Mechanical Valve Research Articles

Effect of the ex situ physical and in situ chemical modification of bacterial nanocellulose on mechanical properties in the context of its potential applications in heart valve design

Bacterial nanocellulose (BNC) is a promising material for heart valve prostheses. However, its low strength properties limit its applicability in cardiovascular surgery. To overcome these limitations, the mechanical properties of BNC can be improved through modifications. The aim of the research was to investigate the extent to which the mechanical properties of BNC can be altered by modifying its structure during its production and after synthesis. The study presents the results of various analyses, including tensile tests, nanoindentation tests, X-ray diffraction (XRD) tests, scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy, conducted on BNC chemically modified in situ with hyaluronic acid (BNC/HA) and physically modified ex situ through a dehydration/rehydration process (BNC 25DR, BNC105DR, BNC FDR and BNC/HA 25DR, BNC/HA 105DR, BNC/HA FDR). The results demonstrate that both chemical and physical modifications can effectively shape the mechanical properties of BNC. These modifications induce changes in the crystalline structure, pore size and distribution, and residual stresses of BNC. Results show the effect of the crystalline structure of BNC on its mechanical properties. There is correlation between hardness and Young's modulus and Iα/Iβ index for BNC/HA and between creep rate of BNC/HA, and Young's modulus for BNC vs Iα/Iβ index.

The Melody Valve in Small Children Undergoing First Mitral Valve Replacement: Better Than Mechanical?

BackgroundIn small children with left atrioventricular valve dysfunction, valve repair is preferred but some will require valve replacement. No prosthetic valve has growth potential, bioprostheses have poor durability, and mechanical prostheses have high rates of thromboembolic and hemorrhagic complications. We reviewed our experience with a modified bovine jugular vein valve designed for use in the right ventricular outflow tract (Melody valve, Medtronic) and compared this with contemporary mechanical valve replacement. MethodsWe reviewed outcomes of all left-sided atrioventricular valve replacements (AVVR) performed between January 2017 and April 2023 on patients with biventricular circulation less than 5 years old at time of surgery, N = 19. We compared mortality and major morbidity outcomes between mechanical AVVR (mAVVR, n = 14) and Melody AVVR (MAVVR, n=5). ResultsMAVVR was performed on younger and smaller patients (5.7 ± 4.2 vs 28.4 ± 22.3 months, P = .002; 6 ± 1.7 vs10 ± 5.1 kg, P = .01). There were 2 early and 1 late death in the mAVVR group, and none in the MAVVR group. There was a trend towards more hemorrhagic and neurologic complications in the mAVVR group (P = .1, 0.28, respectively). ConclusionsIn this small series, despite its use in younger and smaller patients, our preliminary experience with the Melody valve compares favorably with our contemporaneous outcomes with mechanical prostheses by way of simpler anticoagulation management with a trend towards better overall outcomes.

Antithrombotic therapy after heart valve surgery: contemporary practice in the UK.

There is a lack of high-quality data informing the optimal antithrombotic drug strategy following bioprosthetic heart valve replacement or valve repair. Disparity in recommendations from international guidelines reflects this. This study aimed to document current patterns of antithrombotic prescribing after heart valve surgery in the UK. All UK consultant cardiac surgeons were e-mailed a custom-designed survey. The use of oral anticoagulant (OAC) and/or antiplatelet drugs following bioprosthetic aortic valve replacement or mitral valve replacement, or mitral valve repair (MVrep), for patients in sinus rhythm, without additional indications for antithrombotic medication, was assessed. Additionally, we evaluated anticoagulant choice following MVrep in patients with atrial fibrillation. We identified 260 UK consultant cardiac surgeons from 36 units, of whom 103 (40%) responded, with 33 units (92%) having at least 1 respondent. The greatest consensus was for patients undergoing bioprosthetic aortic valve replacement, in which 76% of surgeons favour initial antiplatelet therapy and 53% prescribe lifelong treatment. Only 8% recommend initial OAC. After bioprosthetic mitral valve replacement, 48% of surgeons use an initial OAC strategy (versus 42% antiplatelet), with 66% subsequently prescribing lifelong antiplatelet therapy. After MVrep, recommendations were lifelong antiplatelet agent alone (34%) or following 3 months OAC (20%), no antithrombotic agent (20%), or 3 months OAC (16%). After MVrep for patients with established atrial fibrillation, surgeons recommend warfarin (38%), a direct oral anticoagulant (37%) or have no preference between the 2 (25%). There is considerable variation in the use of antithrombotic drugs after heart valve surgery in the UK and a lack of high-quality evidence to guide practice, underscoring the need for randomized studies.

Advances in warfarin's anticoagulation therapy in Chinese population after mechanical valve replacement

Warfarin is an irreplaceable oral anticoagulant for patients with mechanical heart valves, the stable pharmacogenetic-based warfarin dose prediction algorithms have improved the effectiveness and safety of warfarin anticoagulation therapy. Genetic factors are the main factors affecting the stable dose of warfarin. Single nucleotide polymorphisms such as VKORC1 and CYP2C9 affect the anticoagulation effect of warfarin through pharmacodynamic or pharmacokinetic pathways. Age, body surface area, combined use of drugs, and other nongenetic factors also affect the stable dose of warfarin. Previously published algorithms for warfarin dose prediction included mainly the white race, and most algorithms were constructed using traditional multiple linear regression. However, domestic studies have used machine learning methods to construct warfarin dose prediction algorithms based on the Chinese Han post-mechanical valve replacement population and have achieved better prediction efficiency. This article reviews the advances of warfarin anticoagulation influencing factors and the clinical application of stable dose prediction algorithms.

An in-Depth Examination Modalities of Hemodynamic Characteristics in Mechanical Aortic Valve: A Comprehensive Review Article

The assessment of prosthetic aortic valves through echocardiography, a pivotal noninvasive tool, encounters challenges, with discordant findings compared to invasive measurements, particularly in transvalvular gradients. To address these complexities, this comprehensive review article explores diverse methodologies and modalities for assessing prosthetic aortic valve performance. As these life-saving devices advance in complexity, the demand for precise and innovative assessment techniques intensifies. This journey through established and emerging modalities aims to inform clinical practice, foster experimental innovation, and enhance patient care in the realm of aortic valve prosthetic assessment. Ultimately, a profound understanding of the hemodynamic milieu engendered by aortic prosthetic valves serves as the cornerstone for optimizing valve design and clinical utility. The primary objective of this comprehensive review is to elucidate, with utmost precision, the multifaceted methodologies employed in the investigation and evaluation of mechanical prosthetic aortic valve.

Perioperative stroke after aortic valve replacement for aortic stenosis - incidence, risk factors and short-term outcome

One of the most serious complications of surgical aortic valve replacement (SAVR) is stroke that can result in increased rates of complications, morbidity and mortality postoperatively. The aim of this study was to investigate incidence, risk factors and short-term outcome in a well defined cohort of SAVR-patients. A retrospective study on 740 consecutive aortic stenosis patients who underwent SAVR in Iceland 2002-2019. Patients with stroke were compared with non-stroke patients; including preoperative risk factors of cardiovascular disease, echocardiogram-results, rate of early postoperative complications other than stroke and 30 day mortality. Mean age was 71 yrs (34% females) with 57% of the patients receiving stented bioprosthesis, 31% a stentless Freestyle®-valve and 12% a mechanical valve. Mean EuroSCORE-II was 3.6, with a maximum preop-gradient of 70 mmHg and an estimated valvular area of 0.73 cm2. Thirteen (1.8%) patients were diagnosed with stroke where hemiplegia (n=9), loss of consciousness (n=3) and/or aphasia (n=4) were the most common presenting symptoms. In 70% of cases the neurological symptoms resolved or disappeared in the first weeks and months after surgery. Only one patient out of 13 died within 30-days (7.7%). Stroke-patients had significantly lower BMI than non-stroke patients, but other risk factors of cardiovascular diseases, intraoperative factors or the rate of other severe postoperative complications than stroke were similar between groups. Total length of stay was 14 days vs. 10 days median, including 2 vs. 1 days in the ICU, in the stroke and non-stroke-groups, respectively. The rate of stroke after SAVR was low (1.8%) and in line with other similar studies. Although a severe complication, most patients with perioperative stroke survived 30 days postoperatively and in majority of cases neurological symptoms recovered.

Technical exploration and early results of two-port total thoracoscopic aortic-mitral double-valve replacement

Objective: To examine the clinical outcomes of patients undergoing total thoracoscopic aortic-mitral double-valve replacement. Methods: This is a retrospective case series study. The clinical data of 50 patients who underwent double-valve replacement under a total thoracoscopic two-port approach from November 2021 to August 2022 in the Department of Cardiovascular Surgery, Fujian Medical University Union Hospital were retrospectively analyzed. There were 32 males and 18 females, with an age of (55.3±8.8) years (range: 21 to 62 years). Among them, 36 cases had rheumatic heart disease and 14 cases had infective endocarditis. The 3rd intercostal space between the right anterior axillary line and the midclavicular line was selected as the main operating hole, the total thoracoscopic double-valve replacement were successfully carried out. Baseline data, intraoperative information, surgical outcomes, and postoperative complications were collected for all patients. Results: The cardiopulmonary bypass time was (168.2±30.9) minutes (range: 125 to 187 minutes), the aortic cross-clamping time was (118.8±16.5) minutes (range: 96 to 147 minutes). Five patients received bioprosthetic valves, and 45 received mechanical prosthetic valves. Postoperative mechanical ventilation lasted (9.6±3.4) hours (range: 5.1 to 14.2 hours), the ICU stay was (24.8±7.3) hours (range: 16.3 to 30.1 hours), and the postoperative hospital stay was (6.5±1.2) days (range: 5.0 to 8.0 days). Four patients received red blood cell transfusions of (2.7±0.9) units (range: 2 to 4 units), and the postoperative chest drainage volume was (222.1±56.3) ml (range: 175 to 289 ml). No deaths occurred intraoperatively or in the early postoperative period. One patient required reoperation due to bleeding in the aortic incision. Three patients had mild to moderate paravalvular leakage around the prosthetic aortic valve, with no cases of third-degree atrioventricular block or conversions to median sternotomy. Conclusions: The early outcomes of total thoracoscopic double valve replacement surgery are satisfactory, demonstrating safety and efficacy. This surgical approach expands the scope of total thoracoscopic cardiac surgery, which warrants further investigation and research.

A wall-modeled immersed boundary/large eddy simulation method and its application to simulating heart valve flows

In this work, a wall-modeled immersed boundary (IB)/large eddy simulation (LES) method is extended to the simulation of moving-boundary flows. The used non-equilibrium algebraic wall model is based on an assumed velocity profile, the coefficients of which are determined from physical constraints provided by the full turbulent-boundary-layer equations. To implement the wall model in an IB method named the local domain-free discretization (DFD) method, a local coordinate system fixed on the moving body is introduced. Thus, wall modeling is transformed into a local two-dimensional problem and the complexity of implementation of the wall model is reduced. In the present LES-DFD method, the tangential velocity at an exterior dependent node is determined via wall shear stress prescribed by the wall model. To reduce computational cost for simulating an internal flow with moving boundaries, the stationary boundaries are handled by the body-fitted-grid method and the moving boundaries by the local DFD method. There is no need of an auxiliary grid for solving the non-equilibrium algebraic wall model. Therefore, the inbuilt advantage of an IB method can be retained when simulating moving-boundary problems, and the economy of equilibrium wall models can also be preserved. The present method is applied to simulating the pulsatile flows through a bileaflet mechanical heart valve implanted in a model aorta. The predicted results show an acceptable agreement with the referenced experimental measurements or numerical results at much higher resolution and the applicability of the non-equilibrium wall model to LES of complex moving-boundary flows is verified.

Effective orifice diameter: a new sizing parameter of surgical valve prostheses to inform valve selection.

The labeled sizes of surgical valve prostheses and their discordance with the physical internal valve orifice sizes has long been a controversy in the cardiac surgery community, leading many to believe it to be a contributing factor in prosthesis-patient mismatch following valvular replacement surgery. In an attempt to address this issue, the International Organization for Standardization (ISO) 5840-2:2021 standard for surgical valve prostheses recommends that a new sizing parameter, namely, the effective orifice diameter, be provided in labeling by all manufacturers as an indicator of the true flow-passing capacity of a prosthetic valve. The ISO Cardiac Valves Working Group conducted a multi-laboratory round-robin study to investigate whether the effective orifice diameter of a prosthetic surgical valve could be derived repeatably and reproducibly through steady forward-flow testing. A total of seven valve models, each with multiple sizes, were tested, including a mechanical heart valve and multiple biological heart valves. The round-robin study confirmed that the steady forward-flow test had good intra-laboratory repeatability and inter-laboratory reproducibility in deriving the effective orifice diameters of surgical valve prostheses. On average, among the participating laboratories, the experimentally derived effective orifice diameter of a prosthetic heart valve was 3-12 mm smaller than its labeled size. The effective orifice diameter provides better characterization of the hydrodynamic characteristics of a surgical valve prosthesis and can be derived using a validated steady forward-flow test method. This new sizing parameter will soon be adopted by surgical valve manufacturers and provided in device labeling to inform valve selection by surgeons.

Pregnancy Outcomes in Patients with Prosthetic Heart Valves in Saudi Arabia

Background: Pregnancies in women with heart prostheses are high-risk pregnancies with increased maternal and fetal adverse outcomes. Advances in prosthetic heart valve design and anticoagulation have improved these outcomes over the past decades. Objectives: To study the pregnancy outcomes in pregnancies with heart prostheses and to compare these outcomes between mechanical and biosynthetic heart prostheses in Saudi patients. Methods: In this single centered retrospective study conducted at King Saud Medical City (KSUMC) between January 2011 and February 2020, we have reviewed all pregnant women’s heart prostheses. Fetal and maternal data were obtained, and outcomes were compared between pregnancies with mechanical heart prostheses and bioprostheses. Results: A total of 111 pregnancies were reviewed. A total of 51.4% of pregnancies had bioprostheses, 48.6% had mechanical prostheses, and 64.0% of participants were obese. The majority of the participants had a parity in the range of 2-9 (N=107, 96.4%). The most frequent type of rheumatic heart disease was mitral regurgitation (N=49, 44.1%), followed by mitral stenosis (N=32, 28.8%). There was no maternal mortality and no structural valve failure. There was a high rate of hospital admission in both groups, up to 55% of pregnancies. The rates of abortion, postpartum hemorrhage and transfusions were higher than those in general pregnancies; however, there was no difference in maternal and fetal complications between the two types of prostheses, i.e., bioprostheses and mechanical. Conclusion: Although women with prosthetic heart valves have higher rates of adverse outcomes, they generally tolerate pregnancy well. There was no difference in adverse outcomes between bioprosthetic and mechanical prostheses

Case report on Pharmacogenetic guided warfarin dosing in a postoperative valve replacement patient

Patient underwent mitral valve replacement with mechanical valve and was initiated on oral anticoagulation with standard dose of warfarin. She developed supra therapeutic INR levels. Genotyping of CYP2C9 and VKORC1 encoding genes revealed homozygous variation of CYP2C9*3*3 and heterozygous variation of VKORC1 G>A making her hypersensitive to warfarin. Based on this study result and Clinical Pharmacogenetics Implementation Consortium (CPIC) guideline, a low dose of warfarin (0.5mg per day) was prescribed, to achieve a therapeutic INR of 2.5 to 3.5 and adverse drug effects were avoided.

Vision–language foundation model for echocardiogram interpretation

The development of robust artificial intelligence models for echocardiography has been limited by the availability of annotated clinical data. Here, to address this challenge and improve the performance of cardiac imaging models, we developed EchoCLIP, a vision–language foundation model for echocardiography, that learns the relationship between cardiac ultrasound images and the interpretations of expert cardiologists across a wide range of patients and indications for imaging. After training on 1,032,975 cardiac ultrasound videos and corresponding expert text, EchoCLIP performs well on a diverse range of benchmarks for cardiac image interpretation, despite not having been explicitly trained for individual interpretation tasks. EchoCLIP can assess cardiac function (mean absolute error of 7.1% when predicting left ventricular ejection fraction in an external validation dataset) and identify implanted intracardiac devices (area under the curve (AUC) of 0.84, 0.92 and 0.97 for pacemakers, percutaneous mitral valve repair and artificial aortic valves, respectively). We also developed a long-context variant (EchoCLIP-R) using a custom tokenizer based on common echocardiography concepts. EchoCLIP-R accurately identified unique patients across multiple videos (AUC of 0.86), identified clinical transitions such as heart transplants (AUC of 0.79) and cardiac surgery (AUC 0.77) and enabled robust image-to-text search (mean cross-modal retrieval rank in the top 1% of candidate text reports). These capabilities represent a substantial step toward understanding and applying foundation models in cardiovascular imaging for preliminary interpretation of echocardiographic findings.

Trileaflet Mechanical Valves: What Is Already Known? A Systematic Review

Background: Trileaflet mechanical valves were introduced in the late 90’s. Despite promising results, none have made it past preclinical testing. Ample in vitro, in vivo and computational testing have already been done. Methods: This systematic review is intended to summarize all available preclinical and clinical testing regarding trileaflet mechanical valves. A literature search of Pubmed, Embase and Web of Science (Core Collection) (from inception to August 2023) was performed using a search string that was well defined and not modified during the study. An extensive overview of the search terms used in each database can be found in the appendix. 24 publications were included in this review. Results: This systematic review serves as an overview evaluating the rationale behind a trileaflet mechanical valve as well as the computational, in vitro and in vivo testing. We aim to summarize all available knowledge on trileaflet mechanical valves. Conclusions: A trileaflet mechanical valve is a promising concept, with equal or even superior hemodynamics compared to conventional bileaflet valves based on computational, in vivo and in vitro data. First in men trials are warranted to elude the true potential of this design.

Choice of valve substitutes.

Infective endocarditis often necessitates surgical intervention, and the choice of valve substitute remains a topic of controversy and highly debatable due to the wide range of available options and recent technical advancements. This manuscript reviews the different valve substitutes in the context of infective endocarditis, including mechanical and bioprosthetic valves, homografts, xenografts, and tissue-engineered valves. The patient's age, sex, demographic location, intellectual quotient, comorbidities, available options, and the experience of the surgeon should all be taken into consideration while choosing the best valve substitute for that individual. While valve repair and reconstruction are preferred whenever feasible, valve replacement may be the only option in certain cases. The choice between mechanical and bioprosthetic valves should be guided by standard criteria such as age, sex, expected lifespan, associated comorbidities, and anticipated adherence to anticoagulation therapy and accessibility of medical facilities for follow-up. For patients with severe chronic illness or a history of intracranial bleeding or associated hematological disorders, the use of mechanical prostheses may be avoided. Homografts and bioprosthetic valves provide an alternative to mechanical valves, thereby decreasing the necessity for lifelong anticoagulation after surgery and diminishing the likelihood of bleeding complications. The manuscript also discusses specific valve substitutes for different heart valves (aortic, mitral, pulmonary, tricuspid positions) and highlights emerging techniques such as the aortic valve neocuspidization (Ozaki procedure) and tissue-engineered valves. Ultimately, the ideal valve substitute in IE should be evidence based on a comprehensive elucidation of clinical condition of the patient and available options.

Influence of time in therapeutic range on postoperative complications in mechanical heart valve replacement patients operated with the indigenous TTK Chitra heart valve

Influence of time in therapeutic range on postoperative complications in mechanical heart valve replacement patients operated with the indigenous TTK Chitra heart valve

Dementia Development during Long-Term Follow-Up after Surgical Aortic Valve Replacement with a Biological Prosthesis in a Geriatric Population.

Surgical aortic valve replacement (SAVR) with a biological heart valve prosthesis (BHV) is often used as a treatment in elderly patients with symptomatic aortic valve disease. This age group is also at risk for the development of dementia in the years following SAVR. The research question is "what are the predictors for the development of dementia?". In 1500 patients undergoing SAVR with or without an associated procedure, preoperative (demographic, cardiac and non-cardiac comorbid conditions), perioperative (associated procedures, cross-clamp and cardiopulmonary bypass time) and postoperative 30-day adverse events (bleeding, thromboembolism, heart failure, conduction defects, arrhythmias, delirium, renal and pulmonary complications) were investigated for their effect on the occurrence of dementia by univariate analyses. Significant factors were entered in a multivariate analysis. The sum of the individual follow-up of the patients was 10,182 patient-years, with a mean follow-up of 6.8 years. Data for the development of dementia could be obtained in 1233 of the 1406 patients who left the hospital alive. Dementia during long-term follow-up developed in 216/1233 (17.2%) of the patients at 70 ± 37 months. Development of dementia reduced the mean survival from 123 (119-128) to 109 (102-116) months (p < 0.001). Postoperative delirium was the dominant predictor (OR = 3.55 with a 95%CI of 2.41-4.93; p < 0.00), followed by age > 80 years (2.38; 1.78-3.18; p < 0.001); preoperative atrial fibrillation (1.47; 1.07-2.01; p = 0.018); cardiopulmonary bypass time > 120 min (1.34; 1.02-1.78; p = 0.039) and postoperative thromboembolism (1.94; 1.02-3.70; p = 0.044). Postoperative delirium, as a marker for poor condition, and an age of 80 or more were the dominant predictors.

Клапанозбережне протезування кореня аорти: результати операції Девіда І

The aim – to determine the long-term results and quality of life of patients who underwent David І valve-sparing operation.Materials and methods. The one-center study included 53 patients who underwent planned and urgent David I procedure (valve-sparing replacement of the aortic root and ascending aorta) from 2015 to 2023. The mean age of the 53 patients (among them, 47 (88.68 %) males) was 49.11 ± 1.54 years. We analyzed basic characteristics of the patients, intraoperative and postoperative data. The quality of life was assessed before and in the long-term period after operations by the Medical Outcomes Study Short Form 36 (MOS SF-36) questionnaire.Results and discussion. An average duration of the follow-up period was 2.59 ± 0.27 years ranging from 1.0 to 9.0 years. Overall in-hospital mortality and 30-day mortality was 1.89 % (n 1). Estimated 5-year survival rate was 95.7 ± 1.45 % for all patients. The average duration of the operations was 291.23 ± 12.67 minutes, the total duration of artificial blood circulation was 170.28 ± 8.77 minutes, aorta clamping time – 122.02 ± 5.92 minutes. The mean duration of stay in the hospital was 13.81 ± 0.54 days, intensive care unit – 2.94 ± 0.03 days. The number of patients extubated up to 8 hours after surgery was 48 patients (90.57 %). The performed operation significantly improved the indicators. Patients positively perceived the information about the absence of an artificial heart valve and need of concomitant use of anticoagulants. The patients had a good psycho-social component, which probably affected the assessment of other scales.Conclusions. Patients after David I operation have a low overall in-hospital mortality and 30-day mortality, with a short period of time in intensive care unit and hospital at all. Long-term results in indicator of 5-year survival are excellent. The operation significantly improves quality of life parameters.

Aspirin hypersensitivity: a practical guide for cardiologists.

Aspirin has been known for a long time and currently stays as a cornerstone of antithrombotic therapy in cardiovascular disease. In patients with either acute or chronic coronary syndromes undergoing percutaneous coronary intervention aspirin is mandatory in a dual antiplatelet therapy regimen for prevention of stent thrombosis and/or new ischaemic events. Aspirin is also currently a first-option antithrombotic therapy after an aortic prosthetic valve replacement and is occasionally required in addition to oral anticoagulants after implantation of a mechanical valve. Presumed or demonstrated aspirin hypersensitivity is a main clinical problem, limiting the use of a life-saving medication. In the general population, aspirin hypersensitivity has a prevalence of 0.6%-2.5% and has a plethora of clinical presentations, ranging from aspirin-exacerbated respiratory disease to anaphylaxis. Although infrequent, when encountered in clinical practice aspirin hypersensitivity poses for cardiologists a clinical dilemma, which should never be trivialized, avoiding-as much as possible-omission of the drug. We here review the epidemiology of aspirin hypersensitivity, provide an outline of pathophysiological mechanisms and clinical presentations, and review management options, starting from a characterization of true aspirin allergy-in contrast to intolerance-to suggestion of desensitization protocols.

Instability mechanisms initiating laminar–turbulent transition past bioprosthetic aortic valves

Bioprosthetic heart valves create turbulent flow during early systole which might be detrimental to their durability and performance. Complex mechanisms in the unsteady and heterogeneous flow field complicate the isolation of specific instability mechanisms. We use linear stability analysis and numerical simulations of the flow in a simplified model to study mechanisms initiating the laminar–turbulent transition. The analysis of a modified Orr–Sommerfeld equation, which includes a model for fluid–structure interaction (FSI), indicates Kelvin–Helmholtz and FSI instabilities for a physiological Reynolds number regime. Two-dimensional parametrized FSI simulations confirm the growth rates and phase speeds of these instabilities. The eigenmodes associated with the observed leaflet kinematics allow for decoupled leaflet oscillations. A detailed analysis of the temporal evolution of the flow field shows that the starting vortex interacts with the aortic wall leading to a secondary vortex which moves towards the shear layer in the wake of the leaflets. This appears to be connected to the onset of the shear layer instabilities that are followed by the onset of leaflet motion leading to large-scale vortex shedding and eventually to a nonlinear breakdown of the flow. Numerical results further indicate that a narrower aorta leads to an earlier onset of the shear layer instabilities. They also suggest that the growing perturbations of the shear layer instability propagate upstream and may initiate the FSI instabilities on the valve leaflets.

CoaguChek and Coag-Sense PT2 Meter Point of Care INR Device Validation

ObjectiveTo standardize international normalized ratio (INR) measurements and improve data integrity by enabling electronic result transmission for warfarin monitoring, two point-of-care (POC) devices were evaluated against an internal plasma INR reference method. MethodsA multicenter study was pursued (January 24, 2022, through October 19, 2022) to compare concordance of two commercially available POC devices, Coag-Sense PT2 Meter (Coag-Sense) and CoaguChek XS Pro and Plus devices (CoaguChek), against an internal plasma INR method among patients treated with warfarin. Bias and linear regression analysis were assessed for these devices including dosing decision accuracy compared with plasma INR reference. ResultsTwo hundred ninety-nine patients treated with warfarin across three Mayo Clinic sites agreed to participate. Atrial fibrillation (n=191, 63.9%), venous thromboembolism (n=65; 21.7%), and heart valve prosthesis (n=46; 15.4%) were common anticoagulant indications with a 2.5 INR target for 280 (93.6%) of patients. For the CoaguChek devices, 243 (81.3%) of values fell within 0.2 INR units with plasma INR referent and 285 (95.3%) within 0.4 units (R2=0.93). For the Coag-Sense device, 102 (34.1%) of values fell within 0.2 INR units and 180 (60.2%) within 0.4 INR units of plasma INR values, (R2=0.83; P<.0001). Using the plasma INR as the gold standard, appropriate dosing recommendations would have occurred for 292 (97.7%) of the CoaguChek and 244 (81.6%) of the Coag-Sense results. ConclusionCompared with a plasma referent, INR values obtained from the CoaguChek devices exhibited less systematic bias compared with Coag-Sense measures. This translates to a greater percentage of concordant management decisions between POC and laboratory INR methods.