Cardio-magnetic resonance with 4D Flow sequence before and after pulmonary vein ablation

Introduction: Pulmonary vein ablation is an effective treatment for atrial fibrillation, although it may be associated with complications such as pulmonary vein stenosis, which is usually diagnosed with computed tomography (CT) or cardio-magnetic resonance imaging (CMR). The 4D Flow sequence in CMR could provide additional information on morphology and flow, before and after ablation, complementing the usual assessment. Objective: To assess the usefulness of CMR with 4D Flow sequence for the assessment of pulmonary veins (PV) in the context of radiofrequency ablation. Although ablation is a technique with a low percentage of complications, these must be diagnosed early through imaging tests, with CT and magnetic resonance (MRI) being the most used. The 4D Flow sequence that evaluates intravascular flow has not been studied in this context. Method: 16 patients underwent CMR and PV ablation. In 14 of them, we did CRM after ablation. The following were calculated for each PV: diameter (in morphological sequences and in 4D Flow sequence), flow and flow velocity, by two independent observers. Before and after ablation values were compared. Results: Excellent correlation between the diameter measurements obtained in morphological sequences with the 4D Flow sequence for each PV, intraclass correlation coefficient (95% CI): right superior 0.92 (0.78-0.97), right inferior 0.91 (0.75-0.97), left superior 0.84 (0.56-0.94), and left inferior 0.92 (0.79-0.97). There is an adequate inter- and intraobserver correlation in diameter and flow measurements. A reduction in PV diameter greater than 10% was observed in 21 of 56 veins (37.5%), all of them with mild stenosis. There were no statistically significant variations (p < 0.001) in flow and velocity parameters obtained before and after ablation. Conclusion: The 4D Flow sequence provides morphological and flow information useful in monitoring after PV ablation.