Abstract
Mapping of multiple atrial tachycardias after previous cryoballoon pulmonary vein isolations and multiple radiofrequency ablations can be challenging even for experienced specialists. HD Grid high-density mapping catheter is one of the catheters, which helps not only to precisely identify the mechanisms of macro-reentry tachycardia but also to avoid unnecessary radiofrequency applications. Accordingly, we present two cases of complex atrial arrhythmia with the use of HD Grid, which showed clear visualization of mechanisms and target ablations with the termination of tachycardia.