Biomedical subjects

F W LoGerfo

Publications and source records attributed to F W LoGerfo.

At least 37 records · Page 2Linked to original sources

PubMed1999

Soluble intercellular adhesion molecule, vascular cell adhesion molecule, and impaired microvascular reactivity are early markers of vasculopathy in type 2 diabetic individuals without microalbuminuria.

OBJECTIVE: Using von Willebrand Factor (vWF) as a marker of endothelial function, previous studies have shown that the development of microalbuminuria is associated with the onset of endothelial dysfunction in individuals with type 2 diabetes. We tested the hypothesis that endothelial dysfunction is already evident in normoalbuminuric individuals with type 2 diabetes. RESEARCH DESIGN AND METHODS: We used laser Doppler imaging scanning to measure vasodilation in the forearm skin in response to iontophoresis of 1% acetylcholine (endothelium-dependent) and 1% sodium nitroprusside (endothelium-independent). Multiple indicators of endothelial function--soluble intercellular adhesion molecule (sICAM), soluble vascular cell adhesion molecule (sVCAM), vWF, and microvascular reactivity--were measured in 20 healthy control subjects, 45 normoalbuminuric (urinary albumin/creatinine ratio < 30 micrograms/mg) individuals with type 2 diabetes, and 14 microalbuminuric (urinary albumin/creatinine ratio between 30 and 300 micrograms/mg) individuals with type 2 diabetes. RESULTS: Serum sICAM and sVCAM levels were elevated in the normoalbuminuric (305 +/- 120, 851 +/- 284 ng/ml) and microalbuminuric (300 +/- 89, 845 +/- 252 ng/ml) individuals with diabetes when compared with the healthy control subjects (213 +/- 58, 661 +/- 176 ng/ml) (P < 0.01). Furthermore, the microvascular endothelium-dependent and -independent vasodilation was reduced in the normoalbuminuric (76 +/- 44, 70 +/- 33) (percent increase in perfusion over baseline) and microalbuminuric (74 +/- 41, 73 +/- 28) individuals with diabetes compared with healthy control subjects (126 +/- 67, 120 +/- 47) (P < 0.05). In contrast, plasma vWF was elevated only in the microalbuminuric individuals with diabetes (129 +/- 35%) compared with the normoalbuminuric individuals with diabetes (110 +/- 34) and healthy control subjects (111.3 +/- 39) (P < 0.05). On stepwise multivariate analysis, fasting blood glucose was the most important contributing factor to the variation in microvascular reactivity and sVCAM, whereas insulin resistance (by homeostasis model assessment) was the most important contributing factor to the variation in sICAM. Addition of all clinical and biochemical measures explained only 15-22% of the variation in sICAM, sVCAM, and microvascular reactivity. CONCLUSIONS: Multiple markers of endothelial dysfunction were evident in normoalbuminuric individuals with type 2 diabetes. The pathogenic process of vasculopathy in type 2 diabetes occurs early and may be operative before the development of microalbuminuria.

Adult↗

PubMed1998

Evaluation of a novel hirudin-coated polyester graft to physiologic flow conditions: hirudin bioavailability and thrombin uptake.

PURPOSE: Our laboratory has developed methods required to covalently bind recombinant hirudin (rHir) to the surface of polyester vascular grafts. Using alkaline hydrolysis of the polyester surface, carboxyl-binding sites are created on the outer periphery of each fiber. A series of static, in vitro experiments have demonstrated that surface-bound rHir rapidly removes and inhibits activated human alpha-thrombin from the reaction system; however, the performance of this modified graft material under physiologic flow conditions was undefined. METHODS: An in vitro flow loop was used to evaluate structural stability of the 125I-rHir and 131I-albumin covalently bound to the surface of 6 mm interior diameter crimped polyester grafts exposed to either constant flow (n = 4; shear rate, 300 sec(-1)) or pulsatile flow (n = 4; maximum shear rate, 780 sec(-1)) conditions for a 7-day period. In a separate series of experiments, the kinetics of thrombin-rHir interaction were evaluated through perfusion of 125I-rHir-coated grafts (n = 6) with 131I-thrombin for a 27-hour period under constant flow conditions. Identically prepared 125I-albumin-coated grafts (n = 3) were used as controls. RESULTS: Results of the stability experiments were independent of flow conditions, demonstrating moderate loss of both proteins, with rHir and albumin losses of 52.1% and 19.9% under constant flow and 49.1% and 21.6% under pulsatile flow, respectively. With results comparable with those of previous static experiments, rHir-coated grafts were significantly more effective at removing thrombin from the perfusion stream with 131I-thrombin binding densities of 3.08 +/- 0.61 and 0.64 +/- 0.04 NIHU/cm2 (p < 0.01) for rHir-coated and albumin-coated grafts, respectively. Estimates of the total amount of thrombin inactivated during the perfusion period similarly demonstrated a marked difference between the rHir-coated and control graft segments (125 +/- 8 vs. 3 +/- 14 NIHU; p < 0.005). CONCLUSIONS: These in vitro flow results illustrate that polyester grafts with covalently bound rHir can provide significant reductions in local thrombin concentration under physiologic flow conditions, and can serve as a foundation with which to understand the performance of these grafts when implanted in vivo under physiologic flow and shear rates.

Biocompatible Materials↗

PubMed1998

Estrogen improves endothelial function.

PURPOSE: To determine the effect of estrogen on endothelium-dependent relaxation in the cutaneous microcirculation of women. METHODS: Three groups of women participated in the study. Group 1 (n = 20) was premenopausal and had a mean age of 39 years (range 24-50 years). Group 2 (n = 9) was postmenopausal and had a mean age of 58 years (range 53-65 years). Group 3 (n = 11) was postmenopausal and taking estrogen replacement therapy; the mean age was 53 years (range 43-58 years). Eleven women in group 1 underwent testing twice, once during menstruation (mean serum estradiol level 73 +/- 30 pg/ml) and once during midcycle (mean serum estradiol level 268 +/- 193 pg/ml; p = 0.003). Single-point laser Doppler ultrasound and laser Doppler imaging with a scanner were used to measure vasodilatation in the forearm skin in response to iontophoresis of 1% acetylcholine (endothelium dependent) and 1% sodium nitroprusside (endothelium-independent smooth muscle relaxant). RESULTS: All three groups were matched for body mass index and fasting glucose, total, high-density lipoprotein, and low-density lipoprotein cholesterol and triglyceride levels. All women had normal blood pressure, and none smoked. Mean serum estradiol levels were 196 +/- 170 pg/ml (group 1), 35 +/- 12 pg/ml (group 2), and 107 +/- 78 pg/ml (group 3) (p = 0.004). Maximum microvascular vasodilatation (percentage increase over baseline) in response to acetylcholine was reduced in group 2 (93% +/- 43%) compared with group 1 (187% +/- 63%) and group 3 (142% +/- 56%) (p = 0.001). The response to sodium nitroprusside also was diminished in group 2 (73% +/- 27%) compared with group 1 (126% +/- 45%) and group 3 (100% +/- 32%) (p = 0.02). Within group 1 the acetylcholine response was higher during the midcycle phase (186% +/- 31%) compared with the menstrual phase (147% +/- 57%) (p < 0.05). The sodium nitroprusside response also was higher during the midcycle phase (144% +/- 31%) compared with the menstrual phase (94% +/- 41%) (p < 0.05) CONCLUSION: The results indicate that estrogens might enhance endothelium-dependent and endothelium-independent vasodilatation in the microcirculation of women.

Acetylcholine↗

PubMed1998

The impact of cardiac comorbidity after carotid endarterectomy.

PURPOSE: Myocardial infarction and other comorbidities contribute to complications after carotid endarterectomy (CEA). However, because the combined stroke and death rate after CEA is less than 5%, even relatively large series have small numbers of adverse events that preclude a detailed analysis of the association between the outcome and the patient factors, such as comorbidity and age. We sought to overcome this limitation by studying patients who underwent CEA in a large random sample of Medicare beneficiaries. METHODS: We used a database that contained a 20% random sample of all Medicare beneficiaries to identify patients who underwent CEA between the years 1988 to 1990 (n = 22,165), and we followed these cases until 1992. With multivariate logistic regression and Cox proportional hazards regression models, we examined the impact of age, race, gender, geographic location, hospital characteristics, and comorbidity, including acute myocardial infarction (AMI) and congestive heart failure (CHF), on the risk of stroke and death after CEA. RESULTS: AMI and CHF had the greatest negative impact on the long-term survival rates (adjusted hazard ratio [HR]: 2.40, P < .0001, and 2.85, P < .0001, respectively). Other variables with a significant impact on the long-term survival rates were an age of >80 years (HR, 2.16; P < .0001), an acute stroke (HR, 1.51; P < .0001), diabetes mellitus (DM; HR, 1.52; P < .0001), and male sex (HR, 1.32; P < .0001). In addition, AMI, CHF, DM, and advanced age were associated with an increased risk of perioperative stroke and death. CONCLUSION: Patients with AMI, CHF, DM, and an age of >80 years have diminished perioperative and long-term survival rates after CEA. These results may alter the risk/benefit analysis for such patients, especially those with asymptomatic disease.

Age Factors↗

PubMed1998

Endothelium-dependent vasodilatation is impaired in both microcirculation and macrocirculation during acute hyperglycemia.

PURPOSE: Endothelial dysfunction is associated with atheromatosis and is a common finding with diabetes. We have studied the effects of acute hyperglycemia on the endothelium-dependent vasodilatation of both the microcirculation and the macrocirculation of healthy subjects. Because of the presence of endothelial dysfunction with diabetes, we hypothesize that acute hyperglycemia causes impaired endothelial-dependent responses. METHODS: Twenty healthy subjects (15 men, 5 women) with a mean age of 32.3 years (range, 23 to 49 years) were examined during fasting conditions and at 1 hour after the ingestion of 75 g of glucose. The endothelium-dependent vasodilatation of the brachial artery, a conduit vessel, was evaluated with high-resolution ultrasound scan to measure the changes in the vessel diameter induced with reactive hyperemia. In the microcirculation, the endothelial function was assessed by measuring the changes in the erythrocyte flux after the acetylcholine iontophoresis. RESULTS: The brachial artery endothelium-dependent dilatation was greater during fasting as compared with the response after the glucose load was administered (11.7% [8.3 to 14.3] vs 4.2% [1.5 to 9.6]; P < .001; median, first, and third quartile). Both peak and average blood flow velocities during the hyperemic response were higher after the administration of the glucose load as compared with the fasting period (P < .05), but no changes were found in the blood flow volume. During fasting, microcirculatory endothelial-dependent vasodilatation was also significantly greater than the response after the administration of the glucose load (1293% [591 to 1856] vs 863% [385 to 1180]; P < .01). CONCLUSIONS: In healthy subjects, the ingestion of a glucose load impairs the endothelial-dependent vasodilation in both the microcirculation and the macrocirculation. Because impairment of endothelial responses is associated with the early changes of atherosclerosis, it is possible that prolonged hyperglycemia and endothelial dysfunction may lead to the early and accelerated atherosclerosis of diabetes. Further studies are necessary to examine the long-term effects of hyperglycemia.

Acute Disease↗

PubMed1998

Lower extremity arterial reconstruction in the very elderly: successful outcome preserves not only the limb but also residential status and ambulatory function.

PURPOSE: The purpose of this study was to evaluate our results with lower extremity arterial reconstruction (LEAR) in patients 80 years of age or older and to assess its impact on ambulatory function and residential status. METHODS: We performed a retrospective review of all patients 80 years of age or older undergoing LEAR at a single institution from January 1990 through December 1995. Preoperative information regarding residential status and ambulatory function was obtained from the hospital record and vascular registry. Telephone interviews with patients or next of kin were undertaken to provide information regarding postoperative residential status and ambulatory function. Residential status and level of ambulatory function were graded by a simple scoring system in which 1 indicates living independently, walking without assistance; 2 indicate living at home with family, walking with an ambulatory assistance device; 3 indicates an extended stay in a rehabilitation facility, using a wheelchair; and 4 indicates permanent nursing home, bedridden. Preoperative and postoperative scores for both residential status and ambulatory function were compared. Kaplan-Meier survival curves were generated for graft patency, limb salvage, and patient survival. RESULTS: Two hundred ninety-nine lower extremity bypass operations were performed in 262 patients 80 years of age or older (45% men, mean age 83.6 years, range 80 to 96 years). Sixty-seven percent of the patients had diabetes mellitus. Limb salvage was the indication for operation in 96%. The preoperative mean residential status and ambulatory function scores were 1.79+/-0.65 and 1.55+/-0.66, respectively. The perioperative mortality rate at 30 days was 2.3%. The median length of hospital stay decreased from 16 days in 1990 to 8 days in 1995 (range 4 to 145 days). Eighty-seven percent of grafts were performed with the autologous vein. The 5-year primary, assisted primary, and secondary graft patency rates for all grafts were 72%, 80%, and 87%, respectively. The limb salvage rate at 5 years was 92%. The patient survival rate at 5 years was 44%. The postoperative residential status and ambulatory function scores were 1.95+/-0.80 and 1.70+/-0.66, respectively. Overall scores remained the same or improved in 88% and 78% of patients, respectively. CONCLUSION: LEAR in octogenarians is safe, with graft patency and limb salvage rates comparable to those reported for younger patients. LEAR preserves the ability to ambulate and reside at home for most patients.

Activities of Daily Living↗

PubMed1998

Identification of multiple genes with altered expression at the distal anastomosis of healing polytetrafluoroethylene grafts.

PURPOSE: Anastomotic intimal hyperplasia remains a significant cause of delayed prosthetic arterial graft failure. Prior studies have identified several genes with altered expression within the hyperplastic region at the downstream polytetrafluoroethylene arterial anastomosis as compared with normal arteries. The purpose of the current study was to determine the sequence of early gene-related events at the distal anastomosis of an in vivo prosthetic arterial graft model. Messenger RNA (mRNA) differential display was used to screen for alterations in gene expression between anastomotic sites and control arterial segments. METHODS: Six carotid interposition 6-mm expanded polytetrafluoroethylene grafts were placed in mongrel dogs, with the intervening carotid artery segment serving as the baseline control. Five days after graft implantation, the distal anastomotic artery segments were harvested and total RNA was isolated from both the intervening normal arteries and anastomotic segments. Differential mRNA display was used to identify candidate complementary DNA (cDNA) clones with expression that differed in anastomotic segments as compared with normal intervening arteries. Northern blot analysis confirmed alteration of gene expression. The cDNA clones were sequenced, and gene databases were searched. Novel sequences were used as probes for screening human cDNA libraries. RESULTS: Approximately 7000 mRNA species were screened, and 26 candidate clones were obtained. Northern blot analysis showed altered gene expression in 10 (38%) of the clones, undetectable signals in 13 (50%), and nonregulation in 3 (12%). Seven clones with 92% homology at the nucleotide level to human alpha1 (III) procollagen gene and novel sequence were expressed only at the distal anastomosis. A clone representing apolipoprotein J and a novel sequence had increased expression at the distal anastomosis of 364% +/- 236% and 156% +/- 47%, respectively (mean percentage, control +/- standard deviation). CONCLUSIONS: These studies identified genes with expressions that increased or were exclusive to the distal anastomosis of healing prosthetic arterial grafts in an in vivo prosthetic arterial graft model. Type III collagen may contribute significantly to the composition of the extracellular matrix associated with intimal hyperplasia by increasing lesion volume. Apolipoprotein J, through its association with proteases, may modulate some of the matrix changes seen early after grafting.

Anastomosis, Surgical↗

PubMed1998

Covalent linkage of recombinant hirudin to a novel ionic poly(carbonate) urethane polymer with protein binding sites: determination of surface antithrombin activity.

Surface thrombus formation on implantable biomaterials such as polyurethane is a major concern when utilizing these materials in the clinical setting. Thrombin, which is responsible for thrombus formation and smooth muscle cell activation, has been the target of numerous surface modification strategies in an effort to prevent this phenomenon from occurring. The purpose of this study was to covalently immobilize the potent, specific antithrombin agent recombinant hirudin (rHir) onto a novel polyurethane polymer synthesized with carboxylic acid groups which served as protein attachment sites. The in vitro efficacy of thrombin inhibition by this novel biomaterial surface was then evaluated. Bovine serum albumin (BSA), which was selected as the basecoat protein, was reacted with sulfo-SMCC in a 1:50 molar ratio. This BSA-SMCC complex was then covalently linked to the carboxylated polyurethane (cPU) surface via the crosslinker EDU (cPU-BSA-SMCC). This cPU-BSA-SMCC surface was then reacted with Traut's-modified 125I-rHir, a procedure which created free sulfhydryl groups on rHir (cPU-BSA-SMCC-S-125I-rHir). Using these crosslinking procedures, the cPU-BSA-SMCC-S-125I-rHir segments bound 188 +/- 40 ng/cm2 (n = 60) whereas the controls with non-specifically bound 125I-rHir (Mitrathane + EDC + BSA + 125I-rHir-SH and cPU-BSA + 125I-rHir-SH) bound 13 +/- 8 ng/cm2 and 4 +/- 8 ng/cm2, respectively. Evaluation of these cPU-BSA-SMCC-S-125I-rHir segments for 131I-thrombin inhibition using a chromogenic assay for thrombin showed that a maximum of 2.64 NIHU thrombin was inhibited in contrast to the controls which inhibited bound 0.76 and 0.70 NIHU. Controls with nonspecifically bound 125I-rHir also had 0.31 and 0.76 NIHU 131I-thrombin adherent to their respective surfaces whereas the maximum 131I-thrombin binding to the cPU-BSA-SMCC-S-rHir segments was 1.51 NIHU. Exposure to 131I-thrombin did not result in any release of covalently bound 125I-rHir from the cPU-BSA-SMCC-S-125I-rHir segments. Thus, these results demonstrate that rHir can be covalently bound to this novel polyurethane surface and still maintain potent antithrombin activity.

Antithrombins↗

PubMed1998

Endothelial dysfunction and the expression of endothelial nitric oxide synthetase in diabetic neuropathy, vascular disease, and foot ulceration.

We studied endothelial-mediated microvascular blood flow in neuropathic diabetic patients to determine the association between endothelial regulation of the microcirculation and the expression of endothelial constitutive nitric oxide synthetase (ecNOS) in the skin. Vasodilation on the dorsal foot in response to heating and iontophoresis of acetylcholine (endothelium-dependent) and sodium nitroprusside (endothelium-independent) were measured using single-point laser Doppler and laser Doppler imaging in diabetic patients with neuropathy (DN), with neuropathy and vascular disease (DI), with Charcot arthropathy (DA), and without complications (D), and in healthy control subjects (C). The response to heat was reduced in the DN (321 [21-629] percentage of increase over the baseline, median [interquartile range]) and DI (225 [122-470]) groups but was preserved in the DA (895 [359-1,229]), D (699 [466-1,029]), and C (810 [440-1,064], P < 0.0001) groups. The endothelial-mediated response to acetylcholine was reduced in the DN (17 [11-25]), DA (22 [2-34]), and DI (13 [2-30]) groups compared with the D (47 [24-58]) and C (44 [31-70], P < 0.001) groups. The non-endothelial-mediated response to sodium nitroprusside was also reduced in the DI (4 [0-18]), DN (17 [9-26]), and DA (21 [11-31]) groups compared with the D (37 [19-41]) and C (44 [26-67], P < 0.0001) groups. There was a significant reduction in vasodilation in the DI group compared with all other groups (P < 0.0001). Full thickness skin biopsies from the dorsum of the foot of 15 DN, 10 DI, and 11 C study subjects were immunostained with antiserum to human ecNOS, the functional endothelial marker GLUT1, and the anatomical endothelial marker von Willebrand factor. The staining intensity of ecNOS was reduced in both diabetic groups. No differences were found among the three groups in the staining intensity of von Willebrand factor and GLUT1. We conclude that the endothelium-dependent and endothelium-independent vasodilations are impaired in diabetic patients predisposed to foot ulceration and that neuropathy is the main factor associated with this abnormality. Reduced expression of ecNOS may be a major contributing factor for endothelial dysfunction. These data provide support for a close association of neuropathy and microcirculation in the pathogenesis of foot ulceration.

Acetylcholine↗

PubMed1998

Differences in foot and forearm skin microcirculation in diabetic patients with and without neuropathy.

OBJECTIVE: We have compared the hyperemic response to heat and the endothelium-dependent and endothelium-independent vasodilatation between the dorsum of the foot and the forearm in diabetic neuropathic and non-neuropathic patients and healthy control subjects. RESEARCH DESIGN AND METHODS: We studied the cutaneous microcirculation in the forearm and foot in 15 diabetic patients with neuropathy, in 14 diabetic patients without neuropathy, and in 15 control subjects matched for age, sex, BMI, and in the case of diabetic patients, for the duration of diabetes. Patients with peripheral vascular disease and/or renal impairment were excluded. The cutaneous microcirculation of the dorsum of the foot and the flexor aspect of the forearm was tested in all subjects. Single-point laser Doppler was employed to measure the maximal hyperemic response to heating of the skin to 44 degrees C and laser Doppler imaging scanner was used to evaluate the response to iontophoresis of 1% acetylcholine chloride (Ach) (endothelium-dependent response) and 1% sodium nitroprusside (NaNP) (endothelium-independent response). RESULTS: The transcutaneous oxygen tension was lower in the neuropathic group at both foot and forearm level, while the maximal hyperemic response to heat was similar at the foot and forearm level in all three groups. The endothelium-dependent vasodilation (percent increase over baseline) was lower in the foot compared to the forearm in the neuropathic group (23 +/- 4 vs. 55 +/- 10 [mean +/- SEM]; P < 0.01)], the non-neuropathic group (33 +/- 6 vs. 88 +/- 14; P < 0.01), and the control subjects (43 +/- 6 vs. 93 +/- 13; P < 0.001). Similar results were observed during the iontophoresis of NaNP (P < 0.05). No differences were found among the three groups when the ratio of the forearm:foot response was calculated for both the endothelium-dependent (neuropathic group, 2.25 +/- 0.24; non-neuropathic group, 2.55 +/- 0.35; and control subjects, 2.11 +/- 0.26; P = NS) and endothelium-independent vasodilation (neuropathic group, 1.54 +/- 0.27; non-neuropathic group, 2.08 +/- 0.33; and control subjects, 2.77 +/- 1.03; P = NS). The vasodilatory response, which is related to the C nociceptive fiber action, was reduced at the foot level during iontophoresis of Ach in the neuropathic group. In contrast, no difference was found during the iontophoresis of NaNP at the foot and forearm level and of Ach at the forearm level among all three groups. CONCLUSIONS: In healthy subjects, the endothelial-dependent and endothelial-independent vasodilatation is lower at the foot level when compared to the forearm, and a generalized impairment of the microcirculation in diabetic patients with neuropathy preserves this forearm-foot gradient. These changes may be a contributing factor for the early involvement of the foot with neuropathy when compared to the forearm.

Adult↗

PubMed1997

The effect of arterial reconstruction on the natural history of diabetic neuropathy.

OBJECTIVE: To determine whether reversal of hypoxia slows the progression of neuropathy. DESIGN: Cohort study with a mean follow-up of 19.2 months. SETTING: Institutional and private hospital. PATIENTS: A volunteer sample of 55 patients with diabetes (mean age, 62 years; range, 30-74 years; mean duration of diabetes, 21 years; range, 1-57 years) requiring lower-extremity arterial bypass. Twenty-one successfully treated patients were reexamined at the conclusion of the study. Neuropathy and hypoxia were assessed the day before the operation and during the follow-up visit. INTERVENTION: Lower-extremity arterial reconstruction. MAIN OUTCOME MEASURES: Peroneal nerve conduction velocity and transcutaneous oxygen tension. RESULTS: In the leg operated on, the peroneal nerve conduction velocity remained unchanged during the follow-up period (preoperative, mean [+/- SD] 35.79 +/- 6.02 vs postoperative 35.33 +/- 7.51 m/s; P > .05), but deteriorated in the leg not operated on (36.68 +/- 6.22 vs 33.64 +/- 7.30 m/s; P < .05, Wilcoxon signed rank test). Transcutaneous oxygen tension increased in the revascularized extremity (mean [+/- SD] 40.62 +/- 24.76 vs 66.73 +/- 14.89 mm Hg) but remained unchanged in the leg not operated on (56.76 +/- 17.07 vs 62.00 +/- 15.66 mm Hg; P > .05). Of the entire cohort, 5 patients died during the study period. Graft occlusion occurred in 10 (17%) of 59 extremities. Subset analysis disclosed that the preoperative transcutaneous oxygen tension was significantly higher in the successfully revascularized extremities (41.98 +/- 23.58 vs 24.10 +/- 21.50 mm Hg; P < .001). CONCLUSIONS: Reversal of hypoxia halts the progression of diabetic neuropathy, lending further support to the role of hypoxia in the pathogenesis of nerve destruction in diabetes mellitus. Preoperative transcutaneous oxygen tension is lower in patients with bypass failure, but the severity of neuropathy does not affect the outcome of the operation.

Adult↗

PubMed1997

Covalent linkage of recombinant hirudin to poly(ethylene terephthalate) (Dacron): creation of a novel antithrombin surface.

Thrombus formation and intimal hyperplasia on the surface of implantable biomaterials such as poly(ethylene terepthalate) (Dacron) vascular grafts are major concerns when utilizing these materials in the clinical setting. Thrombin, a pivotal enzyme in the blood coagulation cascade primarily responsible for thrombus formation and smooth muscle cell activation, has been the target of numerous strategies to prevent this phenomenon from occurring. The purpose of this study was to covalently immobilize the potent, specific antithrombin agent recombinant hirudin (rHir) to a modified Dacron surface and characterize the in vitro efficacy of thrombin inhibition by this novel biomaterial surface. Bovine serum albumin (BSA), which was selected as the "basecoat' protein, was reacted with various molar ratios of the cross-linker sulphosuccinimidyl 4-(N-maleimidomethyl) cyclohexane-1-carboxylate (sulpho-SMCC; 1:5-1:50). These BSA-SMCC complexes were then covalently linked to sodium hydroxide-hydrolysed Dacron (HD) segments via the cross-linker 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC). Covalent linkage of these complexes to HD (HD-BSA-SMCC) was not affected by any of the sulpho-SMCC cross-linker ratios assayed. rHir, which was initially reacted with 2-iminothiolane hydrochloride (Traut's reagent) in order to create sulphydryl groups, was then covalently bound to these HD-BSA-SMCC surfaces (HD-BSA-SMCC-S-rHir). The 1:50 (BSA: sulpho-SMCC) HD-BSA-SMCC-S-rHir segments bound 22-fold more rHir (111 ng per mg Dacron) compared to control segments and also possessed the greatest thrombin inhibition of the segments evaluated using a chromogenic substrate assay for thrombin. Further characterization of the HD-BSA-SMCC-S-rHir segments demonstrated that maximum thrombin inhibition was 20.43 NIHU, 14.6-fold greater inhibition than control segments (1.4 NIHU). Thrombin inhibition results were confirmed by 125I-thrombin binding experiments, which demonstrated that the 1:50 HD-BSA-SMCC-S-rHir segments had significantly greater specific thrombin adhesion compared to control segments. Non-specific 125I-thrombin binding to and release from the 1:50 HD-BSA-SMCC-S-rHir segments was also significantly less than the control segments. Thus, these results demonstrate that rHir can be covalently bound to a clinically utilized biomaterial (Dacron) while still maintaining its ability to bind and inhibit thrombin.

Animals↗

PubMed1997

Diabetes mellitus: a risk factor for carotid endarterectomy?

PURPOSE: Symptomatic cerebrovascular disease is more common in patients who have diabetes mellitus than in the nondiabetic population, even when matched for associated risk factors. Although the safety and efficacy of carotid endarterectomy has been established by NASCET and ACAS, several small studies have noted an increased rate of perioperative neurologic morbidity in patients with diabetes. METHODS: Data for all patients who underwent carotid endarterectomy at a single institution from Jan. 1990 to Dec. 1995 were prospectively entered into a computerized vascular registry and form the basis of this report. RESULTS: Of 732 carotid endarterectomy procedures performed, 284 (39%) were performed in patients who had diabetes mellitus. Patients with diabetes and without diabetes were matched for clinical presentation (diabetic patients, 45% asymptomatic; nondiabetic patients, 43%) and internal carotid artery percent stenosis (86.6% +/- 10.6% vs 86.4% +/- 10.6%). Patients with diabetes were younger at presentation than patients without (68.8 +/- 8.5 years vs 70.9 +/- 8.5 years; p < 0.005) and were more likely to have a history of coronary artery disease (53% vs 45%; p = 0.04). The mean total length of stay was 6.1 days for patients with diabetes and 4.8 days among patients without (p = 0.01). An adverse postoperative cardiac event (myocardial infarction, congestive heart failure, or arrhythmia) occurred in nine patients with diabetes (3.2%) and in five nondiabetic patients (1.1%; p < 0.05). By logistic regression analysis, however, diabetes was not an independent risk factor for a postoperative cardiac event (p = 0.28). There were 11 perioperative neurologic events (eight cerebrovascular accidents, three transient ischemic attacks) during the entire period (1.5%), of which six were among diabetic patients (2.1%) and five among nondiabetic patients (1.1%; p = NS). Of the eight cerebrovascular accidents, three occurred in diabetic patients (1.0%) and five in nondiabetic patients (1.1%; p = NS). The total operative mortality rate was 0.3% (diabetic patients, 1 of 284, 0.35%; nondiabetic, 1 of 447, 0.2%). CONCLUSIONS: Patients with diabetes who undergo carotid endarterectomy are more likely to have coexisting cardiac disease, which may contribute to a higher incidence of postoperative cardiac morbidity. Diabetes mellitus alone, however, is not a risk factor for postoperative cardiac morbidity in patients who undergo carotid surgery. In addition, carotid endarterectomy may be safely performed in patients with diabetes with neurologic morbidity and mortality rates that are comparable with those of the nondiabetic population

Aged↗

PubMed1997

Vascular endothelial growth factor expression in canine peripheral vein bypass grafts.

PURPOSE: Autologous veins used as arterial bypass grafts undergo initial loss of the endothelial cell (EC) lining, which is followed by reendothelialization. We characterized the expression of the EC-specific angiogenic mitogen, vascular endothelial growth factor (VEGF), in vascular grafts to help elucidate the molecular and cellular events after bypass procedures. METHODS: Cephalic vein-femoral artery interposition grafts were placed in mongrel dogs. Vein grafts and arteries were harvested at either 48 hours or 4 weeks after bypass, the total RNA was isolated, and the VEGF mRNA expression was evaluated by Northern blot analysis. Tissue segments from each time period were evaluated by immunohistochemical analysis using anti-VEGF antibodies. RESULTS: VEGF mRNA expression in vein grafts as compared with control veins was increased 2.5-fold 48 hours after bypass grafting (p = 0.02) but returned to initial control levels in grafts removed at 4 weeks. Distal arterial segments, which included the anastomotic site without attached vein graft, had a 21.4-fold increase in VEGF expression at 48 hours (p = 0.02) and a 6.6-fold increase at 4 weeks (p < 0.01) as compared with control arterial segments. Vessels subjected to arteriotomy or ischemia alone also demonstrated increased VEGF expression. Immunohistochemical analysis revealed VEGF protein within ECs and smooth muscle cells of the venous bypass graft, with maximal levels observed within intimal hyperplasia at the arterial anastomosis. CONCLUSIONS: After arterial reconstruction procedures using venous conduits, VEGF is significantly increased at 48 hours in the vein graft and arterial anastomosis. VEGF expression in the vein graft normalizes within 4 weeks but remains significantly elevated in the adjacent arterial segment. Increased VEGF production after arterial grafting may facilitate reendothelialization, thus partially accounting for optimal patency rates achieved with autologous vein grafts.

Animals↗

PubMed1997

Anesthesia type does not influence early graft patency or limb salvage rates of lower extremity arterial bypass.

PURPOSE: The effect of anesthesia type on 30-day graft patency and limb salvage rates was evaluated in patients who underwent femoral to distal artery bypass. METHODS: Of 423 patients randomly assigned to receive general, spinal, or epidural anesthetic, 76 did not meet protocol standards and 32 had inadequate anesthesia. A chart review of the remaining 315 patients was undertaken to obtain surgical information not recorded in the original study. All patients were monitored with radial and pulmonary artery catheters. After surgery, patients were in a monitored setting for 48 to 72 hours and had graft function assessments hourly during the first 24 hours and then every 8 hours until discharge. RESULTS: Fifty-one patients were lost to follow-up (15 general, 22 spinal, 14 epidural). Baseline clinical characteristics were similar for the three groups except prior carotid artery surgery, which was more common in the spinal group. Indications for surgery were also similar except for a higher incidence of nonhealing ulcer in the epidural group. There were no differences among groups for 30-day graft patency with or without reoperation, 30-day graft occlusion, death, amputation, or length of hospital stay. CONCLUSION: These results suggest that the type of anesthetic given for femoral to distal artery bypass does not significantly affect 30-day occlusion rate, limb salvage rate, or hospital length of stay.

Aged↗

PubMed1997

Chemical and physical characterization of a novel poly(carbonate urea) urethane surface with protein crosslinker sites.

A major complication which occurs with implantable polyurethane biomaterials is bioincompatibility between blood and the biomaterial surface. Development of a novel biodurable polyurethane surface to which biological agents, such as growth factors or anticoagulants could be covalently bound, would be beneficial. The purpose of this study was to synthesize a novel poly(carbonate urea) urethane polymer with carboxylic acid groups which would serve as "anchor" sites for protein attachment. Physical characteristics such as tensile strength, initial modulus, ultimate elongation, tear strength, water/alcohol uptake and water vapor permeation were then evaluated and compared to other biomedical-grade polyurethanes. Covalent linkage of the blood protein albumin to this novel surface was then examined. A biodurable polycarbonate-based polyurethane containing carboxylic acid groups (cPU) was synthesized using a two step procedure incorporating the chain extender 2,2-bis(hydroxymethyl)-propionic acid (DHMPA). Tensile strength of this cPU film was 2.7 and 2.6 fold greater than both a polycarbonate-based polyurethane synthesized with a 1,4-butanediol chain extender (bdPU) and Mitrathane (Mit) controls, respectively. The cPU polymer also possessed 7.8 and 31 fold greater structural rigidity upon evaluation of initial modulus as compared to the bdPU and Mit, respectively. Ultimate elongation for the bdPU films was slightly higher than the cPU and Mit films, which had comparable elongation properties. The force required to tear the bdPU film was 1.9 and 32 fold greater than the cPU and Mit films, respectively. Alcohol solution uptake by all of the polyurethane segments increased with increasing alcohol concentrations, with the cPU having the greatest uptake. Water uptake was minimal for all the polyurethanes examined and was not affected by altering pH. Water vapor permeation was lowest for the cPU films as compared to both bdPU and Mit. Swelling the cPU in 50% ethanol prior to evaluation slightly increased water vapor permeation through the films. Covalent linkage of the radiolabelled blood protein albumin (125I-BSA) to the cPU segments incubated with the heterobifunctional crosslinker 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) was greatest in the higher percent of ethanol as compared to controls. These results serve as foundation for developing a novel poly(carbonate urea) urethane with physical characteristics comparable to other medical-grade polyurethanes while having protein binding capabilities.

Adsorption↗

PubMed1997

Lower extremity macrovascular disease in diabetes.

Lower extremity macrovascular disease is more common and progresses more rapidly in the presence of diabetes and has a characteristic peritibial distribution with sparing of the foot arteries. The biology of the diabetic foot is compromised, thereby making it more susceptible to injury. Hence, compromises in perfusion have a greater significance, warranting an aggressive approach to revascularization.

Arterial Occlusive Diseases↗

PubMed1996

The impact of reversal of hypoxia by revascularization on the peripheral nerve function of diabetic patients.

Hypoxia is considered to be one of the main aetiopathogenic factors of diabetic neuropathy. We have examined the effects of the reversal of hypoxia, achieved by revascularization, on peripheral nerve function in diabetic patients with or without clinical neuropathy. Fifty-six patients [mean age 62 (range 30-74) years, 44 (79%) males, 15 (27%) with insulin-dependent diabetes of 20 years (range 1-57) duration, and creatinine level 92.8 +/- 30.9 mumol/l (mean +/- SD)] were tested pre-operatively while 30 (54%) were reexamined at least 6 weeks post-operatively. At baseline the leg scheduled for operation showed worse measurements compared to the control leg when tested for Semmes-Weinstein monofilaments, peroneal motor conduction velocity (PMCV) (33.7 +/- 7.18 vs 35.7 +/- 6.09 m.s-1, p < 0.05) and transcutaneous oxygen tension (37.4 +/- 24.6 vs 52.0 +/- 21.5 mm Hg, p < 0.0001) while no differences were found in the vibration perception threshold and leg temperature. When baseline and post-operative measurements were later compared in the operated leg, no differences were noticed in the vibration perception threshold, PMCV and Semmes-Weinstein monofilaments but the transcutaneous oxygen tension increased significantly (32.7 +/- 27.1 vs 64.6 +/- 14.5 mm Hg, p < 0.001). No differences were noticed in any of the above parameters in the contralateral leg. No correlations were found between changes in transcutaneous oxygen tension and PMCV values measured at baseline and at the follow-up visit in either leg. Similar results were found when patients were stratified according to severity of neuropathy, ischaemia and the level of the bypass. We conclude that although there is greater impairment of nerve function in the more ischaemic leg, reversal of hypoxia does not result in any significant improvement of the nerve function measurements.

Adult↗