New Painless Cryoablation Technique for the Treatment of Isthmus-Dependent Atrial Flutter

Sizeable lesions are required to achieve permanent bidirectional conduction block in the cavotricuspid isthmus for the treatment of typical atrial flutter. Currently, radiofrequency (RF) ablation has a high clinical success rate in more than 85% and a low recurrence rate.1 Cryoablation with an 8 mm tip catheter using a new catheter positioning technique may be of greater effectiveness in comparison to ablation with the standard approach with either RF or cryo. Recent studies show that cryoablation of the cavotricuspid isthmus results in essentially pain-free ablation.² This is contrast to the considerable pain that patients may experience during radiofrequency ablation of the isthmus (although this issue has not been systematically studied). This article provides: 1) a description of the new catheter positioning technique for the treatment of typical atrial flutter; and 2) an illustrative case study that demonstrates the strength of the technique both in terms of clinical effectiveness and absence of patient discomfort. Better tip/tissue interface for increased effectiveness in the treatment of atrial flutter Effective cryoablation of the cavotricuspid isthmus requires the creation of lesions sizeable enough to produce a permanent bidirectional conduction block. Larger lesions can be produced by increasing tip/tissue contact. Consequently, we developed a new catheter positioning technique, using a cryocatheter with an 8 mm tip, which results in increased tip/tissue interface and thermal transport capacity. We refer to this technique as the sigma curve position. To ablate the cavotricuspid isthmus using the sigma curve technique, the cryocatheter is placed at a 90 º angle to the intended ablation line between the tricuspid valve and the inferior vena cava. The catheter tip positioned in the inferior isthmus points septally. The first intended ablation site using the sigma curve technique should be as close to the tricuspid annulus as possible. This is followed by a second ablation site with the catheter positioned at the Eustachian ridge/IVC junction (Figures 1 and 2). It should be noted that one or two additional applications may be performed in between the two sites for optimal results with the sigma curve technique. Following the ablations with the sigma curve technique, the ablation sites will be connected using the standard approach by creating a further ablation line in the cavotricuspid isthmus between the tricuspid valve and the inferior vena cava the catheter tip points to the tricuspid valve (Figures 3 and 4). The use of both the standard approach and the sigma curve technique in this manner using a cryoablation catheter is effective in achieving a bidirectional isthmus conduction block.

---

Patient profile. A 74-year-old man with a 3-month history of palpitations and documented typical atrial flutter was referred to our center for electrophysiology evaluation and ablation. Procedure. After two venous sheaths were placed in the right femoral vein, a multi-polar Halo catheter (Biosense Webster Inc., Diamond Bar, California) was positioned in the right atrium and in the coronary sinus following documentation of counterclockwise atrial flutter with a cycle length of 212 ms (Figure 5). A 9 French steerable Freezor MAX catheter from CryoCath Technologies with a 8 mm tip was positioned in the cavotricuspid isthmus. The sigma curve position was used for the first cryoablation at the tricuspid valve annulus, followed by a second cryoablation at the Eustachion ridge/IVC junction. During the latter cryo application, the atrial flutter terminated as the catheter tip was cooled to -80 °C (cumulative cryo time, 265 seconds). The arrhythmia terminated (Figure 6) with verification of unidirectional conduction block. While stimulating in the coronary sinus, a gap was mapped and two more cryoablations were performed using the standard approach. The presence of a bidirectional conduction block (Figure 7) in the inferior isthmus was verified immediately. Results. Four 240-second applications were required to produce bidirectional conduction block. Thirty minutes following the final energy delivery, bidirectional conduction block was reconfirmed, and the patient left the electrophysiology laboratory in sinus rhythm. Our laboratory uses a visual analogue scale from zero (no pain) to 100 (worst pain imaginable) to grade procedure-related pain.3 In this particular case, the patient reported no procedure-related pain (zero on the pain scale), and no complications were noted. In addition, as part of an ongoing investigative protocol, an invasive control-stimulation was performed on this patient 32 days post ablation. On this occasion, bidirectional conduction block in the cavotricuspid isthmus was verified, and the patient remained clinically asymptomatic. Discussion. Cryoadhesion provided very stable catheter positioning in this case; consequently, fluoroscopic images were not required during any of the cryo applications. The sigma curve technique allowed us to achieve bidirectional conduction block quickly by optimizing catheter contact in areas that have previously been difficult to ablate with the standard approach. Using this painless ablation method, sizeable lesions can be created to achieve a permanent bidirectional conduction block in the inferior isthmus as an effective treatment of typical atrial flutter. Note: Freezor ® MAX is not available for sale in the United States.