FIGURE LEGENDS
Figure 1A narrow QRS tachycardia dependent on a jump-up in the AH interval was induced by atrial extra stimulation. The numbers indicate the cycle lengths in ms. II, V2, V5 = surface electrogram; His d and His p = distal and proximal His bundle region; CS d to CSOS = distal to proximal coronary sinus ostium; HRA = high right atrium; RV = right ventricle; A and H = atrial and His bundle electrogram.Figure 2During the tachycardia, intermittent AV dissociation was observed, and the H-H intervals fluctuated. (A) late coupled sinus complex (B) early coupled sinus complex asterisk = atrial contraction from the sinus node. The other abbreviations are as in Figure 1.Figure 3The response to the ventricular overdrive pacing during the tachycardia. arrow = The pacing stimulus at CSOS did not capture the atrium. rH = retrograde His bundle potential. The other abbreviations are as in Figure 1.