Discussion
Several previous reports have suggested that these potentials indicate
the preferential pathway conduction connecting the origin of an
arrhythmia and the myocardial breakout site, and a preferential pathway
potential guided ablation can be an effective strategy for PVC
ablation.1,
3, 7 We
reported that presystolic potentials during PVCs and late potentials
during SR were seen at the successful ablation site, and the
configuration of the vertically and horizontally-flipped presystolic
potentials during PVCs nearly matched that of the late potentials during
SR.8 In this case
series, we also found that the M-shaped presystolic potentials during
PVCs and the W-shaped late potentials during SR were reversely matched.
These reversed potentials might indicate bidirectional conduction of the
preferential pathway in opposite
directions.8 To
demonstrate the hypothesis, we created an activation vector mapping with
the annotation of the onset of the presystolic potentials and offset of
the late potentials. At several points around the successful ablation
site, both the presystolic potentials during PVCs and late potentials
during SR were observed. At the PVC origin, the presystolic potentials
during PVCs were earliest and the offset of the ventricular electrogram
during SR was latest. Coherent maps visualizing the vector of this
preferential conduction indicated that the propagation direction of the
presystolic potentials was opposite to that of the late potentials,
which was supportive of our hypothesis.
These potentials are commonly seen in the periaortic area, but rare in
the RVOT³. In our case series, however, those potentials were also seen
in the peri-pulmonary-artery (PA) area. Based on our findings, those
M-shaped and W-shaped potentials may reflect the slow conduction due to
the smaller amount of myocardium adjacent to the valve annulus such as
the aortic valve and pulmonary valve.
The flipped M-shaped presystolic potentials matched the W-shaped late
potentials in the majority of our cases, but not in some cases. Those
observations might be explained by the difference in the direction
between the propagation of the preferential pathway to the ventricular
myocardium during the PVC and the propagation of the ventricular
myocardium to the preferential pathway during SR. Regarding the
association of the catheter position with the direction of the
preferential pathway conduction, if the catheter position is not
parallel to the direction of the preferential pathway conduction, those
potentials might not be reversely matched. To assess the configuration
of those potentials, we should consider the catheter position.