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Background Chronic mesenteric ischemia (CMI) results from the inability to achieve adequate postprandial intestinal blood flow, usually from atherosclerotic occlusive disease at the origins of the mesenteric vessels. Patients typically present with postprandial pain, food fear, and weight loss, although they can present with acute mesenteric ischemia and bowel infarction. The diagnosis requires a combination of the appropriate clinical symptoms and significant mesenteric artery occlusive disease, although it is often delayed given the spectrum of gastrointestinal disorders associated with abdominal pain and weight loss. The treatment goals include relieving the presenting symptoms, preventing progression to acute mesenteric ischemia, and improving overall quality of life. These practice guidelines were developed to provide the best possible evidence for the diagnosis and treatment of patients with CMI from atherosclerosis. Methods The Society for Vascular Surgery established a committee composed of vascular surgeons and individuals experienced with evidence-based reviews. The committee focused on six specific areas, including the diagnostic evaluation, indications for treatment, choice of treatment, perioperative evaluation, endovascular/open revascularization, and surveillance/remediation. A formal systematic review was performed by the evidence team to identify the optimal technique for revascularization. Specific practice recommendations were developed using the Grading of Recommendations Assessment, Development, and Evaluation system based on review of literature, the strength of the data, and consensus. Results Patients with symptoms consistent with CMI should undergo an expedited workup, including a computed tomography arteriogram, to exclude other potential causes. The diagnosis is supported by significant arterial occlusive disease in the mesenteric vessels, particularly the superior mesenteric artery. Treatment requires revascularization with the primary target being the superior mesenteric artery. Endovascular revascularization with a balloon-expandable covered intraluminal stent is the recommended initial treatment with open repair reserved for select younger patients and those who are not endovascular candidates. Long-term follow-up and surveillance are recommended after revascularization and for asymptomatic patients with severe mesenteric occlusive disease. Patient with recurrent symptoms after revascularization owing to recurrent stenoses should be treated with an endovascular-first approach, similar to the de novo lesion. Conclusions These practice guidelines were developed based on the best available evidence. They should help to optimize the care of patients with CMI. Multiple areas for future research were identified.

Thoracic outlet syndrome (TOS) is the clinical entity that occurs with compression of the brachial plexus, subclavian artery, and/or subclavian vein at the superior thoracic outlet. Compression of each of these structures results in characteristic symptoms divided into three variants: neurogenic TOS, venous TOS, and arterial TOS, each arising from the specific structure that is compressed. The constellation of symptoms in each patient may vary, and patients may have more than one symptom simultaneously. Understanding the various anatomic spaces, causes of narrowing, and resulting neurovascular changes is important in choosing and interpreting radiological imaging performed to help diagnose TOS and plan for intervention. This publication has separated imaging appropriateness based on neurogenic, venous, or arterial symptoms, acknowledging that some patients may present with combined symptoms that may require more than one study to fully resolve. Additionally, in the postoperative setting, new symptoms may arise altering the need for specific imaging as compared to preoperative evaluation. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Abdominal pain with elevated transaminases from inferior vena cava (IVC) obstruction is a relatively common reason for referral and further workup by a hepatologist. The differential for the cause of IVC obstruction is extensive, and the most common etiologies include clotting disorders or recent trauma. In some situations the common etiologies have been ruled out, and the underlying process for the patient’s symptoms is still not explained. We present one unique case of abdominal pain and hepatomegaly secondary to IVC constriction from extrinsic compression of the diaphragm. Based on this patient’s presentation, we urge that physicians be cognizant of the IVC diameter and consider extrinsic compression as a contributor to the patient’s symptoms. If IVC compression from the diaphragm is confirmed, early referral to vascular surgery is strongly advised for further surgical intervention.

Abdominal aortic aneurysms (AAAs) are a relatively common vascular problem that can be treated with either open, surgical repair or endovascular aortic aneurysm repair (EVAR). Both approaches to AAA repair require dedicated preoperative imaging to minimize adverse outcomes. After EVAR, cross-sectional imaging has an integral role in confirming the successful treatment of the AAA and early detection of complications related to EVAR. CT angiography is the primary imaging modality for both preoperative planning and follow-up after repair. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Peripheral arterial disease (PAD) affects millions across the world and in the United States between 9% to 23% of all patients older than 55 years. The refinement of surgical techniques and evolution of endovascular approaches have improved the success rates of revascularization in patients afflicted by lower extremity PAD. However, restenosis or occlusion of previously treated vessels remains a pervasive issue in the postoperative setting. A variety of different imaging options are available to evaluate patients and are reviewed within the context of asymptomatic and symptomatic patients with PAD who have previously undergone endovascular or surgical revascularization. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

In patients with penetrating neck injuries with clinical soft injury signs, and patients with hard signs of injury who do not require immediate surgery, CT angiography of the neck is the preferred imaging procedure to evaluate extent of injury. Other modalities, such as radiography and fluoroscopy, catheter-based angiography, ultrasound, and MR angiography have their place in the evaluation of the patient, depending on the specific clinical situation and question at hand. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer-reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Upper gastrointestinal bleeding (UGIB) remains a significant cause of morbidity and mortality with mortality rates as high as 14%. This document addresses the indications for imaging UGIB that is nonvariceal and unrelated to portal hypertension. The four variants are derived with respect to upper endoscopy. For the first three, it is presumed that upper endoscopy has been performed, with three potential initial outcomes: endoscopy reveals arterial bleeding source, endoscopy confirms UGIB without a clear source, and negative endoscopy. The fourth variant, "postsurgical and traumatic causes of UGIB; endoscopy contraindicated" is considered separately because upper endoscopy is not performed. When endoscopy identifies the presence and location of bleeding but bleeding cannot be controlled endoscopically, catheter-based arteriography with treatment is an appropriate next study. CT angiography (CTA) is comparable with angiography as a diagnostic next step. If endoscopy demonstrates a bleed but the endoscopist cannot identify the bleeding source, angiography or CTA can be typically performed and both are considered appropriate. In the event of an obscure UGIB, angiography and CTA have been shown to be equivalent in identifying the bleeding source; CT enterography may be an alternative to CTA to find an intermittent bleeding source. In the postoperative or traumatic setting when endoscopy is contraindicated, primary angiography, CTA, and CT with intravenous contrast are considered appropriate. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Vascular claudication is a symptom complex characterized by reproducible pain and weakness in an active muscle group due to peripheral arterial disease. Noninvasive hemodynamic tests such as the ankle brachial index, toe brachial index, segmental pressures, and pulse volume recordings are considered the first imaging modalities necessary to reliably establish the presence and severity of arterial obstructions. Vascular imaging is consequently used for diagnosing individual lesions and triaging patients for medical, percutaneous, or surgical intervention. Catheter angiography remains the reference standard for imaging the peripheral arteries, providing a dynamic and accurate depiction of the peripheral arteries. It is particularly useful when endovascular intervention is anticipated. When combined with noninvasive hemodynamic tests, however, noninvasive imaging, including ultrasound, CT angiography, and MR angiography, can also reliably confirm or exclude the presence of peripheral arterial disease. All modalities, however, have their own technical limitations when classifying the location, extent, and severity of disease. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer-reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Objective Unexplained aneurysm growth despite multimodality imaging after endovascular aneurysm repair is often attributed to endotension. We tested a hypothesis that endotension may be from a type Ia endoleak pressurizing the aneurysm sac, without net forward flow, not visualized on standard angiographic imaging. Methods A patient-specific aortic aneurysm phantom was constructed of polyvinyl alcohol using three-dimensional molding techniques. A bifurcated stent graft was implanted, and the phantom was connected to a hemodynamic simulator for testing. Type Ia endoleaks were created using 7F catheters. Three scenarios were studied: complete exclusion (no endoleak), inflow with no sac outflow, and inflow with sac outflow. Imaging with digital subtraction angiography was performed at 48 kVp at 5 frames/s, followed by delayed imaging at 1 frame/min for 30 minutes. Results With no endoleak, the systemic pressure averaged 113 mm Hg and aneurysm sac pressure averaged 101 mm Hg. With an endoleak present without outflow, the systemic pressure averaged 116 mm Hg, the aneurysm sac pressure averaged 120 mm Hg, and endoleak flow was bidirectional with no net forward flow. With endoleak present with aneurysm sac outflow, the systemic pressure averaged 119 mm Hg, aneurysm sac pressure averaged 105.5 mm Hg, and net endoleak flow into the aneurysm sac was 21 mL/min across the endoleak channel. With digital subtraction imaging, the endoleak with no outflow was noted after >9 minutes of delayed imaging. Conclusions In our model, the creation of a type Ia endoleak in the absence of sac outflow resulted in a mean pressure higher than the systemic mean pressure with zero net flow into the aneurysm sac. Consequently, the endoleak could only be visualized with markedly delayed imaging and not with standard contrast digital subtraction angiography like that used in clinical practice. Our findings suggest that endotension may in fact be the result of undetected endoleaks secondary to the limitations of present iodinated contrast imaging modalities.

Mesenteric ischemia is an uncommon condition resulting from decreased blood flow to the small or large bowel in an acute or chronic setting. Acute ischemia is associated with high rates of morbidity and mortality; however, it is difficult to diagnose clinically. Therefore, a high degree of suspicion and prompt imaging evaluation are necessary. Chronic mesenteric ischemia is less common and typically caused by atherosclerotic occlusion or severe stenosis of at least two of the main mesenteric vessels. While several imaging examination options are available for the initial evaluation of both acute and chronic mesenteric ischemia, CTA of the abdomen and pelvis is overall the most appropriate choice for both conditions. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Abdominal aortic aneurysms (AAAs) are a relatively common vascular problem that can be treated with either open, surgical repair or endovascular aortic aneurysm repair (EVAR). Both approaches to AAA repair require dedicated preoperative imaging to minimize adverse outcomes. After EVAR, cross-sectional imaging has an integral role in confirming the successful treatment of the AAA and early detection of complications related to EVAR. CT angiography is the primary imaging modality for both preoperative planning and follow-up after repair. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Peripheral arterial disease (PAD) affects millions across the world and in the United States between 9% to 23% of all patients older than 55 years. The refinement of surgical techniques and evolution of endovascular approaches have improved the success rates of revascularization in patients afflicted by lower extremity PAD. However, restenosis or occlusion of previously treated vessels remains a pervasive issue in the postoperative setting. A variety of different imaging options are available to evaluate patients and are reviewed within the context of asymptomatic and symptomatic patients with PAD who have previously undergone endovascular or surgical revascularization. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

In patients with penetrating neck injuries with clinical soft injury signs, and patients with hard signs of injury who do not require immediate surgery, CT angiography of the neck is the preferred imaging procedure to evaluate extent of injury. Other modalities, such as radiography and fluoroscopy, catheter-based angiography, ultrasound, and MR angiography have their place in the evaluation of the patient, depending on the specific clinical situation and question at hand. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer-reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Upper gastrointestinal bleeding (UGIB) remains a significant cause of morbidity and mortality with mortality rates as high as 14%. This document addresses the indications for imaging UGIB that is nonvariceal and unrelated to portal hypertension. The four variants are derived with respect to upper endoscopy. For the first three, it is presumed that upper endoscopy has been performed, with three potential initial outcomes: endoscopy reveals arterial bleeding source, endoscopy confirms UGIB without a clear source, and negative endoscopy. The fourth variant, "postsurgical and traumatic causes of UGIB; endoscopy contraindicated" is considered separately because upper endoscopy is not performed. When endoscopy identifies the presence and location of bleeding but bleeding cannot be controlled endoscopically, catheter-based arteriography with treatment is an appropriate next study. CT angiography (CTA) is comparable with angiography as a diagnostic next step. If endoscopy demonstrates a bleed but the endoscopist cannot identify the bleeding source, angiography or CTA can be typically performed and both are considered appropriate. In the event of an obscure UGIB, angiography and CTA have been shown to be equivalent in identifying the bleeding source; CT enterography may be an alternative to CTA to find an intermittent bleeding source. In the postoperative or traumatic setting when endoscopy is contraindicated, primary angiography, CTA, and CT with intravenous contrast are considered appropriate. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Background Validation of carotid duplex ultrasound velocity criteria (CDUS VC) to grade the severity of extracranial carotid artery stenosis has traditionally been based on conventional angiography measurements. In the last decade, computed tomographic angiography (CTA) has largely replaced conventional arch and carotid arteriography (CA) for diagnostic purposes. Given the low number of CA being performed, it is impractical to expect noninvasive vascular laboratories to be validated using this modality. CDUS VC have not been developed with the use of CTA-derived measurements. The objective was to determine optimal CDUS VC from CTA-derived measurements with the North American Symptomatic Carotid Endarterectomy Trial (NASCET) method for 50% and 80% stenosis. Methods A retrospective review of all patients who underwent CDUS and CTA from 2000 to 2009 was performed. Vessel diameters were measured on CTA, and corresponding CDUS velocities were recorded. Percent stenosis was calculated using the NASCET method. Receiver operating characteristic (ROC) curves were generated for internal carotid artery (ICA) peak systolic velocity (PSV), ICA end diastolic velocity (EDV), and ICA PSV to common carotid artery PSV ratio (PSVR) for 50% and 80% stenosis. Velocity cut points were determined with equal weighting of sensitivity and specificity. Results A total of 575 vessels were analyzed to create the ROC curves. A 50% stenosis analysis yielded ideal cut points for PSV, EDV, and PSVR of 130 cm/sec, 42 cm/sec, and 1.75. An 80% stenosis analysis yielded ideal cut points for PSV, EDV, and PSVR of 297 cm/sec, 84 cm/sec, and 3.06. Conclusions CTA-derived CDUS VC appeared to be reliable in defining 50% and 80% stenosis in patients with carotid artery stenosis. Although CDUS VC defined in this study were different from many of the previously published VC for the same percent stenosis, there were many similarities to those reported by the Society of Radiologists in Ultrasound consensus conference. We feel that CTA should be the gold standard imaging technique for validating CDUS VC.

Despite a decline during the recent decades in stroke-related death, the incidence of stroke has remained unchanged or slightly increased, and extracranial carotid artery stenosis is implicated in 20%–30% of all strokes. Medical therapy and risk factor modification are first-line therapies for all patients with carotid occlusive disease. Evidence for the treatment of patients with symptomatic carotid stenosis greater than 70% with either carotid artery stenting (CAS) or carotid endarterectomy (CEA) is compelling, and several trials have demonstrated a benefit to carotid revascularization in the symptomatic patient population. Asymptomatic carotid stenosis is more controversial, with the largest trials only demonstrating a 1% per year risk stroke reduction with CEA. Although there are sufficient data to advocate for aggressive medical therapy as the primary mode of treatment for asymptomatic carotid stenosis, there are also data to suggest that certain patient populations will benefit from a stroke risk reduction with carotid revascularization. In the United States, consensus and practice guidelines dictate that CEA is reasonable in patients with high-grade asymptomatic stenosis, a reasonable life expectancy, and perioperative risk of less than 3%. Regarding CAS versus CEA, the best-available evidence demonstrates no difference between the two procedures in early perioperative stroke, myocardial infarction, or death, and no difference in 4-year ipsilateral stroke risk. However, because of the higher perioperative risks of stroke in patients undergoing CAS, particularly in symptomatic, female, or elderly patients, it is difficult to recommend CAS over CEA except in populations with prohibitive cardiac risk, previous carotid surgery, or prior neck radiation. Current treatment paradigms are based on identifying the magnitude of perioperative risk in patient subsets and on using predictive factors to stratify patients with high-risk asymptomatic stenosis.

BackgroundExperimental modeling of arteriovenous hemodialysis fistula (AVF) hemodynamics is challenging. Mathematical modeling struggles to accurately represent the capillary bed and venous circulation. In vivo animal models are expensive and labor intensive. We hypothesized that an in vitro, physiologic model of the extremity arteriovenous circulation with provisions for AVF and distal revascularization and interval ligation (DRIL) configurations could be created as a platform for hemodynamic modeling and testing.MethodsAn anatomic, upper extremity arteriovenous model was constructed of tubing focusing on the circulation from the subclavian artery to subclavian vein. Tubing material, length, diameter, and wall thickness were selected to match vessel compliance and morphology. All branch points were constructed at physiologic angles. The venous system and capillary bed were modeled using tubing and one-way valves and compliance chambers. A glycerin/water solution was created to match blood viscosity. The system was connected to a heart simulator. Pressure waveforms and flows were recorded at multiple sites along the model for the native circulation, brachiocephalic AVF configuration, and the AVF with DR without and with IL (DR no IL and DRIL).ResultsA preset mean cardiac output of 4.2 L/min from the heart simulator yielded a subclavian artery pressure of 125/55 mm Hg and a brachial artery pressure of 121/54 mm Hg with physiologic arterial waveforms. Mean capillary bed perfusion pressure was 41 mm Hg, and mean venous pressure in the distal brachial vein was 17 mm Hg with physiologic waveforms. AVF configuration resulted in a 15% decrease in distal pressure and a 65% decrease in distal flow to the hand. DR no IL had no change in distal pressure with a 27% increase in distal flow. DRIL resulted in a 3% increase in distal pressure and a 15% increase in distal flow to the hand above that of DR no IL. Flow through the DR bypass decreased from 329 mL/min to 55 mL/min with the addition of IL. Flow through the AVF for both DR no IL and DRIL was preserved.ConclusionsThrough the construction and validation of an in vitro, pulsatile arteriovenous model, the intricate hemodynamics of AVF and treatments for ischemic steal can be studied. DR with or without IL improved distal blood flow in addition to preserving AVF flow. IL decreased the blood flow through the DR bypass itself. The findings of the AVF as a pressure sink and the relative role of IL with DR bypass has allowed this model to provide hemodynamic insight difficult or impossible to obtain in animal or human models. Further study of these phenomena with this model should allow for more effective AVF placement and maturation while personalizing treatment for associated ischemic steal.Clinical RelevanceThe complications of arteriovenous fistula (AVF)-associated steal with its concurrent surgical treatments have been clinically described but have relatively little published, concrete hemodynamic data. A further understanding of the underlying hemodynamics is necessary to prevent the occurrence of steal and improve treatment when it occurs. Specific objectives are to study the blood flow through an AVF with varying anatomic and physiologic parameters, determine what factors contribute to the development of arterial steal distal to an AVF, and create optimal interventions to treat arterial steal from an AVF when it occurs. The long-term goal is creation of AVF tailored to patient-specific parameters, resulting in higher rates of functional fistulas with decreases in fistula-related complications. The ability to study fluid dynamics using a unique, in vitro, upper extremity pulsatile arteriovenous circulation simulator creates the ideal platform for this work.

ObjectiveThe single puncture intravascular ultrasound (IVUS)-guided bedside placement of inferior vena cava (IVC) filters has been shown to be an effective technique. The major disadvantage of this procedure is a steep learning curve that can lead to an increased risk of filter malposition. In an effort to increase the safety and efficacy of IVUS-guided bedside IVC filter placement, we proposed that preoperative planning could reduce the incidence of IVUS-guided filter malpositions. As a first step, we examined the correlation between preoperative abdominal computed tomography (CT) scan measurements and intraprocedural IVUS derived measurements of vena cava anatomy and its surrounding structures. As a second step, we attempted to determine the safety of this protocol by assessing the incidence of malposition.MethodsA retrospective review of prospectively collected data was performed on all patients receiving bedside IVUS-guided filters from July 1, 2010 to August 31, 2011. Measurements of the IVC length from the atrial-IVC junction to the midportion of the crossing right renal artery, the lowest renal vein, and iliac vein confluence were obtained prior to IVC filter placement by both CT-based measurement, as well as intraprocedural IVUS pullback lengths. Regression analysis (significant for P < .05) was used to determine the correlation between these imaging modalities.ResultsForty-six patients had adequate CT scans available to perform the analysis and were candidates for bedside IVUS-guided IVC filter placement. All IVUS-guided filters were placed using a single puncture technique with the Cook Celect Filter. This study found there was a close correlation between IVUS and CT derived measurements of the right atrium to right renal artery distance, lowest renal vein distance, and iliac confluence distance. In addition, we found that the IVUS distances from the atrial-IVC junction to the right renal artery and lowest renal vein were statistically similar. Nine patients had 10 vascular anatomic variations, all identified by both IVUS and CT. There were no complications or malpositions of IVC filters using this protocol.ConclusionsThese data suggest that IVUS pullback measurements from the right atrium used in combination with preprocedure CT derived measurements of the distance from the right atrium to the lowest renal vein and iliac vein confluence provide an accurate roadmap for the placement of bedside IVC filters under IVUS guidance. We provide a method for organizing this information in a preplanning document to aid this procedure. We suggest this easily employed technique be more fully utilized to help decrease the incidence of malpositioned filters using single puncture IVUS guidance.

Pulmonary arteriovenous malformations are often included in the differential diagnosis of common clinical presentations, including hypoxemia, hemoptysis, brain abscesses, and paradoxical stroke, as well as affecting 30% to 50% of patients with hereditary hemorrhagic telangiectasia (HHT). Various imaging studies are used in the diagnostic and screening settings, which have been reviewed by the ACR Appropriateness Criteria Vascular Imaging Panel. Pulmonary arteriovenous malformation screening in patients with HHT is commonly performed with transthoracic echocardiographic bubble study, followed by CT for positive cases. Although transthoracic echocardiographic bubble studies and radionuclide perfusion detect right-to-left shunts, they do not provide all of the information needed for treatment planning and may remain positive after embolization. Pulmonary angiography is appropriate for preintervention planning but not as an initial test. MR angiography has a potential role in younger patients with HHT who may require lifelong surveillance, despite lower spatial resolution compared with CT. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every three years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

An abdominal aortic aneurysm (AAA) carries one of the highest mortality rates among vascular diseases when it ruptures. To predict the role of surface curvature in rupture risk assessment, a discriminatory analysis of aneurysm geometry characterization was conducted. Data was obtained from 205 patient-specific computed tomography image sets corresponding to three AAA population subgroups: patients under surveillance, those that underwent elective repair of the aneurysm, and those with an emergent repair. Each AAA was reconstructed and their surface curvatures estimated using the biquintic Hermite finite element method (BQFE). Local surface curvatures were processed into ten global curvature indices. Statistical analysis of the data revealed that the L2-norm of the Gaussian and Mean surface curvatures can be utilized as classifiers of the three AAA population subgroups. The application of statistical machine learning on the curvature features yielded 85.5% accuracy in classifying electively and emergent repaired AAAs, compared to a 68.9% accuracy obtained by using maximum aneurysm diameter alone. Such combination of non-invasive geometric quantification and statistical machine learning methods can be used in a clinical setting to assess the risk of rupture of aneurysms during regular patient follow-ups.

Dialysis access failure and associated complications represent a major cause of morbidity in patients with renal failure. This is due to an incomplete understanding of the hemodynamics associated with both arteriovenous fistula (AVF) successes and complications. Several decades of research have been performed studying these complex hemodynamic changes. This review provides an overview of work undertaken in three key areas of AVF hemodynamic research: mathematical modeling, in vivo fluid dynamic measurements and in vitro fluid dynamic modeling. Current and future work is then summarized involving the application of a comprehensive, systematic study of dialysis access hemodynamics. The ultimate goal is the ability to predict clinical outcomes of dialysis access procedures through personalized, patient-specific surgical planning. If successful, this type of tool would allow surgeons to predict multiple-dialysis access intervention outcomes and choose a personalized approach to maximize success.

Duplex surveillance of arterial stents has focused on detecting in-stent restenosis. Although velocity is commonly reported, that differs from blood flow, and patency of arterial prostheses is flow-dependent. Preliminary evaluation was performed to determine if postprocedure peak systolic blood flow (PSF) through stents correlates with rate of repeat intervention at 12 months.Retrospective review of consecutive patients undergoing arterial stent placement was performed. Demographics, comorbidities, stent size, postprocedure duplex information, and repeat intervention rates were recorded. PSF was calculated by using peak systolic velocity (PSV) and stent dimensions.Consecutive stents (N = 35) were placed in 27 patients (mean age, 72.6 y ± 14). Twenty stents were free from repeat intervention (FR) and 15 required repeat intervention (RR) at 12 months. There was a significant difference between FR and RR groups with respect to initial in-stent PSV and PSF (92.5 cm/s for FR vs 43.7 cm/s for RR [P.002]; 1,918 mL/min for FR vs 722 mL/min for RR [P.0001]). PSF showed sensitivity, specificity, and accuracy rates of 92%, 82%, and 86.2%, respectively, for predicting repeat intervention, versus 83%, 71%, and 76% for PSV. Receiver operating characteristic curve analysis showed a greater area under the curve for PSF versus PSV (0.965 vs 0.859).PSF from an initial postprocedure duplex study accurately correlates with need for repeat stent intervention at 12 months. PSV had a lower sensitivity, specificity, and accuracy. This preliminary finding must be confirmed by prospective studies in individual vascular beds and larger patient populations. A new approach to stent surveillance is suggested.

Objectives Endovenous closure is a common method to treat saphenous vein incompetence. Despite attempts to prevent it, some patients have extension of thrombus above the ideal site of closure immediately below the epigastric vein. We have developed a classification system for the level of saphenous vein closure to guide further therapy after endovenous treatment. Methods A six-tier classification system was developed, based on thrombus proximity to the epigastric or femoral vein, and an algorithm for treatment, based on level of closure was applied to all patients. Results Five hundred consecutive patients underwent radio-frequency ablation of the saphenous vein; it was successfully closed in 498 (99.6%) patients. Thirteen patients (2.6%) experienced thrombus bulging into the femoral vein or adherent to its wall, which was treated with anticoagulation. All of these patients had thrombus retraction to the level of the saphenofemoral junction (SFJ) in an average of 16 days with concurrent anticoagulation. No femoral deep venous thrombosis (DVT) occurred in the series. There was a significantly higher rate of proximal thrombus extension in those patients with a history of DVT and those with a great saphenous vein (GSV) diameter of >8 mm (P Conclusions A classification system for saphenous endovenous closure which extends above the epigastric vein has been helpful in guiding management. A GSV diameter at the SFJ of >8 mm and a history of DVT results in significantly higher rates of proximal thrombus extension into the femoral vein. A short course of LMWH, until clot retracts back into the saphenous vein, is therapeutic. Management of the patients with thrombus flush with the femoral vein wall still needs to be defined, but the outcome from these patients is generally benign.

Rationnelle Les anevrysmes de l’artere renale (AAR) representent une pathologie vasculaire rare avec une incidence estimee Methodes Une revue de tous les patients porteurs d’un AAR a ete realisee, identifies par les codes ICD-9 , de janvier 2003 a decembre 2008 vus dans un centre medical de soins tertiaires. Des donnees ont ete rassemblees concernant la demographie des patients, les caracteristiques de l’anevrysme, la reparation chirurgicale, et les resultats, ainsi que le suivi. Resultats Un total de 14 patients (10 femmes et 4 hommes ; âge moyen, 48 ± 19 ans) etaient inclus, representant 15 anevrysmes. Dix anevrysmes ont subi la reparation ouverte par l’intermediaire d’ARA et cinq ont ete suivis sans etre operes. La taille moyenne de AAR etait plus grande pour ceux subissant la reparation (2,12cm contre 1.62cm, p = 0,037). Sept AAR ont ete repares in situ avec angioplastie par patch ou par reparation primaire ; une reconstruction ex de vivo a ete necessaire pour trois cas; et aucun n’a necessite de pontage. La duree operatoire moyenne etait semblable pour les differents types de reparation, avec une perte de sang plus elevee lors des reparations ex de vivo. La duree mediane de sejour etait de 5 jours (extremes 4 a 14 jours). La reparation n’a eu aucun effet sur la tension arterielle systolique moyenne ou le DFG. Cette reparation, cependant, a eu comme consequence une reduction du nombre de drogues anti hypertensives pour ceux ayant une hypertension associee (2,7 avant contre 1.6 apres, p = 0.03). Il y avait une tendance pour une duree plus courte avant reprise de l’alimentation pour l’approche retroperitoneale par rapport a l’abord transperitoneal. La duree moyenne de suivi etait de 11,6 mois (extremes 3 a 30 mois). Aucune rupture, mort, nephrectomie, ou insuffisance renale n’est survenue dans le groupe. Conclusion A l’epoque des reparations endovasculaires des AAR, la chirurgie ouverte, specifiquement par ARA des AAR demeure un traitement sur avec une faible morbidite associee. La reparation des AAR a eu comme consequence une reduction des medicaments pour ceux presentant une hypertension arterielle associee. La reparation ouverte des AAR devrait etre la technique de premiere intention pour les AAR complexes, surtout en cas d’hypertension arterielle associee.

Rationnelle En 2008, le chirurgien general a fait une demande d’action pour la prevention de la thrombose veineuse profonde (TVP), et pour la premiere fois, les recommandations de l’ American College of Chest Physicians de 2008 pour le traitement des TVP aigues des membres inferieurs (TVPAMI) ont ete mises a jour pour inclure la thrombolyse comme recommandation de niveau 2B. La thrombolyse dirigee par catheter (CDT) pour des patients avec TVPAMI sans contre-indication peut permettre une dissolution plus complete du caillot que l’anticoagulation seule et peut empecher les consequences a long terme des TVP. Nous avons cherche a determiner le pourcentage des hospitalises avec une TVPAMI dans un centre medical tertiaire qui etaient candidats au traitement par CDT et si ces patients ont ete convenablement diriges vers un tel traitement. Methodes Une recherche dans la base de donnees administrative d’un centre medical tertiaire entre janvier 2007 et decembre 2007 a indique 667 admissions de patients liees a un diagnostic de TVP selon la classification internationale des maladies, neuvieme revision des codes de diagnostic (451-451,99, 453-453,99). Les dossiers informatises de l’hopital ont ete alors explores pour rechercher les informations concernant les antecedents medicaux, les comorbidites, des contre-indications a la thrombolyse, les symptomes, les resultats des examens d’imagerie et le traitement. Resultats Sur 667 admissions de patients, 157 (24%) avaient une TVPAMI, 31% avaient une TVP du membre superieur, 17% presentaient un antecedent de TVP, et 28% avaient une thrombose veineuse dans d’autres veines. De ces 157 patients avec TVPAMI, 60 (38%) avaient une TVP iliofemorale proximale ou femorale etendue qui les rendaient candidats pour une thrombolyse. Des 60 patients, seulement 10 (17%) n’avaient pas de contre-indication majeure a la thrombolyse. Parmi ces derniers, un a refuse le traitement par CDT propose, quatre n’ont pas eu d’avis pour la thrombolyse et cinq (9%) ont accepte la CDT et ont ete traites. Au total, sur ces 60 patients, 50 (83%) avaient une pathologie severe et des contre-indications majeures et souvent multiples a la thrombolyse. Conclusion Bien que la majorite des patients identifies dans la base de donnees d’hospitalisation de 2007 avec TVPAMI et absence des contre-indications a la thrombolyse aient ete convenablement informe de la possibilite de traitement par CDT, les patients d’un centre de soins tertiaire ont typiquement des comorbidites medicales graves excluant l’utilisation de la thrombolyse. Les futures etudes evaluant le role en expansion de la CDT chez les patients avec TVPAMI devraient se concentrer sur un recrutement de patients externes ou de centres hospitaliers de plus petite taille, comprenant des patients susceptibles d’avoir moins de contre-indications a la thrombolyse.

The etiology of spontaneous dissection of the carotid and vertebral arteries without antecedent trauma remains unclear. The goal of this 10-year review was to examine factors regarding presentation, diagnosis, treatment, and outcome for all patients at our institution who were diagnosed with spontaneous carotid dissections (SCD) or spontaneous vertebral dissections (SVD) with no prior trauma history. A retrospective chart analysis was performed involving all discharges from UCSD Medical Center from 1995 to 2005. Patients were selected for inclusion based on the diagnosis of carotid or vertebral dissection with no associated traumatic or iatrogenic cause for their presentation. Characteristics of these patients' medical risk factors, presenting symptoms, diagnostic method and time, treatment, and outcomes were analyzed. A total of 20 patients (10 male, age 44.8 +/- 12.9 yrs; 10 female, age 39.6 +/- 14.9 yrs) were included for study. These patients represented 12 cases of SCD and nine SVD. On presentation, a majority of patients with both SVD and SCD reported headache as their primary complaint while a significantly higher rate of nausea (25% vs. 67%, p < 0.01) was reported in SVD. SVD was associated with a significantly longer diagnostic time (11 hr vs. 16 hr, p < 0.01). The most commonly performed diagnostic exam in both SCD and SVD was magnetic resonance angiography (MRA). Anticoagulation was the primary treatment in 11 of 12 SCD and all nine SVD. One patient with persistent, symptomatic bilateral carotid dissection after anticoagulation was treated with stent placement resulting in unilateral intracranial hemorrhage (ICH). Length of stay was significantly longer in SVD (5 d vs. 7 d, p < 0.02). A significantly higher incidence of persistent neurologic deficits on discharge was seen in SCD (71% vs. 33%, p < 0.02). Radiographic evidence of cerebral infarction on discharge had a stronger correlation with clinical deficits in SCD. Although there were only two cases, those treated with endovascular therapy in the setting of SCD suffered complications related to the intervention. On discharge, there did not seem to be a correlation between persistent neurologic deficits and radiographic evidence of infarction in SVD reflecting that recovery after these episodes may not be predictable based on the appearance of the infarction.

Surgical bypass represents one of the chief treatment modalities for peripheral arterial occlusive disease. Despite improving techniques, graft occlusion accounts for the majority of these bypass failures. Once occluded, however, these grafts are thought to rarely pose a threat for future ischemic events. This report describes two patients with previously thrombosed grafts who subsequently presented with limb-threatening ischemia owing to peripheral embolization from the graft. Two patients with occluded grafts presented with ipsilateral limb-threatening acute ischemia. Both of these patients developed severe acute limb-threatening ischemia weeks to months after known graft thrombosis. Arteriography revealed peripheral embolization in each case. Both patients were operated on for disconnection of the thrombosed graft from the native circulation and have been free of recurrent symptoms. The occluded graft, although generally innocuous, can be a source of peripheral emboli, resulting in peripheral embolization and acute limb ischemia. Both patients in this report developed limb-threatening ischemia owing to embolization from the cul-de-sac of occluded prosthetic grafts. Due to the rarity of the condition and its associated morbidity and mortality, awareness and recognition of this phenomenon are critical. Operative disconnection is recommended if the embolism occurs downstream of the graft and no other embolic source can be identified.

The optimal dialysis access for the patient with chronic renal failure is considered to be an autogenous fistula; this is reflected in the recommendations of the National Kidney Foundation–Disease Outcomes Quality Initiatives (NKF-DOQI). If adequate superficial veins at the wrist or the forearm are not available, the next option is usually a prosthetic arteriovenous graft. In this case series, we describe our experience with an autogenous fistula constructed using the brachial vein. There were 20 patients over a 14-month period who were operated on for dialysis access. In these patients, no adequate superficial veins were found at operation. Instead of using a prosthetic graft, we performed a brachial artery–brachial vein fistula in two stages. The first stage involved a forearm anastomosis and then subsequently, weeks later, this fistula was “superficialized.” Twenty patients underwent a brachial artery–brachial vein fistula. Of these patients, all had successful maturation of their fistula and after a minimum waiting period of 12 weeks for maturation; all but one were able to be successfully dialyzed through their fistula. One patient developed arm swelling due to previously placed subclavian vein pacemaker wires. None of the other patients developed arm swelling or vascular steal. The brachial artery–brachial vein fistula is a feasible option for hemodialysis access and we suggest that this option be considered before a prosthetic arteriovenous graft is inserted. Arm swelling and steal have not been a problem, and all patients have been able to have full dialysis through the fistula after appropriate maturation times.

Pressure wave velocity (PWV) is commonly used as a clinical marker of vascular elasticity. Recent studies have increased clinical interest in also analyzing the impact of heart rate, blood pressure, and left ventricular ejection time on PWV. In this article we focus on the development of a theoretical one-dimensional model and validation via direct measurement of the impact of ejection time and peak pressure on PWV using an in vitro hemodynamic simulator. A simple nonlinear traveling wave model was developed for a compliant thin-walled elastic tube filled with an incompressible fluid. This model accounts for the convective fluid phenomena, elastic vessel deformation, radial motion, and inertia of the wall. An exact analytical solution for PWV is presented which incorporates peak pressure, ejection time, ejection volume, and modulus of elasticity. To assess arterial compliance, the solution is introduced in an alternative form, explicitly determining compliance of the wall as a function of the other variables. The model predicts PWV in good agreement with the measured values with a maximum difference of 3.0%. The results indicate an inverse quadratic relationship ([Formula: see text]) between ejection time and PWV, with ejection time dominating the PWV shifts (12%) over those observed with changes in peak pressure (2%). Our modeling and validation results both explain and support the emerging evidence that, both in clinical practice and clinical research, cardiac systolic function related variables should be regularly taken into account when interpreting arterial function indices, namely PWV.

INTRODUCTION: TEVAR has been seen to cause acute and chronic stent-induced tears of the adjacent aortic wall after treatment in 10-25% of cases with increasing frequency as the stent is placed closer to the aortic valve. The underlying cause for these tears and the ability to predict their occurrence is poorly understood. We hypothesize the cause of these tears is related to stent-induced changes in the adjacent aortic wall which could be quantified and predicted through finite element analysis (FEA) of stent-aorta interface. METHODS: Abaqus TM was used to resolve the FEA model of the stent-aorta interface in three configurations. The maximum principal stress in the vessel wall was averaged over the volume around the stent attachment point and the curvature of the stent was calculated at both the distal and proximal ends. (Figure 1). RESULTS: As the curvature of the attachment site increased, an increase in adjacent aortic wall stress was noted. These ranged from mean curvature (1/m) of 0.1 with wall stress of 49kPa for the distal attachment, position #2 to mean curvature of 6.7 and wall stress of 82kPa for the distal attachment site in position #3. There was an increase in maximum stress distribution as the TEVAR approached the aortic root of 104kPa, 109kPa, and 112kPa for positions 1-3 repectively. CONCLUSIONS: An increase in adjacent aortic wall stress and stress distribution was noted as TEVAR were placed closer to the aortic root which corresponds to the increase in stent-induced aortic tears observed in clinical series. This approach provides the basis for a predictive clinical tool to allow for patient-specific TEVAR planning with associated aortic wall stress analysis to minimize adjacent aortic trauma and assist in future stent design.

OBJECTIVES: Size-based assessments of AAA do not accurately identify rupture risk. AAA rupture potential is related to wall failure which is dependent on material properties and compliance. Our hypothesis is that transcutaneous ultrasound (US) regional strain measurements can be used to quantify changes in aortic wall mechanical properties indicative of an increase in rupture risk. METHODS: A patient-specific AAA cryogel phantom was fabricated and mechanical compliance and tested on an in vitro hemodynamic simulator. A Sonix-Touch system imaged the phantom through the maximum axial diameter under physiologic, pulsatile conditions with increasing mean arterial pressure (MAP) of 95, 120, 140, 160, and 180 until rupture (200mmHg). An US image registration algorithm was used to measure the circumferential wall strain from systole to diastole. RESULTS: The spatial mean of the circumferential wall strain (%) in the known location of rupture (solid box) decreased from 2.7, 2.0, 2.4, 1.7, 1.6, and 1.2 for MAP of 95, 120, 141, 160, 180 and 200 mm Hg (rupture) respectively. For comparison the mean strain levels in the adjacent wall of the aneurysm (dashed) were 3.4, 3.4, 3.0, 3.2, 2.1 and 1.8 for the same MAP. The mean diameter of the AAA increased from 5.48cm, 5.83cm, 6.13cm, 6.34cm, 6.54cm, and 6.69cm (rupture) over the range of MAP. CONCLUSIONS: At the location of eventual rupture, the mean regional strain decreased as the diameter of the phantom enlarged and progressed to rupture relative to other regions of the wall. This suggests the possibility of applying regional AAA wall strain as a more accurate method of predicting AAA rupture risk.

Presentamos el caso de un paciente de 90 anos de edad con aneurisma suprarrenal, infrarrenal, e iliaco bilateral con un aumento de diametro significativo durante el intervalo de seguimiento, tratado con colocacion de protesis endovascular. Debido a la importante angulacion del cuello del aneurisma infrarrenal, se detecto una endofuga de tipo 1a, que se trato satisfactoriamente con una extension o cuff aortico. Se uso una nueva tecnica de extension del cuff sobre una guia metalica angulada para acomodar la tortuosidad aortica. El caso de este paciente representa el primer informe publicado sobre el uso de esta tecnica para tratar las zonas de anclaje anguladas.

We present a case of a 90-year-old male with suprarenal, infrarenal, and bilateral iliac aneurysms with significant interval enlargement treated with an endovascular graft. Due to severe infrarenal neck angulation, a type 1a endoleak was encountered, which was successfully treated with an aortic cuff. A novel technique of cuff deployment over an angled guidewire to accommodate the aortic angulation was used. This represents the first report in the literature of using this technique to deal with difficult, angulated landing zones.

Nous presentons le cas d'un homme de 90 ans qui presentait un anevrysme a composantes supra-renale, infrarenale et iliaque bilaterale dont le traitement par endoprothese fut decide a cause d'une augmentation de volume. En raison d'une angulation severe du collet sous-renal, une endofuite de type 1a s'etait developpee mais elle fut traitee avec succes par la mise en place d'une extension proximale. L'endoprothese fut deployee suivant une technique originale utilisant un guide rigide angule, adapte a la tortuosite de l'aorte a ce niveau. Dans la litterature, il s'agit du premier rapport decrivant cette technique pour le traitement d'une pathologie aortique en zone tortueuse.

The current clinical management of abdominal aortic aneurysm (AAA) disease is based to a great extent on measuring the aneurysm maximum diameter to decide when timely intervention is required. Decades of clinical evidence show that aneurysm diameter is positively associated with the risk of rupture, but other parameters may also play a role in causing or predisposing the AAA to rupture. Geometric factors such as vessel tortuosity, intraluminal thrombus volume, and wall surface area are implicated in the differentiation of ruptured and unruptured AAAs. Biomechanical factors identified by means of computational modeling techniques, such as peak wall stress, have been positively correlated with rupture risk with a higher accuracy and sensitivity than maximum diameter alone. In the present work, we performed a controlled study targeted at evaluating the effect of uncertainty of the constitutive material model used for the vascular wall in the ensuing peak wall stress. Based on the outcome of this study, a second analysis was conducted based on the geometric characterization of surface curvature in two groups of aneurysm geometries, to discern which curvature metric can adequately discriminate ruptured from electively repaired AAA. The outcome of this work provides preliminary evidence on the importance of quantitative geometry characterization for AAA rupture risk assessment in the clinic.Copyright © 2013 by ASME

OBJECTIVES Unexplained aneurysm growth despite multimodality imaging following EVAR is often attributed to endotension. We tested a hypothesis that endotension may be from a type 1a endoleak (EL) pressurizing the aneurysm sac without net forward flow, not visualized on standard angiographic imaging. METHODS A patient-specific aortic aneurysm phantom was constructed of polyvinyl alcohol using 3D molding techniques. A bifurcated stent graft was implanted and the phantom connected to a hemodynamic simulator for testing. Type 1a ELs were created using 7 Fr catheters. Three scenarios were studied: complete exclusion (no EL); inflow with no sac outflow; and inflow with sac outflow. DSA imaging was performed at 48kvP at 5fps followed by delayed imaging (1 frame/min) over 30 minutes. RESULTS With no EL, the systemic MAP (sMAP) averaged 113mmHg and Aneurysm Sac MAP (asMAP) averaged 101mmHg. (Table 1) With EL without outflow, the sMAP averaged 116mmHg and asMAP averaged 120mmHg. EL flow was bidirectional with no net forward flow. With EL with aneurysm sac outflow, the sMAP averaged 119mmHg, asMAP averaged 105.5mmHg and net EL flow was +21cc/min across the EL channel. With DSA imaging, the EL with no outflow was noted after >9 min of delayed imaging. CONCLUSIONS Our model demonstrated a Type Ia EL in the absence of aneurysm sac outflow resulting in full pressurization of the aneurysm sac with biphasic (zero net) flow. This EL was not visible on standard contrast DSA until >9 min. This model may serve as a first step in explaining both the mystery of endotension and in vivo aneurysm sac growth with no detectable ELs using current standard imaging modalities.

Data mining techniques are capable of extracting important relationships and correlations among large amounts of data while machine learning methodologies can utilize these correlations to generate models capable of classification and prediction. The combination of machine learning and data mining is an important contribution of the present work for two reasons: (1) given a large database of features that describe the geometry of native abdominal aortic aneurysms (AAAs), patterns and relationships in the data are derived that may not be apparent to the human eye, and (2) statistical models are generated that can classify new data and determine which features discriminate among different aneurysm populations. The objectives of this study were to use anatomically realistic AAA models to evaluate a proposed set of global geometric indices describing the size, shape and individual wall thickness of the aneurysm sac, and use a learning algorithm to develop a model that is capable of discriminating the rupture status of these aneurysms.Copyright © 2012 by ASME

Objectives: Iliofemoral venous outflow stenting has been used to treat both acute and chronic venous thrombosis. It may be beneficial to understand the properties of the normal venous wall and the flow through collapsible tubes to develop new stent technology and improve long-term patency. We hypothesize that radial and circumferential strain can be modeled and measured using intravascular ultrasound (IVUS) techniques to describe venous geometry and asymmetric vessel wall characteristics. Methods: A hydrogel phantom was used to mimic the mechanical properties of a homogeneous vein, including geometry and wall compliance. Radio-frequency (RF) echo frames were acquired using a modified IVUS system with an 8.5 Mhz catheter. All RF signals were digitized to 14 bits at 50 MHz. Radial strain was estimated by applying an intensity matching, image registration based algorithm to the digitized frames. Results: The radial strain images (Figure 1) show increasing positive strain (radial wall thickening) on the top and bottom of the phantom with decreasing negative values (radial wall thinning) at either side. Results suggest an asymmetric compression pattern typical of a vessel collapsing under negative pressure. Conclusions: In conclusion, our data suggest that novel strain analysis can be performed on a phantom vessel consistent with the mechanical properties of the venous system. Further work with venous elastography will help define the mechanical properties of the venous wall and facilitate the development of new stent technology to treat venous disease.

OBJECTIVES: Current size-based assessments of AAA rupture potential do not accurately identify all patients at risk. True AAA rupture potential is related to hemodynamic and geometric factors involving wall strain and compliance. Our hypothesis is that transcutaneous ultrasound-derived strain measurements can identify heterogeneous aortic wall compliance toward predicting future rupture. METHODS: A latex phantom with changes in wall thickness (0.05-0.25 inches) to simulate AAA morphology was tested on an in vitro hemodynamic simulator. A GE Vivid i ultrasound machine interrogated the phantom under uniform physiologic, pulsatile conditions. The circumferential strain and radial strain of uniform wall phantom versus asymmetric wall phantom was quantified. RESULTS: Maximum circumferential strain (MCS) of the uniform wall thickness phantom was evenly distributed at 3.5% with an AP wall strain difference of 2.3% (Figure 1A). Maximum radial strain (MRS) was evenly distributed at 9% with an AP wall strain difference of 0%. MCS and MRS of the asymmetric wall thickness phantom were significantly increased to 30% and 36% respectively at the thinned anterior wall. AP wall strain difference was 22% (Figure 1B) and 10% respectively. CONCLUSIONS: Using transcutaneous 2D ultrasound, we were able to quantify changes in strain due to wall compliance in an AAA phantom. Further development of this technology may provide for a non-invasive method of characterizing the hemodynamic and geometric properties of an AAA to predict rupture potential.

OBJECTIVES: Contrast angiography can diagnose arterial occlusive disease but cannot provide hemodynamic data. Past work has attempted to calculate angiographic blood flow but clinical use has been limited by measurement error of >10%. Our hypothesis was that blood flow could be calculated from a contrast angiogram with METHODS: A pulsatile, in vitro hemodynamic simulator with a light-based angiographic imaging system (InfiMed, Inc.) was used as the testing platform. Flow rates were varied through increases in outflow resistance and were directly measured with a Transonic flow meter (+/-4% error). An algorithm was designed to determine instantaneous flow from DICOM images using a combination of automatic vessel detection, segmentation, and time of flight bolus tracking. These calculated flow rates were compared to those directly measured. RESULTS: The calculated flow rates (cc/min) were highly accurate when compared to those directly measured (4.1+/-3% error). Furthermore, time-density curves were accurate enough to detect relative changes in flow of 1.7 cc/sec reflecting changes in distal vascular resistance (Figure 1). CONCLUSION: We conclude that using this approach, blood flow can be angiographically measured with increased accuracy relative to prior work. This may provide clinically reliable hemodynamic data to guide diagnostic and therapeutic interventions.

Introduction: Arterial compliance is a marker for cardiac burden in atherosclerotic disease, with the pressure Pulse Wave Velocity (PWV) correlated to compliance. Current clinical practice employs pulsed wave Doppler to measure Flow Wave Velocity (FWV) as a surrogate of PWV. We hypothesized that PWV and FWV are not directly related and are affected by left ventricular ejection time (LVET). Furthermore, we proposed that aortic PWV is independent of mean arterial pressure (MAP) in the setting of isolated systolic hypertension. Methods: Using a physiologically accurate electromechanical cardiovascular simulator, two solid state manometer-tipped pressure transducers and two transit time flow sensors were located at the aortic root and at the aortic bifurcation. PWV and FWV were directly measured while individually varying contractility and thus LVET. The experiments were repeated at various systemic vascular resistances (SVR) and vascular compliances. Automated signal processing and data extraction techniques were used to calculate the key parameters. Results: As LVET increased, FWV decreased but PWV increased while MAP remained constant for a fixed SVR and compliance. (Figure 1) This trend held consistent at different SVR’s and compliances. The relationship of PWV and FWV with LVET appeared to be exponential and linear respectively. For a constant MAP, the associated PWV varied by up to 50m/s and FWV by up to 10m/s for a change in LVET of 225ms. Conclusions: In conclusion, our data shows that PWV and FWV appear to be inversely related. Our data also suggest that PWV and FWV are independent of MAP in the setting of isolated systolic hypertension. These findings suggest that FWV measured by pulsed wave Doppler may not be a simple surrogate for true PWV. Future work is needed to elucidate the hemodynamic principals governing the relationship between PWV and FWV.

Objectives: The molecular mechanisms leading to the development of Adnominal Aortic Aneurysms (AAA) remain poorly understood. Vascular Smooth Muscle Cells (VSMCs) are fundamental to maintaining a healthy arterial wall and changes in VSMC phenotype may be pivotal to aneurysm development. We have recently determined a role for a Hedgehog (Hh)/Notch signaling cascade in regulating adult VSMC phenotype. The aim of this study was to investigate Hh/Notch signaling components in aneurysmal and non-aneurysmal aorta. As crosstalk between Notch and Transforming Growth Factor Beta (TGFβ) has been postulated we also investigated expression of this growth factor. Methods: Tissue samples were obtained from aneurysmal and non-aneurysmal segments of the aortic wall of at least 5 patients with suitable anatomy undergoing open repair of infrarenal AAA. All samples analyzed were paired from the same patient with aneurysmal and non-aneurysmal specimens. Protein and mRNA expression levels were determined by western blot analysis and quantitative Real-time PCR respectively. Results: SHh, Notch 1 and 3 IC protein expression was decreased by at least 50% in aneurysmal tissue when compared to non-aneurysmal tissue. In addition, SHh mRNA expression was also decreased by 65%, while there was a decrease in Dll4, Notch 1 and Notch 3 by 66%, 57% and 54% respectively. In contrast, aneurysmal tissue had significantly increased expression of TGFβ and MMP9. TGFB protein and mRNA expression was significantly increased by 5.45±2.13 and 2.5±.2 fold respectively in aneurysmal tissue when compared to non-aneurysmal tissue. Furthermore, MMP9 mRNA expression was significantly increased by 4.7±1.6 fold. In parallel experiments, SMC alpha actin protein expression was significantly decreased by 90% in aneurysmal tissue when compared to non-aneurysmal tissue. Conclusion: These results suggest that SHH/Notch and TGFβ signaling is altered in aneurysmal tissue, compared with non-aneurysmal tissue. Changes in these signaling pathways and resulting changes in VSMC phenotype may play a role in the development of AAA.