Visualization of acute edema in the left atrial myocardium after radiofrequency ablation: Application of a novel high-resolution 3-dimensional magnetic resonance imaging sequence

Abstract

Background: Ablation-induced left atrial (LA) edema may result in procedural failure due to reversible pulmonary vein isolation. Conventional T2-weighted magnetic resonance edema imaging is limited by low spatial resolution.

Objective: The purpose of this pilot study was to optimize and validate a 3-dimensional (3D) sampling perfection with application-optimized contrasts using different flip-angle evolution (SPACE) sequence for quantification of T2 signal in the LA, and to apply it in recently ablated patients, comparing myocardial edema on T2-SPACE to tissue damage on late gadolinium enhancement (LGE) imaging.

Methods: Phantom studies were performed to identify 3D-SPACE parameters for optimal contrast between normal and edematous myocardium. Fourteen AF patients were imaged with both 3D-SPACE and dark-blood turbo-spin echo (DB-TSE) to compare image quality and signal intensity between the 2 techniques. Eight patients underwent pre- and postablation 3D-SPACE and 3D-LGE imaging. Ablation points were co-registered with corresponding myocardial sectors, and ablation-induced changes in T2 and LGE signal intensities were measured.

Results: Signal-to-noise ratio and contrast-to-noise ratio were higher on SPACE vs DB-TSE (65.5 ± 33.9 vs 35.7 ± 17.9; P = .01; and 59.4 ± 33.0 vs 32.9 ± 17.7; P = .04, respectively). T2-signal correlated well on 3D-SPACE and DB-TSE, such that each unit increase in TSE intensity correlated with a 0.69-unit increase in SPACE intensity (95% confidence interval 0.56-0.82; P <.001). T2 and LGE signal intensities were acutely increased at ablation sites. The extent of postablation edema was higher compared to LGE, although the spatial distribution of hyperenhancement around pulmonary veins seemed similar in both modalities.

Conclusion: T2-SPACE can be used to map the extent of acute postablation edema in the thin LA myocardium, with improved resolution and lower artifact compared to traditional DB-TSE.

Keywords: Atrial fibrillation; Late gadolinium enhancement; Left atrial edema; Left atrial fibrosis; Left atrial imaging; Radiofrequency ablation; T2-weighted imaging.