SEARCH · PubMed Health

Results for “HEART VALVE PROSTHESIS”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 289 records · Page 16Linked to original sources

PubMed1995

[Triple mechanical heart valve prosthesis and pregnancy].

A very unusual case, of a multiparous, 36 year-old, woman, she had previous mechanical replacement of her mitral, aortic and tricuspid valves, and was with coumarins. Her 6th pregnancy was uneventful, with no cardiovascular decompensation and delivered a healthy baby girl, weighing 1,700 g. without congenital malformations. We discuss here, her medical management during and after pregnancy as well as, the factors influencing an optimal result for both, mother and baby.

Adult↗

PubMed2002

[Candida albicans endocarditis with mycotic aneurysms of the lower leg arteries in a patient with mechanical heart valve prosthesis].

We report on a 53-year-old patient in whom the aortic and mitral valves had been replaced. This patient developed Candida albicans sepsis with mycotic aneurysms of the tibial arteries as well as cerebral emboli under immunosuppression. Dispensing with a valve replacement operation, a sustained freedom from recurrence (period of observation currently 24 months) could be attained with antimycotic therapy with amphotericin B and flucytosine i.v. and subsequent long-term therapy with fluconazole p.o. as well as surgical and interventional clearance of the mycotic aneurysms.

Adult↗

PubMed1990

[Drug therapy following heart valve prosthesis].

Patients with prostheses of the cardiac valve are, related to the total population, only a small part. But their number permanently increases. Alone in our clinic since 1973 3,250 patients have been provided with artificial cardiac valves. Thus more and more physicians are confronted with the problems of these patients. The long-term results after replacement of the cardiac valves are very essentially influenced by the prevention and well-timed recognition of complications, respectively. For this reason the medicamentous therapy is demonstrated on the basis of own experiences and modern literature. It is clearly pointed out that after replacement of the cardiac valve a permanent cardiologic control is necessary. In detail is reported on the therapy of cardiac insufficiency including disturbances of the cardiac rhythm, on the prophylaxis of thromboembolism as well as on the prophylaxis of endocarditis.

Anti-Bacterial Agents↗

PubMed1988

[Clinical and social aspects of vocational rehabilitation of patients after heart valve prosthesis].

Clinical and social factors that determined the effect of occupational rehabilitation were analyzed in 71 patients after prosthetic valve implantation. In addition to objective factors, resuming work depended on a number of subjective ones as well, as the number of working individuals was virtually similar among the preoperative and follow-up patients, while the number of invalids increased, in spite of the fact that functional condition had improved by 1 or 2 functional classes, according to NYHA, in 52.8% of postoperative patients. There were no significant differences in physical working capacity, as evidenced by bicycle ergometry, between working postoperative patients and those who failed to resume working.

Adult↗

PubMed1994

Relationship between some design characteristics and wear in the Bicarbon heart valve prosthesis.

The hinge design of a new bileaflet valve (Bicarbon) is presented in relation to the long-term durability characteristics. Theoretical considerations supported by experimental findings, lead to the identification of two different wear mechanisms acting in bileaflet valves, i.e. impact and friction wear. Impact wear, caused by the collision between the hinge stops and inflow surface of the leaflet pivots, is the predominant phenomenon; it is mostly influenced by the design of the coupling elements. The wear due friction is significantly less important, given a proper kinematic coupling and a thorough washout. These different mechanisms can significantly affect the wear resistance and long-term reliability of bileaflet valves; therefore, they have been properly taken into account in designing the new valve model. The safety of the overall material and design solutions adopted in the Bicarbon valve has been confirmed by extensive accelerated durability tests resulting in no mechanical failure or loss of functionality.

Animals↗

PubMed1982

The Björk-Shiley heart valve prosthesis. Flow characteristics of the new 70 degrees model.

Thrombus formation on the outflow face and tissue overgrowth along the sewing ring adjacent to the minor outflow region are major clinical pathologic problems observed with the Björk-Shiley tilting disc valve. In the hope of reducing these pathologic conditions the convexo-concave Björk-Shiley valve was designed. A new modification to the convexo-concave model has further improved most of the fluid dynamic characteristics of the valve. In vitro flow studies indicate an average improvement in pressure drop characteristics of about 20 to 30%. Velocity measurements made with a laser-Doppler anemometer in the immediate downstream vicinity of the modified convexo-concave valve indicate that the design changes have further reduced the size of the stagnation zone near the outflow face of disc. It was observed, however, that the regurgitation across the valve increased by about one to two percentage points.

Aortic Valve↗

PubMed1991

[What type of heart valve prosthesis after age 70].

The choice of a valve replacement in patients over 70 years of age must take into account various parameters: the type of valve disorder being operated, the probability of post-operative survival in view of the stage of the valve disease and the age of the subject, and the advantages and draws-backs related to the replacements used. In the case of mechanical replacements, the main risks are related to the embolic and hemorrhagic problems inherent in anticoagulant treatment. In the case of biological replacements, the problems are related to the primary degeneration of these valves, which appears to be less frequent the higher the age. In patients over 75 years of age, bioreplacements have more advantages than mechanical valves. In subjects between 70 and 75 years of age, a mechanical valve can be recommended if there is no contraindication to anticoagulant treatment, if there is some other grounds for long-term anticoagulation and if the life expectancy appears to be greater than 10 years. In other situations, a bioreplacement is recommended.

Age Factors↗

PubMed1991

New J-3 flexible-leaflet polyurethane heart valve prosthesis with improved hydrodynamic performance.

The aim of this new three-leaflet valve development was to design a leaflet with minimum membrane stresses during performance. This is achieved by manufacturing the valve leaflets shaped almost flat in a medium opening position. Thus, the leaflets have two stable positions, one with maximum opening area and the other with favorable stress distribution in the closed position. The transition between the two end positions is achieved through a two-dimensional rolling motion without buckling and with minimum membrane stresses (bulge forces). The manufacturing technique is dip-coating in polyurethane. Hydrodynamic evaluation of the J-3 valve in steady and pulsatile flow showed minimum pressure drop compared to other commercially available valves. Laser-Doppler-anemometry studies indicated very low shear stresses in the flow field downstream of the valve. In durability tests prototypes have reached lifetimes of up to 17 years. In conclusion, the J-3 valve shows superior hydrodynamic performance thereby reducing potential thrombus formation. Minimization of stresses within the valve leaflets through design could reduce calcification.

Biomechanical Phenomena↗

PubMed1983

Steady and pulsatile flow studies on a trileaflet heart valve prosthesis.

The need for better and longer lasting trileaflet valves has led to the design and development of the ABIOMED polymeric trileaflet valve prosthesis. In vitro fluid dynamic studies in the aortic position indicate that overall it has improved leaflet motion characteristics and pressure drop characteristics compared to the Carpentier-Edwards porcine and Ionescu-Shiley pericardial tissue valves in current clinical use. The ABIOMED valve is, however, more stenotic compared to the St. Jude and Medtronic-Hall low profile mechanical valves, at normal cardiac outputs. Steady and pulsatile flow velocity measurements with a laser-Doppler anemometer system indicate that the flow field downstream of the ABIOMED valve is jet-like and leads to elevated shear stresses. These shear stresses are, however, lower than those observed with the Ionescu-Shiley and Carpentier-Edwards tissue valves. The ABIOMED valves tested had been originally configured for use in valved conduits, and it is therefore our opinion that further improvements can be made to the valve and stent design which would enhance its fluid dynamic performance.

Aortic Valve↗

PubMed1977

[Studies on blood traumatization following heart-valve prosthesis].

In 47 patients blood traumatisation was checked after interventions on cardiac valves. The cases in question were: 34 implantations of valve prostheses, 10 valve reconstructions and 3 re-operations because of paravalvular leakages. The tested valve prostheses according to Starr-Edwards, Björk-Shiley and Beall revealed subclinical haemolyses of various degrees. In aortic position the values for Björk-Shirley prostheses showed advantages as compared to the Starr-Edwards valve. Of all tested valve types the Beall prostheses caused the highest blood traumatisation. Manifest haemolytic anaemia was found only in 3 cases, two of them showing paravalvular leakage. In the cases of double valve replacement performed with combined Starr-Edwards and Beall prostheses the haemolysis was only slightly higher than in cases of mitral valve replacement with Beall valves only. In three cases with paravalvular leakage the parameters of haemolysis increased very much, returning to normal in 2 patients after successful correction. The assessment of the parameters of blood traumatisation is indispensible for the choice and improvement of the different types of valves and essential for the diagnosis of paravalvular leakage as well as for the control after leakage repair.

Anemia, Hemolytic↗

PubMedDate not supplied

[Flow characteristics in 3 kinds of heart valve prosthesis].

Transvalvular turbulence caused by the blood flow in implanted cardiac valvular prosthesis is the cause of thrombosis at the post-valvular region. The literature in this connection indicates that thromboembolic complications are more common with the tilting disc mechanical valves. In order to study the turbulence caused by porcine biological prosthetic valves, by a caged-ball Biomed mechanical valve and by a tilting disc Björk-Shiley valve, a device was developed which permits to visualize and to photograph flow characteristics in the three types of valves with the purpose of determining the degree of turbulence generated in each case. An additional accessory equipment was devised for the purpose of measuring static and dynamic pressures at various levels of the test tube containing the prosthetic valve wherein the variations in pressure reflect the degree of turbulence. The data obtained from 500 pressure registrations were analyzed in a computer. The data indicate that the porcine biological valve causes the least turbulence, whereas the mechanical valves create greater turbulence. Of the mechanical valves, the tilting disc prosthetic valve causes considerably greater turbulence, in particular in the vicinity of the smaller orifice.

Animals↗

PubMed1983

In-vitro fluid dynamic characteristics of the abiomed trileaflet heart valve prosthesis.

The need for better and longer lasting trileaflet valves has led to the design and development of the Abiomed polymeric trileaflet valve prosthesis. In-vitro fluid dynamic studies on sizes 25 and 21 mm valves in the aortic position indicate an overall improvement in performance compared to the Carpentier-Edwards and Ionescu-Shiley tissue valves in current clinical use. The pressure drop studies yielded effective orifice areas of 1.99 and 1.54 cm2, and performance indices of 0.41 and 0.45 for the Nos. 25 and 21 valves, respectively. Leaflet photography studies indicated that the two valve sizes had maximum opening areas of 225 and 145 mm2, respectively, at a normal resting cardiac output. Steady and pulsatile flow velocity measurements with a laser-Doppler anemometer (LDA) system indicate that the flow field downstream of the Abiomed valve is jetlike and turbulent. Maximum mean square axial velocity fluctuations of 55 and 83 cm/s, and turbulent shear stresses of 220 and 450 N/m2 were measured in the immediate vicinity of the nos. 25 and 21 valves, respectively. The Abiomed valves studied had been originally configured for use in valved conduits, and it is therefore our opinion that further improvements can be made to the valve and stent design, which would enhance its fluid dynamic performance.

Aortic Valve↗

PubMed1992

Late sudden cardiac death in the follow-up of patients having a heart valve prosthesis.

Eight hundred thirty-one patients with Björk-Shiley prostheses (341 aortic, 345 mitral, and 145 double) had a mean follow-up time of 68.2 months per patient. Of these, 24 (16% of all deaths) died suddenly: six of 42 with aortic valve replacement (14.3%), 12 of 56 with mitral valve replacement (21.4%), and six of 36 with double valve replacement (16.6%). This correlated with evidence of premature ventricular complexes detected in multiple routine 12-lead follow-up electrocardiograms (p less than 0.001 for simple aortic or mitral valve replacements and p less than 0.01 for combined aortic and mitral valve replacements). Premature ventricular complexes were significantly more frequent among those who died suddenly than among survivors and those who died of other causes (p less than 0.001 in both cases); there were no significant differences between the latter two groups. The actuarial risk of sudden death was significantly greater among those patients who had premature ventricular complexes than among those who did not have this disorder (p = 0.0002). We conclude that the presence of premature ventricular complexes, as an independent variable, was correlated with the risk of sudden death.

Adult↗

PubMed1988

A mechanical analysis of the closed Hancock heart valve prosthesis.

In order to obtain mechanical specifications for the design of an artificial leaflet valve prosthesis, a geometrically non-linear numerical model is developed of a closed Hancock leaflet valve prosthesis. In this model, the fibre reinforcement of the leaflet and the viscoelastic properties of frame and leaflets are incorporated. The calculations are primarily restricted to 1/6 part of the valve and a time varying pressure load is applied. The calculations are verified experimentally by measuring the commissure displacements and leaflet centre displacement of a Hancock valve. The numerically obtained commissure displacements are found to be linearly dependent on the pressure load, and the slope of the curves is hardly dependent on loading type and loading velocity. Experimentally a difference is found between the three commissure displacements, which is also predicted numerically using a simplified asymmetric total valve model. Besides, experimentally a clear dependency of commissure displacements on frame size is found. For the leaflet centre displacement, a qualitative agreement exists between numerical prediction and experimental result, although the numerical predicted values are systematically higher. The numerically obtained stress distributions revealed that the maximum von Mises intensity in the membranes occurs in the vicinity of the commissure in the free leaflet area (0.2 N mm-2). Wrinkling of the membranes may occur in the coaptation area near the leaflet suspension. The maximum fibre stress is found near the aortic ring in the fibres which form the boundaries of the coaptation area (0.64 N mm-2). These locations seem to correlate with some common regions of tissue valve failure.

Computer Simulation↗

PubMed2000

[6 years clinical experience with the TEKNA bivalve heart valve prosthesis].

OBJECTIVE: The revised Edwards-Duromedics valve was introduced onto the market in June 1990. In September 1993, the producer changed the name of the valve to TEKNA, which is a low profile, bileaflet, mechanical prosthesis with a self-irrigating hinge mechanism. The results of a prospective follow-up study after valve replacement with this prosthesis are presented. METHODS: From November 1990 to December 1996, 173 TEKNA prostheses were implanted in 161 patients (73 men, 88 women), either in the aortic (AVR; 48.4%), mitral (MVR; 44.1%), or aortic and mitral positions (DVR; 7.5%). Patient ages ranged from 17 to 83 years (mean age 59.2 +/- 8.7 years). Follow-up was 97.5% complete, comprising 433.15 patient-years for a mean follow-up of 34.8 +/- 23 months. RESULTS: Overall operative (30-day) mortality was 4.97%. Fifteen patients died in the late period, corresponding to a linearized late mortality rate of 3.5%/pt-yr. Actuarial survival at six years was 75.3% +/- 6.2% overall. The actuarial freedom from complications was calculated as follows (linearized rates in parentheses): valve-related mortality 91.3% +/- 5.1% (0.92%/pt-yr); thromboembolism 94.2% +/- 2.5% (1.62%/pt-yr); valve thrombosis 98.6 +/- 1.0% (0.46%/pt-yr); bleeding events 85.9% +/- 4.7% (2.77%/pt-yr); prosthetic valve endocarditis 98.6 +/- 0.9% (0.46%/pt-yr); nonstructural dysfunction 93.2 +/- 3.2% (1.38%/pt-yr); reoperation 87.1 +/- 5.3% (2.08%/pt-yr). Functional class according to NYHA was improved from preoperatively 72.05% in III or IV to 6-year postoperative 94.2% in I or II. CONCLUSION: The clinical performance of the TEKNA valve is quite satisfactory, with low incidence of valve-related complications. No structural deterioration has been observed. Further, the patients physical ability and quality of life were significantly improved.

Adolescent↗

PubMed1994

[Pregnancy in patients with heart valve prosthesis. A French retrospective cooperative study (155 cases)].

A French cooperative study of 155 pregnancies in 103 women with valvular prosthesis (95 mechanical, 60 bioprostheses including 27 bivalvular prostheses) is reported. Therefore, a total of 182 prostheses (108 mechanical and 74 bioprostheses) were exposed to the risk of pregnancy. The maternal outcome in the group of 108 mechanical prostheses was complicated by 16 thromboembolic events (TE) including 10 prosthetic valve thromboses which required emergency valve replacement in 4 cases, 6 systemic TE in 13 mitral, 2 aortic and 1 pulmonary mechanical prostheses. The TE were four times more frequent in patients on heparin than in those on oral anticoagulants. There were 4 deaths, 3 among the 10 prosthetic valve thromboses (one reoperation, two sudden deaths). Seven of the 74 bioprostheses were reoperated for degeneration on average 5.9 years after the initial operation but there were no deaths or TE. The outcome of pregnancy was 99 children (63%), 49 of which were born to mothers with mechanical prostheses (53%) and 50 to mothers with bioprostheses (80%) (p < 0.001). Seven of the children were born prematurely, all mothers being on anticoagulant therapy. The birth weight was over 400 grams heavier (3 kg versus 2.6 kg) in the bioprosthesis group (p < 0.05). The 20 spontaneous abortions (13%) were more common in patients on anticoagulants (17%) than in those without (2%) (p < 0.02). Congenital defects due to oral anticoagulants were rare (one certain case). There was one case of phocomelia, an abnormality which has never been described in this context. The 36 remaining pregnancies were still deaths (N = 5), abortion due to maternal death (N = 4), maternal complications (N = 8), therapeutic (N = 9) or voluntary abortions (N = 10) (28 mechanical and 8 bioprostheses).(ABSTRACT TRUNCATED AT 250 WORDS)

Abortion, Spontaneous↗

PubMed1990

In vivo experimental assessment of polytetrafluoroethylene trileaflet heart valve prosthesis.

This report summarizes the results of a series of experimental implantations of polytetrafluoroethylene valves in sheep. Twelve prostheses were implanted in the tricuspid position in weanling (3- to 4-month-old, 26 +/- 3 kg) sheep. The valve sizes were 23 mm (eight animals) and 25 mm (four animals). There were two early deaths, and the 10 survivors were killed in a stepwise manner to get a mineralization profile of the valve. There was one episode of acute thrombosis but no evidence of pulmonary thromboemboli in any animal. In all cases the leaflets were thin and unretracted, but in half of them one cusp or more were stiffened. One valve displayed a fixed outward eversion of the free margin of two leaflets. Macroscopic calcification was detected in seven specimens and always involved the commissural areas. Radiologic studies confirmed this calcium topography and revealed only one case of severe and diffuse mineralization. In most cases the cusps showed a grossly visible pannus that was thinner and less extensive than usually seen in bioprostheses. Examination with light microscopy disclosed a complete lack of infiltrating cells within the cuspal material (made of compact polytetrafluoroethylene). However, those parts of the prostheses made of expanded polytetrafluoroethylene (the material covering the valve frame and the sutures) did show infiltration by host cells and calcium. Mineralized lesions were of extrinsic type, involving fibrin and fibroelastic host tissue accumulated in the inflow aspect of the commissures. Examination with transmission electron microscopy disclosed electron-dense masses surrounded by an electron-lucent granular homogeneous material in areas of mineralization. The time-course evolution of the tissue calcium content shows a moderate mineralization rate (0.46 +/- 0.31 mg/gm of dry-weight material per week of follow-up) and a marginally significant positive correlation between calcium content and follow-up. Our results suggest that the polytetrafluoroethylene valves have a moderate overall calcification rate and that calcium deposits appear to be always related to the commissural region and to the presence of expanded polytetrafluoroethylene.

Animals↗

PubMed1996

Development of the Chitra tilting disc heart valve prosthesis.

BACKGROUND AND AIMS OF THE STUDY: The high prevalence of rheumatic valvular disease in the young population and the high cost of imports necessitated the development of an Indian valve. The development of a tilting disc prosthesis was successfully concluded in February 1995, when the third model completed its clinical trial. The tilting disc valve has an integrally machined cobalt alloy cage, an ultra high molecular weight polyethylene disc and a polyester suture ring. The choice of design was based on its superior hydrodynamics and the age distribution of patients, the majority of whom were below 30 years. The polymer-metal combination was selected for its extremely low wear rate and proven durability in the human body. MATERIALS AND METHODS: The hydrodynamic performance was tested under steady and pulsatile flow conditions. The accelerated durability of nine test valves was evaluated at 800-840 cycles/min for over 350 million cycles each. Size 23 mm valves mere implanted in the mitral position of five sheep. In a clinical trial, 306 patients with isolated mitral or aortic valve replacements were followed up for a total of 371 patient years (mean 1.37 years and range 0-4 years). RESULTS: The hydrodynamic performance was comparable to that of proven clinical models. The accelerated testing indicated lifetimes in excess of 50 years and the animal trials showed the valve to be safe. In the clinical trial, there was no incidence of structural failure or paravalvular leak. The linearized rate of late thromboembolism was 6.2%/patient-year (pty), anticoagulant related hemorrhage 0.54%/pty and infective endocarditis 0.54%/pty. At two years, the total actuarial survival was 89.5%. The higher incidence of thromboembolism and the very low incidence of anticoagulant related hemorrhage illustrate the difficulty in the management of anticoagulant therapy in a developing country, while the low incidence of endocarditis reflects their greater resistance to infection. CONCLUSION: These data clearly showed the valve to be safe and comparable to other similar valves in clinical use.

Adult↗