1. 21 yr old lady Recurrent tachycardia episodes Normal echo Inputs from Tahmeed and Chandrashekhar

2. During catheter insertion-D/D? Tachy initiated by PAC with prolongation of PR; P wave narrow, in ST segment; VA linking despite “wobble” in first few complexes makes AT unlikely. DD: Atypical AVNRT versus ORT

3. Another episode- any further information? RBBB during tachy this time. TCL longer than the previous tachy. However, difficult to draw conclusions since these are 2 separate episodes. 1400 ms 1300 ms

4. Intracardiacs-D/D now? Among available channels, A at His region is earlier. Same D/D as before

5. Another episode, 3 minutes later- any further insight? No. Spontaneous termination after V.

6. Analyse: VA time slightly longer with complete RBBB compared to incomplete RBBB.

7. Comment- Spontaneous termination, fortuitous simultaneous RV pacing spike

8. Route of retrograde conduction? No obvious decrement: AP likely

9. What next? PVC during tachycardia; either his-synchronous or entrainment from RV

10. Interpret: atrium entrained. Post-entrainment:-VAHV response. Corrected PPI-TCL in keeping with ORT

11. Consistent with the prior diagnosis? Yes. His-refractory VPD advances the next A and resets tachycardia.

12. Any further confirmation needed? No. Termination of tachycardia without A=ORT If not, what next? Map the tricuspid annulus.

13. Signal at RF site- where is this likely to be? Likely right sided (given prior findings); away from CS os and His area.

14. After ablation

15. RF site-LAO 40

16. Final diagnosis: Concealed right anterolateral AP with ORT Successful RF ablation