Radiofrequency catheter ablation of focal atrial fibrillation triggers within the pulmonary veins is a rapidly developing therapy that relies on both recent technologies and evolving techniques. We describe the entrapment of a circular mapping catheter within the mitral valve apparatus after transseptal catheterization and mapping of the left atrium and pulmonary veins. The occurrence of this previously unreported complication stresses the need for continual monitoring and reporting of adverse effects from new devices and procedures to better inform patients and physicians of the benefits and risks of electrophysiologic interventions.