Patient 1
Patient 1 has been introduced detailly in a former publishment written by some of our authors [2]. He was a 25-year-old man who was otherwise healthy. His tachycardia could be induced by ventricular burst pacing, with a complete right bundle branch block (CRBBB) pattern, cycle length (CL) variating from 220 to 300 ms. But S1S2 and S1S2S3 stimulation of the atrium and the ventricle did not induce any abnormal phenomena. There were 3 types of VA relationships during tachycardia. One was V-A 1:1 relationship with long RP intervals, another was VA dissociation with V faster than A rate, the 3rd was VA dissociation with atrial fibrillation (Figure 1A). Thus atrial tachycardia and atrio-ventricular reentrant tachycardia (AVRT) could be excluded. HV intervals during sinus rhythm and tachycardia were equal (50ms) which excluded ventricular tachycardia. His bundle refractory period ventricular stimuli could reset the tachycardia with H-H interval reseted earlier than the V-V interval and terminate the tachycardia repeatedly which suggested the existence of an AP. His bundle refractory period ventricular stimuli during tachycardia complicated with AF suggested that the AP was not connected to the atrium, but to the AV node (Figure 1B). Multiple QRS fusion morphologies during His bundle refractory period ventricular stimuli on a fixed RVA site could be observed, suggesting the AP was a nodo-ventricular (NV) fiber which provides a broader period for His bundle refractory period ventricular stimuli to enter the circuit more easily (Figure 1B) [9 ]. S1S1 pacing of RVA led to dissociation of H and V, which excluded the ventricle from the reentrant circuit and further suggested that it were an AVNRT (Figure 1C). Both evidences confirmed that it was an AVNRT with a concealed NV fiber as a bystander. Sketch maps of the tachycardia are shown in our previous work (Figure 1D) [2].
After thermo-controlled ablation (55°C, 40 watt, 90 seconds) of the slow pathway of AV node at the lower 1/3 of the triangle of Koch, the tachycardia could not be induced anymore.