Conservative management versus endovascular or open surgery in the spectrum of type B aortic dissection

Patient-specific compliant simulation framework informed by 4DMRI-extracted pulse wave Velocity: Application post-TEVAR

We introduce a new computational framework that utilises Pulse Wave Velocity (PWV) extracted directly from 4D flow MRI (4DMRI) to inform patient-specific compliant computational fluid dynamics (CFD) simulations of a Type-B aortic dissection (TBAD), post-thoracic endovascular aortic repair (TEVAR). The thoracic aortic geometry, a 3D inlet velocity profile (IVP) and dynamic outlet boundary conditions are derived from 4DMRI and brachial pressure patient data. A moving boundary method (MBM) is applied to simulate aortic wall displacement. The aortic wall stiffness is estimated through two methods: one relying on area-based distensibility and the other utilising regional pulse wave velocity (RPWV) distensibility, further fine-tuned to align with in vivo values. Predicted pressures and outlet flow rates were within 2.3 % of target values. RPWV-based simulations were more accurate in replicating in vivo hemodynamics than the area-based ones. RPWVs were closely predicted in most regions, except the endograft. Systolic flow reversal ratios (SFRR) were accurately captured, while differences above 60 % in in-plane rotational flow (IRF) between the simulations were observed. Significant disparities in predicted wall shear stress (WSS)-based indices were observed between the two approaches, especially the endothelial cell activation potential (ECAP). At the isthmus, the RPWV-driven simulation indicated a mean ECAP>1.4 Pa-1 (critical threshold), indicating areas potentially prone to thrombosis, not captured by the area-based simulation. RPWV-driven simulation results agree well with 4DMRI measurements, validating the proposed pipeline and facilitating a comprehensive assessment of surgical decision-making scenarios and potential complications, such as thrombosis and aortic growth.

Hidden in Plain Sight: Deciphering Chest Pain, Hypertension, and Elevated Creatinine to Unveil Aortic Dissection

Chest pain is a common yet complex presentation in the emergency department, often requiring the exclusion of life-threatening conditions such as aortic dissection. Stanford type B aortic dissection, which affects the descending aorta, poses significant diagnostic and therapeutic challenges but can often be managed medically without immediate surgery. This case underscores the necessity of having a vigilant mindset, performing a detailed clinical examination, and including aortic dissection in the differential diagnosis, especially when typical symptoms are observed. The challenging part of this case was the investigation, as computed tomography angiography couldn't be performed, necessitating the use of magnetic resonance imaging for diagnosis. It highlights the importance of individualized patient care, vigilant monitoring, and comprehensive management strategies in the treatment of aortic dissection.

Navigating clinical appropriateness: A review of management strategies for type B aortic dissection

Aortic dissection is a catastrophic, life-threatening event. Its management depends on the anatomic location of the intimal tear (type A v B) and the clinical presentation in type B aortic dissection. In this article, the current evidence supporting clinical practice, gaps in knowledge, and the need for more rigorous research and higher-quality studies are reviewed.

Systematic review of the effect of cerebrospinal fluid drainage on outcomes after endovascular type B aortic dissection repair

OBJECTIVE

The aim of the present systematic review was to determine whether prophylactic use of cerebrospinal fluid drainage (CSFD) contributes to a lower rate of spinal cord ischemia (SCI) after thoracic endovascular aortic repair (TEVAR) for type B aortic dissection (TBAD).

METHODS

PubMed, Embase, Web of Science and Cochrane Library databases were systematically searched to identify all relevant studies reported before May 7, 2023. A systematic review was conducted in accordance with PRISMA guidelines (PROSPERO registration no. CRD42023441392). The primary outcome was permanent SCI. Secondary outcomes were temporary SCI and 30-day/in-hospital mortality. The data were presented as the pooled event rates (ERs) and 95% confidence intervals (CIs).

RESULTS

A total of 1008 studies were screened, of which 34 studies with 2749 patients were included in the present analysis. The mean Downs and Black quality assessment score was 8.71 (range, 5-12). The pooled rate of permanent SCI with prophylactic CSFD was identical to that without prophylactic CSFD (2.0%; 95% CI, 1.0-3.0; P = 0.445). No statistically significant difference was found between the rates of permanent SCI with routine vs. selective prophylactic CSFD (P = 0.596). The pooled rate of temporary SCI was 1.0% (95% CI, 0.00-1.0%). The pooled rate for 30-day or in-hospital mortality was not significantly different (P = 0.525) in patients with prophylactic CSFD (4.0, 95% CI 2.0-6.0) or without prophylactic CSFD (5.0, 95% CI 2.0-7.0).

CONCLUSIONS

The systematic review has shown that prophylactic CSFD was not associated with a lower rate of permanent SCI and 30-day or in-hospital mortality after TEVAR for TBAD.

Need for and update on clinical trials for uncomplicated type B aortic dissection

The mainstay of management for uncomplicated type B aortic dissection is currently optimal medical therapy, targeting blood pressure and heart rate, along with serial imaging. There is a paucity of data that informs whether early intervention with thoracic endografting in this group of patients will promote aortic remodeling and better long-term outcomes. Investigations to date, including the Investigation of Stent Grafts in Aortic Dissection (INSTEAD), INSTEAD-XL, and Acute Dissection: Stent Graft or Best Medical Therapy (ADSORB) studies, have compared thoracic endovascular aortic repair (TEVAR) with optimal medical therapy in patients with uncomplicated type B aortic dissection but have not shown a benefit for TEVAR conclusively. We discuss three major new randomized trials, which will recruit concurrently in Scandinavia (the Scandinavian trial of uncomplicated aortic dissection therapy [SUNDAY] trial), in the United States (the IMPRoving outcomes in vascular DisEase - aortic dissection [IMPROVE-AD] trial) and the United Kingdom (the Early aortic repair in patients needing endovascular surgery for type B aortic dissection [EARNEST] trial), which promise to provide conclusive, level 1 evidence to decipher whether early TEVAR in this cohort of patients in beneficial.

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.

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.

Cost analysis of thoracic endovascular aortic repair in type B aortic dissection: How much does quality cost?

BACKGROUND

Aortic dissection (AD) is a life-threatening medical emergency that affects an estimated 3-4 people per 100,000 annually, with 40% of cases classified as type B AD (TBAD). TBAD can be further classified as being complicated (co-TBAD) or uncomplicated (un-TBAD) based on the presence or absence of certain features such as malperfusion and rupture. TBAD can be managed conservatively with optimal medical therapy (OMT), or invasively with open surgical repair (OSR) or thoracic endovascular aortic repair (TEVAR), depending on several factors such as type of TBAD and its clinical acuity. The cost-effectiveness, or cost-benefit profile, of these strategies must be given equal consideration. However, TBAD studies featuring cost analyses are limited within the literature. This narrative review aims to address the gap in the literature on cost-effectiveness of TBAD treatments by providing an overview of cost analyses comparing OMT with TEVAR in un-TBAD and TEVAR with OSR in co-TBAD. Another aim is to provide a market analysis of the commercially available TEVAR devices.

METHODS

A comprehensive literature search was performed using several search engines including PubMed, Ovid, Google Scholar, Scopus, and Embase to identify and extract relevant studies.

RESULTS

Several TEVAR devices are available commercially on the global market costing $12,000-19,495. Nevertheless, the Terumo Aortic RELAY® stent graft seems to be the most cost-effective, yielding highly favourable clinical outcomes. Despite the higher initial cost of TEVAR, evidence in the literature strongly suggest that it is superior to OMT for un-TBAD on the long-term. In addition, TEVAR is well established in the literature as being gold-standard repair technique for co-TBAD, replacing OSR by offering a more optimal cost-benefit profile through lower costs and improved results.

CONCLUSIONS

The introduction of TEVAR has revolutionized the field of aortovascular surgery by offering a highly efficacious and long-term cost-effective treatment for TBAD.

Transesophageal Ultrasound Guidance for Endovascular Interventions on the Aorta

Aortic pathologies in general require a multidisciplinary approach and decision-making to integrate elements of clinical acuity, vascular pathology, individual comorbidity, and risk assessment; thus, ideally it is a center with access to multiple imaging modalities and expertise in all treatment options. Besides classic open surgical options, endovascular procedures have been accepted for a variety of aortic pathologies. More recently, novel transcatheter interventions even to the proximal aorta have been introduced, particularly for patients unfit for open surgery. Nevertheless, the role of transesophageal echocardiography to guide percutaneous aortic interventions is not well established, notwithstanding the growing potential as an ancillary tool to guide the procedure and document success.

Wall Shear Stress Assessment of the False Lumen in Acute Type B Aortic Dissection Visualized by 4-Dimensional Flow Magnetic Resonance Imaging: An Ex-Vivo Study

BACKGROUND

Four-dimensional flow magnetic resonance imaging (4D flow MRI) can accurately visualize and quantify flow and provide hemodynamic information such as wall shear stress (WSS). This imaging technique can be used to obtain more insight in the hemodynamic changes during cardiac cycle in the true and false lumen of uncomplicated acute Type B Aortic Dissection (TBAD). Gaining more insight of these forces in the false lumen in uncomplicated TBAD during optimal medical treatment, might result in prediction of adverse outcomes.

METHODS

A porcine aorta dissection model with an artificial dissection was positioned in a validated ex-vivo circulatory system with physiological pulsatile flow. 4D flow MR images with 3 set heartrates (HR; 60 bpm, 80 bpm and 100 bpm) were acquired. False lumen volume per cycle (FLV), mean and peak systolic WSS were determined from 4D flow MRI data. For validation, the experiment was repeated with a second porcine aorta dissection model.

RESULTS

During both experiments an increase in FLV (initial experiment: ΔFLV = 2.05 ml, p < 0.001, repeated experiment: ΔFLV = 1.08 ml, p = 0.005) and peak WSS (initial experiment: ΔWSS = 1.2 Pa, p = 0.004, repeated experiment: ΔWSS = 1.79 Pa, p = 0.016) was observed when HR increased from 60 to 80 bpm. Raising the HR from 80 to 100 bpm, no significant increase in FLV (p = 0.073, p = 0.139) was seen during both experiments. The false lumen mean WSS increased significant during initial (2.71 to 3.85 Pa; p = 0.013) and non-significant during repeated experiment (3.22 to 4.00 Pa; p = 0.320).

CONCLUSION

4D flow MRI provides insight into hemodynamic dimensions including WSS. Our ex-vivo experiments showed that an increase in HR from 60 to 80 bpm resulted in a significant increase of FLV and WSS of the false lumen. We suggest that strict heart rate control is of major importance to reduce the mean and peak WSS in uncomplicated acute TBAD. Because of the limitations of an ex-vivo study, 4D flow MRI will have to be performed in clinical setting to determine whether this imaging model would be of value to predict the course of uncomplicated TBAD.

Pernicious pregnancy: Type B aortic dissection in pregnant women

BACKGROUND

Type B aortic dissection (TBAD) occurs seldomly, particularly in pregnancy, but has disastrous consequences for both mother and fetus. The focus of immediate surgical repair of type A aortic dissection due to higher mortality of patients is less clear in its counterpart, TBAD, in which management is controversial and debated. This article collates knowledge so far on this rare event during pregnancy.

METHODS

A comprehensive literature search was performed in PubMed, Scopus, Google Scholar, Embase, and Medline. Key search terms included "type B aortic dissection," "pregnancy," and corresponding synonyms. Non-English papers were excluded.

RESULTS

Risk factors for TBAD include aortic wall stress due to hypertension, previous cardiac surgery, structural abnormalities (bicuspid aortic valve, aortic coarctation), and connective tissue disorders. In pregnancy, pre-eclampsia is a cause of increased aortic wall stress. Management of this condition is often conservative, but this is dependent on a number of factors, including gestation, cardiovascular stability of the patient, and symptomology. In most cases, a cesarean section before intervention is carried out unless certain indications are present.

CONCLUSIONS

Due to a scarce number of cases across the decades, it is difficult to determine which management is optimal. The gold-standard management of TBAD has traditionally been the medical treatment for uncomplicated cases and open surgery for those needing urgent intervention, but with the advent of techniques, such as thoracic endovascular aortic repair, the management of these group of patients continues to develop.

Finite element modeling to predict procedural success of thoracic endovascular aortic repair in type A aortic dissection

Objective

Thoracic endovascular aortic repair (TEVAR) is recommended for type B aortic dissection and recently has even been used in selected cases of proximal (Stanford type A) aortic dissections in scenarios of prohibitive surgical risk. However, mechanical interactions between the native aorta and stent-graft are poorly understood, as some cases ended in failure. The aim of this study is to explore and better understand biomechanical changes after TEVAR and predict the result via virtual stenting.

Methods

A case of type A aortic dissection was considered inoperable and selected for TEVAR. The procedure failed due to stent-graft migration even with precise deployment. A novel patient-specific virtual stent-graft deployment model based on finite element method was employed to analyze TEVAR-induced changes under such conditions. Two landing positions were simulated to investigate the reason for stent-graft migration immediately after TEVAR and explore options for optimization.

Results

Simulation of the actual procedure revealed that the proximal bare metal stent pushed the lamella into the false lumen and led to further stent-graft migration during the launch phase. An alternative landing position has reduced the local deformation of the dissection lamella and avoided stent-graft migration. Higher maximum principal stress (>20 KPa) was found on the lamella with deployment at the actual position, while the alternative strategy would have reduced the stress to <5 KPa.

Conclusions

Virtual stent-graft deployment simulation based on finite element model could be helpful to both predict outcomes of TEVAR and better plan future endovascular procedures.

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.

The Influence of Aortic Wall Elasticity on the False Lumen in Aortic Dissection: An In Vitro Study

BACKGROUND

Hemodynamics, dissection morphology, and aortic wall elasticity have a major influence on the pressure in the false lumen. In contrast to aortic wall elasticity, the influence of hemodynamics and dissection morphology have been investigated often in multiple in vitro and ex vivo studies. The purpose of this study was to evaluate the influence of aortic wall elasticity on the diameter and pressure of the false lumen in aortic dissection.

METHODS

An artificial dissection was created in 3 ex vivo porcine aortas. The aorta models were consecutively positioned in a validated in vitro circulatory system with physiological pulsatile flow. Each model was imaged with ultrasound on 4 positions along the aorta and the dissection. At these 4 locations, pressure measurement was also performed in the true and false lumen with an arterial catheter. After baseline experiments, the aortic wall elasticity was adjusted with silicon and the experiments were repeated.

RESULTS

The aortic wall elasticity was decreased in all 3 models after siliconizing. In all 3 siliconized models, the diameters of the true and false lumen increased at proximal, mid, and distal location, while the mean arterial pressure did not significantly change.

CONCLUSIONS

In this in vitro study, we showed that aortic wall elasticity is an important parameter altering the false lumen. An aortic wall with reduced elasticity results in an increased false lumen diameter in the mid and distal part of the false lumen. These results can only be transferred to corresponding clinical situations to a limited extent.

Management of Uncomplicated Type B Aortic Dissection

Acute aortic dissection has an incidence of approximately half that of symptomatic abdominal and thoracic aneurysm of the aorta and more than twice the mortality of population-based controls. While urgent undelayed open surgery is the strategy of choice in proximal dissection, medical management has been the mainstay of treatment for uncomplicated distal or type B aortic dissection, but endovascular intervention is now considered a potential treatment option for all type B dissection due to its success in complicated cases. Endovascular repair can be technically demanding in aortic dissection, and timing of the repair can have a significant influence on anatomical and clinical outcome. Observational reports of feasibility and reasonable safety are flanked by only two randomised trials; the Acute Dissection Stent Grafting or Best Medical Treatment (ADSORB) trial demonstrated improved remodelling in acute dissection and the INvestigation of STEnt grafts in patients with type B Aortic Dissections (INSTEAD) trial showed better long-term survival in patients treated endovascularly in the subacute phase. Meta-analyses and other large clinical studies have demonstrated mixed results. Due to some risks associated endovascular repair and the requirement of specialist aortic care (which is not always available), a pragmatic approach for current management could involve high intensity serial imaging in the acute phase of a type B aortic dissection, thereby identifying complicated cases for early intervention and selection of patients at high risk of disease progression for deferred endovascular management in the subacute phase within 90 days.

Long-term Results of Thoracic Endovascular Aortic Repair for Type B Aortic Dissection and Risk Factors for Survival

Purpose: To compare characteristics of acute, subacute, and chronic type B aortic dissection and their influence on long-term results of thoracic endovascular aortic repair (TEVAR). Materials and Methods: In a single-center, retrospective cohort study, 314 patients (median age 52 years; 244 men) with acute (n=165), subacute (n=115), or chronic (n=34) type B aortic dissection underwent TEVAR between January 2009 and December 2013. Patient demographics, risk factors, and imaging characteristics were compared among the groups. Univariable and multivariable Cox regression analyses were performed to identify any factors influencing survival. Results: The acute and subacute patients exhibited more complications at presentation than chronic patients. However, the chronic patients exhibited more aneurysmal dilatation (p<0.001) and true lumen collapse (p<0.001). Over a mean follow-up of 68.1±22.9 months (range 2–108), subacute patients showed a lower reintervention rate (3.6% vs 12.1% vs 12.1%, p=0.045), a lower major complication rate (14.4% vs 33.1% vs 27.3%, p=0.002), and better cumulative overall survival (p=0.03) than the acute and chronic groups, respectively. Furthermore, acute patients developed more stent-graft–induced distal erosion (p=0.017) and retrograde type A dissection (RTAD) (p=0.036), whereas chronic patients had less aortic remodeling in the stented segment (p<0.001), distal thoracic aorta (p<0.001), and abdominal aorta (p=0.047). Finally, multivariable analysis demonstrated age >52 years, visceral malperfusion, and RTAD as independent factors influencing overall survival; aneurysmal dilatation, rupture/impending rupture, and RTAD were independent factors influencing aorta-specific survival. Conclusion: Acute and subacute patients had increased risks of rupture and complications at presentation, whereas chronic patients had increased risks for aneurysmal dilatation. From a long-term perspective, the subacute phase might be an optimal time for TEVAR in cases of type B aortic dissection that do not need emergent interventions. The risk factors influencing survival should be identified, carefully managed, and possibly prevented.

Virtual TEVAR: Overcoming the Roadblocks of In-Silico Tools for Aortic Dissection Treatment

The use of in silico tools for the interventional planning of complex vascular conditions, such as Aortic Dissections has been often limited by high computational cost, involving long timescales for accurate results to be produced and low numbers of patients, precluding the use of statistical analyses to inform individual-level models. In the paper [Theranostics 2018; 8(20):5758-5771. doi:10.7150/thno.28944], Chen et al. proposed a novel algorithm to compute patient-specific 'virtual TEVAR' that will help clinicians to approach individual treatment and decision-making based on objective and quantifiable metrics and validated on a cohort of 66 patients in real time. This research will significantly impact the field and has the potential to transform the way clinical interventions will be approached in the future.