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.