- Email: [email protected]
Pulmonary vein antrum isolation
Pulmonary vein antrum isolation Mohamed Kanj, MD, Oussama Wazni, MD, Andrea Natale, MD From The Cleveland Clinic, Cleveland, Ohio. Pulmonary vein antrum isolation offers safe and effective treatment of atrial fibrillation by eliminating the potential triggers of this arrhythmia. The pulmonary vein antra encompass, in addition to the pulmonary veins, the left atrial roof and posterior wall and, in the case of the right pulmonary vein antra, a portion of the interatrial septum. Compared with pulmonary vein ostial isolation, this technique offers a higher success rate and a lower complication rate. In patients with nonparoxysmal atrial fibrillation, extension of septal ablation to the region of the mitral annulus is associated with better outcomes. Further adjunctive strategies in-
Introduction Over the past decade, significant advances have been made in the catheter treatment of atrial fibrillation (AF). Throughout this period, our ablation strategy has been to eliminate potential triggers of AF, with additional substrate modification in certain patients.1 This procedure has progressed from focal pulmonary vein (PV) ablation to PV ostial and then PV antrum isolation. In our experience, the advantages of PV antrum isolation over the other ablative strategies include a higher clinical success rate and a lower incidence of postprocedural atrial arrhythmias and PV stenosis.
PV antrum origin and anatomic definition As the atrial walls expand during the early embryologic stages, the smooth tissue of the PVs becomes incorporated into the walls of the left atrium (LA), which later becomes the posterior wall and some of the roof of the LA. This incorporated portion of the LA along with the PVs defines the PV antra. PV antra are funnel-like structures. The anterior border of the left PV antrum coincides with the anterior aspect of the PV ostia. However, posteriorly the antrum diverges to encompass a significant portion of the LA posterior wall (Figure 1A). On the other hand, the right PV antrum encompasses the right PVs, with further extensions anteriorly and superiorly into the anterior interatrial septum (Figures 1B and 2). Posteriorly, the right and left PV antra form most, if not all, of the LA posterior wall (Figure 1C). The best imaging modality for defining the PV antra remains three-dimensional computed tomography (CT) and magnetic resonance imaging (MRI). However, their use is limited because of their inability Address reprint requests and correspondence: Dr. Andrea Natale, Department of Cardiovascular Medicine, Cleveland Clinic, 9500 Euclid Avenue F15, Cleveland, Ohio 44195. E-mail address: [email protected].
clude ablation in the coronary sinus, atrial side of inferior mitral annulus, superior vena cava, and along the cristae terminalis, targeting complex fragmented electrograms. We usually reserve these adjunctive ablative therapies for patients with persistent or chronic atrial fibrillation and those with unsuccessful prior catheter ablation. KEYWORDS Atrial fibrillation; catheter ablation; Antrum ablation; Intracardiac echocardiography (Heart Rhythm 2007;4:S73–S79) © 2007 Heart Rhythm Society. All rights reserved.
to produce real-time images. Intracardiac echocardiography (ICE), on the other hand, usually is sufficient for defining the antra and often provides a real-time update on the location of catheters along the PV antrum–LA junction (Figure 3).
Anticoagulation protocol We routinely perform this procedure while patients are fully anticoagulated, with a therapeutic international normalized ratio (INR) between 2 and 3.5. Patients with chronic AF must have therapeutic INRs for at least 2 months before the procedure. Heparin bolus (100 –150 units/kg) is always given before transseptal punctures. The patient is maintained on a heparin infusion rate of 15 to 20 units/kg, and the infusion rate is adjusted to keep the activated clotting time in the range from 350 to 450 seconds.2 Activated clotting times usually are checked every 10 to 15 minutes throughout the procedure. Lower heparin infusion rates may be needed in case of open irrigation catheter use to account for the heparin in the irrigated saline.
Transseptal puncture PV antrum isolation is performed using two catheters: a circular mapping catheter and an ablation catheter. Thus, we perform LA catheterization through two transseptal punctures in the midposterior interatrial septum. More anterior punctures are avoided because they usually limit catheter reach. In addition, we avoid one transseptal puncture with a double-wire technique because it hampers catheter maneuverability.
Energy and catheter choice Although antrum isolation can be performed with any of the energy delivery systems available, radiofrequency (RF) energy seems to be the most reliable. RF energy can be delivered using standard or irrigated (open or closed) RF catheters. Open irrigation catheters have multiple advan-
1547-5271/$ -see front matter © 2007 Heart Rhythm Society. All rights reserved.
doi:10.1016/j.hrthm.2006.12.036
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Figure 1 Three-dimensional computed tomographic reconstruction of the left atrium. A: Right anterior oblique view of the left atrium showing the left pulmonary vein (PV) antrum. B: Left anterior oblique view of the left atrium showing the right superior and inferior PVs (blue) and the right PV antrum (red). Note that the extensions of the right PV antrum anteriorly and superiorly. C: Posteroanterior view of the left atrium showing the left and right PV ostia (cyan) and antra (blue). Note that the posterior wall of the left atrium is part of the PV antra.
tages over passive cooling catheters (8 mm), including higher signal-to-noise ratio, fewer far-field artifacts, decreased thrombogenicity, and better energy delivery in areas of low blood flow.3 However, the use of open irrigated catheters often is associated with significant fluid overload and increased risks of tissue overheating and pops.
For the 8-mm passive cooling catheter, we set the RF energy to 30 W and the temperature to 55°C. The power is titrated in 5-W increments every few seconds to a maximum of 70 W while checking for microbubbles.4 For open irrigated catheters, we use manual power delivery settings at 35 W and titrate the power up to a maximum of 50 W while
Figure 2 Intracardiac echocardiographic (A) and anteroposterior (B) and left anterior oblique (C) fluoroscopic images of the circular mapping catheter (CMC) at the superior anterior extension of the right superior pulmonary vein (RSPV) antrum.
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Figure 3 Intracardiac echocardiographic images of the left atrium. A: Circular mapping catheter (CMC) at the ostium of the left inferior pulmonary vein (PV). Note that the anterior portion of the left inferior PV ostium constitutes the anterior lip of the left inferior pulmonary vein antrum. B: CMC positioned posterior to the left inferior PV. C: CMC positioned posterior to left superior PV. D: CMC at the ostium of the right inferior PV. E: CMC just superior to the right inferior PV and posterior to the right superior PV. F: CMC at the posterior wall in between the right and left inferior PVs. G: CMC septal to the right inferior PV. H: CMC at the ostium of the right superior PV. I: ICE image illustrating the distinction between PV ostium and antrum.
monitoring for impedance rise. A lower energy setting (maximum 30 –35 W) usually is used for delivery to the posterior wall. A temperature probe is routinely placed in the esophagus, and energy delivery is halted if esophageal temperature rises. In addition, RF energy applications over the esophagus usually are limited to 20 seconds.
PV antrum isolation The circular mapping catheter usually is advanced through a Mullins sheath, and the ablation catheter usually is advanced through an SR0 or SL0 sheath. Different sheaths and different curve catheters can be used, depending on the LA anatomy and the operator’s preference. The circular mapping catheter is positioned at the PV antrum–LA junction guided by ICE. RF energy is delivered, targeting potentials on the portion of the circular mapping catheter that defines the PV antrum–LA junction. Each ablation treatment has the endpoint of local potential elimination; thus, the duration of energy application is not fixed and is dependant on the potentials being ablated. The circular mapping catheter
is moved to another location along the PV antrum–LA junction, and further RF energy is applied (Figure 4). This continues until the entire PV antrum–LA junction is ablated. This procedure may require two operators standing side by side, each operating a catheter. The endpoint of this procedure is electrical isolation of all the PV antra. This is defined by entrance and/or exit block into or from the PV antra. Exit block is demonstrated by the presence of dissociated PV potentials that do not conduct into the LA (Figure 5A). Entrance block is demonstrated by lack of potentials inside the PV antrum and not by voltage amplitude reduction (Figure 5B). We routinely seek electrical isolation because we believe that substrate modification of the LA is not sufficient for treatment of AF and that ablation or isolation of AF triggers provides a clinical advantage. Careful attention should be paid to differentiating local PV antrum potentials from far-field potentials to avoid unnecessary energy delivery. Far-field potentials often lack sharp deflection and can be easily differ-
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Figure 4 Cartoon illustrating the circular mapping catheter movement during isolation of part of the right pulmonary vein antrum. The circular mapping catheter is represented by dashed circles. Dots represent the radiofrequency ablation delivered at the respective circular mapping catheter position.
entiated from local PV potentials by differential pacing maneuvers. If PV antrum isolation is not achieved, breakthrough conduction gaps are checked along the PV antrum–LA junction and ablated. Gaps often are identified at the circular mapping catheter sites with the earliest local activity or sites of reversal of local electrogram. During RF energy delivery, it is advisable to avoid direct contact between the ablation catheter and the circular mapping catheter electrodes to prevent char formation on the latter. Further RF energy is applied in the posterior wall and the roof of the LA. The ablation of the roof should connect the superior portions of the left and right PV antra. This usually is performed with the circular mapping catheter positioned at various positions in the roof of the LA. The circular mapping catheter will provide stability by acting as an anchor for the ablation catheter and a tool for monitoring conduction across the roof of the LA. To decrease radiation exposure, we use ICE, RF energy artifact seen on the circular mapping catheter, and occasionally three-dimensional mapping systems (CARTO XP Merge, NavX, and LocaLisa) to assist with monitoring catheter position and manipulation (Figure 6A).
Adjunctive therapies to PV antrum Isolation Adjunctive ablative therapies can be performed in patients with persistent or chronic AF. 1. Septal Ablation: Extension of the anterior portion of the right PV antrum into the interatrial septum has been shown to be associated with higher clinical success rates (freedom from AF) in patients with persistent and chronic AF (Figure 6B).5
2. Ganglionic Plexi: Some investigators proposed the role of ganglionic plexi in initiation and maintenance of AF.6 These plexi usually are located at the border of the PV antra at the following locations: anterior to the right PVs, inferior to the right inferior PV, superior and medial to the left superior PV, and inferior to the left inferior PV. In a study performed at our institution, we documented successful ablation of these plexi using standard PV antrum isolation.7 Thus, PV antrum isolation may be sufficient to ablate these plexi. 3. Continuous Fractionated Atrial Electrogram: Continuous fractionated atrial electrogram (CFAE) spots ablation has been suggested by some investigators as an ablative strategy for AF.8 In our experience, CFAE spots ablation that was performed as an adjunctive ablative strategy to antrum isolation was associated with a higher incidence of intraprocedural rhythm conversion into organized atrial tachycardias but not into sinus rhythm in patients with chronic AF.9 Whether this translates into higher long-term success rate is not known. 4. AF Nests: Real-time spectral mapping using fast Fourier transformation (FFT) in sinus rhythm has identified atrial sites in which the local bipolar electrograms contain unusually higher frequencies; such sites are called fibrillar myocardium or an AF nest.10 In our experience, AF nests are commonly located at the base of the LA appendage, posterolateral mitral annulus, anterior aspect of the interatrial septum, coronary sinus, low crista terminalis, and septal aspect of the superior vena cava–right atrial junction. Ablation of these AF nest sites abolishes the high-frequency potentials and normalizes the spectrum of the local bipolar electrogram (Figure 7). Unlike
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Figure 5 Circular mapping catheter recordings from a pulmonary vein antrum after successful ablation. A: Dissociated pulmonary vein potentials seen with exit block. B: Entrance block documented by the lack of potentials inside the pulmonary vein antrum.
the case of CFAE spots, normalization of FFT analysis requires shorter periods of RF energy delivery. A prospective study evaluating the efficacy of AF nest ablation
as an adjunctive therapy to PV antrum isolation showed a significant improvement in clinical success rates during short-term follow up.11
Figure 6 CARTO XP Merge electroanatomic registration during pulmonary vein antrum isolation in a patient with chronic atrial fibrillation. A: Cranial right anterior oblique view showing a roof ablation and the extension of the radiofrequency lesions into the mitral annulus at the septal region in patients with chronic atrial fibrillation. B: Posterior anterior view showing isolation of the pulmonary vein antrum along with the posterior wall of the left atrium.
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Figure 7 Spectral analysis of “fibrillar” myocardial potentials located in the coronary sinus before (A) and after (B) radiofrequency ablation. Before ablation, there are at least three prominent frequencies, one fundamental (#) and two harmonics (*). After ablation, there was resolution of the higher harmonic frequencies.
5. Other Thoracic Veins: The patient population that would benefit from thoracic vein isolation, such as superior vena cava, coronary sinus, and persistent left superior vena cava, has not been thoroughly defined. In our experience, coronary sinus isolation is important in patients with chronic AF or hypertrophic cardiomyopathy, and superior vena cava isolation is important in patients with obesity or sleep apnea. 6. Other Atrial Triggers: For the past decade, we have used high-dose isoproterenol (up to 20 g/min) for initiation of atrial arrhythmias that may act as triggers for AF. We have found this approach to be very sensitive but of moderate specificity. To improve its specificity, we target only sustained atrial tachycardia or single or bursts of premature atrial complexes that induce AF. Fortunately, this extensive ablative procedure does not affect overall LA contraction. In a recent study performed at our institution, LA systolic function was preserved after PV antrum isolation.12
Complications In our experience, vascular complications are the most common complications seen with PV antrum isolation. Groin and necks hematomas are the most frequent, with an incidence of 1% to 2%. Cerebrovascular events usually are thromboembolic and are seen in fewer than 0.5% of patients. Other complications include PV stenosis, cardiac perforation and tamponade, and phrenic nerve or vagus nerve palsies.
Conclusion and future directions The minimal set of lesions required to treat AF is still undetermined. In our experience, PV antrum isolation is essential for the treatment of all types of AF: paroxysmal,
persistent, and chronic. PV antrum isolation remains a complex ablation procedure requiring high technical skills. We hope that advancements in robotic technology and magnetically guided catheter manipulation and improvements in electroanatomic mapping and registration will revolutionize this field of complex ablations.
References 1. Wazni OM, Marrouche NF, Martin DO, Verma A, Bhargava M, Saliba W, Bash D, Schweikert R, Brachmann J, Gunther J, Gutleben K, Pisano E, Potenza D, Fanelli R, Raviele A, Themistoclakis S, Rossillo A, Bonso A, Natale A. Radiofrequency ablation vs antiarrhythmic drugs as first-line treatment of symptomatic atrial fibrillation: a randomized trial. JAMA 2005;293: 2634 –2640. 2. Wazni OM, Rossillo A, Marrouche NF, Saad EB, Martin DO, Bhargava M, Bash D, Beheiry S, Wexman M, Potenza D, Pisano E, Fanelli R, Bonso A, Themistoclakis S, Erciyes D, Saliba WI, Schweikert RA, Brachmann J, Raviele A, Natale A. Embolic events and char formation during pulmonary vein isolation in patients with atrial fibrillation: impact of different anticoagulation regimens and importance of intracardiac echo imaging. J Cardiovasc Electrophysiol 2005;16: 576 –581. 3. Wittkampf FH, Nakagawa H, Foresti S, Aoyama H, Jackman WM. Salineirrigated radiofrequency ablation electrode with external cooling. J Cardiovasc Electrophysiol 2005;16:323–328. 4. Marrouche NF, Martin DO, Wazni O, Gillinov AM, Klein A, Bhargava M, Saad E, Bash D, Yamada H, Jaber W, Schweikert R, Tchou P, Abdul-Karim A, Saliba W, Natale A. Phased-array intracardiac echocardiography monitoring during pulmonary vein isolation in patients with atrial fibrillation: impact on outcome and complications. Circulation 2003;107:2710 –2716. 5. Verma A, Burkhardt J, Martin D, Elayi C, Wazni O, Cummings J, Thal S, Lakkreddy D, Saliba W, Schweikert R, Natale A. Efficacy of adjunctive septal ablation during intracardiac echocardiography guided pulmonary vein antrum isolation. J Cardiovasc Electrophysiol 2007;18:1– 6. 6. Scherlag BJ, Nakagawa H, Jackman WM, Yamanashi WS, Patterson E, Po S, Lazzara R. Electrical stimulation to identify neural elements on the heart: their role in atrial fibrillation. J Interv Card Electrophysiol 2005;13(Suppl 1):37– 42. 7. Verma A, Saliba W, Lakkreddy D, Burkhardt J, Cummings J, Wazni O, Elayi C, Thal S, Schweikert R, Martin D, Natale A. Vagal responses induced by left atrial parasympathetic ganglion stimulation pre- and post-intracardiac echocardiography guided pulmonary vein antrum isolation for atrial fibrillation. American College of Cardiology Scientific Sessions 2005. 8. Nademanee K, McKenzie J, Kosar E, Schwab M, Sunsaneewitayakul B, Vasavakul T, Khunnawat C, Ngarmukos T. A new approach for catheter ablation of
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atrial fibrillation: mapping of the electrophysiologic substrate. J Am Coll Cardiol 2004;43:2044 –2053. 9. Elayi CS, Arruda M, Wazni OM, Atul V, Di Biase L, Khaykin Y, Ching CK, Patel D, Kanj M, Fahmy TS, Khan M, Thal S, Dresing T, Martin D, Burkhardt D, Schweikert R, Saliba W, Natale A. Atrial fibrillation termination mode comparing three common ablation strategies for permanent atrial fibrillation: results from a randomized study. American Heart Association Scientific Sessions, Chicago, Illinois, November 2006. 10. Pachon M JC, Pachon M EI, Pachon M JC, Lobo TJ, Pachon MZ, Vargas RN, Pachon DQ, Lopez M FJ, Jatene AD. A new treatment for atrial fibrillation based on spectral analysis to guide the catheter RF-ablation. Europace 2004;6: 590 – 601.
S79 11. Arruda M, Prasad SK, Kozeluhova M, Patel D, Schweikert R, Saliba W, Burkhardt J, Bhargava M, Cummings J, Martin D, Pachon-M EI, Tchou P, Pachon-M J, Natale A. Combined spectral mapping guided AF-nests ablation and pulmonary vein antrum isolation: a new approach to improve AF ablation success. Heart Rhythm Society Scientific Sessions, Boston, Massachusetts, May 2006. 12. Verma A, Kilicaslan F, Adams JR, Hao S, Beheiry S, Minor S, Ozduran V, Claude Elayi S, Martin DO, Schweikert RA, Saliba W, Thomas JD, Garcia M, Klein A, Natale A. Extensive ablation during pulmonary vein antrum isolation has no adverse impact on left atrial function: an echocardiography and cine computed tomography analysis. J Cardiovasc Electrophysiol 2006;17: 741–746.
Introduction Over the past decade, significant advances have been made in the catheter treatment of atrial fibrillation (AF). Throughout this period, our ablation strategy has been to eliminate potential triggers of AF, with additional substrate modification in certain patients.1 This procedure has progressed from focal pulmonary vein (PV) ablation to PV ostial and then PV antrum isolation. In our experience, the advantages of PV antrum isolation over the other ablative strategies include a higher clinical success rate and a lower incidence of postprocedural atrial arrhythmias and PV stenosis.
PV antrum origin and anatomic definition As the atrial walls expand during the early embryologic stages, the smooth tissue of the PVs becomes incorporated into the walls of the left atrium (LA), which later becomes the posterior wall and some of the roof of the LA. This incorporated portion of the LA along with the PVs defines the PV antra. PV antra are funnel-like structures. The anterior border of the left PV antrum coincides with the anterior aspect of the PV ostia. However, posteriorly the antrum diverges to encompass a significant portion of the LA posterior wall (Figure 1A). On the other hand, the right PV antrum encompasses the right PVs, with further extensions anteriorly and superiorly into the anterior interatrial septum (Figures 1B and 2). Posteriorly, the right and left PV antra form most, if not all, of the LA posterior wall (Figure 1C). The best imaging modality for defining the PV antra remains three-dimensional computed tomography (CT) and magnetic resonance imaging (MRI). However, their use is limited because of their inability Address reprint requests and correspondence: Dr. Andrea Natale, Department of Cardiovascular Medicine, Cleveland Clinic, 9500 Euclid Avenue F15, Cleveland, Ohio 44195. E-mail address: [email protected].
clude ablation in the coronary sinus, atrial side of inferior mitral annulus, superior vena cava, and along the cristae terminalis, targeting complex fragmented electrograms. We usually reserve these adjunctive ablative therapies for patients with persistent or chronic atrial fibrillation and those with unsuccessful prior catheter ablation. KEYWORDS Atrial fibrillation; catheter ablation; Antrum ablation; Intracardiac echocardiography (Heart Rhythm 2007;4:S73–S79) © 2007 Heart Rhythm Society. All rights reserved.
to produce real-time images. Intracardiac echocardiography (ICE), on the other hand, usually is sufficient for defining the antra and often provides a real-time update on the location of catheters along the PV antrum–LA junction (Figure 3).
Anticoagulation protocol We routinely perform this procedure while patients are fully anticoagulated, with a therapeutic international normalized ratio (INR) between 2 and 3.5. Patients with chronic AF must have therapeutic INRs for at least 2 months before the procedure. Heparin bolus (100 –150 units/kg) is always given before transseptal punctures. The patient is maintained on a heparin infusion rate of 15 to 20 units/kg, and the infusion rate is adjusted to keep the activated clotting time in the range from 350 to 450 seconds.2 Activated clotting times usually are checked every 10 to 15 minutes throughout the procedure. Lower heparin infusion rates may be needed in case of open irrigation catheter use to account for the heparin in the irrigated saline.
Transseptal puncture PV antrum isolation is performed using two catheters: a circular mapping catheter and an ablation catheter. Thus, we perform LA catheterization through two transseptal punctures in the midposterior interatrial septum. More anterior punctures are avoided because they usually limit catheter reach. In addition, we avoid one transseptal puncture with a double-wire technique because it hampers catheter maneuverability.
Energy and catheter choice Although antrum isolation can be performed with any of the energy delivery systems available, radiofrequency (RF) energy seems to be the most reliable. RF energy can be delivered using standard or irrigated (open or closed) RF catheters. Open irrigation catheters have multiple advan-
1547-5271/$ -see front matter © 2007 Heart Rhythm Society. All rights reserved.
doi:10.1016/j.hrthm.2006.12.036
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Heart Rhythm, Vol 4, No 3, March Supplement 2007
Figure 1 Three-dimensional computed tomographic reconstruction of the left atrium. A: Right anterior oblique view of the left atrium showing the left pulmonary vein (PV) antrum. B: Left anterior oblique view of the left atrium showing the right superior and inferior PVs (blue) and the right PV antrum (red). Note that the extensions of the right PV antrum anteriorly and superiorly. C: Posteroanterior view of the left atrium showing the left and right PV ostia (cyan) and antra (blue). Note that the posterior wall of the left atrium is part of the PV antra.
tages over passive cooling catheters (8 mm), including higher signal-to-noise ratio, fewer far-field artifacts, decreased thrombogenicity, and better energy delivery in areas of low blood flow.3 However, the use of open irrigated catheters often is associated with significant fluid overload and increased risks of tissue overheating and pops.
For the 8-mm passive cooling catheter, we set the RF energy to 30 W and the temperature to 55°C. The power is titrated in 5-W increments every few seconds to a maximum of 70 W while checking for microbubbles.4 For open irrigated catheters, we use manual power delivery settings at 35 W and titrate the power up to a maximum of 50 W while
Figure 2 Intracardiac echocardiographic (A) and anteroposterior (B) and left anterior oblique (C) fluoroscopic images of the circular mapping catheter (CMC) at the superior anterior extension of the right superior pulmonary vein (RSPV) antrum.
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Figure 3 Intracardiac echocardiographic images of the left atrium. A: Circular mapping catheter (CMC) at the ostium of the left inferior pulmonary vein (PV). Note that the anterior portion of the left inferior PV ostium constitutes the anterior lip of the left inferior pulmonary vein antrum. B: CMC positioned posterior to the left inferior PV. C: CMC positioned posterior to left superior PV. D: CMC at the ostium of the right inferior PV. E: CMC just superior to the right inferior PV and posterior to the right superior PV. F: CMC at the posterior wall in between the right and left inferior PVs. G: CMC septal to the right inferior PV. H: CMC at the ostium of the right superior PV. I: ICE image illustrating the distinction between PV ostium and antrum.
monitoring for impedance rise. A lower energy setting (maximum 30 –35 W) usually is used for delivery to the posterior wall. A temperature probe is routinely placed in the esophagus, and energy delivery is halted if esophageal temperature rises. In addition, RF energy applications over the esophagus usually are limited to 20 seconds.
PV antrum isolation The circular mapping catheter usually is advanced through a Mullins sheath, and the ablation catheter usually is advanced through an SR0 or SL0 sheath. Different sheaths and different curve catheters can be used, depending on the LA anatomy and the operator’s preference. The circular mapping catheter is positioned at the PV antrum–LA junction guided by ICE. RF energy is delivered, targeting potentials on the portion of the circular mapping catheter that defines the PV antrum–LA junction. Each ablation treatment has the endpoint of local potential elimination; thus, the duration of energy application is not fixed and is dependant on the potentials being ablated. The circular mapping catheter
is moved to another location along the PV antrum–LA junction, and further RF energy is applied (Figure 4). This continues until the entire PV antrum–LA junction is ablated. This procedure may require two operators standing side by side, each operating a catheter. The endpoint of this procedure is electrical isolation of all the PV antra. This is defined by entrance and/or exit block into or from the PV antra. Exit block is demonstrated by the presence of dissociated PV potentials that do not conduct into the LA (Figure 5A). Entrance block is demonstrated by lack of potentials inside the PV antrum and not by voltage amplitude reduction (Figure 5B). We routinely seek electrical isolation because we believe that substrate modification of the LA is not sufficient for treatment of AF and that ablation or isolation of AF triggers provides a clinical advantage. Careful attention should be paid to differentiating local PV antrum potentials from far-field potentials to avoid unnecessary energy delivery. Far-field potentials often lack sharp deflection and can be easily differ-
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Figure 4 Cartoon illustrating the circular mapping catheter movement during isolation of part of the right pulmonary vein antrum. The circular mapping catheter is represented by dashed circles. Dots represent the radiofrequency ablation delivered at the respective circular mapping catheter position.
entiated from local PV potentials by differential pacing maneuvers. If PV antrum isolation is not achieved, breakthrough conduction gaps are checked along the PV antrum–LA junction and ablated. Gaps often are identified at the circular mapping catheter sites with the earliest local activity or sites of reversal of local electrogram. During RF energy delivery, it is advisable to avoid direct contact between the ablation catheter and the circular mapping catheter electrodes to prevent char formation on the latter. Further RF energy is applied in the posterior wall and the roof of the LA. The ablation of the roof should connect the superior portions of the left and right PV antra. This usually is performed with the circular mapping catheter positioned at various positions in the roof of the LA. The circular mapping catheter will provide stability by acting as an anchor for the ablation catheter and a tool for monitoring conduction across the roof of the LA. To decrease radiation exposure, we use ICE, RF energy artifact seen on the circular mapping catheter, and occasionally three-dimensional mapping systems (CARTO XP Merge, NavX, and LocaLisa) to assist with monitoring catheter position and manipulation (Figure 6A).
Adjunctive therapies to PV antrum Isolation Adjunctive ablative therapies can be performed in patients with persistent or chronic AF. 1. Septal Ablation: Extension of the anterior portion of the right PV antrum into the interatrial septum has been shown to be associated with higher clinical success rates (freedom from AF) in patients with persistent and chronic AF (Figure 6B).5
2. Ganglionic Plexi: Some investigators proposed the role of ganglionic plexi in initiation and maintenance of AF.6 These plexi usually are located at the border of the PV antra at the following locations: anterior to the right PVs, inferior to the right inferior PV, superior and medial to the left superior PV, and inferior to the left inferior PV. In a study performed at our institution, we documented successful ablation of these plexi using standard PV antrum isolation.7 Thus, PV antrum isolation may be sufficient to ablate these plexi. 3. Continuous Fractionated Atrial Electrogram: Continuous fractionated atrial electrogram (CFAE) spots ablation has been suggested by some investigators as an ablative strategy for AF.8 In our experience, CFAE spots ablation that was performed as an adjunctive ablative strategy to antrum isolation was associated with a higher incidence of intraprocedural rhythm conversion into organized atrial tachycardias but not into sinus rhythm in patients with chronic AF.9 Whether this translates into higher long-term success rate is not known. 4. AF Nests: Real-time spectral mapping using fast Fourier transformation (FFT) in sinus rhythm has identified atrial sites in which the local bipolar electrograms contain unusually higher frequencies; such sites are called fibrillar myocardium or an AF nest.10 In our experience, AF nests are commonly located at the base of the LA appendage, posterolateral mitral annulus, anterior aspect of the interatrial septum, coronary sinus, low crista terminalis, and septal aspect of the superior vena cava–right atrial junction. Ablation of these AF nest sites abolishes the high-frequency potentials and normalizes the spectrum of the local bipolar electrogram (Figure 7). Unlike
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Figure 5 Circular mapping catheter recordings from a pulmonary vein antrum after successful ablation. A: Dissociated pulmonary vein potentials seen with exit block. B: Entrance block documented by the lack of potentials inside the pulmonary vein antrum.
the case of CFAE spots, normalization of FFT analysis requires shorter periods of RF energy delivery. A prospective study evaluating the efficacy of AF nest ablation
as an adjunctive therapy to PV antrum isolation showed a significant improvement in clinical success rates during short-term follow up.11
Figure 6 CARTO XP Merge electroanatomic registration during pulmonary vein antrum isolation in a patient with chronic atrial fibrillation. A: Cranial right anterior oblique view showing a roof ablation and the extension of the radiofrequency lesions into the mitral annulus at the septal region in patients with chronic atrial fibrillation. B: Posterior anterior view showing isolation of the pulmonary vein antrum along with the posterior wall of the left atrium.
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Figure 7 Spectral analysis of “fibrillar” myocardial potentials located in the coronary sinus before (A) and after (B) radiofrequency ablation. Before ablation, there are at least three prominent frequencies, one fundamental (#) and two harmonics (*). After ablation, there was resolution of the higher harmonic frequencies.
5. Other Thoracic Veins: The patient population that would benefit from thoracic vein isolation, such as superior vena cava, coronary sinus, and persistent left superior vena cava, has not been thoroughly defined. In our experience, coronary sinus isolation is important in patients with chronic AF or hypertrophic cardiomyopathy, and superior vena cava isolation is important in patients with obesity or sleep apnea. 6. Other Atrial Triggers: For the past decade, we have used high-dose isoproterenol (up to 20 g/min) for initiation of atrial arrhythmias that may act as triggers for AF. We have found this approach to be very sensitive but of moderate specificity. To improve its specificity, we target only sustained atrial tachycardia or single or bursts of premature atrial complexes that induce AF. Fortunately, this extensive ablative procedure does not affect overall LA contraction. In a recent study performed at our institution, LA systolic function was preserved after PV antrum isolation.12
Complications In our experience, vascular complications are the most common complications seen with PV antrum isolation. Groin and necks hematomas are the most frequent, with an incidence of 1% to 2%. Cerebrovascular events usually are thromboembolic and are seen in fewer than 0.5% of patients. Other complications include PV stenosis, cardiac perforation and tamponade, and phrenic nerve or vagus nerve palsies.
Conclusion and future directions The minimal set of lesions required to treat AF is still undetermined. In our experience, PV antrum isolation is essential for the treatment of all types of AF: paroxysmal,
persistent, and chronic. PV antrum isolation remains a complex ablation procedure requiring high technical skills. We hope that advancements in robotic technology and magnetically guided catheter manipulation and improvements in electroanatomic mapping and registration will revolutionize this field of complex ablations.
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