Cryoballoon Pulmonary Vein Isolation
Complete isolation of the pulmonary veins (PV) is considered the cornerstone of catheter intervention to treat atrial fibrillation (AF). PV isolation using a cryoballoon has evolved into a relatively simple alternative for point-by-point radiofrequency current (RFC) ablation because this technology theoretically allows for PV isolation with a single application. The technique has a steep learning curve and can be performed with fluoroscopic guidance without a 3-dimensional mapping system or additional imaging techniques.(1) To achieve continuous lesions, an occlusive balloon position at target PV sites as confirmed by PV angiography is necessary to limit convective heating by leaking blood flow (Figure 1). This may be challenging especially at the right inferior PV due to its proximity to the transseptal puncture site. However, using special catheter maneuvers based on the individual anatomy, complete PV isolation is possible in the great majority of patients (97%) with a single balloon and without additional "touch-up" lesions by a focal cryocatheter.(1) If PV occlusion cannot be achieved, the "pull-down" technique may be used, with freezing initiated at the superior PV circumference, accepting a small inferior leakage. When steady-state balloon temperature is achieved both the sheath and the frozen balloon are pulled down to close the inferior leakage. Successful ablations generally reach a minimal balloon temperature of -40°C or less.(2)
Balloon size also plays a role in possible collateral damage to the esophagus. In total, 116 patients have been included in 3 studies with systematic endoscopic screening for esophageal lesions after cryoballoon PV isolation (3). Esophageal ulcerations (6/35, 17%) were only reported in the study using both balloon sizes (and a focal cryocatheter if needed). In the remaining 81 patients from 2 studies employing a single 28mm balloon strategy, no esophageal lesion was found.(3,5) This may be explained by a deviation of the esophageal course from the midline in the great majority of patients, resulting in close proximity of the esophagus to the posteriorly directed inferior PVs. As of today, no atrio-esophageal fistula has been described following cryoballoon ablation, reported esophageal ulcerations healed without clinical sequelae.
A serious complication of PVI using RFC ablation is PV stenosis. Based on the definition of >75% reduction in cross-sectional area from baseline in non-invasive imaging studies, significant PV stenosis was for the first time reported in 7/228 (3.1%) patients following cryoballoon PVI in the North American Arctic Front STOP-AF trial (presented at the Annual Scientific Session in Atlanta, March 2010). Pending publication of the full results, it is unknown whether these cases were associated with a specific balloon size. Energy delivery inside the PV by an under-sized balloon, or "venoplasty" by inflation of an over-sized balloon within the PV are possible explanations. However, combined data from available studies indicate a low incidence (2/1163; 0.17%) of significant PV stenosis resulting in symptoms or requiring intervention.(3)
In patients with paroxysmal AF who underwent cryoballoon PV isolation, one-year freedom from recurrent AF has been reported in the range of 49-77% of patients, depending on whether or not a 3-month blanking period was employed. In persistent AF, one-year freedom from recurrent AF has been reported in 42-48% of patients.(3) Since patients with long-lasting persistent AF may need ablation strategies in addition to PVI to achieve higher success rates, these patients are not treated with cryoballoon ablation in our laboratory. As of today, only data from small non-randomized studies comparing the clinical efficacy of cryoballoon- to RFC-based PVI are available, which showed no difference between the techniques.(3) Sufficiently powered, randomized studies are in preparation.
In conclusion, our approach to cryoballoon PVI using only the single big (28 mm) balloon aims primarily for maximal patient safety. It is a straightforward "single-device" strategy. Large-scale, randomized trials will provide the answer to the important question relating to cryoballoon PVI – whether it constitutes a safer alternative to RFC-based PVI with comparable efficacy.
- Kuck K-H, Fürnkranz A. Cryoballoon ablation of atrial fibrillation. J. Cardiovasc. Electrophysiol. 2010;21(12):1427-1431.
- Fürnkranz A, Köster I, Chun KRJ, Metzner A, Mathew S, Konstantinidou M, Ouyang F, Kuck KH. Cryoballoon temperature predicts acute pulmonary vein isolation. Heart Rhythm. 2011, doi:10.1016/j.hrthm.2011.01.044.
- Andrade JG, Khairy P, Guerra PG, Deyell MW, Rivard L, Macle L, Thibault B, Talajic M, Roy D, Dubuc M. Efficacy and Safety of Cryoballoon Ablation for Atrial Fibrillation – A Systematic Review of Published Studies. Heart Rhythm. 2011, doi: 10.1016/j.hrthm.2011.03.050.
- Franceschi F, Dubuc M, Guerra PG, Delisle S, Romeo P, Landry E, Koutbi L, Rivard L, Macle L, Thibault B. Diaphragmatic electromyography during cryoballoon ablation: a novel concept in the prevention of phrenic nerve palsy. Heart Rhythm. 2011, doi:10.1016/j.hrthm.2011.01.031.
- Fürnkranz A, Chun KRJ, Metzner A, Nuyens D, Schmidt B, Burchard A, Tilz R, Ouyang F, Kuck KH. Esophageal endoscopy results after pulmonary vein isolation using the single big cryoballoon technique. J. Cardiovasc. Electrophysiol. 2010;21(8):869-874.
Keywords: Angiography, Atrial Fibrillation, Electromyography, Esophageal Fistula, Freezing, Heating, Palpation, Patient Safety, Phrenic Nerve, Pulmonary Veins, Punctures, Temperature
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