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Updated: Aug 4, 2025
Estimating Bilateral Atrial Function by Cardiovascular Magnetic Resonance Feature Tracking in Patients with Paroxysmal Atrial Fibrillation
Published on: July 20, 2022
Subject-specific factors affecting particle residence time distribution of left atrial appendage in atrial
Soroosh Sanatkhani1, Sotirios Nedios2,3,4, Prahlad G Menon1
1Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, United States.
Insights
Atrial fibrillation (AF) stroke risk can be better assessed using left atrial appendage (LAA) blood flow dynamics. Mean residence time (t) and asymptotic concentration (C∞) are influenced by cardiac output and hematocrit, not flow patterns.
Area of Science:
- Cardiovascular Research
- Biomedical Engineering
- Computational Fluid Dynamics
Background:
- Atrial fibrillation (AF) is a common arrhythmia linked to thrombus formation in the left atrial appendage (LAA).
- Current stroke risk scores like CHA2DS2-VASc do not incorporate LAA morphology or hemodynamics.
- Previous research indicated that LAA residence time distribution (RTD) metrics (mean residence time, t; asymptotic concentration, C∞) may enhance stroke risk stratification.
Purpose of the Study:
- To investigate the impact of pulmonary vein flow waveform pulsatility, non-Newtonian blood rheology, hematocrit levels, and simulation duration on LAA t and C∞.
- To refine the understanding of factors influencing blood-borne particle residence within the LAA.
- To explore the potential of RTD parameters for improved stroke risk assessment in AF patients.
Main Methods:
- Subject-specific data from 25 AF patients, including left atrial (LA) and LAA CT scans, cardiac output (CO), heart rate, and hematocrit, were collected.
- Computational fluid dynamics (CFD) analyses were performed to calculate LAA t and C∞.
- Simulations were conducted to assess the effects of varying hemodynamic and rheological parameters.
Main Results:
- LAA t and C∞ were significantly influenced by cardiac output but not by the temporal pattern of inlet flow.
- Increasing hematocrit levels led to higher LAA t and C∞.
- Non-Newtonian blood rheology resulted in higher calculated indices (t and C∞) compared to Newtonian models at equivalent hematocrit levels.
- Reliable calculation of LAA t and C∞ requires a minimum of 20,000 seconds of CFD simulation time.
Conclusions:
- Subject-specific LA and LAA geometries are crucial for accurate RTD quantification.
- Cardiac output and hematocrit levels are essential parameters for determining blood cell retention within the LAA.
- The study highlights the importance of considering rheological properties and simulation duration for reliable LAA hemodynamic analysis in AF patients.
Background:
Atrial fibrillation (AF) is a prevalent arrhythmia, that causes thrombus formation, ordinarily in the left atrial appendage (LAA). The conventional metric of stroke risk stratification, CHA2DS2-VASc score, does not account for LAA morphology or hemodynamics. We showed in our previous study that residence time distribution (RTD) of blood-borne particles in the LAA and its associated calculated variables (i.e., mean residence time, t , and asymptotic concentration, C ∞) have the potential to improve CHA2DS2-VASc score. The purpose of this research was to investigate the effects of the following potential confounding factors on LAA t and C ∞: (1) pulmonary vein flow waveform pulsatility, (2) non-Newtonian blood rheology and hematocrit level, and (3) length of the simulation.
Methods:
Subject-Specific data including left atrial (LA) and LAA cardiac computed tomography, cardiac output (CO), heart rate, and hematocrit level were gathered from 25 AF subjects. We calculated LAA t and C ∞ based on series of computational fluid dynamics (CFD) analyses.
Results:
Both LAA t and C ∞ are significantly affected by the CO, but not by temporal pattern of the inlet flow. Both LAA t and C ∞ increase with increasing hematocrit level and both calculated indices are higher for non-Newtonian blood rheology for a given hematocrit level. Further, at least 20,000 s of CFD simulation is needed to calculate LAA t and C ∞ values reliably.
Conclusions:
Subject-specific LA and LAA geometries, CO, and hematocrit level are essential to quantify the subject-specific proclivity of blood cell tarrying inside LAA in terms of the RTD function.
