Figure Legends:
Figure 1. Surface electrocardiogram (I, aVF, V1, V6) and
intracardiac electrograms - His bundle electrogram distal and proximal
(HISD, HISP), coronary sinus (CS) 9,10 dipoles at CS ostium, & CS 1,2
dipoles at distal CS. Pacing is being done from HBD and is followed by
tachycardia; both show identical eccentric atrial activation patterns
(marked by arrows) with earliest activation at CS 3,4 channel.
Figure 2. Left panel. Fluoroscopic image showing location of
left ventricle pacing site and ablation catheter positioned at the
mitral annulus transeptally in RAO 30 (left upper panel) and LAO 40
(left lower panel). Right panel. 12-lead surface
electrocardiogram at the initiation of radiofrequency energy delivery
depicting sudden change in QRS morphology after the
6th beat.
Figure 3. Left panel. Surface electrocardiogram (I, aVF, V1,
V6) and intracardiac electrograms recorded from catheters as depicted in
figure 2 left panel. The arrow after the 2nd beat
denotes the artefact at the initiation of radiofrequency energy
delivery. The orthodromically captured His bundle potentials on the HISD
channel and the ventricular/atrial potentials on the RFD channel are
marked with H, V and A respectively. Note the sudden change in QRS
morphology and width with loss of ventriculo-atrial conduction after the
6th beat. Right panel. The shaded beat on the
left panel at a higher speed of 300 mm/sec to demonstrate a short HV
interval of 20 ms suggesting fusion between wavefronts originating from
the ongoing othrodromic re-entrant tachycardia and the LV pacing.