Long-Term Outcome of Aortic Dissection With Patent False Lumen

The application of computational modeling for risk prediction in type B aortic dissection

OBJECTIVE

New tools are urgently needed to help with surgical decision-making in type B aortic dissection (TBAD) that is uncomplicated at the time of initial presentation. This narrative review aims to answer the clinical question, Can computational modeling be used to predict risk in acute and chronic Stanford TBAD?

METHODS

The review (PROSPERO 2018 CRD42018104472) focused on risk prediction in TBAD. A comprehensive search of the Ovid MEDLINE database, using terms related to computational modeling and aortic dissection, was conducted to find studies of any form published between 1998 and 2018. Cohort studies, case series, and case reports of adults (older than 18 years) with computed tomography or magnetic resonance imaging diagnosis of TBAD were included. Computational modeling was applied in all selected studies.

RESULTS

There were 37 studies about computational modeling of TBAD identified from the search, and the findings were synthesized into a narrative review. Computational modeling can produce numerically calculated values of stresses, pressures, and flow velocities that are difficult to measure in vivo. Hemodynamic parameters-high or low wall shear stress, high pressure gradient between lumens during the cardiac cycle, and high false lumen flow rate-have been linked to the pathogenesis of branch malperfusion and aneurysm formation by numerous studies. Considering the major outcomes of end-organ failure, aortic rupture, and stabilization and remodeling, hypotheses have been generated about inter-relationships of measurable parameters in computational models with observable anatomic and pathologic changes, resulting in specific clinical outcomes.

CONCLUSIONS

There is consistency in study findings about computational modeling in TBAD, although a limited number of patients have been analyzed using various techniques. The mechanistic patterns of association found in this narrative review should be investigated in larger cohort prospective studies to further refine our understanding. It highlights the importance of patient-specific computational hemodynamic parameters in clinical decision-making algorithms. The current challenge is to develop and to test a risk assessment method that can be used by clinicians for TBAD.

Parametric Hemodynamic 4D Flow MRI Maps for the Characterization of Chronic Thoracic Descending Aortic Dissection

BACKGROUND

Systematic evaluation of complex flow in the true lumen and false lumen (TL, FL) is needed to better understand which patients with chronic descending aortic dissection (DAD) are predisposed to complications.

PURPOSE

To develop quantitative hemodynamic maps from 4D flow MRI for evaluating TL and FL flow characteristics.

STUDY TYPE

Retrospective.

POPULATION

In all, 20 DAD patients (age = 60 ± 11 years; 12 male) (six medically managed type B AD [TBAD], 14 repaired type A AD [rTAAD] now with ascending aortic graft [AAo] or elephant trunk [ET1] repair) and 21 age-matched controls (age = 59 ± 10 years; 13 male) were included.

FIELD STRENGTH/SEQUENCE

1.5T, 3T, 4D flow MRI.

ASSESSMENT

4D flow MRI was acquired in all subjects. Data analysis included 3D segmentation of TL and FL and voxelwise calculation of forward flow, reverse flow, flow stasis, and kinetic energy as quantitative hemodynamics maps.

STATISTICAL TESTS

Analysis of variance (ANOVA) or Kruskal-Wallis tests were performed for comparing subject groups. Correlation and Bland-Altman analysis was performed for the interobserver study.

RESULTS

Patients with rTAAD presented with elevated TL reverse flow (AAo repair: P = 0.004, ET1: P = 0.018) and increased TL kinetic energy (AAo repair: P = 0.0002, ET1: P = 0.011) compared to controls. In addition, TL kinetic energy was increased vs. patients with TBAD (AAo repair: P = 0.021, ET1: P = 0.048). rTAAD was associated with higher FL kinetic energy and lower FL stasis compared to patients with TBAD (AAo repair: P = 0.002, ET1: P = 0.024 and AAo repair: P = 0.003, ET1: P = 0.048, respectively).

DATA CONCLUSION

Quantitative maps from 4D flow MRI demonstrated global and regional hemodynamic differences between DAD patients and controls. Patients with rTAAD vs. TBAD had significantly altered regional TL and FL hemodynamics. These findings indicate the potential of 4D flow MRI-derived hemodynamic maps to help better evaluate patients with DAD.

LEVEL OF EVIDENCE

3 Technical Efficacy Stage: 1 J. Magn. Reson. Imaging 2020;51:1357-1368.

Salvage endovascular septectomy in patients with chronic abdominal aortic dissection after failed endovascular aneurysm repair

This study aimed to investigate the efficacy and safety of salvage endovascular septectomy in patients with abdominal chronic aortic dissection (CAD) after endovascular aneurysm repair. A study cohort comprising 6 patients with chronic abdominal aortic dissection after failed endovascular aortic repair [mean age 62.5 (36-69) years] were enrolled to undergo salvage endovascular septectomy. The procedure involved entering the false lumen via the intrinsic visceral entry to perform a confined septectomy using a 'Gigli wire' to merge the true and false lumens. The outcomes were assessed by Digital angiography and computed tomography angiography. All 6 patients were successfully operated on; the diameters of the visceral abdominal aorta and the infrarenal abdominal aorta were similar at 1, 3, 6 and 12 months compared with the baseline; the patency of the visceral branch arteries was also stable at 1, 3, 6 and 12 months compared with the baseline; no occlusion of the visceral branch arteries was noted; no major vascular adverse events or deaths were observed. In this preliminary study, it was proven that salvage endovascular septectomy is a potentially advantageous technique that is safe and effective in the treatment of patients with CAD after failed endovascular aortic repair.

The Role of Thoracic Endovascular Repair in Chronic Type B Aortic Dissection

Continued device improvements along with refined implantation techniques have revolutionize the use of thoracic endovascular repair for both aortic dissections and aneurysms. This is now considered standard of care for acute, complicated type B aortic dissection in patients with appropriate anatomy. However, the treatment of chronic, uncomplicated type B dissection continues to present challenges for the aortic surgeon, as the long-held dogma of medical management and surveillance for aneurysm degeneration has recently come into questions. We present evidence for a more thoughtful approach to management and intervention with thoracic endovascular repair in select patients with chronic, type B dissection.

Multibranched endovascular aortic aneurysm repair in patients with and without chronic aortic dissections

OBJECTIVE

The objective of this study was to compare multibranched endovascular aneurysm repair (MBEVAR) of postdissection thoracoabdominal aortic aneurysms (TAAAs) and pararenal aortic aneurysms (PRAAs) with MBEVAR of degenerative TAAAs and PRAAs and to assess the role played by the preoperative correction of potential complicating factors, such as true lumen compression and false lumen origin of vital branches, using adjunctive maneuvers.

METHODS

From July 2005 to July 2017, there were 162 patients who underwent elective MBEVAR of TAAAs and PRAAs. Data on demographics, procedural details, and outcomes were collected prospectively.

RESULTS

The mean age was 73 ± 8 years, and 119 of 162 (74%) were men; 19 of 162 (12%) had prior aortic dissections. Patients with dissections were younger (65 ± 11 years vs 74 ± 7 years; P = .002) and were less likely to have smoked (13/19 [68%] vs 135/143 [94%]; P = .002) or to have peripheral artery disease (0/19 [0%] vs 35/143 [24%]; P = .01) compared with those without dissections. Patients with prior dissections were more likely to have Crawford type II (10/19 [53%] vs 22/143 [15%]; P = .001) and type III (6/19 [32%] vs 16/143 [11%]; P = .03) TAAAs and were more likely to require at least one pre-MBEVAR adjunctive procedure (14/19 [74%] vs 55/143 [38%]; P = .006) compared with those without dissection. There was no difference in perioperative death, stroke, or paraplegia rates between the two groups. Median follow-up was 2.4 years (interquartile range, 0.8-4.7) and did not differ significantly between the two groups. There were no significant differences in branch vessel occlusion, endoleak rate, or aneurysm-related death between the two groups.

CONCLUSIONS

Patients with chronic type B aortic dissection are more likely to have extensive aneurysms and more likely to require adjunctive procedures to provide the appropriate anatomic substrate for MBEVAR, but this does not appear to affect the conduct of MBEVAR or its outcomes.

Intermediate fenestrations reduce flow reversal in a silicone model of Stanford Type B aortic dissection

Pulsatile, three-dimensional hemodynamic forces influence thrombosis, and may dictate progression of aortic dissection. Intimal flap fenestration and blood pressure are clinically relevant variables in this pathology, yet their effects on dissection hemodynamics are poorly understood. The goal of this study was to characterize these effects on flow in dissection models to better guide interventions to prevent aneurysm formation and false lumen flow. Silicone models of aortic dissection with mobile intimal flap were fabricated based on patient images and installed in a flow loop with pulsatile flow. Flow fields were acquired via 4-dimensional flow MRI, allowing for quantification and visualization of relevant fluid mechanics. Pulsatile vortices and jet-like structures were observed at fenestrations immediately past the proximal entry tear. False lumen flow reversal was significantly reduced with the addition of fenestrations, from 19.2 ± 3.3% in two-tear dissections to 4.67 ± 1.5% and 4.87 ± 1.7% with each subsequent fenestration. In contrast, increasing pressure did not cause appreciable differences in flow rates, flow reversal, and vortex formation. Increasing the number of intermediate tears decreased flow reversal as compared to two-tear dissection, which may prevent false lumen thrombosis, promoting persistent false lumen flow. Vortices were noted to result from transluminal fluid motion at distal tear sites, which may lead to degeneration of the opposing wall. Increasing pressure did not affect measured flow patterns, but may contribute to stress concentrations in the aortic wall. The functional and anatomic assessment of disease with 4D MRI may aid in stratifying patient risk in this population.

The current role of echocardiography in acute aortic syndrome

Acute aortic syndrome (AAS) comprises a range of interrelated conditions caused by disruption of the medial layer of the aortic wall, including aortic dissection, intramural haematoma and penetrating aortic ulcer. Since mortality from AAS is high, a prompt and accurate diagnosis using imaging techniques is paramount. Both transthoracic (TTE) and transoesophageal echocardiography (TEE) are useful in the diagnosis of AAS. TTE should be the first imaging technique to evaluate patients with thoracic pain in the emergency room. Should AAS be suspected, contrast administration is recommended when images are not definitive. TEE allows high-quality images in thoracic aorta. The main drawback of this technique is that it is semi-invasive and the presence of a blind area that limits visualisation of the distal ascending aorta near. TEE identifies the location and size of the entry tear, secondary communications, true lumen compression and the dynamic flow pattern of false lumen. Although computed tomography (CT) is the most used imaging technique in the diagnosis of AAS, echocardiography offers complementary information relevant for its management. The best imaging strategy for appropriately diagnosing and assessing AAS is to combine CT, mainly ECG-gated contrast-enhanced CT, and TTE. Currently, TEE tends to be carried out in the operating theatre immediately before surgical or endovascular therapy and in monitoring their results. The aims of this review are to establish the current role of echocardiography in the diagnosis and management of AAS based on its advantages and limitations.

Aortic remodeling in acute type A aortic dissection after frozen elephant trunk implantation

Survivors at first intervention after acute type A aortic dissection often necessitate additional interventions to avoid dilation and rupture of the remaining thoraco-abdominal aorta. During the first-stage arch procedure, the attempt to treat the descending thoracic aorta with a stent graft could attenuate this phenomenon and reduce the need for further open or endovascular reinterventions. In this short review article, the frozen elephant trunk technique was tested as influencing factor of aortic remodeling during follow-up analysis. Late results from the identified studies suggested promising rates of false lumen thrombosis of the descending thoracic aorta (78-100%), suggesting that aortic remodeling is highly probable with this approach. However, a longer surveillance of the aortic diameters is still necessary to confirm this initial hypothesis.

Proposed classification of endoleaks after endovascular treatment of Stanford type-B aortic dissections

Objectives

Despite two decades of experience, no dedicated classification system exists to document and prognosticate patterns of endoleak encountered after endovascular therapy of type-B aortic dissection. This nomenclature gap has led to inconsistent management and underreporting of significant findings associated with adverse outcomes after endovascular treatment of type-B aortic dissection. Our goal was to propose a reproducible and prognostically relevant classification.

Methods

A multidisciplinary team of seven experienced open and endovascular aortic surgeons was assembled to provide consensus opinion. Extensive literature review was conducted. Deficiencies in the current classification approach of the various patterns of persistent filling of false lumen after endovascular therapy were identified.

Results

Our focus was to categorize high-risk and low-risk subgroups within endoleaks after endovascular treatment of type-B aortic dissection. In this classification, type-Ia endoleak refers to persistent filling of the false lumen in an antegrade manner. Causes include failure to cover the primary entry tear and sizing or technical related proximal seal failure. False lumen filling via distal entry tears is classified as type Ib endoleak, which is further sub-classified into b1 (major branch-related tears), and b2 (multiple small branches related tears). Retrograde ascending aortic dissection and stent graft-induced new entry were classified as type-I endoleaks (type-Ir and type-Is, respectively). Another focus was reclassification type-II endoleaks, with type-IIa endoleak referring to conventional retroleak from one or more posterior branches and type-IIx referring to retroleak from major branches (visceral or left subclavian arteries).

Conclusions

The majority of endoleaks after endovascular treatment of type-B aortic dissection are related to persistent or new filling of the false lumen. We propose a new false lumen-based classification schema for endoleaks occurring after endovascular therapy of type-B aortic dissection.

Detection and Hemodynamic Evaluation of Flap Fenestrations in Type B Aortic Dissection with 4D Flow MRI: Comparison with Conventional MRI and CTA

Purpose

The purpose of this study was to compare dissection flap fenestration visualization between 4D flow MRI, clinical MRI/MRA, and clinical CTA studies and describe the presence of hemodynamically active fenestration flow using 4D flow.

Materials and Methods

Nineteen patients with type B dissection (age: 57±5 years) who had undergone standard of-care MRI/MRA of the chest including 4D flow MRI were retrospectively identified. Fourteen of the 19 patients also had CTA performed within 2 years of the MRI/MRA study with no interval surgery. Image review was performed independently by two radiologists. The number of fenestrations (including entry and exit tears), location, and flow directionality were recorded. Differences in the rate of detection between techniques was assessed using a Wilcoxon signed rank test.

Results

4D flow detected more fenestrations relative to MRI/MRA [rev 1: +3 (10%), rev 2: +5 (20%)]. There were similar numbers of fenestrations detected by 4D flow relative to CTA [rev 1: +1 (4%), rev 2: -3 (-12%)]. MRI/MRA detected fewer fenestration relative to CTA in this cohort [rev 1: -6 (-24%), rev 2: -5 (-19%)]. No differences were significant. Combining 4D flow and MRI/MRA resulted in additional fenestration detection. Most fenestrations demonstrated biphasic flow over the cardiac cycle (flow entering false lumen in systole and exiting during diastole, rev 1:18/33, rev 2: 16/30).

Conclusions

4D flow MRI can detect small flap fenestration in type B dissection patients while providing additional information about flow through fenestrations throughout the cardiac cycle relative to CTA and conventional MRI.

Morphological predictor of remodelling of the descending thoracic aortic false lumen that remains patent after repair of acute type A dissection

OBJECTIVES

Some patients achieve complete recovery through false lumen remodelling in the descending aorta after surgery for acute type A aortic dissection. Our goal was to investigate the relationship between false lumen remodelling during later postoperative stages and quantitative analysis of the true lumen shape during the early postoperative stages.

METHODS

We examined 88 surgical patients between January 2007 and December 2016. Three points of the descending aorta were assessed from the 6th (T6), the 9th (T9) and the 11th (T11) vertebral levels. The shape of the true lumen was evaluated during the early postoperative stages, and false lumen remodelling 1 year after surgery was the end point. The parameters obtained by evaluating the shape of the true lumen comprised the first principal component analysis using elliptic Fourier analysis, the minor diameter ratio and the ratio of the area of the true lumen to that of the descending aorta, and the number of contact points on the true lumen wall during the early stages.

RESULTS

Using univariate analysis, we detected significant differences in the first principal components, the minor diameter ratio, the area ratio and the number of contact points at each thoracic vertebral level (P < 0.05). The cut-off value of the minor diameter ratio was 0.55, and the area ratio was 0.48 as determined by analysis of the receiver operating characteristic. Multivariable logistic analysis indicated that the first principal component was the most significant predictor from the proximal to the middle descending aorta.

CONCLUSIONS

Quantitative evaluation of shape of the true lumen in the early postoperative stages after surgery for acute type A dissection can serve as a viable predictor for false lumen remodelling in later stages. Furthermore, the first principal component could serve as a more astute predictor than other quantitative parameters according to multivariate analysis.

A Promising Treatment of Distal Entry Tears Located in Branched Area of Abdominal Aorta With Coil-Stent Tear Occlusion Device: an Animal Experiment

This study aims to evaluate the effect of coil-stent tear occlusion device in treating entry tears located in branched area of abdominal aorta. An abdominal aortic dissection animal model was constructed by mesh suturing method. The animal models were treated by the occlusion device and were evaluated by computed tomography angiography (CTA) 1 month later. Eighteen pigs were adopted in the abdominal aortic dissection modeling experiment, two of them died of cardiopulmonary arrest during the operation. Sixteen models survived, two of them were found complete false lumen thrombosis by CTA 3 days after the operation. The false lumen kept patency in the remaining 14 cases which were then implanted with the occlusion device. The procedure was successful in 13 cases except for one. The coil-stent tear occlusion device provides a novel method for tears located in the branched area of abdominal aorta, and is worth of further study.

Experimental Insight into the Hemodynamics and Perfusion of Radiological Contrast in Patent and Non-patent Aortic Dissection Models

PURPOSE

In a curved vessel such as the aortic arch, the velocity profile closer to the aortic root is normally skewed towards the inner curvature wall, while further downstream along the curve, the velocity profile becomes skewed towards the outer wall. In an aortic dissection (AD) disease, blood velocities in the true lumen (TL) and false lumen (FL) are hypothesized to depend on the proximity of the entry tear to the root of aortic arch. Faster velocity in the FL can lead to higher hemodynamic loading, and pose tearing risk. Furthermore, the luminal velocities control the perfusion rate of radiological contrast media during diagnostic imaging. The objective in this study is to investigate the effect of AD disease morphology and configuration on the blood velocity field in the TL and FL, and on the relative perfusion of radiological enhancement agents through the dissection.

METHODS

Eight in vitro models were studied, including patent and non-patent FL configurations. Particle image velocimetry (PIV) was used to quantify the AD velocity field, while laser-induced fluorescence (LIF) was implemented to visualize dynamical flow phenomena and to quantify the perfusion of injected dye, in mimicry of contrast-enhanced computed tomography (CT).

RESULTS

The location of the proximal entry tear along the aortic arch in a patent FL had a dramatic impact on whether the blood velocity was higher in the TL or FL. The luminal velocities were dependent on the entry/reentry tear size combination, with the smaller tear (whether distal or proximal) setting the upper limit on the maximal flow velocity in the FL. Upon merging near the distal reentry tear, the TL/FL velocity differential gave rise to the roll up and shedding of shear layer vortices that convected downstream in close proximity to the wall of the non-dissected aorta. In a non-patent FL, the flow velocity was practically null with all the blood passing through the TL. LIF imaging showed much slower perfusion of contrast dye in the FL compared to the TL. In a patent FL, however, dye had a comparable perfusion rate appearing around the same time as in the TL.

CONCLUSIONS

Blood velocities in the TL and FL were highly sensitive to the exact dissection configuration. Geometric case A1R, which had its proximal entry tear located further downstream along the aortic arch, and had its entry and reentry tears sufficiently sized, exhibited the highest FL flow velocity among the tested models, and it was also higher than in the TL, which suggest that this configuration had elevated hemodynamic loading and risk for tearing. In contrast-enhanced diagnostic imaging, a time-delayed acquisition protocol is recommended to improve the detection of suspected cases with a non-patent FL.

The fate of unrepaired chronic type A aortic dissection

OBJECTIVES

The current guidelines do not consider chronic type A aortic dissection as one of the triggers for prophylactic aortic repair, and an aortic diameter of 55 mm is considered the threshold for surgery.

METHODS

From the institutional database, we retrieved 82 patients who were diagnosed as having chronic type A aortic dissection but did not undergo immediate surgical repair from 1997 to 2016. The primary outcome was a composite of adverse aortic events defined as aortic rupture and sudden death. Conversion to elective surgery during follow-up was regarded as competing risk for adverse events.

RESULTS

The median value of the maximal aortic diameter at baseline was 55.2 mm. During a median follow-up of 77.1 months, 19 adverse events occurred while 9 patients received elective aortic repair. On multivariable competing risk analyses, baseline aortic diameter and age emerged as significant and independent factors associated with aortic events. The estimated rates of aortic event within 5 years were 12.0%, 19.4%, and 29.7% for aortic diameters of 50, 60, and 70 mm, respectively, with escalating risk rates as age increased for the given aortic diameters.

CONCLUSIONS

In unrepaired chronic type A aortic dissection, aortic events were not infrequent even for patients with an aortic diameter of less than 55 mm. This finding indicates that there may be a need to lower the surgical threshold for chronic type A aortic dissection.

The distance of the primary intimal tear from the left subclavian artery predicts aortic growth in uncomplicated type B aortic dissection

OBJECTIVE

Controversy exists about the optimal treatment of acute uncomplicated type B aortic dissection (auTBAD). Optimal medical therapy (OMT) provides excellent short-term outcomes, but long-term results are poor. Ideally, auTBAD patients who will fail to respond to OMT in the chronic phase could be identified and undergo thoracic endovascular aortic repair. The purpose of this study was to identify radiographic predictors of auTBAD patients who will fail to respond to OMT.

METHODS

A review of the Emory aortic database from 2000 to 2017 identified 320 auTBAD patients initially treated with OMT. From this cohort, 121 patients with two or more contrast-enhanced imaging scans were available for analysis. These patients were initially divided into groups based on growth of the thoracic aorta ≥10 mm or intervention due to aneurysmal growth: growth (n = 72) and no growth (n = 49). TeraRecon (Foster City, Calif) imaging software was used to analyze characteristics of the primary intimal tear (PIT), false lumen, and overall aortic size. Finally, Cox proportional hazards models were constructed to estimate hazard ratios and to identify predictors of OMT failure.

RESULTS

The mean age of all patients was 54 ± 11 years, and 67% were male. Thirty-eight patients (53%) in the growth group underwent intervention. There were no differences between groups in age, hypertension, diabetes mellitus, tobacco abuse, or chronic obstructive pulmonary disease. The distance of the PIT from the left subclavian artery in patients with auTBAD was significantly shorter in the growth group (growth, 27 mm [9-66 mm]; no growth, 77 mm [26-142 mm]; P < .01). Multivariable Cox regression analysis identified the distance of the PIT from the left subclavian artery and a thoracic aortic diameter >45 mm as independent predictors of failure of OMT. Partial false lumen thrombosis was not a predictor of aortic growth.

CONCLUSIONS

The distance of the PIT from the left subclavian artery is a predictor of aortic growth in auTBAD. Patients with a primary tear located in zone 3 of the proximal descending thoracic aorta should be monitored closely and may be considered for early thoracic endovascular aortic repair in the setting of auTBAD.

Fate of uncomplicated acute type B aortic dissection and impact of concurrent aortic dilatation on remote aortic events

OBJECTIVE

This study aimed to describe the reliable prognostic factors of mortality and subsequent aortic events during the follow-up of uncomplicated type B acute aortic dissection.

METHODS

From January 2004 to December 2014, 255 patients with uncomplicated type B acute aortic dissection were admitted to our hospital. Cox proportional hazards analysis was performed to identify risk factors for all-cause mortality, aorta-related mortality, and aortic events.

RESULTS

In-hospital mortality was observed in 7 patients (2.7%). The rates of 5-year freedom from all-cause mortality, aorta-related mortality, and aortic events were 79.4% ± 2.9%, 93.3% ± 2.0%, and 71.7% ± 3.4%, respectively. The rate of 5-year freedom from aortic events was significantly lower among those with a patent false lumen (P = .006). Age and descending aorta diameter were independent risk factors of all-cause and aorta-related mortality (hazard ratio [HR], 1.08 and 1.13; 95% confidence interval [CI], 1.04-1.10 and 1.03-1.24; P = .0001 and .007, respectively). Independent risk factors for aortic events were descending aorta diameter, false lumen thickness, and dilatation of abdominal aorta (HR, 1.06; 95% CI, 1.02-1.12; P = .006; HR, 1.07; 95% CI, 1.04-1.11; P = .00002; HR, 2.01; CI, 1.20-3.38; P = .008).

CONCLUSIONS

In uncomplicated type B acute aortic dissection, the age and dilatation of the thoracic aorta were associated with a higher risk of death, whereas false lumen thickness and concurrent abdominal aortic dilatation augment the risk for aortic events.

Fate of distal aorta after frozen elephant trunk and total arch replacement for type A aortic dissection in Marfan syndrome

OBJECTIVE

The use of the frozen elephant trunk technique for type A aortic dissection in Marfan syndrome is limited by the lack of imaging evidence for long-term aortic remodeling. We seek to evaluate the changes of the distal aorta and late outcomes after frozen elephant trunk and total arch replacement for type A aortic dissection in patients with Marfan syndrome.

METHODS

Between 2003 and 2015, we performed frozen elephant trunk + total arch replacement for 172 patients with Marfan syndrome suffering from type A aortic dissection (94 acute; 78 chronic). Mean age was 34.6 ± 9.3 years, and 121 were male (70.3%). Early mortality was 8.1% (14/172), and follow-up was complete in 98.7% (156/158) at a mean of 6.2 ± 3.3 years. Aortic dilatation was defined as a maximal diameter of greater than 50 mm or an average growth rate of greater than 5 mm/year at any segment detected by computed tomographic angiography. Temporal changes in the false and true lumens and maximal aortic size were analyzed with linear mixed modeling.

RESULTS

After surgery, false lumen obliteration occurred in 86%, 39%, 26%, and 21% at the frozen elephant trunk, unstented descending aorta, diaphragm, and renal artery, respectively. The true lumen expanded significantly over time at all segments (P < .001), whereas the false lumen shrank at the frozen elephant trunk (P < .001) and was stable at distal levels (P > .05). Maximal aortic size was stable at the frozen elephant trunk and renal artery (P > .05), but grew at the descending aorta (P = .001) and diaphragm (P < .001). Respective maximal aortic sizes before discharge were 40.2 mm, 32.1 mm, 31.6 mm, and 26.9 mm, and growth rate was 0.4 mm/year, 2.8 mm/year, 3.6 mm/year, and 2.6 mm/year. By the latest follow-up, distal maximal aortic size was stable in 63.5% (99/156), and complete remodeling down to the mid-descending aorta occurred in 28.8% (45/156). There were 22 late deaths and 23 distal reoperations. Eight-year incidence of death was 15%, reoperation rate was 20%, and event-free survival was 65%. Preoperative distal maximal aortic size (mm) predicted dilatation (hazard ratio, 1.11; P < .001) and reoperation (hazard ratio, 1.07; P < .001). A patent false lumen in the descending aorta predicted dilatation (hazard ratio, 3.88; P < .001), reoperation (hazard ratio, 3.36; P = .014), and late death (hazard ratio, 3.31; P = .045).

CONCLUSIONS

The frozen elephant trunk technique can expand the true lumen across the aorta, decrease or stabilize the false lumen, and stabilize the distal aorta in patients with Marfan syndrome with type A aortic dissection, thereby inducing favorable remodeling in the distal aorta. This study adds long-term clinical and radiologic evidence supporting the use of the frozen elephant trunk technique for type A dissection in Marfan syndrome.

Comparison of Outcomes in DeBakey Type AI Versus AII Aortic Dissection

The DeBakey classification divides type A acute aortic dissection (AAD) into type I and type II; the latter limited to the ascending aorta. We endeavored to examine differences in DeBakey groups in a contemporary registry. We divided 1,872 patients with noniatrogenic AAD from the International Registry of Acute Aortic Dissection into type I (n = 1691, 90.3%) and type II (n = 181, 9.7%). Patients with type II AAD were older. On presentation, patients with type I AAD reported more back and abdominal pain and were more likely to have pulse deficit. Intramural hematoma was more frequent in type II AAD. Most patients with both types were treated surgically. Lower rates of renal failure, coma, mesenteric and limb ischemia were noted in those with type II AAD. In-hospital death was less frequent (16.6% vs 22.5%) after type II AAD, a trend that did not reach significance. There was no difference in the incidence of new dissection, rapid aortic growth, late aortic intervention or survival at 5 years. In conclusion, AAD limited to the ascending aorta (DeBakey type II) appears to be associated with improved clinical outcomes compared with dissection that extend to the aortic arch or beyond. Although fewer dissection-related complications were noted in patients presenting with type II AAD, as was a trend toward reduced in-hospital mortality, 5-year survival and descending aortic sequelae are not reduced in this contemporary report from International Registry of Acute Aortic Dissection.

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.

New predictor of aortic enlargement in uncomplicated type B aortic dissection based on elliptic Fourier analysis

OBJECTIVES

This study aimed to re-examine the conventional predictive factors for dissected aortic enlargement, such as the aortic and false lumen diameter and to consider whether the morphological elements of the dissected aorta could be predictors by quantifying the 'shape' of the true lumen based on elliptic Fourier analysis.

METHODS

A total of 80 patients with uncomplicated type B aortic dissection were included. The patients were divided into 'Enlargement group' and 'No Change group.' Between the 2 groups, the mean systolic blood pressure during follow-up, aortic and false lumen maximum diameters, and analysed morphological data were compared using each statistical method.

RESULTS

The maximum aortic and false lumen diameters were significantly larger in the Enlargement group than in the No Change group (39.3 vs 35.9 mm; P = 0.0058) (23.5 vs 18.2 mm; P = 0.000095). The principal component 1, which is the data calculated by elliptic Fourier analysis, was significantly lower in the Enlargement group than in the No Change group (0.020 vs - 0.072; P = 0.000049). The mean systolic blood pressure ≥130 mmHg, aortic diameter, false lumen diameter and principal component 1 were included in the Cox proportional hazard model as covariates to determine the significant predictive variable. Principal component 1 demonstrated the only significance with aortic enlargement on multivariate analysis (odds ratio = 0.32; P = 0.048).

CONCLUSIONS

The analysed and calculated morphological data of the shape of the true lumen can be more effective predictive factors of aortic enlargement of type B dissection than the conventional factors.

One-stage hybrid aortic repair using the frozen elephant trunk in acute DeBakey type I aortic dissection

Background

The extent of emergent surgery for acute DeBakey type I aortic dissection is discussed controversial. The frozen elephant trunk (FET) technique in addition to ascending and arch repair promotes aortic remodelling in the descending aorta and thus may provide superior long-term results in terms of less secondary re-interventions and reduced mortality linked to the downstream aorta.

Methods

Between October 2009 and December 2016, a total of 72 patients underwent emergent hybrid aortic repair using the FET for acute DeBakey type I aortic dissection at our centre. Data were analysed from our prospectively collected database and clinical and imaging mid-term follow-up was obtained.

Results

Implant success was 98.6% with an overall 30-day-mortality of 15.3%. New postoperative stroke was seen in 2.8%, new spinal cord injury in 4.2%. In follow-up (mean 37.8±21.2 months) cumulative survival was 75.0% with freedom from distal reintervention in 96.7% and aortic remodelling rate in the descending aorta in 96.5%.

Conclusions

Hybrid aortic repair using the FET in acute DeBakey type I aortic dissection does not elevate the perioperative risk of mortality and provides excellent aortic remodelling with low distal re-intervention rate in mid-term follow-up.

The prognostic impact of distal anastomotic new entry after acute type I aortic dissection repair

OBJECTIVES

Distal anastomotic new entry (DANE) is considered to be one of the causes of patent false lumen (PFL) after acute type I aortic dissection repair. However, there have been few articles with regard to this important issue. We assessed the influence of PFL caused by DANE on long-term outcomes.

METHODS

One hundred twenty-two patients underwent emergency surgery for acute type I aortic dissection (2007-12). The in-hospital mortality was 8% (10 patients). Among the survivors, 93 patients (mean age 67 years) underwent enhanced computed tomography within 2 weeks after the operation. These patients were divided into 3 groups according to the status of the residual FL: those with a PFL with DANE (n = 19) or without DANE (n = 27) and those with a thrombosed FL (n = 47). Changes in descending aortic diameter were analysed between early and last follow-up images.

RESULTS

Aortic growth rate in the PFL with DANE group was greater than that of the other 2 groups (P < 0.05). The PFL with DANE group demonstrated a lower rate of freedom from dissection-related event of distal aorta (66% at 5 years) and enlargement of distal aortic lesions (62% at 5 years). There were no significant differences in late survival among the groups. PFL with DANE was one of the significant risk factors for distal aortic events.

CONCLUSIONS

PFL caused by DANE after acute type I aortic dissection repair showed greater aortic growth rate of the descending aorta and was one of the significant risk factors for distal aortic events.

Acute type A aortic dissection: Rationale and outcomes of extensive repair of the arch and distal aorta

Type A acute aortic dissection represents one of the most complex and life-threatening disorders of the cardiovascular system. Cardiac tamponade caused by ascending aorta rupture is the most common cause of death. In light of this, emergent surgery with ascending and partial arch replacement represents, in most of cases, the best and the faster therapeutic option. The natural history of aortic dissection, however, teaches us that in most cases there is a distal progression of the aortic disease that often requires further surgical and/or endovascular treatments. In light of this, it can be hypothesized that, by increasing the extent of aortic replacement during the first operation, it may improve the outcome of these patients by reducing the probability of a second surgery or, in selected cases and for appropriate indications, by treating with a single surgical step, the disease. In this short review of the literature, we focalized on the rationale and outcome of an extensive repair of the thoracic aorta.

Endovascular Treatment of Various Aortic Pathologies: Review of the Latest Data and Technologies

The technologies and innovations applicable to endovascular treatment for complex aortic pathologies have progressed rapidly over the last two decades. Although the initial outcomes of an endovascular aortic repair have been excellent, as long-term data became available, complications including endoleaks, endograft migration, and endograft infection have become apparent and are of concern. Previously, the indication for endovascular therapy was restricted to descending thoracic aortic aneurysms and abdominal aortic aneurysms. However, its indication has expanded along with the improvement of techniques and devices, and currently, it has become possible to treat pararenal aortic aneurysms and Crawford type 4 thoracoabdominal aortic aneurysm (TAAA) using the off-the-shelf devices. Additionally, custom-made devices allow for the treatment of arch or more extensive TAAAs. Endovascular treatment is applied not only to aneurysms but also to acute/chronic dissections. However, long-term outcomes are still unclear. This article provides an overview of available devices and the results of endovascular treatment for various aortic pathologies.

Thoracic endovascular aortic repair to treat uncomplicated Stanford type B aortic dissection: The surgeon's dilemma to preventing future complications

Uncomplicated type B aortic dissections have traditionally been managed non-operatively with aggressive blood pressure control. However, the best medical treatment is associated with a considerable risk of disease progression to complicated dissection or aneurysmal degeneration of the affected aortic segment. Thoracic endovascular aortic repair could prevent long-term complications but, because the dissected aorta is vulnerable, it is a high-risk procedure performed in asymptomatic patient. Therefore, endovascular treatment is not a solution for all patients and it should be performed only in the subgroup prone to developing progression of the disease and future complications. A number of studies have suggested several prognostic factors of early or late adverse events such as the patency of the false lumen in the follow-up, an initial aortic diameter ≥4 cm with a patent false lumen, an initial false lumen diameter ≥22 mm in the proximal descending aorta, visceral involvement and recurrent or refractory pain or hypertension. Partial false lumen thrombosis and a proximal entry tear size >10 mm have also been suggested to be associated with an increased rate of aortic growth. We need randomised trials focused on these prognostic factors to reach level 1, class A recommendation for the optimal timing of intervention. Meanwhile, we have to discuss with the patient the pro and cons of this prophylactic, low-invasive but high-risk treatment to personalise medical care and provide the optimal risk-to-benefit ratio.

Type B aortic dissection: new perspectives

Background

Stanford type B aortic dissection is one of the aortic catastrophes with a high mortality and morbidity that needs immediate or delayed treatment, either surgically or endovascularly. This comprehensive review article addresses the current status of open, endovascular and hybrid treatment options for type B aortic dissections with the focus on new therapeutic perspectives.

Methods

Evaluation of currently available evidence based on randomized and registry data and personal experience.

Results

All type B dissections require prompt medical treatment to prevent aortic rupture. Acute complicated dissections are nowadays treated by endografting to reroute blood flow into the true lumen and promote false lumen thrombosis and future aortic remodeling. In acute uncomplicated situations the position of endografting is less clear and should be further delineated; however, on the long run also in these situations endografting might be protective for future aortic catastrophes in certain patient categories. In the chronic dissection with aneurysm formation of the descending thoracic and/or thoracoabdominal aorta, especially in connective tissue disorders, open surgery offers nowadays the best immediate results with long durability. Thoracic endografting plays only a minor role in these circumstances but branched and fenestrated endografting are very promising techniques. Hybrid techniques can offer the solution for high risk patients that are not suitable for open surgery.

Conclusions

Emergent thoracic endografting is the golden standard for all complicated type B dissections while uncomplicated patients with high-risk features might benefit from endovascular repair. Open surgery is limited for chronic post dissection aneurysms. Aortic surveillance is of paramount importance in all situations.

The incidence of delayed complications in acute type B aortic dissections is underestimated

OBJECTIVE

Acute type B aortic dissections (TBADs) can have immediate or delayed complications within the first 2 weeks. Because the majority of clinical series retrospectively categorized TBAD, the incidence and outcome of delayed complications in initially uncomplicated TBAD within the first 14 days are not well described.

METHODS

We retrospectively analyzed 86 patients (78% male; age, 62.5 ± 13 years) with acute TBAD treated consecutively between January 2004 and May 2016 at a tertiary referral center. All TBADs were confirmed by computed tomography angiography (CTA) on admission, after 2 to 5 days, and after 10 to 14 days. Study end points were the incidence of immediate and delayed complications (aortic rupture, malperfusion, rapid aortic expansion >4 mm, pain or hypertension resistant to medical therapy) and in-hospital mortality. In addition, we looked at CTA-detected morphometric variables (maximum diameters of descending aorta, false lumen [FL], and primary entry tear; number of intimal tears; FL configuration; true lumen collapse; course of the dissection) and their association with delayed complications. Finally, we assessed treatment modalities and clinical outcomes.

RESULTS

Of all TBADs, 22 (26%) presented with immediate complications (rupture, n = 11); 64 patients (74%) were initially assessed as having uncomplicated TBAD. Of these 64 patients, 24 (28% of all 86) suffered from delayed complications (malperfusion, n = 10; aortic rupture, n = 3; early expansion >4 mm, n = 8; refractory pain, n = 2; uncontrollable hypertension, n = 1) at a median interval of 7.1 (2-14) days after symptom onset. During the first 14 days, 40 patients (46%) remained uncomplicated. The CTA analysis revealed a significant association of initial thoracic aortic diameter (P = .009), size of the primary entry tear (P = .018), true lumen collapse (P = .019), and partially thrombosed FL (P = .019) with the occurrence of delayed complications within the first 14 days. Of the patients with delayed complications, 87.5% underwent surgery (90% thoracic endovascular aortic repair, 10% peripheral revascularization); 12.5% in this group died following aortic rupture before they received surgical repair. The mortality of patients with delayed complicated TBAD was significantly higher compared with those who remained uncomplicated within the 14-day period (12.5% vs 0%; P = .0221).

CONCLUSIONS

Delayed complications in initially uncomplicated acute TBAD are not infrequent. Morphologic variables like maximum diameter of the descending aorta, primary entry tear, true lumen collapse, and partially thrombosed FL were associated with an increased risk of delayed complications in initially uncomplicated TBAD. Future clinical research must verify the predictive role of clinical and morphologic variables in the acute phase, particularly with regard to a possible early surgical treatment to prevent a fatal outcome.

[Acute aortic syndromes]

Acute aortic syndromes include aortic dissections, intramural hematomas, penetrating ulcers, ruptured or contained ruptured aortic aneurysms. In presence of acute thoracic or dorsal pain, elevated D-Dimers and if acute coronary artery syndrome has been ruled out, additional imaging should be performed to detect acute aortic pathologies. Acute type A dissections involve the ascending aorta. Emergent open repair is the preferred treatment. Acute type B dissections involve the thoracic descending aorta. Endovascular treatment using thoracic stent grafts is indicated in complicated cases (malperfusion, rupture, uncontrolled hypertension) or in cases where risk factors of aortic degeneration are identified. Regarding ruptured abdominal aortic aneurysms, optimization techniques recently led to a reduced postoperative mortality. They include adequate treatment of abdominal compartment syndrome, use of aortic stent grafts, endovascular balloon occlusion and permissive hypotension. Symptomatic complex aneurysms encompass renal and visceral arteries. Nowadays, they can be treated in an urgent setting using new endovascular techniques, such as "off-the shelf" branched stent grafts, parallel techniques, home made or in situ fenestrations of standard stent grafts.

Time-Resolved Three-Dimensional Contrast-Enhanced Magnetic Resonance Angiography in Patients with Chronic Expanding and Stable Aortic Dissections

Objective

To prospectively evaluate our hypothesis that three-dimensional time-resolved contrast-enhanced magnetic resonance angiography (TR-MRA) is able to detect hemodynamic alterations in patients with chronic expanding aortic dissection compared to stable aortic dissections.

Materials and Methods

20 patients with chronic or residual aortic dissection in the descending aorta and patent false lumen underwent TR-MRA of the aorta at 1.5 T and repeated follow-up imaging (mean follow-up 5.4 years). 7 patients showed chronic aortic expansion and 13 patients had stable aortic diameters. Regions of interest were placed in the nondissected ascending aorta and the false lumen of the descending aorta at the level of the diaphragm (FL-diaphragm level) resulting in respective time-intensity curves.

Results

For the FL-diaphragm level, time-to-peak intensity and full width at half maximum were significantly shorter in the expansion group compared to the stable group (p = 0.027 and p = 0.003), and upward and downward slopes of time-intensity curves were significantly steeper (p = 0.015 and p = 0.005). The delay of peak intensity in the FL-diaphragm level compared to the nondissected ascending aorta was significantly shorter in the expansion group compared to the stable group (p = 0.01).

Conclusions

3D TR-MRA detects significant alterations of hemodynamics within the patent false lumen of chronic expanding aortic dissections compared to stable aortic dissections.

Update on the Therapeutic Strategy of Type B Aortic Dissection

Stanford type B aortic dissection (TBAD) is a life-threatening disease. Current therapeutic guidelines recommend medical therapy with aggressive blood pressure lowering for patients with acute TBAD unless they have fatal complications. Although patients with uncomplicated TBAD have relatively low early mortality, aorta-related adverse events during the chronic phase worsen the long-term clinical outcome. Recent advances in thoracic endovascular aortic repair (TEVAR) can improve clinical outcomes in patients with both complicated and uncomplicated TBAD. According to present guidelines, complicated TBAD patients are recommended for TEVAR. However, the indication in uncomplicated TBAD remains controversial. Recent results of randomized trials, which compared the clinical outcome in patients treated with optimal medical therapy and those treated with TEVAR, suggest that preemptive TEVAR should be considered in uncomplicated TBAD with suitable aortic anatomy. However, these trials failed to show improvement in early mortality in patients treated with TEVAR compared with patients treated with optimal medical therapy, which suggest the importance of patient selection for TEVAR. Several clinical and imaging-related risk factors have been shown to be associated with early disease progression. Preemptive TEVAR might be beneficial and should be considered for high-risk patients with uncomplicated TBAD. However, an interdisciplinary consensus has not been established for the definition of patients at high-risk of TBAD, and it should be confirmed by experts including physicians, radiologists, interventionalists, and vascular surgeons. This review summarizes the current understanding of the therapeutic strategy in patients with TBAD based on evidence and expert consensus.