Successful ablation for non-pulmonary multi-foci atrial fibrillation/tachycardia in a patient with coronary sinus ostial atresia by transseptal puncture and epicardial approach

Key Teaching Points•To treat atrial tachycardia triggering foci that were located in the coronary sinus (CS) with ostial atresia, we performed puncture with a novel method; transseptal puncture from the right atrium septum to the inside of the coronary sinus.•To perform transseptal puncture of the CS, a crease that is more than 90 degrees and 5 cm from the tip of the Brockenbrough needle must be created. To retain the crease, we used a steerable long sheath (long-curve Agilis) for transseptal puncture.•This procedure has a high risk of complications such as cardiac tamponade and His bundle/slow pathway injury; therefore, careful judgment is necessary before performing this procedure.•To treat atrial fibrillation for which the site of earliest activation was found in the left atrium around the ligament of Marshall, we performed endocardial and epicardial ablation with percutaneous pericardial puncture. •To treat atrial tachycardia triggering foci that were located in the coronary sinus (CS) with ostial atresia, we performed puncture with a novel method; transseptal puncture from the right atrium septum to the inside of the coronary sinus.•To perform transseptal puncture of the CS, a crease that is more than 90 degrees and 5 cm from the tip of the Brockenbrough needle must be created. To retain the crease, we used a steerable long sheath (long-curve Agilis) for transseptal puncture.•This procedure has a high risk of complications such as cardiac tamponade and His bundle/slow pathway injury; therefore, careful judgment is necessary before performing this procedure.•To treat atrial fibrillation for which the site of earliest activation was found in the left atrium around the ligament of Marshall, we performed endocardial and epicardial ablation with percutaneous pericardial puncture.