Branch Vessel Involvement Research Articles

Predicting incomplete occlusion of intracranial aneurysms treated with flow diverters using machine learning models.

Intracranial saccular aneurysms are vascular malformations responsible for 80% of nontraumatic brain hemorrhage. Recently, flow diverters have been used as a less invasive therapeutic alternative for surgery. However, they fail to achieve complete occlusion after 6 months in 25% of cases. In this study, the authors built a tool, using machine learning (ML), to predict the aneurysm occlusion outcome 6 months after treatment with flow diverters. A total of 667 aneurysms in 616 patients treated with the Pipeline embolization device at a tertiary referral center between January 2011 and December 2017 were included. To build the predictive tool, two experiments were conducted. In the first experiment, six ML algorithms (support vector machine [SVM], decision tree, random forest [RF], k-nearest neighbor, XGBoost, and CatBoost) were trained using 26 features related to patient risk factors and aneurysm morphological characteristics, and the results were compared with logistic regression (LR) modeling. In the second experiment, the models were trained using the top 10 features extracted by Shapley additive explanation (SHAP) analysis performed on the RF model. The results showed that the authors' tool can better predict the occlusion outcome than LR (accuracy of 89% for the SVM model vs 62% for the LR model), even when trained using a subset of the features (83% accuracy). SHAP analysis revealed that age, hypertension, smoking status, branch vessel involvement, aneurysm neck, and larger diameter dimensions were among the most important features contributing to accurate predictions. In this study, an ML-based tool was developed that successfully predicts outcome in intracranial aneurysms treated with flow diversion, thus helping neurosurgeons to practice a more refined approach and patient-tailored medicine.

Prognostic impact of branch vessel involvement on organ malperfusion and mid-term survival in patients with acute type A aortic dissection

BackgroundThis study aimed to investigate the impact of branch vessel involvement on organ malperfusion and mid-term survival in patients with acute type A aortic dissection (ATAAD). MethodsBetween January 2019 and December 2020, 493 consecutive patients with angiographically confirmed ATAAD were retrospectively analysed. Preoperative computed tomography angiography parameters (branch artery involvement, longitudinal extent of dissection) were reviewed. The incidence of organ malperfusion, in-hospital mortality, and mid-term outcomes of patients with and without branch vessel involvement were compared. ResultsBranch vessel involvement was detected in 407 patients (82.6%), and organ malperfusion was observed in 234 patients (47.5%). The incidence of organ malperfusion was significantly higher in patients with branch vessel involvement compared with patients without it (52.6% vs. 23.3%, p < 0.001). Patients with coronary artery involvement (32.5%) were more likely to manifest as clinical malperfusion, whereas it occurred only 19.4% in patients with renal artery involvement. In-hospital mortality was higher in patients with branch vessel involvement (19.9% vs. 8.1%, p = 0.010). Median follow-up time was 16.1 months. Two-year survival rate was lower in patients with branch vessel involvement (76.3% vs. 84.5%, p = 0.085) or organ malperfusion (68.3% vs. 86.0%, p < 0.001). Multivariable analysis identified cardiac, cerebral, visceral and renal malperfusion as independent predictors for in-hospital mortality. ConclusionsOnly a small proportion of branch vessel involvement was associated with corresponding organ malperfusion in patients with ATAAD. Branch vessel involvement had a greater effect on short-term outcomes than mid-term survival, and organ malperfusion was related to a worse prognosis beyond it.

Location of the False Lumen Within the Medial Layer in Acute Intramural Hematoma.

We compared the location of the false lumen within the medial layer between acute intramural hematoma (AIH) and acute aortic dissection (AAD) using microscopic images of aortic specimens and examined the associations with patient characteristics, CT findings, and late outcomes. Among 293 patients undergoing surgery for Stanford type A acute aortic syndrome between 2008 and 2018, 45 patients had neither an identifiable intimal tear, flow to the false lumen on preoperative CT or intimal tear by intraoperative observation (AIH group), and 98 patients with patent false lumen were enrolled (AAD group). The AIH group had a significantly thinner outer media thickness (OMT) than the AAD group. The AIH group showed more pericardial effusion, but distal progression of dissection and branch vessel involvement were limited. The change in aortic diameter after surgery was insignificant in the AIH group, whereas in the AAD group it continued to increase. Cumulative incidence of aortic adverse events was significantly higher among AAD patients, but no significant difference was observed in survival between groups. The AIH group had a significantly thinner OMT than the AAD group, which was significantly associated with a large amount of pericardial effusion, greater false lumen diameter, and limited progression of aortic dissection.

Thoracic Endovascular Aortic Repair for Chronic Type B Aortic Dissection: Pre- and Postprocedural Imaging.

Aortic dissection is a chronic disease that requires lifelong clinical and imaging surveillance, long after the acute event. Imaging has an important role in prognosis, timing of repair, device sizing, and monitoring for complications, especially in the endovascular therapy era. Important anatomic features at preprocedural imaging include the location of the primary intimal tear and aortic zonal and branch vessel involvement, which influence the treatment strategy. Challenges of repair in the chronic phase include a small true lumen in conjunction with a stiff intimal flap, complex anatomy, and retrograde perfusion from distal reentry tears. The role of thoracic endovascular aortic repair (TEVAR) remains controversial for treatment of chronic aortic dissection. Standard TEVAR is aimed at excluding the primary intimal tear to decrease false lumen perfusion, induce false lumen thrombosis, promote aortic remodeling, and prevent aortic growth. In addition to covering the primary intimal tear with an endograft, several adjunctive techniques have been developed to mitigate retrograde false lumen perfusion. These techniques are broadly categorized into false lumen obliteration and landing zone optimization strategies, such as the provisional extension to induce complete attachment (PETTICOAT), false lumen embolization, cheese-wire fenestration, and knickerbocker techniques. Familiarity with these techniques is important to recognize expected changes and complications at postintervention imaging. The authors detail imaging options, provide examples of simple and complex endovascular repairs of aortic dissections, and highlight complications that can be associated with various techniques. Online supplemental material is available for this article. ©RSNA, 2022.

Midaortic syndrome and renovascular hypertension

Midaortic syndrome (MAS) is a rare condition characterized by stenosis of the abdominal aorta with or without the involvement of branch vessels. The majority of cases are thought to be idiopathic though MAS has been associated with a number of conditions including granulomatous vasculitis, neurofibromatosis-1 (NF-1), Alagille Syndrome, fibromuscular dysplasia (FMD), and Williams syndrome. Patients typically present with hypertension due to decreased renal perfusion. Less common presentations include renal insufficiency, heart failure, claudication, stroke, and abdominal pain. Imaging modalities help establish the diagnosis of MAS including duplex ultrasound, computed tomography angiography (CTA), magnetic resonance angiography (MRA), and angiography. Initial therapy focuses on medical management with antihypertensives prior to intervention. Invasive interventions are indicated when there is evidence of end organ damage or dysfunction such as decreased renal function, poorly growing kidneys, cerebrovascular accident, left ventricular hypertrophy or frank cardiac failure. Endovascular interventions may assist in diagnosis and may treat some lesions although reintervention rates are high. Most patients require some type of surgical intervention, and a variety of surgical options are available based on anatomic findings. Renal revascularization may be accomplished by renal artery bypass, autotransplantation, or renal artery reconstruction. Aortic lesions may be repaired using patch angioplasty or aortoaortic bypass. Mesenteric arteries do not typically require reconstruction as they are rarely symptomatic. More novel options include the use of tissue expanders to lengthen the aorta to allow for primary aortic reconstruction (TESLA) or the use of the meandering mesenteric artery as an autologous aortic bypass graft (MAGIC).

Prognostic Impact of Branch Vessel Involvement on Computed Tomography versus Clinical Presentation of Malperfusion in Patients With Type a Acute Aortic Dissection

Type A acute aortic dissection (AAD) is a life-threatening disease. The use of contrast-enhanced computed tomography (CT) for diagnosing AAD has increased, and CT can provide pathophysiologic information on dissection such as intramural hematoma (IMH), longitudinal extent of dissection, and branch vessel involvement. However, the prognostic impact of these CT findings is poorly investigated. This multicenter registry included 703 patients with type A AAD. The longitudinal extent of dissection and IMH was determined on CT. Branch vessel involvement was defined as dissection extended into coronary, cerebral, and visceral arteries on CT. The evidence of malperfusion was defined based on clinical presentations. The primary endpoint was in-hospital death. Of 703 patients, 126 (18%) died during hospitalization. Based on contrast-enhanced CT findings, longitudinal extent of dissection was not associated with in-hospital death, while patients with IMH had lower in-hospital mortality than those without (13% vs 22%, p=0.004). Coronary, cerebral, and visceral artery involvement on CT was found in 6%, 55%, and 32%. In patients with coronary artery involvement, 90% had clinical coronary malperfusion, while only 25% and 21% of patients with cerebral and visceral artery involvement had clinical evidence of corresponding organ malperfusion. Multivariable analysis showed evidence of malperfusion as a significant factor associated with in-hospital mortality. In conclusions, branch vessel involvement on CT was not always associated with end-organ malperfusion in patients with type A AAD, especially in cerebral and visceral arteries. Clinical evidence of malperfusion was significantly associated with in-hospital mortality beyond branch vessel involvement on CT.

Noninvasive Morphologic and Hemodynamic Evaluation of Type B Aortic Dissection: State of the Art and Future Perspectives.

Stanford type B aortic dissection (TBAD) is associated with relatively high rates of morbidity and mortality, and appropriate treatment selection is important for optimizing patient outcomes. Depending on individualized risk factors, clinical presentation, and imaging findings, patients are generally stratified to optimal medical therapy anchored by antihypertensives or thoracic endovascular aortic repair (TEVAR). Using standard anatomic imaging with CT or MRI, several high-risk features including aortic diameter, false lumen (FL) features, size of entry tears, involvement of major aortic branch vessels, or evidence of visceral malperfusion have been used to select patients likely to benefit from TEVAR. However, even with these measures, the number needed to treat for TEVAR remains, and improved risk stratification is needed. Increasingly, the relationship between FL hemodynamics and adverse aortic remodeling in TBAD has been studied, and evolving noninvasive techniques can measure numerous FL hemodynamic parameters that may improve risk stratification. In addition to summarizing the current clinical state of the art for morphologic TBAD evaluation, this review provides a detailed overview of noninvasive methods for TBAD hemodynamics characterization, including computational fluid dynamics and four-dimensional flow MRI. Keywords: CT, Image Postprocessing, MRI, Cardiac, Vascular, Aorta, Dissection © RSNA, 2021.

Game changers in vascular and endovascular surgery

Game changers in vascular and endovascular surgery

Strategy for the Treatment of Spontaneous Isolated Visceral Artery Dissection

Abstract Objectives To determine the incidence of rare spontaneous isolated visceral artery dissection (SIVAD), characterize its pathogenesis, and suggest treatment strategies. Materials and Methods We reviewed abdominal contrast-enhanced computed-tomography (CE-CT) scans from January 2005 to December 2016 retrospectively in our institution, identified 47 SIVAD patients and classified them into a symptomatic (n = 22) or asymptomatic group (n = 25). Further, we classified the five types based on the CE-CT images. Patient characteristics, incidence, vascular risk factors, complications, symptoms, treatments outcomes, and morphology features on CE-CT images were analyzed. Results SIVAD was seen on 0.09% of all abdominal CE-CT scans, and 0.68% of all abdominal CT-CT scans obtained for the evaluation of acute abdominal symptoms. The asymptomatic group had significantly fewer patients with periarterial fat stranding or branch vessel involvement on CE-CT images (p Conclusions Symptomatic SIVAD patients should be hospitalized because some of those may experience organ ischemia or aneurysm formation. Endovascular intervention is a feasible treatment for complications of SIVAD.

Strategy for the treatment of spontaneous isolated visceral artery dissection

ObjectivesTo determine the incidence of rare spontaneous isolated visceral artery dissection (SIVAD), characterize its pathogenesis, and suggest treatment strategies. Materials and MethodsWe reviewed abdominal contrast-enhanced computed-tomography (CE-CT) scans from January 2005 to December 2016 retrospectively in our institution, identified 47 SIVAD patients and classified them into a symptomatic (n = 22) or asymptomatic group (n = 25). Further, we classified the five types based on the CE-CT images. Patient characteristics, incidence, vascular risk factors, complications, symptoms, treatments outcomes, and morphology features on CE-CT images were analyzed. ResultsSIVAD was seen on 0.09% of all abdominal CE-CT scans, and 0.68% of all abdominal CT-CT scans obtained for the evaluation of acute abdominal symptoms. The asymptomatic group had significantly fewer patients with periarterial fat stranding or branch vessel involvement on CE-CT images (p < 0.01). The mean length of the dissection was longer in the symptomatic group (p < 0.05). In the asymptomatic group, dissection-related abdominal symptoms and complications did not develop; followed-up CE-CT scans showed improvement in the dissection lesions in 1 (4.0%) patient, no changes in 22 (88.0%), and complete remodeling in 2 (8.0%). In the symptomatic group, one patient presented with organ ischemia at diagnosis and five patients developed organ ischemia underwent endovascular intervention. In the remaining 16 patients received nonoperative intervention only, followed-up CE-CT scans showed improvement in 13 (86.7%), and complete remodeling in 2 (13.3%). ConclusionsSymptomatic SIVAD patients should be hospitalized because some of those may experience organ ischemia or aneurysm formation. Endovascular intervention is a feasible treatment for complications of SIVAD.

Outcomes Among Patients Undergoing Distal Left Main Percutaneous Coronary Intervention.

Distal left main (LM) coronary artery bifurcation disease increases percutaneous coronary intervention (PCI) procedural complexity and is associated with worse outcomes than isolated ostial/shaft disease. The optimal treatment strategy for distal LM disease is undetermined. We sought to determine whether outcomes after PCI of LM distal bifurcation lesions are influenced by treatment with a provisional 1-stent versus planned 2-stent technique, and if so, whether such differences are conditioned by the complexity of the LM bifurcation lesion. The clinical and angiographic characteristics, procedural methods and outcomes, and clinical events through 3-year follow-up were compared in patients undergoing distal LM PCI with a 1-stent provisional versus planned 2-stent technique in the EXCEL trial (Evaluation of XIENCE Versus Coronary Artery Bypass Surgery for Effectiveness of Left Main Revascularization). Among 529 patients undergoing planned distal LM PCI, 344 (65.0%) and 185 (35.0%) were treated with intended 1-stent provisional and planned 2-stent techniques, respectively. The primary composite end point rate of death, myocardial infarction, or stroke at 3 years was significantly lower in patients treated with the provisional 1-stent versus planned 2-stent method (14.1% versus 20.7%; adjusted hazard ratio, 0.55; 95% CI, 0.35-0.88; P=0.01), driven by differences in cardiovascular death (3.3% versus 8.3%, P=0.01) and myocardial infarction (7.7% versus 12.8%, P=0.06). The 3-year rate of ischemia-driven revascularization of the LM complex was also lower in the provisional group (7.2% versus 16.3%, P=0.001). In 342 patients with distal LM bifurcation disease that did not involve both major side branch vessels, the 3-year primary end point was lower with a provisional 1-stent versus planned 2-stent technique (13.8% versus 23.3%, P=0.04), whereas no significant difference was present in 182 patients with distal LM bifurcation disease that did involve both side branch vessels (14.3% versus 19.2%, P=0.36). Among patients with distal LM bifurcation disease in the EXCEL trial randomized to PCI, 3-year adverse outcomes were worse with planned 2-stent treatment compared with a provisional 1-stent approach, a difference that was confined to patients without major involvement of both LM side branch vessels. URL: https://www.clinicaltrials.gov . Unique identifier: NCT01205776.

Comparison of CTA and DSA in the diagnosis of superior mesenteric artery dissecting aneurysm.

Objective To compare computed tomography arteriography (CTA) and digital subtraction arteriography (DSA) in the diagnosis of superior mesenteric artery dissecting aneurysm (SMADA). Methods All SMADA patients who underwent CTA and DSA at one of two medical centers between May, 2007 and April, 2017 were identified. The accuracy of CTA and DSA for the depiction of morphologic characteristics of SMADA was analyzed. Results Fourteen patients (12 men; mean age, 55.1 ± 6.4 years) were included in this study. The mean diameter of the dissecting aneurysm was 3.78 ± 1.53 mm on CTA and 3.81 ± 1.54 mm on DSA ( p = 0.96). The luminal stenosis was 0.52 ± 0.27 on CTA and 0.35 ± 0.23 on DSA ( p = 0.09). The thrombosed false lumen was visualized on CTA in 79% (11/14) of patients but in no patients on DSA ( p < 0.001). The entry points of the dissection were visualized on CTA in 64.3% (9/14) of patients and on DSA in 100% (14/14) of patients ( p = 0.041); CTA and DSA did not visualize re-entry points in any patients. The intimal flap was visualized on CTA in 71.4% (10/14) of patients and on DSA in 78.6% (11/14) of patients ( p > 0.05). Branch vessel involvement was visualized in 7.1% (1/14) of patients on CTA but in no patients on DSA ( p > 0.05). Conclusions CTA can be used in place of DSA for the diagnosis of SMADA. Although CTA may exaggerate the degree of luminal stenosis and is weak in depicting the entry points of SMADA, this modality more accurately depicts the thrombosed false lumen and branch vessel involvement.

Usefulness of triphasic CT aortic angiography in acute and surveillance: Our experience in the assessment of acute aortic dissection and endoleak

IntroductionComputed tomography angiography (CTA) has been widely used in the diagnostic evaluation of many aortic diseases, but no standardized techniques actually exist for aortic CTA. The aim of this study was to describe the usefulness of triphasic CTA in aortic assessment in both non-traumatic emergency and surveillance conditions. MethodsWe performed non ECG-gated CTA examinations with a 64-slice CT scanner using a triphasic protocol consisting of an unenhanced acquisition, and two (early and delayed) contrastographic phases with a delay of 25–30 s and 100–120 s respectively after the injection of contrast medium. Were retrospectively selected adult patients with imaging findings of acute aortic dissection (AAD) or endoleak (EL) from November 2012 to November 2014. ResultsAAD was detected in 36 (67%) patients: 23 type A-AADs, and 13 type B-AADs. The presence of EL was observed in 18 (33%) patients: 1 type Ia, 5 types IIa, 2 types IIb, 1 type IIIa and 9 types IIIb. DiscussionTriphasic CTA is useful to provide correct and prompt diagnosis of AAD in emergency, allowing the evaluation of type and atypical forms of AAD, and the identification of possible branch-vessel involvement and complications. During surveillance, triphasic CTA assures accurate and complete assessment of all known and unknown ELs and it is essential for first follow-up examination. ConclusionTriphasic CTA represents a reliable imaging tool for aortic assessment in both non-traumatic emergency and surveillance after endovascular aneurysm repair. Modified protocol could be employed in selected patients and tailored in their known disease.

Treatment of Ruptured Anterior Communicating Artery Aneurysms: Equipoise in the Endovascular Era?

Ruptured anterior communicating artery (ACoA) aneurysms are heterogeneous intracranial aneurysms whose diverse morphological features influence treatment modality. To compare clinical outcomes and complications of all ruptured ACoA aneurysms treated by clipping or coiling in a modern institutional trial. All patients with ruptured ACoA aneurysms in the Barrow Ruptured Aneurysm Trial were included. Clinical follow-up at 1 and 3 years was analyzed; charts were reviewed for patient demographics, aneurysm characteristics, and in-hospital complications. This cohort included 130 patients (mean age, 52.5 years). Mean aneurysm size was 5.8 mm. Most aneurysm domes projected anteriorly (n = 52). After randomization and crossover, 91 ACoA aneurysms (70%) were clipped and 39 (30%) were coiled. Twenty-two patients (16.9%) initially randomized to coiling crossed over to clipping after evaluation. No patients crossed over from clipping to coiling. Characteristics precluding aneurysms from coiling included unfavorable dome-to-neck ratio, lesions difficult to access by catheter, and branch vessel involvement. Aneurysm size and dome projection were not significantly associated with treatment group, clinical outcome, or retreatment. No significant difference existed in clinical outcome (modified Rankin Scale scores) between groups at discharge or at 1-year or 3-year follow-up using as-treated and intention-to-treat analyses. Retreatment was performed in 3 clipped patients (2.3%) and 3 coiled patients (2.3%). Ruptured ACoA aneurysms, regardless of size and projection, were safely treated by both treatment modalities in a large-scale randomized clinical trial. Clinical outcomes and stroke rates did not differ significantly in as-treated or intention-to-treat analyses.

Predictors of false lumen thrombosis in type B aortic dissection treated with TEVAR.

Thoracic endovascular aortic repair (TEVAR) offers a less invasive treatment option in type B aortic dissection (TBAD) patients and its value has been demonstrated in acute and chronic dissection patients. Total false lumen thrombosis (FLT) is associated with better long-term outcome in these patients, however, this is not obtained in all patients. The purpose of this study was to investigate predictors of FLT. We retrospectively investigated patients who underwent TEVAR for a type B dissection in a large referral center between 2005 and 2012. All patients with a CT angiogram (CTA) obtained preoperatively, postoperatively and after one year of follow-up were selected for analysis. Volume measurements and several morphologic characteristics were analyzed for all scans using Aquarius iNtuition software (TeraRecon, San Mateo, Calif, USA). Multivariate logistic regression analyses were used to study the influence of these characteristics on FLT. Of 132 patients that received TEVAR for an aortic dissection, 43 patients (mean age, 60.3±14.2; 30 male) met our inclusion criteria, of whom 16 (37%) developed full FLT after 1 yr of follow-up. Multivariate logistic regression showed that side branch involvement [odds ratio (OR), 0.03; 95% confidence interval (CI), 0.00-0.92; P=0.045] and a total patent false lumen (FL) at presentation (OR, 0.01; 95% CI, 0.00-0.58; P=0.027) were associated with decreased complete FLT. Volumetric data showed significantly more reduction of the thoracic false lumen in FLT patients compared with non-FLT (-52.3% vs. -32.4%; P=0.043) and also a tendency of less volume increase in the abdominal segment (-5.0±37.5 vs. 21.8±44.3; P=0.052). Patients admitted with type B dissection and branch vessel involvement or a patent entry tear after TEVAR are less likely to develop FLT and aortic remodeling during follow-up. These findings suggest that these patients may require a more extensive procedure and more intensive follow-up to prevent long-term complications.

Spontaneous Dissection of the Splanchnic Arteries: CT Findings, Treatment, and Outcome

The purpose of this study was to describe the various CT findings of isolated spontaneous splanchnic artery dissection and the treatment options and outcomes. From January 1999 to May 2008, splanchnic artery dissection was diagnosed through CT angiography in 34 patients (28 men, six women) without recent trauma or aortic disease. All patients were classified as having either symptomatic (n = 19) or asymptomatic (n = 15) dissection. We analyzed imaging findings of intimal flap, aneurysmal dilatation, thrombosed false lumen, periarterial fatty infiltration, branch vessel involvement, bowel ischemic signs, and the extent of involvement of each artery with each treatment method and the outcomes. Intimal flap (n = 37 [88.1%]; symptomatic, 22; asymptomatic, 15), thrombosed false lumen (n = 27 [64.3%]; symptomatic, 19; asymptomatic, 8), and aneurysmal dilatation (n = 22 [52.4%]; symptomatic, 14; asymptomatic, 8) were seen. Periarterial fatty infiltration and branch vessel involvement differed between the symptomatic and asymptomatic groups (p < 0.01). Renal artery dissection was found in six patients (symptomatic, 3; asymptomatic, 3). Six patients were lost to follow-up. Treatments included conservative management without anticoagulation therapy (n = 19; symptomatic, 8; asymptomatic, 11), endovascular stent insertions (n = 6; symptomatic, 6; asymptomatic, 0), and surgery (n = 3; symptomatic, 3; asymptomatic, 0). Patients with a follow-up interval of more than 10 days had disease in a stationary state (n = 14; symptomatic, 4; asymptomatic, 10), were in improved condition (n = 12; symptomatic, 11; asymptomatic, 1), or had progression of disease (n = 2; symptomatic, 2; asymptomatic, 0). Intimal flap, thrombosed false lumen, and aneurysmal dilatation are the most common CT findings of spontaneous splanchnic artery dissection. In splanchnic artery dissection, conservative management without anticoagulation had good outcome except in patients with bowel ischemia, aneurysmal dilatation three times larger than a normal segment, or progression of dissection.

Acute Aortic Emergencies—Part 2 Aortic Dissections

Patients with aortic disease are some of the highest acuity patients that emergency clinicians encounter. Dissection is the most common aortic catastrophe and involves separation of the aortic layers in a longitudinal fashion leading to diminished perfusion and systemic ischemia. Characteristics of pain, branch vessel involvement, and incidence lead to an understanding of patient presentation, morbidity, and mortality. Diagnosis, selection of diagnostic studies, the degree of preoperative ischemia, and risk of operative mortality can be accomplished using validated clinical decision tools. Emergency interventions are guided by the type of dissection according to the Stanford classification system. Medical management includes pain control and anti-impulse, antihypertensive therapy through vasodilatation and blockage of the sympathetic β-response. The patient may then be evaluated for open surgical intervention, aortic fenestration, endovascularly placed stent grafts, or a combination possibly in a staged approach. Morbidity includes rupture, stroke, paraplegia, acute renal failure, bowel ischemia, and peripheral ischemia.

ACR Appropriateness Criteria® pulsatile abdominal mass, suspected abdominal aortic aneurysm

Clinical palpation of a pulsating abdominal mass alerts the clinician to the presence of a possible abdominal aortic aneurysm (AAA). Generally an arterial aneurysm is defined as a localized arterial dilatation ≥50 % greater than the normal diameter. Imaging studies are important in diagnosing the cause of a pulsatile abdominal mass and, if an AAA is found, in determining its size and involvement of abdominal branches. Ultrasound (US) is the initial imaging modality of choice when a pulsatile abdominal mass is present. Noncontrast computed tomography (CT) may be substituted in patients for whom US is not suitable. When aneurysms have reached the size threshold for intervention or are clinically symptomatic, contrast-enhanced multidetector CT angiography (CTA) is the best diagnostic and preintervention planning study, accurately delineating the location, size, and extent of aneurysm and the involvement of branch vessels. Magnetic resonance angiography (MRA) may be substituted if CT cannot be performed. Catheter arteriography has some utility in patients with significant contraindications to both CTA and MRA. The American College of Radiology Appropriateness Criteria® are evidence-based guidelines for specific clinical conditions that are reviewed every 2 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 where evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

Aortic dissection and malperfusion syndrome: a when, what and how-to guide

Malperfusion syndrome is a complication of aortic dissection caused by branch-vessel involvement and resulting in end-organ ischaemic dysfunction. Clinical diagnosis is mandatory, and imaging plays a critical role in confirmation and treatment planning. Radiologists must focus on detecting complications (findings of aortic dilation, rupture, organ ischaemia, etc.) and defining vascular compromise and associated malperfusion mechanisms. All these factors guide the multidisciplinary discussion concerning patient management and the suitability of endovascular treatment. Application of dedicated imaging protocols is mandatory in order to answer clinical and anatomical questions. Endovascular therapy has taken a predominant role in the therapeutic management of malperfusion syndrome with aortic fenestration, peripheral stenting and stent-grafting, all of which are procedures within the domain of expertise of current interventional radiologists. The purpose of this editorial is to present a when, what and how-to guide for all radiologists who encounter complicated aortic dissection.

Volumetric analysis of type B aortic dissections treated with thoracic endovascular aortic repair

Type B aortic dissections are being successfully treated by thoracic endovascular aortic repair (TEVAR). Postoperative false lumen patency has been associated with aneurysmal dilatation and rupture of the thoracic aorta, necessitating further intervention. This is the first volumetric analysis of type B aortic dissections comparing patients with and without false lumen thrombosis (FLT) after TEVAR. We hypothesized that a greater increase in postoperative true lumen volume will lead to FLT, and without this change, false lumen patency will result. Preoperative and postoperative computed tomography angiography (CTA) imaging was analyzed using three-dimensional reconstruction to measure the short- and long-axis diameter and cross-sectional area of the true lumen, false lumen, and total aorta. Measurements were taken at 5-cm intervals from the left subclavian artery to the aortic bifurcation. Pre- and postoperative volumetric data were calculated and compared in patients with and without postoperative FLT. Between 2006 and 2010, 132 patients underwent thoracic aortic stent grafting. Of these, 31 (23%) had thoracic endografting for type B aortic dissection. Pre- and postoperative CTA images were available for analysis in 23 patients with a mean age of 59 ± 14 years treated for acute, complicated (n = 8, 35%), and chronic (n = 15, 65%) indications. Mean follow-up imaging was 9 months (range, 1-39 months). Thirteen patients (56%) had postoperative FLT and 10 (43%) had persistent false lumen patency. The dissections involved the left subclavian artery (n = 12), visceral arteries (n = 14), renal arteries (n = 16), and iliac arteries (n = 15). The left subclavian artery was intentionally covered in 15 patients (65%). There were no significant differences in age, acute vs chronic dissection, branch vessel involvement, coverage of the left subclavian artery, or distal extent of the endograft between patients with and without postoperative FLT. Patients with postoperative FLT had a significantly smaller preoperative maximum thoracic aortic diameter (5.05 ± 1.0 vs 6.30 ± 1.4 cm; P = .02). Volumetric analysis demonstrated significantly smaller preoperative true lumen volume (141.3 ± 68 vs 230.5 ± 92 cm(3); P = .01) in patients with FLT, but no difference in preoperative false lumen volume. Patients with FLT had a significant increase in the volume percentage of the true lumen from 42.7% to 61.7% (P = .02) after stent graft repair, compared with an increase from 46.7% to 47.7% (P = .75) in patients with persistent false lumen patency. This volumetric study of type B aortic dissection treated with TEVAR suggests that the ability of the endograft to significantly increase the true lumen volume as a percent of the total aorta most accurately predicts postoperative FLT. This is best demonstrated in a nonaneurysmal dissection regardless of timing since dissection.