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At least 685 records · Page 38Linked to original sources
PubMed2006

Increased sensitivity to warfarin after heart valve replacement.

BACKGROUND: The dosage requirement of warfarin to achieve a given international normalized ratio (INR) often varies considerably between the immediate postoperative period and long-term follow-up in patients with prosthetic heart valves, leading to INR instability. OBJECTIVE: To document the extent of warfarin sensitivity in a prospective study of patients receiving heart valve replacements. METHODS: Clinical and laboratory data regarding anticoagulation for 111 patients who received warfarin following heart valve replacement were collected during their hospital stay (induction period) and between 1 and 3 months after surgery (follow-up period). RESULTS: Mean patient age was 65.39 +/- 10.55 years (range 29-85), with 66 men. The mean INR value during the follow-up period was, on average, 0.21 higher than the induction period (2.81 +/- 0.5 vs 2.6 +/- 0.6; p = 0.007). The mean follow-up warfarin dose was 1.54 mg higher than the mean induction warfarin dose (5.09 +/- 2.03 vs 3.55 +/- 1.94 mg; p < 0.001). The warfarin dose index, which indicates relative sensitivity of warfarin, decreased from 1.16 to 0.65 (p < 0.001). Although the INR values during the induction and follow-up periods were similar, the dose requirement in the follow-up period was, on average, 43% higher than that of the induction period. CONCLUSIONS: Immediately after heart valve replacement, patients are more sensitive to warfarin and should receive a lower warfarin dose during the initial phase of oral anticoagulation treatment. This enhanced sensitivity decreases with time. Patients require frequent monitoring and are likely to need an increase in the warfarin dose to avoid insufficient anticoagulation during the early follow-up period.

Adult↗
PubMed1993

Measurement of beta-thromboglobulin and platelet factor 4 to follow up patients with artificial heart valves.

Efficient antithrombotic therapies are necessary for the prevention of thrombotic complications in patients with artificial heart valves. Antiplatelet drugs are commonly used since platelet activation is a feature frequently found in these pathologic conditions. The measurement of beta TG and PF4 is useful for the diagnosis of platelet activation, which may increase the thrombotic risk. Two commercially available ELISA kits for beta TG and PF4 were tested and compared with the corresponding RIA methods used previously. Coefficients of correlation were 0.976 for beta TG and 0.985 for PF4. Both methods gave identical results, although RIA was expressed in nanograms per milliliter, whereas ELISA results were in international units per milliliter by comparison with International Standards. For both parameters 1 IU/ml was found to be almost equal to 1 ng/ml. beta TG was elevated in the group of patients with heart valves (57.28 IU/ml); so was PF4 but to a lesser extent (11.28 IU/ml). The mean concentrations on a normal population were, respectively, 22.40 (+/- 5.15) IU/ml and 4.10 (+/- 2.02) IU/ml. The monitoring of patients with heart valves allowed the identification of two distinct groups: those who had persistent elevated levels of beta TG and PF4, and those whose levels of the same parameters were in the subnormal ranges. All the thrombotic complications were observed in the first group and were preceded by an elevation of platelet markers. beta TG was the most predictive and correlated closely with the evolution of the clinical state. Cerebrovascular accidents were the commonly observed complications. These patients were treated by hypocoagulant therapy and with antiplatelet drugs.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2005

Predicting ATS Open Pivot heart valve performance with computational fluid dynamics.

BACKGROUND AND AIM OF THE STUDY: In-vitro studies on the ATS heart valve have indicated that valve opening is less in an expanding conduit than in a straight conduit. METHODS: Bileaflet valve behavior was studied using a new computational fluid-structure interaction model. A three-dimensional model of the ATS valve was studied in two geometries, simulating the valve in a geometry with sudden expansion downstream of the valve, and in a straight conduit. Mitral and aortic flow patterns were simulated. RESULTS: The ATS valve in the expanding geometry showed opening to a maximum angle of 77.5 degrees; this was confirmed in previous clinical and in-vitro studies. The mean and maximum transvalvular Doppler pressure gradients were 1.1 and 4.3 mmHg, respectively. The maximum shear stress calculated on the leaflet was 25 Pa. Maximum opening of the valve was achieved in the straight conduit; with mean and maximum pressure gradients of 2.1 and 4.6 mmHg, respectively. The maximum shear stress calculated on the leaflet was 35 Pa. CONCLUSION: The results of this numerical study confirmed that valve hemodynamics and leaflet motion were dependent on the geometrical conditions of the valve: the presence of a diverging flow influenced the maximum opening angle of the valve leaflets. This model could be used to predict pressure gradients, effective orifice area, performance index and shear stress loading of mechanical heart valves, and in future will serve as a major research tool to characterize the hemodynamics of existing and new mechanical heart valves.

Aortic Valve↗
PubMed2003

[Myocardial protective effect of L-carnitine in cardioplegia solution on patients undergoing heart valve replacement operation].

OBJECTIVE: To investigate the myocardial protective effect of L-carnitine as an ingredient of cardiac arresting solution in the process of heart valve replacement operation. METHODS: 69 cases undergoing heart valve replacement with cardiopulmonary bypass (CPB), 47 males and 22 females, aged 48.17 +/- 14.22 (16 approximately 74 years), were divided into 3 groups: test group I (n = 22, 12 g/L L-carnitine was put in the St. Thomas II cold crystal cardiac arresting liquid), test group II (n = 24, 6 g/L L-carnitine was put in the St. Thomas II cold crystal cardiac arresting liquid), and control group (n = 23, no L-carnitine was put in the St. Thomas II cold crystal cardiac arresting liquid). Before operation, 20 minutes after the beginning of shunt, after the finish of shunt, and 8 hours, one day, 3 days, and 7 days after operation venous blood was drawn to test the serum cardial tropnin I (cTnI), aspartate transaminase, lactate dehydrogenase, creatine kinase (CK) and CK-MB isozyme. Heart color ultrasonography was conducted to test the cardiac index (CI) and left heart ejecting fraction (EF) one day before operation and 7 days after operation. Before shunt and by the end of intracardiac procedure a bit of myocardial tissue was taken to undergo electron microscopy. The amounts of vaso-active drugs, such as dopamine and dobutamine, used postoperatively, and the postoperative cardiac auto-rebeating rate were recorded. RESULTS: The Amounts of vaso-active drugs used after operation was 329 +/- 54 mg in the test group I and 339 +/- 47 mg in the test group II, both significantly less than in the control group (669 +/- 56 mg, both P < 0.01) without a significant difference between the 2 test groups. Since the end of CPB to 3 days after operation, the serum levels of cTnI, aspartate transaminase, lactate dehydrogenase, CK and CK-MB isozyme were significantly lower in the 2 test groups than in the control group (P < 0.05 or P < 0.01). The serum level of cTnI in test group I was significantly lower than in the test group II (5.71 +/- 1.14 ng/ml vs 7.87 +/- 1.89 ng/ml 1 day postoperatively (P < 0.05), and 5.01 +/- 0.89 ng/ml vs 7.53 +/- 1.43 ng/ml 3 days postoperatively (P < 0.05). The postoperative cardiac auto-rebeating rate was 87.9% in the test group I and 74.3% in the test group II, both significantly higher than that in the control group (45.7%, P < 0.05 and P < 0.01). Heart color ultrasonogram showed that 7 days postoperatively the CI index was 2.86 +/- 0.55 and 2.74 +/- 0.56 in the 2 test groups, significantly higher than that in the control group (2.11 +/- 0.35, both P < 0.05), and the left heart EF were 64.3 +/- 8.6 and 59.1 +/- 6.7 in the 2 test groups, both significantly higher than that in the control group (51.7 +/- 4.9, both P < 0.05). Electron microscopy showed only slight swelling of mitochondria in the cardial cell and the myocardial fiber was intact by the end of operation in the 2 test groups without significant difference between these 2 groups, however, in the control group swelling of mitochondria with vesicle formation, fissure of part of mitochondrial ridges, and disappearance of glycogen particles were found. CONCLUSION: Antegrade coronary perfusion of L-carnitine has a good protective effect on myocardium and is worth spreading for heart valve replacement patients with cardiopulmonary bypass.

Adolescent↗
PubMed2005

Low-dose anticoagulation in Chinese patients with mechanical heart valves.

The aim of this study was to provide guidelines for optimal anticoagulation in Chinese patients after mechanical heart valve replacement. A Carbomedics valve was implanted in 178 patients between July 2000 and July 2003. During follow-up, 22 bleeding events and 1 thromboembolic complication occurred. The linearized rates of bleeding and thromboembolism were 5.83% and 0.26% per patient-year, respectively. The linearized mortality rate was 0.79% per patient-year. The final mean international normalized ratio (INR) was 1.68+/-0.38, however there was a significant variation between the early and late periods of follow-up. For Chinese patients with mechanical heart valves, bleeding was the major complication rather than thromboembolism. Low-dose anticoagulation (international normalized ratio 1.4-2.0) could markedly decrease bleeding and effectively prevent thromboembolism. As the INR was most unstable in the first postoperative month, re-examination of patients in this period is critical.

Adolescent↗
PubMed1987

Reoperations for malfunction of heart valve prostheses, especially with endocarditis.

Following the increasing number of patients with heart valve replacement and an extended indication (older age groups, acute infective endocarditis, multivalvular procedures) the indicence of malfunction of valve prostheses is continuously growing. The prognosis of patients with a malfunctioning prosthesis mainly depends on early diagnosis and adequate therapy. In a retrospective study (1970 to 1984) 3,533 implanted heart valve prostheses were followed up and the cases with malfunction (n = 150; 4.2%) were analyzed. During the follow-up period after 1963 mitral valve replacements (MVR) there were 78 cases of malfunction (4.6%), after 1806 aortic valve replacements (AVR) 73 (4.1%), and after 34 tricuspid valve replacements (TVR) 4 malfunctions (11.8%). These malfunctions concerned periprosthetic leakages (n = 65), prosthetic endocarditis (n = 42), prosthetic valve thrombosis (n = 13), mechanical dysfunction including bioprosthetic degeneration (n = 17), valve related hemolysis (n = 3), and unsatisfactory hemodynamics (n = 10). Special attention was turned to the problem of prosthetic endocarditis (1963-1984) found in a total of 71 patients following 3,878 prosthetic valve replacements (1.9%). In 42 reoperated cases (1970-1984) the causing microorganisms were analyzed, demonstrating staphylococci in a leading position. Secondary complications and additional risk factors are discussed. There has been no change concerning the basis and the strategy of management for prosthetic endocarditis for many years: After a short time of conservative management with tested antibiotics, early reoperation and exchange of the prosthesis seems to be the optimal therapy, despite a distinctly high postoperative mortality (17%).(ABSTRACT TRUNCATED AT 250 WORDS)

Aortic Valve↗
PubMed1992

Mycobacterial infections following heart valve replacement.

Mycobacterial infection is an uncommon but very serious complication of heart valve replacement and other forms of cardiac surgery. Tuberculosis has been a rare complication of valve replacement in the industrially developed countries owing to the low incidence of that disease in such countries. Most reported cases are associated with the insertion of human allograft valves. Valvular tuberculosis could become a more serious problem if heart valve replacement surgery is used to any extent in countries where tuberculosis is common. The majority of other mycobacterial infections occurring after heart surgery have, for unknown reasons, been due to the rapid growers M. chelonae and M. fortuitum. Porcine xenograft valves have been contaminated by M. chelonae, possibly during manufacture as this is not a natural pathogen of pigs. A minority of patients receiving valves known to be contaminated by M. chelonae subsequently developed valve disease. Mycobacterial disease following insertion of mechanical valves is a very uncommon occurrence but the prognosis is poor. There have been several outbreaks of infection of the sternotomy wound by M. chelonae and M. fortuitum and, although the prognosis is better than for mycobacterial endocarditis, treatment, especially for infections due to M. chelonae, often involves extensive debridement including removal of the entire sternum. In view of the poor response to therapy, prevention by avoidance of contamination of all surgical materials, including implanted valves, by environmental mycobacteria is of paramount importance.

Heart Valve Prosthesis↗
PubMed1977

[Antibodies to heart valve fibroblasts in the sera of rheumatic patients].

The antibodies reactive in immunofluorescence with the fibroblasts of human and bovine heart valves were isolated from the rheumatic patients' sera with the aid of immunoadsorbent prepared from human heart valve tissue. No reaction between the antibodies and the fibroblasts of the interstitial connective tissue of the myocardium was observed. It seems that the fibroblasts of the heart valves and the myocardium contain different antigens; the presence of common antigenic components in human and bovine valve fibroblasts is shown.

Antibodies↗
PubMed1992

Penetration of ofloxacin into heart valves, myocardium, mediastinal fat, and sternal bone marrow in humans.

Ofloxacin penetration into heart tissue (valve and myocardium), mediastinal fat, and sternal bone marrow was the object of a prospective nonrandomized study. Thirty-six patients undergoing mitral and/or aortic valve replacement were included. Patients were divided into two groups of 18 patients each. Group 1 patients were administered a single 400-mg intravenous dose of ofloxacin over a 30-min period upon anesthesia (n = 6) or at 1 h (n = 6) or 6 h (n = 6) prior to surgery. Group 2 patients received a 200-mg oral dose of ofloxacin every 12 h during the 48 h preceding surgery. In this group, the final dose of ofloxacin was administered 3 h (n = 9) or 8 h (n = 9) before anesthesia. Plasma and tissue ofloxacin concentrations were assayed by high-pressure liquid chromatography. In group 1 patients, the peak level in plasma was 15.9 +/- 2.5 micrograms/ml. Peak ofloxacin levels in tissue were reached by hour 1 and were 8.89 +/- 2.16 micrograms/g in myocardium and 5 +/- 0.75 micrograms/g in heart valves. A significant decrease in ofloxacin levels in heart valve tissue and sternal bone marrow was observed after hour 3. Nevertheless, ofloxacin myocardial, heart valve, and sternal bone marrow levels remained higher than the MICs for the usually susceptible pathogens for at least 3 h. In group 2 patients, myocardial levels were long lasting (6.46 +/- 1.92 micrograms/g [4 to 8 h] and 5.92 +/- 0.95 micrograms/g [8 to 12 h]) and remained higher than those observed in the other tissues over the entire study period. A progressive but insignificant decrease in ofloxacin heart valve levels was observed (from 2.46 +/- 0.40 micrograms/g [4 to 8 h] to 1.57 +/- 0.22 micrograms/g [8 to 12 h]). In both groups, concentration in mediastinal fat were lower and tended to decrease with time. These were 1.83 +/- 0.61 micrograms/g with the first hour and 0.85 +/- 0.43 micrograms/g between hours 8 and 12 in group 1 and 1.74 +/- 0.52 micrograms/g between hours 4 and 8 and 0.67 +/- 0.11 micrograms/g between hours 8 and 12 in group 2. In conclusion, satisfactory diffusion of ofloxacin into heart tissue seems to favor use of the drug in the treatment of bacterial endocarditis due to susceptible pathogens. Furthermore, the progressively decreasing concentrations observed in heart valve and sternal bone marrow and the poor levels achieved in mediastinal fat suggest the need for renewing injection 3 h following initial infusion if the drug is used as an antibiotic prophylactic agent during cardiovascular surgery.

Adipose Tissue↗
PubMed1985

[Respiratory disorders in acquired heart valve defects with various degrees of heart failure].

The respiratory disorders with various degrees of cardiac insufficiency were studied in 226 patients with acquired heart defects. The indices characterizing the external respiration, alveolar ventilation, alveolar-capillary diffusion, functional and real intrapulmonary shunts and acid-base state were followed up. The results from the numerous indices followed up significantly express the progressive intensification of respiratory disorders with the advancement of cardiac insufficiency. In stage I of cardiac insufficiency, prior to the manifestation of clinical signs of pulmonary stasis, distinct disturbances were established in DLCO, Qs/Qt, PaO2, which, to a great extent, characterize the early respiratory disorders and have a definite importance for the diagnostic and therapeutic behaviour. Most severe are the functional disorders in respiratory system in stage II B of cardiac insufficiency.

Acid-Base Equilibrium↗
PubMed1988

Concentrations of flucloxacillin in heart valves and subcutaneous and muscle tissues of patients undergoing open-heart surgery.

Thirty-seven patients were given a single, 2-g intravenous bolus injection of flucloxacillin prior to open-heart surgery. Within 12 h, flucloxacillin concentrations in serum and heart valves declined from 125.2 to 4.4 micrograms/ml and from 16.5 to 3.7 micrograms/g, respectively. Concentrations in subcutaneous tissue and muscle were almost identical, declining from 14.7 or 14.2 micrograms/g to undetectable levels after 8 to 10 h.

Cardiac Surgical Procedures↗
PubMed1994

Holographic interferometry: a new technique for in vitro investigations of prosthetic heart valves.

At present there are many different prosthetic models available for heart valve replacement. Postimplant dysfunction resulting from material failure has been reported in several prostheses. The prime cause of these defects is hidden abnormalities in the valve construction or materials. In order to detect these defects before implantation, preoperative non-destructive testing of individual valves is proposed. For this purpose, holographic interferometry has been applied which is a non-contact, non-destructive, highly sensitive, three-dimensional measurement technique. Samples of different types of prosthetic heart valve, both mechanical and biological, were mounted in a specially developed test chamber with optical access from four sides. The valves were loaded with a static liquid pressure of 2.5-15 kPa. Deformations of the valves as a result of small pressure differences (0.5-15% of the static pressure) applied between two exposures were recorded by double-exposure holography. A fringe pattern superimposed on the image of the valve reconstructed from the hologram clearly indicates the presence of defects in the valve material.

Heart Valve Prosthesis↗
PubMed2000

Prosthetic heart valves: evaluation of magnetic field interactions, heating, and artifacts at 1.5 T.

The purpose of this study was to use ex vivo testing techniques to determine the magnetic resonance imaging (MRI) safety aspects for 32 different heart valve prostheses that had not been evaluated previously in association with the 1.5-T MR environment. Ex vivo testing was performed using previously described techniques for the evaluation of magnetic field interactions (deflection angle and torque), heating [gel-filled phantom and fluoroptic thermometry; 15 minutes of MRI at a specific absorption rate (SAR) of 1.1 W/kg], and artifacts (using gradient echo and T1-weighted spin-echo pulse sequences). Thirteen heart valve prostheses displayed interactions with the magnetic field. However, these magnetic field interactions were considered relatively minor. Heating was < or =0.8 degrees C for these implants. Artifacts varied from mild to severe depending on the amount and type of metal used to make the particular heart valve prosthesis. For these 32 different heart valve prostheses, the relative lack of substantial magnetic field interactions and negligible heating indicate that MR procedures may be conducted safely in individuals with these implants using MR systems with static magnetic fields of 1.5 T or less.

Artifacts↗
PubMedDate not supplied

Coagulation activation is associated with interleukin-6 plasma levels in patients with mechanical prosthetic heart valves.

BACKGROUND: The intensity of oral anticoagulant therapy in patients with mechanical heart valves is evaluated and controlled by the International Normalized Ratio (INR). However, intravascular coagulation activation can occur despite normal INR values and is related to clinical events. Here, anticoagulation efficiency was assessed by sensitive techniques and potential determinants of coagulation activation were identified. PATIENTS AND METHODS: Forty patients were enrolled after they had undergone mechanical aortic valve replacement. As markers of coagulation activation, plasma concentrations of the D-dimer antigen were prospectively measured. The patients were classified into quartiles according to the D-dimer plasma antigen level. Serum concentrations of the inflammatory markers C-reactive protein (CRP) and Interleukin (IL)-6 were also assessed. RESULTS: The D-dimer levels varied significantly despite therapeutic INR values. In patients with high D-dimer levels, the serum concentrations of IL-6 were significantly increased (top vs. bottom quartile, median, 1.35 versus 0.80 pg/ml; p<0.05), suggestive of subclinical inflammation. There was no association between the D-dimer levels and age, sex, cardiovascular risk factors or time since valve replacement. CONCLUSION: Coagulation activation and inflammation are associated with mechanical heart valves. The D-dimer antigen and IL-6 may be more sensitive than INR and CRP to detect these states and, therefore, could prove valuable additional markers, e.g., in determining the efficacy of new anticoagulant drugs.

Aged↗
PubMed1997

Effect of different oral anticoagulant intensities on prothrombin fragment 1 + 2 in Thai patients with mechanical heart valve prostheses.

The minimal intensity of oral anticoagulant required for antithrombotic protection in patients with a mechanical heart valve is still debatable, and that of the Westerner may not be directly applied to Thai patients. Our preliminary clinical review suggested that International Normalized Ratio (INR) 2-3 might be enough but it needs further supporting evidence. Therefore, we studied the effect of different anticoagulant intensities, expressed as INR, on the in vivo coagulation activation by measuring prothrombin fragment 1 + 2 (F1 + 2) in 116 patients with mechanical heart valve replacements. The patients had received warfarin for not less than one month with different intensities. The mean +/- S.D. of F1 + 2 level in 30 normal controls was 0.7 +/- 0.17 nmol/L. After excluding two outliers, the maximum linear correlation between INR and F1 + 2 was -0.658 (p < 0.001) when only patients whose intensities were lower than INR3 were taken into account. Adding more data from the patients having higher intensities decreased the correlation coefficient. The patients were subsequently classified by INR values in the range INR 1.1-1.9, 2-3 and 3.1-4.2. The F1 + 2 in each group was 0.6 +/- 0.30, 0.28 +/- 0.13 and 0.24 +/- 0.13 nmol/L respectively. The F1 + 2 in the first group did not differ from normal (p = 0.119) but was higher than the others (p = 0.000). The latter two groups had no difference between them (p = 0.112). Hence, from the laboratory point of view, we did not see additional benefit in the reduction of thrombin activation by the anticoagulant intensities higher than the range INR 2-3. The evidence supported that this therapeutic range might be enough for Thai patients with mechanical heart valves.

Adolescent↗
PubMed2001

Hydrodynamic function of a biostable polyurethane flexible heart valve after six months in sheep.

Survival to six months for sheep with a non-biostable polyurethane mitral heart valve prosthesis has been reported previously, however, with surface degradation and accumulation of calcified fibrin/thrombus that impaired leaflet motion and compromised hydrodynamic function. Newly available biostable polyurethanes may overcome this problem. Six adult sheep with biostable polyurethane trileaflet heart valve prostheses of documented hydrodynamic performance, implanted in the mitral position, were allowed to survive for 6 months. Explanted valves were photographed, resubmitted to hydrodynamic function testing, and studied by light and electron microscopy. Explanted valves were structurally intact and differed little in appearance from their preimplant state. Hydrodynamic testing showed no deterioration in pressure gradient or energy losses compared with pre-implant values. Biostable polyurethanes demonstrated improved blood compatibility leaving leaflets flexible and valve function unimpaired. Biostable polyurethanes may thus improve prospects for prolonged function of synthetic heart valve prostheses.

Animals↗
PubMed2000

[Cardiac energy metabolism in heart valve diseases with 31P MR spectroscopy].

PURPOSE: Heart valve disease combined with left ventricular hypertrophy leads to derangements in cardiac energy metabolism, which can be detected non-invasively by 31P-MR-spectroscopy. The purpose of the present study was to examine whether the derangements in cardiac metabolism are reversible after surgical valve replacement. PATIENTS AND METHODS: 10 healthy volunteers and 10 patients with aortic stenosis (pressure gradients > 60 mmHg) were included. For assessment of energy metabolism, 31P-MR spectra were obtained with a double oblique 3D-CSI technique (voxel size 25 cm3). In 5 of 10 patients, follow-up examination was performed 3 months after surgical valve replacement (SVR). Left ventricular (LV) function was analyzed by cine MRI. RESULTS: Before SVR the myocardial phosphocreatine to adenosinetriphosphate (PCr-ATP) ratio was significantly (p = 0.0002) reduced to 0.80 +/- 0.25 in patients compared to 1.65 +/- 0.21 in volunteers. 3 months after SVR, LV mass had significantly (p = 0.04) decreased from 238 +/- 33 g to 206 +/- 47 g. At the same time a significant (p = 0.04) increase of the PCr-ATP ratio from 0.80 +/- 0.25 to 1.28 +/- 0.22 was observed. A slight, but not significant, reduction of the phosphodiester ATP ratio was observed before SVR, with a trend towards normalization after SVR. CONCLUSIONS: After SVR, the deranged energy metabolism shows a trend towards normalization. Further follow-up is necessary to determine whether complete normalization of the energetic derangement can be observed over longer periods of time following SVR.

Adult↗