ISSN:0886-0440    

DOI:10.1111/j.1540-8191.1991.tb00341.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractFailure of reconstructive procedures of the mitral valve is often ascribed to diffuse alteration of the subvalvular apparatus, which prevents the utilization of well‐established techniques such as chordal transposition or shortening. For this reason, in 1986 after 2 years of animal experiments, we started the clinical use of expanded‐polytetrafluoroethylene mitral chordae. Details of the surgical procedure are presented. Our experience is based on 51 patients with a mean follow‐up of about 20 months (range 3–57). Four patients had the valve replaced during the same operation: one patient died later of cardiac failure and two underwent reoperation, 8 and 18 months after operation. Forty‐one patients are in New York Heart Association Functional Class I and three in Class II. We suggest this technique in association with other traditional procedures to increase the number of mitral valves repaired, mostly because of degenerative

ISSN:0886-0440    

DOI:10.1111/j.1540-8191.1991.tb00342.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractDuring a 4‐year period (1986–1989), 3,502 patients had percutaneous transluminal coronary angioplasty (PTCA) in our institution. One hundred nineteen (3.4%) patients required emergency coronary artery bypass graft surgery (CABG) because of abrupt vessel closure following PTCA. Factors associated with vessel closure included lesion angulation ± 90° (p<0.007), the presence of thrombus (p<0.02), or a long (± 2 cm) lesion (p<0.03). Of these 119 emergency CABG patients, 108 (91%) arrived in the operating room in a stable condition (group I) and 11 (9%) were in cardiogenic shock (group II). Five (45%) of the group II patients were admitted to the hospital with an acute myocardial infarction and all 11 patients had a higher incidence of multivessel disease (p<0.05) and lower left ventricular ejection fraction (p<0.001) than group I patients. The overall surgical mortality was 10.1%; however, in group I the mortality was 5.6% and in group II it was 54.5% (p<0.001). The vessel that abruptly closed (“culprit vessel”) was the left anterior descending (LAD) in 60%, the right coronary artery in 27%, and the left circumflex in 13%. The internal mammary artery was utilized to bypass the culprit artery in 51 (43%) patients, including 50% of the culprit LADs. With group I culprit LAD patients, when the left IMA was the bypass conduit, there were no hospital deaths nor strokes and there was a 6.3% incidence of perioperative

ISSN:0886-0440    

DOI:10.1111/j.1540-8191.1991.tb00343.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractA new intravascular probe designed to facilitate small vessel, especially coronary artery, anastomosis is presented. Modifications in anastomotic techniques by using the device are discussed.

ISSN:0886-0440    

DOI:10.1111/j.1540-8191.1991.tb00344.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractIn patients undergoing aortic valve replacement, allograft valves stored at 4°C in a nutrient medium have been associated with excellent immediate and long‐term results. The effects of this method of prolonged storage on the antigenic, immunological, and cellular characteristics of these grafts are incompletely understood. This study was designed to study these phenomena in rat aortic valves subjected to antibiotic sterilization and stored for up to 3 weeks in RPMI containing 10% fetal calf serum. Selected valves from Brown Norway rats were implanted heterotopically into the abdominal aorta of Lewis rats. Other valves were studied prior to transplantation. Antigenicity was determined by immunocytochemical staining using monoclonal mouse antibodies directed at Class I and Class II rat antigens. Immunogenicity was determined by duration of second‐set skin graft survival following heterotopic aortic valve implant. Endothelial cell viability was determined by flow cytometric analysis of endothelial cells harvested from aortic valve allografts by collagenase digestion. Only fresh valves and valves stored for 1 day were positive for Class I antigens; no valves were positive for Class II antigens. Duration of skin graft survival was prolonged with greater duration of storage, but grafts remained immunogenic after 21 days of storage. Endothelial cell viability declined from 95% in the fresh valves to 64% after 21 days of storage. With prolonged duration of allograft valve storage at 4°C, there is an attenuation of antigenicity, immunogenicity, and endothelial cell viability. Loss of endothelial cells may contribute to the changes in immunological responses to the valve allografts. The expression of antigens on the endothelial surface is not a reliable predictor of immunological res

ISSN:0886-0440    

DOI:10.1111/j.1540-8191.1991.tb00345.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractFreehand aortic allograft valves that had been previously sterilized with antibiotics were recovered at reoperation for biomechanical testing. The elastic extensibility of two leaflets from each explanted allograft stored in modified Hank's solution at 4°C were measured using biaxial testing techniques. It was found that the leaflets had lost a significant amount of the natural, preimplant tissue extensibility. Computer simulation was used to investigate the likely consequences of such a profound change in the biomechanical characteristics of the leaflets on whole valve function. We found that the valve becomes progressively more incompetent as leaflet extensibility is lost and the stress levels at the commissures rise sharply with reduced coaptation. The stress levels in the load‐bearing leaflet center are increased in the ventricularis as load is transferred from the fibrosa. The measured change in the radial extensibility of the aortic allograft leaflet needs to be allowed for when sizing the graft at insertion. Inserting the largest possible graft will maximize the time to the onset of central incompetence and improve valvar longevity by lowering the stress during diasto

ISSN:0886-0440    

DOI:10.1111/j.1540-8191.1991.tb00346.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThis study was designed to evaluate the early phase events occurring in a stented pulmonary homograft valve implanted in the tricuspid position. A human pulmonary homograft was sterilized in antibiotic solution for 48 hours and cryopreserved in liquid nitrogen (–176°C). Following thawing and trimming, the pulmonary valve was mounted on a Dacron cloth‐covered Delrin stent and implanted into the tricuspid position in 3‐month‐old sheep, for a mean of 95 ± 5 days. Seven animals were studied. Morphological assessment indicated good structural tissue preservation despite a decrease in viable fibroblasts noted in the distal part of the leaflets. The collagen fibers remained unchanged, and no tissue calcification was found. Viability of the mounted homograft was evaluated using an in vitro tissue culture method, and the viable cells underwent chromosomal analysis to identify whether they originated from the donor or host. Cells with 56 chromosomes, a number intrinsic to sheep cells, were cultured from the donor‐recipient junctional area. Hemodynamic and angiographic data, which were collected at the time of both implantation and explantation, revealed no functional deterioration of the implanted valve over 3 months. At the time of explantation, six of the seven valves were competent and no cusp retraction or thickening was noted. The seventh valve had deteriorated due to endocarditis. We conclude that stented cryopreserved pulmonary homografts may be useful as bioprostheses in the tricusp

ISSN:0886-0440    

DOI:10.1111/j.1540-8191.1991.tb00347.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractIt has been postulated that flexible stent posts can reduce tensile stress at the commissures of tissue heart valves by about 90% when compared with the same valve mounted on a rigid stent. We have used a detailed computer model to investigate the role of flexible stent posts in reducing stress in the leaflets of three types of bioprosthetic heart valves: the bovine pericardial and the high‐ and zero‐pressure fixed porcine valves. The models use stress/strain data from biaxial experiments to characterize the tissue properties and are subjected to a back pressure of 120 mmHg. We found that strain was reduced linearly with stent post deflection and that this was a purely static process–it did not require the load to be applied impulsively. This finding was in close agreement with earlier experimental studies, which measured the same strain reduction whether the valve was loaded quasi‐statically or at physiological rates. In addition, we found that for this mechanism to be effective the valve must have good coaptation at the center and the tissue should be stiff; in other cases, the advantages of strain reduction through the use of a flexible stent are considerably dim

ISSN:0886-0440    

DOI:10.1111/j.1540-8191.1991.tb00348.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe implantation of aortic allografts as well as stentless, freehand porcine xenograft valves requires proper sizing of the graft for the recipient aortic root. To visualize the aortic valve in motion and measure the cyclic expansion of the aortic root, we developed an isolated porcine heart model and a computerized three‐dimensional reconstruction technique. Dynamic and static expansions of the aortic root were obtained from beating and arrested porcine hearts, and additional static expansions at varying pressures were measured from reconstructed three‐dimensional models of valves obtained with high‐resolution magnetic resonance imaging. Measurements of aortic root expansion have shown that it is highly dependent upon the pressures imposed on the heart. Although the aortic root expanded by only 5% between systolic pressures of 60 and 100 mmHg, the total expansion was up to 40% between rest and cyclic pressurizing to 100 mmHg. This data suggest that unstented xenograft valves should be sized 30% to 40% larger than the collapsed size of the recipient aorta. Proper sizing of valves on stents should also be attempted to reduce the large amount of leaflet redundancy that current stenting techniques pr

ISSN:0886-0440    

DOI:10.1111/j.1540-8191.1991.tb00349.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe hydrodynamic function and leaflet dynamics of second generation porcine valves prepared with low‐ or zero‐pressure fixation have been studied and compared to first generation porcine bioprostheses, bileaflet, and tilting disc mechanical valves. The Carpentier‐Edwards Supra‐Annular and Hancock II valves showed lower pressure drops than the Medtronic Intact valve and first generation porcine valves, and comparable overall energy losses to mechanical valves at normal cardiac outputs. Only the zero‐pressure fixed Intact valve showed synchronous leaflet opening. Delayed leaflet opening and high opening pressures were found in both low‐ and high‐pressure fixed porcine valves. All porcine bioprostheses showed high open leaflet bending strains. Fixation of valve leaflets with “near zero” pressure fixation and a more physiological neutral geometry is necessary to ensure synchronous leaflet opening at low flows and a reduction in commissura

ISSN:0886-0440    

DOI:10.1111/j.1540-8191.1991.tb00350.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY