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At least 19 recordsLinked to original sources
PubMed1987

[Hemolysis indicators in the evaluation of the function of artificial heart valves after heart valve prosthesis].

Hemolysis of blood was studied in two groups of patients: the main group consisted of 75 patients with mitral, aortal and two-valves prostheses; a control group had 15 patients with rheumatic valve defects without prostheses. It was shown that hemolysis was minimal in patients with a satisfactory function of prostheses. It was higher after double prostheses and especially in patients with dysfunction of the valves. Lactate dehydrogenase is thought to be the most important and reliable test for the assessment of the hemolysis degree.

Adult↗
PubMed1998

Principal stress analysis in LDA measurement of the flow field downstream of 19-mm Sorin Bicarbon heart valve.

Heart valve replacement has become, since many years, a common surgical practice. Along with the improvement that the patients' health has derived from it, however, a certain amount of risk could not be avoided, bound to the inevitable hemodynamic disturbances that an artificial device generates. A major shortcoming, often reported, is the formation of thrombus on the edge of the prosthetic valve, with a possible obstruction of the orifices through which blood should normally flow undisturbed. Hemolysis is another possible consequence of the implantation of a mechanical heart valve, generally correlated to turbulence downstream of prosthetic heart valves (PHV). As it is agreed upon by many researchers, the risk of thrombogenicity or hemolysis is higher in those valves that are more subject to promote turbulence and flow separation in the flow through them. In the following paper, we present a study of the turbulence-related shear stress downstream of a bileaflet valve of minimum size (19 mm external diameter) Sorin Bicarbon. This size was chosen, accordingly to the Food & Drug Administration (FDA) draft guidance suggestion to investigate the worst case in turbulence promoted by PHVs, in order to have the highest velocity gradients and shear stresses for the FDA-stated cardiac output (6 1/min), related to maximum Reynolds number conditions. Velocity data were collected with the two-dimensional laser Doppler anemometry (LDA) technique; whereas this approach does not investigate directly all three components of the flow field, in the present case (bileaflet valves) it is not a limitation to the assessment of the maximum turbulence shear stress (TSS), thanks to the two-dimensional flow nature downstream of bileaflet models. Data taken in coincident mode were elaborated in order to determine the maximum shear stress in the measured points in the flow field, using the 2D Principal Stress Analysis (PSA). The consequences of a variable principal normal stress direction all along the measured profile will be illustrated in terms of differences between measured and maximum shear stresses. Results show the need to estimate the maximum values for the TSS and the direction along which it is obtained to correctly define the turbulent flow field downstream of PHVs.

Blood Flow Velocity↗
PubMed2003

Acellularized porcine heart valve scaffolds for heart valve tissue engineering and the risk of cross-species transmission of porcine endogenous retrovirus.

OBJECTIVE: Acellularized porcine heart valve scaffolds have been successfully used for heart valve tissue engineering, creating living functioning heart valve tissue. However, there is concern about the possibility of porcine endogenous retrovirus transmission. In this study we investigated whether acellularized porcine heart valve scaffold causes cross-species transmission of porcine endogenous retrovirus in a sheep model. METHODS: Acellularized porcine pulmonary valve conduits (n = 3) and in vitro autologous repopulated porcine pulmonary valve conduits (n = 5) were implanted into sheep in the pulmonary valve position. Surgery was carried out with cardiopulmonary bypass support. The animals were killed 6 months after the operation. Blood samples were collected regularly up to 6 months after the operation and tested for porcine endogenous retrovirus by means of polymerase chain reaction and reverse transcriptase-polymerase chain reaction. In addition, explanted tissue-engineered heart valves were tested for porcine endogenous retrovirus after 6 month in vivo. RESULTS: Porcine endogenous retrovirus DNA was detectable in acellularized porcine heart valve tissue. However, 6 months after implantation of in vitro and in vivo repopulated acellularized porcine heart valve scaffolds, no porcine endogenous retrovirus sequences were detectable in heart valve tissue and peripheral blood. CONCLUSION: Acellularized porcine matrix scaffolds used for creation of tissue-engineered heart valves do not transmit porcine endogenous retrovirus.

Animals↗
PubMed2005

Flow-induced platelet activation in a St. Jude mechanical heart valve, a trileaflet polymeric heart valve, and a St. Jude tissue valve.

Polymer heart valves have been under investigation since the 1960s, but their success has been hampered by an overall lack of durability mainly due to calcification of the leaflets and a relatively high rate of thromboembolic complications. A new polymer (Quatromer) trileaflet design was tested for its thrombogenic potential and was compared to that of existing prosthetic heart valves routinely implanted in patients: a St. Jude Medical bileaflet mechanical heart valve (MHV) and a St. Jude porcine bioprosthetic tissue valve. The valves were mounted in a left ventricular assist device and the procoagulant activity of the platelets was measured using a platelet activation state (PAS) assay. The PAS measurements indicated that the platelet activation level induced by the polymeric valve was very similar to that induced by the St. Jude Medical MHV and the St. Jude tissue valve. No significant difference was observed between the three valves, indicating that they have a comparable thrombogenic potential.

Bioprosthesis↗
PubMed2003

Glycosaminoglycan-degrading enzymes in porcine aortic heart valves: implications for bioprosthetic heart valve degeneration.

BACKGROUND AND AIM OF THE STUDY: Glutaraldehyde (GA)-fixed aortic valves used in heart valve replacement surgery have limited durability due to tissue degeneration and calcification. Despite their structural and functional importance, very little is known about the fate of glycosaminoglycans (GAGs) within the extracellular matrix of bioprosthetic heart valves. The study aim was to investigate the stability of GAGs in GA-fixed tissues and to identify enzymatic mechanisms that may be responsible for GAG degeneration. METHODS: Porcine aortic valve cusps were fixed with GA and implanted subdermally in rats for 21 days. Fresh, fixed and explanted cusps were analyzed for GAG content by hexosamine determination, and GAG-degrading enzyme activity was evaluated using zymography. GAG classes in fresh cusps were also assessed by flurorophore-assisted carbohydrate electrophoresis. Fresh and GA-fixed cusps were also exposed in vitro to hyaluronidase and chondroitinase in order to test the susceptibility of cusp GAGs towards enzymatic degradation. RESULTS: Native aortic cusps contained -3.5% GAGs by dry weight, consisting of hyaluronic acid, chondroitin sulfate and dermatan sulfate. Significantly lower GAG levels were found in aortic cusps after fixation with GA, and even lower levels were found after subdermal implantation in rats. GAG levels in GA-fixed cusps were also significantly reduced by in-vitro incubation with hyaluronidase and chondroitinase. Novel GAG-degrading enzymes were detected in considerable levels in native cusps, in lower levels in GA-fixed cusps and significantly increased levels after subdermal implantation of GA-fixed cusps. CONCLUSION: The combined action of active GAG-degrading enzymes and the failure of GA to stabilize GAGs towards enzymatic digestion may contribute significantly to bioprosthetic heart valve degeneration and subsequent structural failure.

Animals↗
PubMed1975

Age-dependent changes of heart valves and heart size.

The mode and extent of the regressions of heart valves, valvular rings, and tendon chords, as well as the size of atria and ventricles in 316 hearts of different age groups (macroscopically normal at autopsy), were studied. With increasing age, the valves showed marked thickening and loss of elasticity. Deposition of lipoids and calcification occur to a variable extent in the valvular tissue and rings; Valve size shows a change of minor degree, but tendon chords and papillary muscles shorten in old age. The diameters of the atria, mitral, tricuspid, pulmonary, and aortic rings increase continuously up to the 9th decade of life. The width and length of the ventricles show minor alterations in size. In old age, heart weight increases.

Adolescent↗
PubMed1998

Spectral analysis of heart valve sound for detection of prosthetic heart valve diseases.

The spectral analysis of heart valve sound is a noninvasive diagnostic method known to be useful in evaluating the state of the heart valve function. This may provide early detection of valve calcification, thrombus or destruction, since previous studies have shown that the dominant frequency peak moved to a high frequency area when natural heart valve leaflets were calcified, stiffened or destroyed. However, it is important for a heart valve sound diagnostic system to find a proper spectral analysis method on phonocardiography. Until now, conventional frequency analyses such as the Fourier transform or autoregressive spectral estimation technique have been used to estimate spectral components of a phonocardiogram, but they are inappropriate because the signal frequency is assumed to remain constant during the transform interval. To overcome this problem, in this study, FOS (Fast Orthogonal Search) & MUSIC (MUltiple SIgnal Classification), which both appeared suitable for the analysis of biological data, were applied to prosthetic heart valve sound as the new heart valve sound spectral analysis methods. Five subjects with normally functioning mechanical heart valves and a patient with a malfunctioning one were selected to collect the heart valve sound signals. As a result, the second dominant peak frequency proved to be important along with the first dominant peak frequency in identifying the valve function. This study showed that the new heart valve sound spectral analysis method presented in this paper may be an effective method in heart valve sound analysis. Further study using this system in a large population of patients will aid in providing a diagnostic method in the early detection of valve failure.

Female↗
PubMed1980

[beta-Thromboglobulin in plasma in patients with heart-valve diseases and with prosthetic heart valves (author's transl)].

In each 50 patients with rheumatic heart valve diseases and after implantation of prosthetic heart valves and in 20 patients with bioprostheses, beta-thromboglobulin (beta-TG) in plasma was determined. In all cases beta-TG was significantly elevated above the normal range. The levels of beta-TG lay in patients with bioprostheses lower than in the other groups. Bioprostheses are less damaging the thrombocytes than prosthetic heart valves.

Beta-Globulins↗
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↗
PubMedDate not supplied

[Similarities in morphologic changes in heart valves in acquired heart defects of noninflammatory etiology and in damaged menisci without a history of trauma].

Histologic, histochemical and ultrastructural analyses were performed of the leaflets of all four heart valves in 50 subjects with acquired heart defects of noninflammatory etiology and 88 surgically removed damaged menisci without trauma anamnesis. On the basis of the detailed analysis some morphologic similarities were found in the heart valves and menisci such as myxomatous degeneration as the main pathologic lesion, lack of blood vessels in the altered tissues which point to noninflammatory nature of the lesion, similarity in nourishment by diffusion, degradation of the collagenous fibres which present the main histologic structure and the increased accumulation of acid mucopolysacharrides at the site of their degradation as well as the increased number of fibroblasts, that is, chondroid cells which are considered to excrete acid mucopolysacharrides. Sometimes these changes are hardly identify clinically, especially in meniscal diseases which could simulate rheumatic disease.

Adolescent↗
PubMed2006

Characterizing nanoscale topography of the aortic heart valve basement membrane for tissue engineering heart valve scaffold design.

A fully effective prosthetic heart valve has not yet been developed. A successful tissue-engineered valve prosthetic must contain a scaffold that fully supports valve endothelial cell function. Recently, topographic features of scaffolds have been shown to influence the behavior of a variety of cell types and should be considered in rational scaffold design and fabrication. The basement membrane of the aortic valve endothelium provides important parameters for tissue engineering scaffold design. This study presents a quantitative characterization of the topographic features of the native aortic valve endothelial basement membrane; topographical features were measured, and quantitative data were generated using scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), and light microscopy. Optimal conditions for basement membrane isolation were established. Histological, immunohistochemical, and TEM analyses following decellularization confirmed basement membrane integrity. SEM and AFM photomicrographs of isolated basement membrane were captured and quantitatively analyzed. The basement membrane of the aortic valve has a rich, felt-like, 3-D nanoscale topography, consisting of pores, fibers, and elevations. All features measured were in the sub-100 nm range. No statistical difference was found between the fibrosal and ventricular surfaces of the cusp. These data provide a rational starting point for the design of extracellular scaffolds with nanoscale topographic features that mimic those found in the native aortic heart valve basement membrane.

Animals↗