Imaging characteristics of acute type A aortic dissection and candidacy for repair with ascending aortic endografts

Anatomic feasibility of a modular Endo-Bentall stent graft system for type A aortic dissection

OBJECTIVE

The implementation of thoracic endovascular aortic repair in patients with type A aortic dissection has been strictly constrained due to the pulsatile movement and distensibility and the insufficient length of landing zones on ascending aorta. The most prevalent anatomical limitation is the insufficient length of proximal and distal landing zones. We propose a modularly designed Endo-Bentall stent graft system to broaden the scope of thoracic endovascular aortic repair in the ascending aorta by covering intimal tears in the aortic root and ascending aorta and reconstructing coronary arteries. This study was conducted to assess the anatomical feasibility of a novel stent graft design.

METHODS

In this study, we included 152 patients with type A aortic dissection for image measurement and analysis. All computed tomography angiography images were assessed on a 3mensio Workstation version 10.2 (3mensio Medical Imaging B.V.) utilizing the centerline method. We compared the diameters and lengths at various planes in relation to the proposed anatomical criteria for the modular Endo-Bentall stent graft system.

RESULTS

The patients were predominantly male (67.1%), with a median age of 56.5 years (interquartile range, 50.0-65.0 years). Among all aortic dissections, 91.5% extended proximally to the sinotubular junction, whereas only 8.6% were restricted to the tubular ascending aorta. The median perimeter-derived diameter of the aortic annulus was 24.1 mm. The median maximum aortic diameter at the sinotubular junction and brachiocephalic trunk were 44.6 mm and 43.5 mm, respectively. The median height of the left coronary artery, right coronary artery, and sinus of Valsalva were 12.7 mm, 16.7 mm, and 28.4 mm, respectively. After applying exclusion criteria, 66.4% of all patients were anatomically eligible for the modular Endo-Bentall stent graft system. A total of 85.1% of patients were suitable for stent grafts with lengths of 70 mm, 80 mm, or 90 mm. Both antegradely and retrogradely tapered stent grafts were required, according to the diameter differences between the STJ and brachiocephalic trunk.

CONCLUSIONS

Utilizing the modular Endo-Bentall stent-graft design, approximately two-thirds of patients with type A aortic dissection are anatomically eligible for endovascular repair. Further animal studies are required to optimize the device design.

TEVAR for aortic arch lesions combining physician-modified endograft and in-situ fenestration

BACKGROUND

The aim of this retrospective study was to investigate the outcomes of combining physician-modified endograft (PMEG) and in-situ fenestration (ISF) for aortic arch repair.

METHODS

A retrospective analysis was performed in 12 patients with aortic arch pathologies who underwent thoracic endovascular aortic repair with PMEG and ISF between June 2019 and February 2020.

RESULTS

Revascularizations of supra-aortic arteries were successfully performed in 91.7% patients (11/12). One patient with aberrant right subclavian artery was unsuccessful because of tortuosity and sharp angle. One patient received endovascular exclusion by Viabahn due to artery injury of the femoral access. During the follow-up (mean 22.7 months), one patient underwent Bentall surgery because of retrograde type A aortic dissection, and one patient received coils embolization due to occurrence of a type I endoleak. In addition, one patient died of myocardial infarction 13 months after surgery. Results obtained after computed tomography angiography confirmed patency of all the supra-aortic arteries.

CONCLUSIONS

Combining PMEG and ISF could be a feasible option for aortic arch lesions in selected patients. Long-term durability concerns require further evaluation.

Endovascular Intervention for Aortic Dissection Is "Ascending"

Ascending aorta diseases represent an important cause of mortality worldwide. Notably, acute and chronic thoracic aorta pathologies have increased during the last years, but medical therapy does not seem to influence their natural history. Currently, although open surgery is the first choice of treatment, many patients are still rejected or have poor outcomes. In this scenario, endovascular treatment is raised as a valuable option. In this review we describe the limitations of conventional surgery and the state-of-art of endovascular ascending aorta repair.

Regional wall stress differences on tricuspid aortic valve-associated ascending aortic aneurysms

OBJECTIVES

Ascending thoracic aortic aneurysms (aTAAs) carry a risk of acute type A dissection. Elective repair guidelines are based on diameter, but complications often occur below diameter threshold. Biomechanically, dissection can occur when wall stress exceeds wall strength. Aneurysm wall stresses may better capture dissection risk. Our aim was to investigate patient-specific aTAA wall stresses associated with a tricuspid aortic valve (TAV) by anatomic region.

METHODS

Patients with aneurysm diameter ≥4.0 cm underwent computed tomography angiography. Aneurysm geometries were reconstructed and loaded to systemic pressure while taking prestress into account. Finite element analyses were conducted to obtain wall stress distributions. The 99th percentile longitudinal and circumferential stresses were determined at systole. Wall stresses between regions were compared using one-way analysis of variance with post hoc Tukey HSD for pairwise comparisons.

RESULTS

Peak longitudinal wall stresses on aneurysms (n = 204) were 326 [standard deviation (SD): 61.7], 246 (SD: 63.4) and 195 (SD: 38.7) kPa in sinuses of Valsalva, sinotubular junction (STJ) and ascending aorta (AscAo), respectively, with significant differences between AscAo and both sinuses (P < 0.001) and STJ (P < 0.001). Peak circumferential wall stresses were 416 (SD: 85.1), 501 (SD: 119) and 340 (SD: 57.6) kPa for sinuses, STJ and AscAo, respectively, with significant differences between AscAo and both sinuses (P < 0.001) and STJ (P < 0.001).

CONCLUSIONS

Circumferential and longitudinal wall stresses were greater in the aortic root than AscAo on aneurysm patients with a TAV. Aneurysm wall stress magnitudes and distribution relative to respective regional wall strength could improve understanding of aortic regions at greater risk of dissection in a particular patient.

Regional biomechanical and failure properties of healthy human ascending aorta and root

PURPOSE

Aortic dissection (AD) is a life-threatening event that occurs when the intimal entry tear propagates and separates inner from outer layers of the aorta. Diameter, the current criterion for aneurysm repair, is far from ideal and additional evidence to optimize clinical decision would be extremely beneficial. Biomechanical investigation of the regional failure properties of aortic tissue is essential to understand and proactively prevent AD. We previously studied biaxial mechanical properties of healthy human aorta. In this study, we investigated the regional failure properties of healthy human ascending aorta (AscAo) including sinuses of Valsalva (SOV), and sinotubular junction (STJ).

RESULTS

A total of 430 intact tissue samples were harvested from 19 healthy donors whose hearts were excluded from heart transplantation. The donors had mean age of 51 ± 11.7 years and nearly equal gender distribution. Samples were excised from aortic regions and subregions at defined locations. Tissue strips were subjected to either biaxial or uniaxial failure testing. Wall thickness varied regionally being thickest at AscAo (2.08 ± 0.66 mm) and thinnest at SOV (1.46 ± 0.31 mm). Biaxial testing demonstrated hyperplastic behavior of aortic tissues. Posterior and lateral STJ subregions were found to be stiffer than anterior and medial subregions in both circumferential and longitudinal directions. Failure stresses were significantly higher in the circumferential than longitudinal directions in each subregion of AscAo, STJ, and SOV. Longitudinal failure stresses were significantly greater in AscAo than those in STJ or SOV. Longitudinal failure stresses in AscAo were much smaller anteriorly than posteriorly, and medially than laterally.

CONCLUSIONS

The finding of weakest region at the sinotubular junction along the longitudinal direction corroborates clinical observations of that region being commonly involved as the initial site of intimal tear in aortic dissections. Failure stretch ratios correlated to elastic modulus at each region. Furthermore, strong correlation was seen between STJ failure stresses and elastic modulus at physiological pressure along both circumferential and longitudinal directions. Correlating in-vivo aortic elastic modulus based on in-vivo imaging with experimentally determined elastic modulus at physiological pressure and failure stresses may potentially provide valuable information regarding aortic wall strength. Better understanding of aortic biomechanics in normal physiologic and aneurysmal pathologic states may aid in determining risk factors for predicting dissection in patient-specific fashion.