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At least 271 records · Page 15Linked to original sources
PubMed1994

A squeeze flow phenomenon at the closing of a bileaflet mechanical heart valve prosthesis.

In vivo cavitation in cardiovascular flow fields may occur under very unusual circumstances as a localized transient phenomenon which are confined to very small regions in the vicinity of the valve body or leaflet surface. The violent collapse of cavitation bubbles induces local erosion that may lead to structural damage. The fluid mechanical factors that may cause in vivo cavitation inception in mechanical heart valve (MHV) prostheses are investigated. It is established that the closing velocity of the leaflet holds the key to MHV cavitation. During the final phase of valve closing, the fluid mass in the gap space between the closing occluder and the valve's body is squeezed into motion by the rapidly approaching boundaries. The flow pattern created by this motion (termed 'squeeze flow'), is found to be related to the valve geometry, and the impact velocity of the closing leaflet. Given the closing velocity of the leaflet and the geometry of the MHV, computational flow dynamics (CFD) are made to determine the velocity distributions in the gap flow field of a bileaflet MHV in the mitral position. A two dimensional, time dependent model of the gap space show that flow velocity in the gap space can reach values as high as 30 ms-1 in regions near the edge of the inflow surface of the Edwards Duromedics (ED) MHV leaflet. This high speed stream ejected from the gap channel can create the conditions that characterize cavitation. The location of the isolated high speed region corresponds to the surface erosion that was observed in a number of damaged ED-MHV explants.

Acceleration↗
PubMed2004

A single-center experience of the Sorin Bicarbon heart valve prosthesis: long-term clinical, hematological and hemodynamic results.

BACKGROUND AND AIM OF THE STUDY: The Sorin Bicarbon (SB) bileaflet valve, available since 1990, has a good clinical safety profile. The study aim was to assess the long-term clinical results following implantation, plus hemodynamic and hematological aspects of the valve. METHODS: A total of 195 SB prostheses (100 aortic, 67 mitral, 14 double valve replacements) was implanted in 181 patients (108 males, 73 females) since 1991. RESULTS: Mean age at implantation was 60.5 +/- 10.8 years. Actuarial analysis at 9.0 years showed an overall survival of 63.9 +/- 5.5%; 28.2% of deaths were early (n = 11), and 71.8% late (n = 28). Freedom from thrombosis was 99.4 +/- 0.6% (one early event, successfully reoperated on), and from embolic events was 86.3 +/- 4.7%. Freedom from endocarditis and hemorrhagic complications were respectively 98.1 +/- 1.1% and 98.6 +/- 0.9%. No occurrence of hemolysis was reported. Freedom from non-structural valve dysfunction was 98.7 +/- 0.9%, and from reoperation was 96.1 +/- 1.6%. Hemodynamic evaluation by echocardiography and hematological testing was performed at 7.0 +/- 1.3 years (range 5-9 years) in a subset of 31 patients (20 males, 11 females). Mean valve size was 23.9 mm for aortic mitral. Echocardiography showed that aortic valves had a mean effective orifice area (EOA) of 2.26 +/- 1.28 cm2, with peak and mean pressure gradients of 23.6 +/- 14.6 and 12.9 +/- 8.1 mmHg, respectively. The mean EOA of mitral valve prostheses was 2.67 +/- 0.66 cm2, with peak and mean pressure gradients of 12.2 +/- 4.5 and 3.8 +/- 1.6 mmHg, respectively. Overall mean hemoglobin was 13.4 +/- 1.35 g/dl, and serum lactate dehydrogenase 630 +/- 13 IU/l. Serum haptoglobin was detectable in one patient only, and the mean reticulocyte count was 1.24 +/- 0.51%. CONCLUSION: In the present authors' experience, the Sorin Bicarbon prosthesis has low complication rates and maintains an excellent hemodynamic function over time. Hemolytic potential is insignificant with this valve.

Adolescent↗
PubMed1982

[M-mode and two-dimensional echocardiography of heart valve prosthesis dysfunction].

The diagnostic efficacy of M-Mode and 2-d echocardiography for the detection of malfunctioning prosthetic valves was studied in twenty-nine patients with prosthetic valves and clinical deterioration. Echocaradiographic abnormalities were found in 8 of 12 patients with confirmed valve dysfunction; 30.8% of the cases had false negative echo tracings. In 17 patients with normal echocardiographic pictures of the valves another cause of clinical deterioration was found (congestive heart failure, pericardial effusion, aneurysm of aortic root). In this study M-Mode and 2-d echocardiography had an excellent diagnostic accuracy rate in distinguishing congestive heart failure from valve dysfunction. Comparing the data of M-Mode and 2-d registration, both methods are found to be complementary. A major advantage of the 2-d echocardiography is its enhanced spatial orientation, whereas M-Mode echocardiography enables better evaluation of valve movements and corresponding time intervals and recognition of quick movements and fibrillations.

Aortic Valve↗
PubMedDate not supplied

[Hemolytic anemia in patients with heart valve prosthesis].

This article analyzes the historic evolution of the Starr-Edwards prosthesis manufacture and its association to hemolysis. It describes also the information related to bioprosthesis and hemolysis. The mechanisms involved in mechanical hemolysis are discussed (turbulent flux, red cells trapping, construction material and autoimmunity). Reviews the pathophysiology and criteria for clinical and laboratory diagnosis of hemolysis. We describe the value of the quantitation of unconjugated bilirubin, free plasmatic hemoglobin, DHL and it's DHL1 iso enzyme, methemalbumin and urinary hemosiderin for the specific diagnosis of this entity. Finally we comment on the utility of bed rest, cellular maturity inductors, propranolol and sulfinpyrazone therapy for the control of the hemolytic process.

Anemia, Hemolytic↗
PubMed1994

[Reoperation for heart valve prosthesis. Apropos of 99 cases].

From March 1977 to November 1988, 99 patients were reoperated on after a first valvular replacement. Mean delay between the two operations was 53 months (10 days to 18 years). The patients were reoperated on mainly for mechanical disinsertion (30), bacterial endocarditis (25) and thrombosis (18 patients). Operative mortality was 11%, mainly following reoperation for bacterial endocarditis. Mean follow-up (85 patients) was 49 months (6 months-11 years). 75% were alive and doing well 4 years after reoperation and 66% at 6 years. Eight patients needed a third operation with two deaths.

Adolescent↗
PubMed1993

[Reoperations on heart valve prosthesis. Apropos of 99 cases].

From March 1977 to November 1988, 99 patients were reoperated on after a first valvular replacement. Mean delay between the two operations was 53 months (10 days to 18 years). The patients were reoperated on mainly for mechanical disinsertion (30), bacterial endocarditis (25) and thrombosis (18 patients). Operative mortality was 11%, mainly following reoperation for bacterial endocarditis. Mean follow-up (85 patients) was 49 months (6 months-11 years). 75% were alive and doing well 4 years after reoperation and 66% at 6 years. Eight patients needed a third operation with two deaths.

Actuarial Analysis↗
PubMed1985

[Quality of life following heart valve prosthesis].

The subjective and objective health status of 69 patients with a mean age of 58 +/- 9 years was evaluated 2-4 years after replacement of the aortic or mitral valve. All findings were compared to the preoperative status. Subjectively, 80% of all patients felt a considerable improvement following surgery and the mean NYHA functional class dropped postoperatively from 2.68 +/- 0.63 to 1.32 +/- 0.53 (p less than 0.001). 66% of all patients felt better mentally as well. However, 64% of all patients indicated that their intellectual capacity had decreased postoperatively. Objectively the signs of congestive heart failure had decreased significantly (edema -50%, rales -83%, neck vein distention -87%). Cardiomegaly and redistribution had improved in 77% and 80% of all patients, and left ventricular hypertrophy on ECG had disappeared in 46% of all cases. Despite this important subjective and objective improvement, there was little change in the degree of postoperative employment. Thus, valve surgery leads to a dramatic subjective and objective improvement of cardiac performance and quality of life. However, the improvement has little influence on postoperative resumption of work. Results of this study also suggest that cardiac surgery has a negative effect on intellectual capacity.

Adult↗
PubMed1994

Home heparin therapy used in a pregnant patient with a mechanical heart valve prosthesis.

The optimal anticoagulation therapy for pregnant patients with a mechanical valve prosthesis is uncertain, but teratogenic effects and the high incidence of fetal loss associated with dicumarol derivatives limit the use of these agents as anticoagulants in this setting. A patient with a mechanical valve prosthesis, in the first trimester of pregnancy, stopped taking her warfarin because of personal fears about teratogenicity. Prosthetic valve thrombosis developed, and she required redo mitral valve replacement. Another mechanical prosthesis was inserted without maternal or fetal injury. The patient was maintained on continuous home, intravenous, high-dose heparin therapy for the remainder of her pregnancy. This therapy resulted in a successful pregnancy and delivery without valve thrombosis, hemorrhagic events, or maternal or fetal compromise.

Adult↗
PubMed1990

[Surgical treatment of endocarditis following heart valve prosthesis].

Experience of many years in surgical treatment of prosthetic valve endocarditis (RVE) is analyzed. Patients whose condition was serious were operated on for a second time: 91.6% had preoperative functional class IV, in half of them circulatory disorders were of stage IIB--III; 62.4% were subjected to reoperation for emergency indications. Twenty-five reoperations were performed for early PVE with 52% hospital mortality, 23 reoperations-for late term PVE with mortality of 30.4%. The most frequent cause of PVE was staphylococcal infection which showed a tendency to increase in the recent years. In early PVE the severity of the condition in the recent years. In early PVE the severity of the condition was due to sepsis and intoxication, in late-term PVE it was caused by disorders of hemodynamics which were usually induced by dysfunction of the prosthesis. The results of surgical management of PVE depended on the severity of the patient's condition before the operation, timely performance of the operation, and the efficacy of antibacterial therapy.

Adolescent↗
PubMed1977

[Heart valve prosthesis in children and adolescents with aortic valve insufficiency].

Aortic valve prosthetic replacement in children and adolescents helps to improve their haemodynamics, and favourably affects the course of the rheumatic process. The correction of the defect is indicated in the presence of appropriate subjective and objective symptoms of aortic valve insufficiency. The lumen of the aorta was so large in many children that it permitted the employment of prostheses for adults. Calcification of the aortic valve was found in 9 of the 31 patients, which contradicts the commonly accepted belief of a low incidence of calcification in this disease in children. Hospital mortality and postoperative complications rate did not exceed those in aortic valve replacement in adults. The comparatively fast reduction of the heart size and the positive dynamics of the functional parameters in children and adolescents may be due to the high plasticity of the cardiovascular system in this age-group.

Adolescent↗
PubMed1998

[Chronicle of a defective heart valve prosthesis].

The Björk-Shiley convexo-concave (BScc) strut fracture problem is about to enter its third decade. At present, valve carriers still face the risk of outlet strut fracture; a risk which does not seem to decline. The temporising attitude of the manufacturer has led to far more victims than would have been necessary but also the Food and Drug Administration, regulatory agencies outside the US and the medical community share responsibility for this problem.

Confidentiality↗