Paul J. Gagne

Human Endothelial Progenitor Cells From Type II Diabetics Exhibit Impaired Proliferation, Adhesion, and Incorporation Into Vascular Structures

Background—The recent discovery of circulating endothelial progenitor cells (EPCs) has altered our understanding of new blood vessel growth such as occurs during collateral formation. Because diabetic complications occur in conditions in which EPC contributions have been demonstrated, EPC dysfunction may be important in their pathophysiology. Methods and Results—EPCs were isolated from human type II diabetics (n=20) and age-matched control subjects (n=20). Proliferation of diabetic EPCs relative to control subjects was decreased by 48% (P <0.01) and inversely correlated with patient levels of hemoglobin A1C (P <0.05). Diabetic EPCs had normal adhesion to fibronectin, collagen, and quiescent endothelial cells but a decreased adherence to human umbilical vein endothelial cells activated by tumor necrosis factor-&agr; (TNF-&agr;) (P <0.05). In a Matrigel assay, diabetic EPCs were 2.5 times less likely to participate in tubule formation compared with controls (P <0.05). Conclusions—These findings suggest that type II diabetes may alter EPC biology in processes critical for new blood vessel growth and may identify a population at high risk for morbidity and mortality after vascular occlusive events.

3D nongadolinium‐enhanced ECG‐gated MRA of the distal lower extremities: Preliminary clinical experience

To report our initial experience implementing a noncontrast‐enhanced electrocardiograph (ECG) gated fast spin echo magnetic resonance angiography (MRA) technique for assessment of the calf arteries.

Carotid-subclavian bypass: A twenty-two–year experience

PURPOSE A retrospective review of 124 patients who underwent carotid-subclavian bypass from 1968 to 1990 was done to assess primary patency and symptom resolution. METHODS Preoperative data included age, atherosclerosis risk factors, and indications for surgery. Perioperative data included mortality and morbidity rates and graft conduit. Postoperative follow-up assessed graft patency, resolution of symptoms, and late survival. RESULTS Age ranged from 42 to 78 years (mean 57.9). Indications for surgery were vertebrobasilar insufficiency in 24 (19%), extremity ischemia (EI) in 33 (27%), transient ischemic attacks (TIAs) in 13 (11%), both vertebrobasilar insufficiency and EI in 31 (25%), and both TIAs and EI in 23 (18%) patients. Graft conduits were polytetrafluoroethylene in 44 (35%) and Dacron in 80 (65%) cases. Concomitant ipsilateral carotid endarterectomy was done in 32 (26%) patients. During operation, death occurred in one patient (0.8%), and complications occurred in 10 (8%) patients. Thirty-day primary patency and symptom-free survival rates were 100%. Long-term follow-up ranging from 5 to 164 months was available for the 60 cases done between 1975 and 1990. Three grafts occluded at 30, 36, and 51 months after surgery for a primary patency rate of 95% at 5 and 10 years. Twenty-two patients died, yielding survival rates of 83% at 5 years and 59% at 10 years. Symptom recurrence occurred in six (10%) patients from 9 to 66 months after surgery. The symptom-free survival rate was 98% at 1 year, 90% at 5 years, and 87% at 10 years. Symptoms recurred in three patients with occluded grafts and three with patent grafts. The preoperative symptoms of drop attacks and TIAs did not recur. EI recurred in 5% and was noted only in the presence of graft occlusion. Dizziness recurred in 17% of patients admitted with this symptom and was observed despite graft patency. CONCLUSION Carotid-subclavian bypass was a safe and durable procedure for relief of symptomatic occlusive disease of the subclavian artery. Long-term symptomatic relief appeared particularly likely in patients with drop attacks or upper extremity ischemia.

Long-term follow-up of patients undergoing reoperation for recurrent carotid artery disease

PURPOSE We examined the perioperative course and long-term fate of individuals who required reoperation for recurrent carotid artery disease. METHODS The records of 2289 patients undergoing 2961 consecutive operations during a 22-year period were reviewed. Forty-two patients (1.8%) who underwent reoperations were studied. Forty-seven redo carotid artery reconstructions were performed on these 42 patients for neurologic symptoms or asymptomatic high-grade stenosis. Long-term follow-up was obtained on 41 of 42 patients (mean 54 months; range 9 to 202 months). RESULTS The forty-seven reoperations consisted of endarterectomy with patch angioplasty (n = 36), saphenous vein or polytetrafluoroethylene interposition graft (n = 7), or simply vein or polytetrafluoroethylene patch angioplasty (n = 4). There were no perioperative strokes or deaths. Three patients had perioperative transient ischemic attacks and two had cranial nerve injuries. The incidence of late failure after secondary surgery was 19.5% (8/41 patients). These failures consisted of one stroke, three transient ischemic attacks, and four asymptomatic occlusions. One tertiary carotid artery reconstruction was performed for a restenosis at the site of the secondary reconstruction. CONCLUSION The factors responsible for the high incidence of late failures after secondary carotid artery reconstruction are unclear. Reoperation for recurrent carotid artery disease appears less durable than primary carotid endarterectomy. Close postoperative surveillance is recommended after carotid artery reoperation.

A model for predicting occult carotid artery stenosis: screening is justified in a selected population

OBJECTIVES The diagnosis and treatment of carotid artery disease is an integral part of stroke prevention. However, a population of patients who would benefit from screening for carotid artery stenosis has not been well defined. As part of an institutional stroke-screening program, a modified, rapid duplex scan was developed to evaluate patients for occult carotid stenosis. The goal of this study was to evaluate risk factors predictive of carotid stenosis in a selected population, and to identify patients who would benefit from carotid screening. METHODS Patients were eligible for the study if they were >60 years of age and had a history of hypertension, heart disease, current smoking, or family history of stroke. A modified carotid duplex scan that had been previously validated against formal duplex scanning was utilized; this involved visualization of the carotid bulb and proximal internal carotid artery where Doppler flow velocities were obtained and recorded. RESULTS Screening was performed on 394 patients. Thirty-eight patients (9.6%) had either unilateral or bilateral carotid stenosis of > or =50%. Risk factors evaluated included smoking, hypertension, cardiac disease, or hypercholesterolemia. If none of these risk factors was present, the incidence of carotid stenosis was 1.8%. This increased to 5.8% with one risk factor, 13.5% with two risk factors, and 16.7% with three risk factors. Two of three patients with all four risk factors had carotid stenosis (66.7%). Logistic regression and prespecified contrast statements for multiple comparisons were used to assess the relationship between the presence of risk factors and occult carotid artery stenosis. The presence of any one of these risk factors was associated with a statistically significant increase in the presence of occult carotid stenosis (P <.01). This was also statistically significant for the presence of any two risk factors (P <.01) or three risk factors (P <.05). CONCLUSION The prevalence of carotid stenosis significantly increases with the presence of one or more identifiable demographic risk factors in a selected population. Assuming the diagnosis and treatment of carotid stenosis are fundamental to stroke prevention, screening for carotid artery disease is justified in this group of patients.

Temporal expression and activation of matrix metalloproteinases-2, -9, and membrane type 1-matrix metalloproteinase following acute hindlimb ischemia.

OBJECTIVE Matrix metalloproteinase (MMP) activity is essential for remodeling of ischemic tissue. The murine hindlimb ischemia model exhibits tissue remodeling including revascularization in part due to angiogenesis. MMP-2 and -9 are type IV collagenases necessary for basement membrane degradation as a part of extracellular matrix remodeling and angiogenesis. Polymorphonuclear leukocytes (PMNs) contain MMP-9, and in the presence of membrane type 1 (MT1)-MMP, are able to activate proMMP-2 in vitro. Activation of MMP-2 and -9 may be essential in ischemic limbs both for tissue remodeling and revascularization via angiogenesis. We hypothesized that MMP-2 and -9 would be activated following acute hindlimb ischemia (HI), and this activation would be temporally related to PMN infiltration. DESIGN OF STUDY HI was achieved by unilateral femoral artery ligation in 20 FVB/N mice. Five mice underwent sham operation without hindlimb ischemia. Gastrocnemius muscle was harvested from both hindlimbs at 1, 3, 14, and 30 days following ligation and assayed for MMP-2, -9 (gelatin zymography), and MT1-MMP (Western blotting). MMP-2 and -9 expression and activation were analyzed by gelatin zymography and quantified by densitometry with NIH Image Analysis software. Neutrophils per high power field were counted. The results were expressed as a ratio of ischemic to nonischemic limbs and compared at each time point using ANOVA. RESULTS Zymographic analysis revealed a 212% increase in active MMP-2 3 days postligation (P <.05). Active MMP-9 reached its maximum level (800% over baseline) on postoperative day 3 and continued to be elevated on day 14 (737% over baseline) (P <.05). The increase in active MMP-2 and -9 levels paralleled PMN infiltration that also peaked 3 days postligation (1184% over baseline) (P <.05). PMN count, MMP-2, and -9 all returned to baseline levels by postoperative Day 30. MT1-MMP was present in tissue samples from all time points as confirmed by Western blot. CONCLUSIONS Limb ischemia causes an early activation of MMP-2 and -9 in temporal relation to PMN infiltration. HI may prime PMNs, leading to their sequestration in ischemic tissue. Primed PMNs, along with constitutively expressed MT1-MMP, may activate MMPs-2 and -9 and enable tissue remodeling essential for limb revascularization and angiogenesis.

Can the NASCET technique for measuring carotid stenosis be reliably applied outside the trial

PURPOSE The North American Symptomatic Carotid Endarterectomy Trial (NASCET) and the Asymptomatic Carotid Artery Study (ACAS) both confirmed the effectiveness of carotid endarterectomy for preventing stroke in patients who have significant carotid stenosis. A uniform technique for measuring carotid stenosis from an arteriogram (% stenosis = [1 - minimum residual lumen/normal distal cervical internal carotid artery diameter] x 100) was used in both trials, with reproducibility internally validated. The reliability of this measurement when used outside the trials for defining carotid stenosis has not been validated. Imprecise calculation of carotid stenosis can result in a 50% overestimation of significant carotid disease and potential overuse of carotid surgery. This is a prospective study of the reliability of carotid stenosis measurements performed by practicing physicians of different specialties and different levels of clinical experience. METHODS Two vascular surgeons and two interventional radiologists (one resident and one staff member per specialty), blinded to results, calculated the percent stenosis from 219 consecutive arteriograms performed to evaluate extracranial carotid artery occlusive disease; 72 random films were reread by each individual. The interpretations were grouped as < 60% or > or = 60% stenosis (ACAS) and as < 30%, 30% to 69%, and > or = 70% stenosis (NASCET). Interobserver and intraobserver agreement were analyzed with the kappa statistic and Pearson correlation coefficients. RESULTS Interobserver reliability in categorizing carotid stenosis revealed excellent agreement for both ACAS (kappa = 0.825 to 0.903) and NASCET groups (kappa = 0.729 to 0.793). Interobserver correlation coefficients ranged from 0.91 to 0.95. Intraobserver agreement was also highly reproducible for both the ACAS (kappa = 0.732 to 0.970) and NASCET categories (kappa = 0.634 to 0.805). Intraobserver correlation coefficients ranged from 0.89 to 0.95. CONCLUSION The NASCET technique for quantification of carotid stenosis can be easily learned by physicians and reliably implemented for appropriate identification of candidates for carotid endarterectomy.

Controversies in the Management of Type 11 “Branch” Endoleaks Following Endovascular Abdominal Aortic Aneurysm Repair

Successful endovascular aortic aneurysm repair (EVAR) is often defined as complete exclusion of blood flow within the aneurysm sac. Perigraft flow, also known as endoleak, is the most common complication following EVAR. Attachment site related endoleaks (type 1) are generally considered to warrant some form of intervention due to the belief that they represent a risk for future rupture. Management of type 11 endoleaks, also known as branch or collateral endoleaks, is more controversial. Some advocate a policy of watchful-waiting whereas others treat all type 11 endoleaks as soon as they are discovered. The following review explores the controversies pertaining to the management, diagnosis and surveillance imaging, and treatment of type 11 endoleaks.

Causes of perioperative stroke after carotid endarterectomy: Special considerations in symptomatic patients

In order to maximize the efficacy of carotid endarterectomy (CEA), the rate of perioperative stroke must be kept to a minimum. A recent analysis of carotid surgery at our institution found that most perioperative strokes were due to technical errors resulting in thrombosis or embolization. From 1992 through 1997 we have performed nearly 1200 additional CEAs; the purpose of this study was to examine recent trends in the causes of perioperative stroke, with specific attention to differences in symptomatic and asymptomatic patients. The records of 1041 patients undergoing 1165 CEAs were reviewed from a prospectively compiled database. Analysis of these data showed that a history of preoperative stroke appears to increase the risk of perioperative stroke after CEA. Surgical factors associated with perioperative stroke include an inability to tolerate clamping, use of an intraarterial shunt, and having surgery performed under general anesthesia; these factors are clearly interrelated and only the use of intraarterial shunting remains a risk factor by multivariate analysis. Over half of all perioperative strokes (54%) appear to be caused by intraoperative or postoperative thrombosis and embolization. The patient requiring use of intraarterial shunting and/or with a preoperative stroke most likely has a significant watershed area of brain at increased risk of infarction. However, technical errors are still the most common cause of perioperative stroke in these high-risk patients. Such high-risk patients may manifest clinical stroke from small emboli that may be tolerated by asymptomatic clamptolerant patients. Technical precision and appropriate cerebral protection are particularly critical for successful outcomes in high-risk patients.

Disruption of Endothelial Cell Interactions with the Novel HU177 Cryptic Collagen Epitope Inhibits Angiogenesis

Purpose: The importance of cellular communication with the extracellular matrix in regulating cellular invasion is well established. Selective disruption of communication links between cells and the local microenvironment by specifically targeting non-cellular matrix-immobilized cryptic extracellular matrix epitopes may represent an effective new clinical approach to limit tumor-associated angiogenesis. Therefore, we sought to determine whether the HU177 cryptic collagen epitope plays a functional role in regulating angiogenesis in vivo. Experimental Design: We examined the expression and characterized the HU177 cryptic collagen epitope in vitro and in vivo using immunohistochemistry and ELISA. We examined potential mechanisms by which this cryptic collagen epitope may regulate angiogenesis using in vitro cell adhesion, migration, proliferation, and biochemical assays. Finally, we examined the whether blocking cellular interactions with the HU177 cryptic epitope plays a role in angiogenesis and tumor growth in vivo using the chick embryo model. Results: The HU177 cryptic epitope was selectively exposed within tumor blood vessel extracellular matrix, whereas little was associated with quiescent vessels. An antibody directed to this cryptic site selectively inhibited endothelial cell adhesion, migration, and proliferation on denatured collagen type IV and induced increased levels of cyclin-dependent kinase inhibitor p27KIP1. Systemic administration of mAb HU177 inhibited cytokine- and tumor-induced angiogenesis in vivo. Conclusions: We provide evidence for a new functional cryptic regulatory element within collagen IV that regulates tumor angiogenesis. These findings suggest a novel and highly selective approach for regulating angiogenesis by targeting a non-cellular cryptic collagen epitope.