Catheter Ablation in the Treatment of Atrial Fibrillation

Atrial Fibrillation First described in 1903 by Hering Most common sustained arrhythmia The irregularity and inequality of heart rhythm associated with atrial fibrillation was first described by Dr. Hering in 1903. Atrial fibrillation is by far the most common sustained arrhythmia diagnosed and treated by physicians. It may be either paroxysmal or chronic. Paroxysms may be brief or lengthy, frequent or infrequent; they may be benign or result in marked symptoms. 1

Atrial fibrillation accounts for 1/3 of all patient discharges with arrhythmia as principal diagnosis 6% PSVT 6% PVCs 18% Unspecified 4% Atrial Flutter 9% SSS 34% Atrial Fibrillation 8% Conduction Disease 10% VT 3% SCD 2% VF Baily D. J Am Coll Cardiol. 1992;19(3):41A.

Atrial Fibrillation What is Atrial Fibrillation? Chaotic circular impulses in the atria Several reentrant circuits moving simultaneously Atrial rates 300 to 600 beats per minute Ventricular rates regulated by the AV node Irregularly irregular due to partial depolarization of AV node Results in loss of AV synchrony 20% to 30% decrease in cardiac output

Incidence and Prevalence Prevalence increases with age 4.8 % in the 70-79 age group Increases to 8.8% in the 80-89 age group During the next 7-8 years, the number of people over the age of 80 is expected to quadruple

Atrial Fibrillation Demographics by Age U.S. population x 1000 Population with AF x 1000 30,000 20,000 10,000 Population with atrial fibrillation 500 400 300 200 100 U.S. population <5 5- 9 10- 14 15- 19 20- 24 25- 29 30- 34 35- 39 40- 44 45- 49 50- 54 55- 59 60- 64 65- 69 70- 74 75- 79 80- 84 85- 89 90- 94 >95 Age, yr Adapted from Feinberg WM. Arch Intern Med. 1995;155:469-473.

Stages of Atrial Fibrillation Paroxysmal Persistent Permanent

Stages of Atrial Fibrillation Paroxysmal (23% of AF population) Self limiting Spontaneous conversion to sinus rhythm within 24 hrs after onset is common Once the duration exceeds 24 hrs, the likelihood of conversion decreases After one week of persistent arrhythmia, spontaneous conversion is rare 30% of these patients develop “Persistent” AF

Stages of Atrial Fibrillation Persistent (38% of AF population) Requires intervention to restore normal rhythm Cardioversion Electrical or Chemical (drugs) Can lead to electrophysical and structural changes in the myocardium (remodeling) that can lead to “Permanent” AF AF with duration of greater than 7 days rarely spontaneously converts

Stages of Atrial Fibrillation Permanent (39% of AF population) Unable to convert Electrical or Chemical (drugs)

Mechanisms of AF Theories of the mechanism of AF involve 2 main processes: - Enhanced automaticity in one or several rapidly depolarizing foci - Reentry involving one or more circuits

Mechanisms Contributing to AF

Mechanisms of AF Rapidly firing atrial foci, located in one or several pulmonary veins (PVs), can initiate AF in susceptible patients Foci also can occur in RA and infrequently in the superior vena cava or coronary sinus

Pulmonary Vein Myocardial Sleeves

Factors Involved in the Pathogenesis of AF Studies in man have shown that increased inhomogeneity of refractory periods and conduction velocity is present in AF patients. Structural changes in atrial tissue may be one of the underlying factors for dispersion of refractoriness in AF. Other factors involved in the induction or maintenance of AF include premature beats, the interaction with the autonomic nervous system, atrial stretch, anisotropic conduction, and the aging process, vein of Marshall……….

Mechanisms contributing to AF

Atrial Fibrillation: Clinical Problems Embolism and stroke (presumably due to LA clot) Acute hospitalization with onset of symptoms Anticoagulation, especially in older patients (> 75 yr.) Congestive heart failure Loss of AV synchrony Loss of atrial “kick” Rate-related cardiomyopathy due to rapid and irregular ventricular response Rate-related atrial myopathy and dilatation Chronic symptoms and reduced sense of well-being

Therapeutic Approaches to Atrial Fibrillation Anticoagulation Antiarrhythmic suppression Control of ventricular response Pharmacologic Catheter modification/ablation of AV node Curative procedures Catheter ablation Surgery (maze)

Antiarrhythmic Therapy for Atrial Fibrillation Advantages High efficacy for some patients, at least initially (< 50% of all patients) Low initial cost Noninvasive Disadvantages High recurrence rate High long-term cost Non-curative Adverse effects Potential proarrhythmia

Antiarrhythmic Suppression Drugs Conversion of AF Class 1A (decrease conduction velocity, increase refractory periods of cardiac tissue, suppress automaticity) Quinidine Procainamide Class III (decrease conduction velocity, increase refractory periods of cardiac tissue, suppress automaticity) Amiodarone Sotalol Ibutilide (Corvert) Dofetilide

Antiarrhythmic Suppression Drugs Maintenance of normal rhythm Class 1A Class III Class 1C (decrease conduction velocity) Flecainide Propafenone Drug choice depends upon patient’s underlying heart disease

Nonpharmacological Approaches to Atrial Fibrillation Pacemaker therapy 2. Ablation 3. Surgery

RF Ablation Techniques Focal ablation of PV (Pulmonary vein) triggers Segmental PV isolation Wide Area Circumferential Ablation Ablation of Fractionated Complex Electrograms Targeted ablation of ganglionated autonomic plexi in the epicardial fat pads

Focal Ablation of Triggers

Focal Ablation of Atrial Fibrillation 95% of foci are located within a pulmonary vein ( PV). Focal sources of AF may be found in the RA, LA, coronary sinus, superior vena cava or vein of Marshall. 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;339:659–66. Chen SA, et. al: Initiation of atrial fibrillation by ectopic beats originating from the pulmonary veins: Electrophysiologic characteristics, pharmacologic responses, and effects of radiofrequency ablation. Circulation 1999;100:1879-1886.

Pulmonary Vein Spike Discharges

Pulmonary Vein Spike Discharges

Initiation of AF by PV Discharges

PV Potentials PV potentials

PV Potentials

PV Potential on 6-10

PV potentials disappeared during radiofrequency current application

Loss of PV Potentials

Focal Ablation of Pulmonary Veins Complications The most common complications associated with the focal ablation of the PVs are pericardial effusion (<4%), transient ischemic episodes (<2%) and symptomatic PV stenosis <2%). Asymptomatic PV stenosis may occur at as many as 40% of sites at which focal ablation is performed. Symptomatic PV stenosis seems to be infrequent if the number of radiofrequency applications delivered within PV is kept to a minimum.

PV Stenosis

PV Stenosis

Multi-slice CT Endocardial View

PV Stenting

Tamponade: Intra-cardiac echo The incidence of perforation during ablation of the left atrium is relatively low

Segmental PV Isolation

Segmental PV Isolation Limitations associated with focal ablation have prompted the development of other techniques for eliminating the PV arrhythmias. Anatomically PV isolation has significant advantages over focal ablation.

Lasso or Spiral Catheters

Dissociation of the PV potential after successful isolation

Segmental Ostial Pulmonary Vein Isolation The initial experience with segmental ostial ablation of PVs guided by PV potentials is encouraging, with a long-term success rate of 90% in patients with paroxysmal AF Minimal risk of PV stenosis when the power of radiofrequency energy applications is limited to 30 W.

Wide Area Circumferential Ablation

Circumferential Ablation It is an anatomic approach in which circumferential lines of block are created using 3D maps ( Carto, NavX..) around the ostia of PVs for isolation of PVs from LA. Additional linear lesion from LIPV to mitral annulus for preventing LA incisional tachycardia ( 2%). Additional linear lesions (posterior, roof, right isthmus….) may be created deepening on operator’s preference. Pappone C, et al. Atrial electroanatomic remodeling after circumferential radiofrequency pulmonary vein ablation: efficacy of an anatomic approach in a large cohort of patients with atrial fibrillation. Circulation 2001;104:2539–2544.

NavX Map

Anatomical Reconstruction of LA

Circumferential Ablation

Circumferential Ablation Carto Map

Circumferential Ablation

Circumferential Ablation

Circumferential Ablation

Magnetic Resonance Image Electroanatomic Map

Circumferential Ablation Effective in both paroxysmal and chronic AF (81%, 76%) Bipolar amplitude < 0.1 mv inside and around the lesion may be acceptable for showing PV isolation.

Post Circumferential PV ablation Bipolar amplitude < 0.1 mv inside the lesion

Mitral Isthmus Line The addition of mitral isthmus line to the PV disconnection may allow a significant improvement of sinus rhythm maintenance rate, particularly in patients with persistent AF, without the risk for major complications. J Cardiovasc Electrophysiol, Vol. 16, pp. 1150-1156, November 2005

Complication rates following circumferential pulmonary vein ablation Death 0% Pericardial effusion 0.1% Stroke 0.03% Transient ischemic attack 0.2% Tamponade 0.1% Atrio-esophageal fistula 0.03% Pulmonary vein stenosis 0% Incisional left atrial tachycardia 6% Phrenic nerve injury

Topographic Variability of the Esophageal Left Atrial Relation

CT reconstruction of the LA, the pulmonary veins, and the esophagus

Topographic Variability of the Esophageal Left Atrial Relation

Phrenic Nerve Injury

Ablation of Fractionated Electrograms Hypothesis being that these are consistent sites where fibrillating wavefronts turn or split. By ablating these areas the propagating random wavefronts are progressively restricted until the atria can no longer support AF. Nademanee demonstrated 70% freedom from AF following a single procedure for permanent AF patients. Nademanee K, et al. A new approach for catheter ablation of atrial fibrillation: mapping of the electrophysiologic substrate. J Am Coll Cardiol 2004;43:2044–53.

Segmental Ablation vs. Circumferential Ablation? Is either of the two ablation strategies superior to the other? Oral et al. showed that, during the 6 months following a single catheter procedure, Circumferential Ablation was associated with a significantly better outcome with no differences between the two ablation strategies in the complication rates. Schmitt et al. reported opposite results to those of Oral et al. The opposite results in the two studies were obtained because of the large variability in the success rate observed in patients undergoing Circumferential Ablation (88 vs. 47%) while the success rates in patients undergoing Segmental Ablation remained unchanged (67 vs. 71%).

Integrated Approach Journal of Cardiovascular Electrophysiology Vol. 16, No. 12, Dec. 2005

Frequently Asked Question Who is currently a candidate for AF ablation?

Patient selection criteria Inclusion criteria At least one monthly episode of persistent symptomatic AF or At least one weekly episode of paroxysmal AF or Permanent AF And At least one failed trial of antiarrhythmic drugs or More than one antiarrhythmic drug to control symptoms Exclusion criteria NYHA functional class IV Age > 80 years Contraindications to anticoagulation Presence of cardiac thrombus Left atrial diameter ≥ 65 mm Life expectancy < 1 year Thyroid dysfunction Recent updates Patients with mitral and/or aortic metallic prosthetic valves are not excluded Previous repair of atrial septal defects is not an absolute contraindication

Frequently Asked Question AF ablation for asymptomatic individuals?

Asymptomatic Patients To date there is no evidence that treatment of AF by ablation improves mortality, although there are uncontrolled data suggesting that this may be the case. Therefore, asymptomatic patients should not be offered curative ablation of AF, except in the case of those patients undergoing cardiac surgery who may benefit from surgical ablation of their AF as an adjunctive procedure. There is also evidence that patients with heart failure have significant improvements in left ventricular function following successful catheter ablation of AF.

Conclusion For many patients with a previously untreatable heart rhythm, ablation has dramatically improved their symptoms by restoring and maintaining sinus rhythm. Preliminary randomized studies of catheter ablation of AF provide evidence that ablation (with or without concurrent anti-arrhythmic drug use) effectively improves maintenance of sinus rhythm when compared with current anti-arrhythmic drugs. Although prognostic and quality of life data from long term randomized trials of catheter ablation for AF are still in preparation, the non-randomized data comparing ablation to continued medical treatment suggests a strong benefit from ablation.

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