Increased Atrial FDG Activity Identifies Reduced Atrial Function Beyond Rhythm and Cardiac Sarcoid Status

Abstract 2302988, presented at Western Atrial Fibrillation Symposium 2026

Atrial myopathy reflects a spectrum of structural, functional, electrical, and metabolic alterations within the atrial myocardium. Although structural remodeling such as left atrial dilation and impaired strain is well characterized, metabolic aspects of atrial disease remain underexplored. Our objective is to evaluate the relationship between atrial FDG avidity as a marker of metabolic activity and LA remodeling in patients undergoing cardiac imaging for suspected cardiac sarcoidosis (CS).We recruited 120 patients who underwent both cardiac MRI and FDG-PET/CT at the University of Washington Medical Center. Atrial metabolic activity was quantified by SUVmax and atrial target-to-background ratio (aTBR) on PET/CT. LA volume index (LAVi) and emptying fraction (LAEF), average long-axis strain, and phasic strain indices were derived from cine MRI using feature tracking (Panels A and B).LA average long axis strain was 37.1 ± 34.0%, LAEF 47.6 ± 16.1%, and LAVi 36.0 ± 23.0 mL/m2. Atrial FDG uptake was 2.4 ± 0.7 SUV. LA strain negatively correlated with both SUVmax (R= -0.44; P< 0.001) and aTBR (R= -0.53; P< 0.001), while LAVi positively correlated with both (R= 0.40 and R= 0.52, respectively; P < 0.001) (Panels C and D) after adjusting for AF, CS, and heart rate. AF patient exhibited decreased LAEF (42.6 ± 18.3% vs 49.9 ± 14.6% ; P=0.037), decreased reservoir (11.2 ± 4.9% vs 13.5 ±4.9%; P=0.04) and contractile strains (4.8 ± 3.3% vs 8.9 ± 4.1%; P=0.015), increased LA volume index (46.2 ± 25.5mL/m2 vs 31.4 ± 20.4 mL/m2; P=0.003) and increased atrial FDG avidity (2.6 ± 0.6 SUV vs 2.3 ± 0.7 SUV; P=0.012).Higher atrial FDG uptake independently correlates with reduced strain and increased LA volume, suggesting a novel marker of metabolic atrial activity that may emerge before clinical AF.