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 973 records · Page 54Linked to original sources

PubMed2001

Cerebral hypoperfusion in immediate postoperative period following coronary artery bypass grafting, heart valve, and abdominal aortic surgery.

Perioperative levels of jugular bulb oxyhaemoglobin saturation (Sj(O(2))) and lactate concentration (Lj), and postoperative duration of Sj(O(2))<50% were compared between patients undergoing coronary artery bypass grafting (CABG) (n=86), heart valve (n=14) and abdominal aortic (n=16) surgery. Radial artery and jugular bulb blood samples were aspirated after induction of anaesthesia, during re-warming on cardiopulmonary bypass (CPB) (36 degrees C), on arrival in the intensive care unit (ICU) and, subsequently, at 1, 2 and 6 h after ICU admission. Most patients having heart surgery were hypocapnic at 36 degrees C on CPB. Following CABG and heart valve surgery, many patients were hypocapnic whereas after abdominal aortic surgery, most were hypercapnic. During CPB and postoperatively, Sj(O(2)) and Lj were significantly correlated to Pa(CO(2)) and the arterial concentration of lactate (La) respectively (P<0.05). After correction for arterial carbon dioxide tension (Pa(CO(2))) and La, there were no significant changes in Sj(O(2)) or Lj on CPB. Postoperatively, having corrected for Pa(CO(2)), there were significant effects on Sj(O(2)) over all groups as a result of time from surgery (P<0.001) and its interaction with operation type (P<0.001). Following correction for La, there were no postoperative effects on Lj. No significant differences (P=0.2) in duration of Sj(O(2))<50% existed between patients undergoing CABG (1054 (82) min), abdominal aortic (893 (113) min) and heart valve (1073 (91) min) surgery. The lack of significant reciprocal effects on Lj combined with the frequency of hypocapnia and strong influence of Pa(CO(2))()on Sj(O(2)), suggest that Sj(O(2))<50% during CPB and after cardiac surgery represents hypoperfusion as a consequence of hypocapnia rather than cerebral ischaemia.

Aged↗

PubMed1987

Hemodynamic changes during dental extraction and post-extraction bleeding in patients with prosthetic heart valves.

Hemodynamic changes during dental extraction and postextraction bleeding were retrospectively evaluated in patients with prosthetic heart valves. It was found that the rate pressure product had a higher value in the period of anesthesia and during dental extraction. There was a tendency for a high RPP difference corresponding to an increased incidence of ECG changes, such as ST-T, QRS, P, and tachycardia. ECG changes were frequently observed high in procedures which required high doses of local anesthetic at one time or when multiple dental extractions were undertaken, whereas they seemed to have no positive relation to the number of heart valves replaced. Approximately 87% of the extractions were carried out under continuous anticoagulant therapy with a pretreatment coagulability level, of which 32% had bleeding during the first 24 h.

Adult↗

PubMed1997

Anticoagulant control in the first three months after mechanical heart valve replacement.

To establish the precision of anticoagulant control in the first three months after mechanical heart valve replacement, 53 patients from a consecutive series of 91 were telephoned and asked to read out their anticoagulation record. The levels of international normalised ratio (INR) were analysed by Rosendaal's method. Twenty-nine per cent of patient days were spent with an INR in the recommended range of 3.0-4.5. Warfarin dosage was increased at a median INR of 2.1 (interquartile range 1.7-2.3), unchanged at 2.7 (interquartile range 2.3-3.1) and decreased at 4.3 (interquartile range 3.6-5.1). Anticoagulant control is poor in the first three months after mechanical heart valve replacement. Data on the INR at which warfarin dosage is changed suggest either that recommended guidelines are not being followed or a reluctance to increase the dosage in patients receiving inadequate anticoagulation.

Aged↗

PubMed1995

Numerical simulation of instantaneous backflow through central clearance of bileaflet mechanical heart valves at closure: shear stress and pressure fields within clearance.

Instantaneous backflow through central clearance of bileaflet heart valves at the instant of closure is investigated. An Edwards-Duromedics valve in the mitral position is employed to measure the transient pressures near the entrance and exit region in an in vitro flow chamber. A region surrounding the clearance is modelled, and two-dimensional quasi-steady-state numerical simulations are performed, with the measured transient pressure difference across the clearance as a driving force for the flow. The results show that pressure difference several times larger than the driving pressure used to close the valve is established across the clearance for about 0.5 ms at the moment of closure. The resulting average wall shear stress is an order of magnitude larger than the turbulent Reynolds stresses reported distal to the valve during opening. A local jump in the shear stress distribution and fall in the pressure distribution are observed at the entrance region. Rounding of the corners in the channel entrance attenuates these spikes. The results of the study indicate that backflow through clearance at closure may be one reason for the haemolysis and thrombosis associated with mechanical heart valves, despite the short duration of the flow field.

Heart Valve Prosthesis↗

PubMed2002

Pregnancy and mechanical heart valves replacement; dilemma of anticoagulation.

OBJECTIVES: To establish a uniform anticoagulation regimen for pregnant patients with mechanical heart valves taking into account the socio-economic background and to evaluate the incidence of anticoagulant related complications. METHODS: A retrospective study on 63 pregnancies in 21 women with mechanical heart valves was evaluated. These pregnancies were divided into two groups: Group I (n=42) received oral anticoagulants throughout pregnancy and Group II (n=21) received subcutaneous heparin in the 1st trimester and oral anticoagulants for the rest of pregnancy period. Both groups received heparin at time of delivery. RESULTS: There was no case of coumarin embryopathy seen and there was no maternal death. Life threatening valve thrombosis occurred in two patients who were both from Group II and needed emergency re-replacement. Group I had a higher incidence of spontaneous abortion than Group II although this was not statistically significant. CONCLUSIONS: The role of coumarin embryopathy has been overstated. We recommend the use of oral anticoagulants throughout pregnancy especially in countries with similar socio-economic background.

Administration, Oral↗

PubMedDate not supplied

Controversies in antithrombotic therapy for patients with mechanical heart valves.

Current anticoagulation guidelines for patients with mechanical heart valves are based on studies that are seriously flawed in that they used prothrombin time ratios rather than the international normalized ratio (INR) and failed to consider the level of anticoagulation actually achieved. Available data suggest that the appropriate INR range varies according to risk factors and that "tight control" of the INR is of critical importance in reducing thromboembolic and hemorrhagic events. Whether antiplatelet therapy adds benefit to an appropriately controlled level of anticoagulation is not clear. During pregnancy, warfarin is contraindicated; adjusted-dose heparin is recommended by published American and European guidelines. Even so, one small study suggests that this may be inadequate. Topical antifibrinolytic agents can negate the need to alter systemic anticoagulation during dental surgery.

Anticoagulants↗

PubMedDate not supplied

Closing behavior of a new bileaflet mechanical heart valve.

Recently, the in vivo cavitation potential has become a primary concern among manufacturers of new mechanical heart valves (MHV). An experimental/computational program was designed to investigate each of the flow parameters involved. It was established that the closing velocity of the leaflet holds the key to MHV cavitation. One of the novel concepts of the new bileaflet mechanical heart valve (1205-MHV) was its ability to operate with a relatively small angular excursion that led to a much smaller closure velocity at impact (as compared with control valves). This is believed to significantly reduce the cavitation potential. The 1205-MHV is characterized by a longer valve body, with the hinges protruding further upstream. The unique design allows the valve the freedom to open as much as 90 degrees. The closure velocities are reduced by a smaller leaflet excursion (50 degrees), combined with a floating hinge that allows absorption of part of the impact energy at closure. The impact velocities of the 1205-MHV leaflets at closure were measured by a laser sweeping technique that monitored the leaflet closing motion with a precision of 5 microseconds within the last 3 degrees before impact. The 27 mm 1205-MHV (the largest size) was tested in the program by mounting the valve in the mitral position of a physiologic mock circulatory loop. The valve was tested at 70, 90, and 120 bpm. The results were compared with those of a St. Jude Medical 29 mm MHV. The closure velocities measured with the 1205-MHV were significantly lower than those measured with the control valve.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗

PubMed1994

An in-vitro investigation of prosthetic heart valve cavitation in blood.

Vapor cavities produced by low pressure fluid flow conditions have been observed in the vicinity of mechanical heart valves for many years. As cavities collapse during pressure recovery, they can produce stresses large enough to cause pitting of the valve occluders and lysing or activation of blood cells. To date, no method has been presented for the quantification of mechanical heart valve cavitation in blood because it has only been detected optically in transparent blood analog fluids. This paper describes a novel method for quantifying cavitation intensities in opaque fluids such as blood. It is based on the detection of high frequency pressure oscillations (35-350 kHz) at a location 4.5 cm proximal to a Björk-Shiley monostrut mitral valve in a mock circulatory loop driven by a Penn State Electric Ventricular Assist Device. The pressure oscillations which result from cavity collapse are used to quantify cavitation intensities in blood. One time domain and three frequency domain parameters have been developed to quantify cavitation intensity during a single valve closure event and over an ensemble of closure events. The time domain parameter is the Root Mean Squared (RMS) value of the pressure signal after it has been high-pass filtered at 35 kHz. The other three parameters are derived from the power spectrum of the pressure signal. One is the maximum value of the power spectrum between 100 and 200 kHz, another is the area under the power spectrum between 35 and 400 kHz, and the last is the volume under a 3-dimensional time vs. frequency vs. power spectrum plot. The parameters are averaged over a random sample of pressure traces to determine an average cavitation intensity for each operating condition studied. In addition, cavitation pressure fluctuations and hemolysis rates were determined simultaneously at several different mock flow loop operating conditions using porcine blood, and the relationships between various measures of cavitation intensity and the associated index of hemolysis have been established. Hemolysis was shown to increase with cavitation intensity.

Animals↗

PubMed1990

Trial of different intensities of anticoagulation in patients with prosthetic heart valves.

We compared the efficacy and complications of anticoagulation with warfarin in 258 patients with prosthetic heart valves treated with regimens of "moderate intensity" (prothrombin-time ratio, 1.5; international normalized ratio, 2.65) or "high intensity" (prothrombin-time ratio, 2.5; international normalized ratio, 9) in a prospective, randomized study. The two patient groups were followed up for 421 patient-years and 436 patient-years, respectively. Eleven patients were lost to follow-up. Thromboembolism occurred with similar frequency in the two groups (4.0 and 3.7 episodes per 100 patient-years, respectively), but there was a total of 6.2 bleeding episodes per 100 patient-years in the moderate-intensity group, as compared with 12.1 episodes in the high-intensity group (P less than 0.002). There were 5.2 episodes of minor bleeding per 100 patient-years in the moderate-intensity group, as compared with 10.1 episodes in the high-intensity group (P less than 0.01). Major bleeding was also more common in the high-intensity group (2.1 episodes per 100 patient-years--including the only two fatal hemorrhages--as compared with 0.95 episode in the moderate-intensity group), but the difference was not statistically significant. We conclude that a moderate anticoagulant effect (prothrombin-time ratio, about 1.5) in patients with a mechanical prosthetic heart valve offers protection equivalent to that of more intensive therapy, but at a significantly lower risk.

Adolescent↗

PubMed2004

[The influence of hereditary thrombophilic mechanisms on the degree of permanent intravascular coagulation in patients with artificial heart valves].

The genotyping of 40 patients with artificial heart valves (AHV) was performed after prosthesis of the mitral and aotic valves with bicuspid AHV (Medinzh-2 and CarboMedics). The patients took phenylin and varfarin. The patients' genotype was estimated by the thrombophylic genes: factor V Leiden (FVL), prothrombin G20210A, methylene tetrahydrofolate reductase C677T, G/A--455FGB, 4G/5G PAI-1, PI A1/A2 GPIIIa. The genes determining the thrombocytic activity or the vascular wall state substantially influence the third degree of the intensity of the permanent intravascular coagulation (PIC-3) independent of the degree of correction of hemostasis of oral anticoagulants. The addition of anti-aggregants to therapy is the only that can normalize functional activity of thrombocytes in patients with AHV having such defects. The laboratory detection of the genetic defects is of great practical importance for the determination of risk groups of formation of PIC-3 and the strategy of antithrombotic protection of patients with AHV.

Anticoagulants↗

PubMed2003

Statistical analysis of the results of heart valve replacement.

A variety of statistical methods can be used to analyze the results of heart valve replacement. In this review, we illustrate the methodology and the application of the techniques that are most widely used. For early events, univariate analysis and multivariate logistic regression are illustrated. For late (time-related) events, nonparametric methods (Kaplan-Meier and cumulative incidence or 'actual' analysis), parametric methods (based on the exponential, Gompertz and Weibull distributions) and semiparametric methods (Cox proportional hazards) are illustrated.

Aged↗

PubMed1995

Left ventricular function in heart valve surgery: a multidisciplinary challenge.

Between January 1988 and December 1994, 4,097 patients underwent heart valve replacement at the Heart Center North Rhine-Westfalia, Bad Oeynhausen, 1,388 (33.8%) of them suffered from impaired left ventricular (LV) function. Overall hospital mortality was 2.3% (n = 95). In the poor LV function group it was 1.8% (n = 25). There was a significant increase of mortality from 1.5% in patients younger than 60 years to 4.9% in patients 80 years of age and older. Reoperations and emergency operations showed an additional increase of mortality each: 6.2% and 18.2%, respectively. Medium term survival (maximum 48 months) was assessed in a group of 2,006 patients operated between January 1991 and December 1993. The cumulative mortality for patients with poor LV function (n = 148) was 12.8%, whereas for those with normal LV function it was 6.1%. Our data suggest that left ventricular function is of minor importance as far as primary operative results are concerned. In long term follow up patients with valve replacement and poor LV function show an increased mortality mainly due to cardiac causes.

Adolescent↗

PubMed2000

Three-dimensional color Doppler reconstruction of intracardiac blood flow in patients with different heart valve diseases.

An improved perception of the magnitude and dynamics of intracardiac flow disturbances has been made possible by the advent of 3-dimensional (3-D) color Doppler, a new diagnostic procedure developed at our institution. This study describes the new insights derived from 3-D reconstruction of color Doppler flow patterns in patients with different heart valve diseases. The color Doppler flow data from 153 multiplanar transesophageal or transthoracic echocardiographic examinations has been obtained from 133 patients with heart valve disease; 73 patients had mitral regurgitation, 15 had mitral stenosis, 18 had aortic regurgitation, 26 had aortic stenosis, and 21 patients had tricuspid regurgitation. Four patients had pulmonary regurgitation associated with mitral valve disease. The 3-D reconstructions of color Doppler flow signals were accomplished by means of the "Heidelberg Raytracing model," developed at our institution. The 3-D color Doppler reconstructions were obtained in all patients. The 3-D images revealed for the first time the complex spatial distribution of the blood flow abnormalities in the heart chambers caused by different heart valve diseases. New patterns of intracardiac blood flow disturbances were observed and classified. Three-dimensional color Doppler provides a unique noninvasive method that can be easily applied for studying intracardiac blood flow disturbances in clinical practice.

Aortic Valve Insufficiency↗

PubMed1995

Cost-effectiveness and efficacy of an on-site homograft heart-valve bank.

OBJECTIVE: To compare the performance and cost-effectiveness of cryopreserved homograft cardiac valves prepared on site to valves prepared commercially. DESIGN: A review of all patients who received homograft heart valves between January 1990 and December 1993, with cost-effectiveness analysis. Follow-up ranged from 1 to 37 months (mean 12 months). SETTING: Tertiary-care adult and pediatric hospitals. PATIENTS: All consecutive patients receiving homograft heart valves in either the aortic or right ventricular outflow tract (RVOT) position since on-site preparation of cryopreserved cardiac valves began in 1990. Forty-three patients received 47 homograft valve replacements: 18 in the aortic position and 29 in the RVOT position. No patients were lost to follow-up. MAIN OUTCOME MEASURES: Valve function as assessed by patient survival, actuarial freedom from reoperation and Doppler echocardiographic assessment of transvalvar gradients and valvar insufficiency. Cost-effectiveness as assessed by a formal evaluation of on-site costs compared with current prices for commercially prepared valves. RESULTS: There were four operative deaths but no late deaths. Four valves were removed. Freedom from reoperation at 3 years was 100% for aortic valve replacement and 85% for RVOT reconstruction. Echocardiographic follow-up of 34 of the remaining 39 patients showed mild or no insufficiency in 24 valves, moderate insufficiency in 8 valves and severe, but not clinically significant, insufficiency in 2 valves. The cost of on-site preparation of the valves was $1363 compared with $5040 for the commercially prepared valves, a cost saving for the group of $172,819. CONCLUSION: On-site preparation is an effective method of preparing cryopreserved cardiac valves and permits significant cost savings.

Cost-Benefit Analysis↗

PubMed1981

[Surgical treatment of multiple heart valve defects].

The article deals with the study of problems of the surgical treatment of patients with multivalvular heart diseases. Problems of myocardial protection, the methods for correcting tricuspid disease, and the attitude towards attendant valvular diseases depending on their severity are discussed on the grounds of the analysis of hospital fatality rate in a group fo 505 patients who underwent one-stage correction of two or three defective heart valves and the appraisal of late results. Analysis of the late results indicates that a more radical approach to the surgical treatment of mitral valvular disease is necessary and that marked relative insufficiency and all forms of organic tricuspid disease must be corrected without fail.

Adolescent↗

PubMed1983

Trial of combined warfarin plus dipyridamole or aspirin therapy in prosthetic heart valve replacement: danger of aspirin compared with dipyridamole.

Despite the use of oral anticoagulation in patients with prosthetic heart valves, persistent thromboembolism over time warrants a search for improved methods of prevention. Thus, patients receiving 1 or more mechanical prosthetic heart valves were randomized to therapy with warfarin plus dipyridamole (400 mg/day) or warfarin plus aspirin (500 mg/day) on the basis of location and type of valve and surgeon, and followed up with a concurrent, nonrandomized control group taking warfarin alone. In 534 patients followed up 1,319 patient-years, excessive bleeding (necessitating blood transfusion or hospitalization) was noted in the warfarin plus aspirin group (23 of 170 [14%], or 6.0/100 patient-years) compared with warfarin plus dipyridamole (7 of 181 [4%], or 1.6/100 patient-years, p less than 0.001), or warfarin alone (9 of 183 [5%], or 1.8/100 patient-years, p less than 0.001). A trend was evident toward a reduction in thromboembolism in the warfarin plus dipyridamole group (2 of 181 [1%], or 0.5/100 patient-years) as compared with warfarin plus aspirin (7 of 170 [4%], or 1.8/100 patient-years), or warfarin alone (6 of 183 [4%], or 1.2/100 patient-years). Adequacy of anticoagulation (based on 12,720 prothrombin time determinations) was similar in all 3 groups with 65% of prothrombin times in the therapeutic range (1.5 less than or equal to prothrombin time/control less than or equal to 2.5), 30% too low, and 5% too high. Warfarin plus aspirin therapy resulted in excessive bleeding and is contraindicated. Longer follow-up study is needed to determine whether further separation of the incidence of thromboembolism can be detected.

Aspirin↗

PubMedDate not supplied

Warfarin, aspirin and microembolic signals in the acute phase of stroke in a patient with mechanical heart valves.

We report the case of a 54-year-old woman, with atrial fibrillation and mechanical heart valves, who suffered a left-hemispheric stroke while she was under warfarin. Daily bilateral simultaneous transcranial Doppler monitoring of the middle cerebral arteries showed the presence of microembolic signals (MES), whose number remained unchanged after adding aspirin 100 mg daily. We conclude that anticoagulant plus antiplatelet therapy does not influence the number of MES in the acute phase of stroke in patients with prosthetic heart valves, suggesting the gaseous origin of MES in these patients.

Anticoagulants↗

PubMed2006

Two stage EDTA anti-calcification method for bioprosthetic heart valve materials.

BACKGROUND: The aim of this study was to investigate the effect of two-stage EDTA treatment in diminishing calcific degeneration in bovine pericardial bioprosthetic heart valve material. MATERIAL/METHODS: Conventionally preserved pericardium specimens were divided into two groups. Group I (controls, n=18) pieces were first fixed in phosphate-buffered solution (PBS)+0.6% glutaraldehyde at +4 degrees C for 24 hours, then stored in PBS+0.2% glutaraldehyde at room temperature for 6 days. Group II (study group, n=18) pieces were treated with PBS containing 100 microg/ml ethylenediaminetetraacetic acid (EDTA) at +4 degrees C for 24 hours, then fixed in PBS+0.6% glutaraldehyde as was group I at +4 degrees C for 24 hours. After a second exposure to PBS containing 100 microg/ml EDTA at room temperature for 24 hours, they were stored in PBS+0.2% glutaraldehyde at room temperature for 4 days. Pericardial patches were inserted into the dorsal pouches of 18 juvenile male Wistar rats. After 7 weeks of implantation, all the pericardium pieces were harvested from sacrificed rats. The calcium content and biomechanical properties of the explanted tissues were evaluated and also examined histopathologically. RESULTS: The difference in the calcium content of the control and study groups was statistically significant. Biomechanical and histopathologic assessment also supported these findings. CONCLUSIONS: Application of two-stage EDTA was found to be useful in the attenuation of calcification in bioprosthetic heart valve materials with mildly increased durability. As calcification was reduced by approximately 50%, it can be considered for use with other agents as an adjuvant treatment.

Animals↗