Magnetic resonance post-contrast T1 mapping in the human atrium: Validation and impact on clinical outcome after catheter ablation for atrial fibrillation

BACKGROUND The impact of diffuse atrial fibrosis detected by T-1 mapping on the clinical outcome after atrial fibrillation (AF) ablation is unknown. OBJECTIVE This study aimed to validate and assess the impact of post-contrast cardiac magnetic resonance (CMR) imaging atrial T-1 mapping on the clinical outcome after catheter ablation for AF. METHODS CMR imaging was performed in 3 groups by using a clinical 1.5-T scanner: controls, patients with paroxysmal AF, and patients with persistent AF. A T-1 mapping sequence was used to calculate the post-contrast T-1 relaxation time (T-1 time) at the interatrial septum as an index of diffuse atrial fibrosis. A subset underwent left atrial endocardial bipolar voltage mapping for electrophysiologic correlation. After AF ablation, patients underwent clinical review and 7-day Hotter monitoring at 6-month intervals. RESULTS One hundred thirty-two patients (20 controls, 71 (63%) patients with paroxysmal AF, and 41 (37%) patients with persistent AF) underwent CMR imaging. Post-contrast atrial T-1 time was significantly shorter in AF groups (237 +/- 42 ms) than in controls (280 +/- 37 ms) (P < .001). Post-contrast atrial 1-1 time correlated with mean septal voltage (R-2 = .48; P < .001) and global Left atrial voltage (R-2 = .41; P < .001). A diagnosis of AF, AF duration, and Left ventricular end-diastolic volume independently predicted shortened post-contrast atrial T-1 time. The single procedure success rate was 74% at 12 +/- 5 months postablation. Post-contrast atrial T-1 time was the only predictor of arrhythmia recurrence in multivariate analysis (P = .015). A post-contrast atrial T-1 time of > 230 ms was associated with freedom from AF in 85% relative to 62% with a post-contrast atrial T-1 time of < 230 ms (P = .01). CONCLUSION Post-contrast atrial T-1 time as measured using CMR imaging provides an index of atrial fibrosis that correlates with tissue voltage, presence of AF, and clinical outcomes after catheter ablation.