Fig. 1
a Twelve-lead surface electrocardiogram. Premature ventricular contractions (PVCs) demonstrate varying coupling intervals, and the morphology of PVCs includes a complete left bundle branch block, inferior frontal axis, and precordial lead transition zone >V3. The QRS in lead I is positive, and the R-wave in lead II is more than that in lead III. The coupling intervals of ectopic beats vary with multiple coupling intervals. b Activation mapping of ventricular parasystole (VP) shows no distinctively early focus. The anterior free wall of the right ventricular outflow tract (RVOT) is slightly precedent. c Bipolar and unipolar electrocardiograms during two adjacent VPs. d The fusion degree of VP and the nodal rhythm is different between the two VPs, and the morphologies of the QRS complexes are different. b Three-dimensional image and local bipolar and unipolar electrocardiograms of the target located at the middle free wall of the RVOT (green point); ventricular activation on the unipolar electrocardiogram demonstrates a QS morphology. e Three-dimensional image and local bipolar and unipolar electrocardiograms of the target located at the anterior free wall of the RVOT (red point); ventricular activation on the unipolar electrocardiogram also demonstrates a QS morphology