Atrial Tachycardia

A 56 yo male with history of mitral valve prosthesis presents with palpitation. What does this ECG show?

The history of mitral valve prosthesis suggests that this palpitation may be atrial tachycardia or atrial fibrillation. We see positive, saw-tooth shaped flutter waves in 2-3 aVF. If we look carefully at V1, we see flutter waves with isoelectric baseline between them. The PP distance is slightly longer than 200 ms. So the atrial rate is roughly 300/min. the transition ratio to the ventricle is 4/1. Therefore the ventricular rate is around 75/min. You can see the 3D mapping of this patient and the propagation of the tachycardia. The tachycardia is originating from the left atrium and the tachycardia loop is going around the mitral valve and LA posterior wall.