Introduction

Multiple important advances in ablation have taken place over the past year. Seminal articles in the ablation of atrial fibrillation (AF) and ventricular tachycardia (VT) were published.

Atrial Fibrillation

The multicenter FIRE AND ICE (Comparative Study of Two Ablation Procedures in Patients With Atrial Fibrillation) trial randomized 769 patients with paroxysmal AF to cryoballoon or radiofrequency ablation. This landmark trial showed that cryoballoon ablation was non-inferior to radiofrequency ablation in terms of the primary efficacy endpoint. In addition, safety analysis showed that both procedures have similar safety profiles.¹ The randomized AATAC (Ablation vs Amiodarone for Treatment of AFib in Patients With CHF and an ICD) trial, which included 203 patients with persistent AF, NYHA class II to III heart failure with reduced ejection fraction and an implantable cardioverter defibrillator, showed that catheter ablation is superior to amiodarone in preventing AF recurrence.² Furthermore, catheter ablation is associated with a significantly lower risk of unplanned hospitalization when compared to amiodarone, with a relative risk reduction of 45%, and a number needed to treat of 3.8.² A study on the long-term follow-up (up to 12 years) of pulmonary vein isolation (PVI) for paroxysmal AF in 513 patients, showed recurrence-free survival in 59% of patients from a single procedure and in 87% of patients after several ablations [up to 4].³ Another study evaluated the long-term results of cryoballoon ablation in patients with paroxysmal and persistent AF. Out of the 139 patients with paroxysmal AF, 47% remained free of symptomatic recurrence after a single procedure, versus 35.6% of the 61 patients with persistent AF with no statistically significant difference between the groups.⁴ However despite the procedural success and the efficacy of ablation procedures for AF, recurrences are common, and one study demonstrated that AF recurrence following PVI is associated with reduction in quality of life.⁵

A study by Al-Hijji et al. showed that approximately 1 in 8 patients who underwent ablation for AF will undergo a second procedure within 1 year. Demographic factors including younger age, higher household income, people living in southern regions of the USA, and patients with baseline antiarrhythmic drug (AAD) use predicted the need for repeat ablation.⁶ In another study, prolonged P wave duration (>120 ms), and increased P wave dispersion (>45 ms) were significant predictors of AF recurrence.⁷ Furthermore, PVI in patients with persistent AF while in sinus rhythm is significantly associated with a higher success rate, and shorter procedural time and fluoroscopy time compared to targeting complex-fractionated atrial electrograms along with PVI in patients with persistent AF while in AF.⁸ In addition, the Gap-Atrial Fibrillation-German Atrial Fibrillation Competence Network 1 (Gap-AF-AFNET 1) trial, which included 233 with paroxysmal AF, highlighted the importance of ensuring complete PVI during the procedure.⁹ A trial of 129 patients with paroxysmal AF evaluated the role of adenosine infusion following PVI and showed that although adenosine infusion unveils dormant pulmonary vein conduction, it has no effect on the rate of AF recurrence.¹⁰

Aryana et al. looked at procedural and biophysical indicators that predicted durable PVI in patients using cryoballoon ablation and found that time to effect (≤60 seconds) and interval thaw time at 0°C (≥10 seconds) were significant predictors of durable PVI.¹¹ The Efficacy of Antiarrhythmic Drugs Short-Term Use After Catheter Ablation for Atrial Fibrillation (EAST-AF) trial randomized patients after AF ablation to a group that received AADs (Class I or III) during the first 90 days after the procedure (blanking period) and a group that received placebo during the same period. The trial showed that although during the 90-day treatment period the patients in the AAD group had a significantly higher event-free survival compared to the placebo group, after discontinuation of the AAD at 90 days, there was no significant difference in the event-free survival between the 2 groups.¹²

Finally, two meta-analyses examined the efficacy and safety of new oral anticoagulants (NOAC) as an alternative to vitamin K antagonists (VKA) in the peri-procedure period of catheter ablation for AF. The first meta-analysis, which included 1105 patients, compared apixaban to uninterrupted VKA therapy. The results showed that there were no significant differences between apixaban and VKAs in terms of major bleeding, minor bleeding, and the risk of thromboembolism.¹³ Another meta-analysis (more than 11,000 patients) compared NOACs to continuous VKAs. The results showed that NOACs were similar to continuous VKAs in terms of ischemic stroke or transient ischemic attack prevention, and the risk of major bleeding. However NOACs had a significantly lower risk of minor bleeding compared to continuous VKA.¹⁴

Ventricular Tachycardia

After approval of the ThermoCool® catheter for ventricular tachycardia (VT) ablation following the THERMOCOOL VT (NaviStar ThermoCool Catheter for Endocardial RF Ablation in Patients With Ven- tricular Tachycardia) trial, Marchlinski et al. showed long-term efficacy and safety of VT ablation in patients with coronary artery disease.¹⁵

The Ventricular Tachycardia Ablation versus Escalated Antiarrhythmic Drug Therapy in Ischemic Heart Disease (VANISH) trial showed that catheter ablation for VT was superior to escalated AAD therapy in 259 patients with a previous myocardial infarction and implantable cardioverter defibrillator (ICD) insertion (who had an episode of VT in the past 6 months while on amiodarone or other class I or III AAD), in terms of reducing the composite endpoint of death at any time after randomization, or VT storm or appropriate ICD shock after a 30-day period.¹⁶ A meta-analysis by Patel et al. showed superiority of catheter ablation for VT to non-ablative strategies in patients with ischemic heart disease and ICDs in terms of VT recurrence.¹⁷

A retrospective study compared VT ablation in patients with New York Heart Association (NYHA) IV heart failure (HF), to those with NYHA II or III HF in the International VT Ablation Center Collaborative Group (IVTCC) cohort. This study, which included 111 patients with NYHA IV HF, and 1,254 patients with NYHA II or III HF, showed that despite the fact that patients with NYHA IV HF had significantly worse baseline characteristics, more comorbidities, and more procedural complexities than patients with NYHA II or III, VT ablation is a procedure that can be safely performed in patients with NYHA IV. The rate of 1-year recurrence was similar between the groups; however, patients with NYHA IV were more likely to experience the recurrence earlier than those with NYHA II or III. Survival was similar between patients with NYHA II or II with recurrence, and patients with NYHA IV without recurrence. However, patients with NYHA IV HF and VT recurrence had a significantly worse survival than patients with NYHA II or III HF and VT recurrence.¹⁸

In another study, cryoenergy (≥10 seconds) was associated with significantly lower recurrence rate when compared to radiofrequency ablation of ventricular arrhythmias originating from papillary muscles.¹⁹

A study done on 20 patients to determine whether VT recurrence following ablation in patients with arrhythmogenic right ventricular dysplasia and non-ischemic cardiomyopathy was due to disease progression or incomplete ablation, showed that most (70%) of the repeat ablations were done on the original scar, indicating that incomplete ablation plays a role in VT recurrence.²⁰

A recent study on the safety of left ventricular endocardial catheter ablation for VT and premature ventricular complexes showed that more than half of the 12 patients who underwent LV endocardial ablation developed cerebral emboli.²¹ There is a need for larger studies to determine the real risk of cerebral emboli, the long-term effects of these emboli, and ways to prevent them.

In a prospective observational study by Cano et al., the CartoUnivu module for VT ablation in patients with VT and structural heart disease was evaluated. This module integrates fluoroscopy images with electroanatomic mapping images, and aims to reduce fluoroscopy during ablation. Patients in the ischemic VT group had a significantly lower radiation exposure compared to those in the non-ischemic group. In a subset of patients, a near-zero fluoroscopy procedure was possible [effective dose≤ 1mSv].²²

The Study to Obliterate Persistent Ventricular Tachycardia (STOP-VT) trial assessed the efficacy and safety of remote magnetic navigation (RMN) for VT ablation. RMN appears to be a feasible, effective and safe modality for VT ablation; however larger, controlled and adequately powered clinical trials are needed for definitive evaluation of this modality.²³

References

1. Kuck KH, Brugada J, Fürnkranz A, , et al. Cryoballoon or Radiofrequency Ablation for Paroxysmal Atrial Fibrillation. N Engl J Med 2016;374:2235-45.
2. Di Biase L, Mohanty P, Mohanty S, et al. Ablation Versus Amiodarone for Treatment of Persistent Atrial Fibrillation in Patients With Congestive Heart Failure and an Implanted Device: Results From the AATAC Multicenter Randomized Trial. Circulation 2016;133:1637-44.
3. Gökoğlan Y, Mohanty S, Güneş MF, et al. Pulmonary Vein Antrum Isolation in Patients With Paroxysmal Atrial Fibrillation: More Than a Decade of Follow-Up. Circ Arrhythm Electrophysiol 2016;9.
4. Davies AJ, Jackson N, Barlow M, Leitch J. Long Term Follow-up of Pulmonary Vein Isolation Using Cryoballoon Ablation. Heart, Lung and Circulation 2016;25:290-5.
5. Berger WR, Krul SP, van der Pol JA, et al. Documented atrial fibrillation recurrences after pulmonary vein isolation are associated with diminished quality of life. J Cardiovasc Med (Hagerstown) 2016;17:201-8.
6. Al-Hijji MA, Deshmukh AJ, Yao X, et al. Trends and predictors of repeat catheter ablation for atrial fibrillation. Am Heart J 2016;171:48-55.
7. Mugnai G, Chierchia GB, de Asmundis C, et al. P-wave indices as predictors of atrial fibrillation recurrence after pulmonary vein isolation in normal left atrial size. J Cardiovasc Med (Hagerstown) 2016;17:194-200.
8. Bassiouny M, Saliba W, Hussein A, et al. Randomized Study of Persistent Atrial Fibrillation Ablation: Ablate in Sinus Rhythm Versus Ablate Complex-Fractionated Atrial Electrograms in Atrial Fibrillation. Circ Arrhythm and Electrophysiol 2016;9:e003596.
9. Kuck KH, Hoffmann BA, Ernst S, et al. Impact of Complete Versus Incomplete Circumferential Lines Around the Pulmonary Veins During Catheter Ablation of Paroxysmal Atrial Fibrillation: Results From the Gap-Atrial Fibrillation-German Atrial Fibrillation Competence Network 1 Trial.. Circ Arrhythm and Electrophysiol 2016;9:e003337.
10. Ghanbari H, Jani R, Hussain-Amin A, et al. Role of adenosine after antral pulmonary vein isolation of paroxysmal atrial fibrillation: A randomized controlled trial. Heart Rhythm 2016;13:407-15.
11. Aryana A, Mugnai G, Singh SM, et al. Procedural and biophysical indicators of durable pulmonary vein isolation during cryoballoon ablation of atrial fibrillation. Heart Rhythm 2016;13:424-32.
12. Kaitani K, Inoue K, Kobori A, et al. Efficacy of Antiarrhythmic Drugs Short-Term Use After Catheter Ablation for Atrial Fibrillation (EAST-AF) trial. Eur Heart J 2016;37:610.
13. Lu D, Liu Q, Wang KAI, Zhang QI, Shan QJ. Meta-Analysis of Efficacy and Safety of Apixaban in Patients Undergoing Catheter Ablation for Atrial Fibrillation. Pacing Clin Electrophysiol 2016;39:54-9.
14. Wu S, Yang YM, Zhu J, Wan HB, Wang J, Zhang H, Shao XH. Meta-Analysis of Efficacy and Safety of New Oral Anticoagulants Compared With Uninterrupted Vitamin K Antagonists in Patients Undergoing Catheter Ablation for Atrial Fibrillation. Am J Cardiol 2016;117:926-34.
15. Marchlinski FE, Haffajee CI, Beshai JF, et al. Long-Term Success of Irrigated Radiofrequency Catheter Ablation of Sustained Ventricular Tachycardia: Post-Approval THERMOCOOL VT Trial. J Am Coll Cardiol 2016;67:674-83.
16. Sapp JL, Wells GA, Parkash R, et al. Ventricular Tachycardia Ablation versus Escalation of Antiarrhythmic Drugs. N Engl J Med 2016;375:111-21.
17. Patel D, Hasselblad V, Jackson KP, Pokorney SD, Daubert JP, Al-Khatib SM. Catheter ablation for ventricular tachycardia (VT) in patients with ischemic heart disease: a systematic review and a meta-analysis of randomized controlled trials. J Interv Card Electrophysiol 2016;45:111-7.
18. Tzou WS, Tung R, Frankel DS, et al. Ventricular Tachycardia Ablation in Severe Heart Failure: An International Ventricular Tachycardia Ablation Center Collaboration Analysis. Circ Arrhythm Electrophysiol 2017;10.
19. Rivera S, Ricapito MdlP, Tomas L, et al. Results of Cryoenergy and Radiofrequency-Based Catheter Ablation for Treating Ventricular Arrhythmias Arising From the Papillary Muscles of the Left Ventricle, Guided by Intracardiac Echocardiography and Image Integration. Circ Arrhythm Electrophysiol 2016;9:e003874.
20. Berte B, Sacher F, Venlet J, et al. VT Recurrence After Ablation: Incomplete Ablation or Disease Progression? A Multicentric European Study. J Cardiovasc Electrophysiol 2016;27:80-7.
21. Whitman IR, Gladstone RA, Badhwar N, et al. Brain Emboli After Left Ventricular Endocardial Ablation. Circulation 2017 [epub ahead of print].
22. Cano Ó, Andrés A, Osca J, Alonso P, Sancho-Tello M-J, Olagüe J, Martínez-Dolz L. Safety and Feasibility of a Minimally Fluoroscopic Approach for Ventricular Tachycardia Ablation in Patients With Structural Heart Disease. Circ Arrhythm Electrophysiol 2016;9:e003706.
23. Skoda J, Arya A, Garcia F, et al. Catheter Ablation of Ischemic Ventricular Tachycardia With Remote Magnetic Navigation: STOP-VT Multicenter Trial. J Cardiovasc Electrophysiol 2016;27 Suppl 1:S29-37.

Keywords: Adenosine, Amiodarone, Anti-Arrhythmia Agents, Anticoagulants, Arrhythmogenic Right Ventricular Dysplasia, Atrial Fibrillation, Catheter Ablation, Cicatrix, Comorbidity, Coronary Artery Disease, Cytarabine, Defibrillators, Implantable, Disease Progression, Electrophysiologic Techniques, Cardiac, Fluoroscopy, Heart Failure, Intracranial Embolism, Ischemic Attack, Transient, Myocardial Infarction, Papillary Muscles, Pulmonary Veins, Pyrazoles, Pyridones, Risk, Stroke, Tachycardia, Ventricular, Vitamin K

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