Figure legends
Figure 1 Electrophysiological observations of SVT1
A : Manifestation of retrograde conduction via the superior slow pathway (indicated by dot arrow) from a right ventricular (RV) apical extrastimulus with an S1-S2 coupling interval of 360 ms after basic overdrive pacing simultaneously from the coronary sinus (CS) and RV with an S1-S1 cycle length of 750 ms. Please note the earliest site of atrial activation (A2) during retrograde conduction over the superior slow pathway and S2-A2 interval measured as 410 ms in the His bundle recordings.
B: RV overdrive pacing with an S-S cycle length of 380 ms during SVT1, demonstrating VA dissociation, evidenced by no perturbation of the atrial cycles keeping with a cycle length of 390 ms during ventricular pacing.
C: Differential entrainment pacing at an S-S cycle length of 350 ms from the proximal CS (C-1) and low lateral right atrium (LLRA) (C-2). Please note that the VA interval immediately after the last stimulus during either pacing is measured as 115 ms.
CS p and CS d = the proximal and distal coronary sinus; His p and His d = the proximal and distal recordings of His bundle.
Figure 2 Successful ablation of SVT1 and SVT2
Electroanatomical activation mapping of SVT1 (A ) and SVT2 (D ), fluoroscopic views in the left anterior oblique view showing the position of the catheters including the ablation catheter (indicated by unfilled arrows) at the successful ablation site of SVT1 (B ) and SVT2 (D ), and intracardiac electrograms at the successful ablation site of SVT1 (C ) and SVT2 (E ).
Ao = aorta; LA = left atrium. Other abbreviations as figure 1.
Figure 3 Electrophysiological observations of SVT2
A : Intracardiac electrograms during the SVT2, with the atrial, His bundle, and ventricular deflections labeled as A, H, and V, respectively, on the distal His bundle recording (His d).
B : RV overdrive pacing with an S-S cycle length of 390 ms during SVT2, demonstrating VA dissociation, evidenced by no perturbation of the atrial cycles keeping with a cycle length of 400 ms during ventricular pacing.
C : Successful ventricular entrainment with an S-S cycle length of 380 ms, capturing the atria via the slow pathway (indicated by dot arrows), followed by reinitiation of the tachycardia with an initial V-A-V response. Please note the post-pacing interval is measured as 610 ms.
D : Termination of the tachycardia with a bolus injection of ATP with an end of the ventricular activation.
Other abbreviations are as in Figure 1.