Massive Left Atrial Thrombosis Shortly After Radiofrequency Catheter Ablation: Implications of Reduced Flow Dynamics Detected by Four-Dimensional Flow Magnetic Resonance Imaging

A large left atrial (LA) thrombus developed 5 days after repeated ablation for persistent atrial fibrillation despite uninterrupted anticoagulation. The thrombus formed at the previously ablated LA roof, where four-dimensional flow magnetic resonance imaging later showed reduced regional flow velocity, suggesting that persistent local flow stagnation may have contributed to thrombus formation.