Figure legend:
Fig 1. Electrodes shown from top to bottom are four surface ECGs (1, aVF, V4, V1), CS12 (Middle CS) to CS34 (proximal), His distal and proximal, roving mapping catheter (MAP) right atrium RA 5(proximal, near high RA) to RA 1(distal).
A: First beat is wider Mc beat and second beat is narrower HMc beat. The atrial activation sequence and SA measurements are similar in both beats suggestive of extra-nodal VAC.
B: Both beats are Mc but the first beat shows SAC which got released in the next beat having true VAC.
Fig 2. Electrodes shown from top to bottom are four surface ECGs (1, aVF, V4, V1), CS12 (Middle CS) to CS34 (proximal), His distal and proximal, roving mapping catheter (MAP) right atrium RA 5(proximal, near high RA) to RA 1(distal).
A: First beat is HMc with SAC. Second beat is PHc with SAC. Schmutz/SAC (marked as *) was noticeable along with the delayed separate ventricular EGM in the second beat (best seen in MAPp).
B: First beat is HMc with shorter SA. Second beat is PHc with longer SA. However, the VA i.e HA remains same in either of the beats. The absence of Schmutz is distinctly noticeable in the second beat as compared to the second beat of Fig 1B and Fig 2A. Underlying RBBB is also unmasked.
Fig 3: Electrodes shown from top to bottom are four surface ECGs (1, aVF, V4, V1), CS12 (Middle CS) to CS34 (proximal), His distal and proximal, roving mapping catheter (MAP) right atrium RA 5(proximal, near high RA) to RA 1(distal).
A: The catheter position and electrogram just before the maneuver shows a large A-EGM almost equal to V-EGM.
B: Post-RFA para-his pacing showing nodal VA conduction. The wider first beat with Mc had shorter SA than narrower second beat (HMc) with identical atrial activation sequence.