Atrial Fibrillation Ablation: Tips for a Successful Procedure

Atrial fibrillation (AF) is the most common form of arrhythmia, occurring in 1–2 percent of the general population, and is associated with high rates of morbidity and mortality. AF ablation has emerged as a safe and effective therapy for certain patients with AF. Since the first ablation procedure, numerous techniques have evolved.^1-11 In this article, we will discuss these techniques in AF ablation, as well as our tips for a successful procedure.

The EP Lab

At Provena St. Joseph Medical Center, we have a dedicated electrophysiology (EP) laboratory, which is equipped with flat detector (Philips Allura Xper FD10, Philips Medical, Bothell, WA), 56-inch LCD screen (Philips FlexVision), Philips EP cockpit, CARTO 3 electroanatomical mapping system (Biosense Webster, Inc., a Johnson & Johnson company, Diamond Bar, CA), LabSystem^™ PRO EP recording system (Bard Electrophysiology Division, Lowell, MA) and Vivid^™i intracardiac echocardiography (GE Healthcare, Waukesha, WI). We perform approximately 150 AF ablation cases annually.

Patient Selection and Preoperative Assessment

Candidates for the procedure are mainly those who have symptomatic AF refractory to medical therapy,¹¹ but we also consider patients who have an intolerance to medication and patients who are involved in occupations or activities that preclude long-term anticoagulation regardless of the presence of symptoms. Another factor in asymptomatic patients is the presence of cardiomyopathy of nonischemic etiology, which is sometimes associated with AF. Finally, patients who desire to avoid taking antiarrhythmics are also considered for ablation.

Pre procedure, a careful history and physical examination are obtained. We also require the patient to undergo extensive education and counseling, so they thoroughly understand the procedure and know what to expect on the day of ablation as well as during the recovery period. A three-dimensional CT scan is performed to assess the left atrium (LA) and pulmonary vein anatomy. In addition, a transesophageal echocardiography is obtained to exclude left atrial thrombus in patients with persistent atrial fibrillation. All patients receive effective oral anticoagulation with Coumadin^® (Bristol-Myers Squibb) (INR 2-3) or dabigatran (Pradaxa^®, Boehringer Ingelheim) 150 mg twice daily. Coumadin is usually continued; however, Pradaxa is discontinued 24 hours before the procedure.

The Procedure

We perform all AF ablations under general anesthesia to maximize patient comfort. A decapolar catheter is inserted through the femoral vein into the coronary sinus. The LA is accessed with two SL1 long sheaths through separate transseptal punctures under intracardiac echocardiography guidance using a phased array catheter. After transseptal puncture, an intravenous bolus of heparin (5000 IU) is administered, followed by infusion or additional boluses to maintain an activated clotting time between 300-400 s.

A circumferential 20-pole diagnostic catheter (Lasso, Biosense Webster, Inc., a Johnson & Johnson company) and Biosense Webster’s 3.5 mm irrigated tip ThermoCool ablation catheter are introduced to the left atrium via the transseptal sheaths.

A real-time, three-dimensional LA map is reconstructed using a non-fluoroscopic navigation system (Carto 3, Biosense Webster, Inc., a Johnson & Johnson company).

The strategy in paroxysmal AF is to isolate the triggers to prevent AF initiation.³ Wide-area circumferential ablation (WACA) or pulmonary vein antrum isolation (PVAI) is performed to isolate the PVs using the irrigated-tip catheter. Radiofrequency energy is delivered with a power of 20-35 W using irrigation rates of 5-30 ml/minute to maintain a temperature lower than 40° C. Both entrance block (with the use of a circular mapping catheter) and exit block (by pacing within the PVs) are confirmed. An isoproterenol challenge test with 5, 10 and 20 mcg/m is performed to ensure complete PV isolation and to exclude other triggers such as the vein of Marshall, superior vena cava, and coronary sinus (CS). Substrate mapping and ablation of complex fractionated atrial electrograms (CFAE) are performed if the tachycardia persists.¹⁰ We recommend employing a waiting period of 30 minutes, then confirming PV block to exclude early reconnection. (Figure 1)

In persistent AF, we follow a stepwise ablation approach with an endpoint of acute termination of AF. WACA or PVAI and complete isolation of all PVs are performed, followed by linear ablation along the roof of the left atrium connecting the superior aspects of the left and right upper PV encircling lesions,¹³ and another linear ablation lesion between the left inferior PV and mitral annulus (mitral isthmus).¹⁴ It is important to confirm bidirectional block across all ablation lines to prevent macroreentrant tachycardia. This can be achieved by the demonstration of a corridor of double potentials along the linear ablation lesions as well as an activation detour when pacing from either side of each ablation line.¹³

Occasionally, ablation of the CS musculature is required to achieve CS-LA disconnection. This is performed along the endocardial aspect of the mitral annulus and completed from within the vessel (epicardial) as required. The ablation catheter is dragged along the endocardium of the inferior left atrium after looping the catheter in such a way as to position it parallel to the coronary sinus catheter. The ablation catheter is gradually withdrawn from the left atrial septal area and ablation is performed along the posterior mitral annulus from a site adjacent to the CS ostium and progressing to the lateral left atrium. The endpoint is elimination or significant reduction of local endocardial electrograms.

CFAE-targeted mapping and ablation are then performed. These areas represent continuous localized reentry or overlap of different wavelets entering that site. They are characterized by short cycle length and heterogeneous temporal and spatial distribution. Endpoints include slowing of fractionated activity, complete elimination of all complex fractionated activity, or acute termination for persistent AF with noninducibility for PAF.¹² (Figure 2)

At the completion of the procedure, before removing the intracardiac echocardiographic catheter, another assessment of the pericardium is performed to look for any developing effusion.

Patients are monitored on telemetry following the procedure, and if atrial fibrillation recurs, we promptly restore sinus rhythm with electrical direct current cardioversion. Antiarrhythmic drugs are often initiated. The following day, we perform a surface echocardiogram to look for any evidence of an effusion, and patients are given Pradaxa. We avoid giving Lovenox^® (sanofi-aventis) for the first 48 hours following the procedure.

At the time of discharge, patients receive detailed instructions concerning antiarrhythmic drug therapy and the anticoagulation regimen. Patients are told to be alert for any symptoms related to post-procedural complications, such as symptoms related to bleeding, pulmonary embolus, or stroke. Information regarding follow up is supplied, and the importance of promptly reporting symptoms is emphasized.

Follow-up appointments are arranged for one week, one month and three months after the procedure. A 12-lead electrocardiogram is performed during each of those visits. We also assess patients for symptoms that may be related to recurrence. If there is no evidence of recurrence seen on the electrocardiogram and patients are having symptoms, prolonged outpatient monitoring with an event monitor is prescribed. If recurrence is seen, direct current cardioversion is performed with continuation of the current antiarrhythmic drug regimen. If recurrence is seen again following cardioversion, we usually change the antiarrhythmic drug and attempt cardioversion after the patient has been on the new regimen for an adequate period of time. If there is no recurrence after three months, we consider discontinuation of antiarrhythmic drug therapy. New published reports advocate waiting for at least six months before discontinuing the antiarrhythmic drug. If recurrence is seen three months after the procedure, we consider the first procedure unsuccessful. Depending on the burden of AF and the patient’s symptoms and experience with AF, another AF ablation procedure or surgical ablation is considered.

Virtually all patients are anticoagulated with either Coumadin or Pradaxa for one month following the procedure. After one month, if the patient remains in sinus rhythm and the CHADS score is less than two, we consider discontinuation of anticoagulation. If the CHADS score is two or above, we often continue anticoagulation therapy even if there is no obvious recurrence. Prolonged monitoring with an event monitor may be used to document a lack of recurrence before discontinuation of anticoagulation when the patient’s CHADS score is elevated. After discontinuation of Coumadin or Pradaxa, we typically switch patients to a regimen of 325 mg aspirin per day.

Tips and Tricks for a Successful Procedure

We consider our first ablation lesion the most important, and we try to resist moving to a new site prematurely as local edema provoked by ablation might prevent delivering an effective lesion if we have to go back into that site again.

Unnecessary ablation lines should be avoided. It is imperative to confirm block across all ablation lines to avoid creating corridors of reentry in order to prevent macroreentrant tachycardia.

Complete pulmonary vein disconnection should be confirmed at completion, and is considered the cornerstone of each procedure. We encourage using either Isuprel or adenosine to confirm bidirectional block.¹⁵

There are many suggested approaches to avoid esophageal thermal injury while ablating on the left atrial posterior wall.¹⁶ We have found that monitoring intraesophageal temperature with a temperature probe to be the most practical method. We also recommend limiting power to a maximum of 25 watts.

References

1. Haissaguerre M, Jais P, Shah DC, et al. Spontaneous initiation of atrial fibrillation by ectopic beats originating in the pulmonary veins. N Engl J Med 1998;339:659–666.
2. Haissaguerre M, Jais P, Shah DC, et al. Right and left atrial radiofrequency catheter therapy of paroxysmal atrial fibrillation. J Cardiovasc Electrophysiol 1996;7:1132–1144.
3. Oral H, Knight BP, Tada H, et al. Pulmonary vein isolation for paroxysmal and persistent atrial fibrillation. Circulation 2002;105:1077–1081.
4. Oral H, Pappone C, Chugh A, et al. Circumferential pulmonary-vein ablation for chronic atrial fibrillation. N Engl J Med 2006;354:934–941.
5. Ouyang F, Antz M, Ernst S, et al. Recovered pulmonary vein conduction as a dominant factor for recurrent atrial tachyarrhythmias after complete circular isolation of the pulmonary veins: Lessons from double Lasso technique. Circulation 2005;111:127–133.
6. Verma A, Natale A. Should atrial fibrillation ablation be considered first-line therapy for some patients? Why atrial fibrillation ablation should be considered first-line therapy for some patients. Circulation 2005;112:1214–1222.
7. Pappone C, Rosanio S, Oreto G, et al. Circumferential radiofrequency ablation of pulmonary vein ostia: A new anatomic approach for curing atrial fibrillation. Circulation 2000;102:2619–2628.
8. Oral H, Chugh A, Lemola K, et al. Noninducibility of atrial fibrillation as an end point of left atrial circumferential ablation for paroxysmal atrial fibrillation: A randomized study. Circulation 2004;110:2797–2801.
9. Mansour M, Ruskin J, Keane D. Efficacy and safety of segmental ostial versus circumferential extra-ostial pulmonary vein isolation for atrial fibrillation. J Cardiovasc Electrophysiol 2004;15:532–537.
10. Nademanee K, McKenzie J, Kosar E, at al. A new approach for catheter ablation of atrial fibrillation: Mapping of the electrophysiologic substrate. J Am Coll Cardiol 2004;43:2044–2053.
11. Calkins H, Brugada J, Packer DL, et al. HRS/EHRA/ECAS expert consensus statement on catheter and surgical ablation of atrial fibrillation: Recommendations for personnel, policy, procedures and follow-up. A report of the Heart Rhythm Society (HRS) Task Force on catheter and surgical ablation of atrial fibrillation. Heart Rhythm 2007;4:816–861.
12. Haissaguerre M, Sanders P, Hocini M, et al. Changes in atrial fibrillation cycle length and inducibility during catheter ablation and their relation to outcome. Circulation 2004;109:3007–3013.
13. Hocini M, Jais P, Sanders P, et al. Techniques, evaluation, and consequences of linear block at the left atrial roof in paroxysmal atrial fibrillation: A prospective randomized study. Circulation 2005;112:3688–3696.
14. Jais P, Hocini M, Hsu LF, et al. Technique and results of linear ablation at the mitral isthmus. Circulation 2004;110:2996–3002.
15. Gula LJ, Massel D, Leong-Sit P, et al. Does adenosine response predict clinical recurrence of atrial fibrillation after pulmonary vein isolation? J Cardiovasc Electrophysiol 2011;22:982–986.
16. Dagres N, Anastasio N. Prevention of atrial-esophageal fistula after catheter ablation of atrial fibrillation. Curr Opin Cardiol 2010 Nov 19 [Epub ahead of print].