking process, or both. In this study, we analysed the effects of these treatments on the fatigue properties of porcine MV chordae tendineae (CT), as well as on the calcification of the CT using an in vitro technique. CT were tested in 4 groups; (1) native, (2) decellularized (DC), (3) decellularized and cross-linked with glutaraldehyde (DC-GTH), and (4) decellularized and cross-linked with 1-ehtyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)(DC-EDC). CT were tested in both uniaxial tension, and in fatigue at 10MPa peak stress (1Hz). The cycles to failure (mean±SD) for the four groups are as follows; Native- 53,397±55,798, DC- 28,013±30,634, DC-GTH- 97,665±133,556, DC-EDC- 318,601±322,358. DC-EDC CT were found to have a slightly longer fatigue life than the native and DC groups. The DC-EDC group also had a marginally lower dynamic creep rate, meaning those CT elongate more slowly. After in vitro calcification, X-ray microtomography was used to determine relative levels of calcification. The DC-EDC and DC-GTH groups had the lowest volume of calcific deposits. Under uniaxial testing, the ultimate tensile strength (UTS) of the DC-GTH CT was statistically significantly reduced after calcification, while the UTS was relatively unchanged for the DC-EDC group. Overall, these results indicate that a treatment of decellularization plus cross-linking with EDC may improve the fatigue life of porcine CT, reduce the rate of elongation, and help the CT resist the negative effects of calcification. This may be a preferable treatment in the preparation of porcine MVs for the replacement of diseased MVs.

3D velocity field characterization of prosthetic heart valve with two different valve testers by means of stereo-PIV

BACKGROUND

Prosthetic heart valves can be associated to mechanical loading of blood, potentially linked to complications (hemolysis and thrombogenicity) which can be clinically relevant. In order to test such devices in pulsatile mode, pulse duplicators (PDs) have been designed and built according to different concepts. This study was carried out to compare anemometric measurements made on the same prosthetic device, with two widely used PDs.

METHODS

The valve (a 27-mm bileaflet valve) was mounted in the aortic section of the PD. The Sheffield University PD and the RWTH Aachen PD were selected as physical models of the circulation. These two PDs differ mainly in the vertical vs horizontal realization, and in the ventricular section, which in the RWTH PD allows for storage of potential energy in the elastic walls of the ventricle. A glassblown aorta, realized according to the geometric data of the same anatomical district in healthy individuals, was positioned downstream of the valve, obtaining 1:1 geometric similarity conditions. A NaI-glycerol-water solution of suitable kinematic viscosity and, at the same time, the proper refractive index, was selected. The flow field downstream of the valve was measured by means of the stereo-PIV (Particle Image Velocimetry) technique, capable of providing the complete 3D velocity field as well as the entire Reynolds stress tensor. The measurements were carried out at the plane intersecting the valve axis.

RESULTS

A three-jet profile was clearly found in the plane crossing the leaflets, with both PDs. The extent of the typical recirculation zone in the Valsalva sinus was much larger in the RWTH PD, on account of the different duration of the swirling motion in the ventricular chamber, caused by the elasticity of the ventricle and its geometry.

CONCLUSION

The comparison of the hemodynamical behaviour of the same bileaflet valve tested in two PDs demonstrated the role of the mock loop in affecting the valve performance.

Prosthetic mitral valve obstruction: role of real-time three-dimensional transesophageal echocardiography in diagnosis

Acute prosthetic valve thrombosis is a potentially serious complication with an incidence as high as 6% per patient-year for prostheses in the mitral position. Accurate diagnosis of the degree of obstruction and differentiation of pannus versus thrombus is critical in determination of the best mode of therapy. We discuss a case of a patient with multiple comorbidities who presented with mechanical mitral valve obstruction where both transthoracic and two-dimensional transesophageal echocardiography (TEE) were limited in making an accurate diagnosis regarding the mechanism of obstruction. Real-time 3D-TEE (RT-3DTEE) was critical in identifying a partial thrombus on the mechanical valve and guided the choice of thrombolysis as the most appropriate intervention, thus avoiding high-risk surgery in this patient with significant multiple comorbidities.

Efficacy and safety of novel oral anticoagulants in patients with bioprosthetic valves

PURPOSE

Prosthetic valve replacement is performed in several hundred thousand patients worldwide annually, and many of these patients have or will ultimately develop atrial fibrillation or flutter (AF). Novel oral anticoagulants (NOACs) are not recommended in patients with AF and mechanical valves but have not been evaluated in patients with bioprosthetic valves. This study sought to evaluate the efficacy and safety of NOACs in patients with AF and bioprosthetic valves.

METHODS

A retrospective single-center cohort study was performed on all patients with bioprosthetic valve implantation, for whom a NOAC was prescribed for the indication of AF. Patients were evaluated for thromboembolic events including imaging confirmed ischemic stroke, clinically suspected transient ischemic attack, and major bleeding events (according to International Society on Thrombosis and Hemostasis definition).

RESULTS

In total, 73 patients (26 female, 35.6 %) were identified. NOAC therapy began, on average, 990.0 ± 1029.1 days after bioprosthetic valve implantation for an average duration of 511.8 ± 400.8 days. Aspirin was used concomitantly in a majority of patients (72.6 %). There were no ischemic strokes identified (0.0 %) and one possible TIA (1.4 %). There were 6 (8.2 %) minor and 5 (6.9 %) major bleeding events.

CONCLUSION

The use of NOAC therapy for AF in patients with bioprosthetic valves appears safe and effective in the occurrence of thromboembolic events, however, at the expense of increased bleeding. Larger studies are necessary to confirm these findings.

How to define valvular atrial fibrillation?

Atrial fibrillation (AF) confers a substantial risk of stroke. Recent trials comparing vitamin K antagonists (VKAs) with non-vitamin K antagonist oral anticoagulants (NOACs) in AF were performed among patients with so-called "non-valvular" AF. The distinction between "valvular" and "non-valvular" AF remains a matter of debate. Currently, "valvular AF" refers to patients with mitral stenosis or artificial heart valves (and valve repair in North American guidelines only), and should be treated with VKAs. Valvular heart diseases, such as mitral regurgitation, aortic stenosis (AS) and aortic insufficiency, do not result in conditions of low flow in the left atrium, and do not apparently increase the risk of thromboembolism brought by AF. Post-hoc analyses suggest that these conditions probably do not make the thromboembolic risk less responsive to NOACs compared with most forms of "non-valvular" AF. The pathogenesis of thrombosis is probably different for blood coming into contact with a mechanical prosthetic valve compared with what occurs in most other forms of AF. This may explain the results of the only trial performed with a NOAC in patients with a mechanical prosthetic valve (only a few of whom had AF), where warfarin was more effective and safer than dabigatran. By contrast, AF in the presence of a bioprosthetic heart valve or after valve repair appears to have a risk of thromboembolism that is not markedly different from other forms of "non-valvular" AF. Obviously, we should no longer consider the classification of AF as "valvular" (or not) for the purpose of defining the aetiology of the arrhythmia, but for the determination of a different risk of thromboembolic events and the need for a specific antithrombotic strategy. As long as there is no better new term or widely accepted definition, "valvular AF" refers to patients with mitral stenosis or artificial heart valves. Patients with "non-valvular AF" may have other types of valvular heart disease. One should emphasize that "non-valvular AF" does not exclude patients with some types of valvular heart disease from therapy with NOACs.

Endothelial retention and phenotype on carbonized cardiovascular implant surfaces

Heart valve disease is an increasing clinical burden for which there is no effective treatment outside of prosthetic replacement. Over the last 20 years, clinicians have increasingly preferred the use of biological prosthetics to mechanical valves despite their superior durability because of the lifelong anticoagulation therapy that is required. Mechanical valve surface engineering has largely focused on being as non-thrombogenic as possible, but despite decades of iteration has had insufficient impact on the anticoagulation burden. In this study, we systematically evaluate the potential for endothelialization of the pyrolytic carbon surface used in mechanical valves. We compared adsorbed adhesion ligand type (collagen I, fibronectin, laminin, and purified adhesion domain fragments GFOGER and FN7-10) and concentration on endothelial adhesion rates and adhesion strength on Medtronic-Hall prosthetic valve surfaces. Regardless of ligand type or concentration, endothelial adhesion strengthening was insufficient for their intended ultra-high shear stress environment. We then hypothesized that microfabricated trenches would reduce shear stress to tolerable levels while maintaining endothelial access to the flow stream, thereby promoting a confluent and anticoagulant endothelial monolayer. Computational fluid dynamics simulations predicted an empirical relationship of channel width, depth, and spacing that would maintain interior surface shear stress within tolerable levels. Endothelial cells seeded to confluence in these channels retained a confluent monolayer when exposed to 600 dyn/cm(2) shear stress for 48 h regardless of applied adhesive ligand. Furthermore, sheared EC expressed a mature anti-coagulant profile, including endothelial nitric oxide synthase (eNOS), VE-cadherin, and significantly downregulated plasminogen activator inhibitor-1 (PAI-1). As a final test, channeled pyrolytic carbon surfaces with confluent EC reduced human platelet adhesion 1000-fold over pyrolytic carbon alone. These results advance a promising biohybrid approach to enable active moderation of local coagulative response in mechanical heart valves, which could significantly extend the utility of this important treatment for heart valve disease.

Neurologic complications of valvular heart disease

Valvular heart disease (VHD) is frequently associated with neurologic complications; cerebral embolism is the most common of these since thrombus formation results from the abnormalities in the valvular surfaces or from the anatomic and physiologic changes associated with valve dysfunction, such as atrial or ventricular enlargement, intracardiac thrombi, and cardiac dysrhythmias. Prosthetic heart valves, particularly mechanical valves, are very thrombogenic, which explains the high risk of thromboembolism and the need for anticoagulation for the prevention of embolism. Infective endocarditis is a disease process with protean manifestations that include not only cerebral embolism but also intracranial hemorrhage, mycotic aneurysms, and systemic manifestations such as fever and encephalopathy. Other neurologic complications include nonbacterial thrombotic endocarditis, a process associated with systemic diseases such as cancer and systemic lupus erythematosus. For many of these conditions, anticoagulation is the mainstay of treatment to prevent cerebral embolism, therefore it is the potential complications of anticoagulation that can explain other neurologic complications in patients with VHD. The prevention and management of these complications requires an understanding of their natural history in order to balance the risks posed by valvular disease itself against the risks and benefits associated with treatment.

Thirty-year results after implantation of the Björk-Shiley Convexo-Concave Heart valve prosthesis

BACKGROUND

Modifications of the Björk-Shiley valve prosthesis have shown good long-term results. The convexo-concave model, however, was recalled 27 years ago because of a propensity for breakage due to outlet strut fracture. The objective of this study is to describe the 30-year outcome after implantation of the Björk-Shiley convexo-concave mechanical heart valve prosthesis (Pfizer, Rye Brook, NY).

METHODS

The study included 279 patients who were operated between 1979 and 1983 at Turku University Hospital. A total of 305 valves were implanted; 205 in the aortic position and 100 in the mitral position. Patient records were reviewed for baseline characteristics and late events, data on mortality were acquired from registries.

RESULTS

Mean actuarial survival was 19.8 years and mean follow-up was 19.2 years (maximum 34 years). Freedom from reoperation was 91.3% at 30 years. There were 3 outlet strut fractures (2 fatal) during follow-up. Statistically significant predictors of mortality were age and concomitant coronary artery bypass grafting.

CONCLUSIONS

Despite the possibility of structural valve failure the Björk-Shiley convexo-concave valve confers excellent 30-year survival.

Prosthetic heart valve obstruction: thrombolysis or surgical treatment?

Prosthetic valve thrombosis is a potentially life-threatening complication associated with high morbidity and mortality. Transthorasic and transoesophageal echocardiography play an important role to the diagnosis and provides incremental information about the optimal treatment strategy, while fluoroscopy and cardiac computed tomography may be of added value. Guidelines differ on whether surgical treatment or fibrinolysis should be the treatment of choice for the management of left-sided prosthetic valve thrombosis and these uncertainties underline the need for further prospective randomized controlled trials. Thrombus size, New York Heart Association functional class of the patient, the possible contraindications, the availability of each therapeutic option and the clinician's experience are important determinants for the management of prosthetic valve thrombosis.

Long-term safety and effectiveness of mechanical versus biologic aortic valve prostheses in older patients: results from the Society of Thoracic Surgeons Adult Cardiac Surgery National Database

BACKGROUND

There is a paucity of long-term data comparing biological versus mechanical aortic valve prostheses in older individuals.

METHODS AND RESULTS

We performed follow-up of patients aged 65 to 80 years undergoing aortic valve replacement with a biological (n=24 410) or mechanical (n=14 789) prosthesis from 1991 to 1999 at 605 centers within the Society of Thoracic Surgeons Adult Cardiac Surgery Database using Medicare inpatient claims (mean, 12.6 years; maximum, 17 years; minimum, 8 years), and outcomes were compared by propensity methods. Among Medicare-linked patients undergoing aortic valve replacement (mean age, 73 years), both reoperation (4.0%) and endocarditis (1.9%) were uncommon to 12 years; however, the risk for other adverse outcomes was high, including death (66.5%), stroke (14.1%), and bleeding (17.9%). Compared with those receiving a mechanical valve, patients given a bioprosthesis had a similar adjusted risk for death (hazard ratio, 1.04; 95% confidence interval, 1.01-1.07), higher risks for reoperation (hazard ratio, 2.55; 95% confidence interval, 2.14-3.03) and endocarditis (hazard ratio, 1.60; 95% confidence interval, 1.31-1.94), and lower risks for stroke (hazard ratio, 0.87; 95% confidence interval, 0.82-0.93) and bleeding (hazard ratio, 0.66; 95% confidence interval, 0.62-0.70). Although these results were generally consistent among patient subgroups, bioprosthesis patients aged 65 to 69 years had a substantially elevated 12-year absolute risk of reoperation (10.5%).

CONCLUSIONS

Among patients undergoing aortic valve replacement, long-term mortality rates were similar for those who received bioprosthetic versus mechanical valves. Bioprostheses were associated with a higher long-term risk of reoperation and endocarditis but a lower risk of stroke and hemorrhage. These risks varied as a function of a patient's age and comorbidities.