Right atrial remodeling following pulmonary vein isolation in patients with atrial fibrillation assessed by late gadolinium enhancement cardiac MRI

Background

Structural remodeling through atrial fibrosis in atrial fibrillation (AF) is a hallmark of atrial cardiomyopathy in both atria. It is unknown how reverse right atrial (RA) volumetric and functional remodeling after pulmonary vein isolation (PVI) corresponds to tissue-level changes. Late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) enables noninvasive assessment of atrial fibrosis.

Purpose

This study aims to evaluate RA LGE before and 3 months after radiofrequency (RF) PVI using 3D LGE-CMR.

Methods

AF patients (n=54, 62±7 years, 38 males, and 40 paroxysmal AF) underwent RF PVI, and LGE-CMR imaging at baseline and 3 months post-PVI in sinus rhythm. 3D LGE images were post-processed, with RA LGE quantified by the image-intensity-ratio (IIR) method, with IIR>1.20 considered overall fibrosis, IIR>1.20<1.32 defining border zone fibrosis, and IIR>1.32 dense fibrosis. RA volumes and strain were analyzed (n=50), and 18 healthy volunteers served as controls (45±14 years, 4 males).

Results

Among AF patients, RA LGE was similar at baseline and 3 months post-PVI for overall, border zone, and dense fibrosis (36.0[14.4–59.9]% to 41.0[22.4–56.5]%, p=0.54; 12.8[8.3–15.9]% to 13.9[8.1–16.2]%, p=0.22; 20.0[6.0–45.9]% to 23.5[9.7–39.7]%, p=0.69, respectively). RAVImin and RAVImax decreased following PVI (28.2±10.0 mL/m2 to 24.8±8.3 mL/m2; 44.7±11.3 mL/m2 to 40.4±11.2 mL/m2, both p<0.001, respectively), and RA reservoir strain increased compared to baseline (17.1±4.6% to 18.9±3.7%, p=0.03).

There was substantial interindividual variability in RA LGE changes despite all patients being in sinus rhythm during both MRI scans (Fig. 1). In 27 patients, RA LGE decreased 3 months post-PVI (RA LGE–, n = 27) accompanied by remodeled RA volumes and function, which was not observed in those with increased RA LGE (RA LGE+, n=27) (Fig 2).

Healthy volunteers exhibited significantly lower RA LGE levels (overall fibrosis: 8.3[4.2 – 12.5]%), smaller indexed volumes (RAVImax:37.3±8.2 mL/m2), and higher RA emptying fraction (47.3±6.7% vs. 37.7±11.4%), compared with AF patients.

Conclusion

Compared with healthy volunteers, patients with AF exhibited more extensive RA LGE, larger RA volumes, and impaired function, underscoring that AF related atrial remodeling is not confined to the left atrium. In AF patients, RA LGE did not change 3 months post-PVI, but RA volumes decreased and RA function improved. However, in half of patients there was a decrease in RA LGE, that coincided with reverse remodeling of RA volumes and function, which was absent in those with increased RA LGE.Fig1.Individual RA LGE changes post-PVIFig2.RA remodeling post-PVI: LGE-/+