Analysis of real-time three dimensional transesophageal echocardiography in the assessment of left atrial appendage function in patients with atrial fibrillation

Impact of left atrial wall motion assumptions in fluid simulations on proposed predictors of thrombus formation

Atrial fibrillation (AF) poses a significant risk of stroke due to thrombus formation, which primarily occurs in the left atrial appendage (LAA). Medical image-based computational fluid dynamics (CFD) simulations can provide valuable insight into patient-specific hemodynamics and could potentially enhance personalized assessment of thrombus risk. However, the importance of accurately representing the left atrial (LA) wall dynamics has not been fully resolved. In this study, we compared four modeling scenarios; rigid walls, a generic wall motion based on a reference motion, a semi-generic wall motion based on patient-specific motion, and patient-specific wall motion based on medical images. We considered a LA geometry acquired from 4D computed tomography during AF, systematically performed convergence tests to assess the numerical accuracy of our solution strategy, and quantified the differences between the four approaches. The results revealed that wall motion had no discernible impact on LA cavity hemodynamics, nor on the markers that indicate thrombus formation. However, the flow patterns within the LAA deviated significantly in the rigid model, indicating that the assumption of rigid walls may lead to errors in the estimated risk factors. In contrast, the generic, semi-generic, and patient-specific cases were qualitatively similar. The results highlight the crucial role of wall motion on hemodynamics and predictors of thrombus formation, and also demonstrate the potential of using a generic motion model as a surrogate for the more complex patient-specific motion. While the present study considered a single case, the employed CFD framework is entirely open-source and designed for adaptability, allowing for integration of additional models and generic motions.

Finding low CHA2DS2-VASc scores unreliable? Why not give morphological and hemodynamic methods a try?

Patients with atrial fibrillation (AF) suffer from a high risk of thrombosis. Currently, the CHA2DS2-VASc score is the most widely used tool for risk stratification in patients with AF, but it has disappointing accuracy and limited predictive value, especially in those with low scores. Thrombi in patients with AF mostly grow in their left atrial appendages (LAA), which is directly related to the abnormal morphology of the LAA or the left atrium and the unusual hemodynamic state around LAA, which may sensitively evaluate the risk of thrombosis complications in patients with AF and bring bases to clinical plans of medication and operation. Therefore, we investigated the research progress of hemodynamic and morphological studies about the predictive value of thrombosis risk in patients with AF, intending to discuss the prediction potential of morphological and hemodynamic indexes when compared with the presently used CHA2DS2-VASc system and how to build a more precise thromboembolic event prediction model for patients with AF.

Impact of atrial fibrillation on left atrium haemodynamics: A computational fluid dynamics study

We analyse the haemodynamics of the left atrium, highlighting differences between healthy individuals and patients affected by atrial fibrillation. The computational study is based on patient-specific geometries of the left atria to simulate blood flow dynamics. We design a novel procedure to compute the boundary data for the 3D haemodynamic simulations, which are particularly useful in absence of data from clinical measurements. With this aim, we introduce a parametric definition of atrial displacement, and we use a closed-loop lumped parameter model of the whole cardiovascular circulation conveniently tuned on the basis of the patient's characteristics. We evaluate several fluid dynamics indicators for atrial haemodynamics, validating our numerical results in terms of clinical measurements; we investigate the impact of geometric and clinical characteristics on the risk of thrombosis. To highlight the correlation of thrombus formation with atrial fibrillation, according to medical evidence, we propose a novel indicator: age stasis. It arises from the combination of Eulerian and Lagrangian quantities. This indicator identifies regions where slow flow cannot properly rinse the chamber, accumulating stale blood particles, and creating optimal conditions for clots formation.

Assessment of cardiac biomarkers (troponin, B-type natriuretic peptide, and D-dimer) in patients with non-valvular atrial fibrillation and stroke

OBJECTIVES

Atrial fibrillation (AF) is the most common arrhythmia treated in clinical practice and the association of this arrhythmia with stroke has long been recognized. The combination of associated factors to identify stroke risk is still unclear; therefore, we aimed to determine the association between additional risk factors for non-valvular AF (NVAF) and the first onset stroke patients and investigate the predictive ability of additional risks factors such as cardiac biomarkers and AF status for odds of incident stroke.

MATERIALS AND METHODS

We included 455 patients who suffered from NVAF divided into two distinct groups (case-control observational study). Those two groups were based on whether the patients were having a first onset stroke (stroke group) or not having a stroke (non-stroke group). We made the baseline characteristic of our sample group from the substantial evidence of risk factors, lifestyle, and type of AF; to controversial risk described in the new international guideline of AF.

RESULTS

Statistically revealed that heart failure, coronary disease, cigarette smoking, type of AF, warfarin treatment, high sensitive troponin, and B-type natriuretic peptide (BNP) are associated with stroke in NVAF patients (P < 0.05). Otherwise, age, sex, hypertension, kidney disease, diabetes, thyroid disease, alcohol intake, season, aspirin, and D-dimer medication were not associated with stroke (P > 0.05). Multivariate analysis of age, smokers, coronary heart disease, heart failure, high sensitive troponin level, BNP, permanent AF, and warfarin was associated (P < 0.05). The combination of biomarkers with the clinical features can be useful (CHA2DS2-VASC/BS) for the prediction of stroke than CHA2DS2-VASC alone (P < 0.05).

CONCLUSION

Impact of all associated factors and biological markers as additional risk factors may carry a synergy in this life-threatening event. In addition, may hold a clinical role to redefine and predict stroke events better than the current CHA2DS2-VASC.