Prevention of focal intimal hyperplasia in rat vein grafts by using a tissue engineering approach

The present study focused on the role of blood flow in the formation of focal intimal hyperplasia in vein grafts, as well as the development of an engineering approach that can be used to eliminate disturbed blood flow and prevent blood flow-related focal intimal hyperplasia. A rat vein graft model was constructed by interposing a jugular vein into the abdominal aorta with end-to-end anastomoses. Locally disturbed flow was identified by analyzing particle streak-lines in methyl salicylate-cleared and perfused vein grafts in vitro with a physiological Reynolds number. At day 10, 20, and 30 after surgery, focal intimal hyperplasia of the vein grafts was examined using a histological approach and the density of alpha-actin positive cells was determined using immunohistological and fluorescent approaches. Results showed that apparent eddy blood flow formed at the proximal, but not at the distal, end of the vein grafts due to graft-host diameter mismatch and local geometric distortions, and was associated with apparent focal intimal hyperplasia. The thickness of the alpha-actin positive layers of the proximal vein grafts was significantly higher than that of the distal grafts (192 +/- 27 vs. 94 +/- 18 microm, 278 +/- 55 vs. 124 +/- 20 microm, and 288 +/- 24 vs. 131 +/- 23 microm for day 10, 20. and 30, respectively). The density of the alpha-actin positive cells, however, was similar between the proximal and the distal regions (3569 +/- 361 vs. 3285 +/- 343 cells/mm2, 5540 +/- 650 vs. 5376 + 887 cells/mm2, and 5465 +/- 791 vs. 5278 +/- 524 cells/mm2 for day 10, 20, and 30, respectively). When eddy blood flow was eliminated by matching the graft-host diameters using a tissue engineering approach, the average thickness of the alpha-actin positive layers of the proximal (71 +/- 15, 86 +/- 16, and 85 +/- 14 microm for day 10, 20, and 30, respectively) and the distal vein grafts (68 +/- 13, 80 +/- 14, and 79 +/- 13 microm for day 10, 20, and 30, respectively) was reduced significantly. The density of the alpha-actin positive cells was also reduced significantly in the proximal (2946 +/- 359, 3261 +/- 295, 3472 +/- 599 cells/mm2 for day 10, 20, and 30, respectively) and in the distal regions (3151 +/- 511, 3466 +/- 687, 3593 +/- 688 cells/mm2 for day 10, 20, and 30, respectively). The thickness of the alpha-actin positive layers and the density of the alpha-actin positive cells were not significantly different between the proximal and distal regions of the engineered vein grafts at each observation time. These results suggest that eddy flow may develop in vein grafts and may facilitate the formation of focal intimal hyperplasia, and the vascular tissue engineering approach developed in this study may be used to prevent blood flow-related focal intimal hyperplasia in vein grafts.     

Acute hypertension impairs endothelium-dependent vasodilation

PURPOSE: Modified anastomotic techniques utilizing autogenous vein-cuffs or patches have been devised with the hope of improving prosthetic graft patency. The mechanisms of the presumed improvement in patched anastomoses have never been elucidated and remain speculative. We characterized the healing response of the Taylor vein patch in prosthetic arteriovenous fistulae in a canine model of intimal hyperplasia. METHODS: Six adult dogs underwent placement of bilateral (6 patched, 6 control) 4-mm diameter expanded polytetrafluoroethylene loop femoral artery-vein fistulae. Serial duplex ultrasound examinations confirmed graft patency until explant at 6 weeks. Differential light microscopy with computerized image analysis was performed on serial 5-microm sections. Intimal thickness through the venous anastomosis and outflow veins of Taylor patch and control (nonpatched) grafts were compared. Cell type-specific immunocytochemical antibody stains for smooth muscle cells (alpha SMC actin) and endothelial cells (von Willebrand factor) were performed. RESULTS: Eleven of 12 grafts remained patent for 6 weeks, 1 control graft thrombosed. Mean duplex-derived peak systolic velocities of patched (96 cm/sec) and control (108 cm/sec) grafts were similar. Microscopy revealed more intimal pannus anastomotic suture line ingrowth in controls (mean thickness = 178 microm) than Taylor patched grafts (mean 147 microm, p = 0.0002). Significantly less intimal thickening was present in the outflow vein of patched (mean thickness = 90 microm) versus control grafts (mean 195 microm, P <0.0001). The intima maintained a single cell layer of vWF + endothelial cells, while the majority of the cells comprising the lesion expressed alpha SMC actin. CONCLUSION: Perianastomotic pannus is primarily composed of intimal smooth muscle cells. Neointimal thickening is significantly reduced in prosthetic arteriovenous fistulae created with the Taylor vein patch in a canine model. Reduction in perianastomotic intimal thickening may explain the reported clinical improvement in prosthetic bypass graft patency when modified with vein patch techniques.     

Pathological study of implanted dacron grafts in surgery of thoracic aortic aneurysms

We studied woven dacron grafts that had been implanted in 5 patients of thoracic aortic aneurysms. In addition to usual stains, immunocytochemical analysis was performed using monoclonal antibodies to the muscle actin (HHF35) and to the macrophage (HAM56). In the graft of 5 and 24 days implantation, thin thrombi containing red cells and fibrin covered the luminal surface in some places, and macrophages came into the thrombi. In the grafts of 12 and 38 months implantation, intimal hyperplasia of 0.2-1.0 mm thickness was seen at the anastomotic segments with the accumulation of smooth muscle cells. Except for the anastomotic segments, connective tissue matrix with collagen fibers covered the luminal surface, and in some hollows of the graft crimps, old and fresh thombi were seen in layers. Organizing thrombi of 1.0 mm thickness attached where the branched graft was anastomosed to the main graft. Anastomotic intimal hyperplasia in the graft of 148 month implantation was 0.4-1.0 mm in thickness and 5-10 mm in length, and aside from the intimal hyperplasia, an endothelial lining did not cover the luminal surface of the graft. In the thoracic aorta, woven dacron graft implantation did not cause a critical stenosis with the intimal hyperplasia. The mural thrombi formed at the branched graft, however, threatened to result in graft occlusion or embolization.     

Histological and morphometric analyses of early and late aortocoronary vein grafts and distal anastomoses

BACKGROUND: Aortocoronary vein grafts develop fibromuscular intimal hyperplasia within the first year of implantation. Tissue remodeling may promote development of graft atherosclerosis and thrombosis. Angiographic studies show that human aortocoronary vein grafts in situ for one or more years become stenosed, preferentially at the distal anastomosis versus the body or trunk of the graft or at the proximal anastomosis. Previous studies have not reported morphological data on the nature and distribution of intimal lesions around the distal graft/artery anastomoses. OBJECTIVE: To examine and quantify histological and morphometric changes within the intima of 27 aortocoronary vein grafts and their distal anastomoses. METHODS: Seventy-two hearts obtained at autopsy and one at heart transplantation were examined, photographed and fixed in 10% buffered formaldehyde solution. Three to seven 3 mm long segments of grafts and their distal anastomoses were sectioned, stained and examined by light microscopy. RESULTS: Eleven early grafts were implanted for six weeks or less, and they showed significant cellular hyperplasia mainly at the suture line. In 16 late grafts in situ 1.5 to 15 years, the degree of fibromuscular intimal thickening was greatest on the hood and at the suture line, whereas on the floor of the native artery and in the graft body the degree of thickening was approximately one-third and two-thirds, respectively, that seen on the hood. CONCLUSIONS: Stenosis of aortocoronary vein grafts at their distal anastomosis is likely related to the preferential development of intimal thickening on the hood of the graft and at the suture line. Because fibromuscular intimal hyperplasia has been reported to play a role in the development of atherosclerosis and thrombosis in the body of vein grafts, this focal hyperplasia at the distal anastomosis may also play a role in vein graft failure.     

Luminal foam cell accumulation is associated with smooth muscle cell death in the intimal thickening of human saphenous vein grafts

BACKGROUND: Occlusion of saphenous vein grafts is a major problem after coronary artery bypass graft surgery. Diffuse intimal thickening develops in all implanted aortocoronary saphenous vein grafts within 6 months to 1 year. In some regions of the thickened intima, foam cells accumulate along the luminal margin. This particular morphology resembles the morphology of unstable atherosclerotic plaques as they occur in coronary arteries. In the present study, we focused on the possible topographic relation between luminal foam cell accumulation and cell death of smooth muscle cells (SMCs) within the adjacent thickened intima. METHODS AND RESULTS: Segments of occluded and suboccluded implanted human aortocoronary saphenous vein grafts were obtained during reintervention coronary artery bypass graft surgery in 30 patients. In the regions of the vein grafts with luminal foam cell accumulation, the percentage of SMC alpha-actin immunoreactive area of the superficial intimal thickening was 6 +/- 1.4%, which was different from the 17.6 +/- 2.3% of the deep intimal thickening. A strong negative correlation between the number of foam cell nuclei and the percentage of SMC alpha-actin immunoreactive area in the adjacent superficial intimal thickening was present (r = -.77, P < .001). Within the superficial intimal thickening, cytoplasmic and DNA fragmentation could be detected, which points to apoptotic cell death. A fraction of the cytoplasmic fragments fitted the ultrastructural characteristics of matrix vesicles and showed pronounced calcium and phosphorus accumulation as demonstrated with the use of x-ray microanalysis. CONCLUSIONS: The close spatial relation among foam cell accumulation, pronounced intimal SMC loss, and cell death suggests the presence of a foam cell-derived factor that can induce cell death in the SMC population of the intimal thickening. The depletion of the intimal SMC population could promote plaque rupture and thrombotic complications in the grafts.     

Constitutive nitric oxide synthase is expressed and nitric oxide-mediated relaxation is preserved in retrieved human aortocoronary vein grafts

Although little is known about the endothelial cell function of human saphenous vein coronary artery bypass grafts, there is evidence to suggest that receptor-activated, endothelial-dependent relaxation mediated by nitric oxide is impaired. This study examines the expression and function of endothelial cell constitutive nitric oxide synthase (cNOS) of aortocoronary vein bypass grafts and human saphenous veins obtained from 10 patients undergoing repeat coronary artery bypass grafting for recurrent ischemic symptoms. Following precontraction with norepinephrine (10(-5) M), responses to acetylcholine (receptor-mediated, endothelium-dependent), calcium ionophore (A23187; receptor-independent, endothelium-dependent), and sodium nitroprusside (endothelium-independent) were assessed. Following total RNA extraction using phenol/guanidinium isothiocyanate from specimens of human saphenous vein and vein graft, a quantitative RNase Protection Assay (RPA) was performed using a cRNA riboprobe corresponding to a fragment of the human endothelial cell cNOS gene. Histologically, the vein grafts showed both intimal hyperplasia development and focal atherosclerosis formation compared to the saphenous veins. Scanning electron microscopy of the saphenous veins and the vein grafts showed an intact endothelium. Precontracted vein grafts did not relax in response to acetylcholine; in contrast, the saphenous vein relaxed in a dose-dependent manner to reach a maximal relaxation of 19 +/- 4% precontracted tension. Saphenous veins and vein grafts relaxed in response to A23187 with maximal relaxation of 92 +/- 5 and 73 +/- 13%, respectively. Both vessels relaxed in a dose dependent manner to sodium nitroprusside. RPA normalized to beta-actin showed similar levels of expression of endothelial cell cNOS equivalent to 1 pg of sense RNA in both the saphenous vein and vein graft.(ABSTRACT TRUNCATED AT 250 WORDS)     

New insights for dinucleotide backbone binding in conserved C5''-H . . . O hydrogen bonds

OBJECTIVE: Although a number of pharmacologic agents have been shown to reduce intimal hyperplasia in animal models of restenosis, to date no systemic agent has conclusively been shown to be effective in humans. Recently, considerable attention has been directed towards endothelin (ET), a potent vasoconstrictor and a powerful mitogen for vascular smooth muscle cells, as a mediator of intimal hyperplasia. Endothelin-1 has been shown to be mitogenic for human saphenous vein smooth muscle cells, and expression also is elevated in human vein graft stenosis. The aim of this study was the investigation of whether ET receptor antagonists can attenuate neointima formation in a laboratory model of vein graft intimal hyperplasia and the determination of whether the effects are mediated by a specific ET receptor subtype. METHODS: We used an organ culture of human saphenous vein, a well-validated model of vein graft intimal hyperplasia. Paired segments of human long saphenous vein were cultured with and without the following antagonists: bosentan, a nonselective ET receptor antagonist; BQ 123, a specific endothelin-A antagonist; or BQ 788, a specific endothelin-B (ETB) antagonist. After 14 days in the culture, the segments were fixed and processed and the sections were immunostained to facilitate the measurements of neointimal thickness with a computerized image analysis system. RESULTS: The nonselective antagonist bosentan and the ETB selective antagonist BQ 788 significantly reduced neointima formation by 70% (P = .001) and 50% (P = .03), respectively, but the ETA antagonist BQ 123 had no significant effect on the reduction of neointima formation (P = 1.0). CONCLUSION: The results of this study imply an important role for ET as a mediator of human vein graft intimal hyperplasia and imply further that a specific ETB antagonist may have a therapeutic potential for the prevention of vein graft stenosis.     

Levo-Alpha Acetyl Methadol (LAAM). Its advantages and drawbacks

Although the histologic effects of balloon catheter thromboembolectomy in arteries are well described, little is known about its effects on arterialized vein grafts. A chronic canine model was used to compare the intimal hyperplasia that develops following balloon catheter thrombectomy versus thrombolytic therapy when each treatment was used to open experimentally occluded reversed autogenous vein grafts. Eleven of 12 dogs survived to the time of graft thrombosis and treatment. Ten grafts in one group of animals were treated with shear force-controlled balloon catheter thrombectomy, and eleven grafts in another group of animals were treated with infusion of urokinase (average 355, 833 IU/graft). Explantation and histologic evaluation was performed 5 weeks after treatment. Data were evaluated at comparable anatomic locations. These studies demonstrated the development of intimal hyperplasia in both groups with no statistically significant differences in the intimal thickening between the two treatment groups. It is hypothesized that vessel wall damage occurs at the time of thrombosis with the adherence of thrombus to the wall, and that this may be as important in producing intimal hyperplasia as the effects of carefully performed balloon thrombectomy or lytic therapy.     

The direct effect of graft compliance mismatch per se on development of host arterial intimal hyperplasia at the anastomotic interface

To study the direct and sole effect of compliance mismatch on anastomotic intimal hyperplasia of the host arterial wall and to minimize possible confounding factors, dogs with a low thrombotic potential were selected as experimental subjects. Externally supported 6 cm x 5 mm Dacron grafts with a compliance value of approximately 1/300 of the host artery were implanted into the carotid arteries with end-to-end anastomoses on one side and end-to-side anastomoses on the other. The control graft was an autogenous carotid artery segment 4 cm in length transplanted into the femoral artery. Eight cases (24 grafts) were studied for 1 year and three (nine grafts) for 6 months. All were patent throughout the study period except for two noncompliant grafts with end-to-end anastomoses; thrombosis was the documented cause of occlusion. For the patent grafts, follow-up arteriograms showed no progressive narrowing of noncompliant anastomoses. Whether compliant or noncompliant, light microscopy studies showed slight intimal thickening within 1 to 2 mm of the anastomotic line, possibly the result of the normal healing response to stitch and surgical trauma. Quantitatively, 22 measurements representing longitudinal and circumferential thickness of the neointima were taken at each of the 40 patent noncompliant and 22 patent compliant control anastomoses. There was no statistically significant difference in anastomotic neointimal thickness in compliant and noncompliant grafts or for the different implantation periods. These data suggest that graft/host artery compliance mismatch does not cause arterial intimal hyperplasia at the anastomotic interface.     

Specific activity of polypyrrole nanoparticulate immunoreagents: comparison of surface chemistry and immobilization options

PURPOSE: Angioscopy for in situ vein graft preparation has been criticized on the basis that the trauma of instrumentation may predispose to accelerated intimal hyperplasia, jeopardizing patency rates following infrainguinal revascularization. The aim of this study was to assess the effects of angioscopic preparation on endothelial integrity and smooth muscle cell (SMC) behavior in an established organ culture model of human saphenous vein (HSV). METHODS: HSV was harvested from 12 patients during bypass surgery before and after angioscopic preparation. Endothelial integrity was evaluated by immunohistochemical staining with JC-70 and scanning electron microscopy (SEM); remaining segments of pre- and postangioscopy vein were maintained in culture for 14 days in medium supplemented with 30% fetal calf serum. Viability was confirmed by measurement of tissue adenosine triphosphate on day 14 and thickness of the neointima was measured by computerized image analysis of histologic sections. Monoclonal antibodies to proliferating cell nuclear antigen (PCNA) were used as an immunohistochemical marker for proliferating SMCs. RESULTS: There was a significant reduction in the percentage staining by JC-70 (71.3% versus 20.4%) in pre- versus postangioscopy vein (p = 0.002 by Wilcoxon's rank test; n = 12). This was supported by SEM images. Despite this, there were no significant differences between the pre- and postangioscopy HSVs after 14 days of culture with respect to neointimal thickness (61 versus 56 microns) and staining with PCNA (4.80 versus 4.08 nuclei per 10 microns), all according to Wilcoxon's rank test. CONCLUSIONS: Angioscopic vein graft preparation is associated with endothelial cell loss but does not induce additional neointimal hyperplasia in HSV in vitro. These results suggest that angioscopic manipulation does not alter SMC behavior.     

The effect of oestrogen on intimal hyperplasia in cultured human ovarian veins

The beneficial effect of oestrogen on blood vessels may include modulation of vascular response to injury. In this experiment we set out to develop an in-vitro model, using all human materials, for the study of vascular changes in culture, and their response to oestrogen treatment. Human ovarian vein segments were obtained from 15 hysterectomy specimens, and cultured with and without the addition of 17beta-oestradiol. Paired control veins were cultured with the inert 17alpha-oestradiol. The veins were stained with anti-alpha-smooth muscle actin and Miller's elastin, and intimal thickness measured. Cultured veins developed a significant degree of intimal thickening [15.7 versus 8.25 microm in fresh veins, 95% confidence intervals (CI) 13.6, 17.8 and 6.3, 10.2 respectively; P = 0.0001]. The addition of 17beta-oestradiol, but not 17alpha-oestradiol, led to a significant reduction in intimal hyperplasia (intimal thickness 8.85 microm; 95% CI 6.9, 10.8; P = 0.008). The mean number of nuclei per high-power field was also significantly lower in the intima of oestrogen-treated compared to untreated veins (11.6; 95% CI 9.9, 13.26 versus 14.05; 95% CI 12.5, 15.6; P = 0.001). Our data suggest that intimal hyperplasia in cultured ovarian veins is effectively reduced by oestrogen.     

Mouse model of venous bypass graft arteriosclerosis

Saphenous vein grafts are widely used for treatment of severe atherosclerosis via aortocoronary bypass surgery, a procedure often complicated by later occlusion of the graft vessel. Because the molecular mechanisms of this process remain largely unknown, quantitative models of venous bypass graft arteriosclerosis in transgenic mice could be useful to study this process at the genetic level. We describe herein a new model of vein grafts in the mouse that allows us to take advantage of transgenic, knockout, or mutant animals. Autologous or isogeneic vessels of the external jugular or vena cava veins were end-to-end grafted into carotid arteries of C57BL/6J mice. Vessel wall thickening was observed as early as 1 week after surgery and progressed to 4-, 10-, 15-, and 18-fold original thickness in grafted veins at age 2, 4, 8, and 16 weeks, respectively. The lumen of grafted veins was significantly narrowed because of neointima hyperplasia. Histological and immunohistochemical analyses revealed three lesion processes: marked loss of smooth muscle cells in vein segments 1 and 2 weeks after grafting, massive infiltration of mononuclear cells (CD11b/18+) in the vessel wall between 2 and 4 weeks, and a significant proliferation of vascular smooth muscle cells (alpha-actin+) to constitute neointimal lesions between 4 and 16 weeks. Similar vein graft lesions were obtained when external jugular veins or vena cava were isografted into carotid arteries of C57BL/6J mice. Moreover, no significant intima hyperplasia in vein-to-vein isografts was found, although there was leukocyte infiltration in the vessel wall. Thus, this model, which reproduces many of the features of human vein graft arteriosclerosis, should prove useful for our understanding of the mechanism of vein graft disease and to evaluate the effects of drugs and gene therapy on vascular diseases.     

Chronic in vitro shear stress stimulates endothelial cell retention on prosthetic vascular grafts and reduces subsequent in vivo neointimal thickness

OBJECTIVE: The absence of endothelial cells at the luminal surface of a prosthetic vascular graft potentiates thrombosis and neointimal hyperplasia, which are common causes of graft failure in humans. This study tested the hypothesis that pretreatment with chronic in vitro shear stress enhances subsequent endothelial cell retention on vascular grafts implanted in vivo. METHODS: Cultured endothelial cells derived from Fischer 344 rat aorta were seeded onto the luminal surface of 1.5-mm internal diameter polyurethane vascular grafts. The seeded grafts were treated for 3 days with 1 dyne/cm2 shear stress and then for an additional 3 days with 1 or 25 dyne/cm2 shear stress in vitro. The grafts then were implanted as aortic interposition grafts into syngeneic rats in vivo. Grafts that were similarly seeded with endothelial cells but not treated with shear stress and grafts that were not seeded with endothelial cells served as controls. The surgical hemostasis time was monitored. Endothelial cell identity, density, and graft patency rate were evaluated 24 hours after implantation. Endothelial cell identity in vivo was confirmed with cells transduced in vitro with beta-galactosidase complementary DNA in a replication-deficient adenoviral vector. Histologic, scanning electron microscopic, and immunohistochemical analyses were performed 1 week and 3 months after implantation to establish cell identity and to measure neointimal thickness. RESULTS: The pretreatment with 25 dyne/cm2 but not with 0 or 1 dyne/cm2 shear stress resulted in the retention of fully confluent endothelial cell monolayers on the grafts 24 hours after implantation in vivo. Retention of seeded endothelial cells was confirmed by the observation that beta-galactosidase transduced cells were retained as a monolayer 24 hours after implantation in vivo. In the grafts with adherent endothelial cells that were pretreated with shear stress, immediate graft thrombosis was inhibited and surgical hemostasis time was significantly prolonged. Confluent intimal endothelial cell monolayers also were present 1 week and 3 months after implantation. However, 1 week after implantation, macrophage infiltration was observed beneath the luminal cell monolayer. Three months after the implantation in vivo, subendothelial neointimal cells that contained alpha-smooth muscle actin were present. The thickness of this neointima averaged 41 +/- 12 micrometer and 60 +/- 23 micrometer in endothelial cell-seeded grafts that were pretreated with 25 dyne/cm2 shear stress and 1 dyne/cm2 shear stress, respectively, and 158 +/- 46 micrometer in grafts that were not seeded with endothelial cells. CONCLUSION: The effect of chronic shear stress on the enhancement of endothelial cell retention in vitro can be exploited to fully endothelialize synthetic vascular grafts, which reduces immediate in vivo graft thrombosis and subsequent neointimal thickness.     

Ultrasonographic evaluation of the anterior recess in the normal hip: a prospective study on 166 asymptomatic children

Bypass graft patency with ultrafast computed tomography (= Electron Beam Tomography, EBT) was examined in 72 bypass grafts (47 saphenous veins, 25 internal mammary arteries) in 30 patients and compared with coronary angiography. Angiography was performed a mean of 4.4 +/- 3.5 months (range 1-13) from the EBT examination. Contrast material (120 ml) was continuously administered via a peripheral vein and 40 axial slices (3 mm slice thickness, 110 ms scan time) without overlap sequences were obtained, ECG triggered with the single slice scanner mode. Imaging of internal mammary artery grafts began at the thoracic inlet, for saphenous vein grafts, at the undersurface of the aorta. Sixty of 63 angiographically patent bypass grafts were determined patent by EBT (sensitivity 95%), 8 bypass grafts could not be detected by EBT, and 9 were angiographically occluded (specificity 89%). Twenty-four of 25 internal mammary artery grafts were patent at EBT and coronary angiography, one was occluded. In 27 of the 30 patients (90%), all of the angiographically patent grafts could be confirmed as open with EBT. Obstructions of 10 grafts could not be visualized with EBT. Graft insertion into native coronary vessels could be visualized in axial slices, although morphologic quantification of graft insertion stenosis (75-90%) in two cases was not possible. Three dimensional reconstruction of the 40 axial slices allowed graft anatomy to be delineated. Visualization of bypass insertion into the native coronary vessel was less successful because of opacification of the left and right ventricle. Electron beam computed tomography is a minimally invasive procedure capable of evaluating the patency of saphenous vein and internal mammary artery grafts. The morphologic quantification of graft obstruction and visualization of the insertion of the bypasses into the native coronary vessels is less successful with present technology and imaging modalities.     

Donor age and graft function

We evaluated survival and renal function of cadaveric donor grafts according to donor age. The median age of the pediatric donors was 7.0 (0.7-16) years in 46 patients [median age 11.8 years (range) 3-16.8 years]. The median age of the adult donors was 34.4 (19-54) years in 59 patients [median age 12.1 years (range) 7-17.3 years]. Thirty patients were treated with azathioprine and prednisolone and 75 with cyclosporine A and prednisolone. The glomerular filtration rate (GFR) and the effective renal plasma flow (ERPF) were determined by the clearances of 51chromium-EDTA and 125iodine-hippurate 1-48 months after kidney transplantation. There was no difference in graft survival between pediatric and adult grafts. There were also no differences in GFR in patients receiving grafts from pediatric or adult donors; 2-3 months after transplantation the GFR in recipients of pediatric grafts was 62 +/- 20 ml/min per 1.73 m2 compared with 61 +/- 21 in those receiving adult grafts. The ERPF in recipients of adult grafts was significantly higher in the 1st month after transplantation: 486 +/- 239 versus 362 +/- 158 ml/min per 1.73 m2. From the 4th to the 6th month after transplantation this difference disappeared: the ERPF of grafts from pediatric donors was 279 +/- 131 ml/min per 1.73 m2 compared with 273 +/- 123 ml/min per 1.73 m2 in grafts from adult donors. Using the single-kidney GFR and ERPF on an age-matched group of probands with minor diseases as references, 2-3 months after transplant the mean GFR of grafts from pediatric donors increased to 118% +/- 51%, whereas the GFR of adult donor grafts fell to 60% +/- 22% over the same period. After 4-6 months the ERPF in pediatric grafts was 96% +/- 55% compared with 50% +/- 22% in adult grafts. We conclude that graft survival and function in children with either a pediatric or an adult graft may not differ because graft function adapts to the requirement of the recipient.     

Preferred strategies for secondary infrainguinal bypass: lessons learned from 300 consecutive reoperations

PURPOSE: To determine the optimal surgical strategies in reoperative infrainguinal bypass, we reviewed our results in 300 consecutive secondary bypasses in 251 patients operated on between Jan. 1, 1975, and Nov. 1, 1993. METHODS: There were 168 men (67%) and 83 women (33%), with a mean age of 64.8 years and a typical distribution of risk factors including smoking (76.4%), diabetes (33.7%), and coronary artery disease (47.1%). The indications for surgery were limb-threatening ischemia in 83.5% and severe claudication in 16.5% of patients. The majority of conduits (n = 213) were autogenous vein and were composed of a single segment of greater saphenous vein in 121 bypasses (57%) and various alternative veins including composite, arm, and lesser saphenous vein in 92 bypasses (43%). Prosthetic conduits included 69 polytetrafluoroethylene, 16 umbilical vein, and two Dacron grafts. RESULTS: There was one perioperative death (0.3%) and a 25% total morbidity rate including a 1.7% myocardial infarction rate. There was a 28.6% early (< 30 days) graft failure and 10.7% early amputation rate for prosthetic bypass grafts compared with 13.6% early graft failure and 5.6% early amputation rates for vein grafts. Autogenous vein bypasses had higher 5-year secondary patency rates than had prosthetic grafts (51.5% +/- 4.6% vs 27.4% +/- 6.1%, p < 0.001). Results with autogenous vein bypass improved significantly from the 1975 to 1984 to the 1985 to 1993 interval with 5-year secondary patency rates increasing from 38.3% +/- 6.9% to 59.1% +/- 5.8% (p = 0.017) and 5-year limb-salvage rates increasing from 40.4% +/- 7.6% to 72.4% +/- 6.6% (p < 0.001). Vein grafts to the popliteal and tibial outflow levels had equivalent long-term results. Vein grafts completed for claudication demonstrated results superior to those for limb salvage, with a 5-year secondary patency rate of 75.8% +/- 8.1% versus 52.3% +/- 7.9% (p = 0.048). Secondary autogenous vein bypass grafting performed after early primary graft failure (< 3 months) did particularly poorly, with only a 27.2% +/- 7.7% 4-year secondary patency rate. Greater saphenous veins tended to perform better than alternative vein bypasses, with a 5-year secondary patency rate of 68.5% +/- 6.0% compared with 48.3% +/- 10.5% (p = 0.09) and a 5-year limb-salvage rate of 77.8% +/- 7.4% versus 54.2% +/- 11.8% (p = 0.046). CONCLUSIONS: When patients suffer a recurrence of limb-threatening ischemia at the time of infrainguinal graft failure, aggressive attempts at secondary revascularization with autogenous vein are warranted based on the low surgical morbidity and mortality rates and the improved patency and limb salvage rates that are currently attainable.     

Oropharyngeal synovial sarcoma. Report of one case]

OBJECTIVE: To assess the prognostic factors of myocardial recovery expected after coronary bypass surgery and the impact of surgical technique used, a prospective non-randomized study including a 1-year postoperative evaluation of left ventricular function was performed in patients with left ventricular dysfunction (left ventricular ejection fraction (LVEF) < 0.40). METHODS: From 1993 to 1996, 110 patients (mean age 61+/-11 years) were included in the study. The mean LVEF was 31+/-6%. All patients had preoperative radionuclide investigations based on the combination of stress/reinjection thallium single photon emission computed tomography (SPECT) and planar evaluation of LVEF; 88% of patients had reversible ischemic thallium defects. Two surgical technique were used: 53 patients received the left internal mammary artery with associated sequential vein graft, and 57 patients received only arterial grafts, internal mammary and gastroepiploic arteries. The mean number of distal anastomoses was 3.2+/-0.8 and 54% of patients had complete revascularization. At 1 year, all survivors had clinical evaluation and the same radionuclide investigations. RESULTS: The early mortality was 2.7%. At 1 year, 100 patients were surviving; on average, NYHA class decreased 1.9+/-0.8 to 1.4+/-0.6 (P < 0.01) and CCS class from 2.8+/-0.6 to 1+/-0.3 (P < 0.01). The mean LVEF increase from 31+/-9 to 34+/-10% (P < 0.01) and the mean LV end-diastolic volume decreased from 317+/-112 to 285+/-108 ml (n.s.). The postoperative improvement in LV function was higher in patients in NYHA class 3 or 4 before surgery (P < 0.05), when associated sequential vein graft had been used (P < 0.01), and in patients with low preoperative LVEF (P < 0.01). The postoperative LVEF improvement observed was significantly correlated with the improvement in left ventricular end-diastolic (LVED) volume and the improvement in redistribution/reinjection thallium uptake. Multivariate analysis showed that the surgical technique used and the preoperative LVEF were independent prognostic factors of the postoperative myocardial function recovery, with a significant positive impact of the vein use. CONCLUSION: This study confirms the excellent clinical results of coronary artery bypass grafting (CABG) in patients with coronary artery disease and LV dysfunction; improvement in LV function can be documented objectively and is correlated with reperfusion of hibernating myocardium. However, the extended use of arterial grafts does not allow to achieve the significant myocardial recovery observed with the use of one internal mammary artery (IMA) and associated sequential vein graft; it seems to be related to the preoperative selection of patients, but a direct negative impact of arterial grafts was documented and leads to be cautious in patients with severe LV dysfunction.     

The application of intervertebral implant for spine stabilization]

BACKGROUND: To prevent ischemic complications during coronary bypass grafting on the beating heart, a nonocclusive distal anastomosis technique is needed. One recently developed nonocclusive technique requires apposition of the intima of the graft to the adventitia of the recipient artery, in contrast to current surgical practice, which dictates apposition of both intimas. METHODS: To compare the sole effect of intima-adventitia apposition (n = 18) versus traditional intima-intima apposition (n = 18), we investigated radiolabeled platelet deposition and histomorphologic aspects of vascular wall healing quantitatively in a porcine carotid artery bypass graft model. Both groups were evaluated at 2 hours, 2 days, or 4 weeks. RESULTS: Within the first 2 hours, 3 of 6 pigs with intima-adventitia apposition exhibited cyclic flow reductions as a result of massive mural thrombosis. After intima-adventitia apposition, the number of deposited platelets was significantly higher compared with intima-intima apposition, 147.1 +/- 73.0 x 10(6) and 4.6 +/- 1.0 x 10(6) platelets/cm2 (mean +/- standard error of the mean), respectively (p = 0.03). At 2 days, the suture line was covered with small mural thrombi, whereas no thrombi were found after intima-intima apposition. At 4 weeks, intimal hyperplasia at heel and toe was not significantly different from that with intima-intima apposition. CONCLUSIONS: Despite thrombotic phenomena in the early phase, intima-adventitia apposition yielded a patent anastomosis with a small intimal hyperplasia response.     

Frequency dependent force generation correlates with sarcoplasmic calcium ATPase activity in human myocardium

The purpose of this study was to implement and evaluate a clinical protocol for following longitudinally the luminal responses of microvessel cell seeded expanded polytetrafluoroethylene (ePTFE) vascular grafts implanted for hemodialysis access. Half of the patients enrolled in the study were randomized to receive grafts that were "seeded" with transplanted microvessel cells derived from autologous subcutaneous fat; the other half of the patients received nonseeded grafts. The patients agreed to scheduled biopsies of their grafts at three postoperative times. All biopsy samples were evaluated by routine histologic and electron microscopy techniques. Three men and six women were enrolled in the study. All operative procedures were tolerated well. However, only two of the nine patients agreed to 1-year postimplantation biopsies; one of these patients had been randomized to receive a "nonseeded" ePTFE graft and one randomized to receive a "seeded" graft. The "seeded" graft at 3 months showed endothelial cells on the luminal surface as well as some intimal thickening. By 20 months, the same "seeded" graft showed significant concentric intimal thickening and by 24 months, this "seeded" graft thrombosed. The "nonseeded" graft at 16 months had irregular areas of intimal thickening which were quite patchy in nature. The flow contacting surface of the "nonseeded" graft remained thin. The intima of the "seeded" graft was twice as thick as that of the "nonseeded" graft. The methodologies implemented in the study design were appropriate. Biopsy samples were obtained without complication and were easily processed for analysis. Patient compliance with the biopsy protocol was problematic however. The study was terminated because of the development of significant concentric intimal hyperplasia in a "seeded" graft.     

Intestinal epithelial cell regulation of macrophage and lymphocyte interleukin 10 expression

Patients with recurrent angina after coronary artery bypass graft surgery pose a problem. Stent implantation has been advocated in an effort to avoid repeat operation and to address the limitations of balloon angioplasty. Aim of the present study was to determine the in-hospital and long-term results of stent deployment in focal, de novo lesions of vein grafts. Thirty-five focal, de novo lesions of vein grafts in 31 patients were treated with stent deployment. Twenty-four patients (77%) had three vessels, 6 (20%) two vessels and 1 (3%) single vessel disease. Saphenous vein grafts aged 9.7 +/- 4.2 years (range 1-19 years). Twenty-two lesions (63%) were located within the body of the saphenous graft, 8 (23%) at the graft/coronary artery anastomosis and 5 (14%) at the aorta/graft anastomosis. The indications for stent deployment included: suboptimal result from balloon angioplasty (defined as > or = 50% post-angioplasty residual stenosis) in 29/35 lesions (83%); post-angioplasty coronary dissection with threatening occlusion in 4/35 (11%); abrupt closure in 2/35 (6%). Patients were screened for death, myocardial infarction, bypass surgery and repeat angioplasty during in-hospital stay and after a follow-up of 12 +/- 8 months. Even-free survival curve was constructed by the Kaplan-Meier method. Stent deployment was successful in all patients. One stent was deployed in 24/35 lesions (69%), half Palmaz-Schatz stent in 6/35 (17%) and 2 or more stents in 5/35 (14%). The balloon/vessel ratio resulted of 1.0 +/- 0.1 Minimal lumen diameter increased from 0.8 +/- 0.4 to 3.8 +/- 0.6 mm, with a mean gain of 1.8 +/- 0.6 mm (range 1.8-4.0 mm). During the in-hospital period 1 patient (3.2%) died and 1 (3.2%) had a non Q wave myocardial infarction. Therefore, the clinical success rate, was 94%. During the follow-up period, 2 patients died (6.9%), 2 (6.9%) developed a non Q wave myocardial infarction, 1 (3.4%) underwent bypass surgery and 3 (10.3%) underwent repeat angioplasty. The estimated 2-year event-free survival rate (free from myocardial infarction, repeat surgery and repeat angioplasty) was 62%. In conclusion, Palmaz-Schatz stent deployment in focal, de novo vein grafts presents a high rate of procedural success, a low rate of acute complications and good long-term results.