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Left atrial fibrosis predicts impaired atrial function: proof of concept
Left atrial (LA) remodeling, associated with changes in atrial geometry, function and texture, is the hallmark of the pathophysiology of atrial fibrillation (AF). Magnetic Resonance (MR) imaging plays a key role in the assessment of LA remodeling. Recently, fibrotic burden, longitudinal strain and sphericity are introduced as novel measures that can be used to characterize atrial remodeling. However, the relation between these parameters is yet unknown.
This proof of concept study evaluated the association between LA longitudinal strain measured by MR Tissue Tracking, LA sphericity, and LA fibrotic burden in paroxysmal AF patients referred for catheter ablation.
Eight paroxysmal AF patients underwent MR imaging (1.5T Avanto, Siemens) in sinus rhythm prior to their pulmonary vein isolation (PVI) procedure. Sphericity and fibrotic burden were assessed from 3D wholeheart and late gadolinium enhancement (LGE) images acquired at the end of atrial diastole, using custom-written software. LA longitudinal strain was derived from cine-MR images using Tissue Tracking (Circle CVI42, Calgary, Canada). Corresponding to the 3 LA phases, strain measurements were subdivided into total strain (representing atrial reservoir function), passive strain (representing LA conduit function) and active strain (representing LA contractile booster pump function). The LA longitudinal strain was compared to sphericity and fibrotic burden in AF patients.
Mean LA sphericity was 70.69 ± 2.16% and mean LA scar burden was 13.29 ± 15.44%. Total LA strain and passive LA strain had a strong correlation with scar burden (R2=0.63; p=0.019, R2=0.88; p=0.001, respectively) (figure 1A and 1B). Active strain, representing atrial booster function, was not correlated with LA fibrotic burden (R2=0.1; p=0.455) (figure 1C). LA scar area had no correlation with LA sphericity (R2=0.13; p=0.382) (figure 1D). No relation was observed between LA sphericity and longitudinal strain.
LA reservoir function and LA conduit function are both significantly impaired in the presence of LA scar, while active atrial booster function was not affected. Therefore, impaired passive atrial deformation may serve as an early indicator of atrial fibrosis, even in the presence of limited remodeled atria, as indicated by a preserved, non-spherical shape. Future studies with a larger patient cohort are warranted to explore this concept in more detail.
ESC 365 is supported by Bayer, Boehringer Ingelheim and Lilly Alliance, Bristol-Myers Squibb and Pfizer Alliance, Novartis Pharma AG and Vifor Pharma in the form of educational grants. The sponsors were not involved in the development of this platform and had no influence on its content.
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