Modelling Virchow's Triad to Improve Stroke Risk Assessment in Atrial Fibrillation Patients

Abstract

Atrial fibrillation $(AF)$ is associated with a significantly increased risk of stroke due to the presence of three pro-thrombotic mechanisms known as Virchow's triad - blood stasis, endothelial damage and hypercoagulability - which primarily occur in the left atrial appendage $(LAA)$. Insilica evaluation of each factor can improve upon the current empirical stroke risk stratification for AF patients. Computational fluid dynamics simulations were performed on two patient-specific models of the left atrium, one in sinus rhythm $(SR)$ and one in $AF$ to quantify blood stasis and metrics of endothelial damage. Hypercoagulability was assessed by solving reaction-diffusion-convection equations for thrombin, fibrinogen and fibrin - three key clotting proteins, and varying initial concentrations of fibrinogen in accordance with clinical literature. An original grading system is proposed $(A= low, B = moderate, C=high$ risk) for each component of the triad to form a patient-specific risk profile. The $SR$ patient had a risk profile of $[A,\ B, A]$ showing a low-moderate risk of thrombus formation, while the $AF$ patient had $[C, B, C]$, indicating a very high risk of thrombus formation and increased potential for stroke. This novel modelling approach encapsulates all fundamental mechanisms of thrombus formation and may be used to improve stroke risk assessment for $AF$ patients.