nodal reentrant tachycardia [AVNRT], in atrial flutter, and in macroreentrant or focal atrial tachycardias) and in idiopathic ventricular ectopy/tachycardia, the success rates are high. Catheter ablation of atrial fibrillation is increasingly offered to drug-refractory symptomatic patients with paroxysmal tachycardia and selected patients with persistent atrial fibrillation with the aim of isolating the pulmonary vein where most ectopic foci are located and/or to modify the anatomic left atrial substrate ( table 1). (See 'Indications and clinical use' above.) For life-threatening ventricular tachyarrhythmias (ventricular tachycardias and ventricular fibrillation), the mainstay treatment is the implantable cardioverter-defibrillator (ICD) alone or in combination of pharmacological therapy for the prevention of arrhythmia episodes. Catheter ablation may be useful in reducing the frequency of appropriate ICD discharges and to improve patient quality of life or to treat the arrhythmia storm in patients with ICD. The potential risks and benefits of the ablation procedure include those risks associated with an invasive electrophysiology study (EP study) alone ( table 2). Generally, risks are https://www.uptodate.com/contents/overview-of-catheter-ablation-of-cardiac-arrhythmias/print 12/38 7/5/23, 8:12 AM Overview of catheter ablation of cardiac arrhythmias - UpToDate lower in experienced operators and centers that perform larger numbers of procedures. (See 'Complications' above.) ACKNOWLEDGMENT The UpToDate editorial staff acknowledges Bradley Knight, MD, FACC, Mark Link, MD, Brian Olshansky, MD, and Leonard Ganz, MD, FHRS, FACC, who contributed to earlier versions of this topic review. Use of UpToDate is subject to the Terms of Use. REFERENCES 1. 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Errors in pulmonary vein identification and ostia location in the absence of pulmonary vein imaging. Heart Rhythm 2005; 2:1082. 32. Packer DL. Evolution of mapping and anatomic imaging of cardiac arrhythmias. J Cardiovasc Electrophysiol 2004; 15:839. 33. Schilling RJ, Peters NS, Davies DW. Noncontact mapping of cardiac arrhythmias. J Electrocardiol 1999; 32 Suppl:13. 34. Schneider MA, Ndrepepa G, Zrenner B, et al. Noncontact mapping-guided catheter ablation of atrial fibrillation associated with left atrial ectopy. J Cardiovasc Electrophysiol 2000; 11:475. 35. Schilling RJ, Kadish AH, Peters NS, et al. Endocardial mapping of atrial fibrillation in the human right atrium using a non-contact catheter. Eur Heart J 2000; 21:550. https://www.uptodate.com/contents/overview-of-catheter-ablation-of-cardiac-arrhythmias/print 15/38 7/5/23, 8:12 AM Overview of catheter ablation of cardiac arrhythmias - UpToDate 36. Cosio FG, Arribas F, Lopez-Gil M, Gonzalez HD. Radiofrequency ablation of atrial flutter. J Cardiovasc Electrophysiol 1996; 7:60. 37. Ruffy R, Imran MA, Santel DJ, Wharton JM. Radiofrequency delivery through a cooled catheter tip allows the creation of larger endomyocardial lesions in the ovine heart. J Cardiovasc Electrophysiol 1995; 6:1089. 38. Ja s P, Shah DC, Ha ssaguerre M, et al. Prospective randomized comparison of irrigated-tip versus conventional-tip catheters for ablation of common flutter. Circulation 2000; 101:772. 39. Yamane T, Ja s P, Shah DC, et al. Efficacy and safety of an irrigated-tip catheter for the ablation of accessory pathways resistant to conventional radiofrequency ablation. Circulation 2000; 102:2565. 40. Calkins H, Epstein A, Packer D, et al. Catheter ablation of ventricular tachycardia in patients with structural heart disease using cooled radiofrequency energy: results of a prospective multicenter study. Cooled RF Multi Center Investigators Group. J Am Coll Cardiol 2000; 35:1905. 41. Soejima K, Delacretaz E, Suzuki M, et al. Saline-cooled versus standard radiofrequency catheter ablation for infarct-related ventricular tachycardias. Circulation 2001; 103:1858. 42. Jumrussirikul P, Chen JT, Jenkins M, et al. Prospective comparison of temperature guided microwave and radiofrequency catheter ablation in the swine heart. Pacing Clin Electrophysiol 1998; 21:1364. 43. Skanes AC, Klein G, Krahn A, Yee R. Cryoablation: potentials and pitfalls. J Cardiovasc Electrophysiol 2004; 15:S28. 44. Rodriguez LM, Leunissen J, Hoekstra A, et al. Transvenous cold mapping and cryoablation of the AV node in dogs: observations of chronic lesions and comparison to those obtained using radiofrequency ablation. J Cardiovasc Electrophysiol 1998; 9:1055. 45. Skanes AC, Dubuc M, Klein GJ, et al. Cryothermal ablation of the slow pathway for the elimination of atrioventricular nodal reentrant tachycardia. Circulation 2000; 102:2856. 46. Rodriguez LM, Geller JC, Tse HF, et al. Acute results of transvenous cryoablation of supraventricular tachycardia (atrial fibrillation, atrial flutter, Wolff-Parkinson-White syndrome, atrioventricular nodal reentry tachycardia). J Cardiovasc Electrophysiol 2002; 13:1082. 47. Bradley CJ, Haines DE. Pulsed field ablation for pulmonary vein isolation in the treatment of atrial fibrillation. J Cardiovasc Electrophysiol 2020; 31:2136. 48. Reddy VY, Dukkipati SR, Neuzil P, et al. Pulsed Field Ablation of Paroxysmal Atrial Fibrillation: 1-Year Outcomes of IMPULSE, PEFCAT, and PEFCAT II. JACC Clin Electrophysiol 2021; 7:614. https://www.uptodate.com/contents/overview-of-catheter-ablation-of-cardiac-arrhythmias/print 16/38 7/5/23, 8:12 AM Overview of catheter ablation of cardiac arrhythmias - UpToDate 49. Calkins H, Yong P, Miller JM, et al. Catheter ablation of accessory pathways, atrioventricular nodal reentrant tachycardia, and the atrioventricular junction: final results of a prospective, multicenter clinical trial. The Atakr Multicenter Investigators Group. Circulation 1999; 99:262. 50. Bohnen M, Stevenson WG, Tedrow UB, et al. Incidence and predictors of major complications from contemporary catheter ablation to treat cardiac arrhythmias. Heart Rhythm 2011; 8:1661. 51. Gupta A, Perera T, Ganesan A, et al. Complications of catheter ablation of atrial fibrillation: a systematic review. Circ Arrhythm Electrophysiol 2013; 6:1082. 52. Kay GN, Epstein AE, Dailey SM, Plumb VJ. Role of radiofrequency ablation in the management of supraventricular arrhythmias: experience in 760 consecutive patients. J Cardiovasc Electrophysiol 1993; 4:371. 53. Chen SA, Chiang CE, Tai CT, et al. Complications of diagnostic electrophysiologic studies and radiofrequency catheter ablation in patients with tachyarrhythmias: an eight-year survey of 3,966 consecutive procedures in a tertiary referral center. Am J Cardiol 1996; 77:41. 54. Scheinman MM, Huang S. The 1998 NASPE prospective catheter ablation registry. Pacing Clin Electrophysiol 2000; 23:1020. 55. Katritsis DG, Zografos T, Siontis KC, et al. Endpoints for Successful Slow Pathway Catheter Ablation in Typical and Atypical Atrioventricular Nodal Re-Entrant Tachycardia: A Contemporary, Multicenter Study. J Am Coll Cardiol EP 2019; 5:113. 56. Chrispin J, Misra S, Marine JE, et al. Current management and clinical outcomes for catheter ablation of atrioventricular nodal re-entrant tachycardia. Europace 2018; 20:e51. 57. Heidbuchel H, Wittkampf FH, Vano E, et al. Practical ways to reduce radiation dose for patients and staff during device implantations and electrophysiological procedures. Europace 2014; 16:946. 58. Paydak H, Kall JG, Burke MC, et al. Atrial fibrillation after radiofrequency ablation of type I atrial flutter: time to onset, determinants, and clinical course. Circulation 1998; 98:315. 59. Kocovic DZ, Harada T, Shea JB, et al. Alterations of heart rate and of heart rate variability after radiofrequency catheter ablation of supraventricular tachycardia. Delineation of parasympathetic pathways in the human heart. Circulation 1993; 88:1671. 60. Psychari SN, Theodorakis GN, Koutelou M, et al. Cardiac denervation after radiofrequency ablation of supraventricular tachycardias. Am J Cardiol 1998; 81:725. 61. Hamdan MH, Page RL, Wasmund SL, et al. Selective parasympathetic denervation following posteroseptal ablation for either atrioventricular nodal reentrant tachycardia or accessory https://www.uptodate.com/contents/overview-of-catheter-ablation-of-cardiac-arrhythmias/print 17/38 7/5/23, 8:12 AM Overview of catheter ablation of cardiac arrhythmias - UpToDate pathways. Am J Cardiol 2000; 85:875. 62. Geelen P, Brugada J, Andries E, Brugada P. Ventricular fibrillation and sudden death after radiofrequency catheter ablation of the atrioventricular junction. Pacing Clin Electrophysiol 1997; 20:343. 63. Hamdan MH, Page RL, Sheehan CJ, et al. Increased sympathetic activity after atrioventricular junction ablation in patients with chronic atrial fibrillation. J Am Coll Cardiol 2000; 36:151. 64. Manolis AS, Vassilikos V, Maounis T, et al. Detection of myocardial injury during radiofrequency catheter ablation by measuring serum cardiac troponin I levels: procedural correlates. J Am Coll Cardiol 1999; 34:1099. 65. Katritsis D, Hossein-Nia M, Anastasakis A, et al. Use of troponin-T concentration and kinase isoforms for quantitation of myocardial injury induced by radiofrequency catheter ablation. Eur Heart J 1997; 18:1007. 66. Chen L, Wei T, Zeng C, et al. Effect of radiofrequency catheter ablation on plasma B-type natriuretic peptide. Pacing Clin Electrophysiol 2005; 28:200. 67. Anselmino M, Scaglione M, Battaglia A, et al. Iatrogenic atrial septal defects following atrial fibrillation transcatheter ablation: a relevant entity? Europace 2014; 16:1562. 68. Madhavan M, Yao X, Sangaralingham LR, et al. Ischemic Stroke or Systemic Embolism After Transseptal Ablation of Arrhythmias in Patients With Cardiac Implantable Electronic Devices. J Am Heart Assoc 2016; 5:e003163. Topic 1007 Version 36.0 https://www.uptodate.com/contents/overview-of-catheter-ablation-of-cardiac-arrhythmias/print 18/38 7/5/23, 8:12 AM Overview of catheter ablation of cardiac arrhythmias - UpToDate GRAPHICS [1-3] Indications for catheter ablation of arrhythmias Class I Paroxysmal SVT Symptomatic or medical refractory typical atrial flutter Symptomatic WPW Symptomatic PAF refractory to at least one class I/III drug Symptomatic VPBs in the setting of structurally normal heart VPB-induced cardiomyopathy Idiopathic VF induced by unifocal VPBs Idiopathic VT Bundle-branch reentrant VT Recurrent VT in ischemic cardiomyopathy refractory to amiodarone Class IIa Asymptomatic WPW with high-risk features or high-risk occupation Symptomatic PAF prior to treatment with class I/III drug Symptomatic persistent AF refractory to at least one class I/III drug or prior to class I/III drug Recurrent VT in NICM refractory to antiarrhythmic therapy Recurrent VT in adult congenital heart disease refractory to antiarrhythmic therapy Recurrent VT in ARVC refractory to beta blocker Class IIb Long-standing symptomatic persistent AF Select asymptomatic AF Recurrent VT in ischemic cardiomyopathy as an alternative to pharmacologic therapy SVT: supraventricular tachycardia; WPW: Wolff-Parkinson-White syndrome; PAF: paroxysmal atrial fibrillation; VPB: ventricular premature beat; VF: ventricular fibrillation; VT: ventricular tachycardia; AF: https://www.uptodate.com/contents/overview-of-catheter-ablation-of-cardiac-arrhythmias/print 19/38 7/5/23, 8:12 AM Overview of catheter ablation of cardiac arrhythmias - UpToDate atrial fibrillation; NICM: nonischemic cardiomyopathy; ARVC: arrhythmogenic right ventricular cardiomyopathy. References: 1. Al-Khatib SM, Stevenson WG, Ackerman MJ, et al. 2017 AHA/ACC/HRS Guideline for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. J Am Coll Cardiol 2017. 2. Calkins H, Hindricks G, Cappato R, et al. 2017 HRS/EHRA/ECAS/APHRS/SOLAECE expert consensus statement on catheter and surgical ablation of atrial brillation. Heart Rhythm 2017; 14:e275. 3. Page RL, Joglar JA, Caldwell MA, et al. 2015 ACC/AHA/HRS Guideline for the Management of Adult Patients With Supraventricular Tachycardia: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. J Am Coll Cardiol 2016; 67:e27. Graphic 117234 Version 1.0 https://www.uptodate.com/contents/overview-of-catheter-ablation-of-cardiac-arrhythmias/print 20/38 7/5/23, 8:12 AM Overview of catheter ablation of cardiac arrhythmias - UpToDate Electrocardiogram showing an ectopic atrial tachycardia originating from the tricuspid annulus Electrocardiographic tracing showing a narrow complex tachycardia with uniform P waves consistent with an ectopic atrial tachycardia originating from the tricuspid annulus. Prior to the final QRS complex, there is spontaneous return to normal sinus rhythm with P wave of a different morphology. Courtesy of Peter Kistler, MBBS, FRACP, PhD. Graphic 74611 Version 10.0 https://www.uptodate.com/contents/overview-of-catheter-ablation-of-cardiac-arrhythmias/print 21/38 7/5/23, 8:12 AM Overview of catheter ablation of cardiac arrhythmias - UpToDate Electrocardiogram (ECG) showing atrial tachycardia originating from the left superior pulmonary vein. Electrocardiographic tracing showing a narrow complex tachycardia with uniform P waves consistent with atrial tachycardia originating from the left superior pulmonary vein. The initial QRS complex shows a normal sinus beat, followed by the development of atrial tachycardia. Courtesy of Dr. Peter Kistler. Graphic 57390 Version 3.0 https://www.uptodate.com/contents/overview-of-catheter-ablation-of-cardiac-arrhythmias/print 22/38 7/5/23, 8:12 AM Overview of catheter ablation of cardiac arrhythmias - UpToDate Reentrant circuit of typical atrial flutter within the right atrium Schematic representation of reentrant circuit (red arrow) of typical (type 1) atrial flutter. The reentrant impulse rotates in a counterclockwise direction around the tricuspid annulus. The crista terminalis (CT) and eustacian ridge (ER) serve as lines of block, preventing the impulse from short-circuiting the annulus. Ablation is performed in the isthmus between the IVC and TA, which is an obligatory part of the circuit. SVC: superior vena cava; CS: coronary sinus; IVC: inferior vena cava; FO: foramen ovale Graphic 52904 Version 5.0 https://www.uptodate.com/contents/overview-of-catheter-ablation-of-cardiac-arrhythmias/print 23/38 7/5/23, 8:12 AM Overview of catheter ablation of cardiac arrhythmias - UpToDate Electrocardiogram single-lead multifocal atrial tachycardia Clinical features: Elderly patients Decompensation of pulmonary disease Postoperative Arrhythmia usually does not cause severe hemodynamic compromise High mortality ECG features: P waves have 3 forms Atrial rate is usually 100 to 200 bpm Atrial rate is irregular PR interval varies Isoelectric baseline between P waves May progress to atrial fibrillation ECG: electrocardiogram; bpm: beats per minute. Courtesy of Alfred Buxton, MD. Graphic 127222 Version 1.0 https://www.uptodate.com/contents/overview-of-catheter-ablation-of-cardiac-arrhythmias/print 24/38 7/5/23, 8:12 AM Overview of catheter ablation of cardiac arrhythmias - UpToDate 12-lead electrocardiogram (ECG) during electrophysiologic study showing pace mapping of an idiopathic RVOT tachycardia Left panel: 12 lead ECG of spontaneous ventricular tachycardia (VT) in a patient with a structurally normal heart. The VT has a left bundle branch block (LBBB) and an inferior axis morphology, suggesting that the origin is in the right ventricular outflow tract (RVOT). Right panel: A mapping catheter has been positioned in the RVOT and pacing is performed from its tip during sinus rhythm. The "pace map" closely approximates the QRS morphology of the spontaneous VT in all 12 leads, suggesting that the mapping catheter is at or near the VT focus. S: pacing stimulus artifact. Graphic 68142 Version 4.0 https://www.uptodate.com/contents/overview-of-catheter-ablation-of-cardiac-arrhythmias/print 25/38 7/5/23, 8:12 AM Overview of catheter ablation of cardiac arrhythmias - UpToDate 12-lead ECG showing pace map of ventricular tachycardia The QRS complexes on the twelve-lead ECG, recorded during spontaneous VT provoked by isoproterenol, are identical in each lead to those recorded during ventricular pacing. ECG: electrocardiogram; VT: ventricular tachycardia. Graphic 79938 Version 4.0 https://www.uptodate.com/contents/overview-of-catheter-ablation-of-cardiac-arrhythmias/print 26/38 7/5/23, 8:12 AM Overview of catheter ablation of cardiac arrhythmias - UpToDate Electrophysiology study (EPS) tracings showing concealed entrainment (A) Pacing from the distal electrode pair of the mapping/ablation catheter during mapping of sustained ventr tachycardia. On the left side of the figure are the last three stimuli during a train of pacing at a cycle length o milliseconds. Following pacing, the tachycardia (cycle length 430 milliseconds) resumes. The interval from the paced beat to resumption of tachycardia, measured in the distal ablation catheter (Abl d), is just 10 millisecon greater than the tachycardia cycle length. Note that the interval from the pacing stimulus to onset of the QRS is the same as the interval from the local electrogram to the QRS onset when VT resumes after pacing. Note a the paced VT morphology replicates the morphology of the spontaneous tachycardia. This is an example of "concealed entrainment" and implies the catheter is within a critical part of a reentrant circuit. (B) Same site on the ablation catheter (Abl d) during sinus rhythm as shown during VT in figure A. During sinu rhythm, a late potential is present. The vertical line denotes the end of the QRS complex. Delivery of radiofreq energy at this site resulted in termination of VT. The tachycardia was no longer inducible after ablation. Sites this displaying late potentials may be targeted during "substrate-guided ablation." VT: ventricular tachycardia. Graphic 107237 Version 2.0 https://www.uptodate.com/contents/overview-of-catheter-ablation-of-cardiac-arrhythmias/print 27/38 7/5/23, 8:12 AM Overview of catheter ablation of cardiac arrhythmias - UpToDate Electroanatomic voltage map from a normal subject The right ventricular (RV) voltage map in the right anterior oblique projection from a normal subject is obtained using electroanatomic mapping. The colors represent the amplitude of the local unipolar electrogram and blue and purple indicated normal unipolar voltage values ( 5 mV) throughout the RV. LA: left atrium; RA: right atrium. Reproduced with permission from: Boulos M, Lashevsky I, Reisner S, Gepstein L. J Am Coll Cardiol 2001; 38:2020. Copyright 2001 American College of Cardiology. http://www.elsevier.com/locate/jacc http://www.sciencedirect.com Graphic 63899 Version 4.0 https://www.uptodate.com/contents/overview-of-catheter-ablation-of-cardiac-arrhythmias/print 28/38 7/5/23, 8:12 AM Overview of catheter ablation of cardiac arrhythmias - UpToDate Echocardiographic and electroanatomic mapping of the right ventricle in arrhythmogenic right ventricular dysplasia Two-dimensional echocardiographic apical view of a patient with arrhythmogenic right ventricular dysplasia shows severe enlargement of the right ventricle (RV) and right atrium (RA) (panel A). The RV unipolar voltage maps, generated by electroanatomic mapping, are seen in the anteroposterior (panel B) and left anterior oblique views (panel C). There is extensive area of low voltage (red indicates <2 mV) in the apex and anterolateral free wall of the RV, with the septum being spared (purple indicates >5 mV). LA: left atrium; RVOT: RV outflow tract. Reproduced with permission from: Boulos M, Lashevsky I, Reisner S, Gepstein L. J Am Coll Cardiol 2001; 38:2020. Copyright 2001 American College of Cardiology. http://www.elsevier.com/locate/jacc http://www.sciencedirect.com Graphic 54163 Version 4.0 https://www.uptodate.com/contents/overview-of-catheter-ablation-of-cardiac-arrhythmias/print 29/38 7/5/23, 8:12 AM Overview of catheter ablation of cardiac arrhythmias - UpToDate Typical electroanatomic map of infarcted myocardium The electroanatomic map of a patient with a myocardial infarction shows large regions of abnormal electromechanical activity and reduced local shortening (red, abnormally contracting regions with values <4 percent). In contrast, a region in which function remains unhindered is a color-coded blue/purple, normal contractile function >12 percent. Reprinted with permission from: the American College of Cardiology (Journal of the American College of Cardiology, 2001, 37:1590-7). http://www.elsevier.com/locate/jacc http://www.sciencedirect.com Graphic 57238 Version 3.0 https://www.uptodate.com/contents/overview-of-catheter-ablation-of-cardiac-arrhythmias/print 30/38 7/5/23, 8:12 AM Overview of catheter ablation of cardiac arrhythmias - UpToDate Correlation between electroanatomic map and pathological sections of infarcted heart Panel A shows a section of the left ventricle in a patient with a subendocardial myocardial infarction (arrow). The superimposed colors in the reconstruction from an electroanatomic map (panel B) depict bipolar electrogram amplitude (BEA); purple indicates values >6.1 mV; red indicates values <2.1 mV. Beneath the reconstructed sections (panel C) are typical recordings of unipolar electrogram and derivatives, the unipolar electrogram amplitude (UEA) and slew rate (SR) and bipolar electrogram and amplitude from selected points at the core of the infarcted region (the distance between two white marks on the electrogram time scale denotes a 50-millisecond period). Reprinted with permission from the American College of Cardiology (Journal of the American College of Cardiology, 2001, 37:1590-7). http://www.elsevier.com/locate/jacc http://www.sciencedirect.com https://www.uptodate.com/contents/overview-of-catheter-ablation-of-cardiac-arrhythmias/print 31/38 7/5/23, 8:12 AM Overview of catheter ablation of cardiac arrhythmias - UpToDate Graphic 81609 Version 3.0 https://www.uptodate.com/contents/overview-of-catheter-ablation-of-cardiac-arrhythmias/print 32/38 7/5/23, 8:12 AM Overview of catheter ablation of cardiac arrhythmias - UpToDate Intracardiac and surface ECG recordings during electrophysiologic study and radiofrequency catheter ablation of typical atrial flutter Three surface ECG leads (I, aVF, V1) and intracardiac recordings from the high right atrium (HRA), a mapping catheter in the isthmus between the tricuspid valve and inferior vena cava (TV-IVC) (HBE1-2), eight recordings from a catheter extending from the lateral right atrial wall through the TV-IVC isthmus and into the ostium of the coronary sinus (CS15-1 to CS1-2), and right ventricular apex (RVA3-4) in a patient with typical atrial flutter. The tip of the mapping catheter was initially positioned on the tricuspid annulus, and then dragged through the TV-IVC isthmus to the ostium of the IVC during RF application; atrial flutter terminated. Note that the atrial activation (A) blocks between CS7-8 and CS5-6, which on fluoroscopy corresponded to the position of the mapping catheter. Fl: flutter waves; V: ventricular electrogram. Graphic 69946 Version 4.0 https://www.uptodate.com/contents/overview-of-catheter-ablation-of-cardiac-arrhythmias/print 33/38 7/5/23, 8:12 AM Overview of catheter ablation of cardiac arrhythmias - UpToDate Intracardiac and surface electrocardiogram (ECG) recordings during electrophysiologic study and radiofrequency catheter ablation of atrial flutter showing bidirectional isthmus block Shown are three surface ECG leads (I, aVF, V1) and intracardiac recordings from the high right atrium (HRA), eight recordings from a catheter extending from the lateral right atrial wall through the tricuspid valve-inferior vena cava (TV- IVC) isthmus and into the ostium of the coronary sinus (CS15-16 through CS1- 2), and right ventricular apex (RVA3-4) in a patient who has undergone ablation for atrial flutter. Left panel shows pacing (PA) from the lateral right atrial wall; the impulse is propagated down the lateral wall of the high right atrium, generating an atrial electrogram (A), to the lateral TV-IVC isthmus region (CS13- 14, CS11-12, CS9-10) where conduction is blocked. The medial aspect of the isthmus is not depolarized until a wavefront of activation comes down the interatrial septum or from the low left atrium; the distal poles of the catheter are therefore depolarized late and in the opposite direction, from the coronary sinus ostium back towards the medial TV-IVC isthmus (CS3-4, CS5-6, CS7-8). Right panel shows pacing from the coronary sinus ostium. In this case, the medial isthmus is depolarized promptly (CS3-4, CS5-6), but conduction is blocked within the isthmus (CS7-8). Thus, activation of the lateral wall of the right atrium is delayed until a wavefront travels up the septum and across the roof of the right atrium. Activation of the proximal poles of the catheter is therefore delayed and occurs from high to low (CS15-16, CS13-14, CS11-12, https://www.uptodate.com/contents/overview-of-catheter-ablation-of-cardiac-arrhythmias/print 34/38 7/5/23, 8:12 AM Overview of catheter ablation of cardiac arrhythmias - UpToDate CS9-10). Patients with bidirectional block across the TC-IVC isthmus have a low rate of atrial flutter recurrence. Graphic 60090 Version 4.0 https://www.uptodate.com/contents/overview-of-catheter-ablation-of-cardiac-arrhythmias/print 35/38 7/5/23, 8:12 AM Overview of catheter ablation of cardiac arrhythmias - UpToDate Complications of invasive cardiac electrophysiology studies Associated with percutaneous catheterization of veins and arteries Pain Adverse drug reaction Infection/abscess at the catheterization site, sepsis Excessive bleeding, hematoma formation Thrombophlebitis Pulmonary thromboembolism Arterial damage, aortic dissection Systemic thromboembolism Transient ischemic attack/stroke Associated with intracardiac catheters and programmed cardiac stimulation Cardiac chamber or coronary sinus perforation Hemopericardium, cardiac tamponade Atrial fibrillation Ventricular tachycardia/ventricular fibrillation Myocardial infarction Right or left bundle branch block Associated with transcatheter ablation Complete heart block Thromboembolism Vascular access problems (bleeding, infection, hematoma, vascular injury) Cardiac trauma (myocardial perforation, tamponade, valvular damage) Coronary artery thrombosis/myocardial infarction Cardiac arrhythmias Pericarditis Pulmonary vein stenosis Phrenic nerve paralysis Radiation skin burns Possible late malignancy Atrioesophageal fistula https://www.uptodate.com/contents/overview-of-catheter-ablation-of-cardiac-arrhythmias/print 36/38 7/5/23, 8:12 AM Overview of catheter ablation of cardiac arrhythmias - UpToDate Death resulting from one of the above complications Graphic 63157 Version 4.0 https://www.uptodate.com/contents/overview-of-catheter-ablation-of-cardiac-arrhythmias/print 37/38 7/5/23, 8:12 AM Overview of catheter ablation of cardiac arrhythmias - UpToDate Contributor Disclosures Samuel L vy, MD No relevant financial relationship(s) with ineligible companies to disclose. N A Mark Estes, III, MD Consultant/Advisory Boards: Boston Scientific [Arrhythmias]; Medtronic [Arrhythmias]. All of the relevant financial relationships listed have been mitigated. Susan B Yeon, MD, JD, FACC No relevant financial relationship(s) with ineligible companies to disclose. Contributor disclosures are reviewed for conflicts of interest by the editorial group. When found, these are addressed by vetting through a multi-level review process, and through requirements for references to be provided to support the content. Appropriately referenced content is required of all authors and must conform to UpToDate standards of evidence. Conflict of interest policy https://www.uptodate.com/contents/overview-of-catheter-ablation-of-cardiac-arrhythmias/print 38/38