Predictors of Failure of Medical Management in Uncomplicated Type B Aortic Dissection

The role of anatomic shape features in the prognosis of uncomplicated type B aortic dissection initially treated with optimal medical therapy

OBJECTIVE

Currently, the long-term outcomes of uncomplicated type B aortic dissection (TBAD) patients managed with optimal medical therapy (OMT) remain poor. Aortic expansion is a major factor that determines patient long-term survival. The objective of this study was to investigate the association between anatomic shape features and (i) OMT outcome; (ii) aortic growth rate for TBAD patients initially treated with OMT.

METHODS

108 CT images of TBAD in the acute and chronic phases were collected from 46 patients who were initially treated with OMT. Statistical shape models (SSM) of TBAD were constructed to extract shape features from the earliest initial CT scans of each patient by using principal component analysis (PCA) and partial least square (PLS) regression. Additionally, conventional shape features (e.g., aortic diameter) were quantified from the earliest CT scans as a baseline for comparison. We identified conventional and SSM features that were significant in separating OMT "success" and failure patients. Moreover, the aortic growth rate was predicted by SSM and conventional features using linear and nonlinear regression with cross-validations.

RESULTS

Size-related SSM and conventional features (mean aortic diameter: p=0.0484, centerline length: p=0.0112, PCA score c1: p=0.0192, and PLS scores t1: p=0.0004, t2: p=0.0274) were significantly different between OMT success and failure groups, but these features were incapable of predicting the aortic growth rate. SSM shape features showed superior results in growth rate prediction compared to conventional features. Using multiple linear regression, the conventional, PCA, and PLS shape features resulted in root mean square errors (RMSE) of 1.23, 0.85, and 0.84 mm/year, respectively, in leave-one-out cross-validations. Nonlinear support vector regression (SVR) led to improved RMSE of 0.99, 0.54, and 0.43 mm/year, for the conventional, PCA, and PLS features, respectively.

CONCLUSION

Size-related shape features of the earliest scan were correlated with OMT failure but led to large errors in the prediction of the aortic growth rate. SSM features in combination with nonlinear regression could be a promising avenue to predict the aortic growth rate.

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.

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.

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.

Management of Acute, Uncomplicated Type B Aortic Dissection

For decades, the mainstay of management for acute, uncomplicated type B aortic dissection (TBAD) has been anti-impulse medical therapy, focusing on close control of blood pressure, and heart rate. However, the natural history of this entity has remained one of aortic degeneration over time and significant morbidity and mortality. More recently, the advent of endovascular therapy has driven a revolution in the management of TBAD. While thoracic endovascular aortic repair (TEVAR) was rapidly adopted for the treatment of complicated type B aortic dissection due to significantly improved morbidity and mortality when compared with tradition open surgical techniques, its role in the management of uncomplicated dissection remained controversial. However, the accumulation of favorable data on aortic remodeling and survival following early TEVAR for uncomplicated dissection is driving a shift in paradigm and practice. This is particularly true of patients exhibiting certain features at the time of presentation that are associated with increased risk of failure of optimal medical therapy. This article reviews the current evidence in the literature addressing TEVAR for acute, uncomplicated TBAD. In addition, it presents the state of the art in FDA-approved thoracic endograft platforms, guidance regarding case planning, and step-by-step procedural description, including the management of common challenges, and complications.

Cause-specific mortality of type B aortic dissection and assessment of competing risks of mortality

OBJECTIVE

Natural history studies of type B aortic dissection (TBAD) commonly report all-cause mortality. Our aim was to determine cause-specific mortality in TBAD and to evaluate the clinical characteristics associated with aorta-related and nonaorta-related mortality.

METHODS

Clinical and administrative records were reviewed for patients with acute TBAD between 1995 and 2017. Demographics, comorbidities, presentation, and initial imaging findings were abstracted. Cause of death was ascertained through a multimodality approach using electronic health records, obituaries, social media, Social Security Death Index, and state mortality records. Causes of death were classified as aorta related, nonaorta related, or unknown. A Fine-Gray multivariate competing risk regression model for subdistribution hazard ratio was employed to analyze the association of clinical characteristics with aorta-related and nonaorta-related mortality.

RESULTS

A total of 275 individuals met inclusion criteria (61.1 ± 13.7 years, 70.9% male, 68% white). Mean survival after discharge was 6.3 ± 4.7 years. Completeness of follow-up Clark C index was 0.87. All-cause mortality was 50.2% (n = 138; mean age, 70.1 ± 14.6 years) including an in-hospital mortality of 8.4%. Cause-specific mortality was aorta related, nonaorta related, and unknown in 51%, 43%, and 6%, respectively. Compared with patients with nonaorta-related mortality, patients with aorta-related mortality were younger at acute TBAD (69.5 ± 11.2 years vs 61.6 ± 15.5 years; P = .001), underwent more descending thoracic aortic repairs (19.4% vs 45.8%; P = .002), and had a shorter survival duration (5.7 ± 3.9 vs 3.4 ± 4.5 years; P = .002). There was clear variation in cause of death by each decade of life, with higher aorta-related mortality among those younger than 50 years and older than 70 years and a stepwise increase in nonaorta-related mortality with each increasing decade (P < .001). All-cause mortality at 1 year, 3 years, and 10 years was 15%, 24%, and 57%, respectively. After accounting for competing risks, the cumulative incidence of aorta-related mortality at 1 year, 3 years, and 10 years was 8.9%, 16.5%, and 27.2%, respectively, and that of nonaorta-related mortality was 2.7%, 7.2%, and 29%, respectively. A maximum descending thoracic aortic diameter >4 cm was associated with an increase in hazard of aorta-related mortality by 84% (subdistribution hazard ratio, 1.84; 95% confidence interval, 1.03-3.28) on multivariate competing risk regression analysis.

CONCLUSIONS

TBAD is associated with high 10-year mortality. Those at risk for aorta-related mortality have a clinical phenotype different from that of individuals at risk for nonaorta-related mortality. This information is important for building risk prediction models that account for competing mortality risks and to direct optimal and individualized surgical and medical management of TBAD.

Pre-emptive thoracic endovascular aortic repair is unnecessary in extended type A (DeBakey type I) aortic dissections

OBJECTIVE

Pre-emptive thoracic endovascular aortic repair (TEVAR) improves late survival and limits progression of disease after type B aortic dissection, but the potential value of pre-emptive TEVAR has not been evaluated after type A dissection extending beyond the aortic arch (DeBakey type I). The purpose of this study was to compare disease progression and need for aortic intervention in survivors of acute, extended type A (ExTA) dissections after initial repair of the ascending aorta versus acute type B aortic dissections.

METHODS

Consecutive patients presenting with ExTA or type B dissections between 2011 and 2018 were studied. Forty-three patients with ExTA and 44 with type B dissections who survived to discharge and had follow-up imaging studies were included in the analysis. Study end points included progression of aortic disease (>5 mm growth or extension), need for intervention, and death.

RESULTS

The groups were not different for age, sex, atherosclerotic risk factors, or extent of dissection distal to the left subclavian artery. Following emergent ascending aortic repair, five ExTA patients (12%) underwent TEVAR within 4 months after discharge. Despite optimal medical treatment, 29 type B patients (66%) underwent early or late TEVAR (P < .001). During a mean follow-up of 38 ± 30 months, 38 ExTA patients (88%) did not require intervention-23 (53%) of whom showed no disease progression. In comparison, during a mean follow-up of 18 ± 6 months, 14 type B patients (32%) did not require intervention-nine (20%) of whom showed no disease progression (P = .003). There was one aortic-related late death in the ExTA group and two in the type B group. Compared with ExTA patients, type B patients had significantly worse intervention-free survival and intervention/growth-free survival (log rank, P < .001).

CONCLUSIONS

In contrast with type B dissections, these midterm results demonstrate that one-half of ExTA aortic dissections show no disease progression in the thoracic or abdominal aorta, and few require additional interventions. After initial repair of the ascending aorta, pre-emptive TEVAR does not seem to be justified in patients with acute, ExTA dissections.

Left ventricular assist device implant and subsequent orthotopic heart transplant after chronic type B aortic dissection

The criteria for being placed on the list of the International Society for Heart and Lung Transplantation for an orthotopic heart transplant mention nothing about patients with aortic dissection. Nor are there any guidelines pertaining to the patient with type B aortic dissection. Herein, we report the case of a patient with chronic type B aortic dissection for whom we successfully performed a left ventricular assist device implant followed by an orthotopic heart transplant.