Stroke Propensity Is Increased under Atrial Fibrillation Hemodynamics: A Simulation Study

Abstract

Atrial fibrillation (AF) is the most common sustained dysfunction in heart rhythm clinically and has been identified as an independent risk factor for stroke through formation and embolization of thrombi. AF is associated with reduced cardiac output and short and irregular cardiac cycle length. Although the effect of AF on cardiac hemodynamic parameters has been reported, it remains unclear how the hemodynamic perturbations affect the potential embolization of blood clots to the brain that can cause stroke. To understand stroke propensity in AF, we performed computer simulations to describe trajectories of blood clots subject to the aortic flow conditions that represent normal heart rhythm and AF. Quantitative assessment of stroke propensity by blood clot embolism was carried out for a range of clot properties (e.g., 2–6 mm in diameter and 0–0.8 m/s ejection speed) under normal and AF flow conditions. The simulations demonstrate that the trajectory of clot is significantly affected by clot properties as well as hemodynamic waveforms which lead to significant variations in stroke propensity. The predicted maximum difference in stroke propensity in the left common carotid artery was shown to be about 60% between the normal and AF flow conditions examined. The results suggest that the reduced cardiac output and cycle length induced by AF can significantly increase the incidence of carotid embolism. The present simulations motivate further studies on patient-specific risk assessment of stroke in AF.

Role of Aortic Geometry on Stroke Propensity based on Simulations of Patient-Specific Models

“…In other words, elevated stroke propensity by AF was shown to be evident in some of the aortic configurations (Fig. 4A ) which is consistent in our previous observation 17 while such pattern was not observed in other aortic structures (Fig. 4B ).…”

“…It has been previously demonstrated that the motion of a blood clot in blood flow is multifaceted such that the trajectory of a clot is governed by the interplay between hemodynamics and clot properties 17 . Despite such complexities, however, the simulations show that pressure gradient force can be a dominant factor that determines the trajectory of a clot and thus affects the stroke propensity (Fig.…”

“…The vascular surface was smoothed and simplified by MeshLab (an open source 3D mesh processing software) to remove noise. The tetrahedral computational mesh was constructed using an ANSYS meshing tool such that mesh density was commensurate with previous studies 17 , 28 . This was done to ensure mesh-independent solutions that capture complex flow patterns in aortic arch configuration especially near curved and branching regions.…”

“…Indeed, it has been shown that AF may lead to a broad spectrum of abnormal cardiac hemodynamic parameters 13 – 16 . We have recently shown that various aspects of AF hemodynamics (e.g., reduced cardiac output and cycle length) affect the trajectory of a cardiogenic blood clot transported into the carotid artery and embolic propensity in an idealized aortic arch model 17 .…”

Anti-arrhythmic strategies for atrial fibrillation

“…Others have used biophysical modeling and simulation to investigate how hemodynamic perturbations affect the potential embolization of blood clots that ultimately cause stroke. Results suggest that these reduce cardiac output and cycle length induced by AF can significant increase incidence of embolism (Choi et al 2013). The same group recently extended their work to simulate a stroke-prevention device designed to deflect a blood clot.…”