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PubMed1993

A comparison of outcomes in men 11 years after heart-valve replacement with a mechanical valve or bioprosthesis. Veterans Affairs Cooperative Study on Valvular Heart Disease.

BACKGROUND: Mechanical heart valves are durable but thrombogenic, and their use requires that the patient receive anticoagulants. In contrast, bioprosthetic valves are less thrombogenic, but they have limited durability because of tissue deterioration. METHODS: To compare the outcomes of patients who receive these two types of valves, we randomly assigned 575 men scheduled to undergo aortic-valve or mitral-valve replacement to receive either a mechanical or a bioprosthetic valve. The primary end points were death from any cause and any valve-related complication. RESULTS: During an average follow-up of 11 years, there was no difference between the two groups in the probability of death from any cause (11-year probability for mechanical valves, 0.57; for bioprostheses, 0.62; P = 0.57) or in the probability of any valve-related complication (0.65 and 0.69, respectively; P = 0.39). There was a much higher rate of structural valve failure among patients who received bioprosthetic valves (11-year probability, 0.15 for the aortic valves and 0.36 for the mitral valves) than among those who received mechanical valves (no valve failures; P < 0.001). However, this difference was offset by a higher rate of bleeding complications among patients with mechanical valves than among those with bioprosthetic valves (11-year probability, 0.42 and 0.26, respectively; P < 0.001) and by a greater frequency of peri-prosthetic valvular regurgitation among patients with mechanical mitral valves than among those with mitral bioprostheses (11-year probability, 0.17 and 0.09, respectively; P = 0.05). CONCLUSIONS: After 11 years, the rates of survival and freedom from all valve-related complications were similar for patients who received mechanical heart valves and those who received bioprosthetic heart valves. However, structural failure was observed only with the bioprosthetic valves, whereas bleeding complications were more frequent among patients who received mechanical valves.

Aortic Valve↗
PubMed2002

In vitro hydrodynamics of a decellularized pulmonary porcine valve, compared with a glutaraldehyde and polyurethane heart valve.

BACKGROUND: Hydrodynamic performance of a decellularized pulmonary porcine valve was evaluated with a computer versatile pulse duplicator and compared to glutaraldehyde fixated stentless porcine bioprosthesis and a polyurethane heart valve. METHODS: Decellularized pulmonary porcine matrices (Group I, n = 5) were treated chemically to become cell-free collagen matrices. The findings of this heart valve were compared with aortic glutaraldehyde treated porcine prostheses (Group II, n = 5) and polyurethane three leaflet valve prostheses (Group III, n = 1). Measurements were performed in 0.9% saline test fluid at room temperature. Measurements compared were closing time, closing volume, systemic pressure difference and energy losses. Each valve was measured 6 times with 70 beats/minute, a stroke volume of 70 ml corresponds to a cardiac output of 4.9 L/minute. RESULTS: Group I and group III showed no significant differences between parameters. The measured closing time was significantly different (p < 0.001) between group I and II, respectively 24.333 and 53.600 ms and group II and III respectively 53.600 and 24.000. Difference in closing volume was significant (p < 0.05) between groups II and I respectively 3.67 and 0.68 ms and group II and III respectively 3.67 and 0.71. Systolic mean pressure gradient was 18.25 +/- 1.04 mm Hg in group II which was significantly different (p < 0.001) from groups I and III, respectively 10.65 +/- 0.29 mm Hg and 7.70 +/- 0.30 mm Hg. CONCLUSIONS: Decellularized pulmonary porcine valves showed the same excellent performance as polyurethane valve prosthesis, which are superior to the investigated glutaraldehyde fixed xenograft.

Animals↗
PubMed1977

[Heart valve prosthesis in congenital heart defects].

The experience of 68 cases of prosthetic valve replacement for congenital heart diseases is presented. The majority of the cases were 57 patients with the Ebstein anomaly and tetralogy of Fallot. In the patients with the Ebstein anomaly the tricuspid valve was replaced, in those with the tetralogy of Fallot--a plastic enlargement of the pulmonary artery trunk and prosthetic replacement of the pulmonary valve with a ball valve or xeno-graft. Original techniques of radical correction of the Ebstein anomaly and tetralogy of Fallot are presented.

Adult↗
PubMed2003

Isolation of intact aortic valve scaffolds for heart-valve bioprostheses: extracellular matrix structure, prevention from calcification, and cell repopulation features.

Extracellular matrix (ECM) scaffolds isolated from valvulated conduits can be useful in developing durable bioprostheses by tissue engineering provided that anatomical shape, architecture, and mechanical properties are preserved. As evidenced by SEM, intact scaffolds were derived from porcine aortic valves by the combined use of Triton X-100 and cholate (TRI-COL) or N-cetylpyridinium (CPC) and subsequent nucleic acid removal by nuclease. Both treatments were effective in removing most cells and all the cytomembranes, with preservation of (1) endothelium basal membranes, (2) ECM texture, including the D-periodical interaction of small proteoglycans with normally D-banded collagen fibrils, and (3) mechanical properties of the treated valves. Ultrastructural features agreed with DNA, hexosamine, and uronic acid biochemical estimations. Calcification potential, assessed by a 6-week rat subdermal model, was significantly reduced by TRI-COL/nuclease treatment. This was not true for CPC only, despite better proteoglycan preservation, suggesting that nucleic acids also are involved in calcification onset. Human fibroblasts, used to repopulate TRI-COL samples, formed mono- or multilayers on surfaces, and groups of cells also were scattered within the valve leaflet framework. A biocompatible scaffolds of this kind holds promise for production of durable valve bioprostheses that will be able to undergo probable turnover and/or remodeling by repopulating recipient cells.

Animals↗
PubMed1995

A working cardiac valve phantom for radiographic assessment of prosthetic heart valves.

RATIONALE AND OBJECTIVES: A working valve phantom (WVP) that both exercises the valve occluder and simulates movements of the mitral annulus is described. It was designed to develop a method for radiographic detection of a single broken leg of the two-legged Björk-Shiley convexo-concave (C/C) heart valve outlet strut. METHODS: The WVP consists of a pneumatically driven left ventricular assist device immersed in 22 cm of water. Left ventricular assist device annulus movements are generated by systolic turgor and diastolic relaxation of the aortic outflow graft within limits set by the holding fixture design. RESULTS: WVP images were comparable in attenuation, valve motion, and diagnostic sensitivity to clinical C/C valve images and were effective in assessing leaflet excursions in another valve model. Techniques developed in the WVP have proved successful in the clinical detection of C/C valves that have a single broken leg but that show normal function in all other tests. CONCLUSION: The WVP can be a useful tool for developing refined radiographic assessments of prosthetic heart valves.

Heart Valve Prosthesis↗
PubMed1998

Blood rheology in patients with native heart valve disease and after valve replacement.

Patients with heart valve disease have rheologic abnormalities that are more pronounced in double valve disease than in mitral or aortic valve disease; after valve replacement surgery, the degree of rheologic abnormality is more pronounced in patients with mechanical and biological prostheses than in those with homografts and pulmonary autografts. Rheologic abnormalities seen in these patients might be related to the different incidences of thromboembolism in the presence of various valve defects and various types of prostheses.

Adolescent↗
PubMed2004

[Preparation of heart valve scaffold and cell seeding].

To prepare scaffolds for heart valve tissue engineering, porcine heart valves were treated with varied concentrations of trypsin for 32, 56, 80 and 104 h or followed with DNase. And then the structure of acellular valves was observed under light microscope, scanning and transmission electron microscope. Porcine endothelial cells, human endothelial cells, and canine myofibroblasts were reseeded onto the acellularized porcine heart valve scaffolds once a day for 3 days. The valves were analyzed by immunohistochemical staining and electron microscopy. Results show that all endothelial cells and the majority of interstitial cells were removed from the heart valves after digestion with trypsin for 104 h, and the collagen fiber structure remains intact, but the space between collagen fibers increased slightly. Incubation with trypsin for 80 h and then with DNase almost removed all cells, and the collagen fiber structure and the space between the fibers remain intact. After reseeding, human endothelial cells almost fully cover the valve scaffold surface as shown by H-E staining and platelet endothelial cell adhesion molecules (PECAM-1) staining. Xenogeneic porcine endothelial cells also adhered to and grew on the scaffolds. As shown by H-E staining and actin staining, canine myofibroblasts not only adhered to the surface of valve scaffold but also migrated to the inner part of matrix after one week culture. These results suggest that the digestion of porcine heart valves with trypsin combining with DNase is a suitable method to remove cells. The acellular porcine heart valve scaffolds have a quite favorable biocompatibility with human and porcine endothelial cells as well as canine myofibroblasts.

Animals↗
PubMedDate not supplied

Application of stereolithography for scaffold fabrication for tissue engineered heart valves.

A crucial factor in tissue engineering of heart valves is the functional and physiologic scaffold design. In our current experiment, we describe a new fabrication technique for heart valve scaffolds, derived from x-ray computed tomography data linked to the rapid prototyping technique of stereolithography. To recreate the complex anatomic structure of a human pulmonary and aortic homograft, we have used stereolithographic models derived from x-ray computed tomography and specific software (CP, Aachen, Germany). These stereolithographic models were used to generate biocompatible and biodegradable heart valve scaffolds by a thermal processing technique. The scaffold forming polymer was a thermoplastic elastomer, a poly-4-hydroxybutyrate (P4HB) and a polyhydroxyoctanoate (PHOH) (Tepha, Inc., Cambridge, MA). We fabricated one human aortic root scaffold and one pulmonary heart valve scaffold. Analysis of the heart valve included functional testing in a pulsatile bioreactor under subphysiological and supraphysiological flow and pressure conditions. Using stereolithography, we were able to fabricate plastic models with accurate anatomy of a human valvular homograft. Moreover, we fabricated heart valve scaffolds with a physiologic valve design, which included the sinus of Valsalva, and that resembled our reconstructed aortic root and pulmonary valve. One advantage of P4HB and PHOH was the ability to mold a complete trileaflet heart valve scaffold from a stereolithographic model without the need for suturing. The heart valves were tested in a pulsatile bioreactor, and it was noted that the leaflets opened and closed synchronously under subphysiological and supraphysiological flow conditions. Our preliminary results suggest that the reproduction of complex anatomic structures by rapid prototyping techniques may be useful to fabricate custom made polymeric scaffolds for the tissue engineering of heart valves.

Bioprosthesis↗
PubMed2005

The independent role of cyclic flexure in the early in vitro development of an engineered heart valve tissue.

Tissue engineered heart valves (TEHV) are being investigated as an alternative to current non-viable prosthetic valves and valved conduits. Studies suggest that pulse duplicator bioreactors can stimulate TEHV development. In the current study, a model system was used to determine if cyclic flexure, a major mode of heart valve deformation, has independent effects on TEHV cell and extracellular matrix (ECM) development. Ovine vascular smooth muscle cells (SMC) were seeded for 30 h onto strips of non-woven 50:50 polyglycolic acid (PGA) and poly-L-lactic acid (PLLA) scaffold. After 4 days of incubation, SMC-seeded and unseeded scaffolds were either maintained under static conditions (static group), or subjected to unidirectional cyclic three-point flexure at a physiological frequency and amplitude in a bioreactor (flex group) for 3 weeks. After seeding or incubation, the effective stiffness (E) was measured, with SMC-seeded scaffolds further characterized by DNA, collagen, sulfated glycosaminoglycan (S-GAG), and elastin content, as well as by histology. The seeding period was over 90% efficient, with a significant accumulation of S-GAG, no significant change in E, and no collagen detected. Following 3 weeks of incubation, unseeded scaffolds exhibited no significant change in E in the flex or static groups. In contrast, E of SMC-seeded scaffolds increased 429% in the flex group (p<0.01) and 351% in the static group (p<0.01), with a trend of increased E, a 63% increase in collagen (p<0.05), increased vimentin expression, and a more homogenous transmural cell distribution in the flex versus static group. Moreover, a positive linear relationship (r2=0.996) was found between the mean E and mean collagen concentration. These results show that cyclic flexure can have independent effects on TEHV cell and ECM development, and may be useful in predicting the mechanical properties of TEHV constructed using novel scaffold materials.

Animals↗
PubMed1994

Structural alterations in heart valves during left ventricular pressure overload in the rat.

BACKGROUND: Heart valves are an important denominator of the function of the heart but detailed studies of structural alterations of heart valves after hemodynamic changes are lacking. EXPERIMENTAL DESIGN: Structural alterations of heart valves, including DNA synthesis, collagen mRNA, and protein concentration were measured in heart valves of Wistar Kyoto (WKY) rats with acute left ventricular pressure overload, created by intrarenal aortic ligation (AL, N = 18) as well as in heart valves of age-matched spontaneously hypertensive rats, a model of chronic hypertension (N = 18). SHAM aortic ligation and normal WKYs (N = 17 and N = 17) served as controls. All animals received 5'bromo-2' deoxyuridine, during the last 7 days of the experiment, in a dose of 2.4 mg/kg.day. RESULTS: The cumulative labeling fraction (LF) in the mitral valve of AL animals was 47.8 +/- 5.2% as compared with 9.4 +/- 2.6% in SHAM animals (mean +/- SEM, p < 0.01). The LF in the aortic valve of AL animals was 33.3 +/- 2.9% as compared with 7.7 +/- 0.7% in SHAM animals (p < 0.01). The LF in the tricuspid valve was also significantly increased: 11.3 +/- 1.4% in AL versus 5.8 +/- 0.7% in SHAM (p < 0.01). Labeling fractions of heart valves in SHR were not increased as compared with normal WKY. The total collagen concentration in the three heart valves, measured by the hydroxyproline assay, did not change. The mRNA amounts of both collagen type I and III, detected by in situ hybridization, were increased in the heart valves of AL and spontaneously hypertensive animals as compared with the two control groups (SHAM and WKY). In all 3 heart valves, interstitial cells were vimentin-positive, but desmin-negative. A fraction of interstitial cells showed alpha-smooth muscle actin positivity. This immunophenotype did not change during pressure overload. CONCLUSIONS: Heart valves have the capacity to adapt to acute pressure overload, by means of DNA synthesis and increased collagen turnover. The increase in LF in the normotensive tricuspid valve suggests a role for an additional circulating factor. A constant fraction of the interstitial heart valve cells consists of myofibroblasts.

Animals↗
PubMed1999

Expanding the use of total mitral valve preservation in combination with implantation of the CarboMedics heart valve prosthesis.

BACKGROUND: Preservation of the mitral valve and subvalvular apparatus was introduced into the clinic in the early sixties, but for two decades the standard technique for mitral valve replacement included excision of both leaflets and their attached chordae tendineae. Lately, increased emphasis has again been placed on retention of the mitral subvalvular apparatus during valve replacement because of its role on left ventricular function. METHODS: We have preserved the valvular and subvalvular mitral apparatus, when possible, in connection with mitral valve replacement during the last seven years and the present investigation (partly prospective and partly retrospective) was done with the aim of making up the results of our mitral preservation technique. In the period between January 1990 and December 1995, 30% of the patients who underwent mitral valve replacement had complete retention of all mitral tissue. In 1996, the percentage had increased to 50, and during the first seven months of 1997, 70% of the patients had complete retention of all mitral tissue. Since January 1997, we have exclusively used the CarboMedics mitral heart valve prosthesis. A total of 56 patients were identified to have had a CarboMedics heart valve prosthesis implanted. There were 33 men and 23 women with a mean age of 63 years, range 23-77 years. Coronary bypass was a concomitant procedure in 22 patients. In seven patients, both the mitral and aortic valves were replaced. A severely altered valve with thickened and or calcified leaflets, stenotic leaflets, or shortened, retracted and thickened chordae tendineae were not a contraindication for the procedure. Calcified plaques were removed. Adhesion between anterior and posterior leaflets was treated with sharp dissection. Valve and subvalvular tissue were preserved. The leaflets were reefed within the valve-sutures and compressed between the sewing ring and the native annulus when implanting the valve prosthesis. Chordal tension on the ventricle was thereby maintained and the chordae pulled away from the valve effluent. Echocardiography with measurement of ejection-fraction was performed preoperatively during the postoperative course in case of cardiac problems and on a routine basis 1 month after surgery and at various intervals when the patient was seen in the outpatient clinic. Left ventricular outflow tract gradients were measured during the postoperative course in case of cardiac problems and routinely 1 month postsurgically. RESULTS: Five patients died in the postoperative period and one patient had transient neurological symptoms. In none of the patients was death or transient neurological symptoms a consequence of the retention of mitral leaflets with subvalvular apparatus. The remaining 51 patients were all alive at follow-up. Postoperative echocardiography demonstrated a preserved left ventricular function and a left ventricular outflow tract without obstruction. CONCLUSIONS: We find that the described technique in combination with implantation of a CarboMedics heart valve prosthesis is very useful even in patients with a severely altered valve, when preserving the mitral leaflets with subvalvular apparatus during valve replacement. The technique is without procedure related complications and preserves left ventricular function without obstructing the left ventricular outflow tract.

Adult↗
PubMed2005

Comparison of the efficacy and safety profiles of intravenous vitamin K and fresh frozen plasma as treatment of warfarin-related over-anticoagulation in patients with mechanical heart valves.

Patients on warfarin for mechanical heart valves are at increased risk for thromboembolic events and intracranial hemmorhage. In current guidelines, a low dose of vitamin K is the recommended treatment for moderate over-anticoagulation based on studies in which only minority patients participating had mechanical heart valves. We performed a randomized controlled trial to compare the efficacy and safety profile of low-dose intravenous vitamin K and fresh frozen plasma (FFP) for patients with mechanical heart valves and mild to moderate over-anticoagulation (international normalized ratio [INR] 4 to 7). In a 24-month period, we randomized 102 patients to (1) vitamin K or (2) FFP. The baseline INR at presentation between the vitamin K group and the FFP group was 4.61 +/- 0.007 vs 4.78 +/- 0.07 (p = 0.11). Six hours after treatment, patients in the FFP group had a significantly lower mean INR compared with the vitamin K group (2.75 +/- 0.06 vs 3.44 +/- 0.10, p = 0.01). No patient in both groups had over-correction (INR < 2). One week later, there was no significant difference in mean INR between both groups (2.7 +/- 0.11 vs 2.56 +/- 0.12, p = 0.41). Fifty-eight percent of patients in the FFP group and 51% in the vitamin K group had an INR within the target range. There were no adverse reactions or outcomes in both groups. In conclusion, intravenous low-dose vitamin K is a safe alternative to FFP infusion for warfarin overdose in patients with mechanical heart valves.

Anticoagulants↗
PubMed1989

Quality of life and mechanical heart valve sound.

Most currently used mechanical heart valve prostheses generate a distinct metallic sound at closure. Since this sound is often well audible to many patients it can significantly affect their quality of life after heart valve replacement. In this study of surviving patients after heart valve replacement with three types of Björk-Shiley valves (Shiley Inc., Irvine, Ca) one third of the patients claimed that they were in certain situations disturbed by the sound. Several factors were found to be of importance for the perception of mechanical heart valve noise, including age, sex, location of valve, configuration of the thorax, hearing ability and environmental background noise. Preoperative patient information can be of vital importance to avoid postoperative adverse patient reactions.

Aged↗
PubMed1988

Randomised comparison of two intensities of oral anticoagulant therapy after tissue heart valve replacement.

After tissue heart valve replacement 108 patients were randomised to standard anticoagulant control with rabbit brain thromboplastin (Dade C reagent, therapeutic range 18-24 s; international normalised ratio 2.5-40) and 102 to a less intensive regimen controlled with human brain thromboplastin (Manchester Comparative Reagent, therapeutic range 26-30 s; INR 2.0-2.25). Treatment was continued for three months, outcome measures being major or minor embolism or haemorrhage. 2 patients in each group had major embolic events and 11 in each group had minor embolic events. The 95% confidence intervals on the differences are -3.4% to 3.2% for major embolism and -9.3% to 8.2% for minor embolism. Haemorrhagic complications were significantly more frequent with standard treatment (15 patients) than with the less intensive regimen (6 patients); and of the 5 patients with major haemorrhagic complications, all were in the standard treatment group, again a significant difference. The less intensive regimen is thus no less effective and safer than standard anticoagulant therapy in patients with tissue heart valve replacement.

Administration, Oral↗
PubMed2006

Observation and quantification of cavitation on a mechanical heart valve with an electro-hydraulic total artificial heart.

In previous studies, we investigated the cavitation phenomenon in a mechanical heart valve using an electro-hydraulic total artificial heart. With this system, a 50% glycerin solution kept at 37 degrees C was used as the working fluid. We reported that most of the cavitation bubbles were observed near the valve stop and were caused by the squeeze flow. However, in these studies, the effect of the partial pressure of CO(2) on the mechanical heart valve cavitation was neglected. In this study, in order to investigate the effect of the partial pressure of CO(2) on mechanical heart valve cavitation using an electro-hydraulic total artificial heart, we controlled the partial pressure of the CO(2) in vitro. A 25-mm Medtronic Hall valve was installed in the mitral position of an electro-hydraulic total artificial heart. In order to quantify the mechanical heart valve cavitation, we used a high-speed camera. Even though cavitation intensity slightly increased with increases in the PCO(2) at heart rates of 60, 70 and 100 bpm, throughout the experiment, there was no significant difference between the PCO(2) and cavitation intensity.

Electricity↗
PubMedDate not supplied

Penetration of gentamicin into heart valves, subcutaneous and muscular tissue of patients undergoing open heart surgery.

Concentrations of gentamicin in plasma, heart valves, subcutaneous tissue and muscle were determined in 38 patients undergoing open heart surgery. Gentamicin reached peak levels in plasma and tissue within 60 min after a 5 min intravenous bolus injection of 1.5 mg/kg body weight. Subcutaneous and muscle concentrations varied between 0.51 microgram/g and 2.1 microgram/g. Gentamicin peak concentrations in cardiac valvar tissue wre 3.6 mug/g between 2 and 5 hours after administration; gentamicin heart valve concentrations varied between 1.2 microgram/g and 1.59 microgram/g. Gentamicin tissue concentrations during open heart surgery are high enough to inhibit most Klebsiella/Enterobacter and Staphylococcus aureus and epidermidis strains. However Gentamicin heart valve concentrations do not exceed 1.5 microgram/g for more than 1 h, which may explain treatment failures of patients with endocarditis.

Cardiac Surgical Procedures↗
PubMed2006

Bmp2 instructs cardiac progenitors to form the heart-valve-inducing field.

A hallmark of heart-valve development is the swelling and deposition of extracellular matrix in the heart-valve region. Only myocardium overlying this region can signal to underlying endothelium and cause it to lose cell-cell contacts, delaminate, and invade the extracellular space abutting myocardium and endocardium to form endocardial cushions (EC) in a process known as epithelial to mesenchymal transformation (EMT). The heart-valve myocardium expresses bone morphogenetic protein-2 (Bmp2) coincident with development of valve mesenchyme. BMPs belong to the transforming growth factor beta superfamily (TGF-beta) and play a wide variety of roles during development. We show that conditional ablation of Bmp2 in cardiac progenitors results in cell fate changes in which the heart-valve region adopts the identity of differentiated chamber myocardium. Moreover, Bmp2-deficient hearts fail to induce production and deposition of matrix at the heart-valve-forming region, resulting in the inability of the endothelium to swell and impairing the development of ECs. Furthermore, in collagen invasion assays, Bmp2 mutant endothelium is incapable of undergoing EMT, and addition of BMP2 protein to mutant heart explants rescues this phenotype. Our results demonstrate that Bmp2 is both necessary and sufficient to specify a field of cardiac progenitor cells as the heart-valve-inducing region amid developing atria and ventricles.

Animals↗