PMC5775445_01
Surface 12-lead electrocardiogram showing atrial flutter (AFL) with 3:1 atrioventricular conduction. Sawtooth-like negative flutter waves were noted in the inferior leads. The negative flutter waves in all precordial leads were not compatible with typical AFL.
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fig1
On a 12-lead surface electrocardiogram, he now presented with AFL with sawtooth-like flutter waves at a cycle length of 200 ms (Figure 1).
A: Surface electrocardiogram and intracardiac electrograms from the high right atrium (HRA) and coronary sinus (CS) during induced (AFL #1) and clinical (AFL #2) atrial flutter (AFL). The CS disparate activation pattern was observed both in AFL #1 and AFL #2, but the direction of the CS musculature (arrows) and left atrium (LA; dotted arrows) activations was the opposite between AFL #1 and AFL #2. B: Activation maps of the right atrium (RA) and LA during AFL #1 and AFL #2. Note the counterclockwise and clockwise activations around the CS area in AFL #1 and AFL #2, respectively. A conduction block line across the cavotricuspid isthmus is shown by the red tags. A partial conduction block with slow conduction was noted in the proximal CS. LSPV = left superior pulmonary vein; LIPV = left inferior pulmonary vein; MA = mitral annulus; PPI-TCL = difference between the postpacing interval and tachycardia cycle length.
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fig2
During AFL #1, double potentials with decreasing interpotential intervals from the proximal to distal CS were noted (Figure 2A, upper). Paul, MN), demonstrating macroreentry utilizing the CS and adjacent atrial myocardium in a counterclockwise direction (Figure 2B, upper). AFL #1 terminated during the entrainment pacing, we attempted to reinduce AFL #1, and at that time the clinical AFL was induced (AFL #2, Figure 2A, lower). A similar CS activation pattern was observed during AFL #2, but the relationship of each component was reversed. Biatrial activation and entrainment mapping during AFL #2 revealed peri-CS macroreentry in a clockwise direction (Figure 2B, lower).
A: Intracardiac electrograms at the successful ablation site (see Figure 2B) for AFL #2. Note the double potentials (P1 and P2) with intervening fragmented activities. Abl = ablation catheter; other abbreviations as in Figure 2. B: The AFL terminated 2.7 seconds after the initiation of the radiofrequency (RF) application with conduction block between P1 and P2. C: Alterations in the coronary sinus (CS) electrograms during sinus rhythm before and after the ablation of the slow pathway and AFL. Before the slow pathway ablation in the previous session, the left atrium and CS electrograms were fused and activated in the same direction (left panel). A disparate activation pattern was already noted before the AFL ablation. Note the fragmented delayed potentials in the proximal CS (asterisk), implying an incomplete conduction block in the proximal CS (middle panel). There was a complete conduction block in the proximal CS after the AFL ablation, although isolation of the CS musculature was not achieved (right panel).
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fig3
AFL #2, a critical slow conduction site was present in the proximal CS. An RF application at that site, where the double potentials with intervening fragmented potentials were recorded, terminated AFL #2 (Figure 3A and B). AFL #1 was considered to share the critical slow conduction site with AFL #2, because AFL #1 was no longer inducible after the successful ablation of AFL #2. Multiple RF applications delayed the conduction from the LA to the CS, but failed to block the LA-CS connection (Figure 3C).