One weapon, two blows in the war against the thrombus

A three-dimensional phase-field model for multiscale modeling of thrombus biomechanics in blood vessels

Mechanical interactions between flowing and coagulated blood (thrombus) are crucial in dictating the deformation and remodeling of a thrombus after its formation in hemostasis. We propose a fully-Eulerian, three-dimensional, phase-field model of thrombus that is calibrated with existing in vitro experimental data. This phase-field model considers spatial variations in permeability and material properties within a single unified mathematical framework derived from an energy perspective, thereby allowing us to study effects of thrombus microstructure and properties on its deformation and possible release of emboli under different hemodynamic conditions. Moreover, we combine this proposed thrombus model with a particle-based model which simulates the initiation of the thrombus. The volume fraction of a thrombus obtained from the particle simulation is mapped to an input variable in the proposed phase-field thrombus model. The present work is thus the first computational study to integrate the initiation of a thrombus through platelet aggregation with its subsequent viscoelastic responses to various shear flows. This framework can be informed by clinical data and potentially be used to predict the risk of diverse thromboembolic events under physiological and pathological conditions.

Atrial fibrillation and risk of stroke: a nationwide cohort study

AIM

Although the relation between stroke risk factors and stroke in patients with atrial fibrillation (AF) has been extensively examined, only few studies have explored the association of AF and the risk of ischaemic stroke/systemic thromboembolism/transient ischaemic attack (stroke/TE/TIA) in the presence of concomitant stroke risk factors.

METHODS AND RESULTS

From nationwide registries, all persons who turned 50, 60, 70, or 80 from 1997 to 2011 were identified. Persons receiving warfarin were excluded. The absolute risk of stroke/TE/TIA was reported for a 5-year period, as was the absolute risk ratios for AF vs. no AF according to prior stroke and the number of additional risk factors. The study cohort comprised of 3 076 355 persons without AF and 48 189 with AF. For men aged 50 years, with no risk factors, the 5-year risk of stroke was 1.1% (95% confidence interval 1.1-1.1); with AF alone 2.5% (1.8-3.2); with one risk factor and no prior stroke or AF 2.5% (2.3-2.7); and with one factor, no prior stroke and AF 2.9% (1.4-4.3). In men aged 50 years with prior stroke as the only risk factor, 5-year risk was 10.2% (9.1-11.3). In men aged 70 years, the corresponding risks were 4.8% (4.7-4.9), 6.8% (5.7-7.9), 6.6% (6.3-6.8), 8.7 (7.4-9.9), and 19.1% (18.1-20.1), respectively. In women aged 50 years, the risk was of 0.7% (0.7-0.7), 2.1% (0.9-3.2), 1.6% (1.4-1.8), 4.1% (0.6-7.6), and 7.2% (6.3-8.2), respectively, and in women aged 70 years 3.4% (3.3-3.5), 8.2% (7.0-9.5), 4.6% (4.4-4.8), 9.1% (7.5-10.6), and 15.4% (14.5-16.4), respectively.

CONCLUSIONS

Stroke/TE/TIA risk was particularly increased when prior stroke/TE/TIA was present. Atrial fibrillation is associated with an increase in risk of stroke/TE/TIA in the absence of other risk factors but only a moderate increase in risk when other risk factors are present.