Discussion
In this case, a patient with heart failure due to rapid wide QRS
tachcardia due to accessory pathway conduction with Ebstein anomaly
underwent successful ablation of the accessory pathway during AF. There
are two main points in this treatment. First, the location of the
functional TA in the Ebstein anomaly was marked in advance using ICE, as
the ablation failed 25 years ago and it is difficult to locate the TA
anatomically on X-ray. Moreover, it has been recognized that catheter
ablation should optimally target anatomical and not functional TA. In
this case, the accessory pathway mapping was easily done by marking the
anatomical annulus using ICE and the ablation target mapping was easily
done using a 3D mpping system. Second, we succeeded in ablating the
accessory pathway under AF. We used pattern matching to extract only the
ventricle waves with maximum pre-excitation, and mapped only the
electrogram of atrioventricular conduction via the accessory pathway. A
RM, which can visually display all waveforms in chronological order, was
used to visually display the earliest accessory pathway to the
ventricle, and ablation was successfully performed.
Although other studies have reported that the RM is more useful than the
LAT map for atrial tachycardia, this is the first report in which the RM
was used to identify the accessory pathway during AF. Normally, annulus
mapping is difficult during AF because the mixture of irregular atrial
eletrograms. The conventional mapping method, the LAT map, assigns one
premature point to one point and reflects the colour on the map, so that
the propagation map and coherent map using LAT resulted in a disordered
map and accessory pathway could not be identified. (Fig. 3-A) In the LAT
map, the excitation timing at a specific time within a certain time
window (window of interest) is indicated by colour, but annotation is
required to determine the excitation timing. In 3D intra-cardiac
electrograms visualisation including the RM, the annotation of the
excitation timing is not necessary as all excitations are reflected on
the map even if there are multiple excitations in the window of
interest. Random excitation of AF became a small noise, and consistent
propergation emerges.
Using the same method described as in this case report, patients with
rapid wide QRS response via accessory pathway during AF who are
difficult to defibrillate because of suspected thrombus in the left
atrium can be ablated using accessory pathway mapping without
defibrillation.