Endovascular treatment for chronic type B aortic dissection: current opinions

Patient-Specific Haemodynamic Analysis of Virtual Grafting Strategies in Type-B Aortic Dissection: Impact of Compliance Mismatch

INTRODUCTION

Compliance mismatch between the aortic wall and Dacron Grafts is a clinical problem concerning aortic haemodynamics and morphological degeneration. The aortic stiffness introduced by grafts can lead to an increased left ventricular (LV) afterload. This study quantifies the impact of compliance mismatch by virtually testing different Type-B aortic dissection (TBAD) surgical grafting strategies in patient-specific, compliant computational fluid dynamics (CFD) simulations.

MATERIALS AND METHODS

A post-operative case of TBAD was segmented from computed tomography angiography data. Three virtual surgeries were generated using different grafts; two additional cases with compliant grafts were assessed. Compliant CFD simulations were performed using a patient-specific inlet flow rate and three-element Windkessel outlet boundary conditions informed by 2D-Flow MRI data. The wall compliance was calibrated using Cine-MRI images. Pressure, wall shear stress (WSS) indices and energy loss (EL) were computed.

RESULTS

Increased aortic stiffness and longer grafts increased aortic pressure and EL. Implementing a compliant graft matching the aortic compliance of the patient reduced the pulse pressure by 11% and EL by 4%. The endothelial cell activation potential (ECAP) differed the most within the aneurysm, where the maximum percentage difference between the reference case and the mid (MDA) and complete (CDA) descending aorta replacements increased by 16% and 20%, respectively.

CONCLUSION

This study suggests that by minimising graft length and matching its compliance to the native aorta whilst aligning with surgical requirements, the risk of LV hypertrophy may be reduced. This provides evidence that compliance-matching grafts may enhance patient outcomes.

Remodeling, Reintervention, and Survival After Endovascular Repair of Chronic Type B Dissection

BACKGROUND

The efficacy of thoracic endovascular aortic repair (TEVAR) of chronic type B aortic dissection (cTBAD) is controversial. Only limited evidence describes temporal anatomic changes after TEVAR for cTBAD and their relationship to outcomes. We sought to investigate early aortic remodeling events after TEVAR for cTBAD with thoracic aneurysm and determine the association with reintervention and survival.

METHODS

Records from 95 cTBAD patients undergoing TEVAR from 2005 to 2017 were reviewed. Using 3-dimensional centerline analysis, anatomic phenotyping of the thoracoabdominal aorta was performed. Reverse aortic remodeling (RAR) was defined by a ≥5-mm reduction in maximal thoracic aortic diameter. Kaplan-Meier analysis estimated freedom from reintervention and survival.

RESULTS

Visceral segment dissection involvement was present in 89% of patients (n = 85), and the mean preoperative thoracic diameter was 63 mm (SD, 10). Complete thoracic false lumen thrombosis occurred in 71% of patients (n = 67), whereas abdominal false lumen thrombosis was documented in 60% (n = 57) by 6 months. RAR occurred in 41%. Aortic reintervention rate was 39% (n = 37). The 1- and 3-year freedom from reintervention was significantly higher in subjects experiencing early RAR (log-rank P = .02), but reintervention did not impact overall survival (log-rank P = .9). Similarly, overall survival was similar between patients with or without RAR (log-rank P = .4).

CONCLUSIONS

Early RAR is associated with decreased rates of reintervention; however, overall survival is not impacted by these changes. TEVAR for cTBAD results in a high rate of reintervention, which mandates vigilant surveillance protocols.