Aortic dissection is a major aortic catastrophe with a high morbidity and mortality risk caused by the formation of a tear in the aortic wall. The development of a second blood filled region defined as the “false lumen” causes highly disturbed flow patterns and creates local hemodynamic conditions likely to promote the formation of thrombus in the false lumen. Previous research has shown that patient prognosis is influenced by the level of thrombosis in the false lumen, with false lumen patency and partial thrombosis being associated with late complications and complete thrombosis of the false lumen having beneficial effects on patient outcomes. In this paper, a new hemodynamics-based model is proposed to predict the formation of thrombus in Type B dissection. Shear rates, fluid residence time, and platelet distribution are employed to evaluate the likelihood for thrombosis and to simulate the growth of thrombus and its effects on blood flow over time. The model is applied to different idealized aortic dissections to investigate the effect of geometric features on thrombus formation. Our results are in qualitative agreement with in-vivo observations, and show the potential applicability of such a modeling approach to predict the progression of aortic dissection in anatomically realistic geometries.

Aortic dissection causes splitting of the aortic wall layers, allowing blood to enter a ‘false lumen’ (FL). For type B dissection, a significant predictor of patient outcomes is patency or thrombosis of the FL. Yet, no methods are currently available to assess the chances of FL thrombosis. In this study, we present a new computational model that is capable of predicting thrombus formation, growth and its effects on blood flow under physiological conditions. Predictions of thrombus formation and growth are based on fluid shear rate, residence time and platelet distribution, which are evaluated through convection–diffusion–reaction transport equations. The model is applied to a patient-specific type B dissection for which multiple follow-up scans are available. The predicted thrombus formation and growth patterns are in good qualitative agreement with clinical data, demonstrating the potential applicability of the model in predicting FL thrombosis for individual patients. Our results show that the extent and location of thrombosis are strongly influenced by aortic dissection geometry that may change over time. The high computational efficiency of our model makes it feasible for clinical applications. By predicting which aortic dissection patient is more likely to develop FL thrombosis, the model has great potential to be used as part of a clinical decision-making tool to assess the need for early endovascular intervention for individual dissection patients.

Thoracic endovascular repair (TEVAR) has recently been established as the preferred treatment option for complicated type B dissection. This procedure involves covering the primary entry tear to stimulate aortic remodelling and promote false lumen thrombosis thereby restoring true lumen flow. However, complications associated with incomplete false lumen thrombosis, such as aortic dilatation and stent graft induced new entry tears, can arise after TEVAR. This study presents the application and validation of a recently developed mathematical model for patient-specific prediction of thrombus formation and growth under physiologically realistic flow conditions. The model predicts thrombosis through the evaluation of shear rates, fluid residence time and platelet distribution, based on convection-diffusion-reaction transport equations. The model was applied to 3 type B aortic dissection patients: two TEVAR cases showing complete and incomplete false lumen thrombosis respectively, and one medically treated dissection with no signs of thrombosis. Predicted thrombus growth over time was validated against follow-up CT scans, showing good agreement with in vivo data in all cases with a maximum difference between predicted and measured false lumen reduction below 8%. Our results demonstrate that TEVAR-induced thrombus formation in type B aortic dissection can be predicted based on patient-specific anatomy and physiologically realistic boundary conditions. Our model can be used to identify anatomical or stent graft related factors that are associated with incomplete false lumen thrombosis following TEVAR, which may help clinicians develop personalised treatment plans for dissection patients in the future.

Computational hemodynamics studies of aortic dissections usually combine patient-specific geometries with idealized or generic boundary conditions. In this study we present a comprehensive methodology for simulations of hemodynamics in type B aortic dissection (TBAD) based on fully patient-specific boundary conditions. Methods: Pre-operative 4D flow magnetic resonance imaging (MRI) and Doppler-wire pressure measurements (pre-and post-operative) were acquired from a TBAD patient. These data were used to derive boundary conditions for computational modelling of flow before and after thoracic endovascular repair (TEVAR). Validations of the computational results were performed by comparing predicted flow patterns with pre-TEVAR 4D flow MRI, as well as pressures with in vivo measurements. Results and Conclusion: Comparison of instantaneous velocity streamlines showed a good qualitative agreement with 4D flow MRI. Quantitative comparison of predicted pressures with pressure measurements revealed a maximum difference of 11 mmHg (-9.7%). Furthermore, our model correctly predicted the reduction of true lumen pressure from 74/115 mmHg pre-TEVAR to 64/107 mmHg post-TEVAR (diastolic/systolic pressures at entry tear level), compared to the corresponding measurements of 72/118 mmHg and 64/114 mmHg. This demonstrates that pre-TEVAR 4D flow MRI can be used to tune boundary conditions for post-TEVAR hemodynamic analyses.

This case study suggests that high stent-graft tortuosity can lead to high wall stress, which is potentially linked to the formation of SINE. Further large population-based studies are needed to confirm this preliminary finding.