Cryoballoon ablation of atrial fibrillation: a practical and effective approach

Abstract

Medical management of atrial fibrillation (AF), the most common arrhythmia in the general population, has had modest efficacy in controlling symptoms and restoring and maintaining sinus rhythm. Since the seminal observation in 1998 that pulmonary veins host the triggers of AF in the majority of cases, electrical isolation of all pulmonary veins constitutes the cornerstone of ablation in patients with symptomatic AF. However, due to the elaborate and tedious technique of the conventional point-by-point method with radiofrequency ablation guided by electroanatomical mapping, newer, more versatile single-shot techniques, such as cryoballoon ablation, have been sought and developed over recent years and are progressively prevailing. Cryoballoon ablation appears to be the most promising practical and effective approach, and we review it here by presenting all available relevant data from the literature as well as from our own experience in an attempt to apprise colleagues of the significant progress made over the last several years in this important field of electrophysiology.

Keywords: atrial fibrillation; catheter ablation; cryoablation; cryoballoon; pulmonary vein isolation; radiofrequency.

Figure 1

(A) The components of the balloon: the refrigerant (N₂O) is delivered into the inner balloon through the injection tube and vacuumed back into the console during the freezing/unfreezing process. The thermocouple monitors the temperature of the vaporized refrigerant. The outer balloon is maintained under vacuum and constitutes a safety feature to reinforce and protect the inner balloon in case of accidental compromise. The circular mapping catheter (not shown) is deployed through the cryoballoon guidewire lumen, may guide the balloon into the PV, and also provides recordings of real‐time PV potentials before, during, and after cryoablation. The distal mapping section of the mapping catheter is a circular loop with 8 evenly spaced electrodes for mapping and cardiac stimulation. When the balloon is positioned at the PV antrum, contrast dye is injected through the guidewire lumen to assess vein occlusion via fluoroscopy. Comparing the design of (B) the CB1 and (C) CB2 cryoballoons, one notes the difference of the relatively narrow band‐like cooling zone in CB1 (arrows) and the extended span of the cooling zone of CB2, which encompasses the entire distal half of its surface including the distal tip (arrows). This new design produces a larger cooling surface area and reduces additional maneuvering for better balloon positioning for optimal tissue contact. Abbreviations: CB, cryoballoon; N₂O, nitrous oxide; PV, pulmonary vein. (materials for the figure were used with the permission of Medtronic, Inc.© 2016)

Figure 2

An actual case of a patient undergoing AF cryoablation. After accessing the left atrium via a transseptal approach, PV angiography performed via the delivery sheath allows for (A) imaging of the target PV, here the left PVs (arrow). Then the balloon catheter is advanced to (B) the PV antrum, with the circular mapping catheter inserted into the left inferior PV (black arrow), and the balloon is inflated and pushed against the antrum to occlude the PV (white arrow). Occlusion is assessed fluoroscopically by contrast injection into the PV, and when local dye stasis with no backflow is observed, the freezing process is commenced and the balloon ablates the tissue circumferentially. Upon completion of the freezing application, the balloon is deflated and the circular mapping catheter, if too distal, is (C) withdrawn proximally (arrow) to allow for PV potential recording. PV isolation is confirmed when (D) the PV potentials (arrows) are (E) eliminated. In many cases, current technology may allow real‐time observation of PV potential elimination during cooling. Abbreviations: AF, atrial fibrillation; PV, pulmonary vein.