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At least 343 records · Page 19Linked to original sources
PubMed2006

Allograft semilunar cardiac valves processing and cryopreservation - morphology in scanning electron microscope.

OBJECTIVE: The most important factors of long term clinical performance of biological heart valve prostheses are methods of processing and cryopreservation. That is why we decided to evaluate the impact of current Allograft Heart Valves (AHV) Bank protocol on valve tissue morphology. Scanning electron microscope (SEM) is a valuable tool for investigation of biological surfaces. In case of cardiac valves it is especially suitable for detection of fine changes in endothelial covering and underlying layers. MATERIAL AND METHODS: "Fresh" aortic and pulmonary AHV samples, harvested from "heart-beating" cadaveric donors, were compared with (1) tissue from AHV obtained from non heart-beating donors, (2) samples stored in 4 degrees C saline for 24 h, (3) antibiotic treated tissue for 24 h at 37 degrees C and finally (4) cryopreserved valves, stored in liquid nitrogen (-196 degrees C) for 6-38 months. All samples were dissected, dried with hexamethyldisilazane (HMDS), gold coated, studied and photographed by SEM (Tesla BS 301). RESULTS: Our alternative method of drying samples by the HMDS method proved to be suitable for thin membranes of human semilunar valves. We were able to detect early changes in the endothelium after harvesting, and denudation of the endothelial covering during preservation with and without freezing. CONCLUSION: SEM (using HMDS drying) along with other methods may be helpful for the morphological control of processing, cryopreservation and liquid nitrogen storage of AHV. According to the current findings we have to avoid washing of AHV in saline after harvesting.

Cryopreservation↗
PubMed1976

Establishment of a viable homograft cardiac valve bank: a rapid method of determining homograft viability.

A method for determining the viability of homograft valves has been developed based on sequential measurements of glucose and pH levels of the culture medium in which cardiac valves have been maintained for short periods at 37 degrees C. Viable valves, as determined by tissue culture, showed a characteristic pattern of glucose utilization and pH reduction that was absent in nonviable valves. Upon explantation of valve leaflet fragments into tissue culture, only fragments from valves that metabolized glucose produced viable fibroblast cultures. The method reported here is rapid, requires no specialized equipment, is nondestructive, and can directly determine the viability of the valve homograft within 24 to 48 hours.

Aortic Valve↗
PubMed1984

Amyloid deposits in bioprosthetic cardiac valves after long-term implantation in man. A new localization of amyloidosis.

Congo red staining with microscopic examination under polarized light was performed in 30 porcine bioprosthetic cardiac valves and one autologous fascia lata valve explanted from 31 patients in order to detect the presence of amyloid. Microdeposits of amyloid were present in the sewing ring of the fascia lata valve and in 10 porcine bioprostheses, and this finding was confirmed by transmission electron microscopy in 3 porcine bioprostheses. All amyloid-laden porcine valves had been implanted for at least 33 months before removal, and all except two showed dysfunction and/or severe degeneration of cuspal tissue. Statistical analyses failed to establish any correlation between the presence of amyloid and patient-related factors. In a majority of porcine bioprostheses amyloid was permanganate-sensitive and tryptophan-positive. The pathogenesis of this new form of heart valve amyloidosis might consist in penetration of human macrophages in deteriorated bioprosthetic cusps and their interaction with blood-borne amyloid precursors.

Adolescent↗
PubMed1977

[Replacement of cardiac valves with Björk-Shiley and Cooley-Cutter prostheses: a comparative study (author's transl)].

Björk-Shiley and Cooley-Cutter prostheses are the most satisfactory cardiac valves in our experience. They were compared in regard to incidence of emboli and mortality by long-term follow up. Among the 1904 patients who had received a Bjök-Shiley valve between 1969 and 1975 late follow-up could be obtained in 1565 patients. Among the 1329 patients with a Cooley-Cutter valve implanted between 1971 and 1975, late follow-up was obtained in 779. In the mitral valve replacement series, Cooley-Cutter / Björk-Shiley early mortality was 9.9/12.8 (%), late mortality 6.8/12.8 (%), early emboli 5.4/8.1 (%), late emboli 3.7/5.1 (%). In the aortic valve replacement series, Cooley-Cutter/Björk Shiley early mortality was 6.6/8.4 (%), late mortality 2.9/5.1 (%), early emboli 2.7/3.3 (%), late emboli 1.1/2.7 (%). Both early and late mortality and emboli were more favorable in the Cooley-Cutter sample as compared to the Björk-Shiley group. Therefore the Cooley-Cutter prostheses are preferred in both the aortic and mitral positions.

Aortic Valve↗
PubMed2000

Induction of cytotoxic T lymphocytes with destructive potential after cardiac valve homograft implantation.

BACKGROUND AND AIM OF THE STUDY: Clinical and experimental studies have shown that a specific immunological response may play a role in the degeneration of human cardiac valve homografts. In heart and corneal transplantation, cytotoxic T lymphocytes (CTL) with high avidity for donor antigens are presumed to be the major effector cells causing graft destruction. We studied the kinetics of these donor-specific CTL precursors (CTLp) and their high-avidity fraction in peripheral blood of patients receiving a cryopreserved valve homograft. METHODS: Limiting dilution analysis (LDA) was used to enumerate donor-specific CTLp in peripheral blood samples of 15 patients, obtained up to 12 months after valve implantation. Donor-specificity was proven by using donor-HLA mismatched third-party stimulation cells as controls. CD8 monoclonal antibodies were used to distinguish high- and low-avidity CTLp. RESULTS: A significant increase in total donor-specific CTLp among the peripheral blood mononuclear cell population occurred in 14/15 patients (93%) at 3-6 months (p = 0.045) after implantation and remained so for up to 12 months (p = 0.015). In addition, a significant increase was seen in the fraction of circulating CTLp with high avidity for donor antigens (p<0.026) within the first 3 months after implantation. CONCLUSION: Implantation of cryopreserved valve homografts increases the number of donor-specific CTLp and their high-avidity fraction, in the peripheral blood. These cells have the capacity to destroy organ and tissue grafts.

Adolescent↗
PubMed2002

Cardiac valve reoperations: analysis of operative risk factors in 154 patients.

BACKGROUND AND AIMS OF THE STUDY: The study aim was to evaluate the operative risks of reoperation on heart valve prostheses. METHODS: Between January 1985 and December 2000, 154 patients (79 males, 75 females, mean age 61.2+/-9.5 years) underwent cardiac valve reoperation for which indications were prosthetic failure (n = 133; prosthetic mitro-aortic dysfunction occurred in 16 cases), native valve disease in patients with a previous prosthetic valve implantation (n = 12), and both situations concomitantly (n = 9). Total valve replacements numbered 161 (64 in the aortic position, 96 in the mitral position, and one in the tricuspid position). There were 18 valve repairs (eight in the mitral position, 10 in the aortic position). One patient underwent prosthesis thrombectomy (mechanical valve). RESULTS: Overall operative mortality was 8.4% (n = 13); emergency operation (p <0.002), advanced NYHA class (p <0.026), indication for reoperation (p <0.026), gender (p <0.016) and number of previous reoperations (p = 0.05) were independent determinants for reoperation. Non-significant determinants were age and position of replacement. CONCLUSION: Correct planning of reoperation timing reduces operative risks due to NYHA class (3.8% mortality rate for class II-III versus 21.7% for class IV), and to urgent-emergency procedures (35.7% mortality versus 6.5% for elective operations). The high operative risk of prosthesis thrombosis is a deterrent to implanting mechanical prostheses in patients with disorders of hemostasis.

Adult↗
PubMed1997

Passive retrograde cerebral perfusion during routine cardiac valve surgery reverses middle cerebral artery blood flow and reduces the risk of stroke.

BACKGROUND AND AIMS OF THE STUDY: Cerebral complications constitute a major source of morbidity and disability after cardiac valve surgery. These may be the result of macroembolization (air/debris) or inadequate perfusion pressure. In an attempt to reduce the incidence of cerebral vascular accident (CVA)/transient ischemic attack (TIA), we have routinely performed three minutes of passive retrograde cerebral perfusion (PRCP) on all valve cases. Here, we retrospectively determined our perioperative (0-30 day) incidence of CVA/TIA. METHODS: In all cases, the extracorporeal circuit consisted of an ascending aortic cannula and either one two-stage or two single-stage venous cannulae. Three minutes of PRCP was instituted in all cases upon discontinuation of anterograde cardiopulmonary bypass (CPB) via a shunt distal to the heart/lung machine between the arterial and venous cannulae. Mean systemic blood pressure was maintained at 60 mmHg with Neo-Synephrine. Central venous pressure never exceeded 25 mmHg. In 10 cases, transcranial Doppler ultrasonography (TCD) was used to assess middle cerebral artery (MCA) blood flow. In total, 209 consecutive valve procedures with PRCP (group A) were compared with 164 consecutive valve procedures with no PRCP (group B). All data were compared using Fisher's exact probability test. The incidence of CVA/TIA was also compared with published retrospective and prospective data. RESULTS: TCD demonstrated blood flow reversal in the MCA after a minimum of 30 s. The incidence of CVA/TIA was 0% (0/209) in group A, and 2.4% (4/165) in group B (p = 0.0386). The incidence of CVA/TIA in published retrospective data is 0.7-3.8% and 4.8-5.2% in prospective data. CONCLUSIONS: We have demonstrated in 209 consecutive valve cases that, upon discontinuation of CPB, routine three-minute PRCP not only reversed MCA blood flow, but also reduced the incidence of neurologic events.

Cerebrovascular Circulation↗
PubMed1998

Immunogenic human leukocyte antigen class II antigens on human cardiac valves induce specific alloantibodies.

BACKGROUND: The kinetics of panel reactive antibodies (PRA) and incidence of antibodies directed against human leukocyte antigen (HLA) class II were studied in patients who received a cryopreserved cardiac valve allograft. METHODS: A complement-dependent microlymphocytotoxicity test was used to determine the percentage of panel reactive antibodies. Anti-HLA class II antibodies were measured by two-color fluorescence assays. RESULTS: The panel reactive antibodies became positive in 25 (78%) of 32 recipients between 1 and 16 months after implantation. Antibodies against HLA class II antigens were detected in 11 (37%) of 30 patients. In 9 (82%) of 11 cases these antibodies were donor specific. The induction of antibodies against donor HLA class II antigens suggests that intact HLA class II antigens are expressed by viable cells within the graft. Dithiothreitol analysis showed that the antibodies were of the immunoglobulin G type. Apparently, the HLA class II antigens are expressed in an immunogenic way, as activation of specific T-helper cells is essential for the switch from immunoglobulin M to immunoglobulin G antibodies. CONCLUSIONS: Allogeneic valve transplantation is associated with the production of donor-specific anti-HLA class I and II antibodies that could contribute to graft failure. This possibly detrimental effect might be prevented by cross matching in sensitized patients.

Adult↗
PubMed1995

[Guidelines for the diagnosis of endocarditis. Pathology of the cardiac valves].

This article reports the difficulties of the diagnosis of endocarditis, especially when blood cultures are negative. It emphasizes the respective roles of the microbiology and pathology laboratories for the processing of cardiac valves removed by surgery. It clarifies the morphological characteristics of the endocarditis.

Endocarditis↗
PubMed1981

[Changes in serum beta-thromboglobulin levels during oral contraception, cardiac valve disease and pulmonary embolism (author's transl)].

beta-thromboglobulin (beta TG), a platelet-specific protein, was measured in the plasma of 53 healthy subjects (20 men and 33 women), 53 women using estrogen-progestogen contraceptives, 31 patients with cardiac valve disease (including 19 with prosthesis) and 71 patients about to undergo scintigraphy for suspected pulmonary embolism. Compared with levels in healthy subjects, beta TG levels were significantly increased in oral contraceptive users and in cardiac patients with or without prosthesis. High beta TG levels were also found in 20 out of 28 patients with pulmonary embolism confirmed by scintigraphy, but also in some of the .9 lung patients with chronic bronchopulmonary disease. Cardiac patients treated with heparin had higher beta TG levels than non heparin-treated patients, which raises queries about a possible influence of heparin on this particular blood protein.

Adult↗
PubMed2004

Relation of an exaggerated rise in white blood cells after coronary bypass or cardiac valve surgery to development of atrial fibrillation postoperatively.

This study investigated the correlation between an elevated white blood cell (WBC) count as a marker of inflammation and the development of atrial fibrillation (AF) after cardiac surgery. WBC counts were prospectively followed in 181 consecutive patients who underwent coronary bypass or cardiac valve surgery to determine if a baseline or postoperative WBC count elevation is an independent predictor of postoperative AF.

Age Factors↗
PubMed1992

[Measurement of cardiac output by Doppler echocardiography at the 4 cardiac valves].

Many observers remain sceptical with regards to the utilization of Doppler-echocardiographic measurements of intracardiac outputs for the quantification of shunts and regurgitations. In this context, we evaluated the feasibility and validity of measuring output at the level of the four cardiac valves in a population of 35 normal subjects (24 M, 12 F) aged from 23 to 37 years (mean +/- SD = 28 +/- 4). Measurement of stroke volume and output using predetermined criteria was possible in the aortic position in 35 (100%) subjects, in the mitral position in 34 (97%), in the pulmonary position in 20 (57%) and in the tricuspid position in 10 (29%). In 14 subjects (40%), measurement was possible at 2 sites, in 14 (40%) at 3 sites and in 7 (20%) at 4 sites. Inability to measure output was most often due to poor visualization of valvular annulus. There are excellent correlations between aortic stroke volume on the one hand and the mitral (r = 0.97, SEE = 3.41 cc), pulmonary (r = 0.97, SEE = 3.69 cc) and tricuspid (r = 0.96, SEE = 2.77 cc) stroke volumes respectively on the other. These results suggest that reliable measurements of output are feasible in a majority of cases in the aortic and mitral positions but to a much more limited extent in the pulmonary and tricuspid positions; given the small SEE's, they should be useful to quantitate shunts and regurgitations, when feasible.

Adult↗
PubMed1996

Influence of stress on calcification of delipidated bovine pericardial tissue employed in construction of cardiac valves.

Since the development of cardiac bioprostheses, numerous chemical treatments have been assayed to prevent mineralization. The effectiveness of chemical treatments that eliminate lipids from the tissue was tested by combining two models. First, handmade bovine pericardial bioprostheses, subjected to chemical treatment with chloroform/ methanol and glutaraldehyde or treated with glutaraldehyde alone for use as controls, were subjected to mechanical stress in a heart valve, accelerated wear tester (100 x 10(6) consecutive cycles). Then, the bioprostheses were unstitched and tissue samples were taken from the portion subjected to maximal stress (P1) and from that surrounding the sewing ring, which had not been subjected to mechanical stress (P2), for subcutaneous implantation. After 21 and 60 days of implantation, we observed calcification of the samples subjected to mechanical stress, even after delipidating treatment, with no significant differences with respect to the control group. However, the treated samples from the portion not subjected to mechanical stress presented a slighter accumulation of calcium after 60-day implantation (5.60 +/- 3.09 mg Ca2 +/g dry weight of tissue) versus the control group (47.17 +/- 20.4 mg Ca2+/g dry weight of tissue), the difference of which was statistically significant (p < 0.01). At the time of these medium-term studies, marked calcification was observed in tissue subjected to delipidating treatment in the zones that underwent mechanical stress.

Animals↗
PubMed1999

Prevalence of cardiac valve abnormalities in afebrile injection drug users.

OBJECTIVES: To determine the prevalence of occult valvular pathology in afebrile injection drug users (IDUs) compared with an afebrile, non-IDU population. To characterize the type of valvular pathology present in light of current recommendations regarding periprocedural antibiotic prophylaxis against endocarditis. METHODS: This was a comparative, cross-sectional study involving a convenience sample of 98 patients with a history of injection drug use, and 99 non-IDU patients presenting to a large urban ED. Patients were excluded if they had one or more of the following: a history of cardiac valve abnormality, a history of endocarditis, fever on presentation, or a cardiac murmur. Data were collected that included demographics, medical history, and details of injection drug use. Transthoracic echocardiography (echo) was performed on each subject in the ED, and read in a blinded fashion by a single board-certified cardiologist. RESULTS: Among 98 IDUs and 99 non-IDUs, 12% of the IDUs had aortic valve thickening, compared with 5.1% of the non-IDUs (99% CI for difference of 7.8% = -3.0% to 18.6%). Forty-four percent of the IDUs had mitral valve thickening, compared with 25% of the non-IDUs (99% CI for difference of 18.3% = 0.9% to 35.7%). Eleven percent of the IDUs vs 1% of the non-IDUs had tricuspid valve thickening (99% CI for difference of 10.4% = 1.6% to 19.2%). No patient had pulmonic valve thickening. Six percent of the IDUs vs 0% of the non-IDUs had mitral annulus thickening (99% CI for difference of 6.3% = -0.1% to 12.8%). Twelve percent of the IDUs vs 3% of the non-IDUs had mitral chordae thickening (99% CI for difference of 9.5% = -0.4% to 19.4%). Tricuspid chordae thickening was recorded in 2% of the IDUs vs 0% of the non-IDUs (99% CI for difference of 2.1% = -1.7% to 6.0%). Most important, the prevalence of valvular regurgitation was small, and evenly distributed in the two groups. No valvular vegetations were seen. CONCLUSION: Both non-IDUs and IDUs have occult valvular pathology. There is an increased prevalence in IDUs of tricuspid and mitral valve thickening. The prevalence of valvular regurgitation, a reported indication for periprocedural antibiotic prophylaxis, was small and the affected valves were not statistically different between the two groups. These findings question the selected routine use of antibiotic prophylaxis in IDU patients undergoing invasive procedures.

Adult↗
PubMed1994

Cytosolic [Ca2+] measurements in endothelium of rabbit cardiac valves using imaging fluorescence microscopy.

Cytosolic Ca2+ plays a critical role in the secretion of endothelium-derived factors. A new preparation that allows fluorescence imaging of intracellular free Ca2+ concentration ([Ca2+]i) in endothelial cells of rabbit cardiac valves is described. Electron micrographs of the valves revealed no underlying smooth muscle cells that might influence endothelial cell responses or contribute to [Ca2+]i signaling. The valve leaflets, which were < 100 microns in diameter, were visualized using a specially designed chamber and a long working distance fluorescence objective. The semilunar valves (pulmonary and aortic) responded to endothelium-dependent vasodilators, including acetylcholine, with an increase in [Ca2+]i. Synchronized [Ca2+]i transients were observed in the endothelial monolayer in response to agonist stimulation in K(+)-free solutions. The ability to monitor changes in [Ca2+]i in a native endothelial monolayer provides a more realistic assessment of stimulus-response coupling within individual cells and communication between cells of native endothelium. In addition, this preparation affords an opportunity for comparative studies of endothelium-related pathophysiologies, which can be induced experimentally in animal models.

Acetylcholine↗
PubMed2000

Cardiac valve replacement in patients on dialysis: influence of prosthesis on survival.

BACKGROUND: Mechanical valves have been recommended for patients on dialysis because of purported accelerated bioprosthesis degeneration. This study was undertaken to determine time-related outcomes in dialysis patients requiring cardiac valve replacement. METHODS: From 1986 to 1998, 42 patients on chronic preoperative dialysis underwent valve replacement; 17 received mechanical valves and 25 received bioprostheses. Age was similar in both groups: 54+/-18.5 years (mechanical) and 59+/-15.5 years (bioprosthetic, p = 0.4). Sites of valve replacement were aortic (27), mitral (11), and aortic and mitral (4). Follow-up was 100% complete. RESULTS: Survival at 3 and 5 years was 50% and 33% after mechanical valve replacement, and 36% and 27% after bioprosthetic valve replacement (p = 0.3). Four patients with bioprostheses required reoperation: 3 for allograft endocarditis and 1 at 10 months for mitral bioprosthesis degeneration. One patient who received a mechanical valve required reoperation. CONCLUSIONS: Prosthetic valve-related complications in patients on dialysis were similar for both mechanical and bioprosthetic valves. Because of the limited life expectancy of patients on dialysis, bioprosthesis degeneration will be uncommon. Therefore, surgeons should not hesitate to implant bioprosthetic valves in these patients.

Adult↗