1. 30 yr old man Normal echo 3 episodes of paroxysmal tachy All LBBB Inputs from Chandrashekhar, Chennai

2. Analyse. Low atrial (CS) pacing. As CL decreases, there is gradual QRS widening resembling LBBB with LAD. 400 ms

3. First is a sinus beat which shows His potential in the His D is earlier than the RB Potential in the RBP, which in turn is earlier than the RB potential in the RBD. Then pacing from HRAD starts (contrast with CS pacing in slide1), showing preexcitation. The wavefront goes down the right free wall pathway-- right atriofascicular pathway since it inserts distally into distal RBB So the RB potential from RBD now occurs earlier than the RB potential from RBP, which in turn occurs earlier than the His potential from His D indicating that the wavefront is going from below upwards 620 ms

4. A pacing showing preexcitation; with atrial premature beat (S2)there is very slight increase in the preexcitation

5. Any additional information? With V pacing and ventricular premature there is V3 phenomenon ( Bundle branch reentry)

6. Now? No additional insight

7. Diagnosis confirmed? Yes. Delayed RA APD after the septal A is committed preexcites the V indicating the presence of an AP and also resets the tachycardia, indicating the participation of the AP in the tachycardia circuit

8. Again…The same

9. And now? The tachycardia is terminated with an APD without conducting to the ventricle, indicating that the atrium is a component of the circuit

10. Adenosine-comment Tachycardia is terminated in the AV node

11. Adenosine- comment No preexcitation seen

12. Any use of this manouever? Not really from the post-entrainment response point of view. However, one may induce retrograde right bundle branch block sometimes which results in prolongation of the tachycardia cycle length

13. LB with superior axis - Mahaim antidromic tachycardia

14. Soon after- analyse. Preexcited A Fib intermittently (also seen in next slide) A rare ECG with Mahaim-like pathways

15. During catheter positioning-interpret. Catheter bump.

16. No Mahaim potential along tricuspid annulus Mapping performed during atrial pacing and during tachycardia What next? To map more distally along the the atriofascicular pathway closer to the distal insertion site

17. RF site- LAO 40

18. RF site- RAO 30

19. Signal at RF site

20. RF energy

21. As energy was continued, there was some automaticity of the heated RV site After this, no preexcitation was seen with atrial pacing and no tachy was inducible