Sensitivity Analysis of a Phenomenological Thrombosis Model and Growth Rate Characterisation

Aortic dissection is a severe cardiovascular disease caused by the occurrence of a tear in the aortic wall. As a result, the blood penetrates the wall and makes a new blood channel called the false lumen. The haemodynamic conditions in the false lumen may contribute to the formation of thrombi, which influence the patient's diagnosis and outcomes. In this study, the focus is on a haemodynamic-based model of thrombus formation. Since the model construction entails uncertainties in the model parameters, a variance-based sensitivity analysis is performed. Thrombus formation at a backward-facing step is considered as a benchmark for the numerical simulations and sensitivity analysis. This geometry is capable of representing the main contributions of the model in thrombus formation. The study aims at improving the understanding of the model's structure and at preparing model simplifications to enable efficient patient-specific simulations in the future. A polynomial chaos expansion is employed as a surrogate model, from which the quantitative sensitivity indices are derived. In this study, nine model parameters are selected, whose proper values are not well known. The model responses taken into account are the maximum volume fraction of thrombus, its time development, and the thrombus growth rate. The results show that the model lends itself to model reduction since some of the model parameters show little to no influence on the model's outputs. A threshold value related to the concentration of bounded platelets and the bounded platelets reaction rate are identified as the key input parameters dominating the thrombus model predictions in the current geometry. Furthermore, the introduced thrombus characteristic growth time is driven by both the aforementioned variables.