Patient 3
This patient was a 50 year old man. He suffered from palpitation for 12
years. He was otherwise healthy. Either atrial or ventricular EPS could
induce the tachycardia with CL variation from 260 to 275 ms. This
tachycardia had three patterns including a narrow QRS pattern, a
complete left bundle branch block pattern (CLBBB) with superior axis and
a CRBBB pattern with superior axis (Figure 3A). All 3 patterns could
switch to each other incessantly. Cycle length of the narrow QRS pattern
equaled to that of the CLBBB pattern (265 ms), while CL of the CRBBB
pattern was longer (275ms). V-A dissociation was observed during all 3
patterns of tachycardia which excluded atrial tachycardia and AVRT. H-V
intervals of all 3 patterns of tachycardia and sinus rhythm were equal
(46 ms, Figure 3B). Activation sequence of His on both sides during
tachycardia was from the proximal to the distal which suggested that the
tachycardia was a supra-ventricular one. His bundle refractory period
ventricular stimuli could reset H-H interval, indicating the existence
of an AP that did not connect to the atrium (Figure 3C). RVA pacing
during sinus rhythm produced V to H sequential conduction without V to A
conduction, and the proximal H was earlier than the distal H (Figure
3C). This phenomenon further suggested that there was an AP which was
not connected to the atrium. Since CL of the tachycardia was longer
during CRBBB than during CLBBB (Figure 3A), it could be deduced that the
AP located on the right side [4]. RVA entrainment
at 240 ms generated a more fully captured QRS morphologies than that at
250 ms (Figure 3D). This phenomenon suggested that the AP was an NV
fiber, but not an nodo-fascicular (NF) fiber. This tachycardia was an
orthodromic reentrant tachycardia mediated by a concealed NV fiber which
located on the right side. Sketch maps of the tachycardia are shown in
Figure 3E.
After thermo-controlled ablation (55°C, 40 watt, 100 seconds) of the
slow pathway of AV node at the lower 1/3 of the triangle of Koch, the
tachycardia could not be induced, and repeated EPS did not cause
“jump-up” phenomenon of A-H interval any more.
All three patients survived up till now without any symptoms of
recurrences.