Quantification of Atrial Fibrillation-Related Imaging Markers Using Spectral Photon-Counting Computed Tomography

High-resolution spectral photon counting computed tomography (PCCT) may allow characterization of structural alterations within the conduction system - for identifying patients with atrial fibrillation.

To perform a quantitative tissue analysis of the interatrial septum (IAS) along the anterior internodal bundle, the sinoatrial (SA) node and its vascular supply with PCCT in patients with atrial fibrillation (AF) compared to controls.

From 802 patients referred to PCCT coronary angiography, 130 (65 with AF and 65 controls in sinus rhythm)(age 70.3 ±12.2 years, 37.7% women) were included. SA-artery length/anatomy, IAS fibrosis (score1-4), IAS and SA-node density (HU) and iodine concentration; and left atrial wall thickening (LAWT) were quantified by PCCT.

Patients with AF had shorter SA-arteries (p<0.001) but similar anatomy (left vs right). IAS fibrosis (Score 2-4) (87.7% vs 21.5%; p<0.001) and a fully fibrous IAS (78.5% vs 12.3%; p<0.001) were more prevalent in AF vs. controls. IAS density was higher in AF (55.3 vs -44.2 HU; p<0.001), and iodine concentration (1.45 vs -0.1mg/mL; p<0.001). The correlation between IAS density and iodine concentration was high (r = 0.749; p<0.001). Patients with positive left atrial remodeling (LAWT>2mm) had higher IAS fibrosis scores, higher IAS density and iodine concentration (p<0.001). SA-node density and iodine concentration was higher in AF (p<0.001).

Patients with AF exhibit shorter SA-arteries and more IAS fibrosis- highlighting an interplay between vascular supply and fibrosis. Both features may serve as imaging biomarkers for identifying patients with occult asymptomatic AF undergoing coronary PCCT angiography for clinical indications - in whom reinforced screening for atrial fibrillation may be considered.