Patient 2
This patient was a 40 years old woman. She suffered from palpitation for 2 years. She was otherwise healthy. Atrial S1S2S3 decremental stimulation discovered “jump-up” phenomenon of AH interval by 100ms (at S1S2S3=400/280/250-240ms) which demonstrated the existence of dual atrioventricular (AV) nodal pathways. Burst stimulation of the RVA induced a narrow QRS tachycardia repeatedly with CL variations from 325 to 368 ms. The tachycardia showed VA dissociation which excluded atrial tachycardia and AVRT. H and V were in 1:1 relationship and H-V interval during tachycardia equaled to that during sinus rhythm (48 ms), suggesting it were a supra-ventricular tachycardia (Figure 2A). His bundle refractory period ventricular stimuli could not only reset H-H interval and then V-V interval, but also terminate the tachycardia. All of the above phenomena suggested that the patient had an AP which did not connect the atrium. ATP (20 mg bolus) injection terminated the tachycardia, further suggested that the AV node were probably within the reentrant circuit (Figure 2C). RVA entrainment at 300 ms generated a more fully captured QRS morphology than at 310 ms (Figure 2B). This phenomenon suggested that the AP were an NV fiber, but not an NF fiber. Thus this tachycardia was an orthodromic nodo-ventricular reentrant tachycardia (NVRT). Sketch maps of the tachycardia are shown in Figure 2E.
After thermo-controlled ablation (55°C, 35 watt, 120 seconds) of the slow pathway of AV node at the lower 1/3 of the triangle of Koch (Figure 2D), the tachycardia was not induced, and repeated EPS did not cause “jump-up” phenomenon of A-H interval anymore.