10 yr old boy Recurrent narrow QRS tachycardia

10 yr old boy Recurrent narrow QRS tachycardia Normal Echo Inputs from Deep Chandh Raja, Ulhas Pandurangi and Chandrashekhar Some realigment of tracings to avoid confusion

nd 2 Regular narrow QRS, short RP tachycardia. D/D: 1. Orthodromic AVRT 2. AT 3. Typical AVNRT. Tachycardia initiated by PAC which is –ve in II/III; terminates with a P wave, making AT unlikely. During sinus rhythm, there is little prominence of R wave in V 1 but there is no definite evidence of pre-excitation

Baseline- Normal HV Route of retrograde conduction? Looks eccentric with A in CS 78 A earlier than in His; non-decremental

Comment-D/D now? Tachycardia initiation with an A-V-A sequence, without significant AH prolongation

Diagnosis confirmed? His-sync PVC advances the next ‘A’ and terminates the tachycardia ruling out AVNRT. Atrial activation sequence remains the same during tachycardia & PVC. Retrograde route: AP; Likely Dx: Orthodromic AVRT using Rt AP Wide QRS, V 1 –ve, short HV after termination; preexcitation or fusion with escape PVC. 310 ms H H 280 ms H

Interpret Para. Hisian Pacing: AP response - Ignore- possible sinus complex; note the A in His is early

Any further insight? VA intervals during apical pacing clearly more than during inflow pacing suggesting presence of AP as retrograde route RV apical pacing 325 ms RV inflow pacing 300 ms

RF signal-good? Yes; Early bipolar A with corresponding unipolar ‘A’ QS complexes; continuous VA bipolar signals. V and A of equal amplitude RF energy- likely site? Rt Tricuspid annulus free wall. Immediate split followed by brief reconnection followed by elimination of AP conduction seen

Different from before? Yes; VA shorter with RV apical pacing, suggests AV nodal conduction RV apical pacing 330 ms RV inflow pacing 340 ms

As expected? Yes; His capture results in shorter VA than Para. His capture s/o retrograde VA nodal conduction

RF site- Right posterolateral Adenosine- VA Wenckebach, then complete VA block LAO 40 RAO 30 PAC