ICE during atrial diastole before the jump of the transseptal needle into the oval fossa. In this patient the LA cavity has a crescent-like shape at this time point of the cardiac cycle. Ao – non-coronary sinus of the aorta; CT – terminal crest; FO – oval fossa; LA – left atrium; LAFW – left atrial free wall; RA – right atrium; TSN – transseptal needle.