Benchmarking a Center of Excellence in Vascular Surgery: Using Acute Physiology and Chronic Health Evaluation II to Validate Outcomes in a Tertiary Care Institute.

OBJECTIVE: The Society of Vascular Surgery (SVS) has made it a top priority to implement verification of vascular "centers of excellence". Our institutional aortic network was established in 2008 in order to standardize care of patients with suspected acute aortic pathology. The implementation and success of this program has been previously reported. We sought to use our experience as a benchmark for which to develop prognostic modeling to quantify clinical status upon admission and help predict outcomes. Our objective was to validate the Acute Physiology and Chronic Health Evaluation (APACHE) II scoring system using a cohort of aortic emergencies transferred by an organized transfer network. METHOD: This was a retrospective, single institution review of patients transferred through an institutional aortic network for acute aortic pathology from 2017-2018. Demographics, comorbidities, aortic diagnosis, APACHE II score, as well as 30-day mortality were recorded. Associations with 30-day mortality were evaluated using two-sample t-tests, ANOVA models, Pearson chi-square tests and Fisher exact tests. Receiver operating characteristic (ROC) curves were fit overall and by pathology to predict 30-day mortality by Apache II total score. RESULTS: There were 395 consecutive transfers were identified. The mean age was 64.7 years. Diagnoses included Type A Dissection (n = 134), Type B (n = 81), Aortic Aneurysm (n = 122), and PAU/IMH (n = 27). Mean APACHE II score on arrival was 12. Overall there were 53 deaths (13.4%) in the cohort. Patients that died had significantly higher Apache II total scores (11.3 vs 16.5, P < .001). The area under the receiver operator characteristic (ROC) curve (AUC) was .66 for the full cohort, indicating a poor clinical prediction test. CONCLUSION: APACHE II score is a poor predictor of 30-day mortality in a large transfer network accepting all aortic emergencies. The authors believe further refining a prognostic model for diverse population will not only help in predicting outcomes but to objectively quantify illness severity in order to have a basis for comparison among institutions and verification of "centers of excellence".

Society for Vascular Surgery practice guidelines for atherosclerotic occlusive disease of the lower extremities: management of asymptomatic disease and claudication

Peripheral arterial disease (PAD) continues to grow in global prevalence and consumes an increasing amount of resources in the United States health care system. Overall rates of intervention for PAD have been rising steadily in recent years. Changing demographics, evolution of technologies, and an expanding database of outcomes studies are primary forces influencing clinical decision making in PAD. The management of PAD is multidisciplinary, involving primary care physicians and vascular specialists with varying expertise in diagnostic and treatment modalities. PAD represents a broad spectrum of disease from asymptomatic through severe limb ischemia. The Society for Vascular Surgery Lower Extremity Practice Guidelines committee reviewed the evidence supporting clinical care in the treatment of asymptomatic PAD and intermittent claudication (IC). The committee made specific practice recommendations using the GRADE (Grades of Recommendation Assessment, Development and Evaluation) system. There are limited Level I data available for many of the critical questions in the field, demonstrating the urgent need for comparative effectiveness research in PAD. Emphasis is placed on risk factor modification, medical therapies, and broader use of exercise programs to improve cardiovascular health and functional performance. Screening for PAD appears of unproven benefit at present. Revascularization for IC is an appropriate therapy for selected patients with disabling symptoms, after a careful risk-benefit analysis. Treatment should be individualized based on comorbid conditions, degree of functional impairment, and anatomic factors. Invasive treatments for IC should provide predictable functional improvements with reasonable durability. A minimum threshold of a >50% likelihood of sustained efficacy for at least 2 years is suggested as a benchmark. Anatomic patency (freedom from restenosis) is considered a prerequisite for sustained efficacy of revascularization in IC. Endovascular approaches are favored for most candidates with aortoiliac disease and for selected patients with femoropopliteal disease in whom anatomic durability is expected to meet this minimum threshold. Conversely, caution is warranted in the use of interventions for IC in anatomic settings where durability is limited (extensive calcification, small-caliber arteries, diffuse infrainguinal disease, poor runoff). Surgical bypass may be a preferred strategy in good-risk patients with these disease patterns or in those with prior endovascular failures. Common femoral artery disease should be treated surgically, and saphenous vein is the preferred conduit for infrainguinal bypass grafting. Patients who undergo invasive treatments for IC should be monitored regularly in a surveillance program to record subjective improvements, assess risk factors, optimize compliance with cardioprotective medications, and monitor hemodynamic and patency status.(AU)

An expanded series of distal bypass using the distal vein patch technique to improve prosthetic graft performance in critical limb ischemia.

OBJECTIVES: The endovascular first approach has led to increasing complexity for surgical bypass especially in those patients without autogenous conduit. The use of vein interposed at the distal anastomosis has been reported to improve the results of prosthetic grafts. This series expands our initial experience with the distal vein patch technique (DVP) reporting a larger cohort with enhanced follow-up. DESIGN: A retrospective review of prospectively collected data was performed for distal bypasses from July 1995 to November 2008. MATERIALS/METHODS: 1296 tibial bypasses were performed with 270 using the DVP technique. Patient demographics included; 49% diabetes, 20% chronic renal failure, 33% prior failed bypass. Indications for revascularization were claudication (9.3%), rest pain (27.8%), gangrene (22.2%), and non-healing ulceration (40.7%). Lack of vein for the bypass conduit resulted from previous failed grafts (55%), coronary bypass (18%), poor quality vein (23%), or prior vein stripping (8%). Follow-up ranged from 1 to 48 months with graft surveillance by pulse exam, ABI, and Duplex ultrasound. Primary patency and limb salvage ± SE were determined by Kaplan-Meier life-table analysis using Rutherford criteria. RESULTS: Bypasses originated from the external iliac (29%), CFA (55%), SFA (13%), popliteal (1%), and prior grafts (2%). Recipient arteries were below knee popliteal (6%), anterior tibial (25%), posterior tibial (30%), and peroneal (39%). Perioperative graft failure occurred in 13 cases with a total of 41 graft failures leading to 39 major amputations. Primary graft patency from one to four years was 79.8%, 75.6% 65.9%, and 51.2%. Corresponding limb salvage rates were 80.6%, 78.0%, 75.7%, and 67.5%. CONCLUSION: Although not addressed by a randomized trial, we believe this expanded series is a more accurate reflection of expected results confirming that the DVP bypass leads to reasonable long-term results for those challenging patients that require prosthetic distal bypass for lower extremity revascularization.

Critical interactions between TGF-beta signaling/ELF, and E-cadherin/beta-catenin mediated tumor suppression.

Inactivation of the transforming growth factor-beta (TGF-beta) pathway occurs often in malignancies of the gastrointestinal (GI) system. However, only a fraction of sporadic GI tumors exhibit inactivating mutations in early stages of cancer formation, suggesting that other mechanisms play a critical role in the inactivation of this pathway. Here, we show a wide range of GI tumors, including those of the stomach, liver and colon in elf+/- and elf+/- / Smad4+/- mutant mice. We found that embryonic liver fodrin (ELF), a beta-Spectrin originally identified in endodermal stem/progenitor cells committed to foregut lineage, possesses potent antioncogenic activity and is frequently inactivated in GI cancers. Specifically, E-cadherin accumulation at cell-cell contacts and E-cadherin-beta-catenin-dependent epithelial cell-cell adhesion is disrupted in elf+/- / Smad4+/- mutant gastric epithelial cells, and could be rescued by ectopic expression of full-length elf, but not Smad3 or Smad4. Subcellular fractionation revealed that E-cadherin is expressed mainly at the cell membrane after TGF-beta stimulation. In contrast, elf+/- / Smad4+/- mutant tissues showed abnormal distribution of E-cadherin that could be rescued by overexpression of ELF but not Smad3 or Smad4. Our results identify a group of common lethal malignancies in which inactivation of TGF-beta signaling, which is essential for tumor suppression, is disrupted by inactivation of the ELF adaptor protein.

Common femoral artery ligation and local debridement: a safe treatment for infected femoral artery pseudoaneurysms.

PURPOSE: The management of infected femoral artery pseudoaneurysms (IFAPs) is difficult and controversial. Use of synthetic or autologous conduit during arterial revascularization in these cases is complicated by the presence of sepsis and unavailability of autologous venous conduit. We present the results of common femoral artery (CFA) ligation and local drainage with debridement for the treatment of IFAP. METHODS: A retrospective chart review of six consecutive patients from 1995 to 1999 who presented with IFAP from intravenous drug abuse was performed. Inpatient records, anesthesia records, and outpatient clinic charts were reviewed. All patients were men with right-sided lesions. All six patients abused heroin, and five (83%) abused heroin and cocaine. All six patients had a duplex ultrasound scan, and five (83%) patients had a digital subtraction angiogram to confirm the clinical diagnosis. Proximal vascular control was achieved retroperitoneally through an oblique suprainguinal incision. After vascular isolation and test clamping of the distal external iliac artery (EIA), the pedal pulses were examined with continuous wave Doppler scan. If a Doppler signal was present, this was followed with CFA ligation and local drainage and debridement of the IFAP. RESULTS: Pain at injection site and fever with chills were present in five (83%) and three (50%) patients, respectively. A pulsatile groin mass and thigh or leg edema were present in five (83%) patients. Three patients (50%) had a palpable pedal pulse, and all six had a Doppler signal over a pedal artery at presentation. The mean white cell count was 15.6 thousand per cubic millimeter (range, 9.2-19.3). All patients had a Doppler signal over a pedal artery after distal EIA/CFA test occlusion and ligation. None of the patients required an amputation, and all six patients regained their preoperative ambulatory status. The mean follow-up period was 25 months. Two patients had mild claudication (5-6 blocks) at 18 months and 2 years after surgery. All six patients received drug rehabilitation, but they admitted to drug abuse after surgery and rehabilitation. CONCLUSION: CFA ligation and local debridement are safe treatment modalities for IFAP, if there is an intraoperative Doppler signal over a pedal artery during test occlusion of the distal EIA/CFA. CFA ligation avoids the use and therefore the risk of synthetic conduit infection, because there is a high incidence of postoperative drug injection despite aggressive drug rehabilitation.

Basic science curriculum in vascular surgery residency.

Recognizing the importance of basic science teaching in surgical education, the leadership of the Association of Program Directors in Vascular Surgery (APDVS) appointed a panel to gather information and to present its findings at the 1999 annual fall meeting of the Apdvs. A questionnaire was distributed to the program directors present. In addition, information was gathered from the American Board of Surgery regarding the basic science content in the vascular surgery item pool on the vascular surgery qualifying examination (VQE). The vascular surgery unit of the surgical resident curriculum was also analyzed. Fifty-three program directors (64%) completed the questionnaire. Although only two program directors felt that their residents were better prepared to answer basic science questions, the results of the Vqe showed that the examinees do not, as a group, perform differently on basic science items than on clinical management questions. In addition, only a minority of program directors (15%) use a specific method to monitor the learning process of their residents. The majority of the program directors responding (75%) felt that they were capable of teaching basic science to residents. Interestingly, almost half the 53 respondents (47%) said that a basic science curriculum should be comprehensive, not exclusively relevant to the clinical setting. Vqe content outline and the vascular surgery unit of the surgical resident curriculum revealed great emphasis on clinically relevant basic science information. The Apdvs panel recommends that a basic science curriculum should be comprehensive, yet clinically pertinent, and completely integrated with the clinical curriculum. In terms of how to teach basic science in vascular residencies, the panel supports teaching conferences that are problem-based with a faculty member acting as the "resource person" and with specific goals set for the conferences. The panel also suggested establishing a Web site that provides a series of questions, the answers of which could be readily available to trainees and program directors. such immediate feedback could be of great help to program directors to focus the learning process of their residents and monitor its progress.

A novel insulin mimetic without a proliferative effect on vascular smooth muscle cells.

BACKGROUND: Insulin induces vascular smooth muscle cell (VSMC) proliferation, which is an important step in the atherosclerotic process. Recently, a nonpeptidyl fungal metabolite originally referred to as L-783,281, but also known as demethylasterriquinone B-1 (DMAQB-1), was found to have hypoglycemic activity in diabetic mice through interaction with the intracellular beta subunit of the insulin receptor. This study was designed to determine whether DMAQB-1 has an insulin-like proliferative effect on human infragenicular VSMCs. METHODS: Human infragenicular VSMCs were isolated from diabetic patients undergoing amputations. DMAQB-1 cell culture dose response was measured in both serum-free media and media with 1% fetal bovine serum (FBS). A working concentration of DMAQB-1 that ranged from 0.5 to 500 nmol/L was studied in the presence of varying concentrations of glucose and insulin. The ability of DMAQB-1 to stimulate glucose transport at less than or equal to 100 nmol/L was determined by [(14)C]-2-deoxyglucose uptake. DNA synthesis was used as the marker for proliferative stimulus and detected by [(3)H]-thymidine uptake measured at 24 hours. Analysis of variance was used to compare the results among the groups; a P value less than.05 was considered significant. Polynomial regression was used to calculate the median lethal dose. RESULTS: In normal glucose media (100 mg/dL), various concentrations of DMAQB-1 demonstrated a small but statistically significant decrease in DNA synthesis at 0.5 nmol/L in serum-free media and at 5 nmol/L in media supplemented with 1% FBS. The corresponding median lethal dose was 107 nmol/L in serum-free media and 650 nmol/L in media supplemented with 1% FBS. A DMAQB-1 concentration of 5 nmol/L induced glucose transport that was equivalent to an insulin concentration of 100 microU/mL. In serum-free, high glucose media (200 mg/dL), DMAQB-1 concentrations up to 500 nmol/L did not cause a statistically significant change in DNA synthesis. When serum-free, high glucose media was combined with mild (100 microU/mL) or moderate (250 microU/mL) concentrations of insulin, DMAQB-1 caused no statistically significant increase in DNA synthesis. CONCLUSION: Nontoxic doses of DMAQB-1 can induce glucose transport equivalent to insulin in the physiologic range. However, DMAQB-1 does not have an insulin-like proliferative effect on human VSMCs in normal-glucose, high-glucose, or high-insulin environments.

Thiamine (Vitamin B1) protects against glucose- and insulin-mediated proliferation of human infragenicular arterial smooth muscle cells.

Accelerated proliferation of arterial smooth muscle cells (ASMC) plays an important role in the development of atherosclerosis, which preferentially affects the infragenicular vasculature in patients with diabetes mellitus. High insulin and glucose levels, which are present in patients with type II diabetes, have an additive effect in infragenicular ASMC proliferation in vitro. Thiamine is a coenzyme important in intracellular glucose metabolism. The objective of this study is to determine the effect of thiamine on human infragenicular ASMC proliferation induced by high glucose and insulin levels in vitro. Human infragenicular ASMC isolated from diabetic patients undergoing lower extremity amputation were used. Cells were cultured at 37 degrees C in 5% CO(2). Cells were identified as ASMC by immunohistochemical analysis. Cells from passages 3-5 were exposed to glucose concentrations of 0.1 and 0.2% with and without insulin concentrations of 100 ng/mL and 1000 ng/mL, in the presence or absence of 200 microM of thiamine. Standard hemocytometry and (3)H-thymidine incorporation quantified cell proliferation after incubation for 6 days and 24 hr, respectively. The data suggest that thiamine inhibits human infragenicular ASMC proliferation induced by high glucose and insulin. Vitamin B1 intake may prove important in delaying the atherosclerotic complications of diabetes.

Accelerated carotid artery disease after high-dose head and neck radiotherapy: is there a role for routine carotid duplex surveillance?

PURPOSE: High-dose external radiotherapy used in the treatment of head and neck carcinoma has been implicated as a risk factor for accelerated atherosclerotic disease of the carotid arteries. However, how radiotherapy affects atherosclerotic disease is controversial, and little data exist to demonstrate a strong relationship between radiotherapy and progressive carotid disease. METHODS: We performed a retrospective chart review of 69 patients (all men) who underwent duplex ultrasound scanning examinations for carotid disease between 1993 and 1998. Twenty-three patients had received high-dose radiotherapy for the treatment of head and neck carcinoma within the past 12 years (group 1; mean age, 67.8 years), and 46 patients were randomly selected as age-matched control subjects (group 2; mean age, 68.3 years). The mean radiation dose was 6060 +/- 182 rads, and the average interval between radiotherapy and ultrasound scanning was 6. 5 +/- 1.8 years. There was no significant difference between the two groups in the presence of these comorbidities: diabetes mellitus, coronary artery disease, hypertension, tobacco use, hypercholesterolemia, peripheral vascular disease, or stroke. Similarly, there was no difference in the indications for the duplex scanning studies. RESULTS: Five of the 23 patients in group 1 (21. 7%) were found to have advanced carotid disease (70% to 99% stenosis); four patients were symptomatic, three patients went on to endarterectomy, and one patient was awaiting surgery. Two of the 46 patients in the control group (4%) had advanced carotid disease. One patient was symptomatic, and both patients underwent endarterectomy. A significant difference in the prevalence of advanced disease between the two groups was noted (P =.037). Sixteen patients who survived irradiation underwent a second duplex scanning study and had evidence of progressive disease with significant increases in peak systolic velocities. CONCLUSION: High-dose radiotherapy to the head and neck region may be a significant risk factor for accelerated carotid atherosclerotic disease. Routine carotid duplex surveillance may be warranted in this high-risk patient population.

Folic acid inhibits homocysteine-induced proliferation of human arterial smooth muscle cells.

PURPOSE: An elevated plasma homocysteine level has been identified as an independent risk factor for atherosclerosis. Whether this represents a marker for vascular disease or a direct effect on the vasculature remains unclear. Because vascular smooth muscle cells (VSMCs) play an integral role in the atherosclerotic process, we studied the effect of homocysteine on human infragenicular VSMC proliferation and the role of folic acid in reversing the homocysteine effect. METHODS: Human infragenicular VSMCs harvested from amputation specimens were studied. Various cell groups were exposed to physiologic (6.25 micromol/L and 12.5 micromol/L) and pathologic (25 micromol/L to 500 micromol/L) concentrations of homocysteine. Similar groups were simultaneously exposed to 20 nmol/L of folic acid. Cell counts and DNA synthesis, as reflected by [methyl-(3)H]-thymidine incorporation, were performed at 6 days and 24 hours, respectively. Additional groups were exposed to various combinations of folic acid (20 nmol/L), vitamin B(6) (145 nmol/L), and vitamin B(12) (0.45 nmol/L) in the presence of homocysteine (25, 50, and 250 micromol/L). RESULTS: Homocysteine resulted in a dose-dependent increase in DNA synthesis and cell proliferation. Cell counts increased significantly at homocysteine concentrations ranging from 25 micromol/L to 500 micromol/L (P <.05), with a maximal increase of 98% at 500 micromol/L of homocysteine. The addition of 20 nmol/L folic acid resulted in significant inhibition of cell proliferation at all homocysteine concentrations studied (P <.001). Maximal inhibition of 70% occurred in the cells exposed to 50 micromol/L of homocysteine. The increases in [methyl-(3)H]-thymidine incorporation ranged from 36% at 6 micromol/L homocysteine to a maximum of 247% at 500 micromol/L homocysteine. All increases were statistically significant (P <.05). The addition of 20 nmol/L folic acid resulted in significant inhibition of DNA synthesis (P <.002). Vitamins B(6) and B(12) did not demonstrate significant antiproliferative properties. CONCLUSION: A possible role of homocysteine in the formation of atherosclerotic lesions is through a direct proliferative effect on VSMCs in a dose-dependent fashion. Folic acid intake at levels available in dietary supplements may prove protective in hyperhomocysteinemia-induced atherosclerosis. Vitamins B(6) and B(12) alone do not appear to exhibit a substantial inhibitory effect in the setting of elevated homocysteine levels.

Prevalence of peripheral arterial disease and associated risk factors in American Indians: the Strong Heart Study.

Studies of peripheral arterial disease (PAD) in minority populations provide researchers with an opportunity to evaluate PAD risk factors and disease severity under different types of conditions. Examination 1 of the Strong Heart Study (1989-1992) provided data on the prevalence of PAD and its risk factors in a sample of American Indians. Participants (N = 4,549) represented 13 tribes located in three geographically diverse centers in the Dakotas, Oklahoma, and Arizona. Participants in this epidemiologic study were aged 45-74 years; 60% were women. Using the single criterion of an ankle brachial index less than 0.9 to define PAD, the prevalence of PAD was approximately 5.3% across centers, with women having slightly higher rates than men. Factors significantly associated with PAD in univariate analyses for both men and women included age, systolic blood pressure, hemoglobin A1c level, albuminuria, fibrinogen level, fasting glucose level, prevalence of diabetes mellitus, and duration of diabetes. Multiple logistic regression analyses were used to predict PAD for women and men combined. Age, systolic blood pressure, current cigarette smoking, pack-years of smoking, albuminuria (micro- and macro-), low density lipoprotein cholesterol level, and fibrinogen level were significantly positively associated with PAD. Current alcohol consumption was significantly negatively associated with PAD. In American Indians, the association of albuminuria with PAD may equal or exceed the association of cigarette smoking with PAD.

Insulin action enhancement normalizes brachial artery vasoactivity in patients with peripheral vascular disease and occult diabetes.

PURPOSE: Brachial artery vasoactivity (BAVA) evaluation is a reliable, noninvasive method of assessing arterial endothelial function in vivo. We previously have shown that patients with peripheral vascular disease (PVD) and occult diabetes have abnormal BAVA results when fasting and after oral glucose intake during oral glucose tolerance test (OGTT). Troglitazone is an oral hypoglycemic agent that enhances the action of insulin. The effect of troglitazone on BAVA in patients with occult diabetes and PVD is not known. METHODS: Patients with PVD, normal fasting glucose levels, and abnormal OGTT results were identified. With a duplex ultrasound scan, BAVA was evaluated by measuring the brachial artery (BA) flow (in millimeters per minute) before and after 5 minutes of BA occlusion during fasting and at 30 minutes, 1 hour, and 2 hours after the administration of 75 g of glucose during OGTT. Troglitazone therapy (400 mg/day) was begun, and the BAVA evaluation was repeated after 2 and 4 months. These results were compared with the results of the control group who had normal fasting glucose levels, normal OGTT results, and no evidence of PVD. A paired t test was used to compare the BA flow before and after BA occlusion, with a P value of less than.05 considered significant. RESULTS: The control group had a normal hyperemic response with a significantly increased BA flow after 5 minutes of BA occlusion during fasting and at all stages of the OGTT. The occult diabetic group had an abnormal response to hyperemia before the treatment with troglitazone and showed little change in flow after BA occlusion. After 2 months of troglitazone therapy, BAVA results improved after oral glucose intake but not during fasting. After 4 months, BAVA results normalized both while fasting and after oral glucose intake during the OGTT. CONCLUSION: Patients with occult diabetes and PVD have impaired BAVA, which normalizes after treatment with troglitazone. Insulin-action enhancers may slow the progression of PVD in patients with diabetes by improving endothelial cell function. Agents that are aimed at enhancing the action of insulin may have an advantage over the other traditional therapies for diabetes.

The additive effects of glucose and insulin on the proliferation of infragenicular vascular smooth muscle cells.

PURPOSE: Peripheral vascular disease involving the infragenicular arterial tree is common in patients with diabetes mellitus (DM). Accelerated proliferation of vascular smooth muscle cells (VSMCs) plays an important role in the development of atherosclerosis. Insulin and glucose stimulate VSMC proliferation and are elevated in patients with non-insulin-dependent DM. We have previously described the mitogenic effect of insulin on VSMCs in vitro; the effects of insulin and glucose separately and in combination on the proliferation of VSMCs grown in serum-free media were studied. METHODS: Human infragenicular VSMCs isolated from diabetic patients with end-stage peripheral vascular disease undergoing below-knee amputation were used. Cells from passages 3 to 5 were grown in serum-free media with varying glucose (0.05%, 0.1%, 0.2%, 0.4%, 0.6%, and 0.8%) and insulin (no added insulin, 100 ng/mL, and 1000 ng/mL) concentrations for 6 days. RESULTS: Insulin stimulated VSMC growth at glucose concentrations more than 0.2% (0.4% glucose with no added insulin resulted in 13,073 +/- 336 cells/mL, 0.4% glucose with 100 ng/mL insulin resulted in 16,536 +/- 1175 cells/mL, 0.4% glucose with 1000 ng/mL insulin resulted in 17,500 +/- 808 cells/mL, 0.6% glucose with no added insulin resulted in 14,167 +/- 1062 cells/mL, 0.6% glucose with 100 ng/mL insulin resulted in 18,984 +/- 1265 cells/mL, 0.6% glucose with 1000 ng/mL insulin resulted in 20,450 +/- 1523 cells/mL, 0.8% glucose with no added insulin resulted in 15, 853 +/- 1650 cells/mL, 0.8% glucose with 1000 ng/mL insulin resulted in 26,302 +/- 1919 cells/mL; P <.05 compared with glucose with no added insulin). Glucose stimulated VSMC proliferation up to a concentration of 0.2% (42% and 117% higher growth at 0.1% and 0.2% glucose, respectively, compared with the baseline, P <.05), regardless of the insulin concentration in the media. The greatest growth (26,302 +/- 1919 cells/mL) occurred in the group with the highest concentration of both insulin (1000 ng/mL) and glucose (0.8% glucose; P <.05). CONCLUSION: Both insulin and glucose stimulate the growth of diabetic infragenicular VSMCs. The mitogenic effects of insulin and glucose are additive and may contribute to the development of atherosclerosis in patients with DM.

Myointimal hyperplasia: basic science and clinical considerations.

The mechanical injury caused by a bypass procedure or angioplasty of the coronary or peripheral arteries can initiate and maintain the process of myointimal hyperplasia. Myointimal hyperplasia is of great clinical importance. The development of the hyperplastic lesion at the outflow anastomosis of a prosthetic bypass or in autogenous saphenous vein bypass placed in the arterial system is responsible for most bypass failures. It is also the primary cause of restenosis after coronary angioplasty. Myointimal hyperplasia is a complex pathological process of the vascular system characterized by an abnormal proliferation of smooth muscle cells of the vascular wall. Proliferating smooth muscle cells migrate to the subendothelial area and form the hyperplastic lesion, which causes stenosis and obstruction of the vascular lumen. The pathogenesis of myointimal hyperplasia remains under investigation. However, it has been established that both mechanical and chemical factors may induce this process. Arterial injury is believed to stimulate the production of growth factors, such as platelet-derived growth factor (PDGF), which have been shown to stimulate the proliferation of arterial smooth muscle cells and the formation of the hyperplastic lesion in the vascular system. These growth factors and cytokines have been found to be secreted by a variety of cells, including endothelial cells, macrophages, platelets, and arterial smooth muscle cells. Blocking the effects of growth factors such as PDGF or fibroblast growth factor (FGF), by the administration of their antibodies, has been shown to limit the development of the hyperplastic lesion. In this article, we begin with the basic physiology of myointimal hyperplasia. We then address possible therapeutic considerations for the future.

The pathophysiology of atherosclerosis.

Complications resulting from advanced atherosclerosis are the most common indication for vascular reconstructive surgery. Atherosclerosis is a systemic disease affecting the entire arterial tree, but lesions involving the coronary, extracranial cerebral, and lower extremity circulations have the most clinical significance for surgeons. The pathogenesis of atherosclerosis involves a complex series of events, similar to a chronic inflammatory process, with the formation of atherosclerotic plaque as the end result. Injury to the endothelial cell of the artery, resulting in endothelial cell dysfunction, is the first step in the process. Activated endothelial cells attract leukocytes and vascular smooth muscle cells (VSMC), which accumulate and proliferate in the arterial wall. These cellular components produce an excessive amount of connective tissue matrix. The ultimate end point is the formation of a mature fibrous plaque. Symptoms occur when advanced lesions are complicated by plaque rupture, hemorrhage into the plaque, emboli, or thrombosis. A thorough understanding of the pathogenesis of atherosclerosis is essential for the development of strategies for the prevention of the disease, and for the development of new and effective treatments.

Peptide growth factors and signal transduction.

Cell differentiation and proliferation are influenced by peptide growth factors. These peptide molecules are important in maintaining the normal development and growth of animal cells; in addition, they have been found to play a major role in disease states. The role of growth factors in the development of arteriosclerosis and intimal hyperplasia is of great interest to us as physicians taking care of patients with peripheral vascular disease. Factors such as platelet-derived growth factor (PDGF), fibroblast growth factor (FGF), insulin, insulin-like growth factor-I (IGF-I), and transforming growth factors alpha and beta (TGF alpha and beta) have been found to play important roles in controlling the progression of cells in the cell cycle. Furthermore, various growth factors have been found to influence the motility of cells, particularly vascular smooth muscle cells (VSMCs).

The effect of occult diabetic status and oral glucose intake on brachial artery vasoactivity in patients with peripheral vascular disease.

Brachial artery vasoactivity is a well known non-invasive method of assessing arterial endothelial function in vivo. Brachial artery vasoactivity has been found to be impaired in overt diabetes and in patients with coronary artery disease. Impaired brachial artery vasoactivity is felt to be an early indicator of atherosclerosis. The authors identified a group of patients with lower extremity peripheral vascular disease, who had normal fasting glucose level and were not known to be diabetics. An oral glucose tolerance test was performed in this group of patients. Brachial artery vasoactivity was assessed at each step of the oral glucose tolerance test to examine their occult diabetic status and correlate brachial artery vasoactivity to that status. The authors studied 23 randomly selected patients from the vascular surgery clinic between the ages of 50 and 79 years. Serum glucose level was assessed after a 10-h fast and at 30, 60 and 120 min after a 75-g oral glucose challenge. Any patient with two serum glucose values > 140 mg/dl was considered to have a positive oral glucose tolerance test. Using duplex ultrasound, the brachial artery diameter (cm) and blood volume (ml/min) were assessed before and after tourniquet occlusion at each step of the oral glucose tolerance test. Paired and unpaired t-tests were used to evaluate the results, P < 0.05 was considered significant. Nine patients had abnormal oral glucose tolerance test for a prevalence of 39%. There was no significant difference in fasting glucose levels between positive and negative oral glucose tolerance test patients (97.4+/-16.7 versus 88.5+/-5.8, P = 0.23). Patients with a positive oral glucose tolerance test had impaired vasoactivity at fasting and at each step of the test with no significant changes in brachial artery diameter or blood flow in response to brachial artery occlusion. Patients with a negative oral glucose tolerance test exhibited increased brachial artery diameter at fasting in response to brachial artery occlusion (0.43+/-0.02 versus 0.46+/-0.02, P = 0.03), but not after oral glucose challenge. In patients with a negative oral glucose tolerance test, brachial artery flow volume increased significantly in response to hyperemia at fasting (240+/-61 versus 578+/-262, P = 0.001) and at 30 min after glucose intake (260+/-53 versus 358+/-72, P = 0.01). At 60 and 120 min after glucose intake, brachial artery flow volume did not significantly increase in response to brachial artery occlusion. These results indicate that individuals with PVD and normal fasting glucose levels have a high prevalence of positive oral glucose tolerance test (39%). Patients with normal fasting glucose levels and abnormal oral glucose tolerance test have impaired brachial artery vasoactivity at fasting and after oral glucose challenge, this is in contrast to patients with normal oral glucose tolerance test who have normal fasting hyperemic response to brachial artery occlusion. However, this normal brachial artery vasoactivity is lost in the negative oral glucose tolerance test group in response to oral glucose load. These results suggest that endothelial function in diabetics is impaired in the early stages of the disease even before overt hyperglycemia occurs. Tight control of blood glucose level in glucose-intolerant patients prior to occurrence of overt fasting hyperglycemia may prove protective.

Prosthetic bypass with a distal vein patch for limb salvage.

BACKGROUND: Certain patients require tibial bypass for limb salvage without adequate vein available as the conduit. Polytetrafluoroethylene (PTFE) bypasses result in decreased patency prompting the addition of venous tissue at the distal anastomosis as cuffs, collars, and boots. We assessed feasibility and graft patency of a distal vein patch (DVP) interposed between PTFE and the tibial artery. METHODS: Between 7/93 and 7/96, 148 tibial bypasses were performed with 25 (17%) using PTFE/DVP as the conduit. Patient demographics (n = 24) were 11 males and 13 females, mean age of 67, diabetes (n = 15, 57%), renal failure (n = 8, 31%), and excessive cardiac risk (n = 20, 83%). All patients had limb-threatening ischemia with rest pain in 14 (58%) and gangrene/nonhealing ulcer in 10 (42%). Lack of vein was due to previous failed bypass (15,63%), cardiac surgery (5,21%), and unsuitable vein (4,21%). Patients were discharged on coumadin with follow-up at 1 month, 6 months, and annually. RESULTS: PTFE/DVP bypasses originated from the CFA (13,48%), the SFA (3,11 %) and the external iliac artery due to previous groin dissection (9,41 %). Recipient arteries included anterior tibial (7), posterior tibial (8), and peroneal (10). Follow-up ranged from 1 to 36 months. Cumulative graft patency at 6 months and 3 years was 91% and 78%, respectively, by life table analysis. Limb salvage was 91%. CONCLUSION: These early data indicate that tibial bypass with PTFE/DVP as the conduit results in acceptable patency and limb salvage. In the patient without adequate vein, PTFE bypasses to tibial arteries for limb salvage may be improved with a distal vein patch.

Transforming growth factor beta 1 inhibits the proliferative effect of insulin on human infragenicular vascular smooth muscle cells.

PURPOSE: The distribution of atherosclerotic arterial disease in diabetes mellitus characteristically involves the infragenicular arterial tree including the anterior tibial, posterior tibial, and peroneal arteries. The proliferation of vascular smooth muscle cell (VSMC) is essential in the development of the atherosclerotic lesion. It has long been held that insulin plays a causative role in the formation of the atherosclerotic lesion in diabetes. We studied the role played by insulin in the proliferation of these cells in culture and the interaction of insulin with transforming growth factor beta 1 (TGF beta 1), a factor known for its possible inhibitory effects. METHODS: We have grown and characterized a line of VSMC harvested from atherosclerotic infragenicular arteries of human subjects undergoing below-knee amputation. The cultures were defined as being of VSMC origin by immunohistochemical staining with alpha-smooth muscle actin. Confluent cultures of passages 4 through 7 were seeded into six well plates at a density of 5000 cells/well. After serum deprivation the cells were exposed to insulin (100 ng/ml) alone or in combination with TGF beta 1 (6 ng/ml). RESULTS: Our findings indicate that a 48-hour incubation with insulin augments the proliferation of human infragenicular VSMC, producing a 207% increase in cell number when compared with control cells (11,328 +/- 686, n = 56 vs 3682 +/- 182, n = 87; p < 0.0001). The addition of TGF beta 1 in combination with insulin abolished the accelerated growth rate seen in test groups treated with insulin alone (3614 +/- 247, n = 32 vs 11,328 +/- 686, n = 56; p < 0.0001). CONCLUSION: These results strongly suggest that insulin is a potent stimulant of human infragenicular VSMC proliferation. The mitogenic effect of insulin is inhibited by TGF beta 1, producing proliferation rates comparable to those observed in control cells incubated with serum-free media.