Figure 3. Surface ECG and biatrial activation map of counterclockwise mitral annular flutter. Continuous electrical activation without presence of isoelectric baseline between the flutter waves is suggestive of a macroreentrant tachycardia. Flutter waves are typically positive in all precordial leads with V2 of smaller amplitude that V1 and V3 since the mitral annulus is an anterior structure. In addition, flutter waves are inferiorly directed flat to negative in lead I. The right panel shows an electroanatonic biatrial map of the tachycardia that confirms the counterclockwise rotation of perimitral flutter with passive activation of the right atrium. RSPV right superior pulmonary vein, TV tricuspid valve, SVC superior vena cava, IVC inferior vena cava, MV mitral valve, LPV left superior pulmonary vein.