Detection of pulmonary vein and left atrial scar after catheter ablation with three-dimensional navigator-gated delayed enhancement MR imaging: Initial experience

Purpose: To prospectively evaluate whether scar caused by radio-frequency ( RF) ablation of the left atrium ( LA) in patients with atrial fibrillation can be depicted with high-spatial-resolution delayed enhancement magnetic resonance ( MR) imaging. Materials and Methods: All 23 subjects ( 16 men, seven women; mean age, 54 years +/- 13 [ standard deviation]) provided written informed consent; the study was approved by the local institutional review board and was HIPAA compliant. A high-spatial-resolution free-breathing delayed enhancement MR imaging method was developed to detect scar ( ie, ablated tissue) in the LA and pulmonary veins ( PVs). The LA in 15 patients before ablation and in 18 patients at least 30 days after ablation was examined. A reader with 4 years of experience assessed presence of delayed enhancement on images and circumferential completeness. Signal-to-noise and contrast-to-noise ratios were measured and compared with an unpaired t test. The relationship between measurements of enhancement thickness at the interatrial septum and the number of days after ablation was investigated. Results: No subject demonstrated preablation delayed enhancement of the atrial or PV wall, whereas postablation delayed enhancement was identified in all ( 100%). In patients after ablation, a partial to completely circumferential delayed enhancement pattern could be identified for the left inferior PV that encompassed 88% +/- 11 of the circumference, but only 62% of patients demonstrated more than 90% circumferential delayed enhancement. The signal-to-noise ratio of blood was 12, and the signal-to-noise ratios of the pre- and postablation left atrial wall were 15 and 22, respectively ( P < .05). A relationship between delayed enhancement wall thickness and the inverse of the time interval from ablation was identified ( P < .05). Conclusion: High-spatial-resolution delayed enhancement MR imaging allows noninvasive identification of scar induced by RF ablation following isolation therapy of the PV. (c) RSNA, 2007.