250
One Size Doesn’t Fit All: AF Ablation, Complications, and Patients with Structural Heart Disease GRANT V. CHOW, M.D. and DAVID D. SPRAGG, M.D. From the Johns Hopkins Hospital, Baltimore, Maryland, USA
hypertrophic cardiomyopathy, atrial fibrillation, ablation, complications Editorial Comment Catheter ablation for atrial fibrillation (AF) has become a widely accepted therapy for appropriate patients, typically those with AF that is highly symptomatic and refractory to therapy with antiarrhythmic medications.1 And while enthusiasm for ablative AF therapy continues to grow, AF ablation remains a challenging and imperfect procedure.2 Over the last decade there has been a rapid evolution in the strategies used during ablative AF therapy. Focal and segmental ablation has given way, in most centers, to wide-area circumferential pulmonary vein isolation; new targets, including rotors and autonomic ganglia, are under investigation. At the same time, a parallel evolution in ablative technologies has occurred, with the advent of irrigated catheters, cryoablation, and balloon-based therapies. And yet, despite undeniable progress in terms of AF ablation theory and practice, longterm single-procedure success rates remain frustratingly low and complication rates stubbornly high when compared with other catheter-based electrophysiological procedures. Ablation strategies and technological advancements to optimize the benefit-to-risk calculation of AF ablation are critical to delivery of safe and effective therapy, but only insomuch as they serve to inform the central question facing practitioners and patients considering AF ablation: does a particular patient’s constellation of symptoms and substrate (age, gender, comorbidities) justify the risks inherent with catheter ablation? In the current issue of Journal of Cardiovascular Electrophysiology, Hoffmann et al. provide important data on the relationship between patient substrate and observed periprocedural complication rates from PVI for AF, providing useful information to help with that central consideration of substrate and procedural risk.3 The authors provide analysis from the German Ablation Registry (GAR), in which periprocedural complications were catalogued in 6,211 patients undergoing PVI (roughly 90% of patients) or other ablative approaches (linear, segmental, or focal). Ablations were performed at 55 centers from 2007 to 2011. Such large patient volumes allowed the authors to stratify patients by presence and type of structural heart disease (HD), including those free of HD, those with hypertensive HD (HHD), those with coronary artery disJ Cardiovasc Electrophysiol, Vol. 25, pp. 250-252, March 2014. No disclosures. Address for correspondence: David Spragg, M.D., Johns Hopkins Hospital, FHRS, Carnegie 568, Baltimore, MD 21287, USA. Fax: 410-550-1183; E-mail: [email protected] doi: 10.1111/jce.12338
ease (CAD), and those with cardiomyopathy (CM). Patient records were surveyed at 30-day postablation, and complications were systematically recorded. In nearly 4,000 of the original patients, a 1-year follow-up call to discover any latepresenting complications was made. Other patient characteristics (age, gender, AF type) and procedural details (ablative approach, power delivered, and some aspects of anticoagulation strategy used) were tracked as well. The authors tabulated complications and categorized them as minor (spontaneous resolution, no sequellae or prolonged hospital stay), or major (those resulting in permanent injury or death, requiring an intervention, or prolonging hospital stay by over 2 days). Major complications were subclassified as severe (including, for instance, acute myocardial infarction, CVA, tamponade, or major bleeding requiring transfusion) or moderate (TIA, CPR, pneumothorax, heart block, or peripheral vascular injury). Deaths, of which there were 2 (both due to tamponade), were recorded as well. The authors do not specify how atrioesophageal fistulae or phrenic nerve injury were categorized, though presumably the former would be regarded as severe and the latter as moderate. Analysis of their data revealed 4 major findings. First, the overall rate of complications (minor and major) in the total group was 6.3%, and the rate of major complications in the entire cohort was 3.6%. Second, major complications occurred at a higher rate in patients with HHD than in the other groups (no HD, CAD, and CM). This finding was driven principally by increased rates of vascular injury and increased CVA rates in HHD patients compared with the others. Third, age predicted adverse events. Fourth, male patients had a lower rate of major, severe complications. In considering the data provided by the GAR, readers and editorialists alike are faced with the requisite components of critical appraisal: are the results believable, are they generalizable, and are they important? Our impression is that the authors have compiled a large, carefully collected, well defined set of data that complements and reinforces published data on the complications associated with AF ablation. The data in this study are based on a large series of patients drawn from many centers, and followed in a prospectively designed, reasonably rigorous manner. The major complication rate reported by the authors (the sum of moderate, severe, and fatal outcomes in the entire cohort, presented in Table 6) of 4.31% is certainly consistent with the major complication rate of 4.5% reported by Cappato in his updated worldwide survey of AF ablationists from 2010,4 and with the 5.1% complication rate reported by Shah et al. analyzing the California State registry of patients undergoing AF ablation.5 At Johns Hopkins, we have collected our own set of data on procedural outcomes and complication
Chow and Spragg Editorial Comment
rates, predictors of complications, and trends in complications over time as a function of institutional experience.6,7 Like the GAR group, we have found that rates of major complications occur at a rate of 2–4%. We have also found that adverse events occur with greater frequency in the elderly and in women. Because of the large numbers of patients enrolled in the GAR, the rigor of definitions and of followup, and (less importantly) because the data seem consistent with a variety of already published reports, the findings in the current publication are entirely believable. Second is the issue of generalizability, and here, too, Hoffmann et al. are to be commended for compiling a translatable body of data. The GAR, by collecting information on thousands of patients with a range of demographic profiles and comorbidities, provides a set of data that appears to be readily applicable to the general patient population served by AF ablationists. Similarly, because the data are drawn from a wide range of practices (over 50 centers) and presumably an even larger number of individual practitioners, the results are not biased by the skills, preferences, or idiosyncratic practice patterns of a small number of operators. It must be said, though, that the same “real-world” aspect of data collection that makes the GAR data valuable and applicable also imposes some unfortunate limitations on analysis of the results. Two missing pieces of information are particularly noteworthy by their absence. One is systematic recording of anticoagulation strategies for patients undergoing ablation. While some data have been provided on use of intra- and postprocedural heparin, warfarin, and antiplatelet agents, the authors acknowledge that their study cannot fully address the interplay between cardiac substrate, anticoagulation strategy, and outcome. For instance, rates of performing the procedure on patients fully anticoagulated with warfarin (with additional heparin therapy during the procedure) versus bridging patients with low-molecular weight heparin around the procedure are not provided. This seems like a missed opportunity, given that one of the study’s most significant findings is an increase in thromboembolic events in patients with HHD. Second, there are no outcomes data provided from this cohort. And while it is an unfair assertion that every investigation of complication rates must provide outcomes data in the same manuscript, it is helpful to have some sense of procedural success rates (both absolute, and among compared groups) when considering the risks of ablation. A previous publication from the GAR group,8 looking at over 7,000 patients undergoing ablative therapy for AF in roughly the same time period as the current study, found that in patients over 45 years of age the 1-year recurrence rate of AF was approximately 50%. That efficacy rate may not be directly applicable to the population reported on here, and certainly has not been stratified by presence and type of structural HD, but it does provide a general impression of procedural success for the thousands of patients in the German registry. Given the strengths and limitations of the data presented, we are left with the question of whether those data are important. In our view, it is critically important. Ablative therapies for AF must be recognized for what they are–highly invasive, potentially injurious procedures with no demonstrable benefit (to date) in terms of mortality reduction. As such, the discussion between physician and patient when considering AF ablation needs to be particularly well informed and clear in fleshing out the anticipated benefits and risks. The
251
groups identified by this study at increased risk of serious adverse events—those with HHD, the elderly, women—are large and increasing groups in the population. Data like that provided in this study are important for several reasons. First, it provides reassurance that patients with a wide range of cardiac comorbidities can undergo PVI with a reasonably low risk of periprocedural injury. Second, by giving comparative rates of adverse events it allows for a tailored discussion with patients, based on real data, about expectations for complications. That sort of discussion is a duty we owe our patients, and is well served by the work of Hoffmann et al. with this report. At Johns Hopkins, physicians performing AF ablation typically have a fairly blunt discussion about the anticipated risks and benefits of PVI (and ancillary procedures) with patients considering the procedure. That discussion is informed by patient characteristics (age, gender, comorbidities, LA size), arrhythmia characteristics (paroxysmal, persistent, or longstanding persistent AF), and procedural characteristics (simple PVI versus PVI and ancillary ablation). The results from Hoffmann et al. provide further refinement of that discussion, particularly in patients with structural HD, and for that the authors are to be congratulated. References 1. Calkins H, Kuck KH, Cappato R, Brugada J, Camm AJ, Chen SA, Crijns HJ, Damiano RJ Jr, Davies DW, DiMarco J, Edgerton J, Ellenbogen K, Ezekowitz MD, Haines DE, Haissaguerre M, Hindricks G, Iesaka Y, Jackman W, Jalife J, Jais P, Kalman J, Keane D, Kim YH, Kirchhof P, Klein G, Kottkamp H, Kumagai K, Lindsay BD, Mansour M, Marchlinski FE, McCarthy PM, Mont JL, Morady F, Nademanee K, Nakagawa H, Natale A, Nattel S, Packer DL, Pappone C, Prystowsky E, Raviele A, Reddy V, Ruskin JN, Shemin RJ, Tsao HM, Wilber D; Heart Rhythm Society Task Force on Catheter and Surgical Ablation of Atrial Fibrillation. 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. Developed in partnership with the European Heart Rhythm Association (EHRA), a registered branch of the European Society of Cardiology (ESC) and the European Cardiac Arrhythmia Society (ECAS); and in collaboration with the American College of Cardiology (ACC), American Heart Association (AHA), the Asia Pacific Heart Rhythm Society (APHRS), and the Society of Thoracic Surgeons (STS). Endorsed by the governing bodies of the American College of Cardiology Foundation, the American Heart Association, the European Cardiac Arrhythmia Society, the European Heart Rhythm Association, the Society of Thoracic Surgeons, the Asia Pacific Heart Rhythm Society, and the Heart Rhythm Society. Heart Rhythm 2012;9:632-696. 2. Deshmukh A, Patel NJ, Pant S, Shah N, Chothani A, Mehta K, Grover P, Singh V, Vallurupalli S, Savani GT, Badheka A, Tuliani T, Dabhadkar K, Dibu G, Reddy YM, Sewani A, Kowalski M, Mitrani R, Paydak H, Viles-Gonzalez JF. In-hospital complications associated with catheter ablation of atrial fibrillation in the United States between 2000 and 2010: Analysis of 93 801 procedures. Circulation 2013;128:2104-2112. 3. Hoffmann B, Kuck KH, Andresen D, Spitzer SG, Hoffmann E, Schumacher B, Eckardt L, Brachmann J, Becker R, Steven D, Rostock T, Junger C, San M, Senges J, willems S: Impact of structural heart disease on the acute complication rate in atrial fibrillation ablation: Results from the German Ablation Registry. J Cardiovasc Electrophysiol 2014;25:242-249. 4. Cappato R, Calkins H, Chen SA, Davies W, Iesaka Y, Kalman J, Kim YH, Klein G, Natale A, Packer D, Skanes A, Ambrogi F, Biganzoli E: Updated worldwide survey on the methods, efficacy, and safety of catheter ablation for human atrial fibrillation. Circ Arrhythm Electrophysiol 2010;3: 32-38. 5. Shah RU, Freeman JV, Shilane D, Wang PJ, Go AS, Hlatky MA: Procedural complications, rehospitalizations, and repeat procedures after catheter ablation for atrial fibrillation. J Am Coll Cardiol 2012;59:143-149.
252
Journal of Cardiovascular Electrophysiology
Vol. 25, No. 3, March 2014
6. Spragg DD, Dalal D, Cheema A, Scherr D, Chilukuri K, Cheng A, Henrikson CA, Marine JE, Berger RD, Dong J, Calkins H: Complications of catheter ablation for atrial fibrillation: Incidence and predictors. J Cardiovasc Electrophysiol 2008;19:627-631. 7. Hoyt H, Bhonsale A, Chilukuri K, Alhumaid F, Needleman M, Edwards D, Govil A, Nazarian S, Cheng A, Henrikson CA, Sinha S, Marine JE, Berger R, Calkins H, Spragg DD: Complications arising from catheter ab-
lation of atrial fibrillation: Temporal trends and predictors. Heart Rhythm 2011;8:1869-1874. 8. Chun KR, Schmidt B, Kuck KH, Andresen D, Willems S, Spitzer SG, Hoffmann E, Schumacher B, Eckardt L, Seidl K, J¨unger C, Horack M, Brachmann J, Senges J: Catheter ablation of atrial fibrillation in the young: Insights from the German Ablation Registry. Clin Res Cardiol 2013;102:459-468.
One Size Doesn’t Fit All: AF Ablation, Complications, and Patients with Structural Heart Disease GRANT V. CHOW, M.D. and DAVID D. SPRAGG, M.D. From the Johns Hopkins Hospital, Baltimore, Maryland, USA
hypertrophic cardiomyopathy, atrial fibrillation, ablation, complications Editorial Comment Catheter ablation for atrial fibrillation (AF) has become a widely accepted therapy for appropriate patients, typically those with AF that is highly symptomatic and refractory to therapy with antiarrhythmic medications.1 And while enthusiasm for ablative AF therapy continues to grow, AF ablation remains a challenging and imperfect procedure.2 Over the last decade there has been a rapid evolution in the strategies used during ablative AF therapy. Focal and segmental ablation has given way, in most centers, to wide-area circumferential pulmonary vein isolation; new targets, including rotors and autonomic ganglia, are under investigation. At the same time, a parallel evolution in ablative technologies has occurred, with the advent of irrigated catheters, cryoablation, and balloon-based therapies. And yet, despite undeniable progress in terms of AF ablation theory and practice, longterm single-procedure success rates remain frustratingly low and complication rates stubbornly high when compared with other catheter-based electrophysiological procedures. Ablation strategies and technological advancements to optimize the benefit-to-risk calculation of AF ablation are critical to delivery of safe and effective therapy, but only insomuch as they serve to inform the central question facing practitioners and patients considering AF ablation: does a particular patient’s constellation of symptoms and substrate (age, gender, comorbidities) justify the risks inherent with catheter ablation? In the current issue of Journal of Cardiovascular Electrophysiology, Hoffmann et al. provide important data on the relationship between patient substrate and observed periprocedural complication rates from PVI for AF, providing useful information to help with that central consideration of substrate and procedural risk.3 The authors provide analysis from the German Ablation Registry (GAR), in which periprocedural complications were catalogued in 6,211 patients undergoing PVI (roughly 90% of patients) or other ablative approaches (linear, segmental, or focal). Ablations were performed at 55 centers from 2007 to 2011. Such large patient volumes allowed the authors to stratify patients by presence and type of structural heart disease (HD), including those free of HD, those with hypertensive HD (HHD), those with coronary artery disJ Cardiovasc Electrophysiol, Vol. 25, pp. 250-252, March 2014. No disclosures. Address for correspondence: David Spragg, M.D., Johns Hopkins Hospital, FHRS, Carnegie 568, Baltimore, MD 21287, USA. Fax: 410-550-1183; E-mail: [email protected] doi: 10.1111/jce.12338
ease (CAD), and those with cardiomyopathy (CM). Patient records were surveyed at 30-day postablation, and complications were systematically recorded. In nearly 4,000 of the original patients, a 1-year follow-up call to discover any latepresenting complications was made. Other patient characteristics (age, gender, AF type) and procedural details (ablative approach, power delivered, and some aspects of anticoagulation strategy used) were tracked as well. The authors tabulated complications and categorized them as minor (spontaneous resolution, no sequellae or prolonged hospital stay), or major (those resulting in permanent injury or death, requiring an intervention, or prolonging hospital stay by over 2 days). Major complications were subclassified as severe (including, for instance, acute myocardial infarction, CVA, tamponade, or major bleeding requiring transfusion) or moderate (TIA, CPR, pneumothorax, heart block, or peripheral vascular injury). Deaths, of which there were 2 (both due to tamponade), were recorded as well. The authors do not specify how atrioesophageal fistulae or phrenic nerve injury were categorized, though presumably the former would be regarded as severe and the latter as moderate. Analysis of their data revealed 4 major findings. First, the overall rate of complications (minor and major) in the total group was 6.3%, and the rate of major complications in the entire cohort was 3.6%. Second, major complications occurred at a higher rate in patients with HHD than in the other groups (no HD, CAD, and CM). This finding was driven principally by increased rates of vascular injury and increased CVA rates in HHD patients compared with the others. Third, age predicted adverse events. Fourth, male patients had a lower rate of major, severe complications. In considering the data provided by the GAR, readers and editorialists alike are faced with the requisite components of critical appraisal: are the results believable, are they generalizable, and are they important? Our impression is that the authors have compiled a large, carefully collected, well defined set of data that complements and reinforces published data on the complications associated with AF ablation. The data in this study are based on a large series of patients drawn from many centers, and followed in a prospectively designed, reasonably rigorous manner. The major complication rate reported by the authors (the sum of moderate, severe, and fatal outcomes in the entire cohort, presented in Table 6) of 4.31% is certainly consistent with the major complication rate of 4.5% reported by Cappato in his updated worldwide survey of AF ablationists from 2010,4 and with the 5.1% complication rate reported by Shah et al. analyzing the California State registry of patients undergoing AF ablation.5 At Johns Hopkins, we have collected our own set of data on procedural outcomes and complication
Chow and Spragg Editorial Comment
rates, predictors of complications, and trends in complications over time as a function of institutional experience.6,7 Like the GAR group, we have found that rates of major complications occur at a rate of 2–4%. We have also found that adverse events occur with greater frequency in the elderly and in women. Because of the large numbers of patients enrolled in the GAR, the rigor of definitions and of followup, and (less importantly) because the data seem consistent with a variety of already published reports, the findings in the current publication are entirely believable. Second is the issue of generalizability, and here, too, Hoffmann et al. are to be commended for compiling a translatable body of data. The GAR, by collecting information on thousands of patients with a range of demographic profiles and comorbidities, provides a set of data that appears to be readily applicable to the general patient population served by AF ablationists. Similarly, because the data are drawn from a wide range of practices (over 50 centers) and presumably an even larger number of individual practitioners, the results are not biased by the skills, preferences, or idiosyncratic practice patterns of a small number of operators. It must be said, though, that the same “real-world” aspect of data collection that makes the GAR data valuable and applicable also imposes some unfortunate limitations on analysis of the results. Two missing pieces of information are particularly noteworthy by their absence. One is systematic recording of anticoagulation strategies for patients undergoing ablation. While some data have been provided on use of intra- and postprocedural heparin, warfarin, and antiplatelet agents, the authors acknowledge that their study cannot fully address the interplay between cardiac substrate, anticoagulation strategy, and outcome. For instance, rates of performing the procedure on patients fully anticoagulated with warfarin (with additional heparin therapy during the procedure) versus bridging patients with low-molecular weight heparin around the procedure are not provided. This seems like a missed opportunity, given that one of the study’s most significant findings is an increase in thromboembolic events in patients with HHD. Second, there are no outcomes data provided from this cohort. And while it is an unfair assertion that every investigation of complication rates must provide outcomes data in the same manuscript, it is helpful to have some sense of procedural success rates (both absolute, and among compared groups) when considering the risks of ablation. A previous publication from the GAR group,8 looking at over 7,000 patients undergoing ablative therapy for AF in roughly the same time period as the current study, found that in patients over 45 years of age the 1-year recurrence rate of AF was approximately 50%. That efficacy rate may not be directly applicable to the population reported on here, and certainly has not been stratified by presence and type of structural HD, but it does provide a general impression of procedural success for the thousands of patients in the German registry. Given the strengths and limitations of the data presented, we are left with the question of whether those data are important. In our view, it is critically important. Ablative therapies for AF must be recognized for what they are–highly invasive, potentially injurious procedures with no demonstrable benefit (to date) in terms of mortality reduction. As such, the discussion between physician and patient when considering AF ablation needs to be particularly well informed and clear in fleshing out the anticipated benefits and risks. The
251
groups identified by this study at increased risk of serious adverse events—those with HHD, the elderly, women—are large and increasing groups in the population. Data like that provided in this study are important for several reasons. First, it provides reassurance that patients with a wide range of cardiac comorbidities can undergo PVI with a reasonably low risk of periprocedural injury. Second, by giving comparative rates of adverse events it allows for a tailored discussion with patients, based on real data, about expectations for complications. That sort of discussion is a duty we owe our patients, and is well served by the work of Hoffmann et al. with this report. At Johns Hopkins, physicians performing AF ablation typically have a fairly blunt discussion about the anticipated risks and benefits of PVI (and ancillary procedures) with patients considering the procedure. That discussion is informed by patient characteristics (age, gender, comorbidities, LA size), arrhythmia characteristics (paroxysmal, persistent, or longstanding persistent AF), and procedural characteristics (simple PVI versus PVI and ancillary ablation). The results from Hoffmann et al. provide further refinement of that discussion, particularly in patients with structural HD, and for that the authors are to be congratulated. References 1. Calkins H, Kuck KH, Cappato R, Brugada J, Camm AJ, Chen SA, Crijns HJ, Damiano RJ Jr, Davies DW, DiMarco J, Edgerton J, Ellenbogen K, Ezekowitz MD, Haines DE, Haissaguerre M, Hindricks G, Iesaka Y, Jackman W, Jalife J, Jais P, Kalman J, Keane D, Kim YH, Kirchhof P, Klein G, Kottkamp H, Kumagai K, Lindsay BD, Mansour M, Marchlinski FE, McCarthy PM, Mont JL, Morady F, Nademanee K, Nakagawa H, Natale A, Nattel S, Packer DL, Pappone C, Prystowsky E, Raviele A, Reddy V, Ruskin JN, Shemin RJ, Tsao HM, Wilber D; Heart Rhythm Society Task Force on Catheter and Surgical Ablation of Atrial Fibrillation. 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. Developed in partnership with the European Heart Rhythm Association (EHRA), a registered branch of the European Society of Cardiology (ESC) and the European Cardiac Arrhythmia Society (ECAS); and in collaboration with the American College of Cardiology (ACC), American Heart Association (AHA), the Asia Pacific Heart Rhythm Society (APHRS), and the Society of Thoracic Surgeons (STS). Endorsed by the governing bodies of the American College of Cardiology Foundation, the American Heart Association, the European Cardiac Arrhythmia Society, the European Heart Rhythm Association, the Society of Thoracic Surgeons, the Asia Pacific Heart Rhythm Society, and the Heart Rhythm Society. Heart Rhythm 2012;9:632-696. 2. Deshmukh A, Patel NJ, Pant S, Shah N, Chothani A, Mehta K, Grover P, Singh V, Vallurupalli S, Savani GT, Badheka A, Tuliani T, Dabhadkar K, Dibu G, Reddy YM, Sewani A, Kowalski M, Mitrani R, Paydak H, Viles-Gonzalez JF. In-hospital complications associated with catheter ablation of atrial fibrillation in the United States between 2000 and 2010: Analysis of 93 801 procedures. Circulation 2013;128:2104-2112. 3. Hoffmann B, Kuck KH, Andresen D, Spitzer SG, Hoffmann E, Schumacher B, Eckardt L, Brachmann J, Becker R, Steven D, Rostock T, Junger C, San M, Senges J, willems S: Impact of structural heart disease on the acute complication rate in atrial fibrillation ablation: Results from the German Ablation Registry. J Cardiovasc Electrophysiol 2014;25:242-249. 4. Cappato R, Calkins H, Chen SA, Davies W, Iesaka Y, Kalman J, Kim YH, Klein G, Natale A, Packer D, Skanes A, Ambrogi F, Biganzoli E: Updated worldwide survey on the methods, efficacy, and safety of catheter ablation for human atrial fibrillation. Circ Arrhythm Electrophysiol 2010;3: 32-38. 5. Shah RU, Freeman JV, Shilane D, Wang PJ, Go AS, Hlatky MA: Procedural complications, rehospitalizations, and repeat procedures after catheter ablation for atrial fibrillation. J Am Coll Cardiol 2012;59:143-149.
252
Journal of Cardiovascular Electrophysiology
Vol. 25, No. 3, March 2014
6. Spragg DD, Dalal D, Cheema A, Scherr D, Chilukuri K, Cheng A, Henrikson CA, Marine JE, Berger RD, Dong J, Calkins H: Complications of catheter ablation for atrial fibrillation: Incidence and predictors. J Cardiovasc Electrophysiol 2008;19:627-631. 7. Hoyt H, Bhonsale A, Chilukuri K, Alhumaid F, Needleman M, Edwards D, Govil A, Nazarian S, Cheng A, Henrikson CA, Sinha S, Marine JE, Berger R, Calkins H, Spragg DD: Complications arising from catheter ab-
lation of atrial fibrillation: Temporal trends and predictors. Heart Rhythm 2011;8:1869-1874. 8. Chun KR, Schmidt B, Kuck KH, Andresen D, Willems S, Spitzer SG, Hoffmann E, Schumacher B, Eckardt L, Seidl K, J¨unger C, Horack M, Brachmann J, Senges J: Catheter ablation of atrial fibrillation in the young: Insights from the German Ablation Registry. Clin Res Cardiol 2013;102:459-468.
