Fig. 1

Right atrial MAT ablation. In A the flutter wave of counterclockwise CTI-dependent AFL was negative in inferior limb leads (II, III and aVF), positive in precordial lead V1, and progressively became shallow negative from precordial lead V2 to V6. In B the flutter wave of clockwise CTI-dependent AFL was positive in inferior limb leads, negative in precordial lead V1, and progressively became positive in precordial lead V2 to V6. In C counterclockwise AFL was terminated by CTI linear ablation after tricuspid valve bio-prosthesis implantation. Of note, two pouches were found in proximity to the tricuspid annulus (TA) and at the mid-portion of the CTI area (white arrows). Extensive and prolonged RF energy delivery was needed to interrupt AFL and achieve CTI block. The dotted circle represented the tricuspid annulus (TA). In D right atriotomy-related macro-reentry was identified to around the scar line (gray dots line), entrainment pacing at either side of the scar line produced a matched PPI. The critical isthmus was found between the inferior border of the scar and the inferior vena cava, where short linear RF ablation terminated the tachycardia and rendered it non-inducible. Of note, the mid-diastolic, low-voltage and fractionated bipolar potentials were recorded at the critical isthmus (red arrows). In E the ATa-free survival probability was compared in MV group (solid line) and TV group (dotted line), P = 0.70 by Log-Rank test. RAO right anterior oblique view, LAO left anterior obliqueview, PA posterior-anterior view, ATa atrial tachyarrhythmia, PPI post-pacing interval, LA the left atrium, CS coronary sinus