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At least 649 records · Page 36Linked to original sources
PubMed2000

Transpecies heart valve transplant: advanced studies of a bioengineered xeno-autograft.

BACKGROUND: Tissue engineering approaches utilizing biomechanically suitable cell-conductive matrixes should extend xenograft heart valve performance, durability, and growth potential to an extent presently attained only by the pulmonary autograft. To test this hypothesis, we developed an acellular, unfixed porcine aortic valve-based construct. The performance of this valve has been evaluated in vitro under simulated aortic conditions, as a pulmonary valve replacement in sheep, and in aortic and pulmonary valve replacement in humans. METHODS: SynerGraft porcine heart valves (CryoLife Inc, Kennesaw, GA) were constructed from porcine noncoronary aortic valve cusp units consisting of aorta, noncoronary aortic leaflet, and attached anterior mitral leaflet (AML). After treatment to remove all histologically demonstrable leaflet cells and substantially reduce porcine cell-related immunoreactivity, three valve cusps were matched and sewn to form a symmetrical root utilizing the AML remnants as the inflow conduit. SynerGraft valves were evaluated by in vitro hydrodynamics, and by in vivo implants in the right ventricular outflow tract of weanling sheep for up to 336 days. Cryopreserved allograft valves served as control valves in both in vitro and in vivo evaluations. Valves were also implanted as aortic valve replacements in humans. RESULTS: In vitro pulsatile flow testing of the SynerGraft porcine valves demonstrated excellent valve function with large effective orifice areas and low gradients equivalent to a normal human aortic valve. Implants in sheep right ventricular outflow tracts showed stable leaflets with up to 80% of matrix recellularization with host fibroblasts and/or myofibroblasts, and with no leaflet calcification over 150 days, and minimal deposition at 336 days. Echocardiography studies showed normal hemodynamic performance during the implantation period. The human implants have proven functional for over 9 months. CONCLUSIONS: A unique heart valve construct has been engineered to achieve the equivalent of an autograft. Short-term durability of these novel implants demonstrates for the first time the possibility of an engineered autograft.

Animals↗
PubMed1994

[Redo valve replacement for primary tissue failure of bioprosthetic heart valve].

We evaluated long-term results of valve replacement with bioprosthesis in 59 patients. Freedom from primary tissue failure and reoperation declined more than seven years after valve replacement. Seven patients underwent repeat operations because of primary tissue failure in our hospital. Their ages ranged from 32 to 54 years, two cases were male and five were female. At repeat operation, mechanical valve prosthesis were implanted to mitral position in all seven patients, tricuspid annuloplasty was added in five patients, and aortic valve replacement was added in one patients. The New York Heart Association (NYHA) functional classifications were grade II for 1 patient, III for 1, and IV for 5 preoperatively. Five patients had severe pulmonary hypertension preoperatively, and three of them were died after operation. The removed bioprostheses showed tears, perforations or calcifications of cusps and commissural detachments.

Adolescent↗
PubMed2004

The Carbomedics aortic heart valve prosthesis: a review.

The Carbomedics bileaflet mechanical prosthesis was introduced in 1986 and until now more than 500,000 valves have been implanted. The aim of this study was to review the papers published on the Carbomedics aortic heart valve prosthesis. The Carbomedics prosthesis has a solid pyrolite carbon housing and flat leaflets of pyrolite carbon coated graphite that is impregnated with tungsten. The pyrolite carbon housing is reinforced by an outer stiffening ring composed of titanium which virtually eliminates the risk of leaflet escape. The design further enables valve rotation after implantation. The standard aortic valve prosthesis has the sewing cuff located at the outflow level of the valve cylinder. A high-performance valve, the Carbomedics TopHat valve for supraannular implantation, is a standard aortic valve prosthesis where the sewing cuff has been transferred to the inflow level of the valve cylinder. A 2 size increase in valve size can be achieved by using the TopHat valve which is very important in patient-prosthesis mismatch. With the recommended international normalised ratio (INR) level for the Carbomedics aortic heart valve prosthesis the rate of embolic and bleeding events are low. Thrombosis of a Carbomedics aortic heart valve prosthesis is rarely seen and is the result of inappropriate anticoagulation without pannus formation. The incidence of prosthetic endocarditis is very low and this is also the case for noninfectious paravalvular leakage necessitating reoperation. Intrinsic dysfunction and/or structural failure has never been reported. The total absence of intrinsic dysfunction and structural failure of the Carbomedics aortic valve prosthesis is a great advantage. Further the complication rate is very low. The TopHat, the supraannular version of this prosthesis, is a perfect solution in patient-prosthesis mismatch.

Anticoagulants↗
PubMed2000

The Ultracor tilting disc heart valve prosthesis in the aortic position: mid-term follow up.

BACKGROUND AND AIM OF THE STUDY: The Ultracor valve is a recent introduction in the evolution of the tilting disc valve. This report summarizes a single surgeon's experience with the valve in the aortic position over a nine-year period. METHODS: Between 1990 and 1999, 94 patients received an Ultracor heart valve prosthesis in the aortic position. Forty-five patients (48%) had associated procedures, of which 32 (34%) were coronary artery grafts. Mean follow up was 2.6 years; total follow up was 229 patient-years. Follow up was 100% complete. RESULTS: The actuarial survival rate, including operative mortality rate, at five years was 82%. Actuarial freedom from valve-related death was 96% at five years. The linearized complication rate was 1.7%/year for late valve-related mortality, 1.7%/year for thromboembolism, 2.2%/year for anticoagulant-related hemorrhage (ACH), 1.3%/year for prosthetic valve endocarditis (PVE), and 1.7%/year for reoperation. The estimates of actuarial freedom from complications at five years were thromboembolism 89%, ACH 90%, PVE 96% and reoperation 96%. No structural failure or valve thrombosis was observed. CONCLUSION: Our experience over nine years showed the Ultracor heart valve prosthesis in the aortic position to be comparable with other currently evaluated mechanical heart valves in terms of durability and clinical results. Further study in this area should concentrate on the impact of valve type on left ventricular recovery post-implantation to provide additional information to the surgeon when selecting a valve from the plethora of choices available.

Adult↗
PubMed1982

Dental treatment and management of a patient with a prosthetic heart valve.

The American Heart Association committee recognizes that their regimens do not cover all situations. Each patient should be evaluated individually. The necessity for parenteral therapy or oral erythromycin to continue for 48 hours after all dental procedures should be reevaluated on a case-by-case basis. On the other hand, if the dental manipulation involves an infected site, perhaps antibiotic therapy should be continued until signs of the inflammation subside. Dentists and physicians must use their clinical judgement in prescribing antibiotics. However, as Kaye proposed, any deviation in prescribing antibiotics should be in the direction of higher doses or more effective antibiotics. In addition, practitioners must provide adequate patient education and follow-up. Unfortunately, a negligent dentist, a physician giving poor or inadequate advice, or a patient not following instructions may turn a simple dental procedure into a life-threatening situation and potential tragedy.

Anti-Bacterial Agents↗
PubMed2004

Treatment of bioprosthetic heart valve tissue with long chain alcohol solution to lower calcification potential.

The use of glutaraldehyde-treated biological tissue in heart valve substitutes is an important option in the treatment of heart valve disease. These devices have limited durability, in part, because of tissue calcification and subsequent tearing of the valve leaflets. Components thought to induce calcification include lipids, cell remnants, and residual glutaraldehyde. We hypothesized that treatment of glutaraldehyde-treated bioprosthetic heart valve material using a short and long chain alcohol (LCA) combination, composed of 5% 1,2-octanediol in an ethanolic buffered solution, would reduce phospholipid content and subsequently lower the propensity of these tissues to calcify in vivo. Phospholipid content of glutaraldehyde-treated porcine valve leaflets and bovine pericardium was found to be 10.1 +/- 4.3 (n = 7) and 3.9 +/- 0.48 (n = 2) microg/mg dry tissue, respectively, which was reduced to 0.041 +/- 0.06 (n = 7) and 0.21 +/- 0.05 (n = 4) microg/mg dry tissue, respectively, after LCA treatment. Calcification potential of the treated tissues was assessed using a rat subcutaneous implant model. After 60 days of implantation, calcium levels were found to be 171 +/- 32 (n = 11) and 83 +/- 70 (n = 12) mg/g dry weight for glutaraldehyde-treated porcine leaflets and bovine pericardium, respectively, whereas prior LCA treatment resulted in reduced calcium levels of 1.1 +/- 0.6 (n = 12) and 0.82 +/- 0.1 (n = 12) mg/g dry weight, respectively. These data, taken together, support the notion that treatment of glutaraldehyde-treated tissue with a short and long chain alcohol combination will reduce both extractable phospholipids and the propensity for in vivo calcification.

Animals↗
PubMed2005

Lumped parameter model for computing the minimum pressure during mechanical heart valve closure.

The cavitation inception threshold of mechanical heart valves has been shown to be highly variable. This is in part due to the random distribution of the initial and final conditions that characterize leaflet closure. While numerous hypotheses exist explaining the mechanisms of inception, no consistent scaling laws have been developed to describe this phenomenon due to the complex nature of these dynamic conditions. Thus in order to isolate and assess the impact of these varied conditions and mechanisms on inception, a system of ordinary differential equations is developed to describe each system component and solved numerically to predict the minimum pressure generated during valve closure. In addition, an experiment was conducted in a mock circulatory loop using an optically transparent size 29 bileaflet valve over a range of conditions to calibrate and validate this model under physiological conditions. High-speed video and high-response pressure measurements were obtained simultaneously to characterize the relationship between the valve motion, fluid motion, and negative pressure transients during closure. The simulation model was calibrated using data from a single closure cycle and then compared to other experimental flow conditions and to results found in the literature. The simulation showed good agreement with the closing dynamics and with the minimum pressure trends in the current experiment. Additionally, the simulation suggests that the variability observed experimentally (when using dP/dt alone as the primary measure of cavitation inception) is predictable. Overall, results from the current form of this lumped parameter model indicate that it is a good engineering assessment tool.

Animals↗
PubMed1986

[Radiologic imaging of heart valve prostheses in situ].

To determine the radiographic appearance of prosthetic heart valves 15 different models were investigated in situ. Fluoroscopy with detail radiographs and standard chest-radiographs were used for identification of the specific type of the prosthesis, for determination of details of the valve apparatus and for evaluation of the motion of the valve disc/ball. Fluoroscopy and routine radiographs provided sufficient information to identify all prosthetic heart valves with exception of the Xenomedica bioprosthesis. If radiopaque material was used for the valve disc/ball, fluoroscopic assessment of the function of the valve was possible. Thus, in most types of disc or ball valves the opening/closing of the valve can be visualized, whereas in bioprosthesis a radiological determination of the mechanical function is not possible.

Bioprosthesis↗
PubMed2001

Recellularization of heart valve grafts by a process of adaptive remodeling.

The objective of this study was to investigate if function and durability of connective tissue grafts stems from in vivo revascularization and recellularization. Viability is important for durable valve performance, demonstrated by pulmonary autografts. A pattern of in vivo recellularization occurs in xenogeneic or allogeneic heart valves decellularized prior to implantation, dictated by the tissue matrix and functional biomechanics. Porcine or sheep heart valves were decellularized with the SynerGraft antigen reduction process (a common treatment process to remove all histologically demonstrable leaflet cells), and implanted as pulmonary (n = 11) or aortic valve (n = 9) replacements in sheep. Sheep allograft pulmonary valves (n = 4) were implanted as pulmonary valve replacements. Recellularization was evaluated histologically after 3, 4, 5, 6, and 11 months, with cell phenotypes identified using specific antibodies. SynerGraft heart valves were progressively recellularized beginning with an initial cellular infiltrate, and subsequent repopulation with mature interstitial cells. This process occurs in the conduit and then in the leaflet, and is associated with revascularization of the graft. Functional, fully developed fibrocytes, actively synthesizing type I procollagen (antibody probe) were present within 3 months. As the process matured cell density and distribution became similar to native valve leaflets with localization of smooth muscle actin positive cells at the ventricularis/spongiosa interface. After 11 months, leaflet explants had no detectable inflammatory cells, were as much as 80% repopulated, and had a distribution of smooth muscle actin positive cells similar to that of the natural leaflet. SynerGraft- treated heart valve implants are repopulated by a process typical of adaptive remodeling following implantation. This antigen reduction treatment is the first successful tissue engineering effort obtaining an implant with mature recipient cells capable of matrix protein synthesis. Normal early valve function and durability is maintained.

Animals↗
PubMed1989

Wada-Cutter heart valve: overall experience at the Sapporo Medical College.

We performed cardiac valve replacement using the Wada-Cutter valve in 124 patients during the 9 years between 1966 and 1974: aortic valve replacement in 48, mitral valve replacement in 56, tricuspid valve replacement in 9, and multiple valve replacement in 11. Sixteen patients died within 30 days after operation, and 34 died in the late postoperative period, with a cumulative mortality rate of 40.3%. Postoperative complications included valve thrombosis in 9 patients, thromboembolism in 4, and mechanical valve failure in 5. The Wada-Cutter valve, first described at the Annual Meeting of The Society of Thoracic Surgeons on January 27, 1967, in a discussion on the paper by Cooley and colleagues on mitral valve replacement with a discoid valve, attracted attention for its unique design. Four of the Wada-Cutter valves were incorporated in Liotia's total artificial heart, which was implanted clinically for the first time in Cooley's second-stage heart transplantation. It may not only claim to be the origin of today's most popular tilting-disc heart valves but also has some original concepts with regard to bileaflet and tricuspid tilting-disc heart valves. However, at that time, cardiac valve replacement with this prosthesis resulted in a high incidence of thrombosis without systemic anticoagulation and in mechanical valve failure due to hinge wear of the Teflon occluder. For these reasons, its clinical use was discontinued in 1974. If Pyrolite carbon had been adopted in construction of the valve when it first became available, the valve design could have been useful even today.

Aortic Valve↗
PubMed1996

Transcranial high-intensity Doppler signals in patients with mechanical heart valve prostheses: their relationship with abnormal intracavitary echoes.

BACKGROUND AND AIMS OF THE STUDY: In preceding studies, we reported that abnormal Doppler signals of high intensity (HITS) were frequently found in the cerebral arteries of patients with prosthetic mechanical heart valves. These signals should be attributed either to air microbubbles, possibly due to cavitations or to solid emboli elements. On the other hand, the presence of abnormal intracardiac echoes has been reported in patients with mechanical valves. These echoes should be also attributed to air microbubbles or to formed elements. Although in vitro experiments are in favor of the first explanation, the discussion of their origin remains open. METHODS: Among patients subjected to a transesophageal echocardiography (TEE), we selected subjects with mechanical prosthetic heart valves, according to the following criteria: (i) normally functioning valves; (ii) bright echoes suggesting microbubbles, inside the prosthetic valve and/or upstream from it (left ventricular outflow tract or left atrium); (iii) no morphological lesions that could generate solid microemboli at the prosthetic level; (iv) normal carotid arteries, as investigated by color echo-Doppler. RESULTS: Twenty patients were selected: 11 men and nine women of age range 40-64 years. They were implanted with mechanical heart valves (24 Saint-Jude Medical, three Björk-Shiley and one CarboMedics) in the mitral position (10), aortic position (two), or mitral and aortic position (eight) for periods ranging from 10 days to 17 years. There was no major left ventricular dysfunction (mean end-diastolic diameter 51.8 mm; mean ejection fraction 59%). The mean diameter of the left atrium was 46.1 mm. All but three patients were in sinus rhythm; seven had presented with a transient ischemic attack or amaurosis within the six months preceding the investigation. Immediately after TEE, Doppler signals were recorded on the middle cerebral arteries (MCA) during 10 minutes on each side, and the abnormal Doppler signals were counted. Seventeen subjects (85%) exhibited HITS repetition rate from 0.2 to 5.5 per min. CONCLUSION: The percentage of patients with HITS in a non-selected group with mechanical heart valves was about 50%, as observed in previous studies. It appears that in a selected group of patients the percentage with HITS is consistently higher. Therefore, HITS and abnormal intracardiac echoes could have a common origin.

Adult↗
PubMedDate not supplied

The closing behavior of Medtronic Hall mechanical heart valves.

The rapid deceleration of mechanical heart valve leaflets or discs at closure, and their rebound after impact between the leaflets or discs and housing may produce conditions that favor cavitation inception. Precision measurements of the disc closing velocity using a laser sweeping technique (LST) were made on two Medtronic Hall (Med Hall) mitral valve models, the 29 mm Standard and D-16 Med Hall valves. The experiment was carried out in a pulsatile mock flow loop (PFL) by installing the tested valve in the mitral position of the PFL. Tests were conducted under physiologic pressures at heart rates of 70, 90, and 120 beats/min with flow rates of 5, 6, and 7.5 l/min, respectively. For each valve tested, the experimental series was carried out to include both a flexible mounting and a rigid mounting mechanism. The time history of the disc closing velocity during the last 3 degrees before final closure was measured. Results show that the disc approached the valve housing at a near constant velocity of approximately 1.3, 1.5, and 2.0 m/sec for the Med Hall Standard valve, and 1.9, 2.5, and 2.6 m/sec for the Med Hall D-16 valve at 70, 90, and 120 beats/min, respectively. After impact, the valve of disc rebounded with velocities that depended on the mounting modalities and heart rates. In the rigid mounting, the disc rebound velocities of the Med Hall Standard and D-16 valves were about 60%-70% and 70%-80% of their respective approaching velocities. For the flexible mounting, the rebound velocities were 15%-25% and 20%-30% of their respective approaching velocities. The results demonstrate that a slight modification in the seat stop geometry of Med Hall valves can significantly affect disc closure behavior.

Biomechanical Phenomena↗
PubMed2003

Midterm experience with the Sorin Bicarbon heart valve prosthesis for rheumatic disease.

BACKGROUND: In this study, we present a single center experience with Bicarbon bileaflet valve in 307 patients with rheumatic heart disease. METHODS: Between August 1998 and September 2000, 307 patients underwent heart valve replacement using the Bicarbon bileaflet valve (Sorin Biomedica, Saluggia, Italy) with an average age of 47.19+/-13.21 years (range 14 to 80 years), consisting of 147 males and 160 females at Alkan Hospital, Cardiovascular Surgery Department. Aortic valve replacement (AVR) was performed in 77 patients, mitral valve replacement (MVR) in 156 patients and double valve replacement (DVR) in 74 patients. RESULTS: The early mortality rate was 3.3% (10/307) and there was no late mortality. The actuarial survival rate, including hospital mortality, was 96.74+/-1.01% for the whole group, 96.5+/-1.5% for the MVR group, 97.4+/-1.8% for the AVR group and 97.3+/-1.9% for the DVR group at 35 months. One patient had obstructive valve thrombosis with MVR. The 35 months actuarial freedom from valve thrombosis was 99.58+/-0.4% for the whole group. Four patients were reoperated and the 35 months actuarial freedom from reoperation was 98.53+/-0.7% for the whole group, 98.65+/-0.9% for the MVR group, 96.73+/-02% for the DVR group and 100% for the AVR group. No instances of perivalvular leak, hemolysis, endocarditis or embolism were observed during the entire follow-up period. Mean follow-up duration was 16.5+/-7.9 months (ranged 4 to 35 months). CONCLUSION: We have presented our mid-term results with the Sorin Bicarbon bileaflet valve in patients with rheumatic heart disease, which provided good clinical performance combined with meticulous patient care and advanced surgical techniques.

Adolescent↗
PubMed2004

Beating-heart valve surgery in patients with renal failure requiring hemodialysis.

BACKGROUND AND AIM OF THE STUDY: The safety and efficacy of beating-heart valve surgery as a myocardial protection strategy was evaluated in patients with renal failure requiring hemodialysis. METHODS: This was a retrospective review of nine patients (four males, five females; mean age 46.7 years; mean duration of hemodialysis 47 +/- 49 months) who underwent beating-heart valve surgery at the present authors' institution between April 2000 and September 2002. RESULTS: The mean cardiopulmonary bypass time was 77.2 +/- 8 min. Perioperatively, two patients died (one from sepsis; one from complication of anticoagulation). There were no deaths in the follow up since discharge, with average follow up 18.3 months (range: 9-27 months). Other complications included reintubation for <24 h (one case), AV graft thrombosis (one patient) and stroke (one patient, as mentioned above). There were no new cardiac (including arrhythmia and low cardiac output syndrome) or metabolic complications (including hyperkalemia and fluid overload). CONCLUSION: This is the first report of beating-heart valve surgery using simultaneous antegrade and retrograde perfusion with normothermic blood. Despite being small in size, the study demonstrated the safety of this approach in a high-risk population with renal failure requiring hemodialysis. The results suggested a low incidence of complications, and short ICU and hospital stays.

Adult↗
PubMed2001

Risks of fracture of Björk-Shiley 60 degree convexo-concave prosthetic heart valves: long-term cohort follow up in the UK, Netherlands and USA.

BACKGROUND AND AIM OF THE STUDY: Approximately 82,000 Björk-Shiley convexo-concave (BSCC) 60 degree prosthetic heart valves were implanted in patients worldwide between 1979 and 1986. Outlet strut fractures (OSF) of some of the valves were first reported shortly after their introduction. Here, the determinants of OSF are examined, and the between-country variation and long-term risk are assessed. METHODS: Cohorts of patients in the UK, Netherlands and USA with 15,770 BSCC 60 degree heart valves were followed up to 18 years for the occurrence of OSF. RESULTS: Crude rates of OSF were highest in the UK (0.18% per year), intermediate in the Netherlands (0.13%), and lowest in the USA (0.06%), although risk factor adjustment reduced the inter-country differences. Furthermore, in the UK and Netherlands, OSF rates (particularly for mitral valves) declined with time since implantation, and between-country differences were considerably diminished 10 or more years post implantation. The risk of OSF decreased steadily with advancing patient age. Fracture rates were lower among women than men, and also varied significantly with valve size and position and OSF status of other valves in the same shoporder. CONCLUSION: This long-term follow up of BSCC 60 degree heart valve patients indicates that risk factors for valve fracture are generally similar in the UK, Netherlands and USA. It also identifies a strong association between fracture risk and age, newly reveals gender-related differences, and shows that the risk of valve fracture persisted, albeit at a reduced rate, into the 1990s.

Adult↗
PubMed1993

Zinc in rheumatic heart valves.

This study included 48 patients with chronic rheumatic heart disease, 60 control subjects for plasma zinc comparison and 20 control specimens of heart valves from postmortem cases of accident deaths. Plasma and cardiac tissue levels of zinc in patients with rheumatic heart disease were significantly lowered compared to controls. Since zinc is important in the synthesis of nucleic acids and proteins it may influence tissue growth, reparative process and structure and function of biomembrane. Low zinc levels may also influence cell mediated immunity and may increase susceptibility of patients to infection and increased rheumatic activity which needs further study.

Adolescent↗
PubMed1996

Impact of glutaraldehyde on calcification of pericardial bioprosthetic heart valve material.

BACKGROUND: This study was conducted to investigate the impact of the preservation method of bioprosthetic heart valve materials on calcification rates and biocompatibility of the biologic tissue. METHODS: In subcutaneous rat implants, conventionally preserved bioprosthetic heart valve material was compared with bovine pericardium that was treated with L-glutamic acid to reduce residual glutaraldehyde released from the fixed tissue. Both these methods were compared with bovine pericardium that was stabilized by a dye-mediated photooxidation reaction without glutaraldehyde. Biocompatibility of these biomaterials was tested in vitro using human endothelial cell cultures. RESULTS: Conventionally preserved bovine pericardium with a high amount of glutaraldehyde incorporated into the tissue resulted in severe calcification 63 days after subcutaneous implantation in rats (165.4 +/- 20 mg Ca2+/g dry weight). Postfixation treatment with L-glutamic acid, which reduces free, unbound aldehyde groups, showed a significant decrease in calcification (89.6 +/- 14 mg Ca2+/g dry weight). Glutaraldehyde-free preservation by dye-mediated photooxidation showed no calcification after 63 days of subcutaneous implantation (1.0 +/- 0.4 mg Ca2+/g dry weight). Regular endothelial cell proliferation was observed on photooxidized and L-glutamic acid-treated tissue, whereas conventionally treated tissue caused endothelial cell death. CONCLUSIONS: This study underlines the detrimental role of glutaraldehyde in the calcification process of bioprosthetic heart valve materials and emphasizes alternative preservation methods that reduce or avoid the use of glutaraldehyde.

Animals↗