Contact Force−Sensing Catheters: Evolution or Revolution in Catheter Ablation Technology? Edward P. Gerstenfeld Circ Arrhythm Electrophysiol. 2014;7:5-6 doi: 10.1161/CIRCEP.114.001424 Circulation: Arrhythmia and Electrophysiology is published by the American Heart Association, 7272 Greenville Avenue, Dallas, TX 75231 Copyright © 2014 American Heart Association, Inc. All rights reserved. Print ISSN: 1941-3149. Online ISSN: 1941-3084
The online version of this article, along with updated information and services, is located on the World Wide Web at: http://circep.ahajournals.org/content/7/1/5
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Editorial Contact Force–Sensing Catheters Evolution or Revolution in Catheter Ablation Technology? Edward P. Gerstenfeld, MD
R
adiofrequency catheter ablation was initially developed to treat arrhythmias dependent on a narrow isthmus, such as accessory pathway–mediated tachycardias or atrioventricular nodal reentry. Although catheter stability was often discussed as important before delivering radiofrequency energy, adjusting the catheter and delivering another lesion could often rectify an inadequate result. The advent of wide area circumferential or linear ablation for the treatment of atrial fibrillation (AF) and ventricular tachycardia has raised the bar on catheter stability to a new level. To achieve permanent wide area isolation of the pulmonary veins (PV), a series of multiple individual focal lesions must be delivered contiguously and with transmurality. Even a single nontransmural lesion can lead to edema that heals and leads to PV reconnection and recurrent AF. In addition, given the complex left atrial anatomy, atrial and ventricular contraction, respiration, and patient movement, the possibility of PV reconnection after AF ablation is not at all surprising. Consider that the recurrence rate after ablation of atrial flutter, which requires deployment of a short sequence of lesions in a linear fashion connecting 2 well-defined anatomic boundaries, can occur in 10% of patients.1 Extend this to the 10- to 12-cm circumference around the typical PV antrum, and the importance of uniform transmural lesions is apparent.
Article see p 63 It was recognized early that the Achille’s heal to AF ablation was early PV reconnection after ablation.2 Although temperature rises and limited power delivery may have limited lesion depth using early 4-mm-tip catheters, the development of irrigated tip catheters has improved our ability to make large enough lesions to achieve transmurality in the atrium. Yet, PV reconnection continued to occur. I recall as a fellow being told by an attending to “ride the wave,” as I tried to balance the catheter on the left atrial appendage ridge while the patient snored and fidgeted on the table. Clearly, a catheter sliding back and forth over several centimeters was not the ideal situation for delivering reproducible lesions. Use of steerable sheaths, general anesthesia to minimize patient The opinions expressed in this editorial are not necessarily those of the editors or of the American Heart Association. From the Section of Cardiac Electrophysiology, University of California, San Francisco. Correspondence to Edward P. Gerstenfeld, MD, University of California, San Francisco, MU-E 4th floor, 500 Parnassus Ave, San Francisco, CA 94143. E-mail [email protected] (Circ Arrhythm Electrophysiol. 2014;7:5-6.) © 2014 American Heart Association, Inc. Circ Arrhythm Electrophysiol is available at http://circep.ahajournals.org DOI: 10.1161/CIRCEP.114.001424
motion and respiratory motion, and even JET ventilation to remove respiratory excursions completely seemed to enhance the success rate of ablation.3,4 We all use several surrogates of contact force to assure adequacy of lesions during ablation, including catheter stability on fluoroscopy, impedance drop, temperature rise, and electrogram attenuation. Yokoyama et al5 first emphasized the important relationship between catheter/tissue contact force and lesions size in a preclinical study. There was a direct correlation between catheter/ tissue contact force during ablation and the resulting lesion volume in a canine thigh muscle preparation. This important study led to the early adoption of steerable sheaths to maintain better contact force during AF ablation in many centers. The next step in the evolution of catheter ablation was clearly the advent of the contact force–sensing catheter. The initial published results of the first European study using a contact force– sensing catheter6 supported the concept that contact force was the missing link in AF ablation. When mean catheter contact force during ablation was 20 g, the success rate improved dramatically to 80%. In this edition of Circulation: Arrhythmia and Electrophysiology, Ullah et al7 perform a detailed analysis of the relationship between impedance changes, electrogram amplitude, and contact force in 15 patients undergoing catheter ablation of persistent AF; the majority used the Hanson robotic system. An irrigated contact force–sensing catheter (SmartTouch, Biosense Webster, Inc, Diamond Bar, CA) was used with a maximum power delivery of 30 W and irrigation flow rate of 17 mL/min. Contact force was measured using the force time integral (FTI), a measure integrating contact force over time that has become one of the standard measures of contact force applied during catheter ablation. The authors found a strong correlation (Spearman ρ=0.79) between impedance drop during ablation and FTI, with the FTI typically plateauing at 500 g-seconds. Electrogram amplitude reduction correlated poorly with contact force. The authors also found that ablation lesion duration 10 seconds were more consistent and correlated with the FTI. This article has added to the growing body of literature concerning the benefit of contact force measurement during catheter ablation. In contrast to prior reports finding that impedance drop had only a weak correlation with contact force,8,9 the current article found that there was actually a strong correlation between impedance drop and FTI. This is reassuring to many of us who have used impedance drop as a surrogate for lesion creation during catheter ablation. The reason for the differences compared with prior work is not completely clear but
Downloaded from http://circep.ahajournals.org/ at Univ 5 Southern Calif Norris Med Lib on April 7, 2014
6 Circ Arrhythm Electrophysiol February 2014 may be related to the more detailed quantitative analysis and use of nonparametric statistics. The authors also found that the impedance change plateau’s after an FTI of 500 g-seconds, suggesting that further ablation beyond this point does not add significantly to lesion size. This may be useful as a safety and time-saving end point. The limitations of the work are clear—the total patient population is small, and the authors are unable to correlate contact force measurements directly to pathological lesion size in humans. The use of a robotic system to perform the AF ablation is also unusual and may limit the applicability to manual catheter ablation. Finally, only patients with persistent AF were included. The results may differ in patients in whom the atrium is actively contracting during ablation. Nevertheless, the information in the study is corroborative and extends our understanding of how to best use the contact force during AF ablation. Is contact force an evolutionary or revolutionary advance in catheter ablation? I would argue it is revolutionary for several reasons. First, contact force measurements will become the standard at any institution where fellows are trained. One of the reasons we are so attuned to surrogate markers of contact force is that we have all struggled with gauging catheter contact because our fellows progress toward performing independent catheter manipulation. Contact force measurements will be invaluable for giving fellows direct feedback and supervising physicians the ability to judge when effective lesions are being delivered. Second, contact force measurements will be useful to each of us in gauging when our contact force is inadequate. Simply using the contact force catheter for a few cases may allow adoption of techniques to maximize contact force in difficult areas (such as the anterior ridge between the left atrial appendage and PVs). Third, contact force catheters may improve the safety of ablation, allowing us to reduce contact force pressure in certain areas and prevent steam pops or perforations. Fourth, some of the limitations of robotic navigation systems include the inability of the operator to recognize poor or excessive contact force. Incorporation of contact force catheters into these systems may lead to their resurgence. There are still many questions that remain. Once one learns how to optimize contact, will continued use of contact force catheters continue to improve ablation efficacy? Initial studies have shown an impressive improvement in AF ablation outcome when mean contact force can be maintained >20 g and a higher incidence of PV reconnection at sites where lower contact force is applied.10 However, it is possible that anatomic challenges will preclude delivery of increased contact force in certain areas, despite this feedback. A randomized prospective study of blinded versus unblinded use of contact force measurements on outcome after AF ablation, by investigators experienced in the use contact force catheters, would be useful to determine the true use of these catheters. Catheter technologies have advanced tremendously during the past decade, from simple 4-mm-tip radiofrequency catheters to irrigated catheters with multielectrode recordings, shaft visualization, and now contact force measurement. The cost of each catheter continues to increase with each
incremental development. It behooves us to prove that each advance improves patient outcome and safety. In addition, balloon-based technologies allowing more consistent contact and circumferential PV isolation have also arrived. The tradeoff of balloon-based catheters is often a more distal level of PV isolation. Whether the addition of contact force sensing will allow us to achieve the elusive goal of persistent PV isolation with a focal ablation catheter remains to be seen. The analysis from Ullah et al7 has given us the tools to help answer this question.
Disclosures Dr Gerstenfeld receives honoraria from Biosense Webster, Boston Scientific, Medtronic, and St Jude Medical and additionally research grants from Medtronic, Rhythmia Medical, and St Jude Medical.
References 1. Ilg KJ, Kühne M, Crawford T, Chugh A, Jongnarangsin K, Good E, Pelosi F Jr, Bogun F, Morady F, Oral H. Randomized comparison of cavotricuspid isthmus ablation for atrial flutter using an open irrigation-tip versus a large-tip radiofrequency ablation catheter. J Cardiovasc Electrophysiol. 2011;22:1007–1012. 2. Gerstenfeld EP, Callans DJ, Dixit S, Zado E, Marchlinski FE. Incidence and location of focal atrial fibrillation triggers in patients undergoing repeat pulmonary vein isolation: implications for ablation strategies. J Cardiovasc Electrophysiol. 2003;14:685–690. 3. Hutchinson MD, Garcia FC, Mandel JE, Elkassabany N, Zado ES, Riley MP, Cooper JM, Bala R, Frankel DS, Lin D, Supple GE, Dixit S, Gerstenfeld EP, Callans DJ, Marchlinski FE. Efforts to enhance catheter stability improve atrial fibrillation ablation outcome. Heart Rhythm. 2013;10:347–353. 4. Piorkowski C, Eitel C, Rolf S, Bode K, Sommer P, Gaspar T, Kircher S, Wetzel U, Parwani AS, Boldt LH, Mende M, Bollmann A, Husser D, Dagres N, Esato M, Arya A, Haverkamp W, Hindricks G. Steerable versus nonsteerable sheath technology in atrial fibrillation ablation: a prospective, randomized study. Circ Arrhythm Electrophysiol. 2011;4:157–165. 5. Yokoyama K, Nakagawa H, Shah DC, Lambert H, Leo G, Aeby N, Ikeda A, Pitha JV, Sharma T, Lazzara R, Jackman WM. Novel contact force sensor incorporated in irrigated radiofrequency ablation catheter predicts lesion size and incidence of steam pop and thrombus. Circ Arrhythm Electrophysiol. 2008;1:354–362. 6. Reddy VY, Shah D, Kautzner J, Schmidt B, Saoudi N, Herrera C, Jaïs P, Hindricks G, Peichl P, Yulzari A, Lambert H, Neuzil P, Natale A, Kuck KH. The relationship between contact force and clinical outcome during radiofrequency catheter ablation of atrial fibrillation in the TOCCATA study. Heart Rhythm. 2012;9:1789–1795. 7. Ullah, W, Hunter RJ, Baker V, Dhinoja MB, Sporton S, Earley MJ, Schilling RJ. Target indices for clinical ablation in atrial fibrillation: insights from contact force, electrogram, and biophysical parameter analysis. Circ Arrhythm Electrophysiol. 2014;7:63–68. 8. Nakagawa H, Kautzner J, Natale A, Peichl P, Cihak R, Wichterle D, Ikeda A, Santangeli P, Di Biase L, Jackman WM. Locations of high contact force during left atrial mapping in atrial fibrillation patients: electrogram amplitude and impedance are poor predictors of electrode-tissue contact force for ablation of atrial fibrillation. Circ Arrhythm Electrophysiol. 2013;6:746–753. 9. Kumar S, Haqqani HM, Chan M, Lee J, Yudi M, Wong MC, Morton JB, Ling LH, Robinson T, Heck PM, Kelland NF, Halloran K, Spence SJ, Kistler PM, Kalman JM. Predictive value of impedance changes for real-time contact force measurements during catheter ablation of atrial arrhythmias in humans. Heart Rhythm. 2013;10:962–969. 10. Neuzil P, Reddy VY, Kautzner J, Petru J, Wichterle D, Shah D, Lambert H, Yulzari A, Wissner E, Kuck KH. Electrical reconnection after pulmonary vein isolation is contingent on contact force during initial treatment: results from the EFFICAS I study. Circ Arrhythm Electrophysiol. 2013;6:327–333. Key Words: Editorials ◼ atrial fibrillation
Downloaded from http://circep.ahajournals.org/ at Univ Southern Calif Norris Med Lib on April 7, 2014
The online version of this article, along with updated information and services, is located on the World Wide Web at: http://circep.ahajournals.org/content/7/1/5
Permissions: Requests for permissions to reproduce figures, tables, or portions of articles originally published in Circulation: Arrhythmia and Electrophysiology can be obtained via RightsLink, a service of the Copyright Clearance Center, not the Editorial Office. Once the online version of the published article for which permission is being requested is located, click Request Permissions in the middle column of the Web page under Services. Further information about this process is available in the Permissions and Rights Question and Answer document. Reprints: Information about reprints can be found online at: http://www.lww.com/reprints Subscriptions: Information about subscribing to Circulation: Arrhythmia and Electrophysiology is online at: http://circep.ahajournals.org//subscriptions/
Downloaded from http://circep.ahajournals.org/ at Univ Southern Calif Norris Med Lib on April 7, 2014
Editorial Contact Force–Sensing Catheters Evolution or Revolution in Catheter Ablation Technology? Edward P. Gerstenfeld, MD
R
adiofrequency catheter ablation was initially developed to treat arrhythmias dependent on a narrow isthmus, such as accessory pathway–mediated tachycardias or atrioventricular nodal reentry. Although catheter stability was often discussed as important before delivering radiofrequency energy, adjusting the catheter and delivering another lesion could often rectify an inadequate result. The advent of wide area circumferential or linear ablation for the treatment of atrial fibrillation (AF) and ventricular tachycardia has raised the bar on catheter stability to a new level. To achieve permanent wide area isolation of the pulmonary veins (PV), a series of multiple individual focal lesions must be delivered contiguously and with transmurality. Even a single nontransmural lesion can lead to edema that heals and leads to PV reconnection and recurrent AF. In addition, given the complex left atrial anatomy, atrial and ventricular contraction, respiration, and patient movement, the possibility of PV reconnection after AF ablation is not at all surprising. Consider that the recurrence rate after ablation of atrial flutter, which requires deployment of a short sequence of lesions in a linear fashion connecting 2 well-defined anatomic boundaries, can occur in 10% of patients.1 Extend this to the 10- to 12-cm circumference around the typical PV antrum, and the importance of uniform transmural lesions is apparent.
Article see p 63 It was recognized early that the Achille’s heal to AF ablation was early PV reconnection after ablation.2 Although temperature rises and limited power delivery may have limited lesion depth using early 4-mm-tip catheters, the development of irrigated tip catheters has improved our ability to make large enough lesions to achieve transmurality in the atrium. Yet, PV reconnection continued to occur. I recall as a fellow being told by an attending to “ride the wave,” as I tried to balance the catheter on the left atrial appendage ridge while the patient snored and fidgeted on the table. Clearly, a catheter sliding back and forth over several centimeters was not the ideal situation for delivering reproducible lesions. Use of steerable sheaths, general anesthesia to minimize patient The opinions expressed in this editorial are not necessarily those of the editors or of the American Heart Association. From the Section of Cardiac Electrophysiology, University of California, San Francisco. Correspondence to Edward P. Gerstenfeld, MD, University of California, San Francisco, MU-E 4th floor, 500 Parnassus Ave, San Francisco, CA 94143. E-mail [email protected] (Circ Arrhythm Electrophysiol. 2014;7:5-6.) © 2014 American Heart Association, Inc. Circ Arrhythm Electrophysiol is available at http://circep.ahajournals.org DOI: 10.1161/CIRCEP.114.001424
motion and respiratory motion, and even JET ventilation to remove respiratory excursions completely seemed to enhance the success rate of ablation.3,4 We all use several surrogates of contact force to assure adequacy of lesions during ablation, including catheter stability on fluoroscopy, impedance drop, temperature rise, and electrogram attenuation. Yokoyama et al5 first emphasized the important relationship between catheter/tissue contact force and lesions size in a preclinical study. There was a direct correlation between catheter/ tissue contact force during ablation and the resulting lesion volume in a canine thigh muscle preparation. This important study led to the early adoption of steerable sheaths to maintain better contact force during AF ablation in many centers. The next step in the evolution of catheter ablation was clearly the advent of the contact force–sensing catheter. The initial published results of the first European study using a contact force– sensing catheter6 supported the concept that contact force was the missing link in AF ablation. When mean catheter contact force during ablation was 20 g, the success rate improved dramatically to 80%. In this edition of Circulation: Arrhythmia and Electrophysiology, Ullah et al7 perform a detailed analysis of the relationship between impedance changes, electrogram amplitude, and contact force in 15 patients undergoing catheter ablation of persistent AF; the majority used the Hanson robotic system. An irrigated contact force–sensing catheter (SmartTouch, Biosense Webster, Inc, Diamond Bar, CA) was used with a maximum power delivery of 30 W and irrigation flow rate of 17 mL/min. Contact force was measured using the force time integral (FTI), a measure integrating contact force over time that has become one of the standard measures of contact force applied during catheter ablation. The authors found a strong correlation (Spearman ρ=0.79) between impedance drop during ablation and FTI, with the FTI typically plateauing at 500 g-seconds. Electrogram amplitude reduction correlated poorly with contact force. The authors also found that ablation lesion duration 10 seconds were more consistent and correlated with the FTI. This article has added to the growing body of literature concerning the benefit of contact force measurement during catheter ablation. In contrast to prior reports finding that impedance drop had only a weak correlation with contact force,8,9 the current article found that there was actually a strong correlation between impedance drop and FTI. This is reassuring to many of us who have used impedance drop as a surrogate for lesion creation during catheter ablation. The reason for the differences compared with prior work is not completely clear but
Downloaded from http://circep.ahajournals.org/ at Univ 5 Southern Calif Norris Med Lib on April 7, 2014
6 Circ Arrhythm Electrophysiol February 2014 may be related to the more detailed quantitative analysis and use of nonparametric statistics. The authors also found that the impedance change plateau’s after an FTI of 500 g-seconds, suggesting that further ablation beyond this point does not add significantly to lesion size. This may be useful as a safety and time-saving end point. The limitations of the work are clear—the total patient population is small, and the authors are unable to correlate contact force measurements directly to pathological lesion size in humans. The use of a robotic system to perform the AF ablation is also unusual and may limit the applicability to manual catheter ablation. Finally, only patients with persistent AF were included. The results may differ in patients in whom the atrium is actively contracting during ablation. Nevertheless, the information in the study is corroborative and extends our understanding of how to best use the contact force during AF ablation. Is contact force an evolutionary or revolutionary advance in catheter ablation? I would argue it is revolutionary for several reasons. First, contact force measurements will become the standard at any institution where fellows are trained. One of the reasons we are so attuned to surrogate markers of contact force is that we have all struggled with gauging catheter contact because our fellows progress toward performing independent catheter manipulation. Contact force measurements will be invaluable for giving fellows direct feedback and supervising physicians the ability to judge when effective lesions are being delivered. Second, contact force measurements will be useful to each of us in gauging when our contact force is inadequate. Simply using the contact force catheter for a few cases may allow adoption of techniques to maximize contact force in difficult areas (such as the anterior ridge between the left atrial appendage and PVs). Third, contact force catheters may improve the safety of ablation, allowing us to reduce contact force pressure in certain areas and prevent steam pops or perforations. Fourth, some of the limitations of robotic navigation systems include the inability of the operator to recognize poor or excessive contact force. Incorporation of contact force catheters into these systems may lead to their resurgence. There are still many questions that remain. Once one learns how to optimize contact, will continued use of contact force catheters continue to improve ablation efficacy? Initial studies have shown an impressive improvement in AF ablation outcome when mean contact force can be maintained >20 g and a higher incidence of PV reconnection at sites where lower contact force is applied.10 However, it is possible that anatomic challenges will preclude delivery of increased contact force in certain areas, despite this feedback. A randomized prospective study of blinded versus unblinded use of contact force measurements on outcome after AF ablation, by investigators experienced in the use contact force catheters, would be useful to determine the true use of these catheters. Catheter technologies have advanced tremendously during the past decade, from simple 4-mm-tip radiofrequency catheters to irrigated catheters with multielectrode recordings, shaft visualization, and now contact force measurement. The cost of each catheter continues to increase with each
incremental development. It behooves us to prove that each advance improves patient outcome and safety. In addition, balloon-based technologies allowing more consistent contact and circumferential PV isolation have also arrived. The tradeoff of balloon-based catheters is often a more distal level of PV isolation. Whether the addition of contact force sensing will allow us to achieve the elusive goal of persistent PV isolation with a focal ablation catheter remains to be seen. The analysis from Ullah et al7 has given us the tools to help answer this question.
Disclosures Dr Gerstenfeld receives honoraria from Biosense Webster, Boston Scientific, Medtronic, and St Jude Medical and additionally research grants from Medtronic, Rhythmia Medical, and St Jude Medical.
References 1. Ilg KJ, Kühne M, Crawford T, Chugh A, Jongnarangsin K, Good E, Pelosi F Jr, Bogun F, Morady F, Oral H. Randomized comparison of cavotricuspid isthmus ablation for atrial flutter using an open irrigation-tip versus a large-tip radiofrequency ablation catheter. J Cardiovasc Electrophysiol. 2011;22:1007–1012. 2. Gerstenfeld EP, Callans DJ, Dixit S, Zado E, Marchlinski FE. Incidence and location of focal atrial fibrillation triggers in patients undergoing repeat pulmonary vein isolation: implications for ablation strategies. J Cardiovasc Electrophysiol. 2003;14:685–690. 3. Hutchinson MD, Garcia FC, Mandel JE, Elkassabany N, Zado ES, Riley MP, Cooper JM, Bala R, Frankel DS, Lin D, Supple GE, Dixit S, Gerstenfeld EP, Callans DJ, Marchlinski FE. Efforts to enhance catheter stability improve atrial fibrillation ablation outcome. Heart Rhythm. 2013;10:347–353. 4. Piorkowski C, Eitel C, Rolf S, Bode K, Sommer P, Gaspar T, Kircher S, Wetzel U, Parwani AS, Boldt LH, Mende M, Bollmann A, Husser D, Dagres N, Esato M, Arya A, Haverkamp W, Hindricks G. Steerable versus nonsteerable sheath technology in atrial fibrillation ablation: a prospective, randomized study. Circ Arrhythm Electrophysiol. 2011;4:157–165. 5. Yokoyama K, Nakagawa H, Shah DC, Lambert H, Leo G, Aeby N, Ikeda A, Pitha JV, Sharma T, Lazzara R, Jackman WM. Novel contact force sensor incorporated in irrigated radiofrequency ablation catheter predicts lesion size and incidence of steam pop and thrombus. Circ Arrhythm Electrophysiol. 2008;1:354–362. 6. Reddy VY, Shah D, Kautzner J, Schmidt B, Saoudi N, Herrera C, Jaïs P, Hindricks G, Peichl P, Yulzari A, Lambert H, Neuzil P, Natale A, Kuck KH. The relationship between contact force and clinical outcome during radiofrequency catheter ablation of atrial fibrillation in the TOCCATA study. Heart Rhythm. 2012;9:1789–1795. 7. Ullah, W, Hunter RJ, Baker V, Dhinoja MB, Sporton S, Earley MJ, Schilling RJ. Target indices for clinical ablation in atrial fibrillation: insights from contact force, electrogram, and biophysical parameter analysis. Circ Arrhythm Electrophysiol. 2014;7:63–68. 8. Nakagawa H, Kautzner J, Natale A, Peichl P, Cihak R, Wichterle D, Ikeda A, Santangeli P, Di Biase L, Jackman WM. Locations of high contact force during left atrial mapping in atrial fibrillation patients: electrogram amplitude and impedance are poor predictors of electrode-tissue contact force for ablation of atrial fibrillation. Circ Arrhythm Electrophysiol. 2013;6:746–753. 9. Kumar S, Haqqani HM, Chan M, Lee J, Yudi M, Wong MC, Morton JB, Ling LH, Robinson T, Heck PM, Kelland NF, Halloran K, Spence SJ, Kistler PM, Kalman JM. Predictive value of impedance changes for real-time contact force measurements during catheter ablation of atrial arrhythmias in humans. Heart Rhythm. 2013;10:962–969. 10. Neuzil P, Reddy VY, Kautzner J, Petru J, Wichterle D, Shah D, Lambert H, Yulzari A, Wissner E, Kuck KH. Electrical reconnection after pulmonary vein isolation is contingent on contact force during initial treatment: results from the EFFICAS I study. Circ Arrhythm Electrophysiol. 2013;6:327–333. Key Words: Editorials ◼ atrial fibrillation
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