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At least 325 records · Page 18Linked to original sources
PubMed1998

Experimental right ventricle to pulmonary artery discontinuity: outcome of polyurethane valved conduits.

OBJECTIVE: The ideal substitute for the treatment of ventricle-pulmonary artery discontinuity remains a topic of controversy, because of calcifications and degeneration of biologic substitutes leading to subsequent reoperations. Because polyurethane valves used in ventricular assist devices show a satisfactory biocompatibility, the aim of this study was to evaluate a valved conduit composed of a Dacron graft incorporating a trileaflet 25 mm polyurethane valve. METHODS: The conduit was implanted between the right ventricle and the main pulmonary artery in adult sheep, with ligation of the proximal pulmonary artery. The animals received no medications. Serial hemodynamic data were collected at the time of implantation and at postoperative intervals of 6 and 12 months. RESULTS: The peak pressure gradient across the valve increased significantly between implantation (0.17 +/- 5.6 mm Hg) and 6 months after operation (7.3 +/- 3 mm Hg, p = 0.0007) and remained stable thereafter (6.7 +/- 3 mm Hg at 12 months), whereas the cardiac output remained unchanged (4.6 +/- 0.6 L/min at implantation, 4 +/- 0.6 L/min at 6 months, and 3.9 +/- 1.1 L/min at 12 months). At the completion of the study, valve samples were processed and vapor coated with carbon for microscopic examination. There was one instance of nonadherent thrombus formation inside a cusp but no structural failures. The other valves were free of calcium deposits and no significant amounts of phosphorus could be detected by scanning electron microscopy and energy dispersive spectrometry. CONCLUSIONS: These data demonstrate the good hemodynamic performance, low thrombogenicity, and acceptable durability of the polyurethane valves implanted in the right side of the heart in a chronic sheep model.

Animals↗
PubMed1998

Early failure of an autologous pericardium aortic heart valve (ATCV) prosthesis.

BACKGROUND AND AIMS OF THE STUDY: The risk of reoperation due to calcific degeneration is the most important drawback of biological heart valves compared with mechanical prostheses. Concepts to mitigate calcification have been tested experimentally and clinically, but none has proven completely to prevent degeneration. METHODS: Renewed interest has involved the use of autologous pericardium for intraoperative construction of autologous aortic valves (ATCV). RESULTS: Of 10 ATCV implanted between 1994 and 1996, one was removed from an 84-year-old female 27 months after implantation because of severe valvular insufficiency. Eight months earlier, a broken spring of the stent system was detected radiographically, with normal valvular competence at echocardiography. Valve dysfunction was due to shrinkage of one leaflet. Measurement of tissue calcium by atomic absorption spectroscopy showed high levels in the shrunken leaflet compared with two intact leaflets (42.82 versus 0.51 and 2.42 mg Ca2+/g). Histology and immunohistology demonstrated extensive fiber degeneration without inflammation or immune reactions in the destroyed leaflet, and moderate fiber degeneration in intact leaflets. Scanning electron microscopy showed smooth surfaces in the normal leaflet and exposure of collagen in the degenerated leaflet in association with calcium deposition. CONCLUSIONS: In contrast to the outcome in animal studies, intraoperative tanning did not prevent tissue shrinkage in this case. Leaflet malfunction was associated with calcification. At present, the clinical use of valves constructed from autologous pericardium can not be recommended.

Aged↗
PubMed1998

Choosing a prosthetic heart valve.

Although most of the available prosthetic heart valves function remarkably well, the variety of available choices attests to the inability of any single one to fulfill the requirements of the ideal valve substitute. The mechanical prostheses include the caged-ball, tilting-disc, and bileaflet valves. Tissue valves available in the United States are the Carpentier-Edwards and Hancock porcine heterograft valves and the Carpentier-Edwards pericardial valve. Review of several large comparative studies on valve performance reveals that the overall results with tissue and mechanical valves are about equal at the end of 10 years. The characteristics of each type of valve substitute dictate the selection of one prosthesis in preference to others for a particular patient. Mechanical prostheses are recommended for patients without contraindications for anticoagulants. Tissue valves are reserved for patients over 65 years of age or for patients in whom anticoagulation is contraindicated. Multiple other patient-related factors need to be considered in selecting the appropriate valve, including the psychosocial situation and patient preference.

Biocompatible Materials↗
PubMed2006

Heart valve replacement: which valve for which patient?

The ideal heart valve substitute would show no deterioration or thrombogenicity, offer no resistance to blood flow, and be easy to implant. However, such a valve does not exist and we must accept compromises in some of these qualities based on our patients' needs. In selection of cardiac valve prosthesis, valve-related factors such as durability, thrombogenicity, and fluid dynamics should be carefully matched to patient-related factors such as age, size, life expectancy, comorbidities, plans for pregnancy, and lifestyle. In addition, surgeon- or operation-related factors should be considered. Technical aspects of implantation, ease of reoperation, and operative mortalities may tip the risk and benefit balance in a particular direction. We review currently available heart valve prostheses and the clinical factors that are involved in selection of a heart valve substitute.

Age Factors↗
PubMedDate not supplied

Application of tissue-engineering principles toward the development of a semilunar heart valve substitute.

Heart valve disease is a significant medical problem worldwide. Current treatment for heart valve disease is heart valve replacement. State of the art replacement heart valves are less than ideal and are associated with significant complications. Using the basic principles of tissue engineering, promising alternatives to current replacement heart valves are being developed. Significant progress has been made in the development of a tissue-engineered semilunar heart valve substitute. Advancements include the development of different potential cell sources and cell-seeding techniques; advancements in matrix and scaffold development and in polymer chemistry fabrication; and the development of a variety of bioreactors, which are biomimetic devices used to modulate the development of tissue-engineered neotissue in vitro through the application of biochemical and biomechanical stimuli. This review addresses the need for a tissue-engineered alternative to the current heart valve replacement options. The basics of heart valve structure and function, heart valve disease, and currently available heart valve replacements are discussed. The last 10 years of investigation into a tissue-engineered heart valve as well as current developments are reviewed. Finally, the early clinical applications of cardiovascular tissue engineering are presented.

Animals↗
PubMed1999

Artificial Valve Endocarditis Reduction Trial (AVERT): protocol of a multicenter randomized trial.

BACKGROUND AND AIM OF THE STUDY: This article presents the protocol of the Artificial Valve Endocarditis Reduction Trial (AVERT), a multicenter, international randomized trial to assess the efficacy of the SilzoneTM coating of St. Jude Medical Masters Series mechanical heart valves in the prevention of prosthetic heart valve endocarditis (PVE). A total of 4,400 eligible patients will be randomized within three years of study commencement at 17 participating clinical centers in North America and Europe, with study completion within four years. ELIGIBILITY CRITERIA: Eligible patients are candidates for St. Jude mechanical valves with either the Silzone or conventional cuff, in the mitral and/or aortic position, who give informed written consent to participate. Major exclusion criteria are the presence of prosthetic valves that do not require replacement, and the need for tricuspid valve replacement. Bypass surgery and valve repair are allowed during the implant operation. Patients will be randomized using an envelope-based intraoperative randomization scheme, stratified by clinical center and by the presence of endocarditis at the time of surgery. FOLLOW UP: Patients will be contacted at discharge, three months, and each anniversary of the implant procedure. A brief follow up survey, administered via clinic interview, telephone or mail, will elicit events associated with possible endocarditis (unexplained fever, worsening angina, hospitalization) that will initiate contact with the patient's following physician. OUTCOME ANALYSIS: The primary PVE endpoint will be based upon a published algorithm, with two infectious disease specialists making the final determination of cases classified as possible endocarditis. Study data will be periodically reviewed by a Data Safety Monitoring Board. The primary analysis will be an intention-to-treat comparison of freedom from PVE curves between the Silzone and conventional cuff treatment groups. CONCLUSIONS: AVERT will provide much-needed information on the effectiveness of Silzone in preventing PVE, as well as practice patterns and outcomes of valve replacement.

Clinical Protocols↗
PubMed2004

Changing trends in valve surgery in Europe: 1991-2000.

BACKGROUND AND AIM OF THE STUDY: This study sought to elaborate the changing trends in valve surgery in Europe during the 1990s. METHODS: The databases of different national surgical societies, registries and governments and international organizations were consulted and the data obtained were analyzed. RESULTS: The population of Europe (excluding Russia, CIS and Turkey) increased by 2.29%, from 509.67 million in 1991 to 519.15 million in 2000. During this period, the volume of cardiac surgery increased in Europe by 101% to 413,520 operations (797 per 10(6) population). The volume of valve surgery increased by 63% to 85,076 (164 per 10(6) population). The largest volumes of valve surgery were performed in Germany, France, UK, Italy and Spain. The increase in valve surgery volume was maximum in the Baltic states (+287%) and least in Scandinavia (+30%). Valve surgery volume per center per year changed from 139 in 1991 to 140 in 2000. The increase in overall valve surgery volume was sustained by an increase in subsets of octogenarian patients, valve surgery combined with coronary artery surgery, and increased productivity of the emerging economies of countries such as the Czech Republic, Hungary and Poland. Valve surgery as a proportion of cardiac surgery in Europe changed from 25.95% in 1991 to 21% in 2000. In 2000, valve surgery with combined procedures constituted 6.7% of total cardiac surgical volume, but 32% of valve surgical output in Europe. Mechanical valves have continued to dominate and were used in 77% of cases in 2000. Increased use of bioprostheses in the elderly subset among affluent economies was balanced by an increased use of mechanical prostheses in younger patients in emerging facilities in the East and South. The capital-intensive innovations (viz. robotic valve surgery, minimally invasive valve surgery, bioengineered valves) found niches only in some West European centers. Catheter-based procedures did not fulfil their promise. Balloon aortic valve dilatation investigations decreased drastically by the end of the decade, and balloon mitral dilatations number. Conservative aortic valve surgery is not yet practiced widely across Europe, while mitral repair has become widely accepted in clinical parlance. CONCLUSION: Despite the greater political and economic integration of Europe, the pattern of valve surgery continues to remain extremely diverse within the continent.

Aged↗
PubMed2003

Cardiac valve replacement in human immunodeficiency virus-infected patients.

BACKGROUND: Valve replacement in human immunodeficiency virus (HIV)-infected patients is being performed with increasing frequency, but the early and late results in these immunocompromised patients are not known. METHODS: A 10-year retrospective clinical review was undertaken; patients and their physicians were contacted for follow-up clinical status. RESULTS: Twenty-two HIV-infected patients underwent valve replacement between 1990 and 1999, with no operative or hospital deaths. Mean patient age was 37.6 years; 15 were men. Indications for operation were heart failure in 59% (13/22) and sepsis in 91% (20/22). There were 12 aortic valve replacements, seven mitral valve replacements, and three double valve replacements. Mechanical valves were used in 11, bioprostheses in seven, and homografts in four. Follow-up information was available in 20 of 22 patients (84%). At mean follow-up of 5 years, there were 10 late deaths, due to: intracerebral hemorrhage (2), heart failure (2), unknown cause (2), renal failure (1), AIDS (1), sepsis (1) and endocarditis (1). Of the 20 patients with active preoperative endocarditis, 4 (20%) developed recurrent endocarditis; freedom from recurrent endocarditis was 83% at 1 year. Intravenous drug abuse was reported in 16 patients; survival among these patients was 94% at 1 month and 50% at 5 years. Recurrent endocarditis was only seen in patients with continued intravenous drug abuse. CONCLUSIONS: Valve replacement in HIV-infected patients has low operative risk, but late results are poor when HIV infection is associated with intravenous drug abuse, probably due to immunocompromise and continued high-risk behavior.

Adult↗
PubMed2000

Development and evaluation of a swine model to assess the preclinical safety of mechanical heart valves.

BACKGROUND AND AIM OF THE STUDY: The current standard of in vitro and in vivo preclinical heart valve testing has recently been questioned because of its failure to reveal the thrombogenic potential of the Medtronic Parallel prosthetic valve. The aim of this study was to develop a swine model for the in vivo preclinical evaluation of mechanical heart valves, and to assess the ability of this model to identify mechanical heart valve design features that result in valve-related thrombosis. METHODS: Twenty-two swine underwent mitral valve replacement (MVR) using three different bileaflet mechanical valve designs (St Jude Medical, CarboMedics, Medtronic Parallel). Each animal was placed in an anticoagulation protocol (group I, INR 3.0-3.5; group II, INR 2.0-2.5; group III, no anticoagulation) and followed for up to 20 weeks. Terminal studies were performed on all animals surviving for more than 30 days. RESULTS: Twenty-one animals survived the immediate postoperative period. Four of six group I animals died from hemorrhagic (large wound hematoma; hemopericardium) complications early in the study. In the two long-term (61 and 89 days) survivors, INRs of 3.0 to 3.5 were never achieved (61-day survivor, mean INR 2.0 +/- 1.03; range: 0.8-5.4; 89-day survivor, mean INR 1.92 +/- 1.34; range: 1.0-7.9). Pathological analysis of explants from group I survivors revealed minimally obstructive fibrous sheathing on the inflow orifice without restriction of bileaflet motion (61 and 89 days), and two large perivalvular defects (61 days). Six of seven group II animals died from early hemorrhagic complications (hemopericardium) (mean INR 2.32 +/- 1.84; range: 0.8-8.2). Vegetations resulting in obstruction of both sides of the valve orifice and restriction of bileaflet motion were observed in a group II survivor (mean INR 2.33 +/- 1.58; range: 0.9-7.0). Group III animals (n = 8) survived for a mean of 106 +/- 60 days (range: 1-177 days). In group III, fibrous sheathing was present on all explanted valves and organized thrombi in six valves; orifice obstruction (seven valves) and restriction of bileaflet motion (three valves) were also observed. CONCLUSION: The use of MVR in swine as a preclinical model to evaluate the safety and performance of mechanical heart valves is limited by: (i) difficulty in maintaining safe levels of anticoagulation with warfarin, resulting in a high incidence of hemorrhagic complications; (ii) marked fibrous sheath formation and associated thrombosis; and (iii) an increased incidence of perivalvular defects, believed to result from normal somatic growth occurring in young swine.

Animals↗