Surgical or catheter ablation of atrial fibrillation (AF) is an

Transcription

1 Atrial Tachycardia After Ablation of Persistent Atrial Fibrillation Identification of the Critical Isthmus With a Combination of Multielectrode Activation Mapping and Targeted Entrainment Mapping Anshul M. Patel, MD; Andre d Avila, MD, PhD; Petr Neuzil, MD, PhD; Steven J. Kim, MSEE; Theofanie Mela, MD; Jagmeet P. Singh, MD, DPhil; Jeremy N. Ruskin, MD; Vivek Y. Reddy, MD Background Atrial tachycardia (AT) that develops after ablation of atrial fibrillation often poses a more difficult clinical situation than the index arrhythmia. This study details the use of an impedance-based electroanatomic mapping system (Ensite NavX) in concert with a specialized multielectrode mapping catheter for rapid, high-density atrial mapping. In this study, this activation mapping was combined with entrainment mapping to eliminate ATs developing late after atrial fibrillation ablation. Methods and Results All study patients developed AT after ablation for atrial fibrillation. The approach to AT ablation consisted of 4 steps: use of a 20-pole penta-array catheter to map the chamber rapidly during the rhythm of interest, analysis of the patterns of atrial activation to identify wave fronts of electric propagation, targeted entrainment at putative channels, and catheter ablation at these isthmuses. All ablations were performed with irrigated radiofrequency ablation catheters. Forty-one ATs were identified in 17 patients ( ATs per patient). Using the multielectrode catheter in conjunction with the Ensite NavX system, we created activation maps of 33 of 41 ATs (81%) (mean cycle length, seconds) with a mean of points per map and an average mapping time of 8 3 minutes. Of the 33 mapped ATs, 7 terminated either spontaneously or during entrainment maneuvers. Radiofrequency energy was used to attempt ablation of 26 ATs; 25 of 26 of the ATs (96%) were terminated successfully by ablation or catheter pressure. Conclusions This study demonstrates a strategy for rapidly defining and eliminating the scar-related ATs typically encountered after ablation of atrial fibrillation. (Circ Arrhythmia Electrophysiol. 2008;1:14-22.) Key Words: arrhythmia ablation fibrillation mapping tachycardia Surgical or catheter ablation of atrial fibrillation (AF) is an accepted therapeutic option for drug-refractory, symptomatic AF. 1 6 Although patients with paroxysmal AF can be treated successfully with pulmonary vein (PV) isolation alone, additional ablation lesion sets, including linear lesions and ablation at sites of complex fractionated electrograms, are frequently placed to treat patients with persistent AF. One of the most troublesome aspects of the postablation course in this group of patients is the development of atrial tachycardias (ATs). These arrhythmias have a characteristic metronomic 2:1 ventricular response, typically are difficult to manage medically, and frequently recur after cardioversion On the other hand, ATs appear to reflect a more organized atrial substrate on the continuum between AF and sinus rhythm, and successful ablation of the AT often is the last hurdle to overcome before sinus rhythm is achieved. Clinical Perspective p 22 The mechanism of these ATs is typically macroreentry but also sometimes microreentry involving preexisting or iatrogenic ablation-related scar tissue. They typically are challenging to map and ablate because of the unpredictable location and extent of these combined idiopathic/iatrogenic scars. In an effort to efficiently identify the critical isthmuses sustaining postablation ATs, this study evaluated a systematic approach combining rapid high-density activation mapping Received November 5, 2007; accepted January 29, From the Massachusetts General Hospital, Boston (A.M.P., A.d., T.M., J.P.S., J.N.R., V.Y.R.); Homolka Hospital, Prague, Czech Republic (P.N.); and St. Jude Medical, Minneapolis, Minn (S.J.K.). Presented in part at the 2007 Annual Sessions of the Heart Rhythm Society, Denver, Colo, May 9 12, 2007, and published in abstract form (Heart Rhythm. 2007;4:S345). The online Data Supplement can be found with this article at Correspondence to Vivek Y. Reddy, MD, Cardiac Arrhythmia Service, Massachusetts General Hospital, 55 Fruit St, GRB-109, Boston, MA vreddy@partners.org 2008 American Heart Association, Inc. Circ Arrhythmia Electrophysiol is available at DOI: /CIRCEP

2 Patel et al Atrial Tachycardia After AF Ablation 15 Table 1. Patient Characteristics Patient Age, y Sex LA Size, mm Ejection Fraction, % Prior Ablation Procedures Index Ablation Second Ablation 1 47 Male PVI Female PVI, CFAE, CTI Male PVI, CTI PVI, septal radiofrequency application, mitral isthmus with a penta-array mapping catheter coupled to an electrical impedance-based electroanatomic mapping system (Ensite NavX, St. Jude Medical, Minneapolis, Minn) and targeted entrainment. This strategy was assessed in a consecutive series of patients who presented with ATs after prior extensive ablation of persistent AF. Methods Study Population The study population consisted of 17 consecutive patients presenting with drug-refractory postablation ATs. All had a history of symptomatic persistent or long-lasting, persistent AF and had undergone at least 1 prior catheter or surgical ablation procedure for AF. The baseline characteristics are described in Table 1. Previous Ablation Procedure All patients had at least 1 previous catheter ablation for AF. The catheter ablation procedures involved a combination of extraostial PV isolation, cavotricuspid isthmus (CTI) ablation, left atrial (LA) roof line, mitral isthmus line, and complex fractionated atrial Clinical AT Cycle Length, ms Time Between AF and AT Ablation, mo Induced ATs at Electrophysiological Study, n Male PVI PVI, CTI, mitral isthmus 5 57 Male PVI, roof line, CTI, CFAE, mitral isthmus Male PVI, roof line, CTI, mitral isthmus 7 57 Male PVI, roof line, CTI, mitral isthmus, CFAE 8 58 Male PVI, roof line, posterior wall line 9 60 Male PVI, roof line, CTI, CFAE Female PVI, CTI Male Surgical Maze PV antral ablation Male PVI, mitral isthmus, CTI Male PVI, roof line, CTI Male PVI, roof line, CTI, CFAE, superior vena cava isolation Female PVI, roof line, CTI, CFAE, mitral isthmus Male PVI, roof line, CTI, CFAE, mitral isthmus Male PVI, roof line, CTI, mitral isthmus, CFAE CFAE PVI indicates extraostial circumferential ablation with electric PV isolation; roof line, LA linear roof ablation; and CFAE, complex fractionated atrial electrograms. electrogram ablation in the LA, right atrium (RA), and/or the coronary sinus (CS). All patients had ECG documentation of AT refractory to antiarrhythmic drugs. One patient also had initially undergone a surgical maze procedure for AF during concomitant mitral valve replacement surgery. Electrophysiology Study for AT For all patients, antiarrhythmic drugs and warfarin sodium were continued up to the day of the ablation. The international normalized ratio was therapeutic (INR 2 3) at the time of the procedure. The surface ECG and bipolar endocardial electrograms were monitored continuously and stored on a computer-based digital amplifier/recorder system (GE Cardiolab, Waukesha, Wis). Intracardiac electrograms were filtered from 30 to 500 Hz and measured at a sweep speed of 100 to 200 mm/s. A standard decapolar catheter was placed in the CS. A quadripolar reference electrode also was placed in the CS, RA appendage, or aortic root to serve as a location reference for the Ensite NavX mapping system. 15 Transseptal access was obtained with contrast, fluoroscopy, and intracardiac echocardiography to place both an Agilis steerable sheath and a Daig SL-1 sheath (St. Jude Medical, St Paul, Minn) in the LA. A circular mapping catheter and either a

3 16 Circ Arrhythmia Electrophysiol April 2008 Figure 1. A, The penta-array catheter fully deflected with its 5 splines in a radial array, each with 4 electrodes. B, With the NavX system, the locations of the various splines are displayed on a 3-dimensional computed tomography image of the LA in a posteroanterior (PA) view; the penta-array catheter is shown as 5 quadripolar catheters in a radial array. From left to right, the sequential acquisition of the contact electrogram activity obtained as the penta-array catheter is swept up the posterior wall, thereby demonstrating how rapid activation mapping can be performed. To better represent this motion, a movie version of atrial mapping with this approach is available in the online Data Supplement. 3.5-mm-tip Celsius Thermo-Cool (Biosense-Webster, Inc, Diamond Bar, Calif) or Chili (Boston Scientific, Inc, Natick, Mass) ablation catheter were placed through these sheaths into the LA. In all patients, AT was present at baseline or was induced with rapid atrial pacing from the CS. First, the patients were evaluated for CTI-dependent atrial flutter by entrainment from the distal and proximal CS electrodes and, if suggestive, from the CTI itself. Using the Ensite NavX system, we acquired separate multicomponent geometries of the LA appendage, left superior PV, left inferior PV, right superior PV, right inferior PV, and LA body with the circular mapping catheter. These were combined into 1 structure as the electroanatomic map of the LA and PVs and then compared alongside a 3-dimensional computed tomography or magnetic resonance of the LA. When ablation was performed in the RA, a separate geometry of the RA was created. PV Isolation All of the PVs were evaluated for electric disconnection with a multipolar circular mapping catheter (Lasso or Optima catheters; Biosense-Webster, Inc, and St Jude Medical, Inc, respectively). If any reconnection was found, the veins were reisolated, typically requiring only a single ablation lesion at the point of breakthrough. Electric PV isolation was then confirmed with the circular mapping catheter. Activation Mapping The penta-array catheter is a 20-pole steerable mapping catheter arranged in 5 soft radiating spines (1-mm electrodes separated by 4-, 4-, and 4-mm interelectrode spacing) covering a diameter of 3.5 cm (PentaRay, Biosense-Webster, Inc). The penta-array catheter often was manipulated through the steerable sheath to facilitate mapping. Each electrode of this penta-array catheter can be localized by the Ensite NavX system so that the catheter is ultimately visualized as 5 radiating quadripolar splines (Figure 1). After introduction into the LA, activation mapping of the AT was performed. Fifteen bipolar electrograms are acquired simultaneously at each location, thereby allowing rapid creation of activation maps. Potential critical isthmuses were identified as areas of constrained activation (resulting from the idiopathic or iatrogenic scars and anatomic barriers), often also containing fractionated electrograms (Figure 2). Entrainment Mapping Once these wave fronts of atrial activation and putative isthmus sites were identified, entrainment pacing maneuvers were performed from the ablation catheter at these sites at a cycle length 20 to 30 ms less than the tachycardia cycle length (TCL; Figure 3). The site was considered part of the circuit if the postpacing interval (PPI) measured from the stimulation artifact to the return atrial electrogram on the ablation catheter was within 20 ms of the TCL. Radiofrequency Ablation Using the irrigated ablation catheter, we performed radiofrequency ablation with 20 to 50 W of energy and flow rates of 36 and 30 cm 3 /min, using internal or external irrigation, respectively. Energy was titrated to achieved an 10% Ohm impedance drop (Figure 4). If the AT terminated during radiofrequency ablation, rapid atrial pacing was performed to reinduce the arrhythmia. If it remained Figure 2. A, Activation map of a roof macroreentrant AT. The white arrow points to a gap in a previous roof line where the propagation map shows wave-front breakthrough. Electrograms (white arrow) at that site were done during the diastolic interval when the surface ECG was isoelectric, confirming that this was a protected isthmus. Entrainment maneuvers were performed just anterior and posterior to the site because of a high threshold for capture at the site and confirmed that the PPI TCL. B, The macroreentrant AT (cycle length, 305 ms). Leads II and V 1, the ablation catheter electrogram, and proximal CS and distal CS electrograms are shown (at 50 mm/s). A single radiofrequency application at the roof gap eliminated the AT and resulted in normal sinus rhythm.

4 Patel et al Atrial Tachycardia After AF Ablation 17 Arrhythmia Service clinic at Massachusetts General Hospital, including Holter monitoring. Acute success was monitored at a 6- to 8-week follow-up appointment with an office ECG and instructions for the patient to notify his or her physician with any symptomatic recurrence. Holter recordings were obtained 6 weeks and 6 months after the procedure, or sooner at the discretion of the treating physician. The authors had full access to and take full responsibility for the integrity of the data. All authors have read and agree to the manuscript as written. Figure 3. A, An activation map of an AT (255 ms) in a modified posteroinferior view (left) and right anterior oblique view. On the basis of targeted entrainment, the active (green dots) and passive (brown dots) activation wave fronts were easily differentiated. B, The activation map is shown with similar views. Green arrows represent the wave fronts of active activation (ie, good PPI); areas of passive activation are delineated by the brown arrows (ie, bad PPI). If the PPI measured from the stimulation artifact to the return atrial electrogram on the ablation catheter was within 20 ms of the TCL, the site was considered a good PPI. If the PPI was 20 ms, the site was considered a bad PPI. For example, the superior activation of the posterior wall is passive and does not contribute to the AT mechanism. Although the mitral isthmus clearly was part of the AT circuit, a narrow isthmus on the anterior left atrium was identified. RIPV indicates right inferior PV; RSPV, right superior PV; and LIPV, left inferior PV. noninducible, the ablation was considered successful. If another AT was induced, it was then targeted for ablation. When linear ablation was used across an isthmus, activation mapping and/or differential pacing on either side of the ablation line was used to confirm block. Follow-Up After the procedure, membrane-active antiarrhythmic medications were stopped for all patients. Anticoagulation with warfarin was continued with a target international normalized ratio of 2 3. All patients received routine postprocedure follow-up in the Cardiac Results Patient Characteristics and Previous Ablations Patient characteristics and previous ablation data are listed in Table 1. The mean age of the patients was years. The mean left atrial size was 40 5 mm. Two patients had previously documented coronary disease. The mean ejection fraction was 61 14%. One patient (patient 11) had previously undergone mitral valve replacement surgery and had a low ejection fraction (12%) resulting from tachycardia-induced cardiomyopathy. Four patients had undergone 2 previous LA ablation procedures. The second ablation for 3 of those patients was for AT after AF ablation (patients 3, 4, and 16); for 1 patient, it was for AF (patient 11). The mean time from the prior index AF ablation procedure to the current AT procedure was months (range, 1 to 21 months). AT Characteristics All patients had AT documented on 12-lead ECG (Table 1). The mean cycle length of the clinical ATs was ms (range, 210 to 380 ms). A total of 41 ATs were identified at the electrophysiology study in 17 patients, 1 of whom underwent 2 AT ablation procedures. The mean AT cycle length was ms (range, 175 to 550 ms). The number of ATs per patient averaged (range, 1 to 6). Activation Mapping Using the Ensite NavX-tracked penta-array mapping catheter, we performed activation maps in 33 of 41 ATs (81%). The characteristics of all ATs for which activation maps were created are summarized in Table 2. Eight ATs were not mapped because they stopped spontaneously before any Figure 4. A, For the same patient in Figure 3, the activation wave front of the AT is shown in a right anterior oblique projection. The block arrow marks the site of the diastolic potential and the critical isthmus (eventual site of termination of the AT with a single RF application). B, The surface ECG (V 1 ) and an electrogram recorded from the ablation catheter show a diastolic potential 53 ms earlier than the surface P wave, indicating that this is a protected isthmus and, given a good PPI, was likely critical to the circuit. C, The surface ECG (V 1 ), ablation catheter electrogram (ABL), and proximal CS (CS p) electrogram during successful termination at this critical isthmus with a diastolic potential. The beat after termination is atrial pacing. RSPV indicates right superior PV.

5 18 Circ Arrhythmia Electrophysiol April 2008 Table 2. AT Patient Mapped AT Characteristics AT Cycle Length, ms Mechanism AT Location Mode of Termination mapping and did not recur. The mean cycle length of the mapped ATs was ms (range, 175 to 550 ms). For 3 of the mapped ATs, detailed mapping data were not available for posthoc analysis. For the other 30 ATs, the activation maps included a mean of points, each of which required a mean of separate acquisitions with the penta-array catheter. For the macroreentrant ATs, these maps constituted, on average, 96 1% of the TCL. For 14 of the mapped ATs, the time to create an activation map was recorded; the mean time was 8 3 minutes. Macroreentry versus focal microreentry ATs were defined on the basis of the AT activation map. Unlike macroreentrant ATs, the circuits of which traversed large portions of the atrium, focal ATs clinically mapped to a point source with centrifugal activation from this center. In 25 of 33 (78%), the mechanism was macroreentrant. In 8 of 33 (22%), the Follow-Up, mo Recurrence? Macroreentrant Septum Ibutilide 8 Yes; awaiting repeat radiofrequency application Focal Inferior to left inferior PV Spontaneous Focal Right superior PV/septum Linear lesion 10 Yes; after cardioversion, no further recurrence Focal Posterior septum 4 RF lesions 10 No Macroreentrant Mitral isthmus 2 RF lesions Focal Right inferior PV 2 RF lesions 4 No 7 5-1* 280 Macroreentrant Mitral isthmus Entrainment Yes; repeat radiofrequency 8 5-1* 250 Macroreentrant Roof 8 RF lesions application performed 9 5-2* 300 Macroreentrant Roof 1 RF lesion * 245 Macroreentrant Mitral isthmus Spontaneous 8 No * 320 Macroreentrant Mitral isthmus Linear lesion Macroreentrant Mitral isthmus 1 RF lesion 14 No Focal Right inferior PV Entrainment Macroreentrant Mitral isthmus 3 RF lesions 11 No Macroreentrant Mitral isthmus Pressure termination Macroreentrant Roof 1 RF lesion 2 No Macroreentrant Roof Spontaneous Macroreentrant Roof 1 RF lesion 3 No Macroreentrant Roof Linear lesion Macroreentrant Roof Linear lesion 7 No Focal Mitral isthmus 4 RF lesions Macroreentrant Septum 2 RF lesions 10 No Macroreentrant Lateral RA 1 RF lesion Macroreentrant Mitral isthmus Linear lesion 4 Yes; after cardioversion, no further recurrence Macroreentrant CTI Linear lesion 2 No Macroreentrant Postinferior LA Spontaneous 6 Yes; after cardioversion, no further recurrence Macroreentrant Roof Linear lesion 6 No Macroreentrant Mitral isthmus Linear lesion Focal Septum Spontaneous 10 No Focal Base of LA appendage 1 RF lesion Macroreentrant Roof 2 RF lesions Macroreentrant Mitral isthmus 8 RF lesions 3 No Macroreentrant Mitral isthmus 1 RF lesion mechanism was focal. The most common AT (11 of 33; 33%) was a macroreentrant circuit involving the mitral isthmus (Figures 4 and 5). The next most common location for an AT was a macroreentrant circuit involving the roof (9 of 33; 27%). An AT that involved the septum was the third most common (5 of 33; 15%). There were 2 right-sided ATs, 1 involving the lateral RA (Figure 6) and 1 involving the CTI. AT Ablation Of the 33 mapped ATs, 7 terminated during entrainment maneuvers or stopped spontaneously and were not reinducible. Radiofrequency energy was used to ablate 26 ATs (Figures 2 and 4), including 2 for which full activation maps were not created. With radiofrequency energy or catheter pressure, 25 (96%) of 26 ATs were terminated successfully. When radiofrequency failed to terminate the tachyarrhythmia,

6 Patel et al Atrial Tachycardia After AF Ablation 19 Figure 5. A modified right posterior oblique projection (left) and anteroposterior (AP) projection of a LA geometry with an activation map of a mitral isthmus AT. Extensive scar (gray) is shown because this patient had undergone a previous surgical maze procedure followed by a catheter PV isolation procedure before presenting with incessant AT and a tachycardia-induced cardiomyopathy. Inset, Fractionated activity (ABL) on the anterior LA during atrial diastole where successful RF application was delivered terminating the AT. Again, note that instead of placing a traditional mitral isthmus line posteriorly, chamber mapping revealed a constrained region anteriorly, at which site conduction block was easy to achieve. ibutilide was used to attain sinus rhythm. One patient (patient 7) developed AF intraprocedurally after 2 ATs were successfully ablated and then underwent electrical cardioversion to achieve sinus rhythm. Follow-Up There were no complications in any of the patients undergoing AT ablation, including hematomas, pericardial tamponade, or conduction system damage requiring a permanent pacemaker. After 1.1 procedures per patient and a mean follow-up of months (range, 2 to 14 months), 13 (76%) of 17 patients were free of AT (and AF) recurrences. Figure 6. A, For the same patient shown in Figure 5, of the NavX-based CS (mesh), LA (solid) and RA (mesh) atrial geometries are shown in left anterior oblique (left) and posteroanterior (right) projections. The white dots seen on the LA depict where the mitral isthmus AT was terminated at the critical isthmus. B, After termination of this mitral isthmus AT, a second AT was present. A right lateral projection of the LA and RA geometries is shown with an activation map of this posterior RA focal microreentrant AT. During entrainment, the PPI TCL at this site but was not equal as one paced further from this location. Ablation at this site (white dot) eliminated this residual AT. SN indicates sinus node location. After electric cardioversion, 3 of the patients have had no further clinical recurrences on antiarrhythmic medications. The final patient had recurrent AT even after cardioversion and is awaiting another ablation procedure. Discussion Iatrogenic ATs have been reported after either surgical or catheter ablation of AF After ablation of paroxysmal AF (wherein the initial ablation procedure is predominantly directed to PV isolation), the mechanism of AT is virtually always focal, originating from reconnected PVs. 10 However, ablation of persistent AF typically involves LA, and sometimes RA, substrate ablation (linear lesions and ablation of sites of complex fractionated electrograms) beyond simple PV isolation. Here, we report a novel approach to mapping these postablation scar-related ATs by using a combination of activation mapping with a multielectrode array mapping catheter and targeted entrainment mapping. The mechanisms of postablation ATs depend to a large extent on the ablation performed in the index procedure. A segmental approach to PV isolation, confirmed with a circular mapping catheter, resulted in most postablation ATs being of a focal mechanism from reconnected PV ostia. 10,12 Anatomic approaches have been associated with a much higher prevalence of macroreentrant tachycardias around the mitral isthmus or PV ostia. 13,16,17 After a complex fractionated electrogram approach to AF ablation, Nadamanee et al 18 reported that 36% of patients had AT, with half having macroreentrant circuits and half having focal mechanisms. It stands to reason that the mechanisms of postablation AT are particularly variable in cases in which multiple strategies are used, as in the present series. The extent of ablation could even be unknown because either the initial strategy was surgical or several ablation procedures had previously been performed. Haïssaguerre et al 19 reported a 40% prevalence of postablation ATs in patients who had undergone catheter ablation of long-lasting persistent AF. Their initial AF ablation strategy included PV isolation, isolation of the superior vena cava, complex fractionated electrogram ablation, LA roof line, mitral isthmus line, CTI line, and CS isolation. The mechanisms of the ATs observed in this series were varied and

7 20 Circ Arrhythmia Electrophysiol April 2008 included focal mechanisms in the anterior LA, CS, LA appendage, and septum. 19 The same group reported anterior left AT in patients who had undergone PV isolation combined with LA roof and mitral isthmus lines but no previous anterior LA ablation. 20 Catheter ablation of left-sided ATs can be technically challenging. Previous studies evaluating left-sided ATs without prior LA ablation have used a combination of magnetic electroanatomic and entrainment mapping with reasonable success. 21,22 Similar approaches have been reported in series of post AF ablation ATs ,16 18 The usual strategy involves confirmation that the CTI is not part of the circuit and assurance of PV isolation, followed by entrainment mapping at the sites most commonly involved in ATs (septum, LA appendage, mitral isthmus, roof). Activation mapping can then be used as an adjunct when the above strategy is not successful. However, the most commonly used type of activation mapping (with magnetic electroanatomic mapping) is limited by a point-by-point acquisition process that is not always systematic, can be time consuming, and may miss small areas critical to the circuit. Detailed magnetic electroanatomic mapping may require 100 to 200 points, and each flutter circuit can be complex, involving multiple loops and figure-of-8 reentrant circuits. Noncontact mapping of left ATs, in association with AF, also has been described 23 ; however, the accuracy of this mapping system is limited by both the frequently dilated nature of the atrial chamber and the low electrogram voltage amplitudes. The penta-array catheter has been used to map postablation AT and to identify sources maintaining AF. 19,24,25 However, the present series is the first to report its use in activation mapping using an electroanatomic mapping system. This allowed us to perform multielectrode activation mapping and to rapidly create detailed activation maps with relative ease. Almost every map was created in 10 minutes, with some completed in 5 minutes. In particular, when the AT location or cycle length changed in the middle of the procedure, remapping could be repeated expediently. This stands in stark contrast to the point-to-point electroanatomic mapping typically performed with a standard mapping catheter. The other important advantage of activation mapping with this approach is the opportunity to identify critical isthmuses for these ATs, particularly for the macroreentrant variety. Shah and colleagues 26 reported a series of 16 post AF ablation ATs in which 73% involved a narrow, slowly conducting isthmus in the LA, usually involving the ridge between the left PVs and the LA appendage. When this isthmus was found, the AT usually could be terminated with 1 radiofreqency lesion; otherwise, long linear lesions (mitral isthmus or LA roof) lines had to be performed. With our technique, similar isthmuses can be identified. Figures 4 and 5 show mitral isthmus ATs for which activation mapping identified other areas of activation percolating through scars that could be targeted more easily for ablation. When they are found, a single ablation lesion can terminate the AT, thereby obviating the need for a linear lesion set. When so much ablation has already been performed as part of the previous ablation procedure(s), the ability to substantively limit the extent of ablation may reduce any chance of harm (eg, arterial Figure 7. Left AT also can occur during the index AF ablation procedure, particularly during ablation of persistent AF. In this patient with long-lasting persistent AF, the rhythm organized to AT after extensive ablation, including PV isolation, mitral isthmus ablation, and ablation at sites of complex fractionated atrial electrograms. A, With the penta-array catheter, activation mapping of the LA revealed an area of percolation of activity (white arrow) between the ablation lesions isolating the right inferior PV and targeting the complex fractionated electrograms in the LA just inferior to the right inferior PV. Entrainment from this site revealed a PPI TCL. B, An ablation lesion placed at this location (green dot) terminated and eliminated the flutter. injury or electric isolation of the LA appendage) and may reduce the potential for additional iatrogenic scar formation. 19,27 Our series had a 96% acute success rate; 25 of 26 postablation ATs were terminated with radiofrequency ablation or catheter pressure during the first procedure. Other series have reported similar success rates ranging from 88% to 100%. 10,12,13,16,19 Our recurrence rate (5 of 17; 29%) also was similar to other published studies. Recurrence rates in these series ranged from 0% to 47% with mean follow-up ranging from 2 to 16 months. 10,12,13,16,19 A higher rate of recurrence tended to occur in series with longer follow-up. The usefulness of this technique can extend beyond post AF ablation AT to any tachyarrhythmia in which the circuit is difficult to identify. During a staged ablation procedure to treat persistent AF, it is common for the rhythm to eventually organize to an AT percolating through areas that had been incompletely ablated or areas of chronic scarring. In these cases, the approach described in this study can be used similarly to rapidly identify and ablate isthmuses critical to the tachycardia circuits (Figure 7). In addition, although not specifically evaluated in this study, another approach to consider is multielectrode activation mapping during sinus rhythm to identify putative channels of activation. As previously demonstrated for ATs in the setting of surgically corrected congenital heart disease, systematic ablation of these channels can effectively eliminate clinical ATs. 28

8 Patel et al Atrial Tachycardia After AF Ablation 21 Study Limitations This study includes a relatively small cohort of patients. In addition, the follow-up has been based on symptomatic recurrence and periodic Holter monitoring. Although an invasive monitor would be more effective in ruling out asymptomatic recurrences, it should be noted that the 2:1 response frequently observed with these ATs typically renders the patient quite symptomatic as a result of the tachycardia. Furthermore, the possibility of asymptomatic atrial arrhythmia recurrence does not detract from the procedural efficacy in rapidly identifying and terminating the arrhythmias. Another important limitation of this approach is the possibility for the AT to either terminate or change mechanism during entrainment. However, by first performing activation mapping, we could minimize the number of entrainment attempts and thereby minimize the probability of termination. Indeed, termination during entrainment was observed for only 2 of the ATs evaluated in this study. Finally, it may be economically challenging to use the penta-array catheter in addition to the circular mapping catheter during routine clinical procedures as opposed to a limited number of clinical investigational cases as in this study. However, in our more recent experience, we have been able to perform the entire ablation procedure using just the penta-array catheter (without the circular catheter), including creating the LA-PV geometry, performing/verifying electric PV isolation, and mapping/ablating ATs. Alternatively, a circular mapping catheter could be used for mapping; although less effective at conforming to the cardiac anatomy than the penta-array catheter, it nonetheless provides a more rapid means for mapping than does point-to-point mapping with a standard quadripolar mapping catheter. Conclusions We report a technique to rapidly identify and eliminate postablation ATs with a high degree of success. In addition, the identification of critical isthmuses may reduce the extent and time needed for radiofrequency ablation. Future studies are needed to fully assess whether this technique may be applied to other scar-related ATs, including those in the setting of prior surgery for congenital heart disease and those in the presence of idiopathic atrial scar. Source of Funding This work was supported in part by the Deane Institute for Integrative Research in Atrial Fibrillation and Stroke. Disclosures Drs Reddy and Neuzil have received grant support from and served as consultants to Biosense-Webster, Inc, and St. Jude Medical, Inc. Dr d Avila has served as a consultant to St. Jude Medical, Inc. S. Kim is an employee of St. Jude Medical, Inc. The remaining authors report no potential conflicts. References 1. Cox JL, Schuessler RB, Boineau JP. The surgical treatment of atrial fibrillation III: development of a definitive surgical procedure. J Thorac Cardiovasc Surg. 1991;101: Haissaguerre M, Jais P, Shah DC, Takahashi A, Hocini M, Quiniou G, Garrigue S, Le Mouroux A, Le Metayer P, Clementy J. Spontaneous initiation of atrial fibrillation by ectopic beats originating in the pulmonary veins. N Engl J Med. 1998;339: Haïssaguerre M, Shah DC, Jaïs P, Hocini M, Yamane T, Deisenhofer I, Chauvin M, Garrigue S, Clémenty J. Electrophysiologic breakthroughs from the left atrium to the pulmonary veins. Circulation. 2000;102: Haïssaguerre M, Jaïs P, Shah DC, Garrigue S, Takahashi A, Lavergne T, Hocini M, Peng JT, Roudaut R, Clémenty J. Electrophysiological end point for catheter ablation of atrial fibrillation initiated from multiple pulmonary venous foci. Circulation. 2000;101: Pappone C, Rosanio S, Oreto G, Tocchi M, Gugliotta F, Vicedomini G, Salvati A, Dicandia C, Mazzone P, Santinelli V, Gulletta S, Chierchia S. Circumferential radiofrequency ablation of pulmonary vein ostia: a new anatomic approach for curing atrial fibrillation. Circulation. 2000;102: Oral H, Scharf C, Chugh A, Hall B, Cheung P, Good E, Veerareddy S, Pelosi F Jr, Morady F. Catheter ablation for paroxysmal atrial fibrillation: segmental pulmonary vein ostial ablation versus left atrial ablation. Circulation. 2003;108: Usui A, Inden Y, Mizutani S, Takagi Y, Akita T, Ueda Y. Repetitive atrial flutter as a complication of the left-sided simple maze procedure. Ann Thorac Surg. 2002;73: Villacastín J, Pérez-Castellano N, Moreno J, González R. Left atrial flutter after radiofrequency catheter ablation of focal atrial fibrillation. J Cardiovasc Electrophysiol. 2003;14: Oral H, Knight BP, Morady F. Left atrial flutter after segmental ostial radiofrequency catheter ablation for pulmonary vein isolation. Pacing Clin Electrophysiol. 2003;26: Gerstenfeld EP, Callans DJ, Dixit S, Russo AM, Nayak H, Lin D, Pulliam W, Siddique S, Marchlinski FE. Mechanisms of organized left atrial tachycardias occurring after pulmonary vein isolation. Circulation. 2004; 110: Kobza R, Hindricks G, Tanner H, Schirdewahn P, Dorszewski A, Piorkowski C, Gerds-Li JH, Kottkamp H. Late recurrent arrhythmias after ablation of atrial fibrillation: incidence, mechanisms, and treatment. Heart Rhythm. 2004;1: Chugh A, Oral H, Lemola K, Hall B, Cheung P, Good E, Tamirisa K, Han J, Bogun F, Pelosi F, Morady F. Prevalence, mechanisms, and clinical significance of macroreentrant atrial tachycardia during and following left atrial ablation for atrial fibrillation. Heart Rhythm. 2005;2: Deisenhofer I, Estner H, Zrenner B, Schreieck J, Weyerbrock S, Hessling G, Scharf K, Karch MR, Schmitt C. Left atrial tachycardia after circumferential pulmonary vein ablation for atrial fibrillation: incidence, electrophysiological characteristics, and results of radiofrequency ablation. Europace. 2006;8: Haissaguerre M, Jais P, Hocini M, Sanders P, Hsu L-F, Scavee C, Weerasooriya R, Shah DC, Garrigue S, Clementy J. Macro-reentrant atrial flutter following ablation of pulmonary veins, tricuspid and mitral isthmuses. Pacing Clin Electrophysiol. 2003;26:970. Abstract. 15. Sra J, Hauck J, Krum D, Schweitzer J. Three-dimensional right atrial geometry construction and catheter tracking using cutaneous patches. J Cardiovasc Electrophysiol. 2003;14: Mesas CE, Pappone C, Lang CC, Gugliotta F, Tomita T, Vicedomini G, Sala S, Paglino G, Gulletta S, Ferro A, Santinelli V. Left atrial tachycardia after circumferential pulmonary vein ablation for atrial fibrillation: electroanatomic characterization and treatment. J Am Coll Cardiol. 2004;44: Pappone C, Manguso F, Vicedomini G, Gugliotta F, Santinelli O, Ferro A, Gulletta S, Sala S, Sora N, Paglino G, Augello G, Agricola E, Zangrillo A, Alfieri O, Santinelli V. Prevention of iatrogenic atrial tachycardia after ablation of atrial fibrillation: a prospective randomized study comparing conventional pulmonary vein ablation with a modified approach. Circulation. 2004;110: Nademanee K, McKenzie J, Kosar E, Schwab M, Sunsaneewitayakul B, Vasavakul T, Khunnawat C, Ngarmukos T. A new approach for catheter ablation of atrial fibrillation: mapping of the electrophysiologic substrate. J Am Coll Cardiol. 2004;43: Haïssaguerre M, Hocini M, Sanders P, Sacher F, Rotter M, Takahashi Y, Rostock T, Hsu LF, Bordachar P, Reuter S, Roudaut R, Clémenty J, Jaïs P. Catheter ablation of long-lasting persistent atrial fibrillation: clinical outcome and mechanisms of subsequent arrhythmias. J Cardiovasc Electrophysiol. 2005;16: Jaïs P, Sanders P, Hsu LF, Hocini M, Sacher F, Takahashi Y, Rotter M, Rostock T, Bordachar P, Reuter S, Laborderie J, Clémenty J, Haïssaguerre M. Flutter localized to the anterior left atrium after catheter ablation of atrial fibrillation. J Cardiovasc Electrophysiol. 2006;17:

9 22 Circ Arrhythmia Electrophysiol April Jais P, Shah DC, Haissaguerre M, Hocini M, Peng JT, Takahashi A, Garrigue S, Le Metayer P, Clementy J. Mapping and ablation of left atrial flutters. Circulation. 2000;101: Ouyang F, Ernst S, Vogtmann T, Goya M, Volkmer M, Schaumann A, Bänsch D, Antz M, Kuck KH. Characterization of reentrant circuits in left atrial macroreentrant tachycardia: critical isthmus block can prevent atrial tachycardia recurrence. Circulation. 2002;105: Saksena S, Skadsberg ND, Rao HB, Filipecki A. Biatrial and threedimensional mapping of spontaneous atrial arrhythmias in patients with refractory atrial fibrillation. J Cardiovasc Electrophysiol. 2005;16: Haissaguerre M, Hocini M, Sanders P, Takahashi Y, Rotter M, Sacher F, Rostock T, Hsu LF, Jonsson A, O_Neill MD, Bordachar P, Reuter S, Rouda R, Clementy J, Jais P. Localized sources maintaining atrial fibrillation organized by prior ablation. Circulation. 2006;113: Sanders P, Hsu LF, Jais P, Hocini M, Scavee C, Pasquie JL, Takahashi Y, Rotter M, Sacher F, Garrigue S, Clementy J, Haissaguerre M. Novel insights in focal atrial tachycardia using high density localized mapping [abstract]. Heart Rhythm. 2004;1:S Shah D, Sunthorn H, Burri H, Gentil-Baron P, Pruvot E, Schlaepfer J, Fromer M. Narrow, slow-conducting isthmus dependent left atrial reentry developing after ablation for atrial fibrillation: ECG characterization and elimination by focal RF ablation. J Cardiovasc Electrophysiol. 2006;17: Takahashi Y, Jais P, Hocini M, Sanders P, Rotter M, Rostock T, Sacher F, Jais C, Clementy J, Haissaguerre M. Acute occlusion of the left circumflex coronary artery during mitral isthmus linear ablation. J Cardiovasc Electrophysiol. 2005;16: Nakagawa H, Shah N, Matsudaira K, Overholt E, Chandrasekaran K, Beckman KJ, Spector P, Calame JD, Rao A, Hasdemir C, Otomo K, Wang Z, Lazzara R, Jackman WM. Characterization of reentrant circuit in macroreentrant right atrial tachycardia after surgical repair of congenital heart disease: isolated channels between scars allow focal ablation. Circulation. 2001;103: CLINICAL PERSPECTIVE Catheter ablation is increasingly being performed to treat drug-refractory, symptomatic atrial fibrillation (AF). One of the more troubling aspects of AF ablation, particularly extensive atrial ablation for persistent AF, is the appearance of atrial tachycardias (ATs) after AF ablation. These arrhythmias often have a metronomic 2:1 ventricular response, typically are difficult to manage medically, and frequently recur after cardioversion. On the other hand, ATs appear to reflect a more organized atrial substrate on the continuum between AF and sinus rhythm; successful ablation of the AT is often the last hurdle to overcome before sinus rhythm is achieved. However, there is no accepted systematic approach to mapping and ablating these arrhythmias. The present article proposes and evaluates a novel method consisting of 4 steps: use of a 20-pole penta-array catheter for rapid mapping of the chamber during the rhythm of interest, analysis of the patterns of atrial activation to identify wave fronts of electrical propagation, targeted entrainment at putative channels, and catheter ablation at these isthmuses. The process is useful because it can be performed rapidly and repetitively, especially because these ATs are notoriously transitory and polymorphous. The method also allows identification of critical isthmuses required for macroreentrant AT that may have heretofore gone unnoticed; these areas can then be targeted to terminate the arrhythmia with relatively few radiofrequency applications. In this study, when radiofrequency ablation was attempted, ablation of these ATs resulted in a 95% success rate, and the acute success was durable in follow-up.