ABSTRACT: Background:Atrial flow regulator (AFR) (Occlutech, Helsingborg, Sweden) are self-expanding, circular devices. A flexible waist in the centre connects the two discs and has a centrally located shunt. Case summary:We report a case of an 80-year-old woman undergoing a repeat left atrial ablation for persistent atrial fibrillation with an implanted AFR. The AFR was implanted 1 year prior to the procedure for heart failure with preserved ejection fraction as part of the AFR-PRELIEVE trial. A single, fluoroscopy-guided, transseptal puncture was performed infero-posterior to the device, allowing the positioning of the mapping (LASSO® 20?mm, Biosense Webster, Irvine, CA, USA) and ablation (Thermocool Smarttouch SF, CARTO®, Biosense Webster, Irvine, CA, USA) catheter in the left atrium. Three-dimensional mapping (CARTO®, Biosense Webster, Irvine, CA, USA) and left atrial ablation were successfully performed. After the procedure, fluoroscopy and transthoracic echocardiography showed an unchanged device position. Discussion:To our knowledge, this is the first case report of a transseptal puncture in a patient with an implanted AFR. Transseptal puncture in patients with an implanted AFR seems to be safe and feasible. With device diameters of 21-23 mm and based on previous studies on similar devices, transseptal puncture should be possible in most patients, as opposed to puncture through the device.