In vitro evaluation of the long-body On-X bileaflet heart valve

AIM: To determine the staining pattern of vascular endothelial growth factor (VEGF) at different stages of diabetic retinopathy (including post-laser photocoagulation) and to compare staining in excised fibrovascular and fibrocellular (non-diabetic) preretinal membranes. METHODS: Immunohistochemical localisation of VEGF, using antibodies raised against VEGF165 and VEGF121,165,189, was carried out on specimens of normal human retina (n = 15), diabetic retinas ((a) with no overt retinopathy (n = 19), (b) with intraretinal vascular abnormalities but no proliferative retinopathy (n = 6), (c) with active proliferative retinopathy (n = 6), (d) with no residual proliferative retinopathy after photocoagulation therapy (n = 15)), excised diabetic fibrovascular membranes (n = 19), and non-diabetic fibrocellular membranes (n = 7). The degree and pattern of immunostaining was recorded. RESULTS: In general, VEGF was absent from the majority of normal retinas. VEGF staining was apparent in most diabetic tissues but the staining pattern was dependent on both the specificity of the antibody used and the category of tissue. Staining with the VEGF165 antibody was generally confined to endothelial cells adn perivascular regions while the VEGF121,165,189 antibody was also associated with extravascular components of the inner retina. Intensity of immunostaining of diabetic eyes was dependent on the severity of retinopathy being least in diabetics with no overt retinopathy and greatest in retinas with proliferative retinopathy. Interestingly, the intensity of immunostaining in diabetic retinas which had undergone laser surgery for proliferative retinopathy was reduced to basal levels. Moderate to intense immunostaining was observed in all fibrovascular and fibrocellular membranes examined. CONCLUSIONS: This study supports a circumstantial role for VEGF in the pathogenesis of both the preclinical and proliferative stages of diabetic retinopathy.     

Time-frequency analysis of transient pressure signals for a mechanical heart valve cavitation study

A series of transient pressure signals (TPSs) can be measured using a miniature pressure transducer mounted near the tip of the inflow side of a mechanical heart valve (MHV) occluder during closure. A relationship appears to exist between the intensity and pattern of the TPS and the cavitation potential of a MHV. To study the relationship between MHV cavitation and the TPSs, we installed an MHV in a valve testing chamber of a digitally controlled burst test loop. A charge coupled device (CCD) camera and a personal computer based image grabbing program was used to visualize cavitation bubbles appearing on or near the occluder surface. One bileaflet MHV was used as the model for this study. Cavitation bubbles were observed within 300 microsec of the leaflet/housing impact. The valve was tested at various driving pressures between 100 and 1,300 mmHg. MHV cavitation bubble intensities were qualitatively classified into three categories: 1) strong, 2) weak, and 3) none. Digital images of the MHV occluder inflow surface were recorded simultaneously with the TPSs. TPSs were studied by the time-frequency analysis method (spectrogram) and correlated to MHV cavitation potential. The intensity of the cavitation bubbles was found to be associated with burst test loop driving pressures during leaflet closure.     

Effects of dobutamine on aortic valve indexes in asymptomatic patients with bileaflet mechanical prostheses in the aortic valve position

We investigated the effects of alternating transvalvular flow rate on Doppler-derived aortic valve resistance and valve area in asymptomatic patients with mechanical aortic valve replacement under dobutamine infusion. The Gorlin-derived aortic valve area and continuity equation-derived aortic valve area seem to be less flow dependent; valve resistance tends to be flow dependent.     

Normal echocardiographic characteristics of the Sorin Bicarbon bileaflet prosthetic heart valve in the mitral and aortic positions

Doppler echocardiographic characteristics of normally functioning Sorin Bicarbon prostheses were prospectively assessed in 226 consecutive patients (135 male and 91 female patients, mean age 61 +/- 10 years) with 233 valves in the mitral (n = 67) and aortic (n = 166) positions whose function was considered normal by clinical and echocardiographic evaluation. Patterns of "normal" transprosthetic leakage were assessed with transthoracic echocardiography in all valves and with transesophageal echocardiography in six selected mitral valve prostheses. For the mitral valve prostheses, we found that peak and mean gradient, as well as pressure half-time, were not significantly different in either the 25 or the 31 mm valves (median values from 15 to 10 mm Hg, from 4 to 4 mm Hg, and from 70 to 83 ms; p = Not significant for all). On transthoracic study, 12 patients (17%) with a Sorin Bicarbon valve in the mitral position showed minimal transprosthetic leakage. On transesophageal study, all patients showed a transprosthetic leakage whose spatial distribution had a complex pattern: in planes orthogonal to the leaflet axis, two to four jets arising from the hinge points and converging toward the center of the valve plane could be visualized; in planes parallel to the leaflet axis, there were three jets, the two lateral ones diverging and the central one perpendicular to the valve plane. For the aortic valve prostheses, there was a significant decrease in transprosthetic gradients and an increase in effective orifice areas as prosthesis size increased. Peak and mean gradients decreased from a median value of 25 and 13 mm Hg in the 19 mm valves to 9 and 5 mm Hg in the 29 mm valves, respectively. Effective prosthetic valve area calculated with the continuity equation increased from a median value of 0.97 cm2 for the 19 mm size valves to 3.45 cm2 for the 29 mm size. With analysis of variance, effective prosthetic aortic valve area differentiated various valve sizes (F = 40.9, p < 0.0001) better than peak (F = 10.3, p < 0.0001) or mean (F = 8.04, p < 0.0001) gradients alone did. Furthermore, effective prosthetic aortic valve area correlated better than peak and mean gradients with prosthetic size (r = 0.76, r = -0.45, and r = -0.39, respectively). On transthoracic study, 109 patients (66%) showed minimal transprosthetic leakage. These normal values, obtained in a large number of patients with normofunctioning mitral and aortic Sorin Bicarbon valves, may help to identify Sorin Bicarbon prosthesis dysfunction.     

Long-term results of heart valve replacement with the Edwards Duromedics bileaflet prosthesis: a prospective ten-year clinical follow-up

OBJECTIVE: The Edwards Duromedics valve (Baxter Healthcare Corp., Edwards Division, Santa Ana, Calif.) was designed with a self-irrigating hinge mechanism to reduce thromboembolic complications. After good initial clinical results, distribution was suspended in 1988 after reports of valve fracture after 20,000 valves had been implanted. The manufacturer conducted extensive studies to improve the Edwards Duromedics and reintroduced a modified version, which is available as Edwards Tekna. The purpose of the study was the evaluation of long-term results of the original Edwards Duromedics that might be important for the current version, the Edwards Tekna valve. METHODS: A prospective clinical 10-year follow-up was performed of 508 patients who underwent valve replacement with the Edwards Duromedics valve in the aortic (n = 268), mitral (n = 183), and aortic and mitral (n = 56) position. RESULTS: The perioperative mortality rate was 6.9%; follow-up was 98% complete, comprising 3648 patient-years for a mean follow-up of 86 months (range: 33 to 144 months). The actuarial freedom from complications at the 10-year follow-up and the incidence rate (percent per patient-year) were as follows: late mortality rate, 69.2% +/- 2.4% (3.5% per patient-year); thromboembolism, 90.7% +/- 1.6% (0.96% per patient-year); anticoagulation-related hemorrhage, 87.7% +/- 1.7% (1.34% per patient-year); prosthetic valve endocarditis, 96.7% +/- 0.09% (0.38% per patient-year); valve-related mortality rate, 89.3% +/- 1.6% (1.21% per patient-year); valve failure, 86.2% +/- 1.85% (1.54% per patient-year); and valve-related morbidity and mortality rate, 71.1% +/- 2.3% (3.2% per patient-year). Three leaflet escapes were observed (one lethal, two successful reoperations; 99.1% +/- 0.05% freedom, 0.08% per patient-year). All patients functionally improved (86% in New York Heart Association classes I and II), and incidence of anemia was insignificant. CONCLUSIONS: These results confirm that the Edwards Duromedics valve shows excellent performance concerning thromboembolism, hemolysis, and functional improvement and will serve as a reference for the last version, the Edwards Tekna valve, where comparable long-term data are currently not available.     

A mechanical heart valve prosthesis with a spherical shape and open center

A mechanical valve prosthesis is described with central blood flow. The generations I and II of the mechanical valve obstruct the blood flow and cause turbulence with undesirable consequences. The opening in the centre of Simkovic-Bolf valve preserves the laminar blood flow, reduces the trauma of blood and myocardium stress. Our new valve represents a mechanical valve prosthesis of generation III. (Fig. 5, Ref. 16.).     

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.     

Thrombosis of mechanical heart valve prosthesis. Predisposing factors and results of surgical treatment

There is both epidemiologic and experimental support for the hypothesis that a high-fiber diet can reduce breast cancer risk; this may be due, at least in part, to a reduction in circulating estrogens. This study examined the effects of three levels of wheat bran supplementation (5, 10, and 20 g/d for 2 mo) on the major serum estrogens during both the luteal and follicular phases of the menstrual cycle. The 10- and 20-g supplements, which increased the total dietary fiber intakes to approximately 20 and 32 g/d, respectively, resulted in significant decreases in the luteal serum estrone (P < 0.05 and < 0.02, respectively). The serum estradiol was significantly reduced in the 10-g wheat bran group after 2 mo (P < 0.05); the 20-g supplemented group showed a significant decrease in estradiol at 1 mo (P < 0.02), but not at 2 mo. No changes occurred in the estrone sulfate concentrations. During the follicular phase, the 10-g wheat bran group exhibited a significant reduction in the serum estrone (P < 0.02). Only the serum estrone sulfate showed any reduction with the 20-g supplement, and this just failed to achieve significance (P = 0.07). Serum sex hormone-binding globulin levels were unaffected by wheat bran. When of long duration, these effects may be sufficient to favorably influence breast cancer risk in Western women.     

Long-term follow-up of open commissurotomy versus bileaflet valve replacement for rheumatic mitral stenosis

OBJECTIVE: Despite the achievements of third generation mechanical cardiac valve prostheses, conservative procedures are still considered the best surgical option for rheumatic mitral valve stenosis. To compare long-term results of open mitral commissurotomy (Group A) and mitral valve replacement with bileaflet prostheses (Group B) a 15-year follow-up study was carried out. METHODS: From January 1981 to May 1996, 540 consecutive patients with pure isolated rheumatic mitral stenosis underwent mitral valve surgery: 300 had mitral commissurotomy and 240 valve replacement. The follow-up was 99.05% complete and ranged between 1 and 185 months in Group A and from 1 to 171 months in Group B. RESULTS: Hospital mortality was 2% in Group A and 2.08% in Group B. Late mortality was 1% in Group A and 3% in Group B. The 10-year survival rates were 98.7% +/- 1% in Group A and 93.7% +/- 3% in Group B. There was a statistically significant difference of freedom from reoperation in Group B (97.7% +/- 1%) versus Group A (88.1% +/- 2%) (P = 0.04). In group A 14 embolic events occurred (93.7% +/- 2%), and 15 (6.52%) in Group B (83.9% +/- 7%). Haemorrhagic events were observed in 2 patients (0.68%) of Group A (99.3% +/- 0.5%) and in 3 patients (1.3%) of Group B (98.4% +/- 1%). CONCLUSIONS: Long term results of mitral commissurotomy were more satisfactory than those obtained with bileaflet valves. Reoperation rate was higher in mitral commissurotomy.     

Effect of valve holder flexibility on cavitation initiation with mechanical heart valve prostheses: an in vitro study

The records of 98 patients with 160 hypoplastic thumbs seen between 1923 and 1993 were reviewed to determine the salient characteristics of this population. Physical findings, photographs, and x-ray films were studied. Sixty-three percent of patients were male, and 63% had bilateral thumb hypoplasia, 59% had radial dysplasia, and 86% had other anomalies. An associated syndrome, most commonly the vertebral, anal, tracheosophageal, renal, and radial limb anomalies association or Holt-Oram syndrome, was present in 44%. Patients with spine, genitourinary, or gastrointestinal anomalies were most likely to have the vertebral, anal, tracheosophageal, renal, and radial limb anomalies association, those with cardiac anomalies were most likely to have Holt-Oram syndrome, and those with lower extremity anomalies were most likely to have a different syndrome. One hundred thirty-nine thumbs were classifiable, using a modification of Blauth's classification; 19% were types 1 and 2, 23% were type 3, and 58% were types 4 and 5. One hundred seven operations were performed on 63 upper limbs, including 24 thumb reconstructions and 35 pollicizations. These patients must be carefully examined for bilaterality, other anomalies, and syndromes. Classification using a modification of Blauth's criteria is useful and helps the surgeon determine a treatment plan.     

Panel summary: spontaneous echo contrast in patients with mechanical heart valve implants

Three study sites along the roads with different automobile traffic densities were selected and cattle milk samples were collected every month from all the three sites. Lead concentration in samples were determined through atomic absorption spectrometer. Milk collected from area of heavy traffic contained 4.6-7.2 ppm of Pb, which is much higher than its permissible limit (0.3 ppm) according to FDA.     

Chronic evaluation of orthotopically implanted bileaflet mechanical aortic valves in adult domestic sheep

Papillary carcinoma is the most common form of thyroid carcinoma and, generally, it has a more favorable prognosis than other carcinoma types, although diverse variants or subtypes have been described, some of which appear to have a less favorable prognosis. Recently, a new variant, the so-called "Warthin-like tumor" or "tall-cell variant with extensive lymphocytic infiltration of papillary thyroid carcinoma" with behavior similar to the usual papillary carcinoma, has been described. We present a case with the cytohistological pattern of "Warthin-like tumor" of the thyroid. Immunohistochemistry revealed reactivity at the epithelium lining papillae for antimitochondrial 113-I antibody and also membranous positivity for CD15 (Leu M1). Lymphoid stroma showed an immunoprofile similar to chronic lymphocytic thyroiditis. These findings point to the consideration of "Warthin-like tumor" as being a hybrid neoplasm between the tall-cell variant and oxyphilic papillary carcinoma associated to a lymphoid-rich stroma.     

The hemodynamic effects of mechanical prosthetic valve type and orientation on fluid mechanical energy loss and pressure drop in in vitro models of ventricular hypertrophy

A bolus injection of theophylline produced a significant increase in peripheral blood flow in anesthetized rat ear, monitored by laser-Doppler flowmetry, with increases in arterial blood pressure and heart rate. These effects were attenuated by previous treatment with reserpine, but reserpine had no effect on the blood flow increase produced by acetylcholine. A dose of propranolol, which caused attenuation of the theophylline-induced increase in heart rate, did not change the peripheral blood flow. The higher dose of propranolol, which nearly canceled the increases in blood pressure and heart rate, caused attenuation of the blood flow increase but did not cancel it. However, the theophylline-induced flow increase was completely reversed by a nitric oxide synthase inhibitor, NG-nitro-L-arginine methyl ester, which alone had no effect, without any change in arterial blood pressure and heart rate. Treatment of the rats with the dose of inhibitor slightly and significantly reduced the response of peripheral blood flow to acetylcholine. The other isomer, NG-nitro-D-arginine methyl ester, and the other inhibitor, NG-monomethyl-L-arginine, did not have such an effect. These results suggest that the flow increase is due to an independent effect on the heart with modification by autonomic reflexes and involves the adrenergic and nitrergic pathways.     

Choosing a prosthetic heart valve

Although most of the available prosthetic heart valves function remarkably well, the variety of available choices attests to the inability of any single one to fulfill the requirements of the ideal valve substitute. The mechanical prostheses include the caged-ball, tilting-disc, and bileaflet valves. Tissue valves available in the United States are the Carpentier-Edwards and Hancock porcine heterograft valves and the Carpentier-Edwards pericardial valve. Review of several large comparative studies on valve performance reveals that the overall results with tissue and mechanical valves are about equal at the end of 10 years. The characteristics of each type of valve substitute dictate the selection of one prosthesis in preference to others for a particular patient. Mechanical prostheses are recommended for patients without contraindications for anticoagulants. Tissue valves are reserved for patients over 65 years of age or for patients in whom anticoagulation is contraindicated. Multiple other patient-related factors need to be considered in selecting the appropriate valve, including the psychosocial situation and patient preference.     

Hemodynamic structure of antiorthostatic reactions: relationship of mechanical activity of the heart and arterial pressure

This paper is an update on the issue of dental student debt and provides additional data and an exploration of continued trends which were outlined by Douglass and Fein in the 1995 IOM study of The Future of Dental Education. Dental school tuitions have continued to increase at rates at or above the consumer price index. These tuition bills are increasingly being met by debt financing on the part of the students. These trends are described and then related to recent data on the future plans of dental school seniors. The second part of the paper will provide new updated date on dentists' incomes and analyze the trend in dental fees versus the consumer price index. The final section provides a summary of pay back mechanisms currently being offered to students.     

Allograft heart valve viability and valve-processing variables

BACKGROUND: The impact of allograft valve viability on valve durability remains controversial. Analyses of our clinical results have demonstrated the superiority of the cryopreserved valve viable at the time of implantation over the 4 degrees C stored valve nonviable at the time of implantation. In this study, we quantitatively assessed the effects on viability of current and past valve-processing protocols at The Prince Charles Hospital. METHODS: The viability of pulmonary valves was quantitatively analyzed by thin-layer autoradiography to assess the effects of donor type, antibiotics, and valve storage. RESULTS: Control valve segments obtained from beating-heart donor valves had a higher initial viability (0.92+/-0.02) than nonbeating-heart donor valves (0.66+/-0.03). Cryopreservation after low-dose antibiotic sterilization significantly reduced viability to 50% to 60% of the control, and in the presence of amphotericin B, viability dropped further to 10% to 36% of the control. After 7 days' storage at 4 degrees C, viability was reduced to 2% of control and to 0% viability after 21 days. CONCLUSIONS: For maximal preimplantation viability, valves should be procured as soon as possible after cessation of heart beat and should be cryopreserved if they are not to be clinically implanted within 1 to 2 days. Amphotericin B should not be used in conjunction with cryopreservation if viability is to be maximized.     

Hemodynamic performance of four mechanical bileaflet prosthetic valves in the mitral position: an echocardiographic study

Plasma methadone concentrations and its main metabolite D,L-2-ethylidiene-1,5-dimethyl-3,5-diphenylpyrrolidine (EDDP) were determined in 93 patients under methadone maintenance treatment to assess their relationship with heroin use and opioid withdrawal symptoms. Neither plasma concentrations of methadone nor EDDP were significantly different when patients that used heroin in last 3 months were compared with those testing negative for this drug (methadone, 355 +/- 217 versus 369 +/- 216 ng/ml, t = 0.29, P = NS; EDDP, 49 +/- 28 versus 54 +/- 40 ng/ml, t = 0.51, P = NS). No correlation between opioid withdrawal scale scores and plasma concentrations of methadone (r = 0.02, P = NS) and EDDP (r = -0.14, P = NS) was found. Therapeutic drug monitoring during methadone maintenance seems to be useful for assessing compliance with treatment but not for predicting heroin use and subjective withdrawal symptoms.     

Anticoagulation in children with mechanical valve prostheses

BACKGROUND: Clotting complications in patients with mechanical valve prostheses can be prevented with either warfarin sodium (Coumadin; DuPont, Wilmington, DE) or antiplatelet agents. In children, it is not known whether one treatment regimen is more effective or safe than the other. METHODS: We prospectively followed up 64 children and young adults (aged 18 years or younger at implantation) with a mechanical valve on the left side of the heart, from October 1986 through October 1996. Forty-eight patients were treated with Coumadin and 16 with aspirin and dipyridamole. The two groups were similar in age, sex, valve location and size, mean length of follow-up, and operative indication. There has been a total follow-up of 272 patient-years on Coumadin and 116 patient-years on aspirin and dipyridamole. RESULTS: There was no difference between the two groups in survival or freedom from thromboembolism. Bleeding occurred more often in the patients taking Coumadin, but this difference was not statistically significant. Analysis of the literature showed thromboembolism and bleeding rates to be similar in the patients receiving Coumadin and those receiving antiplatelet agents. CONCLUSIONS: Coumadin and the combination of aspirin plus dipyridamole provided similar protection against complications in this group of children and young adults with left-sided St. Jude (St. Paul, MN) mechanical valves. The choice between the two regimens may depend on other factors, such as patient preference and convenience.     

Blood rheology in patients with native heart valve disease and after valve replacement

Patients with heart valve disease have rheologic abnormalities that are more pronounced in double valve disease than in mitral or aortic valve disease; after valve replacement surgery, the degree of rheologic abnormality is more pronounced in patients with mechanical and biological prostheses than in those with homografts and pulmonary autografts. Rheologic abnormalities seen in these patients might be related to the different incidences of thromboembolism in the presence of various valve defects and various types of prostheses.