Left atrial electroanatomic activation map of the clinical atrial flutter. The mitral valve is cut out. The red stripe on the septum marks the “early-meets-late” zone of the activation map. The electrogram from the asterisked site is shown in the right-hand panel. LAO indicates left anterior oblique; and RAO, right anterior oblique.
Entrainment maneuvers. Entrainments from (A) site of fractionated signals at the endocardial lateral mitral isthmus (site of prior linear ablation) as seen on the ablation catheter-distal (ABL d) with post-pacing interval 281 ms, and (B) from proximal coronary sinus (CS 9,10) at 6:30 around mitral annulus with post-pacing interval 243 ms. Tachycardia cycle length is ≈242 ms.
Fluoroscopic left anterior oblique (LAO) projection. The duodecapolar catheter has electrodes spanning from the coronary sinus (CS) to the right atrium (RA). The asterisks show sites of similarly early activation noted on intracardiac electrograms in April 9th Question. As these are spatially disparate sites, none of them could be the site of origin. Rather, the site of origin must be triangulated to places that would be equidistant from all 3 sites. ABL indicates ablation catheter; HIS, hexapolar His-bundle recording catheter; and LAA, left atrial appendage circular mapping catheter.
Electroanatomical activation map of the left atrium viewed in a posteroanterior projection. A site on the left atrial posterior wall between the left and right pulmonary veins was the earliest mapped site for the premature atrial complex, with local activation time 55 ms earlier than any of the asterisked sites in Figure 1. The activation wavefront radially spreading out from this site of origin took a similar 55 ms to reach similarly distant regions of HIS (His-bundle catheter in right atrial anteroseptum), coronary sinus (CS), and left atrial appendage (LAA).