Rachel E. Clough

Endovascular Repair of Acute Uncomplicated Aortic Type B Dissection Promotes Aortic Remodelling: 1 Year Results of the ADSORB Trial

OBJECTIVES Uncomplicated acute type B aortic dissection (AD) treated conservatively has a 10% 30-day mortality and up to 25% need intervention within 4 years. In complicated AD, stent grafts have been encouraging. The aim of the present prospective randomised trial was to compare best medical treatment (BMT) with BMT and Gore TAG stent graft in patients with uncomplicated AD. The primary endpoint was a combination of incomplete/no false lumen thrombosis, aortic dilatation, or aortic rupture at 1 year. METHODS The AD history had to be less than 14 days, and exclusion criteria were rupture, impending rupture, malperfusion. Of the 61 patients randomised, 80% were DeBakey type IIIB. RESULTS Thirty-one patients were randomised to the BMT group and 30 to the BMT+TAG group. Mean age was 63 years for both groups. The left subclavian artery was completely covered in 47% and in part in 17% of the cases. During the first 30 days, no deaths occurred in either group, but there were three crossovers from the BMT to the BMT+TAG group, all due to progression of disease within 1 week. There were two withdrawals from the BMT+TAG group. At the 1-year follow up there had been another two failures in the BMT group: one malperfusion and one aneurysm formation (p = .056 for all). One death occurred in the BMT+TAG group. For the overall endpoint BMT+TAG was significantly different from BMT only (p < .001). Incomplete false lumen thrombosis, was found in 13 (43%) of the TAG+BMT group and 30 (97%) of the BMT group (p < .001). The false lumen reduced in size in the BMT+TAG group (p < .001) whereas in the BMT group it increased. The true lumen increased in the BMT+TAG (p < .001) whereas in the BMT group it remained unchanged. The overall transverse diameter was the same at the beginning and after 1 year in the BMT group (42.1 mm), but in the BMT+TAG it decreased (38.8 mm; p = .062). CONCLUSIONS Uncomplicated AD can be safely treated with the Gore TAG device. Remodelling with thrombosis of the false lumen and reduction of its diameter is induced by the stent graft, but long term results are needed.

Is endovascular repair of mycotic aortic aneurysms a durable treatment option

OBJECTIVE Endovascular repair for degenerative aortic aneurysms is well established, but its role in those with infective pathology remains controversial. This study aims to assess the durability of endovascular repair with a review of our midterm results. METHOD A retrospective analysis of a prospectively maintained endovascular database (1998-2008) was conducted, which identified 673 consecutive patients with aortic aneurysms. RESULTS Nineteen patients (2.8%) were identified with infected aortic aneurysms, in which there were a total of 23 separate aneurysms (16 thoracic and seven abdominal). Six patients (32%) presented with rupture. Eleven patients (58%) had received antibiotics preoperatively for a median duration of 11 days (1-54 days). Fifteen of the 19 (79%) had positive blood cultures, with Staphylococcus aureus being the most common organism. All 19 patients underwent endovascular repair. There were three Type I endoleaks (one requiring conversion to open repair) and two Type II endoleaks. One patient developed transient paraplegia, resolved by cerebrovascular fluid (CSF) drainage, and one patient had a stroke. The 30-day mortality was 11%, and survival at median follow-up of 20 months (0-83 months) was 73%. All eight deaths in the series were related to aneurysm. CONCLUSION Endovascular treatment of infective aortic pathology provides an early survival benefit; however, concerns over on-going graft infection remain.

Management of acute aortic dissection.

A new appraisal of the management of acute aortic dissection is timely because of recent developments in diagnostic strategies (including biomarkers and imaging), endograft design, and surgical treatment, which have led to a better understanding of the epidemiology, risk factors, and molecular nature of aortic dissection. Although open surgery is the main treatment for proximal aortic repair, use of endovascular management is now established for complicated distal dissection and distal arch repair, and has recently been discussed as a pre-emptive measure to avoid late complications by inducing aortic remodelling.

A new imaging method for assessment of aortic dissection using four-dimensional phase contrast magnetic resonance imaging

INTRODUCTION Medical management of type B aortic dissection can result in progressive dilation of the false lumen and poor long-term outcome. Recent studies using models of aortic dissection have suggested flow characteristics, such as stroke volume, velocity, and helicity, are related to aortic expansion. The aim of this study was to assess whether four-dimensional phase-contrast magnetic resonance imaging (4D PC-MRI) can accurately visualize and quantify flow characteristics in patients with aortic dissection and whether these features are related to the rate of aortic expansion. METHODS Twelve consecutive patients with medically treated type B thoracic aortic dissection underwent a three-dimensional (3D) MRI anatomy scan using a blood pool contrast agent. Two-dimensional phase contrast MRI data (2D PC-MRI) were acquired in the ascending and descending aorta and 4D PC-MRI data were acquired in the entire thoracic aorta. The 2D PC-MRI measurements were used to assess the quality of the 4D PC-MRI velocity data. Stroke volume, velocity, and the direction of flow were calculated using 4D PC-MRI and related to the rate of aortic expansion measured on contrast-enhanced computed tomography. RESULTS Comparison of 2D PC-MRI and 4D PC-MRI measurements showed good correlation (Pearson R(2) = 0.98; 95% confidence interval [CI], 0.9818-0.9953; P < .0001) and no proportional bias (bias = 1.0 mL; standard deviation, 4.6). The median aortic growth rate was 6.1 mm/y (interquartile range [IQR], 1.1-15.1 mm/y), and this correlated well with the growth rate of the false lumen (Spearman ρ = 0.62; 95% CI, 0.06-0.89; P = .0347). False lumen thrombosis (FLT) was seen in 7 of 12 patients and was not associated with reduced aortic expansion rate (FLT present: 11.4 mm/y; IQR, 3.6-21.4) vs FLT absent: 9.9 mm/y; IQR, 3.4-24.2; Mann-Whitney P = .8763). False lumen stroke volume and velocity were associated with more rapid aortic expansion (ρ = 0.80 [95% CI, 0.39-0.94; P = .0029] and ρ = 0.59 [95% CI, 0.09-0.87; P = .0480] respectively). The position of the dominant entry tear was associated with rapid expansion, which tended to be higher with distal vs proximal entry tears (distal, 21.4 mm/y [IQR, 11.4-48.9] vs proximal, 5.5 mm/y [IQR, 3.4-16.6]; Mann-Whitney P = .096). Helical flow was seen in the false lumen in 8 of 12 patients and was related to the rate of aortic expansion (ρ = 0.83, P = .0154). CONCLUSIONS 4D PC-MRI can be accurately applied to visualize and quantify flow characteristics in patients with aortic dissection. Stroke volume, velocity, distal dominant entry tears, and helical flow are related to the rate of aortic expansion. This study demonstrates the potential of this new imaging method. A larger prospective study is now required to measure flow characteristics and determine their predictive value for risk stratification of patients with aortic dissection.

Endovascular Treatment of Mycotic Aortic Aneurysms A European Multicenter Study

Background— Mycotic aortic aneurysm (MAA) is a rare and life-threatening disease. The aim of this European multicenter collaboration was to study the durability of endovascular aortic repair (EVAR) of MAA, by assessing late infection–related complications and long-term survival. Methods and Results— All EVAR treated MAAs, between 1999 and 2013 at 16 European centers, were retrospectively reviewed. One hundred twenty-three patients with 130 MAAs were identified. Mean age was 69 years (range 39–86), 87 (71%) were men, 58 (47%) had immunodeficiency, and 47 (38%) presented with rupture. Anatomic locations were ascending/arch (n=4), descending (n=34), paravisceral (n=15), infrarenal aorta (n=63), and multiple (n=7). Treatments were thoracic EVAR (n=43), fenestrated/branched EVAR (n=9), and infrarenal EVAR (n=71). Antibiotic was administered for mean 30 weeks. Mean follow-up was 35 months (range 1 week to 149 months). Six patients (5%) were converted to open repair during follow-up. Survival was 91% (95% confidence interval, 86% to 96%), 75% (67% to 83%), 55% (44% to 66%), and 41% (28% to 54%) after 1, 12, 60, and 120 months, respectively. Infection-related death occurred in 23 patients (19%), 9 after discontinuation of antibiotic treatment. A Cox regression analysis demonstrated non-Salmonella–positive culture as predictors for late infection–related death. Conclusions— Endovascular treatment of MAA is feasible and for most patients a durable treatment option. Late infections do occur, are often lethal, and warrant long-term antibiotic treatment and follow-up. Patients with non-Salmonella–positive blood cultures were more likely to die from late infection. # CLINICAL PERSPECTIVE {#article-title-32}Background— Mycotic aortic aneurysm (MAA) is a rare and life-threatening disease. The aim of this European multicenter collaboration was to study the durability of endovascular aortic repair (EVAR) of MAA, by assessing late infection–related complications and long-term survival. Methods and Results— All EVAR treated MAAs, between 1999 and 2013 at 16 European centers, were retrospectively reviewed. One hundred twenty-three patients with 130 MAAs were identified. Mean age was 69 years (range 39–86), 87 (71%) were men, 58 (47%) had immunodeficiency, and 47 (38%) presented with rupture. Anatomic locations were ascending/arch (n=4), descending (n=34), paravisceral (n=15), infrarenal aorta (n=63), and multiple (n=7). Treatments were thoracic EVAR (n=43), fenestrated/branched EVAR (n=9), and infrarenal EVAR (n=71). Antibiotic was administered for mean 30 weeks. Mean follow-up was 35 months (range 1 week to 149 months). Six patients (5%) were converted to open repair during follow-up. Survival was 91% (95% confidence interval, 86% to 96%), 75% (67% to 83%), 55% (44% to 66%), and 41% (28% to 54%) after 1, 12, 60, and 120 months, respectively. Infection-related death occurred in 23 patients (19%), 9 after discontinuation of antibiotic treatment. A Cox regression analysis demonstrated non-Salmonella–positive culture as predictors for late infection–related death. Conclusions— Endovascular treatment of MAA is feasible and for most patients a durable treatment option. Late infections do occur, are often lethal, and warrant long-term antibiotic treatment and follow-up. Patients with non-Salmonella–positive blood cultures were more likely to die from late infection.

Exploration of 4D MRI Blood Flow using Stylistic Visualization

Insight into the dynamics of blood-flow considerably improves the understanding of the complex cardiovascular system and its pathologies. Advances in MRI technology enable acquisition of 4D blood-flow data, providing quantitative blood-flow velocities over time. The currently typical slice-by-slice analysis requires a full mental reconstruction of the unsteady blood-flow field, which is a tedious and highly challenging task, even for skilled physicians. We endeavor to alleviate this task by means of comprehensive visualization and interaction techniques. In this paper we present a framework for pre-clinical cardiovascular research, providing tools to both interactively explore the 4D blood-flow data and depict the essential blood-flow characteristics. The framework encompasses a variety of visualization styles, comprising illustrative techniques as well as improved methods from the established field of flow visualization. Each of the incorporated styles, including exploded planar reformats, flow-direction highlights, and arrow-trails, locally captures the blood-flow dynamics and may be initiated by an interactively probed vessel cross-section. Additionally, we present the results of an evaluation with domain experts, measuring the value of each of the visualization styles and related rendering parameters.

A variant in LDLR is associated with abdominal aortic aneurysm

Background—Abdominal aortic aneurysm (AAA) is a common cardiovascular disease among older people and demonstrates significant heritability. In contrast to similar complex diseases, relatively few genetic associations with AAA have been confirmed. We reanalyzed our genome-wide study and carried through to replication suggestive discovery associations at a lower level of significance. Methods and Results—A genome-wide association study was conducted using 1830 cases from the United Kingdom, New Zealand, and Australia with infrarenal aorta diameter ≥30 mm or ruptured AAA and 5435 unscreened controls from the 1958 Birth Cohort and National Blood Service cohort from the Wellcome Trust Case Control Consortium. Eight suggestive associations with P<1×10−4 were carried through to in silico replication in 1292 AAA cases and 30 503 controls. One single-nucleotide polymorphism associated with P<0.05 after Bonferroni correction in the in silico study underwent further replication (706 AAA cases and 1063 controls from the United Kingdom, 507 AAA cases and 199 controls from Denmark, and 885 AAA cases and 1000 controls from New Zealand). Low-density lipoprotein receptor (LDLR) rs6511720 A was significantly associated overall and in 3 of 5 individual replication studies. The full study showed an association that reached genome-wide significance (odds ratio, 0.76; 95% confidence interval, 0.70–0.83; P=2.08×10−10). Conclusions—LDLR rs6511720 is associated with AAA. This finding is consistent with established effects of this variant on coronary artery disease. Shared causal pathways with other cardiovascular diseases may present novel opportunities for preventative and therapeutic strategies for AAA.

A new method for quantification of false lumen thrombosis in aortic dissection using magnetic resonance imaging and a blood pool contrast agent.

BACKGROUND False lumen thrombosis after aortic dissection is a major predictor of prognosis. First pass computed tomography (CT) and magnetic resonance (MR) imaging are used routinely, where the image acquisition is timed to the arrival of contrast in the proximal unaffected aorta. Delayed phase imaging is difficult to refine because flow rates in the false lumen are often very slow and highly variable between patients. Blood pool contrast agents bind to albumin and become homogenously distributed in the intravascular circulation, allowing accurate imaging of areas where flow is low. We compared first pass MR and CT with a delayed phase MR acquisition using a blood pool agent to assess whether this more accurately quantified false lumen thrombosis. METHODS Patients with medically treated chronic type B aortic dissection and evidence of false lumen thrombosis on previous CT imaging underwent first pass CT, first pass MR, and delayed phase MR with blood pool agent. Absence of false lumen contrast enhancement was quantified to assess the apparent differences in thrombosis. Phase-contrast MR data were also obtained to assess the affect of flow velocity on false lumen contrast enhancement, and direct thrombus MR images were used to confirm the presence of thrombus. RESULTS Twelve patients were recruited. No difference was seen in apparent thrombus volume between first pass CT and first pass MR imaging (146.9 cm(3) [SD, 88.6] vs 187.6 cm(3) [SD, 136.1], P = .1119; R(2) = .67 [95% confidence interval (CI), r = .46-.95], P = .0012). In all patients, the volume of thrombus derived from first pass acquisitions was greater than the volume derived from delayed phase MR imaging with blood pool agent: first pass CT (paired t test, P = .0007; mean difference = 83.4 cm(3) [95% CI, 44.1-122.6]) and first pass MR (paired t test, P = .0009; mean difference = 124.0 cm(3) [95% CI, 63.2-184.9]). The difference in thrombus volume between first pass and delayed phase MR imaging with blood pool agent correlated significantly with the mean velocity of flow in the false lumen, with lower flow related to a greater difference (R(2) = .61, P = .0028 [95% CI, r = -.94--.37]). Direct thrombus MR images were able to correctly discriminate between thrombus and blood and matched the area of contrast absence on delayed phase MR with blood pool agent images. CONCLUSION First pass techniques to assess false lumen thrombosis in aortic dissection consistently overestimate the apparent thrombus volume by five to six times. This has implications for interpretation of cohort studies and clinical trials that use false lumen thrombosis as an outcome measure. We recommend delayed phase MR imaging with a blood pool agent when accurate assessment of false lumen thrombosis is required.

Nonrigid Motion Modeling of the Liver From 3-D Undersampled Self-Gated Golden-Radial Phase Encoded MRI

Magnetic resonance imaging (MRI) has been commonly used for guiding and planning image guided interventions since it provides excellent soft tissue visualization of anatomy and allows motion modeling to predict the position of target tissues during the procedure. However, MRI-based motion modeling remains challenging due to the difficulty of acquiring multiple motion-free 3-D respiratory phases with adequate contrast and spatial resolution. Here, we propose a novel retrospective respiratory gating scheme from a 3-D undersampled high-resolution MRI acquisition combined with fast and robust image registrations to model the nonrigid deformation of the liver. The acquisition takes advantage of the recently introduced golden-radial phase encoding (G-RPE) trajectory. G-RPE is self-gated, i.e., the respiratory signal can be derived from the acquired data itself, and allows retrospective reconstructions of multiple respiratory phases at any arbitrary respiratory position. Nonrigid motion modeling is applied to predict the liver deformation of an average breathing cycle. The proposed approach was validated on 10 healthy volunteers. Motion model accuracy was assessed using similarity-, surface-, and landmark-based validation methods, demonstrating precise model predictions with an overall target registration error of TRE = 1.70 ± 0.94 mm which is within the range of the acquired resolution.

A 14-year Experience with Aortic Endograft Infection: Management and Results

OBJECTIVES The management of thoracic and abdominal aortic endograft infection is complex and associated with high mortality. Cases are rare: a recent systematic review identified 117 reported cases; the largest reported series comprises 12 infected endografts. METHODS We report 22 consecutive patients with infected abdominal or thoracic aortic endovascular devices implanted from 1998 to 2012. Management included extension with new devices, aneurysm sac drainage of pus/irrigation with antibiotics, endograft explantation, and axillo-(bi)femoral reconstruction. RESULTS Twenty-two patients (16 men) were identified. Median age was 71 years (range, 43-88 years). Index devices were infra-renal endovascular repair (n = 13), and thoracic endovascular repair (n = 9) all for aneurysmal or pseudoaneurysmal disease. Seven (32%) had prior aortic surgery. Follow-up was complete in all cases; in survivors follow-up was a median of 29 (range, 12-45) months. The mortality from explantation of ten infra-renal devices was 1/10 (10%) on-table and a further 2/10 (20%) within 30 days. Device retention led to disease progression and death in all patients with infected endografts. Sac drainage/irrigation provided only temporary control of sepsis. Device extension can treat rupture, but additional devices became infected. CONCLUSION Abdominal endograft explantation is high risk but may be curative. Appropriate selection of patients for infected endograft explantation remains a major challenge.