Contact-Force Recovery Can Predict Cardiac Perforation during Radiofrequency Ablation ALIREZA NAZERI, M.D.,* ANAND GANAPATHY, B.S.,† ALI MASSUMI, M.D.,* MEHRAN MASSUMI, M.D.,* GARTH CONSTANTINE, M.S.,‡ SHAUL RAZ, PH.D.,‡ and MEHDI RAZAVI, M.D.*,† From the *Department of Cardiology, Texas Heart Institute, Houston, Texas; †Department of Internal Medicine, Section of Cardiology, Baylor College of Medicine, Houston, Texas; and ‡Biosense Webster, Inc, Diamond Bar, California
Background: During radiofrequency ablation (RFA), the ability to know whether a steam pop has led to cardiac perforation (CP) would be of profound clinical significance. We aimed to determine whether catheter contact-force characteristics can predict whether a steam pop during RFA causes CP. R SmarttouchTM force-sensing catheter (Biosense Webster Inc., Methods: We used a 7.5F Thermocool Diamond Bar, CA, USA) to perform open-chest left atrial RFA under direct visualization in four sheep. We measured the contact force and its direction every 50 ms during RFA. At each steam pop, we noted whether CP occurred. We then analyzed the contact-force signals to determine whether specific features predicted the presence (+) or absence (−) of CP. Results: A total of 24 steam pops occurred; 10 were CP+ and 14 were CP−. At the time of CP+ and CP− events, the contact force was 50 ± 25 and 40 ± 15 g, respectively (P = 0.146). All steam-pop events were associated with a rapid drop-off in contact force, but 10 of the 14 CP– events showed an immediate contact-force rebound, whereas none of the CP+ events did. This rebound presumably occurred as the catheter tip resumed contact with the left atrial wall. The average contact-force rebound equaled 80–100% of the contact-force drop-off. Conclusions: The ability to measure catheter contact force during RFA is a valuable asset, as contactforce recovery may be used to predict CP. Further studies are warranted to validate our findings in the clinical setting. (PACE 2014; 37:1129–1132) radiofrequency ablation, cardiac perforation, contact-force recovery, steam pops
Introduction Steam pops are audible pops that frequently occur during irrigated radiofrequency ablation (RFA) and can cause cardiac perforation (CP).1 In turn, CP can lead to cardiac tamponade, which is well correlated with the incidence of steam pops. Currently, no method is available that can immediately detect the occurrence of perforation. This situation may change, however, with the use of contact-force sensing, a new technology that measures the force of the catheter tip against the The abstract for this paper has been accepted for presentation at the meeting of the European Society of Cardiology 2013. Financial Support: This study is funded by Biosense Webster, Inc., Diamond Bar, California. Disclosures: G. Constantine and S. Raz are employees of Biosense Webster Inc. Address for reprints: Mehdi Razavi, M.D., Department of Cardiology, Texas Heart Institute, 6624 Fannin Street, Suite 2480, Houston, TX 77030. Fax: 713-791-1786; e-mail: [email protected] Received August 12, 2013; revised February 20, 2014; accepted March 18, 2014. doi: 10.1111/pace.12409
chamber wall. The incidence of steam pops has been shown to increase as the contact force rises, independent of radiofrequency.2 Thus far, investigators of steam-pop events have found no specific characteristic differences in contact-force values that can determine whether or not CP has occurred. The purpose of the present study was to assess whether steam pops with or without CP have specific distinct characteristics on contact-force tracings. To accomplish this goal, we used a catheter developed to measure contact force by assessing the degree of spring bending of the catheter tip. Methods The experiments were performed on four male Suffolk cross sheep with an average weight of 73 kg. The study was approved by our institutional Committee on Animal Use and Care and conformed to the Guide for the Care and Use of Laboratory Animals. For steam-pop induction, we used a 7.5F R force-sensing ablation catheter Thermocool TM Smarttouch (Biosense Webster Inc., Diamond Bar, CA, USA). The catheter features a 3.5-mm
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Table I. Summary of Results Steam Pops
Figure 1. Experimental set up. Contact force sensing ablation catheter shown pressed against the left atrial wall. Increasing radiofrequency force was applied until a steam pop was visualized and then determination of cardiac perforation was performed.
electrode with a 6-hole irrigated tip, which is connected to a spring attached to the catheter shaft. A magnetic transmitter is incorporated into the electrode. The transmitter, along with three location sensors located on the shaft, determines the degree of spring bending. The result can then be used to determine the contact force that the catheter tip is exerting against the cardiac wall, as well as the direction of the force. We used a sampling rate of 50 ms to measure spring bending R by the system. We used the CARTO 3 system (Biosense Webster Inc.) in conjunction with the Smarttouch catheter to graphically present contact-force information along with 3D mapping and navigation characteristics. Under general anesthesia, each sheep underwent a left lateral thoracotomy to allow direct visualization of the heart. After opening the thoracic cavity, we made an incision in the left atrium and lined the incision with a purse-string suture. We then placed the ablation catheter directly into the chamber and secured the device by tightening the suture. To induce steam pops in the cardiac walls, we applied increasing radiofrequency force with the catheter (Fig. 1). After each steam pop, the presence of CP was monitored. Perforation was considered to have occurred if it was directly observable through the thoracic-cavity access site. At the end of the study, the animals were humanely euthanized. We then performed offline data analysis of the contact-force values to determine whether any specific features of the signal could be utilized to differentiate between the presence (+) or absence (−) of CP. The data were analyzed by using the standard statistical methods.
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CP+
CP−
P Value
Number (n) of 10 14 — events Contact force 50 ± 19.36 39.23 ± 14.12 0.146 (t-test) at time of event (g) Force recovery 0 10 — Average force — 80–100% — recovery (% of max contact force) CP+ = cardiac perforation present; CP− = cardiac perforation absent; max = maximum.
Results A total of 24 steam pops occurred during the course of the study. Forty-five total lesions were delivered. Nine steam pops occurred in the lateral left atrial (LA) free wall, five in the appendage, five in the posterior wall, and five in the anterior wall. All ablations were performed at a target of 40 W with 30 cc/min saline flush. Average duration prior to perforation was 32 ± 5.7 seconds and an average temperature of 35 ± 2.3°C. Mean contact force was 43.8 ± 17.3 g. Ten steam pops were CP positive (CP+), indicating the presence of CP, and 14 steam pops were CP negative (CP−), indicating that no perforation had occurred. Table I summarizes the results of the study. After each steam pop, there was a rapid decrease in the contact force. However, rapid recovery of the contact force was seen in 10 of the 14 CP− events. On the other hand, the CP+ events did not have an associated recovery of the contact force after the steam-pop event. For the CP− events associated with contact-force recovery, the average rebound force equaled 80% to 100% of the original contact force. Two data points (one CP+ and one CP−) were excluded, as the contact force could not be obtained even though a steam-pop event occurred. Figure 2 shows the average contact force seen after steam-pop events with CP+ versus CP− outcomes. Higher contact-force values were seen in the CP+ events, but the differences were not significant, due in part to the small sample size. Contact-force recovery was seen in 10 of the 14 CP− events but was not seen in any of the CP+ events. Figure 3 shows examples of the contactforce data obtained for the CP+ versus CP− events.
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CONTACT-FORCE RECOVERY PREDICTS CARDIAC PERFORATION
Figure 2. Average contact force seen after steam-pop events with (+) and without (−) cardiac perforation.
Figure 3. Examples of contact-force differences after steam-pops with cardiac perforation (CP) versus no CP. The steam-pop event occurs at time t = 0 and extends 2 seconds before and 4 seconds after that time. The red line (positive) indicates that CP has occurred; the contact force undergoes a steep drop with no real recovery. In contrast, the blue line (negative) indicates that no CP has occurred; the signal undergoes only minimal decay after the steam-pop event, and the contact force then recovers to its presteam-pop position.
Discussion RFA is commonly performed to treat cardiac arrhythmias, particularly atrial fibrillation.3–6 The current trend shows that an increased number of catheter ablation procedures are performed each year in all cardiac-arrhythmia patients, including older ones.7 Perioperative RFA-related complications are seen in 1.4–6% of patients treated for atrial fibrillation.8–11 CP is a serious risk that can result in pericardial effusion and/or tamponade and is seen in 2.4% of left atrial RFA procedures.9,12
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In a worldwide survey of RFA procedures for atrial fibrillation, CP was the leading cause of death.10 Furthermore, approximately 60% of all CPs that occur in these procedures require immediate pericardial drainage.12 Frequently, there is a delay between the onset of perforation and the clinically significant pericardial effusion causing tamponade. Because the operator is usually unaware of a perforation until hemodynamic compromise occurs, it is often too late to implement corrective measures intended to lessen the impact of perforation and prevent tamponade. Thus, a method that could alert operators when perforation has occurred—or is likely to occur—would have great clinical value. Contact-force sensing irrigated ablation catheters have been shown to be safe and effective for treating patients with cardiac arrhythmias.13 Because steam pops play a role in inducing CP, evaluation of steam pops through the analysis of contact force can provide a method for predicting CP. In previous studies, investigators have evaluated the use of contact force as a means to determine which, if any, characteristics of steam pops could be used to predict whether CP has occurred. Using an irrigated RFA catheter with optical fibers that measured deformation of the catheter tip, Yokoyama et al.2 showed that the incidence of steam pops increased with rising contact force, even independent of radiofrequency, in canine skeletal-muscle models. Perna et al.14 were the first to assess contact force in the beating swine heart for the purpose of analyzing the average contact forces necessary to induce CP. Until now, no one has found any contact-force characteristics that might be utilized to predict the occurrence of CP. Our study showed that contact-force recovery may be a marker that can predict this occurrence. Our data suggest a potential role for contact-force catheters and contact-force recovery phenomena to predict perforation. We believe that contact force recovery is a manifestation of the catheter tip’s immediate rebound against the LA wall after steam pop. Thus the initial release of force after SP will be followed by recovery of contact force. We cannot be certain why contact force recovery did not occur in four lesions. We speculate that in these instances the catheter tip failed to immediately make contact with the left atrial wall after onset of the steam pop. This may have occurred if the force of the pop displaced the catheter tip inward, towards the LA cavity. Whereas our results are not statistically significant, this topic warrants further study, as the ability to rapidly detect CP would potentially decrease the risk of catheter ablation.
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Conclusion We have demonstrated that during RFA, a rapid rebound in the contact force after the initial steam pop-induced drop-off appears to be a feature specific to a steam pop that does not lead to CP. The absolute contact-force value at the time of
the steam pop does not predict whether or not CP is present. The catheter’s ability to measure contact force during RFA is valuable, as contactforce recovery may be used to predict CP. Further studies are warranted to validate our findings in the clinical setting.
References 1. Seiler J, Roberts-Thomson KC, Raymond JM, Vest J, Delacretaz E, Stevenson WG. Steam pops during irrigated radiofrequency ablation: Feasibility of impedance monitoring for prevention. Heart Rhythm 2008; 5:1411–1416. 2. Yokoyama K, Nakagawa H, Shah DC, Lambert H, Leo G, Aeby N, Ikeda A, et al. 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. 3. Oral H, Pappone C, Chugh A, Good E, Bogun F, Pelosi F, Jr., Bates ER, et al. Circumferential pulmonary-vein ablation for chronic atrial fibrillation. N Engl J Med 2006; 354:934–941. 4. Khan MN, Jais P, Cummings J, Di Biase L, Sanders P, Martin DO, Kautzner J, et al. Pulmonary-vein isolation for atrial fibrillation in patients with heart failure. N Engl J Med 2008; 359:1778– 1785. 5. Wazni OM, Marrouche NF, Martin DO, Verma A, Bhargava M, Saliba W, Bash D, et al. Radiofrequency ablation vs antiarrhythmic drugs as first-line treatment of symptomatic atrial fibrillation: A randomized trial. J Am Med Assoc 2005; 293:2634–2640. 6. European Heart Rhythm Association, European Cardiac Arrhythmia Society, American College of Cardiology, American Heart Association, Society of Thoracic Surgeons, Calkins H, Brugada J, et al. HRS/EHRA/ECAS expert consensus statement on catheter and surgical ablation of atrial fibrillation: Recommendations for personnel, policy, procedures and follow-up. A report of the Heart Rhythm Society (HRS) Task Force on Catheter and Surgical Ablation of Atrial Fibrillation. Heart Rhythm 2007; 4:816–861.
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7. Kneeland PP, Fang MC. Trends in catheter ablation for atrial fibrillation in the United States. J Hosp Med 2009; 4:E1–E5. 8. Bertaglia E, Zoppo F, Tondo C, Colella A, Mantovan R, Senatore G, Bottoni N, et al. Early complications of pulmonary vein catheter ablation for atrial fibrillation: A multicenter prospective registry on procedural safety. Heart Rhythm 2007; 4:1265–1271. 9. Cappato R, Calkins H, Chen SA, Davies W, Iesaka Y, Kalman J, Kim YH, et al. Prevalence and causes of fatal outcome in catheter ablation of atrial fibrillation. J Am Coll Cardiol 2009; 53:1798–1803. 10. Cappato R, Calkins H, Chen SA, Davies W, Iesaka Y, Kalman J, Kim YH, et al. Worldwide survey on the methods, efficacy, and safety of catheter ablation for human atrial fibrillation. Circulation 2005; 111:1100–1105. 11. Piccini JP, Lopes RD, Kong MH, Hasselblad V, Jackson K, Al-Khatib SM. Pulmonary vein isolation for the maintenance of sinus rhythm in patients with atrial fibrillation: A meta-analysis of randomized, controlled trials. Circ Arrhythm Electrophysiol 2009; 2:626–633. 12. Bunch TJ, Asirvatham SJ, Friedman PA, Monahan KH, Munger TM, Rea RF, Sinak LJ, et al. Outcomes after cardiac perforation during radiofrequency ablation of the atrium. J Cardiovasc Electrophysiol 2005; 16:1172–1179. 13. Kuck KH, Reddy VY, Schmidt B, Natale A, Neuzil P, Saoudi N, Kautzner J, et al. A novel radiofrequency ablation catheter using contact force sensing: Toccata study. Heart Rhythm 2012; 9:18–23. 14. Perna F, Heist EK, Danik SB, Barrett CD, Ruskin JN, Mansour M. Assessment of catheter tip contact force resulting in cardiac perforation in swine atria using force sensing technology. Circ Arrhythm Electrophysiol 2011; 4:218–224.
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Background: During radiofrequency ablation (RFA), the ability to know whether a steam pop has led to cardiac perforation (CP) would be of profound clinical significance. We aimed to determine whether catheter contact-force characteristics can predict whether a steam pop during RFA causes CP. R SmarttouchTM force-sensing catheter (Biosense Webster Inc., Methods: We used a 7.5F Thermocool Diamond Bar, CA, USA) to perform open-chest left atrial RFA under direct visualization in four sheep. We measured the contact force and its direction every 50 ms during RFA. At each steam pop, we noted whether CP occurred. We then analyzed the contact-force signals to determine whether specific features predicted the presence (+) or absence (−) of CP. Results: A total of 24 steam pops occurred; 10 were CP+ and 14 were CP−. At the time of CP+ and CP− events, the contact force was 50 ± 25 and 40 ± 15 g, respectively (P = 0.146). All steam-pop events were associated with a rapid drop-off in contact force, but 10 of the 14 CP– events showed an immediate contact-force rebound, whereas none of the CP+ events did. This rebound presumably occurred as the catheter tip resumed contact with the left atrial wall. The average contact-force rebound equaled 80–100% of the contact-force drop-off. Conclusions: The ability to measure catheter contact force during RFA is a valuable asset, as contactforce recovery may be used to predict CP. Further studies are warranted to validate our findings in the clinical setting. (PACE 2014; 37:1129–1132) radiofrequency ablation, cardiac perforation, contact-force recovery, steam pops
Introduction Steam pops are audible pops that frequently occur during irrigated radiofrequency ablation (RFA) and can cause cardiac perforation (CP).1 In turn, CP can lead to cardiac tamponade, which is well correlated with the incidence of steam pops. Currently, no method is available that can immediately detect the occurrence of perforation. This situation may change, however, with the use of contact-force sensing, a new technology that measures the force of the catheter tip against the The abstract for this paper has been accepted for presentation at the meeting of the European Society of Cardiology 2013. Financial Support: This study is funded by Biosense Webster, Inc., Diamond Bar, California. Disclosures: G. Constantine and S. Raz are employees of Biosense Webster Inc. Address for reprints: Mehdi Razavi, M.D., Department of Cardiology, Texas Heart Institute, 6624 Fannin Street, Suite 2480, Houston, TX 77030. Fax: 713-791-1786; e-mail: [email protected] Received August 12, 2013; revised February 20, 2014; accepted March 18, 2014. doi: 10.1111/pace.12409
chamber wall. The incidence of steam pops has been shown to increase as the contact force rises, independent of radiofrequency.2 Thus far, investigators of steam-pop events have found no specific characteristic differences in contact-force values that can determine whether or not CP has occurred. The purpose of the present study was to assess whether steam pops with or without CP have specific distinct characteristics on contact-force tracings. To accomplish this goal, we used a catheter developed to measure contact force by assessing the degree of spring bending of the catheter tip. Methods The experiments were performed on four male Suffolk cross sheep with an average weight of 73 kg. The study was approved by our institutional Committee on Animal Use and Care and conformed to the Guide for the Care and Use of Laboratory Animals. For steam-pop induction, we used a 7.5F R force-sensing ablation catheter Thermocool TM Smarttouch (Biosense Webster Inc., Diamond Bar, CA, USA). The catheter features a 3.5-mm
©2014 Wiley Periodicals, Inc. PACE, Vol. 37
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Table I. Summary of Results Steam Pops
Figure 1. Experimental set up. Contact force sensing ablation catheter shown pressed against the left atrial wall. Increasing radiofrequency force was applied until a steam pop was visualized and then determination of cardiac perforation was performed.
electrode with a 6-hole irrigated tip, which is connected to a spring attached to the catheter shaft. A magnetic transmitter is incorporated into the electrode. The transmitter, along with three location sensors located on the shaft, determines the degree of spring bending. The result can then be used to determine the contact force that the catheter tip is exerting against the cardiac wall, as well as the direction of the force. We used a sampling rate of 50 ms to measure spring bending R by the system. We used the CARTO 3 system (Biosense Webster Inc.) in conjunction with the Smarttouch catheter to graphically present contact-force information along with 3D mapping and navigation characteristics. Under general anesthesia, each sheep underwent a left lateral thoracotomy to allow direct visualization of the heart. After opening the thoracic cavity, we made an incision in the left atrium and lined the incision with a purse-string suture. We then placed the ablation catheter directly into the chamber and secured the device by tightening the suture. To induce steam pops in the cardiac walls, we applied increasing radiofrequency force with the catheter (Fig. 1). After each steam pop, the presence of CP was monitored. Perforation was considered to have occurred if it was directly observable through the thoracic-cavity access site. At the end of the study, the animals were humanely euthanized. We then performed offline data analysis of the contact-force values to determine whether any specific features of the signal could be utilized to differentiate between the presence (+) or absence (−) of CP. The data were analyzed by using the standard statistical methods.
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CP+
CP−
P Value
Number (n) of 10 14 — events Contact force 50 ± 19.36 39.23 ± 14.12 0.146 (t-test) at time of event (g) Force recovery 0 10 — Average force — 80–100% — recovery (% of max contact force) CP+ = cardiac perforation present; CP− = cardiac perforation absent; max = maximum.
Results A total of 24 steam pops occurred during the course of the study. Forty-five total lesions were delivered. Nine steam pops occurred in the lateral left atrial (LA) free wall, five in the appendage, five in the posterior wall, and five in the anterior wall. All ablations were performed at a target of 40 W with 30 cc/min saline flush. Average duration prior to perforation was 32 ± 5.7 seconds and an average temperature of 35 ± 2.3°C. Mean contact force was 43.8 ± 17.3 g. Ten steam pops were CP positive (CP+), indicating the presence of CP, and 14 steam pops were CP negative (CP−), indicating that no perforation had occurred. Table I summarizes the results of the study. After each steam pop, there was a rapid decrease in the contact force. However, rapid recovery of the contact force was seen in 10 of the 14 CP− events. On the other hand, the CP+ events did not have an associated recovery of the contact force after the steam-pop event. For the CP− events associated with contact-force recovery, the average rebound force equaled 80% to 100% of the original contact force. Two data points (one CP+ and one CP−) were excluded, as the contact force could not be obtained even though a steam-pop event occurred. Figure 2 shows the average contact force seen after steam-pop events with CP+ versus CP− outcomes. Higher contact-force values were seen in the CP+ events, but the differences were not significant, due in part to the small sample size. Contact-force recovery was seen in 10 of the 14 CP− events but was not seen in any of the CP+ events. Figure 3 shows examples of the contactforce data obtained for the CP+ versus CP− events.
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CONTACT-FORCE RECOVERY PREDICTS CARDIAC PERFORATION
Figure 2. Average contact force seen after steam-pop events with (+) and without (−) cardiac perforation.
Figure 3. Examples of contact-force differences after steam-pops with cardiac perforation (CP) versus no CP. The steam-pop event occurs at time t = 0 and extends 2 seconds before and 4 seconds after that time. The red line (positive) indicates that CP has occurred; the contact force undergoes a steep drop with no real recovery. In contrast, the blue line (negative) indicates that no CP has occurred; the signal undergoes only minimal decay after the steam-pop event, and the contact force then recovers to its presteam-pop position.
Discussion RFA is commonly performed to treat cardiac arrhythmias, particularly atrial fibrillation.3–6 The current trend shows that an increased number of catheter ablation procedures are performed each year in all cardiac-arrhythmia patients, including older ones.7 Perioperative RFA-related complications are seen in 1.4–6% of patients treated for atrial fibrillation.8–11 CP is a serious risk that can result in pericardial effusion and/or tamponade and is seen in 2.4% of left atrial RFA procedures.9,12
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In a worldwide survey of RFA procedures for atrial fibrillation, CP was the leading cause of death.10 Furthermore, approximately 60% of all CPs that occur in these procedures require immediate pericardial drainage.12 Frequently, there is a delay between the onset of perforation and the clinically significant pericardial effusion causing tamponade. Because the operator is usually unaware of a perforation until hemodynamic compromise occurs, it is often too late to implement corrective measures intended to lessen the impact of perforation and prevent tamponade. Thus, a method that could alert operators when perforation has occurred—or is likely to occur—would have great clinical value. Contact-force sensing irrigated ablation catheters have been shown to be safe and effective for treating patients with cardiac arrhythmias.13 Because steam pops play a role in inducing CP, evaluation of steam pops through the analysis of contact force can provide a method for predicting CP. In previous studies, investigators have evaluated the use of contact force as a means to determine which, if any, characteristics of steam pops could be used to predict whether CP has occurred. Using an irrigated RFA catheter with optical fibers that measured deformation of the catheter tip, Yokoyama et al.2 showed that the incidence of steam pops increased with rising contact force, even independent of radiofrequency, in canine skeletal-muscle models. Perna et al.14 were the first to assess contact force in the beating swine heart for the purpose of analyzing the average contact forces necessary to induce CP. Until now, no one has found any contact-force characteristics that might be utilized to predict the occurrence of CP. Our study showed that contact-force recovery may be a marker that can predict this occurrence. Our data suggest a potential role for contact-force catheters and contact-force recovery phenomena to predict perforation. We believe that contact force recovery is a manifestation of the catheter tip’s immediate rebound against the LA wall after steam pop. Thus the initial release of force after SP will be followed by recovery of contact force. We cannot be certain why contact force recovery did not occur in four lesions. We speculate that in these instances the catheter tip failed to immediately make contact with the left atrial wall after onset of the steam pop. This may have occurred if the force of the pop displaced the catheter tip inward, towards the LA cavity. Whereas our results are not statistically significant, this topic warrants further study, as the ability to rapidly detect CP would potentially decrease the risk of catheter ablation.
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Conclusion We have demonstrated that during RFA, a rapid rebound in the contact force after the initial steam pop-induced drop-off appears to be a feature specific to a steam pop that does not lead to CP. The absolute contact-force value at the time of
the steam pop does not predict whether or not CP is present. The catheter’s ability to measure contact force during RFA is valuable, as contactforce recovery may be used to predict CP. Further studies are warranted to validate our findings in the clinical setting.
References 1. Seiler J, Roberts-Thomson KC, Raymond JM, Vest J, Delacretaz E, Stevenson WG. Steam pops during irrigated radiofrequency ablation: Feasibility of impedance monitoring for prevention. Heart Rhythm 2008; 5:1411–1416. 2. Yokoyama K, Nakagawa H, Shah DC, Lambert H, Leo G, Aeby N, Ikeda A, et al. 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. 3. Oral H, Pappone C, Chugh A, Good E, Bogun F, Pelosi F, Jr., Bates ER, et al. Circumferential pulmonary-vein ablation for chronic atrial fibrillation. N Engl J Med 2006; 354:934–941. 4. Khan MN, Jais P, Cummings J, Di Biase L, Sanders P, Martin DO, Kautzner J, et al. Pulmonary-vein isolation for atrial fibrillation in patients with heart failure. N Engl J Med 2008; 359:1778– 1785. 5. Wazni OM, Marrouche NF, Martin DO, Verma A, Bhargava M, Saliba W, Bash D, et al. Radiofrequency ablation vs antiarrhythmic drugs as first-line treatment of symptomatic atrial fibrillation: A randomized trial. J Am Med Assoc 2005; 293:2634–2640. 6. European Heart Rhythm Association, European Cardiac Arrhythmia Society, American College of Cardiology, American Heart Association, Society of Thoracic Surgeons, Calkins H, Brugada J, et al. HRS/EHRA/ECAS expert consensus statement on catheter and surgical ablation of atrial fibrillation: Recommendations for personnel, policy, procedures and follow-up. A report of the Heart Rhythm Society (HRS) Task Force on Catheter and Surgical Ablation of Atrial Fibrillation. Heart Rhythm 2007; 4:816–861.
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7. Kneeland PP, Fang MC. Trends in catheter ablation for atrial fibrillation in the United States. J Hosp Med 2009; 4:E1–E5. 8. Bertaglia E, Zoppo F, Tondo C, Colella A, Mantovan R, Senatore G, Bottoni N, et al. Early complications of pulmonary vein catheter ablation for atrial fibrillation: A multicenter prospective registry on procedural safety. Heart Rhythm 2007; 4:1265–1271. 9. Cappato R, Calkins H, Chen SA, Davies W, Iesaka Y, Kalman J, Kim YH, et al. Prevalence and causes of fatal outcome in catheter ablation of atrial fibrillation. J Am Coll Cardiol 2009; 53:1798–1803. 10. Cappato R, Calkins H, Chen SA, Davies W, Iesaka Y, Kalman J, Kim YH, et al. Worldwide survey on the methods, efficacy, and safety of catheter ablation for human atrial fibrillation. Circulation 2005; 111:1100–1105. 11. Piccini JP, Lopes RD, Kong MH, Hasselblad V, Jackson K, Al-Khatib SM. Pulmonary vein isolation for the maintenance of sinus rhythm in patients with atrial fibrillation: A meta-analysis of randomized, controlled trials. Circ Arrhythm Electrophysiol 2009; 2:626–633. 12. Bunch TJ, Asirvatham SJ, Friedman PA, Monahan KH, Munger TM, Rea RF, Sinak LJ, et al. Outcomes after cardiac perforation during radiofrequency ablation of the atrium. J Cardiovasc Electrophysiol 2005; 16:1172–1179. 13. Kuck KH, Reddy VY, Schmidt B, Natale A, Neuzil P, Saoudi N, Kautzner J, et al. A novel radiofrequency ablation catheter using contact force sensing: Toccata study. Heart Rhythm 2012; 9:18–23. 14. Perna F, Heist EK, Danik SB, Barrett CD, Ruskin JN, Mansour M. Assessment of catheter tip contact force resulting in cardiac perforation in swine atria using force sensing technology. Circ Arrhythm Electrophysiol 2011; 4:218–224.
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