Arnoud V. Kamman

Update in the management of type B aortic dissection

Stanford type B aortic dissection (TBAD) is a life-threatening aortic disease. The initial management goal is to prevent aortic rupture, propagation of the dissection, and symptoms by reducing the heart rate and blood pressure. Uncomplicated TBAD patients require prompt medical management to prevent aortic dilatation or rupture during subsequent follow-up. Complicated TBAD patients require immediate invasive management to prevent death or injury caused by rupture or malperfusion. Recent developments in diagnosis and management have reduced mortality related to TBAD considerably. In particular, the introduction of thoracic stent-grafts has shifted the management from surgical to endovascular repair, contributing to a fourfold increase in early survival in complicated TBAD. Furthermore, endovascular repair is now considered in some uncomplicated TBAD patients in addition to optimal medical therapy. For more challenging aortic dissection patients with involvement of the aortic arch, hybrid approaches, combining open and endovascular repair, have had promising results. Regardless of the chosen management strategy, strict antihypertensive control should be administered to all TBAD patients in addition to close imaging surveillance. Future developments in stent-graft design, medical therapy, surgical and hybrid techniques, imaging, and genetic screening may improve the outcomes of TBAD patients even further. We present a comprehensive review of the recommended management strategy based on current evidence in the literature.

Changes in operative strategy for patients enrolled in the International Registry of Acute Aortic Dissection interventional cohort program

Objective: Advancements in cardiothoracic surgery prompted investigation into changes in operative management for acute type A aortic dissections over time. Methods: One thousand seven hundred thirty‐two patients undergoing surgery for type A aortic dissection were identified from the International Registry of Acute Aortic Dissection Interventional Cohort Database. Patients were divided into time tertiles (T) (T1: 1996–2003, T2: 2004–2010, and T3: 2011–2016). Results: Frequency of valve sparing procures increased (T1: 3.9%, T2: 18.6%, and T3: 26.7%; trend P < .001). Biologic valves were increasingly utilized (T1: 35.6%, T2; 40.6%, and T3: 52.0%; trend P = .009), whereas mechanical valve use decreased (T1: 57.6%, T2: 58.0%, and T3: 45.4%; trend P = .027) for aortic valve replacement. Adjunctive cerebral perfusion use increased (T1: 67.1%, T2: 89.5%, and T3: 84.8%; trend P < .001), with increase in antegrade cerebral techniques (T1: 55.9%, T2: 58.8%, and T3: 66.1%; trend P = .005) and hypothermic circulatory arrest (T1: 80.1%, T2: 85.9%, and T3: 86.8%; trend P = .030). Arterial perfusion through axillary cannulation increased (T1: 18.0%, T2: 33.2%, and T3: 55.7%), whereas perfusion via a femoral approach diminished (T1: 76.0%, T2: 53.3%, and T3: 30.1%) (both P values < .001). Hemiarch replacement was utilized more frequently (T1: 27.0%, T2: 63.3%, and T3: 51.7%; trend P = .001) and partial arch was utilized less frequently (T1: 20.7%, T2: 12.0%, and T3: 8.4%; trend P < .001), whereas complete arch replacement was used similarly (P = .131). In‐hospital mortality significantly decreased (T1: 17.5%, T2: 15.8%, and T3: 12.2%; trend P = .017). Conclusions: There have been significant changes in operative strategy over time in the management of type A aortic dissection, with more frequent use of valve‐sparing procedures, bioprosthetic aortic valve substitutes, antegrade cerebral perfusion strategies, and hypothermic circulatory arrest. Most importantly, a significant decrease of in‐hospital mortality was observed during the 20‐year timespan.

Predictors of aortic growth in uncomplicated type B aortic dissection from the Acute Dissection Stent Grafting or Best Medical Treatment (ADSORB) database.

Background: The high‐risk patient cohort of uncomplicated type B aortic dissections (uTBADs) needs to be clarified. We compared uTBAD patients treated with best medical treatment (BMT), with and without aortic growth, from the Acute Dissection Stent Grafting or Best Medical Treatment (ADSORB) trial database. Furthermore, we looked for trends in outcome for aortic growth and remodeling after BMT and thoracic endovascular aortic repair (TEVAR) and BMT (TEVAR+BMT). Methods: BMT patients with available baseline and a 1‐year follow‐up arterial computed tomography scan were identified. True lumen and false lumen diameter was assessed at baseline and at follow‐up. Patients with false lumen growth (group I) and without false lumen growth (group II) were compared. Predictors of false lumen and total lumen (aortic) growth were identified. Lastly, BMT outcomes were compared with BMT+TEVAR for false lumen thrombosis and change in false lumen and total aortic diameter in four sections: 0 to 10 cm (A), 10 to 20 cm (B), 20 to 30 cm (C), and 30 to 40 cm (D) from the left subclavian artery. Results: The dissection was significantly longer in group I than in group II (43.2 ± 4.9 cm vs 30.4 ± 8.8 cm; P = .002). The number of vessels originating from the false lumen at baseline was identified as an independent predictor of false lumen growth (odds ratio, 22.1; 95% confidence interval, 1.01–481.5; P = .049). Increasing age was a negative predictor of total aortic diameter growth (odds ratio, 0.902; 95% confidence interval, 0.813–1.00; P = .0502). The proximal sections A and B showed complete thrombosis in 80.6% in the BMT+TEVAR group compared with 9.5% in the BMT group. In these sections, changes from patent to partial or partial to complete thrombosis were observed in 90.3% of the TEVAR+BMT group vs 31.0% in the BMT group. In sections C and D, the change in thrombosis was 74.1% for the TEVAR+BMT group vs 20.6% for the BMT group. The false lumen diameter increase at section C was larger in the BMT group. Total lumen diameter decreased in sections A and B in the TEVAR+BMT group compared with an increase in the BMT group (–4.8 mm vs +2.9 mm, and –1.5 mm vs +3.8 mm, respectively). Sections C and D showed minimal and comparable expansion in both treatment groups. Conclusions: The new imaging analysis of the ADSORB trial patients identified the number of vessels originating from the false lumen as an independent predictor of false lumen growth in uTBAD patients. Increasing age was a negative predictor of aortic growth. Our analysis may help to identify which uTBAD patients are at higher risk and should receive TEVAR or be monitored closely during follow‐up.

Contemporary Management Strategies for Chronic Type B Aortic Dissections: A Systematic Review

Background Currently, the optimal management strategy for chronic type B aortic dissections (CBAD) is unknown. Therefore, we systematically reviewed the literature to compare results of open surgical repair (OSR), standard thoracic endovascular aortic repair (TEVAR) or branched and fenestrated TEVAR (BEVAR/FEVAR) for CBAD. Methods EMBASE and MEDLINE databases were searched for eligible studies between January 2000 and October 2015. Studies describing outcomes of OSR, TEVAR, B/FEVAR, or all, for CBAD patients initially treated with medical therapy, were included. Primary endpoints were early mortality, and one-year and five-year survival. Secondary endpoints included occurrence of complications. Furthermore, a Time until Treatment Equipoise (TUTE) graph was constructed. Results Thirty-five articles were selected for systematic review. A total of 1081 OSR patients, 1397 TEVAR patients and 61 B/FEVAR patients were identified. Early mortality ranged from 5.6% to 21.0% for OSR, 0.0% to 13.7% for TEVAR, and 0.0% to 9.7% for B/FEVAR. For OSR, one-year and five-year survival ranged 72.0%-92.0% and 53.0%-86.7%, respectively. For TEVAR, one-year survival was 82.9%-100.0% and five-year survival 70.0%-88.9%. For B/FEVAR only one-year survival was available, ranging between 76.4% and 100.0%. Most common postoperative complications included stroke (OSR 0.0%-13.3%, TEVAR 0.0%-11.8%), spinal cord ischemia (OSR 0.0%-16.4%, TEVAR 0.0%-12.5%, B/FEVAR 0.0%-12.9%) and acute renal failure (OSR 0.0%-33.3%, TEVAR 0.0%-34.4%, B/FEVAR 0.0%-3.2%). Most common long-term complications after OSR included aneurysm formation (5.8%-20.0%) and new type A dissection (1.7–2.2%). Early complications after TEVAR included retrograde dissection (0.0%-7.1%), malperfusion (1.3%–9.4%), cardiac complications (0.0%–5.9%) and rupture (0.5%–5.0%). Most common long-term complications after TEVAR were rupture (0.5%–7.1%), endoleaks (0.0%–15.8%) and cardiac complications (5.9%-7.1%). No short-term aortic rupture or malperfusion was observed after B/FEVAR. Long-term complications included malperfusion (6.5%) and endoleaks (0.0%-66.7%). Reintervention rates after OSR, TEVAR and B/FEVAR were 5.8%-29.0%, 4.3%-47.4% and 0.0%-53.3%, respectively. TUTE for OSR was 2.7 years, for TEVAR 9.9 months and for B/FEVAR 10.3 months. Conclusion We found a limited early survival benefit of standard TEVAR over OSR for CBAD. Complication rates after TEVAR are higher, but complications after OSR are usually more serious. Initial experiences with B/FEVAR show its feasibility, but long-term results are needed to compare it to OSR and standard TEVAR. We conclude that optimal treatment of CBAD remains debatable and merits a patient specific decision. TUTE seems a feasible and useful tool to better understand management outcomes of CBAD.

Visceral Malperfusion in Aortic Dissection: The Michigan Experience

One of the most dreaded complications of acute aortic dissection is end-organ malperfusion. We summarize current evidence and describe our treatment paradigm in the setting of malperfusion in aortic dissection. Given the difficulty with identifying isolated visceral malperfusion in aortic dissection, both in the literature as well as in our practice, we have broadened the discussion to include data examining the presentation complex of malperfusion, particularly if mesenteric ischemia is identified. The approach to treating malperfusion syndrome is different depending on whether the patient presents with type A dissection vs type B dissection with malperfusion. Although thoracic endovascular aortic repair has emerged as the dominant strategy for resolving malperfusion for complicated type B dissection, fenestration may still have a role in its treatment. In contrast, for type A aortic dissection presenting with visceral malperfusion, the concept of operative repair after restoration of end-organ perfusion has been proposed with increasing frequency in recent reports. At the University of Michigan, we apply a patient-specific algorithm, based on the presence of malperfusion with end-organ dysfunction. In those patients presenting with visceral malperfusion, we prefer to first fenestrate, await resolution of the malperfusion syndrome and then perform central aortic repair. We recognize that other groups have implemented similar algorithms to reduce the dismal results of operative procedures in this cohort. However, the most appropriate period of delay remains unknown and there is a persistent risk of rupture before repair is performed. Future studies should be performed to determine whether these various treatment paradigms have merit.

Assessment of CardiOvascular Remodelling following Endovascular aortic repair through imaging and computation: the CORE prospective observational cohort study protocol

Introduction Thoracic aortic stent grafts are orders of magnitude stiffer than the native aorta. These devices have been associated with acute hypertension, elevated pulse pressure, cardiac remodelling and reduced coronary perfusion. However, a systematic assessment of such cardiovascular effects of thoracic endovascular aortic repair (TEVAR) is missing. The CardiOvascular Remodelling following Endovascular aortic repair (CORE) study aims to (1) quantify cardiovascular remodelling following TEVAR and compare echocardiography against MRI, the reference method; (2) validate computational modelling of cardiovascular haemodynamics following TEVAR using clinical measurements, and virtually assess the impact of more compliant stent grafts on cardiovascular haemodynamics; and (3) investigate diagnostic accuracy of ECG and serum biomarkers for cardiac remodelling compared to MRI. Methods and analysis This is a prospective, nonrandomised, observational cohort study. We will use MRI, CT, echocardiography, intraluminal pressures, ECG, computational modelling and serum biomarkers to assess cardiovascular remodelling in two groups of patients with degenerative thoracic aneurysms or penetrating aortic ulcers: (1) patients managed with TEVAR and (2) control patients managed with medical therapy alone. Power analysis revealed a minimum total sample size of 20 patients (α=0.05, power=0.97) to observe significant left ventricular mass increase following TEVAR after 1 year. Consequently, we will include 12 patients in both groups. Advanced MRI sequences will be used to assess myocardial and aortic strain and distensibility, myocardial perfusion and aortic flow. ECG, echocardiography and serum biomarkers will be collected and compared against the imaging data. Computational models will be constructed from each patient imaging data, analysed and validated. All measurements will be collected at baseline (prior to TEVAR) and 1-year follow-up. The expected study period is 3 years. Ethics and dissemination This study has been approved by the University of Michigan IRB. The results will be disseminated through scientific journals and conference presentations. Trial registration number NCT02735720.

A review of follow-up outcomes after elective endovascular repair of degenerative thoracic aortic aneurysms

Long-term outcomes of elective thoracic endovascular aortic repair (TEVAR) for degenerative thoracic aortic aneurysms (TAA) are not well defined. A review of the literature on the follow-up outcomes of elective TEVAR for degenerative TAA resulted in 22 relevant articles. Two- and five-year freedom from aneurysm-related death varied between 93.0% and 100.0%, and 82.4% to 92.7%, respectively. Two-year and five-year all-cause survival ranged between 68.0% and 97.2% and 47.0% to 78.0%, respectively. Follow-up ranged between 17.3 and 66.0 months. Most common endograft-related complication was endoleak, with reported rate between 1.4% and 14.8% during six months up to five years of follow-up. Endovascular reinterventions were reported in 0.0–32.3%, secondary open surgery was needed in 0.0% to 4.7% during follow-up. Aneurysm-related survival rates after elective TEVAR for degenerative TAA are acceptable. However, reported incidences of endograft-related complications vary considerably in the literature, but the majority can be managed with conservative treatment or additional endovascular procedures.

Biomechanical Changes After Thoracic Endovascular Aortic Repair in Type B Dissection: A Systematic Review

Thoracic endovascular aortic repair (TEVAR) has evolved into an established treatment option for type B aortic dissection (TBAD) since it was first introduced 2 decades ago. Morbidity and mortality have decreased due to the minimally invasive character of TEVAR, with adequate stabilization of the dissection, restoration of true lumen perfusion, and subsequent positive aortic remodeling. However, several studies have reported severe setbacks of this technique. Indeed, little is known about the biomechanical behavior of implanted thoracic stent-grafts and the impact on the vascular system. This study sought to systematically review the performance and behavior of implanted thoracic stent-grafts and related biomechanical aortic changes in TBAD patients in order to update current knowledge and future perspectives.

Impact of thoracic endovascular aortic repair on radial strain in an ex vivo porcine model

Objectives To quantify the impact of thoracic endovascular aortic repair (TEVAR) on radial aortic strain with the aim of elucidating stent-graft-induced stiffening and complications. Methods Twenty fresh thoracic porcine aortas were connected to a mock circulatory loop driven by a centrifugal flow pump. A high-definition camera captured diameters at five different pressure levels (100, 120, 140, 160, and 180 mmHg), before and after TEVAR. Three oversizing groups were created: 0-9% ( n  = 7), 10-19% ( n  = 6), and 20-29% ( n  = 6). Radial strain (or deformation) derived from diameter amplitude divided by baseline diameter at 100 mmHg. Uniaxial tensile testing evaluated Youngs moduli of the specimens. Results Radial strain was reduced after TEVAR within the stented segment by 49.4 ± 24.0% ( P  < 0.001). As result, a strain mismatch was observed between the stented segment and the proximal non-stented segment (7.0 ± 2.5% vs 11.8 ± 3.9%, P  < 0.001), whereas the distal non-stented segment was unaffected ( P  = 0.99). Stent-graft oversizing did not significantly affect the amount of strain reduction ( P  = 0.30). Tensile testing showed that the thoracic aortas tended to be more elastic proximally than distally ( P  = 0.11). Conclusions TEVAR stiffened the thoracic aorta by 2-fold. Such segmental stiffening may diminish the Windkessel function considerably and might be associated with TEVAR-related complications, including stent-graft-induced dissection and aneurysmal dilatation. These data may have implications for future stent-graft design, in particular for TEVAR of the highly compliant proximal thoracic aorta.

Standardized Protocol to Analyze Computed Tomography Imaging of Type B Aortic Dissections

Purpose: To propose a standard measuring protocol for type B aortic dissections so as to improve comparability between studies reporting aortic dimensions. Methods: Fifteen computed tomography (CT) scans of type B aortic dissections were measured with a standard protocol by 2 independent observers using postprocessing software. The following parameters were assessed: true, false, and total lumen diameter; true and false lumen volume; and entry tear size, location, and number. Diameters were measured in a perpendicular plane at 2, 10, and 20 cm from the left subclavian artery and 5 cm from the most distal renal artery. True lumen volume was assessed from the left subclavian artery to the aortic bifurcation, while the false lumen volume was from the start to end up to the aortic bifurcation. Entry tear location was assessed in relation to the left subclavian artery. Intra- and interobserver repeatability and agreement were evaluated using the Bland-Altman method, an a priori set of acceptable differences, and Lin’s concordance correlation coefficient (LCCC). Results: Intra- and interobserver mean differences for aortic diameter and true and false lumen volumes were generally within the limits of agreement and the a priori differences; the LCCC showed excellent agreement. Entry tear location, size, and number were difficult to measure in a repeatable manner, with inconsistent correlation coefficients, especially between the 2 observers. Conclusion: This protocol showed acceptable repeatability for aortic diameter and aortic volume measurements. Assessment of entry tears proved challenging and associated with less favorable results. Additionally, investigators are urged to be more transparent regarding the measurement methodology used in studies describing aortic dimensions.