REVIEW ARTICLE
Radiofrequency catheter ablation for atrial fibrillation Lauren Dorn, MMS, PA-C; Adeline Kranzburg, MMS, PA-C; Amy Saumell, MMS, PA-C; Tanya Gregory, PhD; Suzanne Reich, PA-C, MPAS
ABSTRACT Antiarrhythmic drugs are the first-line treatment for atrial fibrillation (AF); as a result, catheter ablation usually is not considered until a patient is experiencing symptomatic AF refractory to at least one antiarrhythmic medication or is intolerant to medical therapy. For these patients, catheter ablation is shown to be more effective than medical therapy for controlling AF. This article reviews catheter ablation and its indications. Keywords: atrial fibrillation, radiofrequency catheter ablation, antiarrhythmic, electrophysiology, ectopic, paroxysmal
TREATMENTS FOR ATRIAL FIBRILLATION Antiarrhythmic drug therapy is the first-line treatment for AF.4 Medications such as amiodarone, flecainide, and sotalol may be used to maintain normal sinus Lauren Dorn practices in orthopedic spine surgery at LewisGale Physicians-The Spine Center in Salem, Va. Adeline Kranzburg practices in the medical, surgical, and neurologic ICUs at Wake Forest Baptist Medical Center in Winston-Salem, N.C. Amy Saumell practices dermatology at Judith Crowell, MD, and Associates in Miami, Fla. Tanya Gregory and Suzanne Reich are assistant professors at Wake Forest School of Medicine. The authors have disclosed no potential conflicts of interest, financial or otherwise. DOI: 10.1097/01.JAA.0000464275.36493.2d Copyright © 2015 American Academy of Physician Assistants
40
© KEVIN A. SOMERVILLE / PHOTOTAKE
Atrial fibrillation (AF) occurs secondary to the firing of ectopic foci within the atria of the heart. As many as 94% of ectopic foci responsible for AF originate from the pulmonary veins.1 These foci are often due to input from the autonomic ganglion plexus located in the epicardial fat near the left atrium, which causes changes in depolarization and calcium loading in the left atrium.2 Less commonly, AF may be caused by focal firing in the right and left atria outside of the pulmonary veins. AF is classified as paroxysmal, persistent, or longstanding. Paroxysmal AF is characterized by symptomatic episodes lasting fewer than 7 days. Persistent fibrillation is defined as episodes lasting longer than 7 days, and long-standing AF has been present for more than 12 months.3
FIGURE 1. Radiofrequency energy delivered from the tip of the
catheter permits controlled, minute damage to the selected ectopic area.
rhythm. Rate control therapy keeps patients in AF but works to decrease the rate of ventricular contractions by causing atrioventricular (AV) nodal blockade. The drugs most commonly used for this purpose are nondihydropyridine calcium channel blockers such as verapamil and diltiazem. Digoxin and beta-blockers may also be used for rate control and to increase ventricular contractility.
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Volume 28 • Number 5 • May 2015
Copyright © 2015 American Academy of Physician Assistants
Radiofrequency catheter ablation for atrial fibrillation
Key points Although antiarrhythmic drugs are the first-line treatment for AF, adverse reactions often limit their success. For some symptomatic patients, including those who do not respond to drug therapy, radiofrequency catheter ablation may cure AF. Although serious complications of catheter ablation are rare, the procedure should be performed only at facilities that have cardiothoracic surgery backup.
In several clinical trials, efficacy rates for antiarrhythmic drug therapy have been as low as 8.7% and as high as 58%.5 The adverse reaction profile of these medications limits their success in controlling AF; adverse reactions range from fatigue, bradycardia, and thyroid disorders to hepatic toxicity and QT interval prolongation.6,7 Moreover, because antiarrhythmic drugs are not atrial-specific, they all carry an increased risk of proarrhythmia.8 When patients do not respond to drug therapy, catheter ablation may be considered. This article reviews the indications, complications, and outcomes for this procedure. Other second-line options for the treatment of AF include direct current cardioversion; cryoablation, which uses a balloon catheter to freeze select ectopic pathways; and the Cox maze procedure, an open-heart surgery that involves making small incisions in the atrium to disrupt ectopic electrical circuits.9 Because atrial dysfunction increases the risk for thrombus formation and stroke, patients with AF should also be considered for anticoagulation therapy. WHEN CATHETER ABLATION IS APPROPRIATE The Heart Rhythm Society/European Heart Rhythm Association/European Cardiac Arrhythmia Society (HRS/EHRA/ ECAS) released an expert consensus statement in 2012 outlining the indications for catheter ablation.2 According to the consensus statement, this procedure is appropriate only when patients are symptomatic and should be considered when AF is refractory to antiarrhythmic drug therapy, when patients cannot tolerate drug therapy, or in selected patients before antiarrhythmic drug therapy is used. The procedure is most reasonable for patients experiencing paroxysmal AF episodes but may be considered in those with persistent or long-standing AF.2 Because medications are first-line treatment for AF, catheter ablation is not usually considered until a patient is experiencing symptomatic AF refractory to at least one antiarrhythmic drug or is intolerant to medical therapy.3 For these patients, catheter ablation is more effective than medical therapy for controlling AF.10-12 For patients with compensated heart failure who do not respond to antiarrhythmic therapy, catheter ablation may
help to increase ejection fraction and exercise tolerance.13 The best outcomes for patients with heart failure occur when the heart is structurally normal, with little ventricular hypertrophy or dilation. Patients with structural abnormalities may also benefit from catheter ablation but may be at higher risk for complications during or after the procedure. Because outcomes tend to be best for patients with structurally normal hearts and paroxysmal patterns of AF, catheter ablation has been explored as first-line therapy for this group.14 HRS/EHRA/ECAS provides a Level B recommendation for ablation as first-line therapy and says it can be considered on an individualized patient basis.2 The role of ablation for asymptomatic patients is uncertain. Pregnancy (in which fluoroscopy may not be used) and thrombus in the atria or ventricles are absolute contraindications to catheter ablation. Skin infection over the area of femoral vein entry should be allowed to resolve before the procedure is performed. Relative contraindications to catheter ablation include decompensated heart failure, history of severe bleeding, previous stroke or blood clots, certain structural abnormalities such as pulmonary vein stenosis, and other situations in which the patient is at increased risk for complications during or after the procedure. The expected efficacy and safety of the procedure should be considered in each patient individually. ABOUT THE PROCEDURE Conduct a thorough patient history and physical examination before ablation therapy. Electrocardiography, ambulatory electrocardiography monitoring, and echocardiography may be used to verify AF and evaluate for structural heart disease or concurrent dysrhythmias. Exercise testing may be used if the patient has a history of an exercise-induced dysrhythmia.15 Studies such as radionuclide scintigraphy, cardiac catheterization, and coronary angiography may be performed based on the patient’s symptoms and clinical presentation. Thyroid-stimulating hormone can be measured to rule out hyperthyroidism as a cause of the dysrhythmia.15 Other laboratory tests before the procedure may include a complete blood cell count, complete metabolic panel, urinalysis, pregnancy test, and prothrombin time/international normalized ratio (INR). Finally, obtain a CT or MRI to aid in mapping the cardiac anatomy and pulmonary vein anatomy to provide a model for use during the procedure. Catheter ablation procedures are commonly performed using procedural sedation, but occasionally are performed under general anesthesia. Patients should discontinue all AV nodal blocking agents and antiarrhythmic drugs several days before the procedure. Vital signs are monitored before, during, and after the procedure, which typically lasts several hours. Patients also need anticoagulation with heparin
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REVIEW ARTICLE
during catheter ablation: a therapeutic INR is not considered to indicate adequate anticoagulation. However, patients who are taking warfarin should continue taking the medication uninterrupted.16 Radiofrequency ablation is the most widespread ablation method used. Radiofrequency energy is delivered from the tip of the catheter to a focal area of endocardium, allowing for controlled, minute damage to the selected ectopic area rather than the more widespread and unwanted damage that occurs with the use of previous ablative methods (Figure 1). The catheters are introduced through venous sheaths in the femoral veins and threaded into the right atrium. Transseptal catheterization is often used, which requires placement of a sheath across the interatrial septum so that the ablation catheter may be placed in the left atrium. Fluoroscopy or intracardiac echocardiography may be used throughout the procedure to allow for visualization and correct positioning of the catheter. Programmed electrical stimulation and 3D mapping of the electrical impulses are used to identify the exact mechanism and origin of the
Long-term outcomes for catheter ablation vary according to the type of AF. dysrhythmia. Radiowaves are then sent via the catheter to the areas of endocardium causing the ectopic potentials, and the heat from this energy is used to ablate the endocardium in a linear fashion. These lines are placed strategically to block the propagation of ectopic signals to the AV node. Several techniques are used to isolate the ectopic pathways: pulmonary vein isolation, complex fractionated atrial electrogram, and ablation to other locations of the heart, such as right atrial ablation. • Pulmonary vein isolation creates a linear or circumferential lesion at the meeting of the pulmonary veins and the left atrium, causing electrical isolation of the pulmonary veins and eliminating ectopic triggering from transmitting potentials to the AV node. • Complex fractionated atrial electrogram targets specific areas of the atria where electrograms are shown to fractionate and disperse in several directions. Evidence varies as to whether pulmonary vein isolation is more effective than complex fractionated atrial electrogram, or if both procedures provide equal outcomes. However, these techniques may be more effective when used in conjunction for the treatment of AF.12,17 After the ablation is performed, electrical stimulation is again implemented to ensure the dysrhythmia is no longer active or inducible. 42
When the procedure is over, the sheaths are removed and the patient is observed for several hours while on bed rest to avoid any immediate vascular complications. The patient may be discharged on the same day or may be kept overnight in the hospital for observation. The patient should take high-dose aspirin for 4 to 8 weeks after the procedure to reduce the risk of venous thromboembolism.15 The need for long-term anticoagulation should be evaluated individually, and a CHA2DS2 score (measuring stroke risk in patients with AF) and previous thromboembolic event history should be factored into this decision.2 COMPLICATIONS OF ABLATION THERAPY The overall complication rate for catheter ablation for AF is 4.5% with 0.15% mortality.18 Vascular complications are most common and include hemothorax, hematoma, and arteriovenous fistula. These complications can be prevented by ensuring appropriate access into the femoral vein as well as by achieving adequate hemostasis at the time the sheath is removed. Using ultrasound while obtaining access reduces the potential formation of arteriovenous fistula during sheath entry. To decrease the likelihood of postprocedural bleeding, tell patients to remain supine for several hours following ablation and sheath removal. Less-common complications include phrenic or vagal nerve injury, pulmonary vein stenosis, and AV block. The most serious complications of cardiac ablation include thromboembolic events, cardiac tamponade, and atrioesophageal fistula. Thromboembolic events may occur during the 2 weeks following the ablation procedure; anticoagulation before, during, and after the procedure is essential.19 Cardiac tamponade has a prevalence of about 1% but is the most frequent cause of periprocedural death. The use of intracardiac echocardiography during ablation may reduce the risk of perforation as well as detect any early pericardial effusions. Atrioesophageal fistula is rare but carries a greater than 80% mortality.20 Because the esophagus is close to the left atrium, damage to the esophagus may occur and lead to dysphagia, GI bleeding, and air embolism causing stroke. Although serious complications are uncommon, ablation should be performed only at facilities where cardiothoracic surgical backup is available. Operator experience has emerged as an important predictor of complication risk. An assessment of more than 90,000 procedures found that electrophysiologists performing fewer than 25 catheter ablations annually had complication rates greater than 6%, which are significantly higher than the complication rates of less than 3% for those performing 25 to 50 procedures per year and more than 50 procedures per year.21 SHORT-TERM AND LONG-TERM OUTCOMES Several studies have sought to show the efficacy of catheter ablation compared with antiarrhythmic drug therapy
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Radiofrequency catheter ablation for atrial fibrillation
for the treatment of AF. The SARA study evaluated 146 patients with persistent AF and found that after 12 months of follow-up, 70.4% of patients who underwent catheter ablation remained free of AF episodes compared with 43.7% in the medical therapy group.11 Similarly, a 2013 meta-analysis by Lin and colleagues evaluated eight randomized trials comparing catheter ablation with drug therapy; the authors concluded that the success rate was significantly higher for catheter ablation.12 And a 2006 study by Stabile and colleagues concluded that ablation therapy combined with antiarrhythmic drug therapy was superior to drug therapy alone in patients with AF refractory to drug treatment; 65% of the AF-plus-drug-therapy group experienced no AF episodes in 1 year, compared with only 7% in the control group.22 This last study did not evaluate the efficacy of drug therapy compared to ablation alone. Oral and colleagues published an evaluation of the efficacy of circumferential pulmonary vein ablation in maintaining sinus rhythm in the absence of antiarrhythmic drug therapy. Twelve months after the first circumferential pulmonary vein ablation, 57 of 77 patients were in normal sinus rhythm without antiarrhythmic drug therapy—a 74% success rate.23 Circumferential pulmonary vein ablation had to be repeated in the remaining patients because of either recurrent AF or left atrial flutter. The maintenance of sinus rhythm after circumferential pulmonary vein ablation was attributed to a decrease in the diameter of the left atrium, an improvement in left ventricular ejection fraction, and a reduction in severity of symptoms.23 Finally, a study by Reynolds and colleagues evaluated quality of life after either catheter ablation or antiarrhythmic drug therapy in 167 patients; the authors observed significant improvement at the 3-month followup in seven areas ranging from bodily pain to general health and physical functioning in the patients who had received ablation therapy.10 Long-term outcomes for catheter ablation vary according to the type of AF. Patients with paroxysmal AF have the highest success rates, with some estimates placing them at 80% to 85%.24 Most estimates are lower, however. A meta-analysis by Ganeson and colleagues evaluated the long-term outcomes for more than 6,000 patients at follow-up dates between 28 and 71 months postprocedure and found a 66.6% success rate for paroxysmal AF (range, 58.2% to 74.2%).25 The same meta-analysis found a 51.9% success rate for nonparoxysmal AF (range, 33.8% to 69.5%).25 Cheema and colleagues reported 45% long-term success rates for ablation therapy for nonparoxysmal AF.26 Long-term freedom from atrial dysrhythmia can be achieved with one procedure in some patients, but others will need multiple procedures to achieve this goal. Recurrence is most commonly due to reconnection of the electrical circuit at previously isolated pulmonary veins.2
Predictors of recurrence include persistent AF, valvular AF, left atrial enlargement, operator inexperience, and symptom recurrence within the first 30 days postprocedure.27 Incomplete electrical isolation of all pulmonary veins also is considered to have a significant effect on recurrence rates.26 Some evidence is available about changes in cardiovascular and other health risks after ablation therapy. In 2011, Bunch and colleagues reported on the long-term rates of stroke, death, and dementia in more than 37,000 patients: over a period of 3 years, patients who received ablation for AF had higher incidences of hypertension, heart failure, and valvular disease than patients with AF who did not receive ablation and patients who did not have AF; however, the ablation therapy group had lower incidences of dementia, stroke, and death compared with the other groups.28 Lin and colleagues evaluated 1,262 patients with a CHA2DS2-VASc score of 1 or more: all patients undergoing ablation had a lower incidence of mortality compared with those receiving antiarrhythmic drug therapy; patients with a CHA2DS2-VASc score greater than 2 had lower risks of major adverse cardiovascular events, and those with a CHA2DS2-VASc score of 1 had similar rates of major cardiovascular events as compared to the control group.29 CONCLUSION The increasing prevalence of AF in the US population suggests that further investigation into and use of catheter ablation can help to reduce the symptoms and complications of this disease. Indeed, several clinical trials are evaluating the efficacy of catheter ablation. The CABANA trial is comparing ablation to antiarrhythmic drug therapy, and the EAST trial plans to evaluate how early rhythm control and ablation therapy will work to decrease risk of AF complications.30,31 Both trials plan to finish their data collection in 2017. Catheter ablation is an effective therapeutic strategy for AF, and this procedure may become an increasingly effective modality for improving symptoms and preventing their recurrence. The evidence is promising, but a broader evidence base supported by larger sample sizes is needed to further understand the role of radiofrequency ablation for AF. Patients with paroxysmal AF have received the most benefit with catheter ablation thus far, as reflected in both short-term and long-term studies. More studies are needed to evaluate the long-term efficacy of catheter ablation. Further exploration of catheter ablation as first-line treatment, especially for patients with paroxysmal AF, is needed to possibly reduce the complications and structural changes that come with chronic AF. Greater operator experience is related to success and symptom-free periods for patients undergoing catheter ablation. Success rates are higher at high-volume sites;
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Radiofrequency catheter ablation for atrial fibrillation
thus, proper training and experience are important to electrophysiologists performing this procedure. Finally, although catheter ablation has shown to be more effective in many cases when compared to antiarrhythmic drug therapy, the procedure should be considered on an individualized patient basis and should not be performed until the patient understands the risk of complications and what the procedure and followup entail. The patient should be the one to ultimately decide between medical and surgical management for episodes of AF. JAAPA REFERENCES 1. Chen SA, Hsieh MH, Tai CT, et al. Initiation of atrial fibrillation by ectopic beats originating from the pulmonary veins: electrophysiological characteristics, pharmacological responses, and effects of radiofrequency ablation. Circulation. 1999;100(18): 1879-1886. 2. Calkins H, Kuck KH, Cappato R, et al. 2012 HRS/EHRA/ECAS expert consensus statement on catheter and surgical ablation of atrial fibrillation: recommendations for patient selection, procedural techniques, patient management and follow-up, definitions, endpoints, and research trial design. Europace. 2012;14(4):528-606. 3. Thomas SP, Sanders P. Catheter ablation for atrial fibrillation. Heart Lung Circ. 2012;21(6-7):395-401. 4. Fuster V, Rydén LE, Asinger RW, et al. ACC/AHA/ESC guidelines for the management of patients with atrial fibrillation: executive summary. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the European Society of Cardiology Committee for Practice Guidelines and Policy Conferences (Committee to Develop Guidelines for the Management of Patients With Atrial Fibrillation) developed in collaboration with the North American Society of Pacing and Electrophysiology. Circulation. 2001;104(17):2118-2150. 5. Viles-Gonzalez JF, Fuster V, Halperin J, et al. Rhythm control for management of patients with atrial fibrillation: balancing the use of antiarrhythmic drugs and catheter ablation. Clin Cardiol. 2011;34(1):23-29. 6. Zimetbaum P. Amiodarone for atrial fibrillation. N Engl J Med. 2007;356(9):935-941. 7. Singh BN, Singh SN, Reda DJ, et al., for the Sotalol Amiodarone Atrial Fibrillation Efficacy Trial (SAFE-T) Investigators. Amiodarone versus sotalol for atrial fibrillation. N Engl J Med. 2005; 352(18):1861-1872. 8. Woods CE, Olgin J. Atrial fibrillation therapy now and in the future: drugs, biologicals, and ablation. Circ Res. 2014;114(9): 1532-1546. 9. Cox JL, Schuessler RB, D’Agostino HJ Jr, et al. The surgical treatment of atrial fibrillation. III. Development of a definitive surgical procedure. J Thorac Cardiovasc Surg. 1991;101(4): 569-583. 10. Reynolds MR, Walczak J, White SA, et al. Improvements in symptoms and quality of life in patients with paroxysmal atrial fibrillation treated with radiofrequency catheter ablation versus antiarrhythmic drugs. Circ Cardiovasc Qual Outcomes. 2010; 3(6):615-623. 11. Mont L, Bisbal F, Hernández-Madrid A, et al. Catheter ablation vs. antiarrhythmic drug treatment of persistent atrial fibrillation: a multicentre, randomized, controlled trial (SARA study). Eur Heart J. 2013;10:1093-1100. 12. Lin G, Lu H, Shen Y, et al. Meta-analysis of the therapeutic of various methods for the treatment of chronic atrial fibrillation. Exp Ther Med. 2013;6(2):489-496.
13. Hsu L, Jais P, Sanders P, et al. Catheter ablation for atrial fibrillation in congestive heart failure. N Engl J Med. 2004;351: 2373-2383. 14. Wazni OM, Marrouche NF, Martin DO, et al. Radiofrequency ablation vs antiarrhythmic drugs as first-line treatment of symptomatic atrial fibrillation: a randomized trial. JAMA. 2005;293 (21):2634-2640. 15. Ganz LI. Catheter ablation of cardiac arrhythmias: overview and technical aspects. http://www.UpToDate.com. 16. Santangeli P, Di Biase L, Burkhardt JD, Natale A. Catheter ablation of atrial fibrillation under therapeutic warfarin should be adopted worldwide: let’s stop waiting for Godot! J Cardiovasc Electrophysiol. 2013:24(5):516-518. 17. Parkash R, Tang AS, Sapp JL, Wells G. Approach to the catheter ablation technique of paroxysmal and persistent atrial fibrillation: a meta-analysis of the randomized controlled trials. J Cardiovasc Electrophysiol. 2011;22(7):729-738. 18. Cappato R, Calkins H, Chen SA, et al. Updated worldwide survey on the methods, efficacy, and safety of catheter ablation for human atrial fibrillation. Circ Arrhythm Electrophysiol. 2010; 3(1):32-38. 19. Cappato R, Calkins H, Chen SA, et al. Prevalence and causes of fatal outcome in catheter ablation of atrial fibrillation. J Am Coll Cardiol. 2009;53(19):1798-1803. 20. Aldhoon B, Wichterle D, Peichl P, et al. Complications of catheter ablation for atrial fibrillation in a high-volume centre with the use of intracardiac echocardiography. Europace. 2013;15(1):24-32. 21. Deshmukh A, Patel NJ, Pant S, et al. 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(19):2104-2112. 22. Stabile G, Bertaglia E, Senatore G, et al. Catheter ablation treatment in patients with drug-refractory atrial fibrillation: a prospective, multi-centre, randomized, controlled study (Catheter Ablation for the Cure of Atrial Fibrillation Study). Eur Heart J. 2006;27(2):216-221. 23. Oral H, Pappone C, Chugh A, et al. Circumferential pulmonaryvein ablation for chronic atrial fibrillation. N Engl J Med. 2006; 354(9):934-941. 24. Callahan TD 4th, Natale A. Catheter ablation of atrial fibrillation. Med Clin North Am. 2008;92(1):179-201. 25. Ganesan AN, Shipp NJ, Brooks AG, et al. Long-term outcomes of catheter ablation of atrial fibrillation: a systematic review and meta-analysis. J Am Heart Assoc. 2013;2(2):e004549. 26. Cheema A, Dong J, Dalal D, et al. Long-term safety and efficacy of circumferential ablation with pulmonary vein isolation. J Cardiovasc Electrophysiol. 2006;17(10):1080-1085. 27. D’Ascenzo F, Corleto A, Biondi-Zoccai G, et al. Which are the most reliable predictors of recurrence of atrial fibrillation after transcatheter ablation? A meta-analysis. Int J Cardiol. 2013;167 (5):1984-1989. 28. Bunch TJ, Crandall BG, Weiss JP, et al. Patients treated with catheter ablation for atrial fibrillation have long-term rates of death, stroke, and dementia similar to patients without atrial fibrillation. J Cardiovasc Electrophysiol. 2011;22(8):839-845. 29. Lin YJ, Chao TF, Tsao HM, et al. Successful catheter ablation reduces the risk of cardiovascular events in atrial fibrillation patients with CHA2DS2-VASc risk score of 1 and higher. Europace. 2013;15(5):676-684. 30. Catheter ablation vs anti-arrhythmic drug therapy for atrial fibrillation trial (CABANA). http://clinicaltrials.gov/show/ NCT00911508. Accessed February 17, 2015. 31. The German Atrial Fibrillation Network. Early treatment of atrial fibrillation for stroke prevention trial (EAST). http://clinicaltrials. gov/show/NCT01288352. Accessed February 17, 2015.
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Radiofrequency catheter ablation for atrial fibrillation Lauren Dorn, MMS, PA-C; Adeline Kranzburg, MMS, PA-C; Amy Saumell, MMS, PA-C; Tanya Gregory, PhD; Suzanne Reich, PA-C, MPAS
ABSTRACT Antiarrhythmic drugs are the first-line treatment for atrial fibrillation (AF); as a result, catheter ablation usually is not considered until a patient is experiencing symptomatic AF refractory to at least one antiarrhythmic medication or is intolerant to medical therapy. For these patients, catheter ablation is shown to be more effective than medical therapy for controlling AF. This article reviews catheter ablation and its indications. Keywords: atrial fibrillation, radiofrequency catheter ablation, antiarrhythmic, electrophysiology, ectopic, paroxysmal
TREATMENTS FOR ATRIAL FIBRILLATION Antiarrhythmic drug therapy is the first-line treatment for AF.4 Medications such as amiodarone, flecainide, and sotalol may be used to maintain normal sinus Lauren Dorn practices in orthopedic spine surgery at LewisGale Physicians-The Spine Center in Salem, Va. Adeline Kranzburg practices in the medical, surgical, and neurologic ICUs at Wake Forest Baptist Medical Center in Winston-Salem, N.C. Amy Saumell practices dermatology at Judith Crowell, MD, and Associates in Miami, Fla. Tanya Gregory and Suzanne Reich are assistant professors at Wake Forest School of Medicine. The authors have disclosed no potential conflicts of interest, financial or otherwise. DOI: 10.1097/01.JAA.0000464275.36493.2d Copyright © 2015 American Academy of Physician Assistants
40
© KEVIN A. SOMERVILLE / PHOTOTAKE
Atrial fibrillation (AF) occurs secondary to the firing of ectopic foci within the atria of the heart. As many as 94% of ectopic foci responsible for AF originate from the pulmonary veins.1 These foci are often due to input from the autonomic ganglion plexus located in the epicardial fat near the left atrium, which causes changes in depolarization and calcium loading in the left atrium.2 Less commonly, AF may be caused by focal firing in the right and left atria outside of the pulmonary veins. AF is classified as paroxysmal, persistent, or longstanding. Paroxysmal AF is characterized by symptomatic episodes lasting fewer than 7 days. Persistent fibrillation is defined as episodes lasting longer than 7 days, and long-standing AF has been present for more than 12 months.3
FIGURE 1. Radiofrequency energy delivered from the tip of the
catheter permits controlled, minute damage to the selected ectopic area.
rhythm. Rate control therapy keeps patients in AF but works to decrease the rate of ventricular contractions by causing atrioventricular (AV) nodal blockade. The drugs most commonly used for this purpose are nondihydropyridine calcium channel blockers such as verapamil and diltiazem. Digoxin and beta-blockers may also be used for rate control and to increase ventricular contractility.
www.JAAPA.com
Volume 28 • Number 5 • May 2015
Copyright © 2015 American Academy of Physician Assistants
Radiofrequency catheter ablation for atrial fibrillation
Key points Although antiarrhythmic drugs are the first-line treatment for AF, adverse reactions often limit their success. For some symptomatic patients, including those who do not respond to drug therapy, radiofrequency catheter ablation may cure AF. Although serious complications of catheter ablation are rare, the procedure should be performed only at facilities that have cardiothoracic surgery backup.
In several clinical trials, efficacy rates for antiarrhythmic drug therapy have been as low as 8.7% and as high as 58%.5 The adverse reaction profile of these medications limits their success in controlling AF; adverse reactions range from fatigue, bradycardia, and thyroid disorders to hepatic toxicity and QT interval prolongation.6,7 Moreover, because antiarrhythmic drugs are not atrial-specific, they all carry an increased risk of proarrhythmia.8 When patients do not respond to drug therapy, catheter ablation may be considered. This article reviews the indications, complications, and outcomes for this procedure. Other second-line options for the treatment of AF include direct current cardioversion; cryoablation, which uses a balloon catheter to freeze select ectopic pathways; and the Cox maze procedure, an open-heart surgery that involves making small incisions in the atrium to disrupt ectopic electrical circuits.9 Because atrial dysfunction increases the risk for thrombus formation and stroke, patients with AF should also be considered for anticoagulation therapy. WHEN CATHETER ABLATION IS APPROPRIATE The Heart Rhythm Society/European Heart Rhythm Association/European Cardiac Arrhythmia Society (HRS/EHRA/ ECAS) released an expert consensus statement in 2012 outlining the indications for catheter ablation.2 According to the consensus statement, this procedure is appropriate only when patients are symptomatic and should be considered when AF is refractory to antiarrhythmic drug therapy, when patients cannot tolerate drug therapy, or in selected patients before antiarrhythmic drug therapy is used. The procedure is most reasonable for patients experiencing paroxysmal AF episodes but may be considered in those with persistent or long-standing AF.2 Because medications are first-line treatment for AF, catheter ablation is not usually considered until a patient is experiencing symptomatic AF refractory to at least one antiarrhythmic drug or is intolerant to medical therapy.3 For these patients, catheter ablation is more effective than medical therapy for controlling AF.10-12 For patients with compensated heart failure who do not respond to antiarrhythmic therapy, catheter ablation may
help to increase ejection fraction and exercise tolerance.13 The best outcomes for patients with heart failure occur when the heart is structurally normal, with little ventricular hypertrophy or dilation. Patients with structural abnormalities may also benefit from catheter ablation but may be at higher risk for complications during or after the procedure. Because outcomes tend to be best for patients with structurally normal hearts and paroxysmal patterns of AF, catheter ablation has been explored as first-line therapy for this group.14 HRS/EHRA/ECAS provides a Level B recommendation for ablation as first-line therapy and says it can be considered on an individualized patient basis.2 The role of ablation for asymptomatic patients is uncertain. Pregnancy (in which fluoroscopy may not be used) and thrombus in the atria or ventricles are absolute contraindications to catheter ablation. Skin infection over the area of femoral vein entry should be allowed to resolve before the procedure is performed. Relative contraindications to catheter ablation include decompensated heart failure, history of severe bleeding, previous stroke or blood clots, certain structural abnormalities such as pulmonary vein stenosis, and other situations in which the patient is at increased risk for complications during or after the procedure. The expected efficacy and safety of the procedure should be considered in each patient individually. ABOUT THE PROCEDURE Conduct a thorough patient history and physical examination before ablation therapy. Electrocardiography, ambulatory electrocardiography monitoring, and echocardiography may be used to verify AF and evaluate for structural heart disease or concurrent dysrhythmias. Exercise testing may be used if the patient has a history of an exercise-induced dysrhythmia.15 Studies such as radionuclide scintigraphy, cardiac catheterization, and coronary angiography may be performed based on the patient’s symptoms and clinical presentation. Thyroid-stimulating hormone can be measured to rule out hyperthyroidism as a cause of the dysrhythmia.15 Other laboratory tests before the procedure may include a complete blood cell count, complete metabolic panel, urinalysis, pregnancy test, and prothrombin time/international normalized ratio (INR). Finally, obtain a CT or MRI to aid in mapping the cardiac anatomy and pulmonary vein anatomy to provide a model for use during the procedure. Catheter ablation procedures are commonly performed using procedural sedation, but occasionally are performed under general anesthesia. Patients should discontinue all AV nodal blocking agents and antiarrhythmic drugs several days before the procedure. Vital signs are monitored before, during, and after the procedure, which typically lasts several hours. Patients also need anticoagulation with heparin
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REVIEW ARTICLE
during catheter ablation: a therapeutic INR is not considered to indicate adequate anticoagulation. However, patients who are taking warfarin should continue taking the medication uninterrupted.16 Radiofrequency ablation is the most widespread ablation method used. Radiofrequency energy is delivered from the tip of the catheter to a focal area of endocardium, allowing for controlled, minute damage to the selected ectopic area rather than the more widespread and unwanted damage that occurs with the use of previous ablative methods (Figure 1). The catheters are introduced through venous sheaths in the femoral veins and threaded into the right atrium. Transseptal catheterization is often used, which requires placement of a sheath across the interatrial septum so that the ablation catheter may be placed in the left atrium. Fluoroscopy or intracardiac echocardiography may be used throughout the procedure to allow for visualization and correct positioning of the catheter. Programmed electrical stimulation and 3D mapping of the electrical impulses are used to identify the exact mechanism and origin of the
Long-term outcomes for catheter ablation vary according to the type of AF. dysrhythmia. Radiowaves are then sent via the catheter to the areas of endocardium causing the ectopic potentials, and the heat from this energy is used to ablate the endocardium in a linear fashion. These lines are placed strategically to block the propagation of ectopic signals to the AV node. Several techniques are used to isolate the ectopic pathways: pulmonary vein isolation, complex fractionated atrial electrogram, and ablation to other locations of the heart, such as right atrial ablation. • Pulmonary vein isolation creates a linear or circumferential lesion at the meeting of the pulmonary veins and the left atrium, causing electrical isolation of the pulmonary veins and eliminating ectopic triggering from transmitting potentials to the AV node. • Complex fractionated atrial electrogram targets specific areas of the atria where electrograms are shown to fractionate and disperse in several directions. Evidence varies as to whether pulmonary vein isolation is more effective than complex fractionated atrial electrogram, or if both procedures provide equal outcomes. However, these techniques may be more effective when used in conjunction for the treatment of AF.12,17 After the ablation is performed, electrical stimulation is again implemented to ensure the dysrhythmia is no longer active or inducible. 42
When the procedure is over, the sheaths are removed and the patient is observed for several hours while on bed rest to avoid any immediate vascular complications. The patient may be discharged on the same day or may be kept overnight in the hospital for observation. The patient should take high-dose aspirin for 4 to 8 weeks after the procedure to reduce the risk of venous thromboembolism.15 The need for long-term anticoagulation should be evaluated individually, and a CHA2DS2 score (measuring stroke risk in patients with AF) and previous thromboembolic event history should be factored into this decision.2 COMPLICATIONS OF ABLATION THERAPY The overall complication rate for catheter ablation for AF is 4.5% with 0.15% mortality.18 Vascular complications are most common and include hemothorax, hematoma, and arteriovenous fistula. These complications can be prevented by ensuring appropriate access into the femoral vein as well as by achieving adequate hemostasis at the time the sheath is removed. Using ultrasound while obtaining access reduces the potential formation of arteriovenous fistula during sheath entry. To decrease the likelihood of postprocedural bleeding, tell patients to remain supine for several hours following ablation and sheath removal. Less-common complications include phrenic or vagal nerve injury, pulmonary vein stenosis, and AV block. The most serious complications of cardiac ablation include thromboembolic events, cardiac tamponade, and atrioesophageal fistula. Thromboembolic events may occur during the 2 weeks following the ablation procedure; anticoagulation before, during, and after the procedure is essential.19 Cardiac tamponade has a prevalence of about 1% but is the most frequent cause of periprocedural death. The use of intracardiac echocardiography during ablation may reduce the risk of perforation as well as detect any early pericardial effusions. Atrioesophageal fistula is rare but carries a greater than 80% mortality.20 Because the esophagus is close to the left atrium, damage to the esophagus may occur and lead to dysphagia, GI bleeding, and air embolism causing stroke. Although serious complications are uncommon, ablation should be performed only at facilities where cardiothoracic surgical backup is available. Operator experience has emerged as an important predictor of complication risk. An assessment of more than 90,000 procedures found that electrophysiologists performing fewer than 25 catheter ablations annually had complication rates greater than 6%, which are significantly higher than the complication rates of less than 3% for those performing 25 to 50 procedures per year and more than 50 procedures per year.21 SHORT-TERM AND LONG-TERM OUTCOMES Several studies have sought to show the efficacy of catheter ablation compared with antiarrhythmic drug therapy
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Radiofrequency catheter ablation for atrial fibrillation
for the treatment of AF. The SARA study evaluated 146 patients with persistent AF and found that after 12 months of follow-up, 70.4% of patients who underwent catheter ablation remained free of AF episodes compared with 43.7% in the medical therapy group.11 Similarly, a 2013 meta-analysis by Lin and colleagues evaluated eight randomized trials comparing catheter ablation with drug therapy; the authors concluded that the success rate was significantly higher for catheter ablation.12 And a 2006 study by Stabile and colleagues concluded that ablation therapy combined with antiarrhythmic drug therapy was superior to drug therapy alone in patients with AF refractory to drug treatment; 65% of the AF-plus-drug-therapy group experienced no AF episodes in 1 year, compared with only 7% in the control group.22 This last study did not evaluate the efficacy of drug therapy compared to ablation alone. Oral and colleagues published an evaluation of the efficacy of circumferential pulmonary vein ablation in maintaining sinus rhythm in the absence of antiarrhythmic drug therapy. Twelve months after the first circumferential pulmonary vein ablation, 57 of 77 patients were in normal sinus rhythm without antiarrhythmic drug therapy—a 74% success rate.23 Circumferential pulmonary vein ablation had to be repeated in the remaining patients because of either recurrent AF or left atrial flutter. The maintenance of sinus rhythm after circumferential pulmonary vein ablation was attributed to a decrease in the diameter of the left atrium, an improvement in left ventricular ejection fraction, and a reduction in severity of symptoms.23 Finally, a study by Reynolds and colleagues evaluated quality of life after either catheter ablation or antiarrhythmic drug therapy in 167 patients; the authors observed significant improvement at the 3-month followup in seven areas ranging from bodily pain to general health and physical functioning in the patients who had received ablation therapy.10 Long-term outcomes for catheter ablation vary according to the type of AF. Patients with paroxysmal AF have the highest success rates, with some estimates placing them at 80% to 85%.24 Most estimates are lower, however. A meta-analysis by Ganeson and colleagues evaluated the long-term outcomes for more than 6,000 patients at follow-up dates between 28 and 71 months postprocedure and found a 66.6% success rate for paroxysmal AF (range, 58.2% to 74.2%).25 The same meta-analysis found a 51.9% success rate for nonparoxysmal AF (range, 33.8% to 69.5%).25 Cheema and colleagues reported 45% long-term success rates for ablation therapy for nonparoxysmal AF.26 Long-term freedom from atrial dysrhythmia can be achieved with one procedure in some patients, but others will need multiple procedures to achieve this goal. Recurrence is most commonly due to reconnection of the electrical circuit at previously isolated pulmonary veins.2
Predictors of recurrence include persistent AF, valvular AF, left atrial enlargement, operator inexperience, and symptom recurrence within the first 30 days postprocedure.27 Incomplete electrical isolation of all pulmonary veins also is considered to have a significant effect on recurrence rates.26 Some evidence is available about changes in cardiovascular and other health risks after ablation therapy. In 2011, Bunch and colleagues reported on the long-term rates of stroke, death, and dementia in more than 37,000 patients: over a period of 3 years, patients who received ablation for AF had higher incidences of hypertension, heart failure, and valvular disease than patients with AF who did not receive ablation and patients who did not have AF; however, the ablation therapy group had lower incidences of dementia, stroke, and death compared with the other groups.28 Lin and colleagues evaluated 1,262 patients with a CHA2DS2-VASc score of 1 or more: all patients undergoing ablation had a lower incidence of mortality compared with those receiving antiarrhythmic drug therapy; patients with a CHA2DS2-VASc score greater than 2 had lower risks of major adverse cardiovascular events, and those with a CHA2DS2-VASc score of 1 had similar rates of major cardiovascular events as compared to the control group.29 CONCLUSION The increasing prevalence of AF in the US population suggests that further investigation into and use of catheter ablation can help to reduce the symptoms and complications of this disease. Indeed, several clinical trials are evaluating the efficacy of catheter ablation. The CABANA trial is comparing ablation to antiarrhythmic drug therapy, and the EAST trial plans to evaluate how early rhythm control and ablation therapy will work to decrease risk of AF complications.30,31 Both trials plan to finish their data collection in 2017. Catheter ablation is an effective therapeutic strategy for AF, and this procedure may become an increasingly effective modality for improving symptoms and preventing their recurrence. The evidence is promising, but a broader evidence base supported by larger sample sizes is needed to further understand the role of radiofrequency ablation for AF. Patients with paroxysmal AF have received the most benefit with catheter ablation thus far, as reflected in both short-term and long-term studies. More studies are needed to evaluate the long-term efficacy of catheter ablation. Further exploration of catheter ablation as first-line treatment, especially for patients with paroxysmal AF, is needed to possibly reduce the complications and structural changes that come with chronic AF. Greater operator experience is related to success and symptom-free periods for patients undergoing catheter ablation. Success rates are higher at high-volume sites;
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Radiofrequency catheter ablation for atrial fibrillation
thus, proper training and experience are important to electrophysiologists performing this procedure. Finally, although catheter ablation has shown to be more effective in many cases when compared to antiarrhythmic drug therapy, the procedure should be considered on an individualized patient basis and should not be performed until the patient understands the risk of complications and what the procedure and followup entail. The patient should be the one to ultimately decide between medical and surgical management for episodes of AF. JAAPA REFERENCES 1. Chen SA, Hsieh MH, Tai CT, et al. Initiation of atrial fibrillation by ectopic beats originating from the pulmonary veins: electrophysiological characteristics, pharmacological responses, and effects of radiofrequency ablation. Circulation. 1999;100(18): 1879-1886. 2. Calkins H, Kuck KH, Cappato R, et al. 2012 HRS/EHRA/ECAS expert consensus statement on catheter and surgical ablation of atrial fibrillation: recommendations for patient selection, procedural techniques, patient management and follow-up, definitions, endpoints, and research trial design. Europace. 2012;14(4):528-606. 3. Thomas SP, Sanders P. Catheter ablation for atrial fibrillation. Heart Lung Circ. 2012;21(6-7):395-401. 4. Fuster V, Rydén LE, Asinger RW, et al. ACC/AHA/ESC guidelines for the management of patients with atrial fibrillation: executive summary. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines and the European Society of Cardiology Committee for Practice Guidelines and Policy Conferences (Committee to Develop Guidelines for the Management of Patients With Atrial Fibrillation) developed in collaboration with the North American Society of Pacing and Electrophysiology. Circulation. 2001;104(17):2118-2150. 5. Viles-Gonzalez JF, Fuster V, Halperin J, et al. Rhythm control for management of patients with atrial fibrillation: balancing the use of antiarrhythmic drugs and catheter ablation. Clin Cardiol. 2011;34(1):23-29. 6. Zimetbaum P. Amiodarone for atrial fibrillation. N Engl J Med. 2007;356(9):935-941. 7. Singh BN, Singh SN, Reda DJ, et al., for the Sotalol Amiodarone Atrial Fibrillation Efficacy Trial (SAFE-T) Investigators. Amiodarone versus sotalol for atrial fibrillation. N Engl J Med. 2005; 352(18):1861-1872. 8. Woods CE, Olgin J. Atrial fibrillation therapy now and in the future: drugs, biologicals, and ablation. Circ Res. 2014;114(9): 1532-1546. 9. Cox JL, Schuessler RB, D’Agostino HJ Jr, et al. The surgical treatment of atrial fibrillation. III. Development of a definitive surgical procedure. J Thorac Cardiovasc Surg. 1991;101(4): 569-583. 10. Reynolds MR, Walczak J, White SA, et al. Improvements in symptoms and quality of life in patients with paroxysmal atrial fibrillation treated with radiofrequency catheter ablation versus antiarrhythmic drugs. Circ Cardiovasc Qual Outcomes. 2010; 3(6):615-623. 11. Mont L, Bisbal F, Hernández-Madrid A, et al. Catheter ablation vs. antiarrhythmic drug treatment of persistent atrial fibrillation: a multicentre, randomized, controlled trial (SARA study). Eur Heart J. 2013;10:1093-1100. 12. Lin G, Lu H, Shen Y, et al. Meta-analysis of the therapeutic of various methods for the treatment of chronic atrial fibrillation. Exp Ther Med. 2013;6(2):489-496.
13. Hsu L, Jais P, Sanders P, et al. Catheter ablation for atrial fibrillation in congestive heart failure. N Engl J Med. 2004;351: 2373-2383. 14. Wazni OM, Marrouche NF, Martin DO, et al. Radiofrequency ablation vs antiarrhythmic drugs as first-line treatment of symptomatic atrial fibrillation: a randomized trial. JAMA. 2005;293 (21):2634-2640. 15. Ganz LI. Catheter ablation of cardiac arrhythmias: overview and technical aspects. http://www.UpToDate.com. 16. Santangeli P, Di Biase L, Burkhardt JD, Natale A. Catheter ablation of atrial fibrillation under therapeutic warfarin should be adopted worldwide: let’s stop waiting for Godot! J Cardiovasc Electrophysiol. 2013:24(5):516-518. 17. Parkash R, Tang AS, Sapp JL, Wells G. Approach to the catheter ablation technique of paroxysmal and persistent atrial fibrillation: a meta-analysis of the randomized controlled trials. J Cardiovasc Electrophysiol. 2011;22(7):729-738. 18. Cappato R, Calkins H, Chen SA, et al. Updated worldwide survey on the methods, efficacy, and safety of catheter ablation for human atrial fibrillation. Circ Arrhythm Electrophysiol. 2010; 3(1):32-38. 19. Cappato R, Calkins H, Chen SA, et al. Prevalence and causes of fatal outcome in catheter ablation of atrial fibrillation. J Am Coll Cardiol. 2009;53(19):1798-1803. 20. Aldhoon B, Wichterle D, Peichl P, et al. Complications of catheter ablation for atrial fibrillation in a high-volume centre with the use of intracardiac echocardiography. Europace. 2013;15(1):24-32. 21. Deshmukh A, Patel NJ, Pant S, et al. 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(19):2104-2112. 22. Stabile G, Bertaglia E, Senatore G, et al. Catheter ablation treatment in patients with drug-refractory atrial fibrillation: a prospective, multi-centre, randomized, controlled study (Catheter Ablation for the Cure of Atrial Fibrillation Study). Eur Heart J. 2006;27(2):216-221. 23. Oral H, Pappone C, Chugh A, et al. Circumferential pulmonaryvein ablation for chronic atrial fibrillation. N Engl J Med. 2006; 354(9):934-941. 24. Callahan TD 4th, Natale A. Catheter ablation of atrial fibrillation. Med Clin North Am. 2008;92(1):179-201. 25. Ganesan AN, Shipp NJ, Brooks AG, et al. Long-term outcomes of catheter ablation of atrial fibrillation: a systematic review and meta-analysis. J Am Heart Assoc. 2013;2(2):e004549. 26. Cheema A, Dong J, Dalal D, et al. Long-term safety and efficacy of circumferential ablation with pulmonary vein isolation. J Cardiovasc Electrophysiol. 2006;17(10):1080-1085. 27. D’Ascenzo F, Corleto A, Biondi-Zoccai G, et al. Which are the most reliable predictors of recurrence of atrial fibrillation after transcatheter ablation? A meta-analysis. Int J Cardiol. 2013;167 (5):1984-1989. 28. Bunch TJ, Crandall BG, Weiss JP, et al. Patients treated with catheter ablation for atrial fibrillation have long-term rates of death, stroke, and dementia similar to patients without atrial fibrillation. J Cardiovasc Electrophysiol. 2011;22(8):839-845. 29. Lin YJ, Chao TF, Tsao HM, et al. Successful catheter ablation reduces the risk of cardiovascular events in atrial fibrillation patients with CHA2DS2-VASc risk score of 1 and higher. Europace. 2013;15(5):676-684. 30. Catheter ablation vs anti-arrhythmic drug therapy for atrial fibrillation trial (CABANA). http://clinicaltrials.gov/show/ NCT00911508. Accessed February 17, 2015. 31. The German Atrial Fibrillation Network. Early treatment of atrial fibrillation for stroke prevention trial (EAST). http://clinicaltrials. gov/show/NCT01288352. Accessed February 17, 2015.
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