EDITORIAL COMMENTARY
Simplified pulmonary vein isolation: Are we there yet? Christopher F. Liu, MD, FHRS From the Division of Cardiology, Department of Medicine, Weill Cornell Medical College, New York, New York. Since the observation by Haissaguerre et al1 that triggers of atrial fibrillation (AF) mapped to the pulmonary veins (PVs), circumferential PV isolation has become the cornerstone of most AF ablation strategies.2 As efforts have been made to improve the efficacy and safety of PV isolation, there also has been a push to simplify the circumferential ablation process in order to reduce the learning curve and expedite this time-consuming procedure. The ongoing challenge of the catheter-based ablation procedure remains: How can we best deliver a complex lesion set in a beating heart? As with all procedures, the answer lies in the interplay of the operator’s skills and the available tools. For many years, the only available technology for ablation involved a focal catheter, delivering unipolar radiofrequency (RF) energy between the catheter tip and a surface patch electrode. The first major technological improvement in AF ablation involved saline irrigation of the focal RF catheter. By reducing the temperature at the electrode-tissue interface, irrigation reduced the incidence of char formation and simultaneously enabled higher power delivery.3 Despite the advent of steerable sheaths, a high level of manual skill is still required for precise point-to-point movement of the focal ablation catheter in order to achieve a truly contiguous lesion set, which remains a time-consuming procedure.4 Given the approximately circular shape of the PV ostia, more recent ablation platforms have logically been built with circumferential energy delivery. Of the balloon-based ablation platforms, the high-intensity focused ultrasound balloon has been largely abandoned owing to safety concerns.5 The laser balloon continues to undergo clinical evaluation in the United States. As a true single-shot PV isolation tool, the cryoballoon has achieved widespread use in recent years, with efficacy and safety data comparable to those of focal RF ablation.6 Other variations of this theme have combined the circular mapping catheter and the focal ablation catheter into 1 tool, obviating the need for a second transseptal catheter. Furthermore, since energy delivery to each circumferential electrode is individually controlled, these platforms allow the choice of Disclosure: Dr. Liu has received a research grant from Biosense Webster for an unrelated project. Address reprint requests and correspondence: Dr Christopher F. Liu, Division of Cardiology, Department of Medicine, Weill Cornell Medical College, 520 E 70th St, Starr-4, New York, NY 10021. E-mail address: [email protected].
1547-5271/$-see front matter B 2014 Heart Rhythm Society. All rights reserved.
large segment or focal ablation, giving even more conceptual appeal. Unfortunately, circumferential RF ablation tools have not delivered on their promise thus far. The high-density mesh ablator has been largely abandoned owing to high reconnection rates associated with poor clinical efficacy.7 The 10-pole PV ablation catheter (PVAC) was designed from a typical circular mapping catheter shape and is capable of delivering duty-cycled unipolar and bipolar RF energy, thereby potentially creating a contiguous circumferential lesion with minimal repositioning requirement. The initial data appeared quite promising with regard to shorter procedural times and short-term success rates comparable to those of focal irrigated RF ablation.8 However, increased understanding of and vigilance for asymptomatic cerebral emboli (ACE) revealed an alarmingly high incidence of these lesions after PVAC ablation.9 Animal and human studies have now suggested that when poles are in proximity, RF delivery, especially bipolar current, is associated with increased microbubbles and subsequent ACE lesions on magnetic resonance imaging.10,11 This suggests that ACE lesions are associated with overheating of the local blood pool. As the PVAC languishes in the approval process in the United States, one wonders at what point is the simplicity and elegance of the design overwhelmed by the complicating factors of large area ablation? It is in this setting that the nMARQ irrigated circular decapolar mapping and ablation catheter (Biosense Webster Inc, Diamond Bar, CA) makes its entrance. In this issue of HeartRhythm, Shin et al12 describe their experience of using the nMARQ ablation system to perform PV isolation in 25 patients. The conceptual advantage of the nMARQ ablation system over the previous multielectrode ablation systems is the presence of irrigation, which theoretically provides the same benefit that it brought to focal RF ablation: lowering the electrode temperature to reduce charring and allow higher power delivery. The authors report complete acute success in isolating all PVs in this series without the need for a focal catheter. With a reportedly rapid learning curve, procedure and fluoroscopy times were short compared with published data for other ablation systems, although this type of comparison has significant caveats. There were no acute procedure-related complications, and cardiac magnetic resonance imaging performed in all patients 1–2 days after ablation showed no significant PV stenosis—although this was compared with radiographically estimated PV diameter http://dx.doi.org/10.1016/j.hrthm.2013.12.026
Liu
Editorial Commentary
from the intraprocedural left atrial angiogram. Charring on the nMARQ ablation system was noted in 3 procedures; all 3 had delivered bipolar ablation. Follow-up clinical data were available for an average of just over 4 months. Given that this was a feasibility report and not an outcomes study, the nMARQ ablation system has passed an initial test —that of expediency and acute efficacy in PV isolation. However, in our contemporary stage of progress in AF ablation, there are many more essential tests to be taken. With regard to safety, as referenced by the authors, there has already been a reported case of pericardial-esophageal fistula associated with the nMARQ ablation system.13 In addition, irrigation does not prevent charring on overlapping electrodes delivering energy simultaneously, as seen in this series. Another series has reported a high incidence of ACE lesions, similar to previous reports of the PVAC, as well as a high incidence of thermal esophageal lesions.14 With regard to postprocedural efficacy, the durability of PV isolation has become the ultimate test of all PV isolation procedures. In this study, there was no specified waiting period or provocation testing with adenosine or isoproterenol—tools to assess for dormant conduction or possible early recovery of conduction. Fortunately, phrenic nerve palsy has not been reported. As contact force sensing becomes more mature as an adjunctive tool for focal ablation, it is unclear how that technology might be incorporated into a multielectrode platform such as the nMARQ ablation system. Finally, shortand long-term clinical outcomes will be needed. Just like the early stages of focal RF ablation and cryoballoon ablation, there are undoubtedly many lessons to be learned in how to precisely use the nMARQ ablation system to maximize its benefit and minimize its risk. It remains to be seen whether the nMARQ ablation system will go the route of the cryoballoon or the high-intensity focused ultrasound balloon. One thing is clear: Despite the visual simplicity of the final circles of ablation seen on 3dimensional maps, PV isolation will remain a complex procedure, with a myriad of considerations for balancing the extent of permanent myocardial tissue destruction with reduction of complications.
385
References 1. Haissaguerre M, Jais P, Shah DC, et al. Spontaneous initiation of atrial fibrillation by ectopic beats originating in the pulmonary veins. N Engl J Med 1998;339: 659–666. 2. Calkins H, Kuck KH, Cappato R, et al. 2012 HRS/EHRA/ECAS expert consensus statement on catheter and surgical ablation of atrial fibrillation: recommendations for patient selection, procedural techniques, patient management and follow-up, definitions, endpoints, and research trial design: a report of the Heart Rhythm Society (HRS) Task Force on catheter and surgical ablation of atrial fibrillation. Heart Rhythm 2012;9:632–696. 3. Wittkampf FH, Nakagawa H, Foresti S, Aoyama H, Jackman WM. Salineirrigated radiofrequency ablation electrode with external cooling. J Cardiovasc Electrophysiol 2005;16:323–328. 4. Hutchinson MD, Garcia FC, Mandel JE, et al. Efforts to enhance catheter stability improve atrial fibrillation ablation outcome. Heart Rhythm 2013;10: 347–353. 5. Neven K, Metzner A, Schmidt B, Ouyang F, Kuck KH. Two-year clinical followup after pulmonary vein isolation using high-intensity focused ultrasound (HIFU) and an esophageal temperature-guided safety algorithm. Heart Rhythm 2012;9: 407–413. 6. Packer DL, Kowal RC, Wheelan KR, et al. STOP AF Cryoablation Investigators. Cryoballoon ablation of pulmonary veins for paroxysmal atrial fibrillation: first results of the North American Arctic Front (STOP AF) pivotal trial. J Am Coll Cardiol 2013;61:1713–1723. 7. Steinwender C, Honig S, Leisch F, Hofmann R. One-year follow-up after pulmonary vein isolation using a single mesh catheter in patients with paroxysmal atrial fibrillation. Heart Rhythm 2010;7:333–339. 8. Bittner A, Monnig G, Zellerhoff S, et al. Randomized study comparing dutycycled bipolar and unipolar radiofrequency with point-by-point ablation in pulmonary vein isolation. Heart Rhythm 2011;8:1383–1390. 9. Herrera Siklody C, Deneke T, Hocini M, et al. Incidence of asymptomatic intracranial embolic events after pulmonary vein isolation: comparison of different atrial fibrillation ablation technologies in a multicenter study. J Am Coll Cardiol 2011;58:681–688. 10. Haines DE, Stewart MT, Dahlberg S, et al. Microembolism and catheter ablation, I: a comparison of irrigated radiofrequency and multielectrode-phased radiofrequency catheter ablation of pulmonary vein ostia. Circ Arrhythm Electrophysiol 2013;6:16–22. 11. Wieczorek M, Lukat M, Hoeltgen R, et al. Investigation into causes of abnormal cerebral MRI findings following PVAC duty-cycled, phased RF ablation of atrial fibrillation. J Cardiovasc Electrophysiol 2013;24:121–128. 12. Shin D-I, Kirmanoglou K, Eickholt C, et al. Initial results of using a novel irrigated multielectrode mapping and ablation catheter for pulmonary vein isolation. Heart Rhythm 2014;11:375–383. 13. Deneke T, Schade A, Diegeler A, Nentwich K. Esophago-pericardial fistula complicating atrial fibrillation ablation using a novel-irrigated radiofrequency multipolar ablation catheter. J Cardiovasc Electrophysiol 2013;Epub ahead of print 14. Deneke T, Schade A, Müller P, et al. Acute safety and efficacy of a novel multipolar irrigated radiofrequency ablation catheter for pulmonary vein isolation. J Cardiovasc Electrophysiol 2013;Epub ahead of print
Simplified pulmonary vein isolation: Are we there yet? Christopher F. Liu, MD, FHRS From the Division of Cardiology, Department of Medicine, Weill Cornell Medical College, New York, New York. Since the observation by Haissaguerre et al1 that triggers of atrial fibrillation (AF) mapped to the pulmonary veins (PVs), circumferential PV isolation has become the cornerstone of most AF ablation strategies.2 As efforts have been made to improve the efficacy and safety of PV isolation, there also has been a push to simplify the circumferential ablation process in order to reduce the learning curve and expedite this time-consuming procedure. The ongoing challenge of the catheter-based ablation procedure remains: How can we best deliver a complex lesion set in a beating heart? As with all procedures, the answer lies in the interplay of the operator’s skills and the available tools. For many years, the only available technology for ablation involved a focal catheter, delivering unipolar radiofrequency (RF) energy between the catheter tip and a surface patch electrode. The first major technological improvement in AF ablation involved saline irrigation of the focal RF catheter. By reducing the temperature at the electrode-tissue interface, irrigation reduced the incidence of char formation and simultaneously enabled higher power delivery.3 Despite the advent of steerable sheaths, a high level of manual skill is still required for precise point-to-point movement of the focal ablation catheter in order to achieve a truly contiguous lesion set, which remains a time-consuming procedure.4 Given the approximately circular shape of the PV ostia, more recent ablation platforms have logically been built with circumferential energy delivery. Of the balloon-based ablation platforms, the high-intensity focused ultrasound balloon has been largely abandoned owing to safety concerns.5 The laser balloon continues to undergo clinical evaluation in the United States. As a true single-shot PV isolation tool, the cryoballoon has achieved widespread use in recent years, with efficacy and safety data comparable to those of focal RF ablation.6 Other variations of this theme have combined the circular mapping catheter and the focal ablation catheter into 1 tool, obviating the need for a second transseptal catheter. Furthermore, since energy delivery to each circumferential electrode is individually controlled, these platforms allow the choice of Disclosure: Dr. Liu has received a research grant from Biosense Webster for an unrelated project. Address reprint requests and correspondence: Dr Christopher F. Liu, Division of Cardiology, Department of Medicine, Weill Cornell Medical College, 520 E 70th St, Starr-4, New York, NY 10021. E-mail address: [email protected].
1547-5271/$-see front matter B 2014 Heart Rhythm Society. All rights reserved.
large segment or focal ablation, giving even more conceptual appeal. Unfortunately, circumferential RF ablation tools have not delivered on their promise thus far. The high-density mesh ablator has been largely abandoned owing to high reconnection rates associated with poor clinical efficacy.7 The 10-pole PV ablation catheter (PVAC) was designed from a typical circular mapping catheter shape and is capable of delivering duty-cycled unipolar and bipolar RF energy, thereby potentially creating a contiguous circumferential lesion with minimal repositioning requirement. The initial data appeared quite promising with regard to shorter procedural times and short-term success rates comparable to those of focal irrigated RF ablation.8 However, increased understanding of and vigilance for asymptomatic cerebral emboli (ACE) revealed an alarmingly high incidence of these lesions after PVAC ablation.9 Animal and human studies have now suggested that when poles are in proximity, RF delivery, especially bipolar current, is associated with increased microbubbles and subsequent ACE lesions on magnetic resonance imaging.10,11 This suggests that ACE lesions are associated with overheating of the local blood pool. As the PVAC languishes in the approval process in the United States, one wonders at what point is the simplicity and elegance of the design overwhelmed by the complicating factors of large area ablation? It is in this setting that the nMARQ irrigated circular decapolar mapping and ablation catheter (Biosense Webster Inc, Diamond Bar, CA) makes its entrance. In this issue of HeartRhythm, Shin et al12 describe their experience of using the nMARQ ablation system to perform PV isolation in 25 patients. The conceptual advantage of the nMARQ ablation system over the previous multielectrode ablation systems is the presence of irrigation, which theoretically provides the same benefit that it brought to focal RF ablation: lowering the electrode temperature to reduce charring and allow higher power delivery. The authors report complete acute success in isolating all PVs in this series without the need for a focal catheter. With a reportedly rapid learning curve, procedure and fluoroscopy times were short compared with published data for other ablation systems, although this type of comparison has significant caveats. There were no acute procedure-related complications, and cardiac magnetic resonance imaging performed in all patients 1–2 days after ablation showed no significant PV stenosis—although this was compared with radiographically estimated PV diameter http://dx.doi.org/10.1016/j.hrthm.2013.12.026
Liu
Editorial Commentary
from the intraprocedural left atrial angiogram. Charring on the nMARQ ablation system was noted in 3 procedures; all 3 had delivered bipolar ablation. Follow-up clinical data were available for an average of just over 4 months. Given that this was a feasibility report and not an outcomes study, the nMARQ ablation system has passed an initial test —that of expediency and acute efficacy in PV isolation. However, in our contemporary stage of progress in AF ablation, there are many more essential tests to be taken. With regard to safety, as referenced by the authors, there has already been a reported case of pericardial-esophageal fistula associated with the nMARQ ablation system.13 In addition, irrigation does not prevent charring on overlapping electrodes delivering energy simultaneously, as seen in this series. Another series has reported a high incidence of ACE lesions, similar to previous reports of the PVAC, as well as a high incidence of thermal esophageal lesions.14 With regard to postprocedural efficacy, the durability of PV isolation has become the ultimate test of all PV isolation procedures. In this study, there was no specified waiting period or provocation testing with adenosine or isoproterenol—tools to assess for dormant conduction or possible early recovery of conduction. Fortunately, phrenic nerve palsy has not been reported. As contact force sensing becomes more mature as an adjunctive tool for focal ablation, it is unclear how that technology might be incorporated into a multielectrode platform such as the nMARQ ablation system. Finally, shortand long-term clinical outcomes will be needed. Just like the early stages of focal RF ablation and cryoballoon ablation, there are undoubtedly many lessons to be learned in how to precisely use the nMARQ ablation system to maximize its benefit and minimize its risk. It remains to be seen whether the nMARQ ablation system will go the route of the cryoballoon or the high-intensity focused ultrasound balloon. One thing is clear: Despite the visual simplicity of the final circles of ablation seen on 3dimensional maps, PV isolation will remain a complex procedure, with a myriad of considerations for balancing the extent of permanent myocardial tissue destruction with reduction of complications.
385
References 1. Haissaguerre M, Jais P, Shah DC, et al. Spontaneous initiation of atrial fibrillation by ectopic beats originating in the pulmonary veins. N Engl J Med 1998;339: 659–666. 2. Calkins H, Kuck KH, Cappato R, et al. 2012 HRS/EHRA/ECAS expert consensus statement on catheter and surgical ablation of atrial fibrillation: recommendations for patient selection, procedural techniques, patient management and follow-up, definitions, endpoints, and research trial design: a report of the Heart Rhythm Society (HRS) Task Force on catheter and surgical ablation of atrial fibrillation. Heart Rhythm 2012;9:632–696. 3. Wittkampf FH, Nakagawa H, Foresti S, Aoyama H, Jackman WM. Salineirrigated radiofrequency ablation electrode with external cooling. J Cardiovasc Electrophysiol 2005;16:323–328. 4. Hutchinson MD, Garcia FC, Mandel JE, et al. Efforts to enhance catheter stability improve atrial fibrillation ablation outcome. Heart Rhythm 2013;10: 347–353. 5. Neven K, Metzner A, Schmidt B, Ouyang F, Kuck KH. Two-year clinical followup after pulmonary vein isolation using high-intensity focused ultrasound (HIFU) and an esophageal temperature-guided safety algorithm. Heart Rhythm 2012;9: 407–413. 6. Packer DL, Kowal RC, Wheelan KR, et al. STOP AF Cryoablation Investigators. Cryoballoon ablation of pulmonary veins for paroxysmal atrial fibrillation: first results of the North American Arctic Front (STOP AF) pivotal trial. J Am Coll Cardiol 2013;61:1713–1723. 7. Steinwender C, Honig S, Leisch F, Hofmann R. One-year follow-up after pulmonary vein isolation using a single mesh catheter in patients with paroxysmal atrial fibrillation. Heart Rhythm 2010;7:333–339. 8. Bittner A, Monnig G, Zellerhoff S, et al. Randomized study comparing dutycycled bipolar and unipolar radiofrequency with point-by-point ablation in pulmonary vein isolation. Heart Rhythm 2011;8:1383–1390. 9. Herrera Siklody C, Deneke T, Hocini M, et al. Incidence of asymptomatic intracranial embolic events after pulmonary vein isolation: comparison of different atrial fibrillation ablation technologies in a multicenter study. J Am Coll Cardiol 2011;58:681–688. 10. Haines DE, Stewart MT, Dahlberg S, et al. Microembolism and catheter ablation, I: a comparison of irrigated radiofrequency and multielectrode-phased radiofrequency catheter ablation of pulmonary vein ostia. Circ Arrhythm Electrophysiol 2013;6:16–22. 11. Wieczorek M, Lukat M, Hoeltgen R, et al. Investigation into causes of abnormal cerebral MRI findings following PVAC duty-cycled, phased RF ablation of atrial fibrillation. J Cardiovasc Electrophysiol 2013;24:121–128. 12. Shin D-I, Kirmanoglou K, Eickholt C, et al. Initial results of using a novel irrigated multielectrode mapping and ablation catheter for pulmonary vein isolation. Heart Rhythm 2014;11:375–383. 13. Deneke T, Schade A, Diegeler A, Nentwich K. Esophago-pericardial fistula complicating atrial fibrillation ablation using a novel-irrigated radiofrequency multipolar ablation catheter. J Cardiovasc Electrophysiol 2013;Epub ahead of print 14. Deneke T, Schade A, Müller P, et al. Acute safety and efficacy of a novel multipolar irrigated radiofrequency ablation catheter for pulmonary vein isolation. J Cardiovasc Electrophysiol 2013;Epub ahead of print
