SEARCH · PubMed Health

Results for “HEART VALVES”

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 631 records · Page 35Linked to original sources

PubMed1978

Durability of prosthetic heart valves.

Accelerated fatigue testing of clinical heart valves has been performed at cyclic rates of 33 to 35 cycles per second at 37 degrees C using water for non-biological valves and glutaraldehyde solutions for tissue valves. Flows were in the physiological range, and the pressure difference across each valve during closure was 100 +/- 25 mm Hg. The results showed that major fatigue occurred for the Starr-Edwards 2320 at 150 million cycles, the Hufnagel trileaflet at 124 million cycles, the Björk-Shiley Delrin disc at 140, the Björk-Shiley Pyrolite disc at 973, the Beall 103 at 60, the Hancock porcine at 62, the Carpentier-Edwards porcine at 34, and the Ionescu-Shiley porcine pericardial prosthesis at 65 million cycles. The Lillehei-Kaster was removed after 762 million cycles without discernible wear. Three facts emerged from the testing data: (1) the component worn in vitro wears in vivo; (2) the sites of in vitro fatigue on the component are identical to clinical specimens; and (3) those valves that have high durability in vitro have given similar performance in patients. The in vitro and clinical data for tissue valves do not correlate. The possible reasons for the discrepancy are discussed, and a note of caution is made regarding realistic expectations of clinical durability of tissue valves.

Bioprosthesis↗

PubMed1983

Localized dystrophic amyloidosis of heart valves.

A survey of 152 surgically resected heart valves (90 aortic, 60 mitral, two pulmonic) from a consecutive series of 142 adult patients revealed congophilic, green birefringent, amyloid deposits in 81 valves (59 aortic, 22 mitral) from 77 patients from 41 to 79 years of age. Amyloid was found in 50 (82 per cent) of 61 valves showing degenerative calcific sclerosis and in 31 (53 per cent) of 58 valves showing post-rheumatic sclerosis but in none of 33 valves showing more acute disease processes (myxoid transformation, "stretch lesions," healed bacterial endocarditis). All the amyloidotic valves showed some calcification, and amyloid deposits frequently occurred around the calcified foci. Histochemically, the valvular amyloid was distinguishable from other major forms of amyloid by its largely negative alcian blue and periodic acid-Schiff staining and by its pepsin-resistant iodine staining. The localized, dystrophic nature and unusual histochemical properties of this valvular amyloidosis clearly distinguish it from other forms of cardiac amyloidosis.

Adolescent↗

PubMedDate not supplied

In vivo evaluation of a trileaflet mechanical heart valve.

Design goals for a mechanical heart valve include duplicating the hemodynamic performance of the natural valve, eliminating the need for anticoagulants, and maintaining safety. The Lapeyre-Dassault (Dassault-Aviation, Paris, France) prosthetic valve, undergoing development, addresses these goals. The unique trileaflet design consists of a solid titanium ring and three leaflets. Prototypes of the valve fabricated with Delrin leaflets were implanted in the mitral position in six calves (70-90 kg). Four calves (Studies 1, 2, 3, 5) had long-term survival of 165, 158, 219, and 281 days, respectively. Two calves were killed, one on Day 37 and one on Day 39, after complications unrelated to the valve developed. In all calves heparin was given intravenously to maintain partial thromboplastin time at 1.5 to 2.0 x baseline for approximately 1 week. In Studies 1 and 2 full anticoagulation and antiplatelet therapy was given (orally administered sodium warfarin to maintain prothrombin time at 1.5 to 2.0 x baseline, along with aspirin (1 g/day) and dipyridamole 400 mg/day). In Study 3, all anticoagulation and antiplatelet therapy was discontinued at 1 month after implant. In Study 5, no anticoagulation therapy was given after the initial week of intravenous heparin; however, antiplatelet therapy was started on the fifth postoperative month and maintained until the study's end at 9 months. At 1, 2, 3, and 5 months, the mean plasma free hemoglobin level in the four long-term animals was 5.0 +/- 2.16, 6.0 +/- 3.83, 8.5 +/- 4.93, and 11.3 +/- 6.74 mg/dl, respectively. Hemolysis was not a problem. Valve performance during normal activity was excellent in all the calves, as evidenced by echocardiography and the overall appearance of good health. In the four completed long-term studies, left heart catheterization showed a mean valve pressure gradient of 11.57 +/- 1.26 mmHg and no apparent valvular regurgitation. Histopathologic examination of major organs showed no evidence of thromboembolic events. This study shows that the innovative design of this trileaflet valve performed well in initial in vivo testing, justifying further development.

Animals↗

PubMed1997

[Pregnancy in women with a mechanical heart valve. Review of the literature].

AIM: To define therapeutic ways to manage obstetrics at an optimal level for a patient carrying a mechanical prosthetic heart valve. METHOD: From a review of literature and documented cases, we propose an obstetrical and cardiological management scheme for pregnant patients carrying a mechanical prosthetic heart valve. We deal successively with the preventive (anticoagulation) and curative treatment (surgery and thrombolytic therapy) of valvular thrombosis, in fact, a severe -but unfortunately frequent- complication of these pregnancies. RESULTS: Pregnancy concerning patients with mechanical prosthetic heart valves is a high-risk pregnancy. In fact, the risk of thrombo-embolic accidents even with a closely followed anticoagulant treatment seems to come from the existence of the prothese, the state of physiological hypercoagulation and peri-partum hemorrhages. Naturally, multidisciplinary follow-up is indispensable. The prescription of anticoagulant treatments must respect the main principals and the normal counter-indications in order to minimise maternal and fetal complications. CONCLUSION: Pregnancy amongst patients carrying mechanical prosthetic heart valves should be considered rare and highly exceptional cases, from a cardio-vascular surgeon's point of view. For obstetricians, it is sometimes difficult to forbid pregnancy to a nullipara. The discussion whether to authorize a pregnancy will be treated case-by-case, holding into account the socio-cultural environment of the patient, as the principles of an anticoagulant treatment and the underlying risks must be well understood.

Anticoagulants↗

PubMed1996

Prophylactic replacement of Björk-Shiley convexo-concave heart valves: an easy-to-use tool to aid decision-making in individual patients.

OBJECTIVE: To develop an easy-to-use tool for decision-making on prophylactic replacement of Björk-Shiley convexo-concave heart valves. DESIGN: Decision analysis comparing elective replacement with observation. SETTING: Referral centres for patients with artificial heart valves. PATIENTS: Quantitative estimates were obtained from a follow up study conducted in The Netherlands, including 2303 patients with a mean follow up of 6.6 years and from recently published studies. INTERVENTION: Elective valve replacement with a new artificial heart valve. MAIN OUTCOME MEASURE: Loss of life-expectancy. RESULTS: A simple graph was constructed to present the loss of life-expectancy caused by strut fracture for combinations of basal life-expectancy (life-expectancy without strut fracture) and lethal fracture risk (strut fracture risk multiplied by lethality of fracture). This loss can be compared directly with the loss of life-expectancy caused by surgical mortality. This quantitative approach takes into account individual patient characteristics, such as age, gender, cardiac comorbidity, and position of the valve, but the final estimation of surgical mortality also requires clinical judgement. The calculations can be made easily by hand or with a simple computer application. CONCLUSIONS: This decision support tool enables the direct estimation of the gain or loss of life-expectancy that is likely with replacement of a Björk-Shiley convexo-concave heart valve. It can be used to evaluate individual patients as well as groups of patients, and allows for easy incorporation of revisions of fracture risk estimates.

Adult↗

PubMed1978

[Temporal characteristics of the movement of the cut-off elements of artificial heart valves in a pulsing flow].

A comparative investigation of time characteristics of the movement of artificial heart valves with spherical, hemispherical and lentil-shaped obturative elements under non-stationary conditions was carried out. It has been found that it is practically impossible to avoid the delay in the valve closing and opening, as well as the regurgitation phenomena, on the valve prothesis, due to the inertia of obturative elements and attached masses. A searching for new models of the heart valves should go on.

Aortic Valve↗

PubMed2001

Calcification resistance, biostability, and low immunogenic potential of porcine heart valves modified by dye-mediated photooxidation.

The calcification potential, biostability, and immunogenic response of materials intended for long-term in vivo use, such as in heart-valve bioprostheses, are essential components of device performance. Here we explore these properties in photooxidized porcine heart valves. To study immunological sensitization, we injected tissue extracts intradermally into guinea pigs. Test and control animals received a challenge patch of the appropriate extract and were scored for dermal reactions. Neither cottonseed oil nor sodium chloride extracts of photooxidized heart-valve tissues caused any dermal inflammatory response. After implantation in the rat subcutaneous model for 90 days, the calcium content of 48-h-treated photooxidized cusp tissue [0.04 +/- 0.00 mg/g wet weight (gww)] was comparable to that of unimplanted control tissues (usually <1 mg/gww) and much lower than that of glutaraldehyde-treated controls (71 +/- 15 mg/gww). The porcine aortic wall calcium content (49 +/- 31 mg/gww) was comparable to that of glutaraldehyde-treated controls (59 +/- 8 mg/gww). Histologically, a time-dependent decrease in inflammation and vascularization with increasing photooxidation time was noted in the rat model along with an increase in the stability and organization of collagen bundles. In summary, porcine valve tissues treated by dye-mediated photooxidation were resistant to calcification, were biostable, and demonstrated a low immunogenic response, indicating potential for use in heart-valve bioprostheses.

Animals↗

PubMed1999

High-frequency pressure fluctuations measured in heart valve patients.

BACKGROUND AND AIM OF THE STUDY: Due to the risk of thromboembolic complications, mechanical heart valve patients require life-long anticoagulant therapy, in contrast to bioprosthetic valves. The reason for this is still not fully understood. In vitro studies have demonstrated the presence of cavitation bubbles in the vicinity of mechanical heart valves, but not of bioprosthetic valves. When cavitation bubbles collapse, they release a significant amount of energy, which may damage the formed elements of the blood. A correlation between the presence of cavitation bubbles and high-frequency pressure oscillations has been established in vitro. Thus, the aim of this study was to measure and quantify high-frequency pressure oscillations in patients with normal, bioprosthetic or mechanical aortic valves. METHODS: Measurements were performed in six patients with normal aortic valves after coronary bypass surgery, in five patients fitted with a Carpentier-Edwards pericardial bioprosthesis, and in nine patients fitted with a St. Jude Medical or CarboMedics aortic valve. High-frequency pressure fluctuations were measured intraoperatively using a hydrophone placed near the aortic annulus. The root mean square (RMS) value of the high-frequency pressure signals were calculated in the frequency range 35-150 kHz. RESULTS: High-frequency pressure fluctuations, with intensities above the noise floor, were registered only in the vicinity of mechanical heart valve prostheses, and not in the vicinity of normal or bioprosthetic valves. The mean value of RMS pressure fluctuations was 0.5 Pa for normal aortic valves, 0.8 Pa for bioprosthetic valves, and 67 Pa for mechanical valves. CONCLUSIONS: This study is the first to show the presence of high-frequency pressure fluctuations in patients with mechanical valves.

Aged↗

PubMed2002

Detection of calcium deposits on heart valve leaflets by vibro-acoustography: an in vitro study.

The presence of calcium deposits on heart valve leaflets constitutes a clinically significant diagnostic indication. A novel method for imaging and detecting calcium deposits on tissue heart valves is presented. The method, called vibro-acoustography, uses the radiation force of ultrasound to vibrate the tissue at low (kHz) frequency and records the resulting acoustic response to produce images that are related to the hardness of the tissue. The method is tested on excised human heart valve tissues. Resulting images clearly show calcium deposits with high contrast and are in agreement with the corresponding radiographs of the specimens.

Algorithms↗

PubMed1996

Guidelines for reporting morbidity and mortality after cardiac valvular operations. The American Association for Thoracic Surgery, Ad Hoc Liaison Committee for Standardizing Definitions of Prosthetic Heart Valve Morbidity.

At the request of the Councils of The Society of Thoracic Surgeons (STS) and The American Association for Thoracic Surgery (AATS) the Ad Hoc Liaison Committee for Standardizing Definitions of Prosthetic Heart Valve Morbidity "revisited" the "Guidelines" published in September 1988 [1-3]. The purpose of the review was to update and clarify definitions within the guidelines and to consider recommendations made by others [4, 5]. The variety of cardiac valvular procedures has expanded since 1988; therefore, in this document the term "operated valve" indicates prosthetic and bioprosthetic heart valves of all types: operated or repaired native valves and allograft and autograft valves. The term "operated valve" includes any cardiac valve altered by a surgeon during an operation. Much morbidity and mortality is a direct consequence of the interaction between the patient and operated valve(s), although patient variables (e.g., age, degree of coronary arterial disease, follow-up care) may be more responsible for outcomes than an operated valve. However, no set of guidelines can identify all possible patient factors that may affect morbidity and mortality. General agreement regarding the following definitions of terms and suggestions for reporting data do not preclude more detailed analyses or constructive recommendations and investigators are encouraged to identify relevant patient factors in addition to factors related to operated valves.

Documentation↗

PubMed2006

Fundamental mechanics of aortic heart valve closure.

Stresses in a prosthetic heart valve at closure are determined by its geometrical and structural characteristics, by the mechanical support environment, and by the momentum of the valve leaflets or occluder and of the blood at the instant of closure. The mass of blood to be arrested is significantly greater than that of the leaflets or occluder, and is therefore likely to dominate the closure impulse. The kinetic energy of the blood must be transduced into potential energy in the structural components (valve leaflets, aortic root and aorta). This paper presents a methodology for computation and parameterisation of the blood momentum associated with a valve in the aortic position. It is suggested that the influence of physiological parameters, such as systolic waveform and systemic impedance, on the closure characteristics can be investigated based on the fluid dynamic implications. Detailed results are presented for a single leaflet mechanical valve (Bjork-Shiley 60 degrees Convexo-Concave). It is demonstrated that a simple analytical method can yield results that might be adequate for the purposes of valve design.

Aorta↗

PubMed2003

Two-dimensional fluid-structure interaction simulation of bileaflet mechanical heart valve flow dynamics.

BACKGROUND AND AIM OF THE STUDY: Mechanical heart valve implantation requires long-term anticoagulation because of thromboembolic complications. Recent studies have indicated that the relatively high wall shear stresses and negative pressure transients developed during the valve closing phase may be dominant factors inducing thrombus initiation. The study aim was a two-dimensional (2D) functional simulation of flow past bileaflet heart valve prosthesis during the closing phase, incorporating the fluid-structure interaction analysis to induce motion of the leaflets. METHODS: The fluid-structure interaction model used was based on unsteady 2D Navier-Stokes equations with the arbitrary Lagrangian-Eulerian method for moving boundaries, coupled with the dynamic equation for leaflet motion. Parametric analysis of the effect of valve size, leaflet density, and the coefficient of resilience at the instant of impact of the leaflet with the housing were also performed. RESULTS: Comparing the predicted motion of the leaflet with previous experimental results validated the simulation. The results showed the presence of negative pressure transients near the inflow side of the leaflet at the instant of valve closure, and the negative pressure transients were augmented during the leaflet rebound process. Relatively high velocities and wall shear stresses, detrimental to the formed elements in blood were present in the clearance region between the leaflet and valve housing at the instant of valve closure. CONCLUSION: The simulation can be potentially applied to analyze the effects of valve geometry and dimensions, and the effect of leaflet material on the flow dynamics past the valve prosthesis during the opening and closing phases for design improvements in minimizing problems associated with thromboembolic complications.

Biomechanical Phenomena↗

PubMed1977

The principles and in vivo performance of the Edinburgh pivoted aerofoil-disc prosthetic heart valve.

Prototypes of the Edinburgh prosthetic heart valve, known from previous experiments in vitro to promote exceptionally smooth and undisturbed forward flow, have been shown here in canine experiments to possess hemodynamic characteristics not inferior to those of the Bjork-Shiley valve (a present standard of excellence). In addition, we report a low incidence of valve thrombus deposition among calves in which this prototype valve, fabricated from the conventional materials, Delrin and stainless steel, has been implanted in the tricuspid site for up to 100 days without use of anticoagulants. This suggests that the design of the valve is such as to render it of low thrombogenicity. The new valve is designed for fabrication throughout in vitreous or pyro-coated carbon, materials of very high inherent athrombogenicity. It appears from the results discussed here that the developed form of the prosthesis, composed wholly of these athrombogenic materials, is likely to have both acceptable hemodynamic characteristics and an exceptionally low tendency to form thrombus. The introduction of such valves promises to be very advantageous and the results given here appear to warrant their development as the next stage of this program.

Animals↗

PubMed2003

Introduction of a flexible polymeric heart valve prosthesis with special design for mitral position.

BACKGROUND: Current heart valve prostheses are constructed mimicking the native aortic valve. Special hemodynamic characteristics of the mitral valve such as a nonaxial central inflow with creation of a left ventricular vortex have so far not been taken into account. A new polycarbonaturethane (PCU) bileaflet heart valve prosthesis with special design for the mitral position is introduced, and results of animal testing are presented. METHODS AND RESULTS: After in vitro testing, 7 PCU-prostheses and 7 commercial bioprostheses (Perimount, n=4; Mosaic, n=3) were implanted in mitral position into growing Jersey calves (age 3-5 months, weight 60-97 kg) for 20 weeks. 2-Dimensional echocardiography was performed after implantation and before sacrification. Autopsy included histologic, radiographic, and electron microscopic examination of the valves. In vitro durability was proven for >15 years. After implantation 2-dimensional-echocardiography showed no relevant gradient or regurgitation of any prosthesis. Clinical course of the animals with PCU valves was excellent. In contrast, 5 of 7 calves with bioprostheses were sacrificed after 1-9 weeks because of congestive heart failure. 2-Dimensional echocardiography of the PCU valves after 20 weeks showed mild leaflet thickening with trivial regurgitation; mean gradient was 8.1+/-5.0 mm Hg (weight: 160-170 kg). The explanted PCU prostheses revealed mild calcification and no structural degeneration. All of the Perimount bioprostheses were severely calcified and degenerated after 11+/-7 weeks. One Mosaic bioprosthesis was thrombosed after 1 week, and 2 showed severe and mild-to-moderate degeneration after 4 and 22 weeks, respectively. CONCLUSIONS: Polycarbonaturethane valve prostheses with special design for mitral position show excellent hemodynamic performance and durability in vivo. Calcification and structural changes are mild compared with bioprostheses. Controlled clinical studies are planned.

Animals↗

PubMed1985

Inhibition of calcification of bioprosthetic heart valves by local controlled-release diphosphonate.

Bioprostheses fabricated from porcine aortic valves are widely used to replace diseased heart valves. Calcification is the principal cause of the clinical failure of these devices. In the present study, inhibition of the calcification of bioprosthetic heart valve cusps implanted subcutaneously in rats was achieved through the adjacent implantation of controlled-release matrices containing the anticalcification agent ethanehydroxydiphosphonate dispersed in a copolymer of ethylene-vinyl acetate. Prevention of calcification was virtually complete, without the adverse effects of retarded bone and somatic growth that accompany systemic administration of ethanehydroxydiphosphonate.

Animals↗

PubMedDate not supplied

A new approach to detection of the cavitation on mechanical heart valves.

The cavitation on the mechanical heart valves (MHVs) is thought to be a cause of the mechanical failure of the occluder; also, the free radicals that would be generated when the cavitation bubbles implode might affect the patients chemically. These cavitation effects are attributed to the bubble collapse. Therefore, it is important to detect the bubble implosion behavior to analyze the cavitation on MHVs. The cavitation bubbles induce the generation of free radicals at their implosion, and the excited hydroxyl radicals emit the faint light. Based on this fact, we have tried to observe the faint light emission from a MHV to specifically capture the implosion of the cavitation bubbles. A highly sensitive CCD (charge coupled device) camera (C2400-35 VIM camera, Hamamatsu Photonics, Hamamatsu, Japan) was adopted in this study. This camera can observe low light down to the single photon counting range, and it gives two-dimensional mapping of the light. A 20 mm Björk-Shiley valve was submerged in the water tank of 10 L deionized water with luminol as a light enhancer, and then the pressure difference of 150 mm Hg was exerted on the valve at a rate of 60 bpm with a pulse duplicator. The camera and the water tank were settled in the lightproof configuration. After 2 hours of exposure, faint light images have been obtained successfully. The light emits mostly from the edge of the occluder on the inflow side in the major orifice of the valve. Therefore the results suggest that the bubbles would implode around this region and that free radicals caused by cavitation might be produced on MHV, which has coincided with our preliminary result by an electron spin resonance spectrometry.

Biophysical Phenomena↗

PubMed1997

A comparison of a moderate with moderate-high intensity oral anticoagulant treatment in patients with mechanical heart valve prostheses.

BACKGROUND: The long-term administration of oral anticoagulants to patients with mechanical heart valve prostheses is generally accepted. However, the appropriate intensity of oral anticoagulant treatment in these patients is still controversial. METHODS AND RESULTS: From March 1991 to March 1994, patients referred to the Padova Thrombosis Center who had undergone mechanical heart valve substitution at least 6 months earlier were randomly assigned to receive oral anticoagulants at moderate intensity (target INR = 3) or moderate-high intensity (target INR = 4). Principal end points were major bleeding, thromboembolism and vascular death. Minor bleeding was a secondary end-point. A total of 104 patients were assigned to the target 3 group and 101 to the target 4 group; they were followed for from 1.5 years to up 4.5 years (mean, 3 years). Principal end-points occurred in 13 patients in the target 3 group (4 per 100 patient-years) and in 20 patients in the target 4 group (6.9 per 100 patient-years). Major hemorrhagic events occurred in 15 patients, 4 in the target 3 group (1.2 per 100 patient-years) and 11 in the target 4 group (3.8 per 100 patient-years) (p = 0.019). The 12 recorded episodes of thromboembolism, 4 of which consisted of a visual deficit, were all transient ischemic attacks, 6 in the target 3 group (1.8 per 100 patient-years) and 6 in the target 4 group (2.1 per 100 patient-years). There were 3 vascular deaths in each group (0.9 and 1 per 100 patient-years for target 3 and target 4 groups, respectively). Minor bleeding episodes occurred 85 times (26 per 100 patient-years) in the target 3 group and 123 times (43 per 100 patient-years) in the target 4 group (p = 0.001). CONCLUSIONS: Mechanical heart valve patients on anticoagulant treatment who had been operated on at least 6 months earlier experienced fewer bleeding complications when maintained on a moderate intensity regimen (target INR = 3) than those on a moderate-high intensity regimen (target INR = 4). The number of thromboembolic events and vascular deaths did not differ between the two groups.

Administration, Oral↗

PubMed2006

Tissue engineering of heart valves in vivo using bone marrow-derived cells.

In this study, we tissue-engineered heart valves in vivo using autologous bone marrow-derived cells (BMCs). Canine BMCs were differentiated into endothelial cell (EC)-like cells and myofibroblast (MF)-like cells. Decellularized porcine pulmonary valves were seeded with BMCs and implanted to abdominal aorta and pulmonary valve of bone marrow donor dogs. Histological examination of the explants identified the regeneration of valvular structures expressing CD31 and smooth muscle alpha-actin, indicating the presence of EC-like and MF-like cells in the grafts at 3 and 1 week, respectively, after implantation. Fluorescent microscopic examinations identified the presence of fluorescently labeled cells in the explants, indicating that the implanted BMCs survived and participated in the heart valve reconstitution. This study reports, for the first time, on tissue engineering of heart valve in vivo using BMCs.

Animals↗