Computed Tomography Imaging Features in Acute Uncomplicated Stanford Type-B Aortic Dissection Predict Late Adverse Events

Predictors of Late Adverse Events in Patients with Surgically Treated Type I Aortic Dissection

OBJECTIVE

Residual aortic dissection (AD) following DeBakey type I AD repair is associated with a high rate of adverse events that need additional intervention or surgery. This study aimed to identify clinical and early post-operative computed tomography angiography (CTA) imaging factors associated with adverse events in patients with type I AD after ascending aorta replacement.

METHODS

This single centre, retrospective cohort study included consecutive patients with type I AD who underwent ascending aorta replacement from January 2011 to December 2017 and post-operative CTA within three months. The primary outcome was AD related adverse events, defined as AD related death and re-operation due to aortic aneurysm or impending rupture. The location and size of the primary intimal tears, aortic diameter, and false lumen status were evaluated. Regression analyses were performed to identify factors associated with AD related adverse events. A decision tree model was used to classify patients as high or low risk.

RESULTS

Of 103 participants (55.43 ± 13.94 years; 49.5% male), 24 (23.3%) experienced AD related adverse events. In multivariable Cox regression analysis, connective tissue disease (hazard ratio [HR] 15.33; p < .001), maximum aortic diameter ≥ 40 mm (HR 4.90; p < .001), and multiple (three or more) intimal tears (HR 7.12; p < .001) were associated with AD related adverse events. The three year cumulative survival free from AD related events was lower in the high risk group with aortic diameter ≥ 40 mm and multiple intimal tears (41.7% vs. 90.9%; p < .001).

CONCLUSION

Early post-operative CTA findings indicating a maximum aortic diameter ≥ 40 mm and multiple intimal tears may predict a higher risk of adverse events. These findings suggest the need for careful monitoring and more vigilant management approaches in these cases.

Early three-dimensional growth in uncomplicated type B aortic dissection is associated with long-term outcomes

OBJECTIVE

Late adverse events (LAEs) are common among initially uncomplicated type B aortic dissection (uTBAD); however, identifying those patients at highest risk of LAEs remains a significant challenge. Early false lumen (FL) growth has been suggested to increase risk, but confident determination of growth is often hampered by error in two-dimensional clinical measurements. Semi-automated three-dimensional (3D) mapping of aortic growth, such as by vascular deformation mapping (VDM), can potentially overcome this limitation using computed tomography angiograms (CTA). We hypothesized that FL growth in the early pre-dissection phase by VDM can accurately predict LAEs.

METHODS

We performed a two-center retrospective study of patients with uTBAD, with paired CTAs in the acute (1-14 days) and subacute/early chronic (1-6 months) periods. VDM analysis was used to map 3D growth. Standard clinical CT measures (ie, aortic diameters, tear characteristics) were also collected. Multivariate analysis was conducted using a decision tree and Cox proportional hazards model. LAEs were defined as aneurysmal FL (>55 mm); rapid growth (>5 mm within 6 months); aorta-specific mortality, rupture, or re-dissection.

RESULTS

A total of 107 (69% male) patients with uTBAD initially met inclusion criteria with a median follow-up of 7.3 years (interquartile range [IQR], 4.7-9.9 years). LAEs occurred in 72 patients (67%) at 2.5 years (IQR, 0.7-4.8 years) after the initial event. A multivariate decision tree model identified VDM growth (>2.1 mm) and baseline diameter (>42.7 mm) as optimal predictors of LAEs (area under the receiver operating characteristic curve = 0.94), achieving an 87% accuracy (sensitivity of 93%, specificity of 76%) after leave-one-out validation. Guideline reported high-risk features were not significantly different between groups.

CONCLUSIONS

Early growth of the FL in uTBAD was the best tested indicator for LAEs and improves upon the current gold-standard of baseline diameter in selecting patients for early prophylactic thoracic endovascular aortic repair.

Predictors for thoracic aortic growth in patients with type B aortic dissection after thoracic endovascular aortic repair

OBJECTIVE

To identify independent predictors of thoracic aortic growth in patients with type B aortic dissection (TBAD) undergoing thoracic endovascular aortic repair (TEVAR).

METHODS

A retrospective analysis of the patients undergoing TEVAR for TBAD or intramural hematoma (IMH) from April 2014 to April 2023 was performed. The baseline morphological data of TBAD was established through computed tomography angiography (CTA) before discharge. Patients were divided into two groups based on aortic growth: growth and no growth. Aortic growth defined as an increase ≥5 mm in thoracic maximal aortic diameter during any serial follow-up CTA measurement. Logistic regression following propensity score matching (PSM) was used to identify independent predictors for aortic growth. Receiver operating characteristic curve and cutoff value of independent predictors were calculated. Linear regression was used to establish a correlation between anatomical variables and follow-up aortic diameter.

RESULTS

A total of 145 patients with TBAD (n = 122) or IMH (n = 23) undergoing TEVAR were included, with a male of 83.4% and a mean age of 56 ± 14.1 years. Patients in growth group and no growth group was 26 (17.9%) and 119 (80.1%), respectively. After using PSM method, matched regression analysis showed residual maximal tear diameter (OR = 0.889, 95% CI 0.830-0.952, p = 0.001) and follow-up aortic diameter (OR = 0.977, 95% CI 0.965-0.989, p < 0.001) were independent predictors for aortic growth. The cutoff value was 8.55 mm for residual tear diameter and 40.65 mm for follow-up maximal aortic diameter. The residual maximal tear diameter showed a linear correlation with follow-up aortic diameter (DW = 1.74, R2 = 6.2%, p = 0.033).

CONCLUSIONS

This study suggested that residual maximal tear diameter >8.55 mm and follow-up aortic diameter >40.65 mm could predict aortic growth in patients with TBAD undergoing TEVAR.

Development and Validation of a User Friendly Morphology Grading System (PATENT) Predicting Aortic Remodelling After Thoracic Endovascular Aortic Repair in High Risk Uncomplicated Type B Aortic Dissection

OBJECTIVE

This study aimed to create a morphology grading system, solely based on 2D images from computed tomography angiography, to predict negative aortic remodelling (NAR) for patients with high risk uncomplicated type B aortic dissection (TBAD) after thoracic endovascular aortic repair (TEVAR).

METHODS

This single centre retrospective cohort study extracted and analysed consecutive patients diagnosed with high risk uncomplicated TBAD. Negative aortic remodelling was defined as an increase in the false lumen or total aortic diameter, or decrease in the true lumen diameter. The multivariable Cox regression model identified risk factors and a prediction model was created for two year freedom from NAR. A three category grading system, in which patients were classified into low, medium, and high risk groups, was further developed and internally validated.

RESULTS

Of 351 patients included, 99 (28%) developed NAR. The median age was 52 years (interquartile range 45, 62 years) and 56 (16%) were female. The rate of two year freedom from NAR was 71% (95% CI 65 - 77%). After the multivariable Cox regression analysis, Patent false lumen, Aberrant right subclavian artery, Taper ratio, abdominal circumferential Extent, coeliac artery or reNal artery involved, and four channel dissection (Three false lumens) remained independent predictors and were included in the PATENT grading system. The risk score was statistically significantly associated with NAR (HR 1.21; 95% CI 1.14 - 1.29; p < .001). The medium and high risk groups demonstrated a higher rate of NAR (medium risk, HR 2.82; 95% CI 1.57 - 5.01; p = .001; high risk, HR 4.39; 95% CI 2.58 - 7.48; p < .001). The grading system was characterised by robust discrimination with Harrell's C index of 0.68 (95% CI 0.63 - 0.75).

CONCLUSION

The PATENT grading system was characterised by good discrimination and calibration, which may serve as a clinician friendly tool to aid risk stratification for TBAD patients after TEVAR.

Discussing on the Aortic Coverage in Type B Aortic Dissection Treatment: A Comprehensive Scoping Review

OBJECTIVE

The objective of this study is to investigate and address the question surrounding the determination of the optimal endograft length of coverage during TEVAR for type B aortic dissection (TBAD), with a particular emphasis on the distal landing zone (DLZ).

DATA SOURCES

MEDLINE, Scopus, and Web of Science databases were used.

METHODS

The PRISMA-ScR statement was followed.

RESULTS

Several variables can contribute to the length of coverage during TEVAR in TBAD patient. Baseline patient's characteristics, TBAD-related features, the type of endoprosthesis, and postoperative graft behaviour may contribute to the choice of coverage.

CONCLUSIONS

No robust data have been published regarding the optimal length of TEVAR. Therefore, reporting the percentage of covered aorta and improving computational studies should be valorised to improve postoperative outcomes.

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.

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.

Deep learning-based radiomics of computed tomography angiography to predict adverse events after initial endovascular repair for acute uncomplicated Stanford type B aortic dissection

PURPOSE

This study aimed to construct a predictive model integrating deep learning-derived radiomic features from computed tomography angiography (CTA) and clinical biomarkers to forecast postoperative adverse events (AEs) in patients with acute uncomplicated Stanford type B aortic dissection (uTBAD) undergoing initial thoracic endovascular aortic repair (TEVAR).

METHODS

We retrospectively evaluated 369 patients treated with TEVAR for acute uTBAD from January 2015 to December 2022. A three-dimensional (3D) deep convolutional neural network (CNN) automated radiomic feature extraction from CTA images. Feature selection, using Analysis of Variance (ANOVA) and the Least Absolute Shrinkage and Selection Operator (LASSO) algorithms, refined a radiomic score (Rad-Score). This score, alongside clinical parameters, was modelled via Extreme Gradient Boosting (XGBoost) analysis. Model calibration was assessed by calibration curves.

RESULTS

The integration of the Rad-Score with clinical factors including albumin and C-reactive protein levels moderately enhanced predictive efficiency, exhibiting an area under the curve (AUC) of 1.000 (95%CI, 1.000-1.000) in the training cohort and 0.990 (95%CI, 0.966-1.000) in the internal validation cohort. In an independent validation cohort from another hospital, the combined model yielded an AUC of 0.985 (95%CI, 0.965-1.000), with an accuracy, precision, sensitivity, and specificity of 0.92, 0.92, 0.94, and 0.91, respectively.

CONCLUSIONS

The synergistic application of deep learning-based radiomics from CTA and clinical indicators holds promise for anticipating AEs post-initial thoracic endovascular aortic repair in patients with acute uTBAD. The clinical utility of the constructed combined model, offering prognostic foresight during follow-up, has been substantiated.

Predicting adverse events after thoracic endovascular aortic repair for patients with type B aortic dissection

The potential of adverse events (AEs) after thoracic endovascular aortic repair (TEVAR) in patients with type B aortic dissection (TBAD) has been reported. To avoid the occurrence of AEs, it is important to recognize high-risk population for prevention in advance. The data of 261 patients with TBAD who received TEVAR between June 2017 and June 2021 at our medical center were retrospectively reviewed. After the implementation of exclusion criteria, 172 patients were finally included, and after 2.8 years (range from 1 day to 5.8 years) of follow up, they were divided into AEs (n = 41) and non-AEs (n = 131) groups. We identified the predictors of AEs, and a prediction model was constructed to calculate the specific risk of postoperative AEs at 1, 2, and 3 years, and to stratify patients into high-risk (n = 78) and low-risk (n = 94) group. The prediction model included seven predictors: Age > 75 years, Lower extremity malperfusion (LEM), NT-proBNP > 330 pg/ml, None distal tear, the ratio between the diameter of the ascending aorta and descending aorta (A/D ratio) > 1.2, the ratio of the area of the false lumen to the total aorta (FL ratio) > 64%, and acute TEVAR, which exhibited excellent predictive accuracy performance and discriminatory ability with C statistic of 82.3% (95% CI 77.3-89.2%). The prediction model was contributed to identify high-risk patients of postoperative AEs, which may serve to achievement of personalized treatment and follow-up plans for patients.

False lumen regurgitation fraction and energy loss in the aorta measured using four-dimensional flow MRI to predict expansion of acute uncomplicated type B aortic dissection: a prospective study

AIM

To assess the relationship between four-dimensional (4D)-flow-derived false lumen regurgitation fraction (FLRF) and energy loss (EL) percentage in the descending thoracic aorta (DTA) with the aortic growth rate in uncomplicated type B aortic dissection (uTBAD).

METHODS AND MATERIALS

In this prospective study performed on 15 patients with uTBAD, computed tomography (CT) angiography and 4D-flow magnetic resonance imaging (MRI) were performed at the initial presentation with follow-up CT at 2 years. 4D-flow parameters, including maximum peak systolic velocity (PSV), FLRF, and percentage of EL were measured using Circle CV42. The significance of these parameters for expansion (>3 mm/year) of aortic dissection was analysed.

RESULTS

Five patients had an enlarging aorta, while 10 had a stable aortic size. The Mann-Whitney U-test showed entry tear >10 mm (p=0.026), FLRF (7.6 ± 8.9 versus 64.8 ± 16.7%; p=0.002), EL in the DTA in (1.61 ± 1.99 versus 2.21 ± 0.32 μW/cm3; p=0.014) and percentage of EL in the DTA to overall energy loss from the ascending aorta to the DTA (37 ± 15% versus 66 ± 17%; p=0.005), having a statistically significant different expanding stable dissection. A positive significant Spearman correlation was noted with the aortic growth rate (in millimetres over 2 years) with FLRF (r=0.71, p=0.003), EL in the DTA (r=0.56, p=0.007), and percentage of EL in the DTA (r=0.62, p=0.003).

CONCLUSION

4D flow parameters, including FLRF and the percentage amount of EL in the DTA may help predict aortic growth at an early stage in uTBAD.

Investigating the Role of Thrombosis, Fenestration, and False Lumen Orbital Orientation in the Hemodynamics of Type B Aortic Dissection

While much about the fundamental mechanisms behind the initiation and progression of Type B aortic dissection (TBAD) is still unknown, predictive models based on patient-specific computational fluid dynamics (CFD) can help in risk stratification and optimal clinical decision-making. Aiming at the development of personalized treatment, CFD simulations can be leveraged to investigate the interplay between complex aortic flow patterns and anatomical features. In this study, the hemodynamics of false lumen thrombosis, a large fenestration, and the orbital orientation of the false lumen is studied through image-based CFD simulations on three TBAD patient-specific geometries. A new pipeline was developed leveraging the open-source software SimVascular and Paraview to analyze multiple patients simultaneously and to achieve large-scale parallelization in CFD results based on patients' computed tomography (CT) images. The results of this study suggest that the internal orbital orientation of the false lumen contributes to maintaining a positive luminal pressure difference Δ P T L - F L = P T L - P F L between the true lumen (TL) and the false lumen (FL), despite an impingement area in the false lumen near the entry tear. A positive and high luminal pressure difference is thought to promote TL expansion and FL compression. Moreover, it was also found that both FL thrombosis at the entry tear region, and the presence of a large fenestration in the descending thoracic aorta reduce the magnitude of the negative luminal pressure difference, which in turn may reduce FL expansion and the risk of unstable aortic growth.

Incidence, presentation and outcome of acute aortic dissection: results from a population-based study

OBJECTIVES

To describe the incidence of acute aortic dissection in a clearly defined population, to assess onset symptoms and admission biochemical marker levels and to analyse variables potentially associated to mortality.

METHODS

Medical records and CT angiograms of all patients hospitalised for acute aortic dissection in the Stockholm County during the 5-year period 2012-2016 were reviewed. The patients were followed until date of death or until 31 December 2020. The annual incidence was determined. Associations between clinical and biochemical variables and 30-day mortality, respectively, were analysed using multivariable logistic regression models.

RESULTS

A total of 344 patients were included. The mean annual incidence of acute aortic dissection was 4.1 per 100 000. Median age was 67 years (range 24-91) and 34% (n=118) were women. Type A dissection was predominant; 220 patients (64%) had type A and 124 (36%) had type B. Painless dissection was more common in type A than in type B (18% vs 15%, p=0.003). Type A dissection patients also more commonly had elevated plasma troponin T (44% vs 21%, p<0.001) and thrombocytopenia (26% vs 15%, p=0.010) than type B dissection patients on admission. Overall, 30-day mortality was 28% in type A and 11% in type B (p<0.001). Both painless dissection (OR 4.30, 95% CI 1.80 to 10.28, p=0.001) and elevated troponin T (OR 3.78, 95% CI 2.01 to 7.12, p<0.001), respectively, were associated with increased 30-day mortality in all acute aortic dissection patients. Thrombocytopenia was associated with elevated 30-day mortality only in patients with type A (OR 3.09, 95% CI 1.53 to 6.21, p=0.002).

CONCLUSIONS

Nearly two-thirds of acute aortic dissection patients had type A. Levels of troponin T and platelets, respectively, paired with presence or absence of typical symptoms may become useful adjuncts in risk stratification of patients with acute aortic dissection.

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.

The Influence of Minor Aortic Branches in Patient-Specific Flow Simulations of Type-B Aortic Dissection

Type-B aortic dissection (TBAD) is a disease in which a tear develops in the intimal layer of the descending aorta forming a true lumen and false lumen (FL). Because disease outcomes are thought to be influenced by haemodynamic quantities such as pressure and wall shear stress (WSS), their analysis via numerical simulations may provide valuable clinical insights. Major aortic branches are routinely included in simulations but minor branches are virtually always neglected, despite being implicated in TBAD progression and the development of complications. As minor branches are estimated to carry about 7-21% of cardiac output, neglecting them may affect simulation accuracy. We present the first simulation of TBAD with all pairs of intercostal, subcostal and lumbar arteries, using 4D-flow MRI (4DMR) to inform patient-specific boundary conditions. Compared to an equivalent case without minor branches, their inclusion improved agreement with 4DMR velocities, reduced time-averaged WSS (TAWSS) and transmural pressure and elevated oscillatory shear in regions where FL dilatation and calcification were observed in vivo. Minor branch inclusion resulted in differences of 60-75% in these metrics of potential clinical relevance, indicating a need to account for minor branch flow loss if simulation accuracy is sought.

Early Thoracic Endovascular Aortic Repair of Uncomplicated Type B Thoracic Aortic Dissection: An Aorta Team Approach

BACKGROUND

 Although uncomplicated Type B aortic dissection (uTBAD) is traditionally treated with optimal medical therapy (OMT) as per guidelines, recent studies, performed primarily in interventional radiology or surgical operating rooms, suggest superiority of thoracic endovascular aortic repair (TEVAR) over OMT due to recent advancements in endovascular technologies. We report a large, single-center, case control study of TEVAR versus OMT in this population, undertaken solely in a cardiac catheterization laboratory (CCL) with a cardiologist and surgeon. We aimed to determine if TEVAR for uTBAD results in better outcomes compared with OMT.

METHODS

 This was a retrospective chart review of all patients with uTBAD during the last 13 years, with 46 cases (TEVAR group) and 56 controls (OMT group).

RESULTS

 In the TEVAR group, the procedure duration of 2.5 hours resulted in 100% procedural success for stent placement, with 63% undergoing protective left subclavian artery bypass, 0% mortality or stroke, and a lower readmission rate (1 vs. 2%; p = 0.04 in early TEVAR cases), but a longer length of stay (12.9 vs. 8.5 days: p = 0.006). The risk of all-cause long-term mortality was markedly reduced in the TEVAR group (RR = 0.38; p = 0.01), irrespective of early (<14 days) versus late intervention. On follow-up computed tomography imaging, the false lumen stabilized or decreased in 85% of cases, irrespective of intervention timing.

CONCLUSION

 TEVAR performed solely in the CCL is safe and effective, with lower all-cause mortality than OMT. These data, in collaboration with previous data on TEVAR in different settings, call for consideration of an update of practice guidelines.

Questionable Long-Term Results of the Extended Provisional Extension to Induce Complete Attachment (E-PETTICOAT) Technique in the Management of Chronic Type B Aortic Dissection

BACKGROUND

Published interim results of the extended provisional extension to induce complete attachment (e-PETTICOAT) technique suggested favorable remodeling in chronic type B Aortic Dissection (cTBAD). This report presents long-term results of the e-PETTICOAT technique for the management of cTBAD (without aneurysmal dilatation).

METHODS

Patients with cTBAD below the 55 mm aortic size were eligible for the management using the e-PETTICOAT technique. Follow-up was conducted at 1, 2 and 5 years based on the computed tomography angiogram. All the presurgery risk factors (entry >1 cm, inner curve entry, fusiform index >0.65, false lumen > 22 mm, aortic size >40 mm, recurrent pain or hypertension, and Stanford Dissection Risk Calculation) and postsurgery complications were examined in the study.

RESULTS

A total of 20 patients underwent the e-PETTICOAT surgery. The survival rate at 1, 2, and 5 years was 75%, 70%, and 64%, respectively, and the percentage of patients without any reinterventions was 100%, 93%, and 18%. Aortic degeneration was recognized in 30%, 55%, and 85% of the patients. Only 3 of the 20 patients were alive and without any reintervention after 5 years. The receiver operating curve analysis does not indicate any factor that would predict the remodeling result in the long-term follow-up.

CONCLUSIONS

The use of e-PETTICOAT technique in cTBAD might not have a beneficial influence on the long-term results.

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.

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.

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.

Current Understanding of Aortic Dissection

The aorta is the largest artery in the body, delivering oxygenated blood from the left ventricle to all organs. Dissection of the aorta is a lethal condition caused by a tear in the intimal layer of the aorta, followed by blood loss within the aortic wall and separation of the layers to full dissection. The aorta can be affected by a wide range of causes including acute conditions such as trauma and mechanical damage; and genetic conditions such as arterial hypertension, dyslipidaemia, and connective tissue disorders; all increasing the risk of dissection. Both rapid diagnostic recognition and advanced multidisciplinary treatment are critical in managing aortic dissection patients. The treatment depends on the severity and location of the dissection. Open surgical repair is the gold standard of treatment for dissections located to the proximal part of the aorta and the arch, while endovascular interventions are recommended for most distal or type B aortic dissections. In this review article, we examine the epidemiology, pathophysiology, contemporary diagnoses, and management of aortic dissection.

The extended PETTICOAT technique does not guarantee favorable remodeling after acute type B aortic dissection

Introduction

Favorable remodeling is not always observed after thoracic endovascular aortic repair (TEVAR) in acute complicated type B aortic dissection (TBAD). Existing distal re-entries might be the cause of that. Many more extensive techniques have been introduced and evaluated. None of them achieve proven benefit in long-term follow-up.

Aim

A new technique called extended PETTICOAT (provisional extension to induce complete attachment) or e-PETTICOAT technique was published in 2018. It allows one to cover proximal and distal re-entries and consists of: combined implantation of a thoracic stent graft to seal the proximal entry; self-expandable stents in the visceral aorta to expand the true lumen; plus two parallel kissing iliac stent grafts below the renal arteries. Despite encouraging medium term results, it has unknown long-term consequences.

Material and methods

The prospective observational single center study included 11 patients with complicated acute TBAD qualified for endovascular treatment using the e-PETTICOAT technique. Complicated acute TBAD was identified only in cases of clinical manifestation before or at the time of intervention; radiological findings were not sufficient to identify complications in our study. Method: The 5-year follow-up, based on clinical outcome including survival, re-interventions and angio-CT-assessed remodeling, was examined.

Results

The e-PETTICOAT technique achieves good remodeling in 38% of primary and 88% of secondary procedures.

Conclusions

The E-PETTICOAT does not guarantee favorable remodeling during a 5-year follow-up in acute complicated TBAD. Complex aortic repair after e-PETTICOAT might be needed.

False Lumen Flow Assessment by Magnetic Resonance Imaging and Long-Term Outcomes in Uncomplicated Aortic Dissection

BACKGROUND

Despite the absence of clinical complications after an acute aortic dissection (AD) with persistent patent false lumen (FL), a high risk for clinical events may persist.

OBJECTIVES

The aim of this study was to assess the natural evolution of noncomplicated AD and ascertain whether different FL flow patterns by magnetic resonance imaging (MRI) have independent prognostic value for AD-related events beyond established morphologic parameters.

METHODS

One hundred thirty-one consecutive patients, 78 with surgically treated type A dissections and 53 with medically treated type B dissections, were followed up prospectively after acute AD with persistent patent FL in the descending aorta. Maximum aortic diameter, true lumen compression, entry tear, and partial FL thrombosis by computed tomography were assessed. Systolic antegrade true lumen and FL flow volumes and diastolic antegrade and retrograde flows were analyzed by MRI during the first year after AD.

RESULTS

After a median follow-up period of 8.0 years (IQR: 4.6-10.9 years), 43 patients presented aorta-related events (25 died and 18 required endovascular treatment). FL systolic antegrade flow ≥30% with respect to total systolic antegrade flow and retrograde diastolic flow ≥80% with respect to total diastolic FL flow were predictors of aortic events. In multivariate analysis, aortic diameter >45 mm (HR: 2.91), type B dissection (HR: 2.44), and MRI flow pattern (HR: 16.87) were independent predictors of AD-related events.

CONCLUSIONS

High systolic antegrade flow volume in the FL with significant diastolic retrograde flow assessed by MRI and aortic diameter >45 mm identify patients with higher risk for complications in whom more aggressive management would be indicated.

Risk profile analysis of uncomplicated type B aortic dissection patients undergoing thoracic endovascular aortic repair: Laboratory and radiographic predictors

BACKGROUND

There is emerging evidence to support pre-emptive thoracic endovascular aortic repair (TEVAR) intervention for uncomplicated type B aortic dissection (unTBAD). Pre-emptive intervention would be particularly beneficial in patients that have a higher baseline risk of progressing to complicated TBAD (coTBAD). There remain debate on the optimal clinical, laboratory, morphological, and radiological parameters, which would identify the highest-risk patients that would benefit most from pre-emptive TEVAR.

AIM

This review summarizes evidence on the clinical, laboratory, and morphological parameters that increase the risk profiles of unTBAD patients.

METHODS

A comprehensive literature search was carried out on multiple electronic databases including PubMed, EMBASE, Ovid, and Scopus to collate all research evidence on the clinical, laboratory, and morphological parameters that increase the risk profiles of unTBAD patients RESULTS: At present, there are no clear clinical guidelines using risk-stratification to inform the selection of unTBAD patients for TEVAR. However, there are noticeable literature trends that can assist with the identification of the most at-risk unTBAD patients. Patients are at particular risk when they have refractory pain and/or hypertension, elevated C-reactive protein (CRP), larger aortic diameter, and larger entry tears. These risks should be considered alongside factors that increase the procedural risk of TEVAR to create a well-balanced approach. Advances in biomarkers and imaging are likely to identify more pertinent parameters in the future to optimize the development of balanced, risk-stratified treatment protocols.

CONCLUSION

There are a variety of risk profiling parameters that can be used to identify the high-risk unTBAD patient, with novel biomarkers and imaging parameters emerging. Longer-term evidence verifying these parameters would be ideal. Further randomized controlled trials and multicentre registry analyses are also warranted to guide risk-stratified selection protocols.

Outer Media Thickness at False Lumen and Secondary Aortic Dilatation After Acute Aortic Dissection

BACKGROUND

This study measured the outer media thickness (OMT) at the false lumen by using microscopic images of specimens collected intraoperatively and assessed the impact of OMT on secondary dilatation of the downstream aorta.

METHODS

Of 238 patients undergoing surgical procedures for acute type A dissection between 2007 and 2016, 129 patients fulfilled the inclusion criteria for this study: DeBakey type I dissection with a patent false lumen, histopathologic examination of full-thickness aortic wall, and at least 1 follow-up computed tomographic scan at more than 3 months after surgical procedures. On average, 5.1 scans were obtained per patient, and median follow-up was 4.3 years.

RESULTS

Considerable variation was observed in OMT (median, 0.21 mm; range, 0.04-0.51 mm). The aortic diameter growth rate was inversely correlated with the OMT, and in the lowest tertile of OMT the aortic diameter dilated significantly faster in the first year than later and faster than in the other tertiles. Multivariable Fine-Gray analysis, with death as the competing risk, identified OMT as an independent variable for aortic-related events. Patients with OMT of 0.04 to 0.15 mm had a 3.54-fold higher risk of aortic-related events and those with 0.16 to 0.31 mm had a 1.56-fold higher risk of aortic-related events than did patients with OMT of 0.32 to 0.51 mm. Multivariable Cox regression analyses revealed OMT of 0.04 to 0.15 mm as an independent variable for all-cause mortality.

CONCLUSIONS

In patients with DeBakey type I aortic dissection with a patent false lumen, the growth rate of the distal residual dissecting aorta was inversely correlated with the OMT. The risk of aortic-related events was significantly higher in patients with OMT of 0.04 to 0.15 mm.

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.

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.

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.

Alternative management of proximal aortic dissection: concept and application

Open surgery remains the mainstay of treatment for acute type A aortic dissection and should be offered to most patients. However, there are elderly patients in which surgical treatment may be deemed extremely high risk or futile. Endovascular treatment approaches have been applied to a small number of these patients and data are limited to case reports and small series. The application of endovascular therapies to ascending aorta is currently limited by anatomical and technical challenges posed by the dynamic motion of the ascending aorta and the proximity of vital structures to intended landing zones (aortic valve, coronary arteries, and supra-aortic branches) and lack of specially designed endografts to address these issues. While thoracic endovascular aortic repair (TEVAR) has replaced open aortic repair for a suitable lesion in distal aortic dissection, some selected patients with type A aortic dissection at high surgical may be candidates. Hence, there is potential because, in proximal (Stanford type A) dissections, 10–30% of patients are not accepted for surgery, and 30–50% are technically amenable for TEVAR. Recent experience has shown that carefully selected patients with favorable anatomical characteristics may be subject to endovascular stent-graft treatment as a last resort with mixed results. Technical improvement is necessary to offer. satisfactory endovascular options in non-surgical candidates.

Obstructive Sleep Apnoea in Stanford Type B Aortic Dissection Is Associated With Multiple Imaging Signs Related to Late Aortic Events

Background: Obstructive sleep apnoea (OSA) is highly prevalent in patients with Stanford type B aortic dissection (TBAD). Few studies have evaluated the effects of OSA on vascular changes in TBAD patients. This study aimed to explore the effect of OSA on aortic morphological changes in TBAD patients and its relation to late aortic events (LAEs).

Methods: This case-control study included 143 TBAD patients. The diameters of different parts of the aorta were measured based on computed tomography angiography (CTA). According to the apnoea-hypopnoea index (AHI), OSA was classified as mild (5 ≤ AHI ≤ 15), moderate (15 < AHI ≤ 30), or severe (AHI > 30). The false lumen (FL) status was evaluated and classified as partially thrombosed, patent, or completely thrombosed.

Results: The OSA prevalence in TBAD patients was 64.3%, and image differences related to LAEs between TBAD patients with and without OSA included the maximum aortic diameter at onset (37.3 ± 3.9 vs. 40.3 ± 4.5 mm, p < 0.001), the FL diameter of the proximal descending thoracic aorta (16.0 ± 6.8 vs. 20.3 ± 4.7 mm, p < 0.001), and the proportion of the FL that was partially thrombosed (39.2 vs. 64.1%, p = 0.004). Additionally, in the multivariable analysis of patients with OSA, the risks of an aortic diameter ≥40 mm, a proximal descending aorta FL ≥ 22 mm and a partially thrombosed FL were 4.611 (95% CI: 1.796–11.838, p = 0.001), 2.544 (95% CI: 1.050–6.165, p = 0.039), and 2.565 (95% CI: 1.167–5.637, p = 0.019), respectively, after adjustment for confounding factors. Trend tests showed that the risks of an aortic diameter ≥40 mm and a partially thrombosed FL increased with increasing OSA severity.

Conclusions: TBAD patients with moderate to severe OSA have aortic dilatation in different parts of the aorta. OSA is an independent risk factor for multiple imaging signs related to LAEs, suggesting that OSA is an important factor affecting the prognosis of TBAD patients.

ACR Appropriateness Criteria® Suspected Acute Aortic Syndrome

Acute aortic syndrome (AAS) includes the entities of acute aortic dissection, intramural hematoma, and penetrating atherosclerotic ulcer. AAS typically presents with sudden onset of severe, tearing, anterior, or interscapular back pain. Symptoms may be dominated by malperfusion syndrome, due to obstruction of the lumen of the aorta and/or a side branch when the intimal and medial layers are separated. Timely diagnosis of AAS is crucial to permit prompt management; for example, early mortality rates are reported to be 1% to 2% per hour after the onset of symptoms for untreated ascending aortic dissection. The appropriateness assigned to each imaging procedure was based on the ability to obtain key information that is used to plan open surgical, endovascular, or medical therapy. This includes, but is not limited to, confirming the presence of AAS; classification; characterization of entry and reentry sites; false lumen patency; and branch vessel compromise. Using this approach, CT, CTA, and MRA are all considered usually appropriate in the initial evaluation of AAS if those procedures include intravenous contrast administration. Ultrasound is also considered usually appropriate if the acquisition is via a transesophageal approach. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

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.

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.

Predicting reintervention after thoracic endovascular aortic repair of Stanford type B aortic dissection using machine learning

OBJECTIVES

To construct models for predicting reintervention after thoracic endovascular aortic repair (TEVAR) of Stanford type B aortic dissection (TBAD).

METHODS

A total of 192 TBAD patients who underwent TEVAR were included; 68 (35.4%) had indications for reintervention. Clinical characteristics, aorta characteristics on pre- and postoperative computed tomography angiography, and aorta characteristics on immediate postoperative aortic digital subtraction angiography were collected. The least absolute shrinkage and selection operator (LASSO) regression was applied to identify the risk factors for reintervention. Eight classifiers were used for modeling. The models were trained on 100 train-validation random splits with a ratio of 2:1. The performance was evaluated by the receiver operating characteristic curve.

RESULTS

Seven predictors of reintervention were identified, including maximum false lumen diameter, aortic diameter measured at the level of approximately 15 mm distal to the left subclavian artery, aortic diameter measured at the level of the diaphragm, false lumen diameter measured at the level of the celiac artery, number of bare-metal and covered stents, number of bare-metal stents, and residual perfusion of the false lumen. Logistic regression (LR) yielded the highest performance, with an area under the curve of 0.802. A nomogram built for clinical use showed good calibration. The cutoff value for dividing patients into low- and high-risk subgroups was 0.413. Kaplan-Meier curves showed that the overall survival of high-risk patients was significantly shorter than that of low-risk patients (both p < 0.05).

CONCLUSION

Our nomogram could predict the reintervention after TEVAR in patients with TBAD, which may facilitate patient selection and surveillance strategies.

KEY POINTS

• Seven risk factors of reintervention after TEVAR of TBAD were identified for modeling. • Logistic regression performed best in predicting reintervention with an AUC of 0.802. • Patients with a high risk of reintervention had shorter OS than those with a low risk.

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.

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.

Aortic growth and development of partial false lumen thrombosis are associated with late adverse events in type B aortic dissection

BACKGROUND

Patients with medically treated type B aortic dissection (TBAD) remain at significant risk for late adverse events (LAEs). We hypothesize that not only initial morphological features, but also their change over time at follow-up are associated with LAEs.

MATERIALS AND METHODS

Baseline and 188 follow-up computed tomography (CT) scans with a median follow-up time of 4 years (range, 10 days to 12.7 years) of 47 patients with acute uncomplicated TBAD were retrospectively reviewed. Morphological features (n = 8) were quantified at baseline and each follow-up. Medical records were reviewed for LAEs, which were defined according to current guidelines. To assess the effects of changes of morphological features over time, the linear mixed effects models were combined with Cox proportional hazards regression for the time-to-event outcome using a joint modeling approach.

RESULTS

LAEs occurred in 21 of 47 patients at a median of 6.6 years (95% confidence interval [CI], 5.1-11.2 years). Among the 8 investigated morphological features, the following 3 features showed strong association with LAEs: increase in partial false lumen thrombosis area (hazard ratio [HR], 1.39; 95% CI, 1.18-1.66 per cm2 increase; P < .001), increase of major aortic diameter (HR, 1.24; 95% CI, 1.13-1.37 per mm increase; P < .001), and increase in the circumferential extent of false lumen (HR, 1.05; 95% CI, 1.01-1.10 per degree increase; P < .001).

CONCLUSIONS

In medically treated TBAD, increases in aortic diameter, new or increased partial false lumen thrombosis area, and increases of circumferential extent of the false lumen are strongly associated with LAEs.

Aortic Dissection and Other Acute Aortic Syndromes: Diagnostic Imaging Findings from Acute to Chronic Longitudinal Progression

Acute aortic dissection is the prototype of acute aortic syndromes (AASs), which include intramural hematoma, limited intimal tear, penetrating atherosclerotic ulcer, traumatic or iatrogenic aortic dissection, and leaking or ruptured aortic aneurysm. The manifestation is usually sudden and catastrophic with acutely severe tearing chest or back pain. However, clinical symptoms do not allow distinction between AAS types and other acute pathologic conditions. Diagnostic imaging is essential to rapidly confirm and accurately diagnose the type, magnitude, and complications of AASs. CT fast acquisition of volumetric datasets has become instrumental in diagnosis, surveillance, and intervention planning. Most critical findings affecting initial intervention and prognosis are obtained at CT, including involvement of the ascending aorta, primary intimal tear location, rupture, malperfusion, size and patency of the false lumen, complexity and extent of the dissection, maximum caliber of the aorta, and progression or postintervention complications. Involvement of the ascending aorta-Stanford type A-has the most rapid lethal complications and requires surgical intervention to affect its morbidity and mortality. Lesions not involving the ascending aorta-Stanford type B-have a lesser rate of complications in the acute phase. During the acute to longitudinal progression, various specific and nonspecific imaging findings are encountered, including pleural and pericardial effusions, fluid collections, progression including aortic enlargement, and postoperative changes that can be discerned at CT. A systematic analysis algorithm is proposed for CT of the entire aorta throughout the continuum of AASs into the chronic and posttreated disease state, which synthesizes and communicates salient findings to all care providers. Online supplemental material is available for this article. ^©RSNA, 2021.

3D Morphologic Findings Before and After Thoracic Endovascular Aortic Repair for Type B Aortic Dissection

BACKGROUND

Stanford type-B aortic dissection (TBAD) is commonly treated by thoracic endovascular aortic repair (TEVAR). Usually, the implanted stent-grafts will not cover the entire dissection-affected region for those patients with dissection extending beyond the thoracic aorta, thus the fate of the uncovered aortic segment is uncertain. This study used 3-dimensional measurement of aortic morphological changes to classify the different remodeling effects of TBAD patients after TEVAR, and hypothesized that not only initial morphological features, but also their change over time at follow-up are associated with the remodeling.

METHODS

Forty-one TBAD patients underwent TEVAR and CT-angiography before and after the intervention (twice or more follow-ups) were included in this study. According to the false-lumen volume variations post-TEVAR, patients who had abdominal aortic expansion at the second follow-up were classified into the Enlarged (n =12, 29%) and remaining into the Stable group (n = 29, 71%). 3D morphological parameters were extracted on precise reconstruction of imaging datasets. Statistical differences in 3D morphological parameters over time between the 2 groups and the relationship among these parameters were analyzed.

RESULTS

In the Enlarged group, the number of all tears before TEVAR was significantly higher (P = 0.022), and the size of all tears at the first and second follow-up post-TEVAR were significantly higher than that in the Stable group (P = 0.008 and P = 0.007). The location of the primary tear was significantly higher (P = 0.031) in the Stable group. The cross-sectional analysis of several slices below the primary tear before TEVAR shows different shape features of the false lumen in the Stable (cone-like) and Enlarged (hourglass-like) groups. The number of tears before TEVAR has a positive correlation with the post-TEVAR development of dissection (r = 0.683, P = 0.00).

CONCLUSION

The results in this study indicated that the TBAD patients with larger tear areas, more re-entry tears and with the primary tear proximal to the arch would face a higher risk of negative remodeling after TEVAR.

Quantification of true lumen helical morphology and chirality in type B aortic dissections

Chirality is a fundamental property in many biological systems. Motivated by previous observations of helical aortic blood flow, aortic tissue fibers, and propagation of aortic dissections, we introduce methods to characterize helical morphology of aortic dissections. After validation on computer-generated phantoms, the methods were applied to patients with type B dissection. For this cohort, there was a distinct bimodal distribution of helical propagation of the dissection with either achiral or exclusively right-handed chirality, with no intermediate cases or left-handed cases. This clear grouping indicates that dissection propagation favors these two modes, which is potentially due to the right-handedness of helical aortic blood flow and cell orientation. The characterization of dissection chirality and quantification of helical morphology advances our understanding of dissection pathology and lays a foundation for applications in clinical research and treatment practice. For example, the chirality and magnitude of helical metrics of dissections may indicate risk of dissection progression, help define treatment and surveillance strategies, and enable development of novel devices that account for various helical morphologies.NEW & NOTEWORTHY A novel definition of helical propagation of type B aortic dissections reveals a distinct bimodality, with the true lumen being either achiral (nonhelical) or exclusively right-handed. This right-handed chirality is consistent with anatomic and physiological phenomena such as right-handed twist during left ventricle contraction, helical blood flow, and tissue fiber direction. The helical character of aortic dissections may be useful for pathology research, diagnostics, treatment selection, therapeutic durability prediction, and aortic device design.

Predictive Factors of Operative Need in Medically Managed Type B Aortic Dissections

BACKGROUND

Aneurysmal degeneration of medically managed type B aortic dissection (TBAD) can be a life-threatening condition. Preventive thoracic endovascular aorta repair (TEVAR) in patients at risk could potentially be beneficial. The aim of this study was to examine the predictors for late aneurysmal dilatation after TBAD.

METHODS

A retrospective study was conducted on 82 patients with medically managed acute TBAD for a minimum of 14 days. Relevant demographic, biochemical, and radiographic variables at presentation were studied. The aortic dissection risk calculator tool developed by Sailer et al., predicting the risk of adverse events after aortic dissection based on demographic and radiographic variables at presentation, was tested retrospectively.

RESULTS

With a median follow-up of 36 months (range 13-68), 25 (30.5%) patients underwent surgery (92% TEVAR). A larger initial aortic and false lumen diameter as well as a greater distal extension of the dissection was associated with higher need for surgery (respectively, P = 0.003, P = 0.004, and P = 0.001). We observed higher growth rates of maximum aortic diameter in patients with a greater distal extension of the dissection, larger false lumen diameters and false lumen outflow, and entry tears located at the inner aortic arch (respectively, P = 0.001, P = 0.005, P = 0.001 and P = 0.014). No significant correlations could be found for the risks provided by the calculator tool.

CONCLUSIONS

The initial maximum aortic diameter of TBAD is a key predictor for aortic growth. Furthermore, the distal extension of the dissection also seems to play an important role in late aneurysmal degeneration. However, we were not able to confirm the added value of the risk calculator tool in our study group.