Cryoablation as an alternative strategy for bidirectional cavotricuspid isthmus block following multiple failed sessions of radiofrequency ablation due to epicardial-endocardial breakthrough: A case report

Figures

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  Fig. 1. Cavotricuspid isthmus (CTI) dependent atrial flutter (AFL) (counterclockwise AFL) in the fourth session. (A) Entrainment pacing (220 ms) from the tricuspid annulus (TA) catheter (left half) and the ablation catheter positioned at the cavotricuspid isthmus (CTI) (right half) (later identified as epicardial-endocardial breakthrough (EEB) sites in the CTI). This shows that both pacing sites' EEBs are participating in this tachycardia (the post-pacing interval minus the tachycardia cycle length: 2 ms and 18 ms, both within 30 ms). ms. (B) Fluoroscopic images during Entrainment pacing with the TA catheter and the ablation catheter. (C) Local activation map during atrial flutter before radiofrequency ablation in this session (left anterior oblique (LAO) inferior view). The white line indicates endocardial conduction block of the CTI (i.e., EEB). (D) Voltage map during atrial flutter before radiofrequency ablation in this session (LAO inferior view). The red area indicates ablation from the previous two sessions. (E) CTI linear ablation on the septal side of the low-voltage area (the exit sites of EEB; LAO inferior view). Additional ablation was intensively performed on the inferior…

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  Fig. 2. Second activation map of CTI dependent AFL (counterclockwise AFL) following radiofrequency ablation in this session. (A) The yellow area indicates the entrance of the EEB, where the unipolar electrogram showed a prominent R wave followed by a small and blunted S wave (LAO inferior view). Entrance site of the EEB was 9 mm away from the white line (indicating conduction block). Double potentials were recorded at the EEB site. (B) The green area indicates the exit of the EEB, where the unipolar electrogram shows a small and blunted R wave followed by a prominent S wave. Exit site of the EEB was 9 mm away from the white line. (C) Additional radiofrequency ablation both on the septal (exit of EEB) and lateral (entrance of the EEB) sides. (D) A reverse “U-curve” approach was used to ensure steadier contact during RF ablation near the inferior vena cava ostium. (E) Cryoablation sites on a right atrial voltage map during atrial flutter. (F) A local activation time map indicates that the excitation from the exit site of the EEB radiates outward, with a portion of it proceeding in the initial direction and another segment turning back. (G) Schematic drawing of the mechanism underlying the…

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  Fig. 3. Intracardiac electrocardiogram and fluoroscopic images. (A) During coronary sinus ostium pacing after radiofrequency applications, the sequence of the tricuspid annulus catheter remained unchanged as atrial flutter spontaneously recurred. This suggests that only a unidirectional block from the septal side to the lateral side was formed, and a bidirectional block had not been established. (B) The potentials of the cryoablation catheter at the successful freezing site just before freezing. (C) Fluoroscopic images of the successful cryoablation site. (D) A total of 50 s into the second freezing cycle, an extension in the tachycardia cycle length was observed, subsequently leading to the termination of the atrial flutter.