Cardiac Valve Prostheses Research Articles

Clinical Effects of Hospital–Family Collaborative Cardiac Rehabilitation Training on Patients with Heart Failure after Cardiac Valve Prostheses

Background: Affected by factors, such as patients' age, course of disease, and underlying diseases, patients have high complications after cardiac valve replacement. This study applied hospital–family collaborative cardiac rehabilitation training to patients with heart failure undergoing cardiac valve prostheses and explored the clinical effect to provide guidance for postoperative rehabilitation. Methods: The clinical data of 213 patients with heart failure admitted to our hospital from January 2023 to January 2024 were retrospectively analyzed. After 12 cases who did not meet the inclusion criteria were excluded, 201 cases were finally included. In accordance with different nursing methods, patients were divided into reference group (n = 102) and observation group (n = 99). The reference group received routine nursing program, whereas the study group adopted hospital–family collaborative cardiac rehabilitation training on the basis of routine nursing. The levels of cardiac function indices [left ventricular ejection fraction (LVEF), left ventricular end-diastolic volume (LVEDV), left ventricular end-systolic volume (LVESV) and stroke volume (SV)], quality of life, cardiovascular risk factors [total cholesterol (TC), triglyceride (TG), and fasting blood glucose (FBG)] and the rehospitalization rate were compared between the two groups. Results: Before management, the levels of LVEF, LVEDV, LVESV, SV, quality-of-life scores, TC, TG, and FBG in the two groups were similar (p > 0.05). After management, the observation group had higher levels of LVEF, LVEDV, LVESV, and SV (p < 0.001); a better quality of life (p < 0.001); lower levels of TC, TG, and FBG (p < 0.001); and a lower rehospitalization rate (p < 0.05) than the reference group. Conclusion: Hospital–family collaborative cardiac rehabilitation training seems to improve the cardiac function indices of patients undergoing cardiac valve prostheses, and it has a certain clinical application value. However, the results should be promoted with caution, and more studies are needed to verify them.

Mechanical behaviors of high-strength fabric composite membrane designed for cardiac valve prosthesis replacement

Bovine pericardium has been commonly used as leaflets in cardiac valve prosthesis replacement for decades because of its good short-term hemocompatibility and hemodynamic performance. However, fatigue, abrasion, permanent deformation, calcification, and many other failure modes have been reported as well. The degradation of the performance will have a serious impact on the function of valve prostheses, posing a risk to the patient's health. This study aimed to introduce a flexible fabric composite with better mechanical performance such that it can be employed as a substitute material for bioprosthetic valve leaflets. This composite has a multilayered thin film structure made of ultrahigh molecular weight polyethylene (UHMWPE) fabric and thermoplastic polyurethane (TPU) membranes. The mechanical properties of three specifications with different design parameters were tested. The tensile strength, shear behavior, tear resistance, and bending stiffness of the composites were characterized and compared to those of bovine pericardium. A constitutive model was also established to describe the composites' mechanical behaviors and predict their strength. According to the results of the tests, the composite could maintain a flexible bending stiffness with high in-plane tensile strength and tear strength. Therefore, bioprosthetic valve made of this substitute material can withstand harsher loads in the blood flow environment than those made of bovine pericardium. Moreover, all these test results and constitutive models can be used in future research to evaluate hemodynamic performance and clinical applications of fabric composite valve prostheses.

Management of Antithrombotic Drugs in Patients with Isolated Traumatic Brain Injury: An Intersociety Consensus Document.

All available recommendations about the management of antithrombotic therapies (ATs) in patients who experienced traumatic brain injury (TBI) are mainly based on expert opinion because of the lack of strength in the available evidence-based medicine. Currently, the withdrawal and the resumption of AT in these patients is empirical, widely variable, and based on the individual assessment of the attending physician. The main difficulty is to balance the thrombotic and hemorrhagic risks to improve patient outcome. Under the endorsement of the Neurotraumatology Section of Italian Society of Neurosurgery, the Italian Society for the Study about Haemostasis and Thrombosis, the Italian Society of Anaesthesia, Analgesia, Resuscitation, and Intensive Care, and the European Association of Neurosurgical Societies, a working group (WG) of clinicians completed two rounds of questionnaires, using the Delphi method, in a multidisciplinary setting. A table for thrombotic and bleeding risk, with a dichotomization in high risk and low risk, was established before questionnaire administration. In this table, the risk is calculated by matching different isolated TBI (iTBI) scenarios such as acute and chronic subdural hematomas, extradural hematoma, brain contusion (intracerebral hemorrhage), and traumatic subarachnoid hemorrhage with patients under active AT treatment. The registered indication could include AT primary prevention, cardiac valve prosthesis, vascular stents, venous thromboembolism, and atrial fibrillation. The WG proposed a total of 28 statements encompassing the most common clinical scenarios about the withdrawal of antiplatelets, vitamin K antagonists, and direct oral anticoagulants in patients who experienced blunt iTBI. The WG voted on the grade of appropriateness of seven recommended interventions. Overall, the panel reached an agreement for 20 of 28 (71%) questions, deeming 11 of 28 (39%) as appropriate and 9 of 28 (32%) as inappropriate interventions. The appropriateness of intervention was rated as uncertain for 8 of 28 (28%) questions. The initial establishment of a thrombotic and/or bleeding risk scoring system can provide a vital theoretical basis for the evaluation of effective management in individuals under AT who sustained an iTBI. The listed recommendations can be implemented into local protocols for a more homogeneous strategy. Validation using large cohorts of patients needs to be developed. This is the first part of a project to update the management of AT in patients with iTBI.

First experience of transcatheter implantation of a Russian-made MedLab-CT prosthesis in a patient with dysfunction of biological mitral valve prosthesis

We present a case report of successful transcatheter implantation of a Russian-made cardiac valve prosthesis in a patient with dysfunction of biological mitral valve prosthesis (valve-in-valve). A patient aged 78 years with a high surgical risk and severe heart failure due to mitral valve bioprosthesis dysfunction is described. Fluoroscopyand transesophageal echocardiography-guided transapical implantation of a MedLab-CT prosthesis (23 mm) was made. When a heart rate of 180 beats per minute, a stent prosthesis was implanted. Transcatheter implant valve functioned properly after surgery. The patient was discharged in satisfactory condition.

Modern concepts from old ideas in manufacture of cardiac valve prostheses.

In reviewing the history of mechanical prosthetic valves, it appears evident how many improvements and technical advances have been obtained in this field. Looking to the past, it must also be underlined how some old concepts, which can be considered quite revolutionary for those years, clearly indicate the great skill and ingenuity of those who conceived them. Old ideas have been revitalized by modern concepts, and this is exemplified when considering the developments of bileaflet and sutureless prostheses.

Sterilization and Cross-Linking Combined with Ultraviolet Irradiation and Low-Energy Electron Irradiation Procedure: New Perspectives for Bovine Pericardial Implants in Cardiac Surgery.

Bovine pericardium is the major natural source of patches and aortic valve substitutes in cardiac repair procedures. However, long-term tissue durability and biocompatibility issues lead to degeneration (e.g., calcification) that requires reoperation. Tissue preparation strategies, including glutaraldehyde fixation, are reasons for the deterioration of pericardial tissues. We describe a pretreatment procedure involving sterilization and cross-linking combined with ultraviolet (UV) irradiation and low-energy electron irradiation (SULEEI). This innovative, glutaraldehyde-free protocol improves the mechanical aspects and biocompatibility of porcine pericardium patches. We adopted the SULEEI protocol, which combines decellularization, sterilization, and cross-linking, along with UV irradiation and low-energy electron irradiation, to pretreat bovine pericardium. Biomechanics, such as ultimate tensile strength and elasticity, were investigated by comparing SULEEI-treated tissue with glutaraldehyde-fixed analogues, clinical patch materials, and an aortic valve substitute. Histomorphological and cellular aspects were investigated by histology, DNA content analysis, and degradability. Mechanical parameters, including ultimate tensile strength, elasticity (Young's modulus), and suture retention strength, were similar for SULEEI-treated and clinically applied bovine pericardium. The SULEEI-treated tissues showed well-preserved histoarchitecture that resembled all pericardial tissues investigated. Fiber density did not differ significantly. DNA content after the SULEEI procedure was reduced to less than 10% of the original tissue material, and more than 50% of the SULEEI-treated pericardium was digested by collagenase. The SULEEI procedure represents a new treatment protocol for the preparation of patches and aortic valve prostheses from bovine pericardial tissue. The avoidance of glutaraldehyde fixation may lessen the tissue degeneration processes in cardiac repair patches and valve prostheses.

Medium-term results of transcatheter implantation of MedLab-CT aortic valve prosthesis

Aim. To assess the clinical and hemodynamic results of transcatheter aortic valve replacement with the MedLab-CT prosthesis. Material and methods. MedLab-CT is the first Russian transcatheter implantable cardiac valve prosthesis. It is a balloon — an expandable stent, the cusps of which are made of 0,1 mm thick polytetrafluoroethylene plates. The use of synthetic material for the manufacture of the locking mechanism of the transcatheter implantable cardiac valve prostheses is a priority choice in the world. The reason was the hypothesis suggesting the absence of biodegradation of polytetrafluoroethylene in the body. The mechanical stability of the valve was tested on the pulse duplicator with a load equivalent to 10 years of functioning in the aortic position. The study included 69 patients who underwent implantation of the MedLab-CT prosthesis. One of the exclusion criteria for surviving patients was a follow-up period of less than 6 months. We estimated survival and incidence of clinically significant stroke, as well as hemodynamic parameters according to echocardiography for up to 3 years. Thirty nine patients were examined by face-toface approach, the rest ones underwent a telephone questionnaire survey. Results. The average follow-up was 9,6 months, the maximum — 3 years. Most patients belonged to the elderly group (average age 73,3 years). For 51 patients (74%) according to the EuroSCORE scale and for 37 (54%), according to the STS scale, a high risk of surgical intervention was determined: ≥8%.Mortality rate was 13% — 6 deaths were noted at the hospital stage, 3 patients died in the long term. No strokes recorded. In the face-to-face group, mean gradient on the aortic valve prosthesis was determined to be 8,41±4,21 mm Hg; insufficiency due to paraprosthetic fistulas not higher than I degree was observed in 7 patients (18%), not higher than II degree — in 1 patient; cases of transvalvular aortic insufficiency was not revealed. Conclusion. The results on the studied parameters are comparable with the data presented by foreign randomized clinical trials of imported models of transcatheter aortic valve prostheses.

Heart-brain interactions

Heart-brain interactions are represented by the association of cerebral ischemia with coronary artery disease, cardioembolic cerebral ischemia, and cardiovascular complications due to brain damage. As atherosclerosis is a systemic inflammatory disease, in patients with transient ischemic attack, stroke or asymptomatic carotid artery disease, a previous myocardial infarction, angina or an asymptomatic coronary artery disease are often associated and a correlation between the carotid atherosclerosis and coronary artery disease severity has been reported. Furthermore, the long-term prognosis of patients with stroke is strongly affected by coronary events. At the same time, the prevalence of concomitant cerebrovascular disease is common in patients with coronary artery disease. Other cardiovascular diseases, including left atrial and left atrial appendage thrombosis in atrial fibrillation, thrombi in the left ventricle in acute and chronic coronary artery disease and dilated cardiomyopathies, infective endocarditis with vegetations, cardiac valve prosthesis thrombosis, cardiac tumors, mitral and aortic valve calcifications, aortic plaques and patent foramen ovale, are associated with cardioembolic events. Finally, acute ischemic or hemorrhagic cerebral events, epileptic seizures, cerebral traumas, and brain tumors can be associated with electrocardiographic abnormalities, catecholaminergic myocardial damage, or arrhythmias.

Wear behavior of fluorinated diamond-like carbon (DLC) film in bull serum albumin (BSA) solutions

Fluorinated diamond-like carbon (DLC) films have good biocompatibility and bloodcompatibility. When they are used in cardiac valve prosthesis, the wear resistance has to be investigated in more detail. In this paper, the tribological behavior of fluorinated DLC films under different loads and sliding speeds in bull serum albumin (BSA) solutions were investigated by ball-on-disc friction tests. The results show that the proteins in BSA solutions promoted the DLC film adhesion failure because of the increased friction coefficients and accelerated corrosion rate. The fluorine doping can lower the corrosion rate of DLC film, thereby improving the adhesion stability and wear resistance of DLC in BSA solutions.

Successful Management of Prosthetic Valve Brucella Endocarditis with Antibiotherapy Alone.

ObjectivesTo report a case of mechanical aortic prosthesis Brucella endocarditis successfully treated with antibiotics alone.Materials and methods: We describe a clinical case and present a review of the literature.ResultsA 60-year-old female farmer with a mechanical aortic prosthetic valve presented with low back pain and fever. She was diagnosed with prosthetic valve Brucella mellitensis endocarditis and was cured with antibiotic therapy alone. Few cases of successfully treated prosthetic valve Brucella endocarditis without surgery have been reported.ConclusionProsthetic valve Brucella endocarditis usually requires surgical valve replacement. However, selected patients may be successfully treated with antibiotic therapy alone.LEARNING POINTSBrucella endocarditis is responsible for most fatal cases of brucellosis.Brucellosis relapse after treatment in patients with a cardiac valve prosthesis should arouse suspicion for endocarditis.Long-term medical treatment alone can be successful in selected patients with Brucella endocarditis, even in those with prosthetic valve endocarditis..

Micro-Arc Oxidation Enhances the Blood Compatibility of Ultrafine-Grained Pure Titanium.

Ultrafine-grained pure titanium prepared by equal-channel angular pressing has favorable mechanical performance and does not contain alloy elements that are toxic to the human body. It has potential clinical value in applications such as cardiac valve prostheses, vascular stents, and hip prostheses. To overcome the material’s inherent thrombogenicity, surface-coating modification is a crucial pathway to enhancing blood compatibility. An electrolyte solution of sodium silicate + sodium polyphosphate + calcium acetate and the micro-arc oxidation (MAO) technique were employed for in situ oxidation of an ultrafine-grained pure titanium surface. A porous coating with anatase- and rutile-phase TiO2 was generated and wettability and blood compatibility were examined. The results showed that, in comparison with ultrafine-grained pure titanium substrate, the MAO coating had a rougher surface, smaller contact angles for distilled water and higher surface energy. MAO modification effectively reduced the hemolysis rate; extended the dynamic coagulation time, prothrombin time (PT), and activated partial thromboplastin time (APTT); reduced the amount of platelet adhesion and the degree of deformation; and enhanced blood compatibility. In particular, the sample with an oxidation time of 9 min possessed the highest surface energy, largest PT and APTT values, smallest hemolysis rate, less platelet adhesion, a lesser degree of deformation, and more favorable blood compatibility. The MAO method can significantly enhance the blood compatibility of ultrafine-grained pure titanium, increasing its potential for practical applications.

Intravascular hemolysis in patients with mitral regurgitation: Evaluation by erythrocyte creatine

BackgroundIntravascular hemolysis has been reported in patients with cardiac valve prostheses, but intravascular hemolysis in patients with mitral regurgitation with native valve has not been evaluated in detail. We designed a study to elucidate the impact of regurgitation flow on intravascular hemolysis in patients with primary mitral regurgitation by measuring erythrocyte creatine. MethodsErythrocyte creatine was enzymatically assayed in 29 patients with moderate to severe primary mitral regurgitation and 12 age-matched healthy volunteers. The size and characteristics of mitral regurgitation were determined by color Doppler echocardiography. ResultsErythrocyte creatine was significantly higher in patients with eccentric jet (n=17, 2.64±0.77μmol/g Hb) than that of central jet (n=12, 1.68±0.13μmol/g Hb) and control subjects (1.39±0.25μmol/g Hb). Patients with eccentric jet had a significantly lower erythrocyte count and hemoglobin (385±58 x104/μL and 116±19g/l) compared to those with central jet (450±47×104/μL and 137±14g/l) and control subjects (433±31×104/μL and 134±19g/l). There were no significant differences in age, estimated glomerular filtration rate, pulmonary artery systolic pressure, left atrial size and left ventricular end-diastolic dimension between patients with eccentric jet and central jet. ConclusionsIntravascular hemolysis associated with subclincal anemia in patients with eccentric jet was due to the destruction of erythrocyte by collision of the eccentric jet to the atrial wall.

VWF Multimer Quantitation for Assessment of Cardiac Lesion Severity and Bleeding Risk

Introduction: Recent reports have utilized von Willebrand factor (VWF) multimerquantitation in the assessment of native cardiac lesions and prosthetic valve dysfunction. However there is no standardized method for quantitation. We compared 3 methods of assessment which utilized a normal plasma control.Methods: We analyzed 476 samples and their control plasma from 395 patients including normal subjects, patients with aortic stenosis, hypertrophic cardiomyopathy, mitral or aortic regurgitation, normal and abnormal left cardiac valve prostheses, and left ventricular assist device therapy (LVAD). VWF multimers were assessed as normal or abnormal, or as normalized (patient / normal plasma) VWF multimerratios of gel bands >15/2-15 (NMR 15) or gel bands > 10/2-10 (NMR 10). We tested whether one technique was more strongly associated with hemodynamic severity of the cardiac lesion, with a history of acquired bleeding, and compared the results to a separate test of VWF function, platelet function analyzer 15 00 (PFA).Results: Two hundred seventeen patient samples reflected normal or mildly abnormal hemodynamics, 111 moderate, and 113 severely abnormal hemodynamics. Abnormal multimers were present in only 19% of samples with normal or mildly abnormal hemodynamics compared to 79% abnormal in the presence of moderate to severe hemodynamic abnormality. The distinction between moderate and severe hemodynamic abnormality was less striking, 65% versus 88% (figure, left). Quantitative NMR values declined with increasing cardiac lesion severity (figure, middle). The two quantitative multimermethods showed similar relationships to lesion severity by ANOVA, r=0.40 (NMR 15) versus r=0.36 (NMR 10), and by Spearman correlation, r=0.68 for NMR 15, and r=0.66 for NMR 10, and PFA results were comparable (all p< 0.001). Bleeding rates were associated with NMR 15, 10 and PFA (Mann-Whitney p<0.001, figure, right).Conclusion: The dichotomous normal / abnormal VWF multimer method appears to distinguish ≥ moderate hemodynamic disruption, whereas there is a continuous relationship between hemodynamic severity and quantitative multimer methods, which may be clinically useful in circumstances in which clinical estimation of lesion severity is challenging, such as with dysfunctional prosthetic valves. Progressive loss of VWF multimersappears to be associated with bleeding, suggesting that quantitative measures may provide incremental value over the dichotomous normal / abnormal designation. [Display omitted] DisclosuresBlackshear:Baxalta, Inc: Consultancy, Research Funding.

Acute felon and paronychia: Antibiotics not necessary after surgical treatment. Prospective study of 46 patients

Paronychia and felon are the most common infections of the hand. Surgical treatment is required once an abscess develops, but systematic use of postoperative antibiotic therapy remains open for discussion. Antibiotics both favor the selection of resistant bacteria and increase the cost of treatment. To our knowledge, no study has demonstrated their benefit following excision, yet many practitioners prescribe them systematically and empirically. In our current practices, we do not use antibiotic coverage following excision of uncomplicated paronychia or felon (no signs of arthritis, osteitis, flexor tenosynovitis, lymphangitis), except in potentially at-risk patients (immunosuppressed, diabetic, cardiac valve prosthesis recipient). Since this approach seems to lead to good outcomes, our objective was to evaluate them clinically in this study. Our prospective study included 46 patients who were not considered at risk. There were 26 cases of paronychia, 3 cases of felon and 17 patients presenting both paronychia and felon. All cases were abscessed and uncomplicated. All patients underwent surgical excision, and none received postoperative antibiotics. Follow-up took place on the day after surgery, at days 7, 14, 21 and 45. The main criterion for evaluation was healing of the infection and the wound. We recorded 45 cases of healing with no complications and a single case of recurrence. Surgical excision of paronychia or felon without antibiotic coverage gives excellent results with only rare recurrence. The single failure can be attributed to inadequate excision. Antibiotic therapy has no role in managing uncomplicated felon or paronychia in patients who are otherwise not at risk. Successful treatment depends above all on the completeness of the surgical excision.

Evaluation of Intravascular Hemolysis With Erythrocyte Creatine in Patients With Aortic Stenosis

Chronic intravascular hemolysis has been identified in patients with cardiac valve prostheses, but only a few case reports have evaluated intravascular hemolysis in patients with native valvular heart disease. To detect intravascular hemolysis in patients with aortic stenosis, erythrocyte creatine was evaluated with hemodynamic indices obtained by echocardiography.Erythrocyte creatine, a marker of erythrocyte age, was assayed in 30 patients with aortic stenosis and 10 aged matched healthy volunteers. Peak flow velocity of the aortic valve was determined by continuous-wave Doppler echocardiography. Twenty of 30 patients with aortic stenosis had high erythrocyte creatine levels (> 1.8 µmol/g Hb) and erythrocyte creatine was significantly higher as compared with control subjects (1.98 ± 0.49 versus 1.52 ± 0.19 µmol/g Hb, P = 0.007). Peak transvalvular pressure gradient ranged from 46 to 142 mmHg and peak flow velocity ranged from 3.40 to 5.95 m/second. Patients with aortic stenosis had a significantly lower erythrocyte count (387 ± 40 versus 436 ± 42 × 10(4) µL, P = 0.002) and hemoglobin (119 ± 11 versus 135 ± 11 g/L, P < 0.001) as compared with control subjects. Erythrocyte creatine had a fair correlation with peak flow velocity (r = 0.55, P = 0.002).In conclusion, intravascular hemolysis due to destruction of erythrocytes was detected in patients with moderate to severe aortic stenosis and the severity of intravascular hemolysis was related to valvular flow velocity of the aortic valve.

Maternal and Fetal Outcomes in Pregnant Women with a Prosthetic Mechanical Heart Valve.

BACKGROUNDPregnancy is associated with several cardiocirculatory changes that can significantly impact underlying cardiac disease. These changes include an increase in cardiac output, sodium, and water retention leading to blood volume expansion, and reductions in systemic vascular resistance and systemic blood pressure. In addition, pregnancy results in a hypercoagulable state that increases the risk of thromboembolic complications.OBJECTIVESThe aim of this study is to assess the maternal and fetal outcomes of pregnant women with mechanical prosthetic heart valves (PHVs).METHODSThis is a prospective observational study that included 100 pregnant patients with cardiac mechanical valve prostheses on anticoagulant therapy. The main maternal outcomes included thromboembolic or hemorrhagic complications, prosthetic valve thrombosis, and acute decompensated heart failure. Fetal outcomes included miscarriage, fetal death, live birth, small-for-gestational age, and warfarin embryopathy. The relationship between the following were observed: – Maternal and fetal complications and the site of the replaced valve (mitral, aortic, or double)– Maternal and fetal complications and warfarin dosage (≤5 mg, >5 mg)– Maternal and fetal complications and the type of anticoagulation administered during the first trimesterRESULTSThis study included 60 patients (60%) with mitral valve replacement (MVR), 22 patients (22%) with aortic valve replacement (AVR), and 18 patients (18%) with double valve replacement (DVR). A total of 65 patients (65%) received >5 mg of oral anticoagulant (warfarin), 33 patients (33%) received ≤5 mg of warfarin, and 2 patients (2%) received low-molecular-weight heparin (LMWH; enoxaparin sodium) throughout the pregnancy. A total of 17 patients (17%) received oral anticoagulant (warfarin) during the first trimester: 9 patients received a daily warfarin dose of >5 mg while the remaining 8 patients received a daily dose of ≤5 mg. Twenty-eight patients (28%) received subcutaneous (SC) heparin calcium and 53 patients (53%) received SC LMWH (enoxaparin sodium). Prosthetic valve thrombosis occurred more frequently in patients with MVR (P = 0.008). Postpartum hemorrhage was more common in patients with aortic valve prostheses than in patients with mitral valve prostheses (P = 0.005). The incidence of perinatal death was higher in patients with AVR (P = 0.014). The incidence of live birth was higher in patients with DVR (P = 0.012). The incidence of postpartum hemorrhage was higher in patients who received a daily dose of >5 mg of warfarin than in patients who received ≤5 mg of warfarin (P = 0.05). The incidence of spontaneous abortion was also higher in patients receiving >5 mg of warfarin (P ≤ 0.001), while the incidence of live births was higher in patients receiving ≤5 mg of warfarin (P = 0.008). There was a statistically significant difference between the anticoagulant received during the first trimester and cardiac outcomes. Specifically, patients on heparin developed more heart failure (P = 0.008), arrhythmias (P = 0.008), and endocarditis (P = 0.016). There was a statistically significant relationship between heparin shifts during the first trimester and spontaneous abortion (P = 0.003).CONCLUSIONWarfarin use during the first trimester is safer for the mother but is associated with more fetal loss, especially in doses that exceed 5 mg. The incidence of maternal complications is greater in women who receive LMWH or unfractionated heparin during the first trimester, especially prosthetic valve thrombosis, although the fetal outcome is better because heparin does not cross the placenta.

Warfarin Therapy: New Challenges of an Old Drug

The anticoagulant drug warfarin is a vitamin K antagonist (VKA), coumarin derivative, formed by the racemic mixture of two optically active isomers known by Rectus (R) and Sinister (S) enantiomers in equal proportion, being the S-warfarin five times more potent. Although warfarin is still considered the mainstay of oral anticoagulant treatment, it is a difficult drug to manage due to its narrow therapeutic index. An inappropriate management of patients can lead to subtherapeutic or supratherapeutic levels, increasing the risk of thromboembolic episodes or hemorrhagic episodes, respectively. Common indications for the use of warfarin include stroke prevention in atrial fibrillation, preventing thrombus formation in patients with heart valves and treatment of venous thromboembolism. Unlike situations as nonvalvular atrial fibrillation (and thromboembolic risk factors such as hypertension, diabetes or ventricular dysfunction), venous thrombosis and pulmonary embolism where there is evidence for the use of the new oral anticoagulants (dabigatran, apixaban, rivaroxaban, etc), warfarin and similar remain only option for patients with cardiac valve prosthesis requiring anticoagulation.

Clots and cardiac valve prostheses

Clots and cardiac valve prostheses

In vitro assessment of the lenz effect on heart valve prostheses at 1.5 T

Increasing numbers of patients with cardiac valve prostheses are being referred for magnetic resonance imaging (MRI) despite concerns about the potential for functional valve impedance due to Lenz forces. This study aims to determine, in vitro, the occurrence of Lenz forces on 9 heart valve prostheses at 1.5 T and assess the risk of impedance of valve function. A specially designed hydro-pneumatic system was used to record pressure changes across the valve indicative of any MR induced alteration in leaflet performance. Nine cardiac valve prostheses were exposed to the B0 field at 1.5 T. Each valve was advanced through the B0 field and continuous signals from high frequency pressure transducers were recorded and pressure drops across the valve were assessed using time correction superimposition. The delta p across the valve was assessed as a marker of any MRI induced alteration in leaflet performance. All prostheses produced sinusoidal waveforms. Profiles were asymmetrical and there was no consistency in complex shape and valve type/sub-group. Irregularities in pressure profiles of 4 prostheses were detected indicating resistance of the occluder to the B0 field. This study provides empirical evidence of the Lenz Effect on cardiac valve prostheses exposed to the MR B0 field causing functional valve impedance and increasing the risk of valvular regurgitation and reduced cardiac output. Thus, it is essential to consider the potential for the Lenz Effect when scanning cardiac valve implant patients in order to safeguard their wellbeing.

Simulating the Dynamics of an Aortic Valve Prosthesis in a Pulse Duplicator: Numerical Methods and Initial Experience.

Each year, approximately 250,000 surgical procedures are performed to repair or to replace cardiac valves [1], and of these, approximately 50,000 are aortic valve replacement operations. Despite decades of development, many of the limitations of cardiac valve prostheses remain consequences of the fluid dynamics generated by the replacement valve [1]. To enable cross-validation studies that allow for detailed comparisons of experimental and computational results, we are developing fluid-structure interaction (FSI) models of the dynamics of aortic valve prostheses mounted in a ViVitro Systems, Inc. pulse duplicator apparatus. Such an experimentally validated computational model promises both to facilitate the design of novel valve prostheses, and also to assist in the regulatory process, by providing access to detailed spatially- and temporally-resolved flow data that are challenging to obtain via experimental approaches.Our numerical approach to FSI is based on the immersed boundary (IB) method [2]. The structural dynamics are described in Lagrangian form using a material coordinate system, whereas the momentum of the fluid-solid system and the viscosity and incompressibility of the fluid are described in Eulerian form using fixed Cartesian physical coordinates. Lagrangian and Eulerian variables are coupled by integral transforms with Dirac delta function kernels. When the equations are discretized, the singular delta function is replaced by a regularized version of the delta function. See Peskin [2] for details.To treat rigid body dynamics within the framework of the IB method, we adopt an approach similar to that recently developed by Kim and Peskin [3], in which the continuous equations are:(1)ρ(∂u∂t(x,t)+u(x,t)·∇u(x,t)) =-∇p(x,t)+μ∇2u(x,t)+f(x,t)(2)∇·u(x,t)=0(3)f(x,t)=∫UF(s,t)δ(x-X(s,t))ds(4)∂X∂t(s,t)=∫Ωu(x,t)δ(x-X(s,t))dx(5)∂Y∂t(s,t)=V(t)+W(t)×R(s,t)(6)F(s,t)=κ(Y(s,t)-X(s,t))in which x∈Ω are physical coordinates, s∈U are material coordinates, X(s,t) and Y(s,t) are time-dependent mappings from material coordinates to current coordinates, u(x,t) is the Eulerian velocity field, p(x,t) is the Eulerian pressure field, f(x,t) and F(s,t) are equivalent Eulerian and Lagrangian force densities, ρ is the fluid density, μ is the fluid viscosity, and δ(x)=δ(x)δ(y)δ(z) is the three-dimensional Dirac delta function. The force field F(s,t) acts to impose the rigidity constraint ∂X∂t(s,t)=U(s,t)=V(t)+W(t)×R(s,t)in which V(t) and W(t) are respectively the linear and angular velocity of the structure and R(s,t) is the radius vector. In the limit κ→∞, the constraint is imposed exactly; for finite κ&gt;0, the constraint is only approximately satisfied. The dynamics of V(t) and W(t) are determined from the requirement that the time rate of change of the “excess” linear and angular momentum (i.e., in excess of the momentum accounted for by the momentum equation (1)) be proportional to the net force ∫Ω-F(s,t)ds and net torque ∫Ω-F(s,t)×R(s,t)ds acting on the body.Geometrical models of the aortic section of the ViVitro pulse duplicator and of a St. Jude Regent valve were created using SolidWorks (Dassault Systèmes SolidWorks Corp., Waltham, MA). These geometrical models were meshed using CUBIT (Sandia National Laboratory, Albuquerque, NM). To drive flow through the valve, we impose a physiological left ventricular pressure waveform, and characteristic downstream compliance and resistance to mimic the response of the systemic circulation. Simulations used the IBAMR software [4]. Initial simulation results are shown in Fig. 1, demonstrating that realistic flow rates can be obtained using this model under realistic driving and loading conditions. We are presently fine tuning this model in preparation for validation studies.We acknowledge discussions with A. P. S. Bhalla, A. Donev, D. M. McQueen, and C. S. Peskin, and funding from AHA award 10SDG4320049, NIH award HL117063, and NSF awards DMS 1016554 and OCI 1047734.