PMC6342331_01
A: Twelve-lead electrocardiogram showed persistent atrial flutter (AFL) with positive P waves in leads II (with a tiny negative initial deflection), III, aVF, and V1; negative P waves in lead aVR; and almost isoelectric P waves in leads I, aVL, and V2-V6. B: Intracardiac electrograms of the AFL recorded from a 20-electrode catheter from the lateral wall of the right atrium (RA) to the distal coronary sinus (CS). The tachycardia cycle length was 270 ms. The activation sequence in the RA was consistent with a counterclockwise direction while the activation in the CS was almost simultaneous. C: Fluoroscopic image. D: Ablation at the cavotricuspid isthmus led to a sudden alteration of atrial activation sequence, although the tachycardia continued. E: Isolation of the right pulmonary veins and linear ablation of the left atrial roof led to termination of the tachycardia and restoration of sinus rhythm. CSd = distal of the coronary sinus; CSp = proximal of the coronary sinus; Halo d = distal of the RA part of the 20-electrode catheter; Halo p = proximal of the RA part of the 20-electrode catheter; LAO = left anterior oblique.
gr1.jpg
PMC6342331_01_gr1.jpg
fig1
Positive P waves presented in leads II (with a tiny negative initial deflection), III, aVF, and V1 on the surface electrocardiogram (Figure 1A). The tachycardia cycle length (TCL) was 270 ms (Figure 1B and C). RA without cessation of the tachycardia or change of TCL (Figure 1D). Repeated mapping of the LA demonstrated that the same roof-dependent AFL was still present. Finally, linear ablation of the LA roof and isolation of the RPV led to termination and noninducibility of tachycardia (Figure 1E).
Activation map indicating the cavotricuspid isthmus-dependent reentry in the right atrium (RA) and roof-dependent reentry in the left atrium (LA) (middle upper panel: anterior view; middle lower panel: posterior view; white arrows indicate the directions of propagation of the reentrant circuits). Entrainment pacing and further measurements support the existence of concomitant reentrant circuits with postpacing interval (PPI)-tachycardia cycle length (TCL) <= 30 ms at the LA roof (A), RA lateral wall along the tricuspid annulus (B), and interseptum (D), while a PPI-TCL at the LA lateral wall is much longer (C). MA = mitral annulus; TA = tricuspid annulus.
gr2.jpg
PMC6342331_01_gr2.jpg
fig2
Biatrial 3-dimensional electroanatomical mapping (CARTO 3, Biosense Webster, Irvine, CA) also suggested a cavotricuspid isthmus (CTI)-dependent AFL in the RA, while a craniocaudal activation pattern on the posterior wall of the left atrium (LA) was observed (Figure 2). TCL of 0-30 ms at the CTI; lateral, anterior, and septal walls of the RA; and the roof and septal wall of the LA, but > 30 ms at the LA lateral wall and CS. This confirmed that a roof-dependent AFL surrounding the right pulmonary veins (RPV) existed concomitantly with the CTI-dependent AFL and used the interatrial septum as a common pathway (Figure 2).
Measurements of the local activation time (LAT) at both sides of septum with location of assessment (left panel) and explanatory sketch (right panel). The left atrial (LA) septum was activated earlier than the right atrium (RA) septum inferiorly (LAT anterior: -17 vs 12 ms, posterior: -27 vs 27 ms) but later superiorly (anterior: 37 vs 24 ms, posterior: 75 vs 39 ms). Conduction time was longer along the LA septum than the RA septum (anterior: 54 vs 12 ms, posterior: 102 vs 12 ms; A, B). Repeated mapping of the LA after the RA reentry was eliminated (C, D) demonstrated that the same roof-dependent atrial flutter was still present, but the anterosuperior LA septum was activated much later than before (LAT 69 vs 37 ms, shown in circles), with the activation time of the posterior LA septum unchanged (103 vs 102 ms).
gr3.jpg
PMC6342331_01_gr3.jpg
fig3
At the anterosuperior septum, the activation time of both sides was consistent with the CTI-dependent AFL (Figure 3A and B). However, the anterosuperior LA septum was activated much later than previously (Figure 3C and D).