Paroxysmal Long R-P Tachycardia.

This case highlights characteristic features of atrial tachycardia arising from the mitral annulus. P wave morphologies can provide additional clues regarding the origin of atrial tachycardia on the mitral annulus. The atrial activation sequence is sometimes, but not always, earliest in the His potential electrogram position and may or may not be characterized by proximal-to-distal coronary sinus activation. Careful mapping along the mitral annulus to determine the earliest site of activation with reference to the surface P wave is a reliable method for precisely localizing an atrial tachycardia origin. Catheter ablation can be approached using either a transseptal or retrograde aortic approach.