A Difficult Case Of Left Atrial Flutter.

A 55-year-old male was referred for a third ablation procedure because of recurrent atrial fibrillation. During re-isolation of the inferior right pulmonary vein the patient developed an atypical flutter with an clockwise activation pattern around the mitral annulus. Linear ablation at the left mitral isthmus transformed but did not terminate the tachycardia. The cavotricuspid isthmus proved to be a second critical isthmus and linear ablation at this site terminated the tachycardia.