Macro-reentrant Single-loop Biatrial Flutter Appearing as Typical Atrial Flutter: Case Study and Review

Figure 1:. Diagram of surgical incisions from the posterior view performed during mitral valve surgery. An interatrial groove vertical incision was made between the right-sided pulmonary veins and septum in the LA (shown in red) with extension of the incision to the outer wall of the RA (also shown in red). The septum on the inside of the RA was then incised and opened (blue dashed line) toward the mitral valve annulus. IVC: inferior vena cava; LA: left atrium; MVA: mitral valve annulus; RA: right atrium; SVC: superior vena cava.

Figure 2:. Twelve-lead ECG of the atrial flutter.

Figure 3:. A: Entrainment from the CS with a PPI of 348 ms and TCL of 340 ms. B: Entrainment from the distal anterolateral RA with a PPI of 356 ms and TCL of 340 ms. C: Entrainment from the distal CS with a PPI of 340 ms and TCL of 340 ms. In A, B, and C, intracardiac recordings include the anterolateral RA catheter (Deca) in purple, Abl, and CS catheter in yellow. Also, the distal electrodes of the anterolateral RA catheter are inferior, while the proximal electrodes are superior along the RA free wall. CS: coronary sinus; HBE: His-bundle catheter; PCS: proximal coronary sinus.

Figure 3:. D: Diagram of proposed initial flutter circuit involving the RA and LA. The black bar indicates scar tissue from prior surgery. CS: coronary sinus. E: Abl positioned at the CTI prior to RF ablation. In E, intracardiac recordings include the anterolateral RA catheter (Deca) in purple, Abl, and CS catheter in yellow. Also, the distal electrodes of the anterolateral RA catheter are inferior, while the proximal electrodes are superior along the RA free wall. BB: Bachmann’s bundle; CS: coronary sinus; HBE: His-bundle catheter; IVC: inferior vena cava; LA: left atrium; PCS: proximal coronary sinus; RA: right atrium.

Figure 4:. A: Color activation map of the right lateral RA after CTI ablation with prolongation of the CL. Activation was seen occurring down the lateral wall from BB and then moving posteriorly toward the CS. B: Activation map posterior view of the RA after RA isthmus ablation covering 360 ms out of the 380 ms of the TCL. A narrow channel is seen between the SVC and IVC facilitating conduction from the lateral wall to the CS. The map also shows that the light blue portion of the CL is missing, corresponding with activation of BB. The surgeon’s incision across the septum is also noted. C: Posterior view of the RA, with a voltage map of the RA showing scar and low-voltage areas in red forming a narrow channel, across which activation was found to occur. Catheters are seen in the CS (yellow) and posterior RA (red). Ablation lesions are seen across the channel, which terminated the tachycardia. BB: Bachmann’s bundle; CS: coronary sinus; RA: right atrium; TCL: tachycardia cycle length.

Figure 5:. Entrainment from the distal ablation catheter near the narrow channel seen on the posterior RA. The PPI was 370 ms and was equal to the TCL. Intracardiac recordings include the anterolateral RA catheter (Deca) in purple, ablation catheter in white, and CS catheter in yellow. The distal electrodes of the anterolateral RA catheter are inferior, while the proximal electrodes are superior along the RA free wall. Abl: ablation catheter; CS: coronary sinus; RA: right atrium; TCL: tachycardia cycle length.

Figure 6:. A: Ablation near the posterior RA channel terminated atrial flutter to sinus rhythm. Left atrial activation occurred over BB as the CS was isolated from the RA. B: Pacing from the low anterolateral RA to check the CTI ablation line. Conduction at this point was now occurring from distal to proximal within the CS, while time to the PCS had become markedly prolonged at 224 ms. In A and B, intracardiac recordings include the anterolateral RA catheter (Deca) in purple, Abl in white, and CS catheter in yellow. Also, the distal electrodes of the anterolateral RA catheter are inferior, while the proximal electrodes are superior along the RA free wall. BB: Bachman’s bundle; Abl: ablation catheter; PCS: proximal coronary sinus; RA: right atrium.