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PubMed1983

[Concentrations of cefotiam in serum, heart valves, muscle and adipose tissue during heart surgery].

In 20 patients undergoing heart surgery, concentrations of cefotiam (Halospor) in plasma, heart valves, muscles and subcutaneous tissue were determined after intravenous injection of 2 g. Within 5 h cefotiam serum concentration declined from 18 micrograms/ml to 7 micrograms/ml, the concentrations in heart valves declined from 22 micrograms/g to 4 micrograms/g. In heart valves the concentrations during heart surgery were high enough to inhibit most Staphylococcus aureus, E. coli and Klebsiella strains.

Adipose Tissue↗
PubMed1985

[Heart valve surgery without heart catheter study].

The development of new non-invasive diagnostic techniques in cardiology and their validisation has questioned the up-to-now performed preoperative heart-catheterization for evaluation of valvular heart disease. Although all these methods--2-dimensional echocardiography, Doppler-sonography and nuclear techniques--offer a reliable judgement in regard to classification and operative indications, coronary heart disease can only be ruled out by coronarography--except in younger patients without risk-factors and angina. Also in acute valvular disease the invasive diagnostic measures give the heart surgeon more security as regards additional morphologic changes such as intimatears, fistulas or abscesses near the valve. The sensitivity of invasive methods is higher than that of 2-dimensional echocardiography. The expanding application of non-invasive diagnostic tools and with increasing experience it can be assumed that heart-catheterizations prior to surgical valvular repair can be done with more accuracy and not only as a routine.

Aortic Valve Insufficiency↗
PubMed1991

Principle of operation, design criteria and fluid dynamics of a new bileaflet heart valve prosthesis.

Bileaflet heart valves show the best fluid dynamic behaviour among mechanical valves and, as a consequence, give the best clinical results. A new bileaflet heart valve has been designed whose main characteristics are the kind of leaflet movement, low profile, fluid dynamics and material. Two flat leaflets move freely inside a very low profile housing ring. The movement is described by the rolling without sliding of the leaflet surface around a cylindrical surface on the inner wall of the housing. The opening angle is 85 degrees. Both the leaflets and the housing are machined from a solid piece of titanium and then covered with carbon by ion beam techniques. The design phase and the first fluid dynamic evaluation were done by numerical methods.

Carbon↗
PubMed2000

Role of cine-fluoroscopy, transthoracic, and transesophageal echocardiography in patients with suspected prosthetic heart valve thrombosis.

Prosthetic heart valve thrombosis (PVT) is a rare but potentially life-threatening complication of heart valve replacement. An effective, quick, and easy diagnostic method is highly desirable. We evaluated the diagnostic efficacy of cine-fluoroscopy (CF), transthoracic (TTE), and transesophageal (TEE) echocardiography in 82 consecutive patients with mechanical valves and suspected PVT. Criteria for PVT were: leaflet(s) motion restriction at CF, increased Doppler gradients at TTE, and evidence of thrombi at TEE. Patients were divided in 4 groups (A, B, C, and D) according to results of CF and TTE. Group A was composed of 24 patients with positive CF and TTE. Thrombi were detected by TEE in all cases, suggesting that when both are positive, CF and TTE correctly identified PVT in all patients so that TEE may be deferred. Group B was composed of 12 patients with positive CF and negative TTE; TEE showed PVT in 4 patients (33%). These patients had very slight leaflet motion restriction as in the case of initial PVT. This suggests that CF compared with Doppler may identify patients with "hemodynamically significant" PVT. The remaining 8 patients in this group had monocuspid prostheses with negative TEE, suggesting that abnormal leaflet motion at CF may be due to functional changes. Therefore, TEE should always be performed in case of monocuspid prostheses with isolated CF abnormalities. Group C was composed of 18 asymptomatic patients with small-sized aortic prostheses and very high Doppler gradients on routine TTE. CF showed normal leaflet motion and TEE ruled out PVT in all cases outlining the diagnostic role of CF in this particular subset. Finally, group D was composed of 28 patients with negative CF and TTE. TEE did not show thrombi in 24 of 28 patients (86%), confirming that, when both yield negative results, CF and TTE are reliable methods to rule out valve thrombosis in most cases. However, in 4 of 28 patients (14%) TEE showed "nonobstructive" prosthetic thrombosis: these patients had mitral prostheses, chronic atrial fibrillation, and 3 of 4 had systemic embolisms. Thus, TEE should be performed in selected patients despite negative CF and TTE results. Sensitivity, specificity, and positive and negative predictive values were 87%, 78%, 80%, and 91% for CF and 75%, 64%, 57%, and 78% for TTE, respectively. CF and TTE correctly identified PVT in 70 of 82 patients (85%). TEE was actually required in 15% of the cases. Thus, CF and TTE are quick, effective, and complementary diagnostic tools to diagnose PVT in most patients. TEE still remains the gold standard technique in selected cases.

Aged↗
PubMed1980

The design, fabrication and evaluation of a trileaflet prosthetic heart valve.

Although prosthetic heart valves have been in existence for many years, the need for new improved designs and in-vitro evaluation techniques are apparent. This paper presents details on the design considerations, fabrication techniques and heart valve evaluation equipment. A valve performance index is discussed in light of various valve and mock circulatory test section designs. The need for national and indeed international valve evaluation techniques is made apparent.

Aortic Valve↗
PubMedDate not supplied

Blood compatibility of a newly developed trileaflet mechanical heart valve.

An ideal heart valve prosthesis, which has both the flow dynamic properties and blood compatibility of a tissue valve prosthesis and the durability of a mechanical prosthesis, does not exist. The Triflo trileaflet mechanical heart valve (MHV; Triflo Medical Inc., Irvine, CA) is a newly developed MHV prosthesis with the following design goals: central flow, minimal flow disturbance and stasis around the hinge region, and durability. The current study was conducted to evaluate the blood compatibility of a 29 mm Triflo MHV in the mitral position of eight calves for 5 months without any postoperative anticoagulation. Whole blood platelet aggregometry and the Xylum Clot Signature Analyzer (Xylum Corporation, Scarsdale, NY) were used to evaluate the postoperative changes in platelet and coagulation functions. Full autopsies, histological examinations of major internal organs, and scanning electron microscopy analyses of the explants were performed. Early termination occurred in two cases; one was because of valve thrombosis on the 25th day, and the other was killed because of a nonvalvular complication on the 105th day. The valve thrombosis was attributed to prolonged ventricular fibrillation at the time of valve replacement surgery. Whole blood platelet aggregometry and clot signature analyzer parameters did not show any sign of activation of platelets or the coagulation system. No hemolysis was observed. There was no macroscopic valve thrombosis or embolism observed in the remaining seven cases. Scanning electron microscopy analyses showed clean leaflet and valve ring surfaces, with only occasional minute platelet aggregations. Excellent blood compatibility of the Triflo MHV was demonstrated in this study.

Animals↗
PubMed2002

Long-term results of valve replacement with the CarboMedics prosthetic heart valve.

This study examined the long-term results of the CarboMedics prosthetic heart valve. Between July 1990 and May 2000, 256 CarboMedics valve prostheses (120 single aortic, 62 single mitral, and 34 double aortic/mitral) were implanted into 216 patients (mean age 57.8 years). The mean follow-up was 57.7 +/- 36 months (maximum 133 months) with a total of 1,038.4 patient years. Patient survival, including operative deaths, was 85.1% at 10 years. Linearized rates for various complications were thromboembolism 0.39% per patient year, bleeding events 0.39% per patient year; prosthetic valve endocarditis 0.29% per patient year, nonstructural dysfunction 0.87% per patient year, and reoperation 0.39% per patient year. There were no valve thrombosis or structural valve failures in this series. The probabilities of freedom from thromboembolism and reoperation at 10 years were 96.3% and 93.1%, respectively. In conclusion, the CarboMedics valve can be used satisfactorily with a low incidence of thromboembolism and valve thrombosis.

Aortic Valve↗
PubMed1997

Low-intensity oral anticoagulation plus low-dose aspirin versus high-intensity oral anticoagulation alone: a randomized trial in patients with mechanical prosthetic heart valves.

BACKGROUND: Mechanical heart valve replacement requires lifelong anticoagulant treatment. Aspirin has proved useful in further reducing thromboembolic events when added to oral anticoagulants. However, increased (gastrointestinal) bleeding was observed at the doses previously tested for this combination in heart valve prostheses. METHODS: We performed a prospective randomized trial to compare the combination of low-intensity oral anticoagulants (international normalized ratio 2.5 to 3.5) plus aspirin (100 mg/day) (arm A) versus high-intensity oral anticoagulants alone (arm B) (international normalized ratio 3.5 to 4.5). Arm A included 258 patients and arm B 245 patients. The two groups were comparable for all baseline characteristics. RESULTS: The outcomes of the study were embolism, valve thrombosis, and major hemorrhage. The median follow-up was 23 months. The two treatments offered similar antithrombotic protection. The incidence of embolic episodes was 1.32 per 100 patient-years (95% confidence interval 0.53 to 2.7) for arm A and 1.48 per 100 patient-years (95% confidence interval 0.59 to 3.03) for arm B. Major hemorrhage occurred in 1.13 per 100 patient-years (95% confidence interval 0.41 to 2.45) for arm A and 2.33 per 100 patient-years (95% confidence interval 1.17 to 4.14) for arm B. Gastrointestinal bleeding was not increased by this combined reduced dose of aspirin and coumarin.

Anticoagulants↗
PubMed1989

[Use of anticoagulants in pregnant women carrying heart valve prosthesis].

Prosthetic heart valves require permanent anticoagulant treatment. In the case of pregnancy, serious problems arise in that coumarin drugs lead to increased incidence of fetal death and malformation. On the other hand, the omission of anticoagulant treatment implies considerable risks of systemic embolism and even of maternal death. Review of the literature and the few cases published so far do not prove that antiplatelet agents are effective and safe and offer sufficient protection against thromboembolism. The use of heparin may reduce the incidence of complications. The authors come to the conclusion that women with prosthetic heart valves should be advised to avoid pregnancy. Biovalves should be applied in those who wish to bear children.

Abnormalities, Drug-Induced↗
PubMed1992

[Mineralization of heart valves].

Mineralization (calcification) of heart valves (mitral, aortic and aortic bioprosthesis) have been analyzed using; histology, x-ray diffraction, infrared spectroscopy, scanning microscopy, atomic absorption and electron microprobe. Obtained results showed the presence of two type of mineralization. First type is represented by grains composed of hydroxyapatite containing admixture of carbonates. This mineralization is seen macroscopically. Second type of mineralization is possible to determine only using chemical methods. It is represented by biological structures containing amount of Ca, P and other elements higher then normal heart valves. This second type of the mineralization conducts to the changes of physical features of the tissue. Both types of calcification develops because of the defects of atomic structure of biological components of heart valves (mainly collagen). These defects show the presence of free atomic bindings i.e. electric potential. Because of this, they are able to react with surrounding free joints, starting calcification. Defects of biological structures of heart valves are the results of infections, mechanical destruction of the valves etc. Calcification may be stopped on different stages of its development: or as secret calcification or may pass to the stage seen as apatite grains.

Adult↗
PubMed1998

[Aortic valve replacement: technique and outcome with artificial heart valves and allografts].

Prosthetic aortic valve replacement has become a highly effective surgical treatment for aortic valve stenosis and aortic valve incompetence. After a properly timed aortic valve replacement, age- and gender-related actuarial survival can be similar to those of a normal healthy population, if serious late valve-related complications do not occur. The perioperative risk of isolated aortic valve replacement approaches 1% to 2% mainly influenced by valve- and patient-related factors such as age, left ventricular function, New York Heart Association class, preoperative hemodynamic and time of operation. Despite a number of various mechanical, bioprosthetic and biological heart valve prostheses, aortic valve replacement remains a palliative surgical treatment. Life-long anticoagulation is required by patients with mechanical heart valve prostheses, and, degeneration and subsequent reoperation is inherent in all bioprosthetic devices. The availability of cryopreserved allograft is limited and the Ross-operation is a technically demanding procedure with a somewhat higher perioperative mortality. Perioperative morbidity after isolated aortic valve replacement is low. A fatal neurological event, the most dreaded complication after aortic valve replacement, is found in about 0.5% of patients. Post-operatively, left ventricular hypertrophy decreases and cardiac dysfunction, reflected by the left-ventricular ejection rate is reversed in most patients, associated with an excellent clinical outcome and an age- and sex-specific normal long-term survival. To offer the most appropriate valve substitute to the individual patient, the debate focus on the question of whether patients benefit from durable mechanical heart valves or a primary anticoagulation-free bioprosthesis. However, there is no difference found between the prostheses types with regard to serious valve related complications such as major thromboembolism and hemorrhage, fatal reoperation and valve-related mortality. The search for an ideal permanent substitute for the aortic valve continues. To date, proper indication, optimal timing of the operation and careful analysis of the late results may help to improve the long-term survival of patients with after isolated aortic valve replacement.

Aortic Valve↗
PubMed1995

[Recommendations for prevention of thromboembolism in heart valve diseases. Working Group on Valvular Heart Disease, European Society of Cardiology].

Thromboembolic events are still a major cause of morbidity and mortality in patients with native valvular heart disease and in patients with prosthetic heart valves. Although the introduction of oral anticoagulation reduced this risk, thromboembolism and anticoagulation-related hemorrhages still represent significant problems in the management of these patients. In this article the guidelines developed by the Working Group on Valvular Heart Disease of the European Society of Cardiology for the management of antithrombotic therapy in heart valve disease are thoroughly discussed. The indication for and intensity of anticoagulation in various clinical situations, the concept of risk factor-adjusted intensity of anticoagulation, and the concept of control of oral anticoagulation with the International Normalized Ratio are presented.

Administration, Oral↗
PubMed2003

Mechanisms of bioprosthetic heart valve calcification.

BACKGROUND: Cryopreserved human heart valves are used in approximately 20% of the tissue heart valve procedures performed annually. The pathophysiology of allograft failure is not fully understood. The authors proposed the hypothesis that the rapid deterioration observed in some allograft heart valve recipients is caused by disruptive interstitial ice damage that occurs during cryopreservation and subsequently leads to accelerated valve degeneration on implantation. METHODS: This hypothesis was tested by comparison of the standard commercial heart valve freezing method of cryopreservation and an ice-free, vitrification method of cryopreservation with fresh controls in a subcutaneous, juvenile rat implant model of calcification. Calcium concentration in explants was determined by atomic absorption spectroscopy. RESULTS: Statistically significant calcification (P<0.05) was observed in both syngeneic and allogeneic cryopreserved valves relative to fresh valves. The ice-free cryopreservation method demonstrated significant reduction of allogeneic heart valve calcification (P<0.01). Comparison of fresh syngeneic and allogeneic grafts at the 3-week time point demonstrated significantly higher calcium content in allograft valve explants (P<0.005). CONCLUSIONS: These findings demonstrate that allogeneic valve calcification is influenced by two factors, the cryopreservation method used and immunogenicity. Alternative cryopreservation methods that avoid ice formation may improve the in vivo performance of cryopreserved allogeneic heart valves.

Animals↗
PubMed2005

Heart valve regeneration.

The valves of the heart cannot regenerate spontaneously. Therefore, heart valve disease generally necessitates surgical repair or replacement of the diseased tissue by mechanical or bioprosthetic valve substitutes in order to avoid potentially fatal cardiac or systemic consequences. Although survival and quality of life is enhanced for many patients treated surgically, currently available valve substitutes remain imperfect. This is especially the case in pediatric applications, where physiologically corrective procedures can be successfully performed, but reoperations are frequently required to replace failed valve substitutes or accommodate growth of the patient. While much work is currently underway to incrementally improve existing valve substitutes, a major impact will require radically new technologies, including tissue engineering or regeneration. The use of engineered tissue offers the potential to create a non-obstructive, non-thrombogenic tissue valve substitute containing living cells capable of providing ongoing remodeling and repair of cumulative injury to the extracellular matrix. Ideally, this would allow growth in maturing recipients. The innovative fabrication of materials and the development of sophisticated methods to repair or regenerate damaged or diseased heart valves requires integration of a diverse array of basic scientific principles and enabling technologies. Thus, heart valve tissue engineering requires an understanding of relationships of structure to function in normal and pathological valves (including mechanisms of embryological development, tissue repair and functional biomechanics), and the ability to control cell and tissue responses to injury, physical stimuli and biomaterial surfaces, through chemical, pharmacological, mechanical and potentially genetic manipulations. These approaches created by advances in cell biology raise exciting possibilities for in situ regeneration and repair of heart valves.

Bioprosthesis↗
PubMedDate not supplied

Diamond-like carbon coating and plasma or glow discharge treatment of mechanical heart valves.

All mechanical heart valves (MHV) are thrombogenic. Application of surface modification technology to reduce the incidence of thrombus formation on MHV is a novel undertaking. This requires collaboration within the bioengineering and cardiothoracic surgery fields. From reviewing results of recent and past investigations, and our own preliminary study with diamond-like carbon coating (DLC) and plasma or glow discharge treatment (GDT) of MHV, we identify and discuss several potentially beneficial effects that may reduce the extent of valve-related thrombogenesis by surface modification. DLC and GDT may affect the surfaces of MHV in many ways, including cleaning of organic and inorganic debris, generating reactive and functional groups on the surface layers without affecting their bulk properties, and making the surfaces more adherent to endothelial cells and albumin and less adherent to platelets. These different effects of surface modification, separately or in combination, may transform the surfaces of MHV to be more thromboresistant in the vascular system.

Animals↗
PubMed2002

Optimizing the tensile properties of polyvinyl alcohol hydrogel for the construction of a bioprosthetic heart valve stent.

Although bioprosthetic heart valves offer the benefits of a natural opening and closing, better hemodynamics, and avoidance of life-long anticoagulant therapy, they nevertheless tend to fail in 10-15 years from tears and calcification. Several authors, including the present ones, have identified the rigid stent as a factor contributing to these failures. The ultimate solution is an artificial heart valve that has mechanical properties that allow it to move in conformity with the aortic root during the cardiac cycle, has superior hemodynamics, is nonthrombogenic, will last more than 20 years, and mitigates the need for anticoagulants. We have identified a polymer, polyvinyl alcohol (PVA) hydrogel, that has mechanical properties similar to soft tissue. The purpose of this research is to match the tensile properties of PVA to the porcine aortic root and to fabricate a stent prototype for a bioprosthetic heart valve with the use of the PVA hydrogel. Specimens of 15% w/w PVA were prepared by processing through 1-6 cycles of freezing (-20 degrees C) at 0.2 degrees C/min freeze rate and thawing (+20 degrees C) at different thawing rates (0.2 degrees C/min and 1 degrees C/min), for different holding times (1 and 6 h) at -20 degrees C. Subsequently tensile tests and stress-relaxation tests were conducted on the specimens. The different holding times at -20 degrees C demonstrated no difference in the result. The slower thawing rate improved the tensile properties but did not produce significant changes on the stress-relaxation properties. The nonlinear stress-strain curve for the PVA after the fourth freeze-thaw cycle matched the porcine aortic root within the physiological pressure range. The stress-relaxation curve for PVA also approximated the shape of the aortic root. The complex geometry of an artificial heart valve stent was successfully injection molded. These results, in combination with other preliminary findings for biocompatibility and fatigue behavior, suggest that PVA hydrogel is a promising biomaterial for implants, catheters, and artificial skin.

Animals↗