Determinants of Impaired Left Atrial Hemodynamics in Paroxysmal Atrial Fibrillation: A 4D Flow MRI Study

Figures

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  Figure 1. A flowchart diagram of the patients analyzed in this project, following quality control protocols.

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  Figure 2. Data processing and analysis workflow: (A) Example of 4D-flow MRI data after application of correction steps. (B) Depiction of intracardiac flow patterns throughout the full heart volume. (C) A time-averaged phase-contrast (PC) magnetic resonance angiography (MRA) dataset is used to define left atrial (LA) anatomy, with a selected intensity threshold to enhance structural visibility; the LA is manually delineated across consecutive slices to obtain a 3D volume. (D) Stasis within the LA is subsequently quantified and visualized as maximum intensity projections from the sagittal perspective, with warmer colors (red) indicating greater stasis and cooler colors (blue) indicating reduced stasis.

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  Figure 3. Relationships between clinical measurements and the presence of left atrial stasis. Panels (A–E) display how body mass index (BMI), resting heart rate (HR), left ventricular ejection fraction (LVEF), left atrial volume index (LAVi), and hematocrit vary in relation to left atrial stasis. Each plot includes a linear regression line, and all observed relationships reached statistical significance after correcting for multiple predictors in a linear regression (p < 0.01). Panel (F) illustrates the differences in left atrial stasis between male and female patients. Panels (G,H) illustrate variations in left atrial blood flow stasis by age or diabetes status, neither of which was a significant predictor in the linear regression model. Values are shown as mean ± SE; ** p < 0.01.

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  Figure 4. Visualization of heart rate–associated left atrial stasis patterns in a patient with low heart rate and a patient with high heart rate with paroxysmal atrial fibrillation using 4D Flow MRI. Segmented 3D reconstructions of the left atrium, overlaid with a heat map representing voxel-level stasis intensity. The accompanying color scale (0–100) quantifies stasis magnitude, with warmer colors reflecting higher stasis.

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  Figure 5. Visualization of left atrial stasis in men and women with paroxysmal atrial fibrillation using 4D Flow MRI. Segmented 3D renderings of the left atrium are shown for male and female participants, with an overlaid heat map representing voxel-wise stasis values. Color intensity corresponds to the stasis scale displayed to the right (ranging from 0–100). Warmer colors indicate regions of higher stasis.