Use of the Local Activation Time Histogram “Trough” to Identify the Slow Conduction Channel in Complex Congenital Heart Disease Macro-re-entrant Arrhythmias

Figures

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  Figure 1. Activation maps of the atria in flutter and the potential circuits. (A) An activation map of the right atrium (RA) in the anteroposterior projection. The window of interest was set at 100% of the tachycardia cycle length (240 ms). The local activation time histogram is missing the initial 30% of the tachycardia cycle length. (B) An activation map of the left atrium in the posteroanterior projection. The histogram shows that the entire cycle length was mapped with a broad area of early-meets-late (EML) (deep red) on the posterior wall. (C) A corresponding voltage map of the left atrium in the posteroanterior projection showing the pulmonary vein anatomy and patchy posterior scar (bipolar voltage cutoffs 0.05-0.5 mV). (D) A voltage map in the right anterior oblique projection demonstrating scar on the interatrial septum. An anatomic shell of the RA (grey) is shown for orientation. (E) A coherent map of the left atrium showing a potential roof-dependent flutter encircling the RPV ostium (cutout). The region of interest has been enlarged on the right. (F) A coherent map of the left atrium showing an alternative flutter mechanism around scar on the inferoposterior aspect of the…

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  Figure 2. Using the spread of local activation time points to identify the critical isthmus. (A) A table showing the distribution of local activation points across the tachycardia cycle length (TCL) by dividing into 10 equally spaced isochrones. The minimum represented isochrone is highlighted in blue. (B) An activation map of the left atrium shown in the right lateral projection. The isochrone with the lowest percentage of activation points (mid-blue) forms a narrow channel of activation over the septum. (C) Entrainment from the narrow channel using OctaRay bipoles C3-4 demonstrates concealed entrainment and a postpacing interval approximating the TCL. (D) The linear ablation lesion set shown in a right lateral projection. LPV, left pulmonary veins; RPV, right pulmonary veins.