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At least 379 records · Page 21Linked to original sources
PubMed1988

Microvascular polytetrafluoroethylene prostheses: the cellular events of healing and prostacyclin production.

This study was undertaken to obtain more insight into the morphologic and functional performance of microvascular polytetrafluoroethylene (PTFE) prostheses. Therefore, both the cellular events of healing (n = 30) and the prostacyclin production (n = 18) of microvascular polytetrafluoroethylene prostheses (length 10 mm, internal diameter 1.5 mm) were evaluated from 1 hour up to 3 months after implantation into the abdominal aorta of rats. After implantation, the graft surface became scarcely covered with platelets. From 1 week onward, endothelial cells originating from the anastomotic sides grew in over the graft surface, covered only about half the prostheses after 3 months of implantation, but did produce normal amounts of prostacyclin as compared to normal endothelium. Only near the anastomotic sides one to two layers of smooth-muscle-like cells developed underneath the neoendothelial lining. Perigraft tissue ingrowth into the wall of the polytetrafluoroethylene prostheses was scarce. The overall patency rate was 98 percent. It was concluded that optimalization of the healing characteristics of microvascular polytetrafluoroethylene prostheses may provide a prosthesis that is more suitable for clinical microsurgery.

Animals↗
PubMed1978

Pattern of arrangement of smooth muscle cells in neointimae of synthetic vascular prostheses.

Neointimae of fabric vascular prostheses of three types (crimped and knitted [A], stretchable [B], and expansile [C]) were examined under both light and electron microscopes from 1 to 1,240 days after implantation in the thoracic aorta of 161 dogs. With all types of prostheses, a very uniform arrangement of smooth muscle cells was observed beneath the endothelial cells. In the crimped and knitted prostheses (A), the smooth muscle cells in the neointima showed a regular arrangement perpendicular to the direction of the bloodstream at each inner ridge of the crimp. In the stretchable prostheses (B), which can stretch only longitudinally, the long axes of the smooth muscle cells oriented in rows parallel to the bloodstream. In the expensive prostheses (C), which can expand only circumferentially, the smooth muscle cells were perpendicular to the bloodstream. These observations suggest that the arrangement of the smooth muscle cells in neointima is largely governed by the tension to which they are subjected.

Animals↗
PubMed1987

[Progressive complications associated with polyester arterial prostheses. Study of 61 specimens following surgical excision].

Reports of individual surgical cases tend to be anecdotal because of the unique circumstances surrounding the patient, the surgeon, the intervention and, where applicable, the prosthetic device. To overcome this limitation the authors have taken a wider collaborative approach and report the analysis of 61 explanted polyester arterial prostheses associated with delayed complications on 53 patients reoperated upon in six different French hospitals. One advantage of such an independent and centralized retrieval programme is that the impact of centre specific factors, such as patient selection and surgical techniques, is minimized. Consequently, by following a standardized protocol for the evaluation of the morphologic, pathologic and mineralogic characteristics of the tissue surrounding the excised grafts, as well as the textile structure of the prostheses themselves, it has been possible to distinguish between iatrogenic and disease related complications and to demonstrate a number of general findings associated with the clinical performance of polyester arterial prostheses. Complications such as thromboses, infections and false aneurysms appear to occur randomly after different lengths of implantation, thicker fibrous tissue capsules are associated with velour grafts with highly textured yarns, the incidence of mineralized tissue and of endothelialized luminal surfaces is rare, weft knitted textile prostheses appear less mechanically stable and more sensitive to iatrogenic trauma than warp knitted, and the incidences of lipid and cholesterol adsorption, bacterial colonization and sterile fluid loss need further investigation. These observations lead to the recommendation that for patients with longer life expectancies surgeons should consider selecting low porosity, woven or warped knitted prostheses which contain yarns that have not been highly textured.

Adult↗
PubMed1982

Early normalization of platelet survival by endothelial seeding of Dacron arterial prostheses in dogs.

Current synthetic vascular prostheses do not acquire a complete lining of vascular endothelium in humans or dogs. Seeding of autogenous venous endothelium has bee reported to remedy this defect, but previous studies have been primarily morphologic. To see if venous endothelial seeding caused a measurable decrease in platelet-prosthetic interaction in vivo, serial 111In-labeled platelet survival studies were done in dogs with seeded (N = 8) and unseeded (n = 9) thoracoabdominal Dacron bypass prostheses.l Changes in platelet survival time (PST) were compared with endothelial coverage scores, which were determined by blinded survey of removed prostheses by scanning electron microscopy (SEM). The PSTs before surgery (+/- SD) were 5.02 +/- 0.79 days (seeded) and 5.31 +/- 0.99 days (control) (P = 0.51). Seven weeks after surgery the PSTs were 4.01 +/- 1.10 days (seeded) and 2.67 +/- 0.88 days (control) (P = 0.013). The subgroup of four dogs with seeded prostheses that had complete endothelial coverage showed restoration of the platelet survival pattern to that of the linear decay seen before surgery, SEM studies showed that this normalization of PST occurred despite the presence of small nidi of platelet adhesion on exposed Dacron fibers and irregularities of the endothelial pattern consistent with flow disturbances and venous jet lesions near anastomoses. Endothelial seeding, when technically successful, appears to sharply curtail the degree of platelet interaction with vascular prostheses and restores a normal platelet survival pattern. Longer studies of seeded prostheses are needed to determine if seeding protects against the late complications of intimal hyperplasia and thrombotic occlusion.

Animals↗
PubMed1984

Differentiation of vascular prostheses in dogs with serial tests of in vivo platelet reactivity.

Three different vascular prostheses (standard weight knitted Dacron, double velour knitted Dacron, and expanded polytetrafluoroethylene) were implanted in the aortas of dogs, and serial determinations of platelet survival and platelet serotonin were monitored at 12-week intervals for 1 year. Prostheses were then removed and luminal coverage with endothelialized neointima and production of prostacyclin were measured. Changes in platelet survival were correlated with changes in platelet serotonin, and both measurements reflected in vivo platelet reactivity with the vascular prostheses. These changes were unique for each type of prosthesis and were dependent upon physical characteristics and the rate and degree of coverage of the prosthetic surface with endothelialized neointima that produced prostacyclin. Prostheses that reduced platelet survival and platelet serotonin the least as shown by serial evaluation were found at harvest to be the most completely paved with nonthrombogenic neointima. In dogs, these techniques allow differentiation of vascular prostheses and provide a useful animal model for their evaluation.

6-Ketoprostaglandin F1 alpha↗
PubMed1984

Seeding human arterial prostheses with mechanically derived endothelium. The detrimental effect of smoking.

Endothelial healing of Dacron arterial prostheses can be hastened in dogs by seeding autogenous venous endothelium onto the prostheses in a single-staged operation. To determine whether this technique enhances the patency of human grafts, we studied the results of 186 operations on 161 patients performed between February 23, 1978, and December 1, 1982. Alternately allocating patients to treatment with seeded and unseeded Dacron knitted prostheses, we performed axillary-femoral and axillary-femoral-femoral bypasses in 11 patients (six seeded and five unseeded) and femoral-femoral bypasses in 28 (13 seeded and 15 unseeded). By a randomized block method of treatment allocation, femoral-popliteal grafts were installed in 147 limbs (112 vein, 18 seeded, and 17 unseeded). Patency was analyzed by the life-table method. Overall, femoral-femoral and femoral-popliteal bypasses demonstrated no difference between the seeded and unseeded grafts. Patency was somewhat better in seeded than unseeded axillary-femoral bypasses. Nevertheless, nonsmokers with seeded femoral-popliteal Dacron grafts enjoyed a significantly better graft patency than those with unseeded grafts (p = 0.035), whereas a substantial deterioration of seeded Dacron grafts was observed in those patients who smoked (p = 0.008 at 6 months). Vein grafts performed better than either seeded or unseeded Dacron prostheses (p = 0.016). Serum beta-thromboglobulin (BTG) levels varied widely and did not differ among any of the treatment groups. We concluded that endothelial seeding improved the patency of human arterial prostheses but that results were worse if the patient was a smoker. BTG was not a useful measure of the platelet activation induced by an arterial prosthesis.

Blood Coagulation Disorders↗
PubMed1983

[Reoperations on heart valve prostheses. Apropos of 58 cases].

In the period from 1968 to November 1980, 1 023 patients underwent surgery for single or multiple valve replacement. Fifty three patients (6,6% of the follow-up population) had to be reoperated, including 5 patients who had to be reoperated twice, giving a total of 58 reoperations. The average interval before reoperation was 30 months. The incidence was similar in monovalvular (7,5 p. 100 mitral valves, 5 p. 100 aortic valves) and polyvalvular (7 p. 100) cases. On the other hand, the incidence of reoperation of tricuspid prostheses (17 p. 100) was significantly superior to that of mitral valve (5,3 p. 100) or aortic valve (3,8 p. 100) prostheses. In 91 p. 100 of cases, the indication for reoperation was prosthetic valve dysfunction related to endocarditis in over a third of cases (21). In 32 cases, reoperation was required in the absence of any infectious process: 13 spontaneous perivalvular leaks, 10 thromboses, and 9 stenosing prostheses. There were no reoperations for wear of the prosthetic material. Only 9 p. 100 of patients were reoperated for uncorrected valvular disease. The prognosis of these reoperations was poor; hospital mortality being 42,5 p. 100. This high mortality rate is explained by the frequency of reoperation for infective endocarditis (36 p. 100) in our series, the mortality of which was 73,6 p. 100 and even higher when reoperation was an emergency for infectious or hemodynamic reasons. There was also a high mortality rate with reoperation for thrombosis (30 p. 100) because of the severe myocardial dysfunction in thrombosis of tricuspid prostheses and the emergency situation associated with mitral prosthetic valve thrombosis. Excluding these two complications, the average mortality was 21 p. 100. Although the surgical indications are relatively easy for thrombosis, perivalvular leak and stenosing prostheses, they are particularly difficult in infectious endocarditis especially with regards to the timing of reoperation. We believe that, ideally, reoperation should be delayed as long as possible to allow the antibiotic therapy the maximum time to take effect. Surgery can then be performed after controlling the infection and before the installation of severe hemodynamic distress.

Adolescent↗
PubMed1984

[Experience with the treatment of suppuration surrounding synthetic vascular prostheses].

Experience with the conservative and operative treatment of suppurations around vascular prostheses in 16 patients is presented. Spread of the purulent inflammation around prostheses from the place of primary suppuration on the femur up to the portions proximal to the inguinal ligament was taking place within the first 1-2 weeks after the appearance of the first symptoms of suppuration. Partial resection of infected portions of the prostheses and substitution of them by autovenous grafts are thought to be more expedient within these terms. Such operations are less traumatic and technically more simple than interventions associated with a complete ablation of aorto-femoral prostheses and a simultaneous substitution of them by new vascular prostheses or transplants.

Anti-Bacterial Agents↗
PubMedDate not supplied

Comparison of intraoperative flow measurements and haemodynamic findings at follow-up in patients with different aortic disc valve prostheses.

Intraoperative as well as postoperative assessment of effective orifice area, determined by relating flow through a prosthetic heart valve to the pressure gradient measured across the valve, provides a data base for comparison of different types of cardiac prostheses. As a measure of valve performance, we have used the derivation of both the effective area according to the Aaslid formula measured intraoperatively and to the Gorlin formula measured at a re-catheterization study. We also established the parameter 'effective index area', Ia or Ii. Ia is defined as the ratio between the effective orifice area and the annulus orifice area, and Ii as the ratio between the effective orifice area and the internal orifice area of the valve housing. The patients included in the study had either Lillehei-Kaster, Björk-Shiley or Hall-Kaster aortic valve prostheses inserted. In most of the Lillehei-Kaster prostheses, Ia varied around 0.27 and Ii around 0.56, while the corresponding values in the Björk-Shiley prostheses were 0.35 and 0.56, increasing to around 0.50 and 0.75 respectively in the Hall-Kaster prostheses.

Adult↗
PubMed1978

Non--cloth-covered caged-ball prostheses. The second decade.

The Starr-Edwards Models 6120 mitral and 1200/60 aortic valves are caged-ball prostheses with cloth-covered sewing rings and bare-metal struts. Introduced in 1965, they have been in continuous clinical use longer than any other currently available heart valve prostheses. Late results with this valve are analyzed and compared with recent series employing other current valve prostheses. One hundred thirty-four mitral 6120 prostheses were inserted at the University of Oregon Health Sciences Center from 1965 through 1977, with 118 operative survivors followed for a mean of 5.4 years. Twelve-year survival rate (+/- standard error) was 50 (+/-8) percent. Twelve percent of late deaths were valve related. Eighty-eight (+/-5) percent of valves were still in place at 12 years. The embolic rate was 5.8 (+/-1.0) percent per patient-year for all emboli and 2.2(+/-0.6) percent per patient-year for serious emboli. Two hundred forty-nine operative survivors among 282 patients undergoing aortic valve replacement during the same period of time were followed for a mean of 4.3 years. Twelve-year survival was 61 (+/-6) percent and the removal-free rate was 92(+/-5) percent. Six percent of late deaths were valve related. Embolic rates were 5.0 (+/-.7) percent and 1.8 (+/-.4) percent per patient-year for all emboli and serius emboli, respectively. Structural failure, specifically ball variance, was not encountered with this prosthesis. Ninety percent of 10 year survivors are in N.Y.H.A. Functional Class I or II. There was one anticoagulant-related death in 1,698 patient-years of follow-up. The current non--cloth-covered caged-ball valves provide unquestionable durability and well-documented results into their second decade of use. They provide a base line for comparison with newer prostheses and offer a valid, current choice for both aortic and mitral valve replacement.

Aortic Valve↗
PubMed1982

[Non-invasive determination of pressure gradients of heart valve prostheses using Doppler ultrasound].

Noninvasive measurements of pressure gradients by continuous wave Doppler ultrasound technique were carried out in 40 patients with correctly functioning heart valve prostheses (10 Björk-Shiley in aortic position, 10 Björk-Shiley in mitral, 10 St. Jude Medical in aortic and 10 St. Jude Medical in mitral) and in 10 patients with normal aortic and 10 patients with normal mitral valves. The pressure gradients were slightly but significantly higher in prosthetic than in normal heart valves (p less than 0.005). Pressure gradients in Björk-Shiley prostheses were higher than in St. Jude Medical prostheses both in aortic (18.4 +/- 2.6 vs 9.6 +/- 1.9; p less than 0.01) and in mitral position (8.2 +/- 1.1 vs 5.4 +/- 0.8; p less than 0.05). The pressure gradient was inversely related to valve size in Björk-Shiley prostheses (r = -0.60 for aortic and r = -0.42 for mitral valves; p less than 0.05) but not in St. Jude Medical prostheses. The non-invasive Doppler technique should be useful in the diagnosis of prosthetic valve obstruction.

Aortic Valve↗
PubMedDate not supplied

[Design and evaluation of a duplication of the cardiac for the evaluation of valvular prostheses].

Recently, several different models of valvular prostheses have been developed in which biological material, like duramater and perycardium, is being used for their manufacturing. Since these valves have to be manufactured one by one, the possibility of obtaining heterogeneous results is very high, thus it is very important to have a system to evaluate the behavior of these prostheses. The objective of this project was to design and evaluate a cardiac cycle duplicator to test the function of valvular prostheses. The system consists of a double plexiglass chamber, separated by the valvular prosthesis being studied. The superior "auricular" chamber is connected to a reservoir where the height of the column of saline can be modified. The interior "ventricular" chamber is connected to a pump that generates pressure pulses at constant intervals which simulate ventricular systoles. The other end of the pump connects with an artificial Starling's resistance. The data obtained from this system allows the quantification of the following: 1) Functional diameter, form and area of maximal opening; 2) valve motility; 3) sufficiency of the prostheses; 4) velocity of valve opening and closing; 5) rigidity of the valves; 6) optimal pressure gradient for adequate valvular function. The system makes possible the evaluation and comparison of the function of these valvular prostheses.

Biocompatible Materials↗
PubMed1994

[Aortic valve replacement in old age. The results and follow-up echo-Doppler study of the prostheses].

BACKGROUND: To analyze the results of aortic valve replacement in elderly patients and to evaluate the hemodynamic performance of valvular prostheses, we have retrospectively studied the patients 70 years of age or older, who consecutively underwent aortic valve replacement in our Center. METHODS: From January 1988 to December 1992, a series of 112 patients aged 70 to 88 years (mean 74.8 +/- 3.8 years) underwent aortic valve replacement; 49.1% of patients were male; aortic valvular lesion was: stenosis in 65.2%, insufficiency in 9.8% and mixed stenosis and insufficiency in 25.0%. In 73.2% isolated valve disease was present; in 25.0% coronary artery disease was associated. Preoperatively 58.9% were in New York Heart Association class III, and 29.5% were in class IV. Concomitant extracardiac diseases were present in 73.2%. The types of valve prostheses employed were: mechanical tilting disc (28 cases), mechanical bileaflet (40 cases), bioprosthesis (44 cases). A significantly favourable relationship between body surface area and size of prostheses was evident. RESULTS: Overall hospital mortality was 8.9% (5.4% for elective isolated aortic valve replacement) with significant difference (p = 0.006) related to criteria for surgical indication (elective 6.4%, urgent 10.0%, emergency 37.5%). Valvular lesion, age, sex, associated coronary artery bypass surgery, the values of peak and mean aortic valve gradient, the relative wall thickness and the presence of extracardiac disease have not been identified as risk factors for hospital mortality. The mean follow-up of the 102 discharged patients is 27.1 +/- 16.5 months (range 2 to 64 months). Eight late deaths (7.8%) occurred; the overall actuarial freedom from all deaths (excluding hospital mortality) was 95.6 +/- 2.2% at 1 year and 88.6 +/- 4.0% at 3 and 5 years. Five non fatal valve related complications occurred: hemorrhage in 4 cases (1.8% pt/yr) and hemolysis in 1 case (0.4% pt/yr). Ninety-seven percent of patients were found to be in NYHA functional class I or II. Comparative echocardiographic evaluation of the prostheses showed significant differences in mean gradient: regarding 21 mm size lower in bileaflet than in tilting disc and regarding 23 mm size lower in bileaflet than in tilting disc or bioprostheses. CONCLUSIONS: Aortic valve replacement has proved to be safe and effective in the elderly population and is considered the procedure of choice for aortic valve disease. Although we consider mandatory to choose the valve substitute matching different physiopathological and psychological attitudes of individual patient, mechanical prostheses and particularly bileaflet type for size < or = 21 mm should be preferred.

Aged↗
PubMed1993

[Occlusion of aorto-femoral vascular prostheses after long-term implantation].

The authors present a report dealing with their experience with reoperations for occlusion of vascular prostheses implanted in aorto-femoral region in the late postoperative period. The most frequent cause of this occlusions was the obstruction of the outflow track at the distal anastomosis. In small arteries (under 5 mm) this obstruction was mainly caused by myointimal proliferation which originated from the host artery. In the early period after occlusion it is possible to remove the thrombus from the prostheses mostly in all patients by means of Fogarty catheter and to ensure the long lasting passage of the prostheses by plastic operations of the origin of profunda femoral artery. In long lasting occlusions of the prostheses can thrombolytic therapy 1-2 weeks before reoperation facilitate removing of the thrombus. In 113 patients with the different type of reoperations for occlusion of the prostheses in the aorto-femoral region we succeeded in 102 patients (90.3%). In 8 patients the reoperation was not successful (7%) and we had to amputate the distal extremity and three patients (2.3%) died from the heart complications in the early postoperative period.

Adolescent↗
PubMed1993

Subsidence, tip, and hump micromovements of noncoated ribbed femoral prostheses.

The micromovements of 18 ribbed femoral prostheses were measured for two years postoperatively. Repeated roentgen stereophotogrammetric examinations (RSA) were used to measure distal migration of the center of the prostheses and movements of the prosthetic hump and tip. During the first six postoperative months, an increasing number of prostheses migrated significantly. Migration was first observed at the tip. Two years after the operation, one prosthesis had been revised because of pain. Thirteen of 17 remaining prostheses had subsided, 12 displayed hump and 16 tip migration, and eight had rotated about the longitudinal axis of the femur. In these hips, the instant center of rotation ran obliquely through the greater trochanter or the isthmus of the femur. Clinical follow-up examination and measurements on conventional roentgenograms disclosed a correlation between pain, the extent of sclerosis surrounding the prostheses, and the distal migration according to RSA measurements.

Adult↗
PubMed1993

[Biodegradation of dacron vascular prostheses. Physico-chemical, histological, morphometric and ultrastructural study].

The paper deals with study of long-term stability as far as concerns Dacron vascular prostheses in woven and knitted double velour. Among our vascular prostheses case-reports, we evaluated three of them explanted after 11, 12, 20 years; all of the prostheses were patent. Chemical-physical, histopathological and ultrastructural analysis have been carried on in order to evaluate in vivo ageing of the examined prostheses. The results all indicate strong alterations of the original properties related to double velour of knitted prostheses and weak alterations of woven one.

Aged↗
PubMedDate not supplied

Magnetic resonance study of virgin and explanted silicone breast prostheses. Can proton relaxation times be used to monitor their biostability?

The development of sensitive and non invasive magnetic resonance (MR) techniques for monitoring the fate of silicones in breast prostheses in vivo requires detailed knowledge of the MR properties of these silicones. To characterize changes in the proton dynamics, relaxation time measurements (T1 and T2) were obtained on virgin and explanted breast prostheses using both spectroscopic and imaging techniques in a magnetic field of 1.5 Tesla. Averaged transverse relaxation times (T2) were observed to depend neither on the measurement technique employed (virgin silicone, T2 = 160 +/- 5 msec with imaging and 154 +/- 9 msec spectroscopically) nor on the effect of being implanted in the body for various periods of time ranging from 4 months to 17 years (explanted silicone, T2 = 164 +/- 16 msec with imaging and 159 +/- 25 msec spectroscopically). Average longitudinal relaxation times (T1) were also found to be similar for virgin and explanted prostheses (virgin silicone T1 = 899 +/- 32 msec, explanted silicone T1 = 879 +/- 75 msec, measured with imaging), but appeared to depend on the measurement technique employed (virgin silicone T1 = 764 +/- 17 msec, explanted silicone T1 = 765 +/- 23 msec, measured spectroscopically). Although the measured relaxation times did not reveal any differences between virgin and explanted prostheses, marginal differences were detected between the relaxation times of explanted prostheses from different manufacturers. More reference data on standard silicone products may be required before changes in implanted silicone can be assessed using proton magnetic relaxation times.

Biocompatible Materials↗
PubMed1996

[Contribution of multiplane transesophageal echocardiography in the study of mitral valve prostheses].

Many reports have confirmed the value of transoesophageal echocardiography in the diagnosis of mechanical mitral valve prosthesis dysfunction: new biplane and multiplane probes seem to provide additional information in the assessment of cardiac disease. The aim of this study was to quantify the additional value of these new probes in the assessment of mitral valve prostheses. Seventy-five mitral valve prostheses were assessed with the multiplane probe, 45 normal bileaflet prostheses, 17 with regurgitant dysfunction and 12 with non obstructive thrombi and/or strands, and one with a blocked leaflet. In order to compare the respective values of monoplane, biplane and multiplane probes, the recordings were performed at 0 degrees, 90 degrees and from 0 degrees to 180 degrees in continuous sweep mode through the scanning plane. Globally, with the monoplane assessment, it was only possible to visualise both leaflets simultaneously in 13% of cases. The majority of prostheses was correctly analysed between 60 and 100 degrees. This was of paramount importance for the diagnosis of blockage of one leaflet. With respect to para-prosthetic valve regurgitation, the transverse view allowed visualisation of the lateral and paraseptal annular regions. The addition of a longitudinal view allowed visualisation of anterior and posterior regurgitant jets: the supplementary views provided by the multiplane probe allowed detection of small regurgitant jets in the diagonal planes between the longitudinal and transverse views. The multiplane probe offers the possibility of identifying the precise origin of the jet and helps quantification and peroperative localisation of its position. Small, non-obstructive thrombi and strands are better seen using a multiplane probe, especially when of small size. Therefore, multiplane transoesophageal echocardiography improves the assessment of mitral valve prostheses, the majority of diagnoses being, however, accessible with biplane probes.

Echocardiography, Transesophageal↗