Atrial Fibrosis by cardiac MRI is a correlate for atrial stiffness in patients with atrial fibrillation

Figures

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  Figure 1. Left atrial strain and fibrosis measurement. A) Comprehensive left atrial strain measurements evaluated nine metrics of strain. These consisted of strain at three phases (reservoir, conduit and, active phase), and timings to peak strain. Additionally, the time derivative of the strain curve yielded three strain rates and times to peak strain rate in the three phases. Timings were normalized by RR. B) In two subjects, atrial LGE slices from a 3D volume are shown with segmentations (in green), using a subject specific threshold, determined by including signal associated with the valvular enhancement, but excluding blood pool signals.

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  Figure 2. Representative examples of strain and atrial LGE. A) Strain curves for four patients, with normal LA volume, pressure and strain (blue), elevated atrial LGE but normal volume (grey), elevated atrial LGE and high volume (orange), and a patient with high pressure and volume but not significant LGE (yellow). The higher LA volume patients have reduced strains. In the high LA LGE subject with normal volume, strain is also reduced. In the high pressure subject, the time to peak reservoir strain rate increased. B-C) show representative color-coded slices from the atrial LGE images for the normal patient (B), and the patient with elevated LA LGE (C).

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  Figure 3. Heat maps, showing significant (p<0.05) Spearman rho correlation coefficients and p-values for 25 parameters within the entire cohort. Non-significant correlations are replaced with R=0. A) Spearman rho correlations. The four squares (with black and white lines) group parameters by LA volumetry; LA stiffness, strain and strain rates; LA deformation timings and LV volumetric parameters. Note that all strain metrics were measured for N=67, except active strain metrics (N=44). Atrial LGE was measured in N=41, and atrial LGE could be correlated with active function metrics in N=36. B) P-value heat map.

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  Figure 4. Left atrial fibrosis (LGE (mls)) correlates. LGE was correlated with strains, volumes and strain rates. Correlations were stronger among subjects with normal minimum LA volume. Correlations with Stiffness index was strongest. All shown correlations were significant (p<0.01).

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  Figure 5. Correlates of mean atrial pressure in the whole cohort (the other correlate, BMI, is not shown).

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  Figure 6. When comparing groups with normal vs. elevated pressure (LAP≥12mmHg, n=33), reservoir and conduit strain times and maximum LAVi were found to be different.