The Role of False Lumen Size in Prediction of In-Hospital Complications After Acute Type B Aortic Dissection

The Role of Location, Length, and Thickness of the Intimal Flap in the Propagation of Stanford Type B Aortic Dissection Based on Ex Vivo Porcine Aorta Models

PURPOSE

To explore the role of location, length, and thickness of the intimal flap in the propagation of Stanford type B aortic dissection (TBAD) based on ex vivo porcine aorta models based on ex vivo porcine aorta models.

MATERIALS AND METHODS

The porcine aortas were harvested and randomly divided into 6 groups to create various TBAD aortic models. We constructed intimal flaps for different locations (group A [entry tear on outer curvature] and group B [entry tear on inner curvature]), lengths (group C [long] and group D [short]), and thicknesses (group E [thick] and group F [thin]). For the ex vivo perfusion experiments conducted on model aortas, an experimental circulation loop (ECL) was employed. The pressure in false lumen (FL) was constantly monitored. A comparison was made between the morphological data collected before and after the experiment to quantify the changes in the FL after the experiment.

RESULTS

Compared the results with group B, the mean peak pressures of the FL in group A were lower (106.87±15.55 vs. 124.01±22.75 mm Hg, p=0.028). The mean axial propagation length in group A was shown to be shorter than that of group B (88.14±33.38 vs. 197.43±41.65 mm, p<0.001). The mean peak pressure was higher in group C than in group D (144.04±19.37 vs. 92.51±26.70 mm Hg, p<0.001). The mean peak pressure of group E was higher than that of group F (160.83±32.83 vs. 109.33±15.62 mm Hg, p<0.001), as was the mean axial propagation length of group E (143.11±39.73 vs. 100.45±35.44 mm, p=0.021). According to the results of multivariable linear regression, axial propagation length=45.873-0.703×length of initial FL+0.863× peak pressure (p<0.001).

CONCLUSION

There was a relationship between FL propagation and the location, length, and thickness of the intimal flap. The axial propagation length was related to the length of the intimal flap and the peak pressure of propagation. It may be helpful to evaluate the risk of propagation in patients with TBAD.

CLINICAL IMPACT

This study found that the locations, lengths, and thickness of the intimal flap significantly contributed to propagation pressure of FL. Using dissection flap characteristics, a physician can predict FL development in a patient and formulate a treatment plan.The purpose was to investigate the relationship between the dissection flap characteristics (location, length, and thickness) and the propagation of the FL, which is not clear at present. This study employed porcine models to create an experimental circulation loop. The perfusion experiment was conducted using a FL without distal re-entry and a non-pulsating flow.

Uncomplicated Type B Aortic Dissection: Challenges in Diagnosis and Categorisation

BACKGROUND

Acute type B aortic dissection (TBAD) is a rare disease that is likely under-diagnosed in the UK. As a progressive, dynamic clinical entity, many patients initially diagnosed with uncomplicated TBAD deteriorate, developing end-organ malperfusion and aortic rupture (complicated TBAD). An evaluation of the binary approach to the diagnosis and categorisation of TBAD is needed.

METHODS

A narrative review of the risk factors predisposing patients to progression from unTBAD to coTBAD was undertaken.

RESULTS

Key high-risk features predispose the development of complicated TBAD, such as maximal aortic diameter > 40 mm and partial false lumen thrombosis.

CONCLUSION

An appreciation of the factors that predispose to complicated TBAD would aid clinical decision-making surrounding TBAD.

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.

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.

Relationship of acute type A aortic dissection and disseminated intravascular coagulation

OBJECTIVE

Acute type A aortic dissection (ATAAD) is a critical disease presenting with disseminated intravascular coagulation (DIC). However, the relationship between the degree of DIC and false lumen conditions remains unclear. In the present study, we evaluated the degree of preoperative DIC and the outcomes of ATAAD treatment.

METHODS

A total of 124 patients with ATAAD (70 men and 54 women) treated from January 2012 to January 2020 were included in the present study. The correlation between the preoperative Japanese Association for Acute Medicine (JAAM) DIC score and the false lumen diameter and length, measured using preoperative computed tomography, was examined retrospectively. The correlations were calculated using liner regression analysis. The level of statistical significance was set at P < .05.

RESULTS

The patients were divided into two groups: a low JAAM DIC score group and a high JAAM DIC score group. The preoperative JAAM DIC scores in the high- and low-score groups were 4.8 ± 1.2 and 1.7 ± 2.3, respectively (P < .001). The 5-year survival rates and aortic event-free rates in the low-score group were favorable compared with the high-score group; however, the differences were not statistically significant (80.8% vs 54.5%, P = .065; 63.9% vs 59.8%, P = .15, respectively). The false lumen diameter in the ascending aorta was greater in the high-score group than that in the low-score group (P < .05). The JAAM DIC score correlated significantly with the ascending false lumen diameter and the dissection length (r = 0.32 and P < .001; r = 0.29 and P = .001, respectively). A high JAAM DIC score was associated with communicating-type ATAAD (P < .05).

CONCLUSIONS

Our results suggest that high preoperative JAAM DIC scores are associated with a large false lumen and communicating-type ATAAD.

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.

Association of hemodynamic factors and progressive aortic dilatation following type A aortic dissection surgical repair

Type A aortic dissection (TAAD) involves the ascending aorta or the arch. Acute TAAD usually requires urgent replacement of the ascending aorta. However, a subset of these patients develops aortic rupture due to further dilatation of the residual dissected aorta. There is currently no reliable means to predict the risk of dilatation following TAAD repair. In this study, we performed a comprehensive morphological and hemodynamic analysis for patients with and without progressive aortic dilatation following surgical replacement of the ascending aorta. Patient-specific models of repaired TAAD were reconstructed from post-surgery computed tomography images for detailed computational fluid dynamic analysis. Geometric and hemodynamic parameters were evaluated and compared between patients with stable aortic diameters (N = 9) and those with aortic dilatation (N = 8). Our results showed that the number of re-entry tears and true/false lumen pressure difference were significantly different between the two groups. Patients with progressive aortic dilatation had higher luminal pressure difference (6.7 [4.6, 10.9] vs. 0.9 [0.5, 2.3] mmHg; P = 0.001) and fewer re-entry tears (1.5 [1, 2.8] vs. 5 [3.3, 7.5]; P = 0.02) compared to patients with stable aortic diameters, suggesting that these factors may serve as potential predictors of aneurysmal dilatation following surgical repair of TAAD.

Distal Extended Endovascular Aortic Repair PETTICOAT: A Modified Technique to Improve False Lumen Remodeling in Acute Type B Aortic Dissection

BACKGROUND

Data from the literature suggest that in patients with acute, complicated type B aortic dissection (cTBAD), initial successful treatment with thoracic endovascular aneurysm repair (TEVAR) is not necessarily associated with favorable remodeling of the dissected aorta during follow-up, and long-term results indicate that TEVAR failed to completely suppress false lumen patency. Sealing of all relevant distal reentries, infrarenal and/or iliac, seems to be the key issue to induce total false lumen thrombosis in abdominal aorta as well as the iliac arteries, especially in complicated patients presenting with malperfusion or complete true lumen collapse.

MATERIALS AND METHODS

Of the 34 consecutive patients diagnosed with cTBAD at our hospital from January 2015 to April 2018, 30 had complicated dissections receiving endovascular treatment according to the standard Provisional ExTension To Induce COmplete ATtachment (PETTICOAT) technique and were excluded from this study, whereas 4 patients with radiologic evidence of multiple reentry tears at detached lumbar arteries and iliac bifurcation with complete true lumen collapse and clinical evidence of malperfusion were treated with a modified PETTICOAT technique with distal extension of the aortic stent, balloon expansion of the stented true lumen, and use of the AFX bifurcated endograft system to preserve the natural aortic bifurcation and provide complete distal sealing of reentry tears.

RESULTS

Primary technical success was achieved in all patients. No postoperative deaths were observed, but 1 patient experienced an hemorrhagic shock on the second postoperative day. No patient suffered postoperative stroke, paraplegia, paraparesis, or acute renal failure.

CONCLUSIONS

Using an abdominal aortic bifurcated endograft with PETTICOAT to treat acute cTBAD seems to be a feasible approach in high-risk patients to improve aortic remodeling. The AFX bifurcated endograft system meets the requirements of anatomical fixation and sealing of distal tears.

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

OBJECTIVES

Acute type B aortic dissection can have a stable course or evolve into aneurysm and subsequent adverse events. The aim of this systematic review was to analyze the morphologic predictors of an adverse course to establish their validity based on consistency of results.

METHODS

Fifty-one studies were included in this review, reporting on aortic size, false lumen (FL) size, primary entry tear (ET) size and location, status of FL thrombosis, number of ETs, branch vessels involvement, and FL longitudinal extent.

RESULTS

Some predictors showed good consistency, whereas others did not. Aortic size was the most investigated predictor. A larger diameter at presentation predicted worse outcomes, with few exceptions. Both FL size and size relative to true lumen size also predicted an adverse course, although a standardized measurement method was not used. Regarding primary ET size and location, evidence was sparse and somewhat conflicting. Although FL complete thrombosis was consistently associated with a more benign course, the role of partial thrombosis remained unclear and the concept of FL saccular formation might account for the inconsistency, but further evidence is needed. A higher number of re-entry tears was considered to be protective against false channel expansion, but results need to be confirmed. The predictive role of branch vessels involvement and FL longitudinal extent remain controversial.

CONCLUSIONS

Among several predictors of aortic growth and events in acute type B aortic dissection, controversial and even conflicting results have been described. Consistent evidence has been demonstrated only for two predictors: aortic size at presentation is associated with adverse events and total FL thrombosis has a protective role.

Temporal and Morphological Patterns Predict Outcome of Endovascular Repair in Acute Complicated Type B Aortic Dissection

OBJECTIVES

The aim was to analyse early and late outcomes in patients undergoing thoracic endovascular aortic repair (TEVAR) for acute or subacute non-traumatic type B aortic dissection (TBAD), with the particular aims of identifying prognostic morphological predictors, and to assess the magnitude of the impact of the timing of TEVAR.

METHODS

This was a retrospective, two centre, population based consecutive case series. The study group consisted of all the 53 patients undergoing TEVAR for complicated TBAD in Stockholm during the 12 year period 2004-2015. Demographic data, risk factors, operative, and outcome variables were registered and analysed. The CT scans were thoroughly retrospectively examined.

RESULTS

Nearly half (24 patients; 45%) underwent TEVAR within 48 h of the onset of the initial symptoms, another 20 within 2 weeks, and nine in the subacute phase (15-90 days). The median age was 63 years (range 32-88) and 20 patients (38%) were women. The 30 day mortality was 17% (nine patients). Eight of these nine patients were treated within the first 48 h; urgent intervention (0-48 h) was associated with increased mortality (crude OR 14.0; 95% CI 1.6-122). All the nine patients had a false lumen area (FLA) at the level of the tracheal bifurcation exceeding 50% of the aortic cross sectional area at that segment, a finding significantly associated with increased mortality (p = .04), with a 25% 30 day mortality if the FLA > 50% (n = 36) at that segment, but 0% if the FLA was <50%. Overall the one year survival was 79% and five year survival 65%.

CONCLUSIONS

All the early deaths demonstrated a FLA >50% of the total aortic cross sectional area at the level of the tracheal bifurcation. Patients needing urgent TEVAR had markedly worse outcome. The first finding may become an additional tool for future risk stratification.

Early and midterm outcomes of thoracic endovascular aortic repair (TEVAR) for acute and chronic complicated type B aortic dissection

Thoracic endovascular aortic repair (TEVAR) in the current era has been chosen as a dominant and minimally invasive treatment for complicated aorta dissection. This study aimed to assess safety and feasibility of TEVAR in acute and chronic type B aortic dissection.Between January 2011 and December 2013, 85 patients with complicated type B aortic dissection undergoing TEVAR were divided into acute aortic dissection (AAD) (n = 60) group and chronic aortic dissection (CAD) group (n = 25). Computed tomography was used to evaluate postoperative changes in maximal aortic diameter and true and false lumen diameters at 3 levels during a mean follow-up period of 26.4 ± 15.6 months.The technical success rate was 100%. In-hospital and 30-day rates of death were 3.3% in acute group and 0 in chronic group. Postdischarge rates of type I leak, type II leak, and retrograde type A dissection were 6.7%, 5.2%, and 3.4% (acute) and 0%, 4.0%, and 4.0% (chronic), respectively. The maximal aorta diameter remained stable in all the 3 levels in both acute and chronic group. The cumulative freedom from all-cause mortality at 3 years was similar in acute and chronic groups (89.5% vs 95.5%, P = .308). The cumulative freedom from aortic-related mortality was also not significantly different in the acute and chronic groups (92.8% vs 95.2%, P = .531). In the thoracic aorta, TEVAR treatment resulted in a significant increase in true lumen (TL) diameter and decrease in false lumen (FL). However, in the abdominal aorta, TEVAR did not lead to significant change in TL and FL diameters. The rates of complete thrombosis thoracic false lumens were better than that in the abdominal false lumen.TEVAR was a safe and effect therapy for complicated acute and chronic type B dissection with low early and mid-term mortality and morbidity.

Endovascular management of chronic symptomatic aortic dissection with the Streamliner Multilayer Flow Modulator: Twelve-month outcomes from the global registry

OBJECTIVE

Reported are initial 12-month outcomes of patients with chronic symptomatic aortic dissection managed by the Streamliner Multilayer Flow Modulator (SMFM; Cardiatis, Isnes, Belgium). Primary end points were freedom from rupture- and aortic-related death, and reduction in false lumen index. Secondary end points were patency of great vessels and visceral branches, and freedom of stroke, paraplegia, and renal failure.

METHODS

Out of 876 SMFM implanted globally, we have knowledge of 542. To date, 312 patients are maintained in the global registry, of which 38 patients were identified as having an aortic dissection (12.2%). Indications included 35 Stanford type B dissections, two Stanford type A and B dissections, and one mycotic Stanford type B dissection.

RESULTS

There were no reported ruptures or aortic-related deaths. All cause survival was 85.3% Twelve-month freedom from neurologic events was 100%, and there were no incidences of end-organ ischemia, paraplegia or renal insult. Morphologic analysis exhibited dissection remodeling by a reduction in longitudinal length of the dissected aorta, and false lumen volume. A statistically significant reduction in false lumen index (P = .016) at 12 months, and a borderline significant increase in true lumen volume (P = .053) confirmed dissection remodeling.

CONCLUSIONS

The SMFM is an option in management of complex pan-aortic dissection. Results highlight SMFM implantation leads to dissection stabilization with no further aneurysm progression, and no retrograde type A dissection. Thoracic endovascular aneurysm repair by SMFM ensued in freedom from aortic rupture, neurologic stroke, paraplegia and renal failure. Further analysis of the global registry data will inform long-term outcomes.

Use of computational fluid dynamics studies in predicting aneurysmal degeneration of acute type B aortic dissections

OBJECTIVE

Whereas uncomplicated acute type B aortic dissections are often medically managed with good outcomes, a subset develop subacute or chronic aneurysmal dilation. We hypothesized that computational fluid dynamics (CFD) simulations may be useful in identifying patients at risk for this complication.

METHODS

Patients with acute type B dissection complicated by rapidly expanding aortic aneurysms (N = 7) were compared with patients with stable aortic diameters (N = 7). Three-dimensional patient-specific dissection geometries were generated from computed tomography angiography and used in CFD simulations of pulsatile blood flow. Hemodynamic parameters including false lumen flow and wall shear stress were compared.

RESULTS

Patients with rapid aneurysmal degeneration had a growth rate of 5.3 ± 2.7 mm/mo compared with those with stable aortic diameters, who had rates of 0.2 ± 0.02 mm/mo. Groups did not differ in initial aortic diameter (36.1 ± 2.9 vs 34.4 ± 3.6 mm; P = .122) or false lumen size (22.6 ± 2.9 vs 20.2 ± 4.5 mm; P = .224). In patients with rapidly expanding aneurysms, a greater percentage of total flow passed through the false lumen (78.3% ± 9.3% vs 56.3% ± 11.8%; P = .016). The time-averaged wall shear stress on the aortic wall was also significantly higher (12.6 ± 3.7 vs 7.4 ± 2.8 Pa; P = .028).

CONCLUSIONS

Hemodynamic parameters derived from CFD simulations of acute type B aortic dissections were significantly different in dissections complicated by aneurysm formation. Thus, CFD may assist in predicting which patients may benefit from early stent grafting.

Type B Aortic Dissection: A Review of Prognostic Factors and Meta-analysis of Treatment Options

According to international guidelines, stable patients with uncomplicated Type B aortic dissection (TBAD) should receive optimal medical treatment. Despite adequate antihypertensive therapy, the long-term prognosis of these patients is characterized by a significant aortic aneurysm formation in 25-30% within four years, and survival rates from 50 to 80% at five years and 30 to 60% at 10 years. In a prospective randomized trial, preemptive thoracic endovascular aortic repair (TEVAR) in patients with chronic uncomplicated TBAD was associated with an excess early mortality (due to periprocedural hazards), but the procedure showed its benefit in prevention of aortic-specific mortality at five years of follow-up. However, preemptive TEVAR may not be the treatment of choice in all patients with uncomplicated TBAD because of the inherent periprocedural complications like stroke, paraparesis, and death, as well as stent graft-induced complications (i.e., retrograde dissection or endoleaks). Thus, the TEVAR-related deaths and complications (especially paraplegia and stroke) raise concerns that moderate the better survival with TEVAR at five years. By timely identification of those patients prone for developing complications, early intervention, preferably in the subacute or early chronic phase, may improve the overall long-term outcome for these patients. Therefore, early detectable and reliable prognostic factors for adverse events are essential to stratify patients who can be treated medically and those who will benefit from rigorous follow-up and, in the long-term, from timely, or even prophylactic, TEVAR. Several studies have identified prognostic factors in TBAD such as aortic diameter, partial false lumen thrombosis, false lumen thickness, and location of the primary entry tear. Combining these clinical and radiological predictors may be essential to implement a patient-specific approach designed to intervene only in those patients who are at high risk of developing complications to improve the long-term outcomes of patients with uncomplicated Type B aortic dissection.

Prognostic factors in patients with uncomplicated acute type B aortic dissection

BACKGROUND

The benefit of thoracic endovascular aortic repair (TEVAR) for uncomplicated acute type B aortic dissection is unclear. Reliable prognostic factors are needed to identify candidates for prophylactic TEVAR. The aim of this study was to detect prognostic factors in patients with uncomplicated acute type B aortic dissection.

METHODS

From January 2003 to April 2012, a total of 228 patients with uncomplicated acute type B aortic dissection were admitted to our institute. Cox proportional hazards analysis was performed to identify risk factors for death, dissection-related death, and aortic events.

RESULTS

Independent predictors of mortality were age (hazard ratio [HR], 1.08; p < 0.001) and false lumen thickness (mm) (HR, 1.10; p = 0.013), and the risk factor for dissection-related death was false lumen thickness (mm) (HR, 1.14; p < 0.001). Independent risk factors for aortic events were diameter of the descending aorta (mm) (HR, 1.14; p < 0.001) and entry in a proximal site (HR, 2.90; p = 0.02). The actuarial freedom from aortic events in patients with a descending aortic diameter of less than 40 mm and no entry in a proximal site at 1, 3, and 5 years was 96.6%, 90.8%, and 82.5%, respectively, whereas in patients with 1 of these 2 factors, it was 80.1%, 66.8%, and 53.5%, respectively.

CONCLUSIONS

In uncomplicated acute type B aortic dissection, the diameter of the descending aorta and entry in a proximal site were independent prognostic factors for aortic events. Prophylactic TEVAR should be considered for patients with these risk factors.

TEVAR for type B aortic dissection in Japan

TEVAR is a new strategy for treating both acute and chronic type B aortic dissection. The JSC guidelines classify TEVAR as a Class I recommendation for cases of complicated acute type B dissection and a Class IIa recommendation for cases of chronic type B aortic dissection. While TEVAR has been primarily applied to treat complicated acute type B aortic dissection in Europe and the USA, the procedure remains an off-label treatment strategy for aortic dissection in Japan. The current state of TEVAR for type B aortic dissection in Japan from 2001 to 2011 is estimated in the annual reports of the Japanese Association for Thoracic Surgery. The number of acute type B aortic dissection patients treated with transluminal stent grafting increased rapidly after 2008, from 10 cases in 2001 to 76 cases in 2010. Meanwhile, the number acute type B aortic dissection patients treated with any type of surgery has increased gradually, from 100 cases in 2001 to 194 cases in 2009. The number of chronic type B aortic dissection patients treated with transluminal stent grafting increased abruptly in 2010, reaching 346 cases, which accounted for one-third of all surgical procedures for chronic type B aortic dissection. Furthermore, the number of open surgeries for chronic type B aortic dissection has also increased gradually, from 401 cases in 2001 to 947 cases in 2011. At present, open surgery, TEVAR and hybrid procedures are available to treat patients with type B aortic dissection. The use of a multidisciplinary team approach is mandatory when selecting the appropriate surgical strategy.

Acute aortic emergencies--part 2: aortic dissections

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