Left atrial glucose metabolism by 18F-FDG PET/CT in persistent atrial fibrillation and after return to sinus rhythm
Authors: Marchandise S , Raoult T , Roelants V , Garnir Q , Scavee C , Varnavas V , Wauters A , Gruson D , Nellessen E , Beauloye C , Gerber B 
Published: November 2023

Abstract

Background
Atrial Fibrillation (AF) is strongly associated with the development of Left Atrial (LA) remodeling. Animal studies pointed to an important role of metabolic deregulation in AF, yet few studies have assessed LA myocardial metabolism in vivo in patients with AF. 18-fluorodeoxyglucose (FDG) Positron Emission tomography (PET) has been widely used for evaluation of left ventricular (LV) metabolism, but its application to study metabolism of LA has not yet been explored.

Purpose
The aim of this study was to evaluate LA glucose metabolism and contractile efficiency in patients with persistent AF, following our successful implementation of a protocol enabling the acquisition of high-resolution PET images of the LA.

Methods
36 nondiabetic patients (64±7 years, 29 men) with persistent non valvular AF (peAF) undergoing a first AF ablation and 5 healthy age matched volunteers (69±5 years, 3 men, p=0.114) without AF underwent FDG PET, speckle tracking echocardiography (STE) and cardiac MRI (cMR). PET was performed after overnight fasting and after administration of a nicotinic acid derivative (Acipimox 250 mg) to maximally stimulate myocardial glucose uptake. The 3 tests were repeated 3 months later in 26 patients in whom return to permanent sinus rhythm (SR) could be obtained after the ablation procedure. PET images were registered with cMR LA angiography, and the mean partial volume and spillover corrected standardized FDG uptake (SUV) in the whole LA, the left atrial appendage (LAA), and the left ventricle (LV) were computed. Measurements were compared to global Peak Atrial Longitudinal Strain (GPALS) and to left atrial ejection fraction (LAEF) measured by STE and LA contractile efficiency was computed as the ratio of LA SUV to LAEF.

Results
Hemodynamics (syst. BP mmHg: 128±11 vs 129±5 mmHg, p=0.663) and metabolic parameters (glycemia: 99±14 vs 96±7 mg/dl, p=0.480) were similar in peAF patients and healthy controls. While 18F-FDG SUV in the LV was comparable between pEAF patients and healthy controls, patients in peAF exhibited significantly increased SUV in LA and LAA compared to controls. Following a return to SR, LA-SUVmean and LAA-SUVmean in patients peAF decreased significantly after 3 months (20.3%, p&lt;0.002 and 34.1%, p&lt;0.001), whereas the LV-SUVmean remained unchanged (p=0.847). The Global Peak Atrial Longitudinal Strain (GPALS) increased by 54.2%(p&lt;0.001), and the Left Atrial Ejection Fraction (LAEF) by 39.2% (p&lt;0.001), post-restoration of SR. (Figure 1). Accordingly contractile efficiency of LA SUV/LAEF in peAF patients improved significantly upon their return to SR (47%, p&lt;0.001).

Conclusion
LA glucose metabolism is significantly increased in peAF and return after restoration of SR. This could indicate oxygen wasting and reduced contractile efficiency of AF or metabolic shift towards preferred glucose metabolism in AF. These findings support the notion that LA glucose metabolism plays a role in the pathophysiology of AF.Figure 1Figure 2