Hope or Hype – Does Cryoballoon Simplify Atrial Fibrillation Ablation Technique or Just Another Costly Toy? –
論文ID: CJ-16-0622
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論文ID: CJ-16-0622
Radiofrequency (RF) energy for catheter ablation of atrial fibrillation (AF) has been a therapeutic option since the reports from Haïssaguerre et al1 and Chen et al.2 Electrical isolation of the pulmonary veins (PVs) is the cornerstone and established endpoint of AF ablation.3–5 Combining RF catheter ablation and a 3D electroanatomic mapping system has become a worldwide procedure in the past 10 years. However, it is time-consuming using the catheter tip to isolate the PVs using a point-by-point technique. A single-shot method to speed up and simplify the procedure has been introduced since the use of the balloon catheter. It can ablate a larger area of tissue at once than the conventional tipped catheters. But the balloon-based ablation technique is not yet recommended to treat persistent or long-standing persistent AF. The available energy sources for the balloon device are cryo (Arctic Front), laser (HeartLight) or RF energy (Hot balloon). Of these different techniques, cryoablation has emerged as an important alternative to RF ablation because of better safety profiles, including less thrombogenicity and less risk of perforation.6–13 Because of sufficient evidence, it was approved for AF treatment by the CE marketing regulation in 2005 and by the US FDA in December 2010.
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The first randomized, multicenter trial for cryoablation (STOP-AF trial) reported the superior efficacy of 1st-generation cryoballoon ablation compared with antiarrhythmic medication.6 The trial demonstrated that cryoablation is a safe and effective alternative to antiarrhythmic medication for patients with symptomatic paroxysmal AF. The 1-year freedom from AF rate was 69.9% in that study, with significantly improved symptoms. A similar 1-year AF-free rate of cryoablation was also reported from another 8-year-experience study, with a continuous increase in the 1-year success rate with successive years of study, suggesting the importance of the learning curve for this new ablation technology.7 Although cryoablation isolates the PVs in a simple way, recent registry and prospective randomized trials reported comparable efficacy between RF and cryoablation after a 1-year of follow-up.8,9 The Table shows moderate sample size reports published in the past 2 years. Most of the studies demonstrated a similar efficacy between cryoablation and irrigated-tip RF ablation for paroxysmal AF.8–12 In most studies, procedural duration was shorter and fluoroscopic exposure a little longer than with conventional RF ablation with 3D mapping system. Nevertheless, efficacy is not the only issue we need to consider; safety is also paramount before making this ablation technique available to most operators, including less experienced doctors. When cryoablation was first applied by experienced electrophysiologists, some serious complications were observed. For example, phrenic nerve paralysis, which occurred in 5–10% of patients after cryoablation, although most cases were transient and asymptomatic.8–12 There are also concerns of collateral damage to neighboring soft tissues, including the esophagus or bronchus. How to adjust for adequate energy and freezing duration in order to avoid these complications or collateral damage is still unclear and whether a bonus lesion is required after acute PV isolation is also a debatable issue.
| Study | Patient no. RF/CA |
CB generation | Follow-up (months) |
RF/CA success (%) |
P value | PNP in CA group (%) |
|---|---|---|---|---|---|---|
| Mugnai et al10 | 260/132 | 1st | 23±13 | 57/63 | 0.25 | 8.1 |
| Aryana et al11 | 593/320 | 2nd | 6 | 61/78 | <0.001 | 8.8 |
| Luik et al8 | 159/156 | 1st and 2nd | 6 | 63/64 | NS | 5.8 |
| Schmidt et al9 | 1,699/607 | 1st | 12 | 55/54 | 0.87 | 2.2 |
| Khoueiry et al12 | 376/311 | 1st and 2nd | 14±8 | 86/83 | 0.25 | 0 |
AF, atrial fibrillation; CA, cryoablation; CB, cryoballoon; NS, non-significant; PNP, phrenic nerve paralysis; RF, radiofrequency.
Apart from these efficacy and safety considerations, when applying clinical trial results to test general populations, only the indications and contraindications regulated. Will the outcomes of those trials be translated to our daily practice? In the real world, there is limited guidance for problematic cases, not the strict regulation in the study protocol of clinical trials. Therefore, the post-market surveillance (PMS) might be closer and more reflective of the clinical scenario. The authors are to be congratulated for their excellent work in reporting the PMS of the safety and efficacy of cryoablation in Japan.13 The study enrolled 660 symptomatic AF patients from 33 Japanese hospitals. By using the 2nd-generation cryoballoon, procedural efficacy reached 88.4% at 6-month follow-up of. As for safety concerns, only 3.7% device-related and 3.9% procedure-related events were observed. These study results are consistent with the outcomes reported in other global trials of the effectiveness of cryoballoon.8–12 Although this study was a PMS, the safety outcome seems not a significant problem with new cryoballoon users.
As far as the procedural simplicity, safety and technical approachability for new users are concerned, are we now confident to say paroxysmal AF ablation is the first-line therapy before antiarrhythmic medication and a contender for opening up AF ablation to non-EP interventional cardiologists? The electrophysiology of AF is complex; despite this convenient technique, we still need careful consideration of the procedural endpoints to achieve a better outcome. Non-PV ectopy accounts for 5–10% in paroxysmal AF patients, and it is even higher in Asian populations and persistent AF cases.14 By using cryoablation only, we will miss those AF triggers. If atypical atrial flutter develops after PV isolation, additional RF ablation is still required. Ganglinated plexi ablation can modulate the procedural outcome.15 Unfortunately, we currently do not have enough evidence of the effects of freezing on the intrinsic cardiac autonomic activity. Incomplete denervation has also been reported to cause pro-arrhythmogeneity. Besides, PV anatomical variants (eg, common ostium, middle PV) are not uncommon. Operators need to learn how to adapt the cryoballoon to those anatomical variations. Thus, cryoablation does not just simplify the ablation approach, it also provokes our thoughts on the fundamentals of AF knowledge, not just isolating the PVs per se and go. This is the beauty and attraction of electrophysiology!
There are multiple mechanisms of AF and current ablation results are still not satisfactory. Cryoablation provides a simple ablation approach and saves time spent on the first step of AF treatment. Looking at it another way, if we save more time in the first step, then we can take more time to identify the AF mechanism or modify the diseased atrial substrate, in order to improve the long-term AF ablation outcome.
The present work was supported by the Taipei Veterans General Hospital (V104E7-003, VA105C-60), Ministry of Science and Technology (MOST 103-2314-B-075-062-MY3, MOST 104-2314-B-075-065-MY2).
The authors have no conflicts of interest to declare.
