Site Of Stenosis Research Articles

Clinical Presentation and Cardiovascular Risk Profiles in Patients With Left Main Coronary Artery Disease in a Middle Eastern Country

We evaluated the prevalence and clinical profile of patients with left main coronary artery disease (LMCA) in Qatar between 2006 and 2010. Patients were divided into 2 groups: patients with LMCA and patients without LMCA but had severe 3-vessel disease (VeD) eligible for surgical revascularization. Among 7000 patients who underwent coronary angiography, 210 patients had significant LMCA and 200 patients with severe 3VeD were matched for age and sex. Diabetes mellitus and hypertension were comparable in the 2 groups. Presentations with myocardial infarction or heart failure were comparable in both groups. Isolated LMCA was 4-fold higher in women (P = .02). Dyslipidemia and smoking were more prevalent in patients with distal and proximal lesions, respectively. Renal failure was independent predictor of LMCA (adjusted odds ratio: 2.6; 95% confidence interval: 1.43-4.69). One-year mortality was higher in LMCA (P = .01). The LMCA carries high mortality. Certain cardiovascular risk factors were important predictors of stenosis site.

Multimodal CT to Differentiate Acute Ischemic Stroke From Stroke Mimics

A 64-year-old man was evaluated in the emergency department after reportedly being found unconscious and “stiff.” A “stroke alert” was called from the field prior to arrival. At the time of initial evaluation, collateral history was not available. On examination, the patient was agitated, did not follow commands, and had a left gaze preference. There were symmetric and semipurposeful movements of the limbs. The patient was sedated and intubated to facilitate additional testing. Head computed tomography (CT) showed no hemorrhage. Computed tomography angiography (CTA) demonstrated diminished flow in the left hemispheric convexity branches without the evidence of proximal occlusion. CT Perfusion (CTP) showed reduced cerebral blood volume, cerebral blood flow, and increased time to peak perfusion involving the left cerebral hemisphere diffusely. The urine toxicology was positive for methamphetamine and cannabis. No thrombolytic therapy was administered and the patient recovered over the subsequent 24 hours. Multimodal CT has been adopted by many stroke centers as the neuroimaging modality of choice to guide acute stroke treatment. In this patient, the absence of proximal vascular occlusion and the diffusely reduced left-hemisphere blood flow and blood volume were suggestive of postictal hypoperfusion rather than focal cerebral ischemia.1 The CTP images for this patient are shown in Figure 1 (A-C), and they demonstrate the typical findings for postictal hypoperfusion, which includes holo-hemispheric involvement, crossing of multiple vascular distributions, sparing of the basal ganglia, and predilection for the smaller cortical vessels.2 This patient’s left gaze preference is therefore explained in the context of loss of cortical function in the hypoperfused hemisphere postictally. In acute ischemic stroke, the CTP would show an area of decreased relative cerebral blood flow (CBF) and relative cerebral blood volume (CBV) with increased time to peak (TTP) at the site of focal stenosis or occlusion surrounded by an area of decreased rCBF, increased rCBV, and increased TTP due to autoregulation. Additionally, there would be no sparing of any structures within the affected vascular distribution. Figure 1. Demonstrated is reduced cerebral blood flow (A) on the order of 10-30 mL/100 mg tissue per minute in the entire left hemisphere across the anterior, middle, and posterior cerebral artery territories with relative sparing of the basal ganglia. Likewise, ... This case illustrates the diagnostic utility of CTP in differentiating between stroke and stroke mimic when collateral history is limited or the examination is confounded.

The maximum necrotic core area is most often located proximally to the site of most severe narrowing: a virtual histology intravascular ultrasound study

Previous angiographic studies have shown that almost two-thirds of vulnerable plaques are located in non-obstructive lesions. Possibly, the maximum necrotic core (Max NC) area is not always identical to the site of most severe stenosis. Therefore, the purpose of this study was to evaluate the potential difference in location between the maximum necrotic core area and the site of most severe narrowing as assessed by virtual histology intravascular ultrasound (VH IVUS). Overall, 77 patients (139 vessels) underwent VH IVUS. The Max NC site was defined as the cross section with the largest necrotic core area per vessel. The site of most severe narrowing was defined as the minimum lumen area (MLA). Per vessel, the distance from both the Max NC site and MLA site to the origo of the coronary artery was evaluated. In addition, the presence of a virtual histology-thin cap fibroatheroma (VH-TCFA) was assessed. The mean difference (mm) between the MLA site and Max NC site was 10.8 ± 20.6 mm (p < 0.001). Interestingly, the Max NC site was located at the MLA site in seven vessels (5%) and proximally to the MLA site in 92 vessels (66%). Importantly, a higher percentage of VH-TCFA was demonstrated at the Max NC site as compared to the MLA site (24 vs. 9%, p < 0.001). In conclusion, the present findings demonstrate that the Max NC area is rarely at the site of most severe narrowing. Most often, the Max NC area is located proximal to the site of most severe narrowing.

Abstract 167: High Resolution MR Imaging Of Intracranial Arterial Vessel Walls In Moyamoya Disease

Background: The pathogenesis of the primary occlusive vasculopathy or vasculopathies involving the basal arteries in patients with moyamoya phenomenon is unknown. Newer Magnetic Resonance (MR) techniques have been developed to characterize atheroma in the arterial wall. This is a pilot study of vessel wall imaging using high field-strength, high-spatial resolution MR techniques in patients with moyamoya. Method: Twenty patients with idiopathic moyamoya were recruited. MR imaging was performed on a 3T head MR system. Imaging included a time-of-flight (TOF) magnetic resonance angiography (MRA) and high-resolution T2-weighted sequences through the circle of Willis. Images were inspected for evidence of an intramural occlusive lesion or atheroma. Vessel wall thickness of the internal carotid artery (ICA) at the points of maximal narrowing as determined by catheter angiography was compared to the wall thickness of the distal basilar artery in each patient. Vessel wall thickness was calculated as the difference between the intraluminal diameter measured on MRA and the extraluminal diameter measured on the T2 image, divided by 2. Results: All patients demonstrated diminished arterial diameters on T2 imaging corresponding to sites of luminal stenosis on catheter angiography and time-of-flight MRA sequences. No focal or diffuse intramural thickening was subjectively observed at the sites of stenosis. Objective measures of vessel wall thickness found no difference between the sites of maximal stenosis of involvded vessels and univolved vessels of similar diameter. The mean thickness of the basilar artery was 0.66 mm (standard deviation 0.14). The mean thickness of the diseased ICA was 0.61 mm (s.d. 0.22) in patients with bilateral disease. The mean thickness of the uninvolved ICA in patients with unilateral disease was 0.69 mm (s.d. 0.07). The figure includes sequential high resolution T2 images of a patients with unilateral right sided moyamoya phenomenon (a,b) demonstrating a small right ICA (arrow) compared to the unaffected contralateral ICA. TOF MRA (c,d) illustrate luminal stenosis without evidence of intramural thickening. Multiple moyamoya collateral vessels are also evident (c). Conclusion: These data suggest that the pathological process underlying vessel narrowing and occlusion is not a static structural lesion in the vessel wall leading to luminal compromise. In addition, these imaging techniques may be useful in distinguishing idiopathic basal occlusive disease from other processes such as atherosclosis.

Abstract 1905: Arterial Spin-Labeled MRI of Leptomeningeal Collateral Perfusion in Acute Ischemic Stroke

Background: Leptomeningeal collaterals and associated cortical perfusion downstream from a proximal arterial occlusion or stenosis are potent predictors of outcome in acute stroke. Arterial spin-labeled (ASL) MRI may depict delayed arterial transit effects (DATE) of these collaterals and cerebral blood flow (CBF), utilizing noninvasive techniques without the use of contrast. We conducted a prospective validation study of ASL DATE and CBF as biomarkers of leptomeningeal collateral perfusion compared to digital subtraction angiography (DSA) and dynamic susceptibility contrast (DSC) perfusion MRI in acute ischemic stroke. Methods: Consecutive anterior circulation acute ischemic stroke patients admitted during a 1-year period were evaluated with pseudo-continuous ASL, DSA and DSC perfusion MRI within 12 hours of symptom onset. ASL DATE extent was scored using a 3-point scale and angiographic collaterals on the DSA graded using the ASITN/SIR collateral score. ASL CBF and DSC CBF maps were co-registered to derive comparative ROI statistics on perfusion in the symptomatic territory. ASL CBF lesions &lt; 15 mL/100 g/min were used to measure DSC CBF values within coregistered ROIs. Results: Among 39 patients meeting entry criteria, mean age was 66±19 years and 51% were male. All 39 patients were imaged with ASL and DSA, with DSC perfusion MRI in a subset of 27. Sites of vascular occlusion or stenosis were: terminal ICA - 10, M1 MCA - 20, M2 MCA - 5 and more distal MCA - 4. ASL DATE scores ranged from 0-2, with a median of 1. DSA collateral grade ranged from 0-4, with a median of 2. Overall, there was strong correlation (r=0.702, p&lt;0.001) between the ASL and DSA measures of leptomeningeal collateral supply. In the downstream territory from these leptomeningeal collaterals, ASL CBF and DSC CBF maps both revealed hypoperfusion in regions that closely matched. Only limited correlation, however, was noted between exact ASL CBF and DSC CBF values within the co-registered ROIs. Conclusions: ASL MRI provides an accurate, noninvasive measure of leptomeningeal collateral perfusion in acute ischemic stroke due to anterior circulation stenosis or occlusion. ASL CBF measures of collateral perfusion likely are arterially weighted, like DSA collateral grades, and unlike conventional DSC perfusion MRI CBF values.

Non-invasive imaging of atherosclerosis.

Atherosclerosis is an inflammatory disease that causes most myocardial infarctions, strokes, and acute coronary syndromes. Despite the identification of multiple risk factors and widespread use of drug therapies, it still remains a global health concern with associated costs. It is well known that the risks of atherosclerotic plaque rupture are not well correlated with stenosis severity. Lumenography has a central place for defining the site and severity of vascular stenosis as a prelude to intervention for relief of symptoms due to blood flow limitation. Atherosclerosis develops within the arterial wall; this is not imaged by lumenography and hence it provides no information regarding underlying processes that may lead to plaque rupture. For this, we must rely on other imaging modalities such as ultrasound, computed tomography, magnetic resonance imaging, and nuclear imaging methods. These are capable of reporting on the underlying pathology, in particular the presence of inflammation, calcification, neovascularization, and intraplaque haemorrhage. Additionally, non-invasive imaging can now be used to track the effect of anti-atherosclerosis therapy. Each modality alone has positives and negatives and this review will highlight these, as well as speculating on future developments in this area.

Natural History of Upper Limb Arterio-Venous Fistulae for Chronic Hemodialysis

Arterio-venous fistulae (AVF) for hemodialysis are prone to problems, ultimately leading to failure of the fistulae. Our aim was to determine the site and time to first stenosis and time to and factors influencing AVF failure for radio-cephalic (RC), brachio-cephalic (BC), and transposed brachio-basilic (BB) AVF. Retrospective analysis of native AVF constructed within a single vascular unit between January 2002-December 2008. Patients followed up to the end points of death, AVF failure or end of study period. Data collected included: age, sex, AVF type, time and site of first stenosis and time to failure. The relationship between fistula type, stenosis, and failure were examined. In total, 398 native AVF were included in the study (91 RC, 208 BC, and 99 BB), with a mean age of 66 years. A total of 215 (54%) AVF developed a flow limiting stenosis, and over time 151 (40%) AVF failed. Stenoses developed significantly earlier in RC AVF (median 113 days) compared to BC (median 277 days), compared to BB (median days 414), P=.029. There was no statistically significant difference in time to failure (RC median 1344 days; BC median 1576 days; BB median 1159 days), P=.673. The presence of stenosis was the only variable found to have a significant impact on AVF failure in multivariate analysis. Type of upper limb fistula did not impact on failure rates. Flow limiting stenoses impacted on fistula failure.

Computational Fluid Dynamics Analysis of Pulsatile Blood Flow Behavior in Modelled Stenosed Vessels with Different Severities

This study focuses on the behavior of blood flow in the stenosed vessels. Blood is modelled as an incompressible non‐Newtonian fluid which is based on the power law viscosity model. A numerical technique based on the finite difference method is developed to simulate the blood flow taking into account the transient periodic behaviour of the blood flow in cardiac cycles. Also, pulsatile blood flow in the stenosed vessel is based on the Womersley model, and fluid flow in the lumen region is governed by the continuity equation and the Navier‐Stokes equations. In this study, the stenosis shape is cosine by using Tu and Devil model. Comparing the results obtained from three stenosed vessels with 30%, 50%, and 75% area severity, we find that higher percent‐area severity of stenosis leads to higher extrapressure jumps and higher blood speeds around the stenosis site. Also, we observe that the size of the stenosis in stenosed vessels does influence the blood flow. A little change on the cross‐sectional value makes vast change on the blood flow rate. This simulation helps the people working in the field of physiological fluid dynamics as well as the medical practitioners.

Papaverine-Induced Polymorphic Ventricular Tachycardia in Relation to QTU and Giant T-U Waves in Four Cases

Papaverine is used for the evaluation of functional status of the coronary arteries but it may provoke severe ventricular tachyarrhythmias (VTAs). This study compared the clinical and ECG characteristic of patients with papaverine-induced VTAs. The study involved 25 patients who underwent a fractional flow reserve (FFR) study. FFR was determined as the ratio of blood pressure at the distal and the proximal site of stenosis after intracoronary papaverine administration at 12 mg into the left and 8 mg into the right coronary artery. The QT and QTU intervals were measured manually in the limb leads and in the precordial leads, respectively and corrected by the R-R interval to obtain QTc and QTUc. The clinical and ECG data were compared between the patient groups with and without VTAs. After papaverine administration into the left (20), right (3) or both coronary arteries (2), the RR interval shortened, but non-significantly however, the QT interval (and QTc) and the QTU interval (and QTUc) were significantly prolonged. VTAs developed in four women: torsade de pointes in 3 followed by ventricular fibrillation and ventricular premature beats in 1 patient. After papaverine administration, QTU and QTUc were more prolonged in women than men and in patients with VTAs compared to those without. Just prior to VTAs, giant T-U waves were observed. Intracoronary papaverine was used to determine FFR which may induce VTAs. VTAs developed only in women and they were closely related to prolongation of the QTU intervals with prominent T-U waves.

Safety and efficacy of extractible self-expandable metal stents in the treatment of Crohnʼs disease intestinal strictures: A prospective pilot study

Endoscopic management of Crohn's disease (CD) intestinal strictures with balloon dilation is effective; however, recurrences are frequent and require further dilations or surgery. The use of extractible metallic stents may be as effective as balloon dilation with fewer recurrences. The aim was to investigate in a prospective pilot study the feasibility and clinical effectiveness of the use of extractible stents in the treatment of CD intestinal strictures. In two tertiary referral centers, quiescent CD patients except for obstructive symptoms associated with intestinal stenosis of less than 50 mm length on enterography were eligible for transitory stent placement, initially planned to be retrieved after 8 weeks, which was secondarily reduced to 4 weeks after patient 3. Eleven patients (six males, five females, median age 34 years [range 18-66]) were prospectively included. The sites of intestinal stenosis were an ileocolonic anastomosis, an ileosigmoidic anastomosis, and the surgically untreated terminal ileum in eight, one, and two patients, respectively. Stent placement was technically successful in 10 patients. Obstructive symptoms were relieved in 6 out of 10 patients. Two patients needed surgery related to the procedure. Six downstream migrations were observed. Only one patient could have the stent extracted as scheduled on day 28 and remains symptom-free after 73 months of follow-up. Even if stenting appears an effective technique in treating symptomatic CD intestinal strictures, the procedure is associated with a prohibitively high rate of spontaneous migrations and complications.

Abstract 9917: The Site of Greatest Vulnerability is Most Often Located Proximally to the Site of Most Severe Narrowing: A Virtual Histology Intravascular Ultrasound Study

Introduction: Previous angiographic studies have shown that almost two-thirds of vulnerable plaques are located in non-obstructive lesions. However, the spatial relationship between the location of most severe narrowing and vulnerable rupture sites has not been fully elucidated. Probably, the site of greatest vulnerability is not always identical to the site of most severe stenosis. Therefore, the aim of the present study was to assess the spatial relationship between the location of the site of greatest vulnerability and the location of most severe narrowing with VH IVUS. Methods: Overall, 77 patients (139 vessels) underwent VH IVUS. The site of greatest vulnerability was defined as the cross-section with the largest necrotic core area per vessel, the maximum necrotic core (Max NC) site. The site of most severe narrowing was defined as the minimum lumen area (MLA). Per vessel the distance from both the Max NC site and MLA site to the origo of the coronary artery was evaluated. In addition, the presence of a thin cap fibroatheroma (TCFA) was assessed. Results: The mean difference (mm) between the MLA site and Max NC site was 10.8±20.6mm (P&lt;0.001). Interestingly, the Max NC site was located at the MLA site in 7 vessels (5%) and proximally to the MLA site in 92 vessels (66%). Besides, a higher % of TCFA was demonstrated at the Max NC site as compared to the MLA site (24% versus 9%, P&lt;0.001). Conclusion: The present findings demonstrate that the site of greatest vulnerability is rarely at the site of most severe narrowing. Most often, the site of greatest vulnerability is located proximally to the site of most severe narrowing. Furthermore a higher percentage of TCFA (plaque phenotype with high-risk of rupture) was demonstrated at the site of greatest vulnerability. Figure 1 Difference in distance (mm) and distribution between Max NC site and MLA site. In the majority of vessels the site of Max NC is located proximal to site of MLA.

Visualization of Internal Carotid Artery Atherosclerotic Plaques in Symptomatic and Asymptomatic Patients: A Comparison of Optical Coherence Tomography and Intravascular Ultrasound

OCT has been reported as a high-resolution imaging tool for characterizing plaque in the coronary arteries. The present study aimed to evaluate the ability of OCT to visualize carotid artery plaques compared with that of IVUS in asymptomatic and symptomatic patients. OCT was performed for 34 plaques (17 symptomatic, 17 asymptomatic) in 30 patients during CAS under a proximal cerebral protection method. OCT was performed before balloon angioplasty and after stent placement. IVUS was also performed just after OCT. No technical or neurologic complications were encountered by using OCT. An inner catheter was used in 12 of 34 procedures (35.3%) for advancing the OCT image wire beyond the site of stenosis. OCT clearly visualized intraluminal thrombus in 15 of 34 plaques (44.1%), whereas IVUS detected a thrombus in 1 plaque (2.9%, P < .001). Neovascularization was demonstrated in 13 of 34 plaques (38.2%) by OCT, but not by IVUS (0%, P < .001). Intraluminal thrombus was more frequently observed in symptomatic plaques (13 of 17, 76.5%) than in asymptomatic plaques (2 of 17, 11.8%; P < .001). Interobserver and intraobserver variability with OCT diagnosis was excellent for thrombus, ulceration, neovascularization, and lipid pool. The present findings suggest that OCT can safely and precisely visualize human carotid plaques during CAS and that intraluminal thrombus and neovascularization are more frequently detected in symptomatic plaques.

Simultaneous resection of Barrett's esophageal cancer and severe stenosis caused by reflux esophagitis

A 60-year-old woman presented with dysphagia. Upper endoscopy revealed severe stenosis in Barrett’s esophagus with the internal diameter narrowed to 8 mm (Fig. 1). Contrast-enhanced CT ruled out metastasis. Tongueshaped brownish areas, where adenocarcinoma had been diagnosed, were approximately 5 to 7 mm in diameter. ESD extending 5 cm in the longitudinal direction was performed to resect the adenocarcinoma and the nearcircumferential stenosis site. Considering the severe fibrosis present, surgical entry was made 3 cm from the proximal end. At the stenosis site, EUS (20 MHz) revealed an intact submucosal layer around 0.5 mm of the circumference. In a retroflexed view from the stomach, we made an incision on the distal side of the stenosis. By advancing the endoscope into the submucosal layer by using the tunnel technique, we observed the most severe scarring (Fig. 2). Circumferential resection was completed (Fig. 3). Postoperative pathology revealed high-grade dysplasia and Barrett’s well-differentiated adenocarcinoma (Fig. 4). Kenacort was applied, and balloon dilation was performed on postoperative day (POD) 5 to prevent stenosis. The muscularis was exposed over the ulcer surface, and it was possible to permeate the gel into the remaining muscularis by expanding the balloon. Granulation tissue accompanied by extensive microvasculature was observed by magnified narrow-band imaging endoscopy on POD 12. By POD 15, granulation tissue was replaced by regenerating epithelium, with no post-ESD stricture formation apparent. On POD 60, Gastrografin contrast imaging confirmed smooth passage past the post-ESD lesion, and additional balloon dilation (to 18 mm) was performed. No stenosis or clinical symptoms were apparent at POD 90. n

Colon Lymphoma Mimicking Severe Ischemic Colitis

Purpose: A 65-year-old male presented with weight loss, fever and night sweats. He reported mild diarrhea and left lower quadrant abdominal pain. The initial workup revealed left-sided colitis and multiple small ulcers on colonoscopy, and the biopsies showed nonspecific colitis. A repeat colonoscopy revealed similar findings. Two months later he presented to our institution with hematochezia and progressive anemia, with a hemoglobin of 7.7 mg/dl. Colonoscopy revealed a 3 x 4 cm ischemic-appearing sigmoid ulcer with a necrotic base (Figure 1, Panel A) at 25 cm from the anal verge. These findings, and lack of bleeding while obtaining biopsies, were suggestive of ischemic colitis. However, histopathology revealed lymphoepithelial lesions (Figure 2, Panel A), and a clonal population of cells was positive for CD10 and CD20 (Figure 2, Panel B), confirming large-B-cell non-Hodgkin's lymphoma. A PET scan demonstrated stage IV disease with bone and adrenal involvement. After 6 cycles of chemotherapy with rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone (R-CHOP), his PET scan showed complete resolution of his disease. A colonoscopy done after 7 months showed a 5 mm area of stenosis at the 25 cm position, corresponding to the prior sigmoid ulcer. The ulceration was significantly reduced in size (Figure 1, Panel B). Balloon dilatation was performed at the stenosis site, and biopsies obtained during the procedure showed no evidence of malignancy. Diffuse large-B-cell lymphoma can occur anywhere in the GI tract. Patients tend to present with more systemic symptoms, a more advanced stage at diagnosis, and have a worse prognosis. Colonoscopy with biopsies is the principle diagnostic modality. The usual treatment is combination chemo-immunotherapy, and selected patients may be candidates for a trial of H pylori eradication. Considering lymphoma as a differential diagnosis in the workup of ischemic colitis with systemic symptoms may result in earlier recognition and a more favorable outcome.Figure 1: Sigmoid ulcer before (A) and after (B) chemotherapy. Figure 2: Histopathology showing lymphocytic infiltration (A) and positive immune staining for B lymphocytes (B).

Thin Bronchoscope for Evaluating Stenotic Airways during Stenting Procedures

Background: Flexible bronchoscopy can play an important role in the evaluation of an airway lumen during therapeutic bronchoscopic procedures. Despite its potential usefulness, however, evaluation with a standard-sized bronchoscope, which cannot pass completely through a severely stenosed airway, is often unsatisfactory. Objectives: This study aimed to evaluate the usefulness of prototype thin bronchoscopes for assessing stenotic airways during stenting procedures. Methods: Forty-six patients with central airway stenosis requiring stent implantation were enrolled in this prospective study. After inserting a rigid bronchoscope under general anesthesia, a flexible bronchoscopic evaluation using a 5.9- or 6.0-mm standard bronchoscope was performed, followed by evaluation using a prototype 3.4- or 3.5-mm thin bronchoscope for airways beyond the site of stenosis, which could not be visualized by the standard bronchoscope. Results: A standard bronchoscope could not pass through the stenotic airway in 15 of 46 patients (33%). On univariate analysis, the grade of stenosis (p < 0.001), the presence or absence of atelectasis (p = 0.04) and the presence or absence of viscous secretions (p = 0.02) were related to the rate of successful passage by a standard bronchoscope. On multivariate analysis, only the grade of stenosis remained independently associated with the success rate. In 12 of the 15 patients (80%), the airway lumen beyond the stenotic lesion, which could not be reached by a standard bronchoscope, was successfully visualized and evaluated with a thin bronchoscope. No significant complications were associated with the procedures. Conclusion: The thin bronchoscope can be a useful tool for evaluating a severely stenosed airway during the stenting procedure.

An Unusual Cause of Venous Hypertension After Dialysis Access Creation

Venous hypertension after creation of arteriovenous fistula or arteriovenous shunt occurs in approximately 10-15% of patients (Kojecky etal., Biomed Papers, 2002;146:77-79; Criado etal., Ann Vasc Surg 1994;8:530-535). Its etiology is commonly stenosis and/or thrombosis of the central venous system secondary to previous catheterization with subsequent development of venous hypertension after the arteriovenous connection is made. Treatment strategies often involve venography to determine the site of venous stenosis and/or occlusion centrally and subsequent endovascular recanalization of the stenotic or occluded veins. In this article, we report a case of venous hypertension in a 76-year-old man who presented with a swollen arm after placement of an arteriovenous fistula. In this circumstance, venography revealed extrinsic compression of the subclavian vein at the level of the first rib, the anatomic abnormality seen in venous thoracic outlet syndrome. In this report, we describe surgical and endovascular management of this patient, and review the literature on the causes of central vein stenosis discovered after creation of dialysis access.

Resting coronary flow velocity in the functional evaluation of coronary artery stenosis: study on sequential use of computed tomography angiography and transthoracic Doppler echocardiography

Accelerated flow at the site of flow-limiting stenosis can be detected by transthoracic Doppler echocardiography (TTDE). We studied feasibility and accuracy of sequential coronary computed tomography angiography (CTA) and TTDE in detection of haemodynamically significant coronary artery disease (CAD). We prospectively enrolled 107 patients with intermediate (30-70%) pre-test likelihood of CAD. All patients underwent CTA using a 64-slice scanner. Using TTDE, the ratio of maximal diastolic flow velocity to pre-stenotic flow velocity (M/P ratio) was measured in the coronary segments with stenosis in CTA. In all patients, the results were compared with invasive coronary angiography, including measurement of fractional flow reserve when appropriate. All analyses were done blinded. TTDE was feasible in 276 of 285 evaluated coronary segments. Significant coronary stenoses were associated with a higher M/P ratio than non-significant stenoses (3.59 ± 1.82 vs. 1.28 ± 0.60, P < 0.001). The optimal M/P ratio for detection of significant stenosis was 2.2 (area under receiver operating characteristic curve 0.92, P < 0.001). Compared with the strategy of CTA alone, sequential CTA and focused TTDE had a better positive predictive value (PPV; 61 vs. 78%) and diagnostic accuracy (93 vs. 96%, P = 0.006) without impairment of the negative predictive value (97 vs. 97%). Sequential use of CTA and TTDE is feasible for combined anatomic and functional evaluation of coronary stenoses. Compared with coronary CTA alone, addition of TTDE improved PPV for detection of significant CAD.

Magnetic compression anastomosis is useful in biliary anastomotic strictures after living donor liver transplantation

An anastomotic biliary stricture is a complication of living donor liver transplantation (LDLT) performed using duct-to-duct anastomosis. Despite advances in treating this complication, there is no one established treatment protocol. To investigate the safety, effectiveness, and mid-term outcome of magnetic compression anastomosis (MCA) for treating biliary obstruction after LDLT when the obstruction cannot be resolved by using percutaneous or peroral methods. Retrospective, observational study with standardized treatment and follow-up. Tertiary-care academic medical center. Twelve patients underwent MCA procedures to treat anastomosis site stricture after LDLT. MCA. Bile duct patency, technique performance, and complications were evaluated. We achieved magnet approximation at the anastomotic stricture in 10 of 12 patients (83.3%). The magnets failed to approximate in 2 patients. We achieved recanalization of the stricture site in 10 of 10 patients. We removed an internal catheter in 9 patients. The mean interval from magnet approximation to removal was 74.2 days (range 14-181 days). The mean time from recanalization to removal of the internal catheter was 183 days (range 51-266 days). Patients were examined regularly after removing the internal catheter with a mean follow-up period of 331 days (range 148-581 days). The observed MCA-related complications consisted of 1 case of mild cholangitis and 1 recurrence of the anastomotic stricture. Nonrandomized study design. MCA safely and effectively resolved post-LDLT biliary duct-to-duct anastomotic strictures that could not be resolved using conventional methods, such as ERCP and percutaneous transhepatic biliary drainage.

Stenting for Symptomatic Extracranial Vertebral Artery Stenosis

The proximal extracranial vertebral artery is a common site of stenosis identified by cerebral angiography (second only to carotid bifurcation). In an

Disturbed flow in radial-cephalic arteriovenous fistulae for haemodialysis: low and oscillating shear stress locates the sites of stenosis

Despite recent clinical and technological advancements, the vascular access (VA) for haemodialysis still has significant early failure rates after arteriovenous fistula (AVF) creation. VA failure is mainly related to the haemodynamic conditions that trigger the phenomena of vascular wall disease such as intimal hyperplasia (IH) or atherosclerosis. We performed transient computational fluid dynamics simulations within idealized three-dimensional models of 'end-to-side' and 'end-to-end' radio-cephalic anastomosis, using non-Newtonian blood and previously measured flows and division ratio in subjects requiring primary access procedure as boundary conditions. The numerical simulations allowed full characterization of blood flow inside the AVF and of patterns of haemodynamic shear stress, known to be the major determinant of vascular remodelling and disease. Wall shear stress was low and oscillating in zones where flow stagnation occurs on the artery floor and on the inner wall of the juxta-anastomotic vein. Zones of low and oscillatory shear stress were located in the same sites where luminal reduction was documented in previous experimental studies on sites stenosis distribution in AVF. We conclude that even when exposed to high flow rates, there are spot regions along the AVF exposed to athero-prone shear stress that favour vessel stenosis by triggering IH.