Current evidence in predictors of aortic growth and events in acute type B aortic dissection

A Monte Carlo Sensitivity Analysis for a Dimensionally Reduced-Order Model of the Aortic Dissection

PURPOSE

Aortic dissection is associated with a high mortality rate. Although computational approaches have shed light on many aspects of the disease, a sensitivity analysis is required to determine the significance of different factors. Because of its complex geometry and high computational expense, the three-dimensional (3D) fluid-structure interaction (FSI) simulation is not a suitable approach for sensitivity analysis.

METHODS

We performed a Monte Carlo simulation (MCS) to investigate the sensitivity of hemodynamic quantities to the lumped parameters of our zero-dimensional (0D) model with numerically calculated lumped parameters. We performed local and global analyses on the effect of the model parameters on important hemodynamic quantities.

RESULTS

The MCS showed that a larger lumped resistance value for the false lumen and the tears result in a higher retrograde flow rate in the false lumen (the coefficient of variation,c v , i = 0.0183 , the sensitivityS X i σ = 0.54 , Spearman's coefficient,ρ s = 0.464 ). For the intraluminal pressure, our results show a significant role in the resistance and inertance of the true lumen (the coefficient of variation,c v , i = 0.0640 , the sensitivityS X i σ = 0.85 , and Spearman's coefficient,ρ s = 0.855 for the inertance of the true lumen).

CONCLUSION

This study highlights the necessity of comparing the results of the local and global sensitivity analyses to understand the significance of multiple lumped parameters. Because of the efficiency of the method, our approach is potentially useful to investigate and analyze medical planning.

Radiographic complicated and uncomplicated descending aortic dissections: aortic morphological differences by CT angiography and risk factor analysis

AIMS

To identify radiographic differences between patients with uncomplicated and complicated descending aortic dissections.

METHODS AND RESULTS

Between April 2009 and July 2021, 209 patients with acute descending aortic dissections were analysed as complicated (malperfusion, rupture, diameter progress, and diameter ≥ 55 mm) or uncomplicated. Detailed CTA measurements (slice thickness ≤ 3 mm) were taken in multiplanar reconstruction. A composite endpoint (early aortic failure) was defined as reoperation, diameter progression, and early mortality. Seventy-seven patients were female (36.8%) [complicated n = 27 (36.5%); uncomplicated n = 50 (37.0%) P = 1.00]. Seventy-four (35%) patients were categorized as morphologically complicated, and 135 (65%) as uncomplicated. In patients with complicated dissections, the dissection extended more frequently to the aortic bifurcation (P = 0.044), the coeliac trunk (P = 0.003), the superior mesenteric artery (P = 0.007), and both iliac arteries (P < 0.001) originated less frequently from the true lumen. The length of the most proximal communication (entry) in type B aortic dissection was longer, 14.0 mm [12.0 mm; 27.0 mm] vs. 6.0 mm [4,0 mm; 13.0 mm] in complicated cases (P = 0.005). Identified risk factors for adverse aortic events were connective tissue disease [HR 8.0 (1.9-33.7 95% CI HR)], length of the aortic arch [HR 4.7 (1.5-15.1 95% CI HR)], a false lumen diameter > 19.38 mm [HR 3.389 (1.1-10.2 95% CI HR)], and origin of the inferior mesenteric artery from the false lumen [HR 4.2 (1.0-5.5 95% CI HR)].

CONCLUSION

We identified significant morphological differences and predictors for adverse events in patients presenting complicated and uncomplicated descending dissections. Our morphological findings will help guide future aortic therapies, taking a tailored patient approach.

Aortic remodelling based on false lumen communications in patients undergoing acute type I dissection repair with AMDS hybrid prosthesis: a substudy of the DARTS trial

OBJECTIVES

The Dissected Aorta Repair Through Stent (DARTS) Implantation trial demonstrated positive proximal aortic remodelling following aortic dissection repair with the AMDS hybrid prosthesis. In this study, we look to identify predictors of aortic remodelling following aortic dissection repair with AMDS including whether communications between branch vessels and the false lumen (FL) predict aortic growth.

METHODS

The DARTS implantation trial included patients who underwent acute DeBakey type I aortic dissection (ATAD I) repair with the AMDS from March 2017 to January 2019. Anatomic measurements were collected from original computerized tomography scans. Measurements were taken at zones 2, 3, 6 and 9. Patients were grouped based on the number of FL communications with the supra-aortic branch vessels or visceral branch vessels.

RESULTS

Forty-seven patients were included in the original DARTS implantation trial. Patients with FL communications with the supra-aortic branch vessels tended to have significant growth at zone 3 (P = 0.02-0.0018), while greater numbers of visceral FL communications tended to predict aortic growth at zones 3 (P = 0.003), 6 (P = 0.017-0.0087) and 9 (P = 0.0016-0.0003).

CONCLUSIONS

Aortic remodelling following ATAD I repair using the AMDS may be predicted by local FL communications with branch vessels. Patients undergoing ATAD I repair were more likely to experience significant aortic growth in zone 3 with more head vessel communications and in zones 3, 6 and 9 with more visceral FL communications. Predictors of aortic remodelling may help to guide initial surgical management for aortic dissection patients.

Morphologic prognostic factor for thoracoabdominal aortic dilation after acute type A dissection repair

OBJECTIVES

Risk factors for late-term aortic dilation after acute type A aortic dissection repair have not been well examined. The goal of this study was to determine the relationship between the abdominal aortic true lumen location and thoraco-abdominal aortic dilation after surgical repair for acute type A aortic dissection.

METHODS

Patients who were preoperatively diagnosed with acute type A aortic dissection between April 2014 and July 2022 were included in this study. We evaluated the renal artery-level dissected aortic morphology and classified the study population into 2 groups: the ventral (those with the true lumen located on the ventral side) and the dorsal (other patients not assigned to the ventral group) groups, based on the location of the true lumen. Aortic dilation was defined as thoraco-abdominal aortic expansion ≥5 mm on 1-year postoperative computed tomography images.

RESULTS

We examined 49 surgical patients who were assigned to the ventral (n = 22) and dorsal (n = 27) groups. The number of patients with ≥5 mm thoraco-abdominal aortic dilation after the operation was significantly higher in the ventral group than in the dorsal group (90.9% vs 51.9%, P = 0.009). The multivariable logistic regression analysis showed that the ventral type was an independent prognostic factor for thoraco-abdominal aortic dilation after the operation (odds ratio, 6.01; 95% confidence interval, 1.56-23.77; P = 0.009).

CONCLUSIONS

The location of the true lumen of the abdominal aorta in acute type A aortic dissection may be a prognostic factor for thoraco-abdominal aortic dilation after surgical repair.

Identification and Evaluation of Blood-Based Biomarkers for Abdominal Aortic Aneurysm

INTRODUCTION

Blood-based biomarkers for abdominal aortic aneurysm (AAA) have been studied individually; however, we considered a panel of proteins to investigate AAA prognosis and its potential to improve predictive accuracy.

MATERIALS AND METHODS

Using a prospectively recruited cohort of patients with/without AAA (n = 452), we conducted a prognostic study to develop a model that accurately predicts AAA outcomes using clinical features and circulating biomarker levels. Serum concentrations of 9 biomarkers were measured at baseline, and the cohort was followed for 2 years. The primary outcome was major adverse aortic event (MAAE; composite of rapid AAA expansion [>0.5 cm/6 months or >1 cm/12 months], AAA intervention, or AAA rupture). Using 10-fold cross-validation, we trained a random forest model to predict 2 year MAAE using (1) clinical characteristics, (2) biomarkers, and (3) clinical characteristics and biomarkers.

RESULTS

Two-year MAAE occurred in 114 (25%) patients. Two proteins were significantly elevated in patients with AAA compared with those without AAA (angiopoietin-2 and aggrecan), composing the protein panel. For predicting 2 year MAAE, our random forest model achieved area under the receiver operating characteristic curve (AUROC) 0.74 using clinical features alone, and the addition of the 2-protein panel improved performance to AUROC 0.86.

CONCLUSIONS

Using a combination of clinical/biomarker data, we developed a model that accurately predicts 2 year MAAE.

A Deformable Constraint Transport Network for Optimal Aortic Segmentation From CT Images

Aortic segmentation from computed tomography (CT) is crucial for facilitating aortic intervention, as it enables clinicians to visualize aortic anatomy for diagnosis and measurement. However, aortic segmentation faces the challenge of variable geometry in space, as the geometric diversity of different diseases and the geometric transformations that occur between raw and measured images. Existing constraint-based methods can potentially solve the challenge, but they are hindered by two key issues: inaccurate definition of properties and inappropriate topology of transformation in space. In this paper, we propose a deformable constraint transport network (DCTN). The DCTN adaptively extracts aortic features to define intra-image constrained properties and guides topological implementation in space to constrain inter-image geometric transformation between raw and curved planar reformation (CPR) images. The DCTN contains a deformable attention extractor, a geometry-aware decoder and an optimal transport guider. The extractor generates variable patches that preserve semantic integrity and long-range dependency in long-sequence images. The decoder enhances the perception of geometric texture and semantic features, particularly for low-intensity aortic coarctation and false lumen, which removes background interference. The guider explores the geometric discrepancies between raw and CPR images, constructs probability distributions of discrepancies, and matches them with inter-image transformation to guide geometric topology in space. Experimental studies on 267 aortic subjects and four public datasets show the superiority of our DCTN over 23 methods. The results demonstrate DCTN's advantages in aortic segmentation for different types of aortic disease, for different aortic segments, and in the measurement of clinical indexes.

Current perspectives in acute type B aortic dissections: a literature review

In this new millennial, endovascular strategies have revolutionized the treatment of acute type B aortic dissection (aTBAD). With reduced in-hospital mortality and good long-term outcomes TEVAR has become the gold standard for the treatment of complicated dissection and is gaining increasing support for its preventive applicability in some uncomplicated dissections. With this new paradigm came a shift of the treatment goal where just covering the entry tear is not enough and instead achieving long-term positive thoracoabdominal remodeling is needed. More extensive approaches with composite device designs (covered stent graft and bare metal stent) emerged to answer this aortic conundrum. At 5-year of follow-up, "Provisional ExTension To Induce COmplete Attachment technique" (PETTICOAT) and its evolution "Stent assisted balloon induced intimal disruption and relamination in aortic dissection repair" (STABILISE) seem to be safe techniques that can allow, when anatomically feasible, excellent aortic remodeling and, in some cases, even the healing of the dissection. Nevertheless, STABILISE results, although promising, are mostly based on small series and therefore need to be validated by analyzing medium-long-term results from the international registry. Given the plethora of new data and the disparity of expert opinions on the best treatment to adopt, in this review we aim to summarize the current knowledge on the results of these different strategies for acute TBAD.

The geometric evolution of aortic dissections: Predicting surgical success using fluctuations in integrated Gaussian curvature

Clinical imaging modalities are a mainstay of modern disease management, but the full utilization of imaging-based data remains elusive. Aortic disease is defined by anatomic scalars quantifying aortic size, even though aortic disease progression initiates complex shape changes. We present an imaging-based geometric descriptor, inspired by fundamental ideas from topology and soft-matter physics that captures dynamic shape evolution. The aorta is reduced to a two-dimensional mathematical surface in space whose geometry is fully characterized by the local principal curvatures. Disease causes deviation from the smooth bent cylindrical shape of normal aortas, leading to a family of highly heterogeneous surfaces of varying shapes and sizes. To deconvolute changes in shape from size, the shape is characterized using integrated Gaussian curvature or total curvature. The fluctuation in total curvature (δK) across aortic surfaces captures heterogeneous morphologic evolution by characterizing local shape changes. We discover that aortic morphology evolves with a power-law defined behavior with rapidly increasing δK forming the hallmark of aortic disease. Divergent δK is seen for highly diseased aortas indicative of impending topologic catastrophe or aortic rupture. We also show that aortic size (surface area or enclosed aortic volume) scales as a generalized cylinder for all shapes. Classification accuracy for predicting aortic disease state (normal, diseased with successful surgery, and diseased with failed surgical outcomes) is 92.8±1.7%. The analysis of δK can be applied on any three-dimensional geometric structure and thus may be extended to other clinical problems of characterizing disease through captured anatomic changes.

Hemodynamic effects of entry and exit tear size in aortic dissection evaluated with in vitro magnetic resonance imaging and fluid-structure interaction simulation

Understanding the complex interplay between morphologic and hemodynamic features in aortic dissection is critical for risk stratification and for the development of individualized therapy. This work evaluates the effects of entry and exit tear size on the hemodynamics in type B aortic dissection by comparing fluid-structure interaction (FSI) simulations with in vitro 4D-flow magnetic resonance imaging (MRI). A baseline patient-specific 3D-printed model and two variants with modified tear size (smaller entry tear, smaller exit tear) were embedded into a flow- and pressure-controlled setup to perform MRI as well as 12-point catheter-based pressure measurements. The same models defined the wall and fluid domains for FSI simulations, for which boundary conditions were matched with measured data. Results showed exceptionally well matched complex flow patterns between 4D-flow MRI and FSI simulations. Compared to the baseline model, false lumen flow volume decreased with either a smaller entry tear (- 17.8 and - 18.5%, for FSI simulation and 4D-flow MRI, respectively) or smaller exit tear (- 16.0 and - 17.3%). True to false lumen pressure difference (initially 11.0 and 7.9 mmHg, for FSI simulation and catheter-based pressure measurements, respectively) increased with a smaller entry tear (28.9 and 14.6 mmHg), and became negative with a smaller exit tear (- 20.6 and - 13.2 mmHg). This work establishes quantitative and qualitative effects of entry or exit tear size on hemodynamics in aortic dissection, with particularly notable impact observed on FL pressurization. FSI simulations demonstrate acceptable qualitative and quantitative agreement with flow imaging, supporting its deployment in clinical studies.

Editor's Choice - Trends in Management and Outcomes of Type B Aortic Dissection: A Report From the International Registry of Aortic Dissection

OBJECTIVE

To describe the trends in management and outcomes of patients with acute type B aortic dissection in the International Registry of Acute Aortic Dissection.

METHODS

From 1996 - 2022, 3 908 patients were divided into similar sized quartiles (T1, T2, T3, and T4). In hospital outcomes were analysed for each quartile. Survival rates following admission were compared using Kaplan-Meier analyses with Mantel-Cox Log rank tests.

RESULTS

Endovascular treatment increased from 19.1% in T1 to 37.2% in T4 (ptrend < .001). Correspondingly, medical therapy decreased from 65.7% in T1 to 54.0% in T4 (ptrend < .001), and open surgery from 14.8% in T1 to 7.0% in T4 (ptrend < .001). In hospital mortality decreased in the overall cohort from 10.7% in T1 to 6.1% in T4 (ptrend < .001), as well as in medically, endovascularly and surgically treated patients (ptrend = .017, .033, and .011, respectively). Overall post-admission survival at three years increased (T1: 74.8% vs. T4: 77.3%; p = .006).

CONCLUSION

Considerable changes in the management of acute type B aortic dissection were observed over time, with a significant increase in the use of endovascular treatment and a corresponding reduction in open surgery and medical management. These changes were associated with a decreased overall in hospital and three year post-admission mortality rate among quartiles.

Artificial Intelligence-Based Prediction of Cardiovascular Diseases from Chest Radiography

Chest radiography (CXR) is the most frequently performed radiological test worldwide because of its wide availability, non-invasive nature, and low cost. The ability of CXR to diagnose cardiovascular diseases, give insight into cardiac function, and predict cardiovascular events is often underutilized, not clearly understood, and affected by inter- and intra-observer variability. Therefore, more sophisticated tests are generally needed to assess cardiovascular diseases. Considering the sustained increase in the incidence of cardiovascular diseases, it is critical to find accessible, fast, and reproducible tests to help diagnose these frequent conditions. The expanded focus on the application of artificial intelligence (AI) with respect to diagnostic cardiovascular imaging has also been applied to CXR, with several publications suggesting that AI models can be trained to detect cardiovascular conditions by identifying features in the CXR. Multiple models have been developed to predict mortality, cardiovascular morphology and function, coronary artery disease, valvular heart diseases, aortic diseases, arrhythmias, pulmonary hypertension, and heart failure. The available evidence demonstrates that the use of AI-based tools applied to CXR for the diagnosis of cardiovascular conditions and prognostication has the potential to transform clinical care. AI-analyzed CXRs could be utilized in the future as a complimentary, easy-to-apply technology to improve diagnosis and risk stratification for cardiovascular diseases. Such advances will likely help better target more advanced investigations, which may reduce the burden of testing in some cases, as well as better identify higher-risk patients who would benefit from earlier, dedicated, and comprehensive cardiovascular evaluation.

A Comparison of Retrospective ECG-Gated CT and Surgical or Angiographical Findings in Acute Aortic Syndrome

The best cardiac phases in retrospective ECG-gated CT for detecting an intimal tear (IT) in aortic dissection (AD) and an ulcer-like projection (ULP) in an intramural hematoma (IMH) have not been established. This study aimed to compare the detection accuracy of diastolic-phase and systolic-phase ECG-gated CT for IT in AD and ULP in IMH, with subsequent surgical or angiographical confirmation as the reference standard.In total, 81 patients (67.6 ± 11.8 years; 41 men) who underwent emergency ECG-gated CT and subsequent open surgery or thoracic endovascular aortic repair for AD (n = 52) or IMH (n = 29) were included. The accuracies of detecting IT and ULP were compared among only diastolic-phase, only systolic-phase, and both diastolic-phase and systolic-phase methods of retrospective ECG-gated CT; surgical or angiographical findings were used as the reference standard. The detection accuracy for IT and ULP using only diastolic-phase, only systolic-phase, and both diastolic-phase and systolic-phase methods of ECG-gated CT was 93% [95% CI: 87-97], 94% [95% CI: 88-97], and 95% [95% CI: 90-97], respectively. There were no significant differences in detection accuracy among the 3 acquisition methods (P = 0.55). Similarly, there were no significant differences in the accuracy of detecting IT in AD (P = 0.55) and ULP in IMH (P > 0.99) among only diastolic-phase, only systolic-phase, and both diastolic- and systolic-phase ECG-gated CT.Retrospective ECG-gated CT for detecting IT in AD and ULP in IMH yields highly accurate findings. There were no significant differences seen among only diastolic-phase, only systolic-phase, and both diastolic-phase and systolic-phase ECG-gated CT.

Factors Affecting False Lumen Thrombosis In Type B Aortic Dissection

BACKGROUND

Complete thrombosis of the false lumen facilitates remodeling of type B aortic dissection (TBAD). Morphological characteristics affect thrombosis in the false lumen.

OBJECTIVES

Discuss the factors present before admission that influence false lumen thrombosis in patients with TBAD.

METHODS

We studied 282 patients diagnosed with TBAD in our hospital between January 2008 and December 2017. We divided the subjects into a thrombotic group and a non-thrombotic group based on whether any thrombus was detectable in the false lumen. We analyzed the differences between the two groups with respect to clinical data, the vertical length of the dissection, and the diameter of the aorta. P values < 0.05 were considered statistically significantly different.

RESULTS

Significant differences between the thrombotic group and non-thrombotic group were found with respect to age (53.92 ± 11.40 vs. 50.36 ± 10.71, p = 0.009) and proportion of patients with renal insufficiency (7.83% vs. 16.38%, p = 0.026). In zones 3-9, the true lumen diameter of the thrombotic group was significantly larger than in the non-thrombotic group (p < 0.05). Binary logistic regression analysis showed that true lumen diameter in zone 5 and renal insufficiency were independent predictors of false lumen thrombosis.

CONCLUSIONS

Age and renal function were associated with thrombosis in the false lumen. Potentially, the difference between the diameter of the true lumen diameter and that of the false lumen may influence the thrombosis of the false lumen.

Optimal medical treatment versus endovascular aortic repair in uncomplicated isolated abdominal aortic dissection

OBJECTIVE

To report the results of optimal medical treatment (OMT) and endovascular aortic repair (EVAR) in patients with uncomplicated isolated abdominal aortic dissection (IAAD).

METHODS

A retrospective review of 96 consecutive patients with uncomplicated IAAD (uIAAD) managed at a single tertiary vascular unit between January 2011 and July 2021 was conducted. Standard methods for univariate and survival analyses were used. The primary outcomes were all-cause mortality. Secondary end points included uIAAD progression, interventional complications, and follow-up aortic intervention.

RESULTS

Initially, 53.1% of patients (51/96) were managed with OMT. No in-hospital deaths occurred. During follow-up, three patients died, and three and two patients who were initially managed with OMT subsequently required endovascular treatment and surgical management, respectively. Initially, 46.9% of patients (45/96) underwent EVAR. One patient died during hospital admission; nine patients had an endoleak after operation and one needed reintervention. Furthermore, during follow-up, five patients died; four patients needed reoperation, one surgery and three endovascular treatments. The overall long-term mortality was 8.4%, and follow-up aortic intervention rate was 9.5% (median follow-up, 54 months; interquartile range, 33-81 months) with no significant difference between groups. Of note, 12 patients (12.6%) suffered uIAAD progression, which was higher in the OMT group than EVAR group (10 [19.6%] vs 2 [4.5%]; P = .03).

CONCLUSIONS

uIAAD may be managed safely by OMT with regular surveillance, despite the risk of disease progression. Compared with OMT, EVAR could significantly prevent uIAAD progression. For anatomically suitable patients with uIAAD progression and who are unresponsive to OMT, pre-emptive EVAR is a safe and feasible option.

Acute aortic dissection

Although substantial progress has been made in the prevention, diagnosis, and treatment of acute aortic dissection, it remains a complex cardiovascular event, with a high immediate mortality and substantial morbidity in individuals surviving the acute period. The past decade has allowed a leap forward in understanding the pathophysiology of this disease; the existing classifications have been challenged, and the scientific community moves towards a nomenclature that is likely to unify the current definitions according to morphology and function. The most important pathophysiological pathway, namely the location and extension of the initial intimal tear, which causes a disruption of the media layer of the aortic wall, together with the size of the affected aortic segments, determines whether the patient should undergo emergency surgery, an endovascular intervention, or receive optimal medical treatment. The scientific evidence for the management and follow-up of acute aortic dissection continues to evolve. This Seminar provides a clinically relevant overview of potential prevention, diagnosis, and management of acute aortic dissection, which is the most severe acute aortic syndrome.

Advanced risk prediction for aortic dissection patients using imaging-based computational flow analysis

Patients with either a repaired or medically managed aortic dissection have varying degrees of risk of developing late complications. High-risk patients would benefit from earlier intervention to improve their long-term survival. Currently serial imaging is used for risk stratification, which is not always reliable. On the other hand, understanding aortic haemodynamics within a dissection is essential to fully evaluate the disease and predict how it may progress. In recent decades, computational fluid dynamics (CFD) has been extensively applied to simulate complex haemodynamics within aortic diseases, and more recently, four-dimensional (4D)-flow magnetic resonance imaging (MRI) techniques have been developed for in vivo haemodynamic measurement. This paper presents a comprehensive review on the application of image-based CFD simulations and 4D-flow MRI analysis for risk prediction in aortic dissection. The key steps involved in patient-specific CFD analyses are demonstrated. Finally, we propose a workflow incorporating computational modelling for personalised assessment to aid in risk stratification and treatment decision-making.

Inter-observer variability of expert-derived morphologic risk predictors in aortic dissection

OBJECTIVES

Establishing the reproducibility of expert-derived measurements on CTA exams of aortic dissection is clinically important and paramount for ground-truth determination for machine learning.

METHODS

Four independent observers retrospectively evaluated CTA exams of 72 patients with uncomplicated Stanford type B aortic dissection and assessed the reproducibility of a recently proposed combination of four morphologic risk predictors (maximum aortic diameter, false lumen circumferential angle, false lumen outflow, and intercostal arteries). For the first inter-observer variability assessment, 47 CTA scans from one aortic center were evaluated by expert-observer 1 in an unconstrained clinical assessment without a standardized workflow and compared to a composite of three expert-observers (observers 2-4) using a standardized workflow. A second inter-observer variability assessment on 30 out of the 47 CTA scans compared observers 3 and 4 with a constrained, standardized workflow. A third inter-observer variability assessment was done after specialized training and tested between observers 3 and 4 in an external population of 25 CTA scans. Inter-observer agreement was assessed with intraclass correlation coefficients (ICCs) and Bland-Altman plots.

RESULTS

Pre-training ICCs of the four morphologic features ranged from 0.04 (-0.05 to 0.13) to 0.68 (0.49-0.81) between observer 1 and observers 2-4 and from 0.50 (0.32-0.69) to 0.89 (0.78-0.95) between observers 3 and 4. ICCs improved after training ranging from 0.69 (0.52-0.87) to 0.97 (0.94-0.99), and Bland-Altman analysis showed decreased bias and limits of agreement.

CONCLUSIONS

Manual morphologic feature measurements on CTA images can be optimized resulting in improved inter-observer reliability. This is essential for robust ground-truth determination for machine learning models.

KEY POINTS

• Clinical fashion manual measurements of aortic CTA imaging features showed poor inter-observer reproducibility. • A standardized workflow with standardized training resulted in substantial improvements with excellent inter-observer reproducibility. • Robust ground truth labels obtained manually with excellent inter-observer reproducibility are key to develop reliable machine learning models.

Fluid-structure interaction simulation of visceral perfusion and impact of different cannulation methods on aortic dissection

Hemodynamics in aortic dissection (AD) is closely associated with the risk of aortic aneurysm, rupture, and malperfusion. Altered blood flow in patients with AD can lead to severe complications such as visceral malperfusion. In this study, we aimed to investigate the effect of cannulation flow on hemodynamics in AD using a fluid-structure interaction simulation. We developed a specific-idealized AD model that included an intimal tear in the descending thoracic aorta, a re-entry tear in the left iliac artery, and nine branches. Two different cannulation methods were tested: (1) axillary cannulation (AC) only through the brachiocephalic trunk and (2) combined axillary and femoral cannulation (AFC) through the brachiocephalic trunk and the right common iliac artery. AC was found to result in the development of a pressure difference between the true lumen and false lumen, owing to the difference in the flow rate through each lumen. This pressure difference collapsed the true lumen, disturbing blood flow to the celiac and superior mesenteric arteries. However, in AFC, the pressure levels between the two lumens were similar, and no collapse occurred. Moreover, the visceral flow was higher than that in AC. Lastly, the stiffness of the intimal flap affected the true lumen's collapse.

Readmission after early thoracic endovascular aortic repair versus medical management of acute type B aortic dissection

BACKGROUND

The use of thoracic endovascular aortic repair (TEVAR) for the management of acute uncomplicated type B aortic dissection (TBAD) has increased. Although the results from early studies were promising, larger randomized trials evaluating TEVAR are lacking. It is also unclear where sufficient equipoise exists for such trials. In the present study, we evaluated the number of readmissions and unplanned operations after TEVAR vs those after medical management as the initial treatment of acute uncomplicated TBAD and the frequency of each treatment in this population.

METHODS

We performed a multi-institutional retrospective review of patients with acute TBAD from 2015 to 2020 with the 1-year outcomes available, excluding patients with prior aortic intervention or chronic, iatrogenic or traumatic etiologies. The primary exposure was TEVAR vs medical management at the index admission. The patient demographics, clinical presentation, and imaging findings were analyzed using bivariate and multivariate logistic regression for the primary outcomes of unplanned readmission and/or operation after the initial admission. The secondary outcomes were mortality, myocardial infarction, stroke, renal failure requiring dialysis, retrograde type A dissection, and length of stay. We hypothesized that the readmissions would be higher with medical management.

RESULTS

A total of 216 patients with TBAD (47 with complicated and 169 with uncomplicated) from two large academic centers were identified. Of the 169 patients with uncomplicated TBAD, 83 (49%) had been treated medically and 86 (51%) had undergone TEVAR at the initial admission. No differences were found in the demographics or high-risk imaging features at presentation. The medically managed patients had had higher rates of unplanned readmission (34% vs 9%; P = .0001) and operation (28% vs 8%; P = .0007) but shorter lengths of stay (6.3 vs 13.1 days; P < .0001). No differences were found in mortality, although the rate of myocardial infarction was higher in the medically managed group (10.8% vs 2.3%; P = .02). Although 28% of the medically managed patients had later required operation, they had had morbidity and mortality similar to those of patients who had undergone initial TEVAR. Initial medical management was associated with unplanned readmission (odds ratio, 8.3; P = .02) and the need for operation (odds ratio, 4.56; P = .006). No differences were found in the outcomes according to the involved aortic zones.

CONCLUSIONS

In the present study, medical management of acute uncomplicated TBAD was associated with higher rates of readmission and the need for unplanned operation compared with TEVAR. However, no differences were found in the 1-year mortality for the patients for whom medical management had failed. Because one half of the patients had undergone medical management and one half had undergone early TEVAR, this finding suggests clinical equipoise for the treatment of acute uncomplicated TBAD. Therefore, a larger randomized trial appears warranted to determine whether a clear benefit exists for early TEVAR.

Morphological parameters affecting false lumen thrombosis following type B aortic dissection: a systematic study based on simulations of idealized models

Type B aortic dissection (TBAD) carries a high risk of complications, particularly with a partially thrombosed or patent false lumen (FL). Therefore, uncovering the risk factors leading to FL thrombosis is crucial to identify high-risk patients. Although studies have shown that morphological parameters of the dissected aorta are related to FL thrombosis, often conflicting results have been reported. We show that recent models of thrombus evolution in combination with sensitivity analysis methods can provide valuable insights into how combinations of morphological parameters affect the prospect of FL thrombosis. Based on clinical data, an idealized geometry of a TBAD is generated and parameterized. After implementing the thrombus model in computational fluid dynamics simulations, a global sensitivity analysis for selected morphological parameters is performed. We then introduce dimensionless morphological parameters to scale the results to individual patients. The sensitivity analysis demonstrates that the most sensitive parameters influencing FL thrombosis are the FL diameter and the size and location of intimal tears. A higher risk of partial thrombosis is observed when the FL diameter is larger than the true lumen diameter. Reducing the ratio of the distal to proximal tear size increases the risk of FL patency. In summary, these parameters play a dominant role in classifying morphologies into patent, partially thrombosed, and fully thrombosed FL. In this study, we point out the predictive role of morphological parameters for FL thrombosis in TBAD and show that the results are in good agreement with available clinical studies.

Entry tear hemodynamics using 4D flow MRI in a patient with acute type B aortic dissection

Stanford type B aortic dissection (TBAD) is a potentially fatal condition involving a tear in the descending aorta. As TBAD can be managed with medical therapy or surgical repair, identifying predictors of adverse outcomes is important to risk-stratify patients for preemptive surgical procedures. 4D flow magnetic resonance imaging (MRI) has shown to be useful in characterizing the complex hemodynamics seen in TBAD patients and correlating flow patterns with adverse outcomes. We report a case of a 58-year-old man who presented to the hospital with acute TBAD and a large primary entry tear. He was initially managed with medical therapy due to his stable clinical status and computed tomographic angiography showing a stable dissection. However, 4D flow MRI showed high velocity flow through the entry tear, which foreshadowed the later clinical decompensation of the patient. Our case demonstrates that performing 4D flow MRI on TBAD patients is feasible and can provide valuable information in the decision to pursue medical or surgical management.

Endovascular treatment of complicated versus uncomplicated acute type B aortic dissection

OBJECTIVE

The study objective was to analyze the outcomes of thoracic endovascular aortic repair performed for complicated and uncomplicated acute type B aortic dissections.

METHODS

Patients from WL Gore's Global Registry for Endovascular Aortic Treatment who underwent thoracic endovascular aortic repair for acute type B aortic dissections were included, and data were retrospectively analyzed.

RESULTS

Of 5014 patients enrolled in the Global Registry for Endovascular Aortic Treatment, 172 underwent thoracic endovascular aortic repair for acute type B aortic dissections. Of these repairs, 102 were for complicated acute type B aortic dissections and 70 were for uncomplicated acute type B aortic dissections. There were 46 (45.1%) procedures related to aortic branch vessels versus 15 (21.4%) in complicated type B aortic dissections and uncomplicated type B aortic dissections (P = .002). The mean length of stay was 14.3 ± 10.6 days (median, 11; range, 2-75) versus 9.8 ± 7.9 days (median, 8; range, 0-42) in those with complicated type B aortic dissections versus those with uncomplicated acute type B aortic dissections (P < .001). Thirty-day mortality was not different between groups (complicated type B aortic dissections 2.9% vs uncomplicated acute type B aortic dissections 1.4%, P = .647), as well as aortic complications (8.8% vs 5.7%, P = .449). Aortic event-free survival was 62.9% ± 37.1% versus 70.6% ± 29.3% at 3 years (P = .696).

CONCLUSIONS

In the Global Registry for Endovascular Aortic Treatment, thoracic endovascular aortic repair results for complicated type B aortic dissections versus uncomplicated acute type B aortic dissections showed that 30-day mortality and perioperative complications were equally low for both. The midterm outcome was positive. These data confirm that thoracic endovascular aortic repair as the first-line strategy for treating complicated type B dissections is associated with a low risk of complications. Further studies with longer follow-up are necessary to define the role of thoracic endovascular aortic repair in uncomplicated acute type B dissections compared with medical therapy. However, in the absence of level A evidence from randomized trials, results of the uncomplicated acute type B aortic dissection patient cohort treated with thoracic endovascular aortic repair from registries are important to understand the related risk and benefit.

Registry of Aortic Diseases to Model Adverse Events and Progression (ROADMAP) in Uncomplicated Type B Aortic Dissection: Study Design and Rationale

Purpose

To describe the design and methodological approach of a multicenter, retrospective study to externally validate a clinical and imaging-based model for predicting the risk of late adverse events in patients with initially uncomplicated type B aortic dissection (uTBAD).

Materials and Methods

The Registry of Aortic Diseases to Model Adverse Events and Progression (ROADMAP) is a collaboration between 10 academic aortic centers in North America and Europe. Two centers have previously developed and internally validated a recently developed risk prediction model. Clinical and imaging data from eight ROADMAP centers will be used for external validation. Patients with uTBAD who survived the initial hospitalization between January 1, 2001, and December 31, 2013, with follow-up until 2020, will be retrospectively identified. Clinical and imaging data from the index hospitalization and all follow-up encounters will be collected at each center and transferred to the coordinating center for analysis. Baseline and follow-up CT scans will be evaluated by cardiovascular imaging experts using a standardized technique.

Results

The primary end point is the occurrence of late adverse events, defined as aneurysm formation (≥6 cm), rapid expansion of the aorta (≥1 cm/y), fatal or nonfatal aortic rupture, new refractory pain, uncontrollable hypertension, and organ or limb malperfusion. The previously derived multivariable model will be externally validated by using Cox proportional hazards regression modeling.

Conclusion

This study will show whether a recent clinical and imaging-based risk prediction model for patients with uTBAD can be generalized to a larger population, which is an important step toward individualized risk stratification and therapy.Keywords: CT Angiography, Vascular, Aorta, Dissection, Outcomes Analysis, Aortic Dissection, MRI, TEVAR© RSNA, 2022See also the commentary by Rajiah in this issue.

Using a reduced-order model to investigate the effect of the heart rate on the aortic dissection

The computational cost of a three-dimensional (3D) fluid-structure interaction (FSI) simulation of a dissected aorta has prevented researchers from investigating the effect of a wide range of the heart rate on the hemodynamic quantities in the disease. We have presented a systematic procedure to develop a zero-dimensional (0D) model for a dissected aorta. A series of numerical experiments were used to calculate the values for the resistance, inertance, and compliance of each lumen with irregular geometries. Having validated the results from the 0D model against those from the 3D model for one heart rate, we used the 0D model to investigate the effect of the heart rate of 50-150 bpm on the flow rates and the pressures in an idealized geometry of an aortic dissection. The 0D model showed acceptable accuracy when compared with the 3D FSI simulation. For instance, at peak systole, 7.18% relative error in the flow rate in the true lumen was observed for 0D and 3D simulations. The flow rate in the true lumen showed a stronger dependency on the heart rate, that is, 300% for the true lumen and 1.5% for the false lumen. The pressure difference between the lumina increased non-monotonically as the heart beats faster. Because of its efficiency, the reported procedure can be used for uncertainty and sensitivity analysis of the hemodynamic quantities in a diseased aorta with complex geometries such as that of the aortic dissection.

Early aortic growth in acute descending aortic dissection

OBJECTIVES

Acute aortic dissection leads to the destabilization of the aortic wall, followed by an immediate increase in aortic diameter. It remains unclear how the aortic diameter changes during the dissection's acute and subacute phases. The aim of this study was to evaluate the change in aortic geometry within 30 days after the onset of a descending aortic dissection.

METHODS

Patients with acute type B and non-A non-B dissection who had at least 2 computed tomography angiography scans obtained within 30 days after the onset of dissection were evaluated. Exclusion criteria were a thrombosed false lumen, connective tissue disorders and endovascular or open aortic repair performed prior to the second computed tomography angiography.

RESULTS

Among 190 patients with acute aortic dissection, 42 patients met our inclusion criteria. Their aortic geometry was analysed according to the computed tomography angiography scans obtained between 0-3 (N = 35), 4-7 (N = 9) and 8-30 (N = 12) days after the dissection onset. The highest aortic diameter growth rate was observed in the first quartile of the thoracic aorta and measured 0.66 (0.06; 1.03), 0.29 (-0.01; 0.41) and 0.06 (-0.13; 0.26) mm/day at 0-3, 4-7 and 8-30 days after the dissection, respectively. Proximal entry location (P = 0.037) and entry located at the arch concavity (P = 0.008) were associated with a higher aortic diameter increase.

CONCLUSIONS

Early rapid growth occurs during the first week after the descending aortic dissection-most intensely over the first 3 days, and this is associated with the location of the dissection's entry.

The Necessity to Seal the Re-Entry Tears of Aortic Dissection After TEVAR: A Hemodynamic Indicator

Thoracic endovascular aortic repair (TEVAR) is a common treatment for Stanford type B aortic dissection (TBAD). However, re-entry tears might be found distal to the stented region which transports blood between the true and false lumens. Sealing the re-entry tears, especially for the thoracic tears, could further reduce blood perfusion to the false lumen; however, it might also bring risks by re-intervention or surgery. Wise determination of the necessity to seal the re-entry tears is needed. In this study, patient-specific models of TBAD were reconstructed, and the modified models were established by virtually excluding the thoracic re-entries. Computational hemodynamics was investigated, and the variation of the functional index and first balance position (FBP) of the luminal pressure difference, due to the sealing of the re-entries, was reported. The results showed that the direction of the net flow through the unstented thoracic re-entries varied among cases. Excluding the re-entries with the net flow toward the false lumen may induce the FBP moving distally and the relative particle residence time increasing in the false lumen. This study preliminarily demonstrated that the hemodynamic status of the re-entry tears might serve as an indicator to the necessity of sealing. By quantifying the through-tear flow exchange and shift of FBP, one can predict the hemodynamic benefit by sealing the thoracic re-entries and thus wisely determine the necessity of further interventional management.

Imaging and Surveillance of Chronic Aortic Dissection: A Scientific Statement From the American Heart Association

All patients surviving an acute aortic dissection require continued lifelong surveillance of their diseased aorta. Late complications, driven predominantly by chronic false lumen degeneration and aneurysm formation, often require surgical, endovascular, or hybrid interventions to treat or prevent aortic rupture. Imaging plays a central role in the medical decision-making of patients with chronic aortic dissection. Accurate aortic diameter measurements and rigorous, systematic documentation of diameter changes over time with different imaging equipment and modalities pose a range of practical challenges in these complex patients. Currently, no guidelines or recommendations for imaging surveillance in patients with chronic aortic dissection exist. In this document, we present state-of-the-art imaging and measurement techniques for patients with chronic aortic dissection and clarify the need for standardized measurements and reporting for lifelong surveillance. We also examine the emerging role of imaging and computer simulations to predict aortic false lumen degeneration, remodeling, and biomechanical failure from morphological and hemodynamic features. These insights may improve risk stratification, individualize contemporary treatment options, and potentially aid in the conception of novel treatment strategies in the future.

Type B aortic dissection residual after proximal aortic repair: an innovative open surgical approach in patients not eligible for endovascular treatment

BACKGROUND

Residual type B aortic dissection (R-TBAD) is a challenging kind of disease affecting an increasing number of patients. Management of R-TBAD has not been specifically addressed in current literature and many of those patients are not eligible for endovascular treatment. Aim of the study was to evaluate the efficacy and feasibility of a specifically conceived procedure the "saguaro branched graft technique" to treat R-TBAD distal to a proximal stent-graft.

METHODS

Data of patients treated between 2015 and 2019 were prospectively collected and retrospectively analysed. Indication for surgery was R-TBAD with chronic malperfusion, aortic enlargement >55mm or rapid growth, and symptomatic aortic enlargement. A dacron graft with four branches has been tailored on the back table by implanting two bifurcated grafts to a tube or bifurcated graft. After left thoracoabdominal incision the proximal endograft has been used as a solid starting point for the distal branched graft. Sequential revascularization of the visceral vessels was performed step by step by suturing each artery outside the aneurysm before opening the distal aorta, while a continued retrograde aortic and visceral perfusion was maintained by a left pump atrio-femoral bypass. After that all visceral branches had been regularly perfused from above, the thoraco-abdominal aorta was open and repaired. Outcome measures were 30-day mortality and 30-day major complications as were long-term all-cause mortality, aorta-related mortality, reintervention and patency rates of the branches.

RESULTS

Thirteen patients with R-TBAD were treated during the study period. Indication for surgery was chronic malperfusion in one patient (7.7%), aortic enlargement >55mm or rapid growth in 9 patients (69.2%), persistent pain with aortic enlargement ≥50mm in 3 patients (23.1%). All patients were considered not eligible for endovascular repair. At 30-days no deaths or re-interventions occurred and major complications including acute cardiovascular events and renal function impairment were not reported; one patient (7.7%) developed postoperative paraplegia. At a mean follow-up period of 19.6±10.2 (range, 8-48) months, reintervention and mortality rates were null. Visceral malperfusion and late-onset renal failure were not reported, and all visceral branches were still patent.

CONCLUSIONS

Despite the potential high risk of open surgery, the "saguaro branched graft technique" appears to be a safe surgical solution for R-TBAD.

Criteria for endovascular intervention in type B aortic dissection

BACKGROUND

The use of thoracic endovascular aortic repair (TEVAR) for the management of uncomplicated type B aortic dissection (un-TBAD) remains controversial. There is a lack of consensus over whether pre-emptive TEVAR should be carried out in patients with un-TBAD at risk of progression to complicated TBAD. We present a review of current evidence and seek to suggest criteria where endovascular intervention in un-TBAD may prove beneficial relative to pharmacotherapy alone.

METHODS AND MATERIALS

PubMed and Cochrane databases were searched using terms including: type B aortic dissection, risk factors, medical therapy, TEVAR, false lumen (FL) expansion, and mortality. Papers were selected based on title and abstract.

RESULTS

Optimal medical therapy remains the mainstay treatment for patients with un-TBAD, however, patients with un-TBAD present with varying degrees of disease progression risk. Factors such as age, aortic morphology, history of connective tissue disorders, FL thrombosis, and aortic branch involvement may potentiate progression from un-TBAD to complicated TBAD. Short- and long-term outcomes associated with TEVAR for TBAD remain promising.

CONCLUSION

Pre-emptive TEVAR may be beneficial in patients with un-TBAD presenting with the above factors, however, further prospective research into the optimal timing for TEVAR in un-TBAD is required.

Evaluation and verification of patient-specific modelling of type B aortic dissection

Quantitative assessment of the complex hemodynamic environment in type B aortic dissection (TBAD) through computational fluid dynamics (CFD) simulations can provide detailed insights into the disease and its progression. As imaging and computational technologies have advanced, methodologies have been developed to increase the accuracy and physiological relevance of CFD simulations. This study presents a patient-specific workflow to simulate blood flow in TBAD, utilising the maximum amount of in vivo data available in the form of CT images, 4D-flow MRI and invasive Doppler-wire pressure measurements, to implement the recommended current best practice methodologies in terms of patient-specific geometry and boundary conditions. The study aimed to evaluate and verify this workflow through detailed qualitative and quantitative comparisons of the CFD and in vivo data. Based on data acquired from five TBAD patients, a range of essential model inputs was obtained, including inlet flow waveforms and 3-element Windkessel model parameters, which can be utilised in further studies where in vivo flow data is not available. Local and global analysis showed good consistency between CFD results and 4D-MRI data, with the maximum velocity in the primary entry tear differing by up to 0.3 m/s, and 80% of the analysed regions achieving moderate or strong correlations between the predicted and in vivo velocities. CFD predicted pressures were generally well matched to the Doppler-wire measurements, with some deviation in peak systolic values. Overall, this study presents a validated comprehensive workflow with extensive data for CFD simulation of TBAD.

Differences in the Area of Proximal and Distal Entry Tears at CT Angiography Predict Long-term Clinical Outcomes in Aortic Dissection

Purpose

To identify entry tear variables that are related to adverse clinical events by using CT angiography (CTA) performed during the subacute phase of aortic dissection.

Materials and Methods

In this prospective study conducted from January 2000 to December 2013, participants with an aortic dissection with a patent false lumen and no comorbidities underwent CTA during the subacute phase. Participants were followed up for a survival analysis to assess the time to an adverse aortic event (AAE). The maximum aortic diameter (MAD), proximal and distal tear areas and difference between these areas, and partial false-lumen thrombosis were assessed by using Cox regression for adverse events.

Results

Seventy-two participants (mean age, 55 years ± 12 [standard deviation]; 55 men) were evaluated: 47 were surgically treated (type A aortic dissection) and 25 were medically treated (type B aortic dissection). Twenty-two participants had an AAE manifest during follow-up (9.22 years ± 5.78): There were 18 elective surgeries for aneurysmal degeneration, two emergent surgeries for acute aortic syndrome, and two aortic condition-related deaths. A categorical model composed of genetic aortic disease (GAD) (hazard ratio [HR], 3.4 [95% CI: 1.2, 9.9]; P = .02), MAD greater than 45 mm (HR, 6.1 [95% CI: 2.4, 15.8]; P < .001), and tear dominance (HR, 5.2 [95% CI: 2.1, 13]; P < .001), defined as an absolute tear area difference of greater than 1.2 cm², was used to stratify participants into three risk groups: low, without any risk factors (57% [41 of 72] and 7% [three of 41] had events); intermediate, with one risk factor (31% [22 of 72] and 50% [11 of 22] had events); and high, with two or more risk factors (13% [nine of 72] and 89% [eight of nine] had events; log rank P < .001).

Conclusion

Tear dominance demonstrated at CTA performed in the subacute phase of aortic dissection was related to long-term adverse events. Participants without GAD, dominant tears, or MAD greater than 45 mm had conditions that were safely managed with optimal medical treatment and imaging follow-up.Keywords: CT Angiography, Vascular, Aorta, Dissection Supplemental material is available for this article. © RSNA, 2021See also commentary by Fleischmann and Burris in this issue.

Predictors of Long-Term Aortic Growth and Disease Progression in Patients with Aortic Dissection, Intramural Hematoma, and Penetrating Aortic Ulcer

BACKGROUND

We aimed to identify predictors of long-term aortic diameter change and disease progression in a population cohort of patients with newly diagnosed aortic dissection (AD), intramural hematoma (IMH), or penetrating aortic ulcer (PAU).

METHODS

We used the Rochester Epidemiology Project record linkage system to identify all Olmsted County, MN-USA, residents diagnosed with AD, IMH, and PAU (1995-2015). The endpoints were aortic diameter change, freedom from clinical disease progression (any related intervention, aortic aneurysm, new aortic syndrome, rupture or death) and disease resolution (complete spontaneous radiological disappear). Linear regression was used to assess aortic growth rate; predictors of disease progression were identified with Cox proportional hazards.

RESULTS

Of 133 incident cases, 46 ADs, 12 IMHs, and 28 PAUs with sufficient imaging data were included. Overall median follow-up was 8.1 years. Aortic diameter increase occurred in 40 ADs (87%, median 1.0 mm/year), 5 IMHs (42%, median 0.2 mm/year) and 14 PAUs (50%, median 0.4 mm/year). Symptomatic presentation (P = 0.045), connective tissue disorders (P = 0.005), and initial aortic diameter >42 mm (P = 0.013) were associated with AD growth rate. PAU depth >9 mm (P = 0.047) and female sex (P = 0.013) were associated with aortic growth rate in PAUs and IMHs. At 10 years, freedom from disease progression was 22% (95% CI 12-41) for ADs, 44% (95% CI 22-92) for IMHs, and 46% (95% CI 27-78) for PAUs. DeBakey I/IIIB AD (HR 3.09; P = 0.038), initial IMH aortic diameter (HR 1.4; P = 0.037) and PAU depth >10 mm (HR 3.92; P = 0.018) were associated with disease progression. No AD spontaneously resolved; resolution rate at 10 years was 22% (95% CI 0-45) for IMHs and 11% (95% CI 0-23) for PAUs.

CONCLUSIONS

Aortic growth and clinical disease progression are observed in most patients with aortic syndromes, while spontaneous resolution is uncommon. Predictors of aortic growth and disease progression may be used to tailor appropriate follow-up and eventual early intervention.

Postoperative Maximal Aortic Diameter is a Significant Predictor of Dilation of the Residual Dissected Aorta after Aortic Replacement for Acute Debakey Type I Aortic Dissection

BACKGROUND

This study investigated the impact of aortic diameter on late aortic dilation of the residual dissected aorta after tear-oriented aortic replacement for acute DeBakey type I aortic dissection.

METHODS

Of 133 patients who underwent aortic replacement for acute DeBakey type I/II aortic dissection between 2008 and 2019, 45 patients with a residual dissected aorta after surgery for acute DeBakey type I aortic dissection and who underwent computed tomography at predischarge and after 1 year were retrospectively assessed. The aortic diameter and false lumen area were measured at 3 levels: the maximal aortic site, seventh thoracic vertebra, and celiac axis. Multivariable Cox regression analysis was employed to identify the predictors of late aortic dilation, defined as an aortic growth rate of ≥5 mm/year or a maximal aortic diameter of ≥55 mm.

RESULTS

During a median follow-up of 75 [range: 13-152] months, 6 patients (5 men; mean age: 57 ± 14 years) experienced aortic dilation. All 6 patients had the maximal aortic diameter between the distal aortic arch and seventh thoracic vertebra level at the last computed tomography. Multivariable Cox regression analysis showed that the predischarge maximal aortic diameter was an independent determinant of late aortic dilation (hazard ratio: 2.28/mm, 95% confidence interval: 1.10-5.86).

CONCLUSIONS

Predischarge maximal aortic diameter is a significant predictor of late aortic dilation in patients with a residual dissected aorta after tear-oriented surgical repair of acute DeBakey type I aortic dissection.

Deep Learning-Based 3D Segmentation of True Lumen, False Lumen, and False Lumen Thrombosis in Type-B Aortic Dissection

Patients with initially uncomplicated typeB aortic dissection (uTBAD) remain at high risk for developing late complications. Identification of morphologic features for improving risk stratification of these patients requires automated segmentation of computed tomography angiography (CTA) images. We developed three segmentation models utilizing a 3D residual U-Net for segmentation of the true lumen (TL), false lumen (FL), and false lumen thrombosis (FLT). Model 1 segments all labels at once, whereas model 2 segments them sequentially. Best results for TL and FL segmentation were achieved by model 2, with median (interquartiles) Dice similarity coefficients (DSC) of 0.85 (0.77-0.88) and 0.84 (0.82-0.87), respectively. For FLT segmentation, model 1 was superior to model 2, with median (interquartiles) DSCs of 0.63 (0.40-0.78). To purely test the performance of the network to segment FLT, a third model segmented FLT starting from the manually segmented FL, resulting in median (interquartiles) DSCs of 0.99 (0.98-0.99) and 0.85 (0.73-0.94) for patent FL and FLT, respectively. While the ambiguous appearance of FLT on imaging remains a significant limitation for accurate segmentation, our pipeline has the potential to help in segmentation of aortic lumina and thrombosis in uTBAD patients.Clinical relevance- Most predictors of aortic dissection (AD) degeneration are identified through anatomical modeling, which is currently prohibitive in clinical settings due to the timeintense human interaction. False lumen thrombosis, which often develops in patients with type B AD, has proven to show significant prognostic value for predicting late adverse events. Our automated segmentation algorithm offers the potential of personalized treatment for AD patients, leading to an increase in long-term survival.

Atypical Presentation of Descending Aortic Dissection in an Acute Heart Failure Patient

Aortic dissection is relatively uncommon, but often presents with acute severe chest or back pain and acute hemodynamic compromise and is associated with high mortality. We present a case of aortic dissection with an atypical presentation in a heart failure patient and the challenges encountered to make the diagnosis. The patient was a 54-year-old African American female who presented with progressively worsening exertional dyspnea and orthopnea for three days and sensation of indigestion and bloating. The patient denied any recent history of chest pain and she was initially admitted for heart failure exacerbation. Her admission chest x-ray showed severe cardiomegaly with a prominence of pulmonary vascular but there was a borderline widening of mediastinum measuring 8.2 cm. Physical exam showed unequal dorsalis pedis pulses (fainter on the right side) and systolic blood pressure difference of more than 20 mmHg between bilateral upper extremities. Computed tomography angiography (CTA) of chest, abdomen, and pelvis confirmed the diagnosis of dissection of thoracic and abdominal aorta extending from the left subclavian artery to the femoral artery. The patient was managed with labetalol drip and later transferred to a tertiary center for an elevated level of care where the endovascular intervention was performed. The patient then followed up with a vascular clinic for serial CTA and heart failure clinic for optimization of core measures. In conclusion, this case highlights the importance of clinical suspicion of aortic dissection and discusses the various clinical presentations of aortic dissection and its management. Being a highly fatal condition, prompt diagnosis is extremely important and is often life-saving. Therefore, it is important for physicians to be aware of atypical presentations of aortic dissection to initiate timely interventions to avoid catastrophic complications.

Extended Stent Coverage Decreases Distal Aortic Segmental Enlargement After the Endovascular Repair of Acute Complicated Type B Aortic Dissection: A Multi-Center Retrospective Study of 814 Patients

PURPOSE

This study aimed to investigate the effect of distal aortic segmental enlargement (DASE) after thoracic endovascular aortic repair for complicated type B aortic dissection (cTBAD).

MATERIALS AND METHODS

From March 2003 to October 2018, 814 patients with acute cTBAD from 5 medical centers were retrospectively identified. DASE is indicated as the enlargement of distal aortic segmental volume ≥1.6 fold of the preoperative volume compared with the most recent postoperative computed tomography angiography (CTA) scan. Of these patients, 635 (78%) were identified as non-DASE, and 179 (22%) were identified as DASE. Competing risk analysis was performed to compare late death and distal aortic reintervention between the groups. The morphological variables and false lumen thrombosis at 7 aortic levels were measured based on the preoperative CTA and the most recent CTA. Univariate and multivariate Cox regression analyses were used to assess the independent predictors of DASE.

RESULTS

The mean follow-up time of the entire cohort was 5.6 years (interquartile range: 2.4-8.3 years). There were total of 208 late deaths, including 94 (14.8%) deaths in non-DASE group versus 114 (63.7%) deaths in the DASE group. Distal aortic reintervention was observed in 89 patients, with 43(6.7%) in the non-DASE group versus 46 (25.7%) in the DASE group. The cumulative incidence of late death and distal aortic reintervention were significantly higher in the DASE than in the non-DASE group (p<0.001). In morphological analysis, significant incomplete false lumen thrombosis was observed in all distal aortic segments above the aortic level of celiac artery (p<0.01). According to multivariate analysis, the Marfan syndrome, stent coverage to the level of diaphragm and the level of celiac artery were independent predictors of the DASE (p<0.001). Patients with extended stent coverage to the level of celiac artery have shown a lower incidence of DASE (p<0.010).

CONCLUSION

Compared with the non-DASE group, patients with DASE demonstrated a higher rate of late death and distal aortic reintervention. For the cTBAD population, extended stent-graft coverage to the aortic section between diaphragm and celiac artery might serve as a "cost-efficient" cutoff point aiming to reduce the risk of DASE.

Artificial intelligence and machine learning in aortic disease

PURPOSE OF REVIEW

Discuss foundational concepts for artificial intelligence (AI) and review recent literature on its application to aortic disease.

RECENT FINDINGS

Machine learning (ML) techniques are rapidly evolving for the evaluation of aortic disease - broadly categorized as algorithms for aortic segmentation, detection of pathology, and risk stratification. Advances in deep learning, particularly U-Net architectures, have revolutionized segmentation of the aorta and show potential for monitoring the size of aortic aneurysm and characterizing aortic dissection. These algorithms also facilitate application of more complex technologies including analysis of flow dynamics with 4D Flow magnetic resonance imaging (MRI) and computational simulation of fluid dynamics for aortic coarctation. In addition, AI algorithms have been proposed to assist in 'opportunistic' screening from routine imaging exams, including automated aortic calcification score, which has emerged as a strong predictor of cardiovascular risk. Finally, several ML algorithms are being explored for risk stratification of patients with aortic aneurysm and dissection, in addition to prediction of postprocedural complications.

SUMMARY

Multiple ML techniques have potential for characterization and risk prediction of aortic aneurysm, dissection, coarctation, and atherosclerotic disease on computed tomography and MRI. This nascent field shows considerable promise with many applications in development and in early preclinical evaluation.

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.

False lumen ejection fraction predicts growth in type B aortic dissection: preliminary results

OBJECTIVES

Current risk assessment strategies in type B aortic dissection are focused on anatomic parameters, although haemodynamic abnormalities that result in false lumen (FL) pressurization are thought to play a significant role in aortic growth. The objective of this study was to evaluate blood flow of the FL using 4D flow magnetic resonance imaging (MRI) and identify haemodynamic and anatomic factors that independently predict the rate of aortic growth.

METHODS

Patients with dissection of the descending thoraco-abdominal aorta (n = 18) were enrolled in a prospective observational study and underwent 4D flow MRI for haemodynamic assessment of the entry tear and FL. Anatomic parameters were obtained by magnetic resonance angiography and baseline computed tomography. False lumen ejection fraction (FL EF) was defined the ratio of retrograde flow rate at the dominant entry tear during diastole over the antegrade systolic flow rate.

RESULTS

The median aortic growth rate was 3.5 mm/year (interquartile range 0.5-8.1 mm/year). Entry tear peak velocity was lower in patients with enlarging aortic dimensions (95.5 ± 24.1 vs 128.1 ± 37.4 cm/s, P = 0.039). After adjusting for co-variates FL EF (β = 0.15, P = 0.004), baseline maximal aortic diameter (β = 0.37, P = 0.001) and the entry tear distance from the left subclavian artery (β = 0.07, P = 0.016) were significant predictors of aortic growth rate.

CONCLUSIONS

Beyond standard anatomic risk factors, FL EF is an independent predictor of aortic growth rate and may represent an intuitive, non-invasive method to estimate FL pressurization and improve patient-specific risk assessment in patients with type B aortic dissection.

The characteristics of distal tears affect false lumen thrombosis rate after thoracic endovascular aortic repair for acute type B dissection

OBJECTIVES

A low false lumen thrombosis rate (FLTR) is common in patients with type B aortic dissection after they have undergone thoracic endovascular aortic repair, which indicates a poor long-term prognosis. This study aimed to establish a quantitative linear regression model to predict false lumen (FL) thrombosis accurately using morphological parameters.

METHODS

In this retrospective study, we included 59 patients diagnosed with acute type B aortic dissection between 2014 and 2017. Morphological parameters were measured. Univariable and multivariable linear regression analyses were performed, and a linear regression model relating FLTR with the number of re-entry tears was proposed. Ten patients were further chosen to validate the linear relationship, and idealized aortic dissection models were adopted for haemodynamic analysis.

RESULTS

Only the total area and number of re-entry tears were negatively correlated with FL thrombosis (P < 0.001). Moreover, based on the univariable regression, the number of re-entry tears played a more crucial role in FLTR (R2 = 0.509 vs R2 = 0.298), and the linear relationship model was created as follows: thrombosis rate (%) = -11.25 × distal tear number + 105.24. This model was perfectly matched in 10 patients (concordance correlation coefficient = 0.880, P = 0.947). Moreover, when the total area of re-entry tears was constant, the net blood flow increased rapidly with an increase in the tear count.

CONCLUSIONS

The number of re-entry tears could be a crucial related factor of FL thrombosis; the larger the number of re-entry tears is, the lower the possibility of thrombosis is.

False lumen pressure estimation in type B aortic dissection using 4D flow cardiovascular magnetic resonance: comparisons with aortic growth

BACKGROUND

Chronic type B aortic dissection (TBAD) is associated with poor long-term outcome, and accurate risk stratification tools remain lacking. Pressurization of the false lumen (FL) has been recognized as central in promoting aortic growth. Several surrogate imaging-based metrics have been proposed to assess FL hemodynamics; however, their relationship to enlarging aortic dimensions remains unclear. We investigated the association between aortic growth and three cardiovascular magnetic resonance (CMR)-derived metrics of FL pressurization: false lumen ejection fraction (FLEF), maximum systolic deceleration rate (MSDR), and FL relative pressure (FL ΔPmax).

METHODS

CMR/CMR angiography was performed in 12 patients with chronic dissection of the descending thoracoabdominal aorta, including contrast-enhanced CMR angiography and time-resolved three-dimensional phase-contrast CMR (4D Flow CMR). Aortic growth rate was calculated as the change in maximal aortic diameter between baseline and follow-up imaging studies over the time interval, with patients categorized as having either 'stable' (< 3 mm/year) or 'enlarging' (≥ 3 mm/year) growth. Three metrics relating to FL pressurization were defined as: (1) FLEF: the ratio between retrograde and antegrade flow at the TBAD entry tear, (2) MSDR: the absolute difference between maximum and minimum systolic acceleration in the proximal FL, and (3) FL ΔPmax: the difference in absolute pressure between aortic root and distal FL.

RESULTS

FLEF was higher in enlarging TBAD (49.0 ± 17.9% vs. 10.0 ± 11.9%, p = 0.002), whereas FL ΔPmax was lower (32.2 ± 10.8 vs. 57.2 ± 12.5 mmHg/m, p = 0.017). MSDR and conventional anatomic variables did not differ significantly between groups. FLEF showed positive (r = 0.78, p = 0.003) correlation with aortic growth rate whereas FL ΔPmax showed negative correlation (r = - 0.64, p = 0.026). FLEF and FL ΔPmax remained as independent predictors of aortic growth rate after adjusting for baseline aortic diameter.

CONCLUSION

Comparative analysis of three 4D flow CMR metrics of TBAD FL pressurization demonstrated that those that focusing on retrograde flow (FLEF) and relative pressure (FL ΔPmax) independently correlated with growth and differentiated patients with enlarging and stable descending aortic dissections. These results emphasize the highly variable nature of aortic hemodynamics in TBAD patients, and suggest that 4D Flow CMR derived metrics of FL pressurization may be useful to separate patients at highest and lowest risk for progressive aortic growth and complications.

False lumen enhancement characteristics on computed tomography angiography predict risk of aneurysm formation in acute type B aortic dissection

OBJECTIVES

Differential luminal enhancement [between true lumen (TL) and false lumen (FL)] results from differential flow patterns, most likely due to outflow restriction in the FL. We aimed to assess the impact of differential luminal enhancement at baseline computed tomography angiography on the risk of adverse events in patients with acute type B aortic dissection (TBAD).

METHODS

Baseline computed tomography angiographies of patients with acute TBAD between 2007 and 2016 (n = 48) were analysed using three-dimensional software at multiple sites along the descending thoraco-abdominal aorta. At each location, we measured contrast density in TL and FL [Houndsfield unit (HU)], maximal diameter (cm) and circumferential FL extent (°). Outcome data were collected via retrospective chart review. Multivariable logistic regression models were employed to determine the independent risk of TL-FL differential luminal enhancement on aneurysm formation (maximal diameter ≥55 mm) and medical treatment failure.

RESULTS

Patients were predominately male (75%) and 52.8±12.9 years at diagnosis. The mean follow-up was 5.9±2.6 years, and 42% (n = 20/48) patients were diagnosed with thoraco-abdominal aortic aneurysm. The baseline absolute difference between FL and TL contrast density measured at 2 cm distal to primary entry tear (TL-FLabs-Tear) was significantly higher among patients who developed aneurysm (26 HU, IQR: 15-53 vs 13 HU, IQR: 4-24, P = 0.001). Aneurysm development during follow-up was predicted by TL-FLabs-Tear (odds ratio 1.07, P = 0.012) and baseline maximal aortic diameter (odds ratio 1.90, P < 0.001). High (≥18 HU) differential luminal enhancement was associated with lower rates of aneurysm-free survival and higher rates of medical treatment failure.

CONCLUSIONS

Differential luminal enhancement may be a novel predictor of aneurysm formation among patients with acute TBAD.