Macroreentrant Atrial Tachycardia Research Articles

Right atrial macroreentrant tachycardia, around the scar due to long-term continuous tachycardia, in two patients without prior atrial sturgery.

Right atrial macroreentrant tachycardia, around the scar due to long-term continuous tachycardia, in two patients without prior atrial sturgery.

A case of left atrial macro-reentrant tachycardia involving the myocardium of the coronary sinus.

A case of left atrial macro-reentrant tachycardia involving the myocardium of the coronary sinus.

Catheter ablation of atrial fibrillation originating from extrapulmonary vein areas: Taipei approach

A P o p t t d f i j p e w t l f b a r ( c t w r ntroduction he pulmonary veins (PVs) are a dominant source of ecopic activity initiating atrial fibrillation (AF). We and thers have demonstrated that extra-PV ectopic activity ould initiate AF, and elimination of ectopic activity can ure this specific group of patients with AF. The Boreaux group demonstrated that extensive ablation of exra-PV areas after isolation of all four PVs can convert hronic AF to focal or macroreentrant atrial tachycardias, nd further elimination of these atrial tachycardias could aintain sinus rhythm in approximately 90% of patients ith chronic AF. Furthermore, we also showed initiation of F without any initiating PV ectopy, presumably due to eentry. Therefore, we must consider the important role of oth ectopy and reentry from extra-PV areas in the initiation nd maintenance of AF, not only in patients with paroxysal AF but also those with chronic AF. This article describes the current state of mapping and blation techniques, and the safety and efficacy of catheter blation for extra-PV AF in patients with paroxysmal and hronic AF.

AB21-5: 3-D-CT / -MRI integration into electroanatomical mapping (Carto Merge®) for ablation of Atrial Macro-Reentrant Tachycardias (AMRT) after surgical repair of Congenital Heart Disease (CHD)

AB21-5: 3-D-CT / -MRI integration into electroanatomical mapping (Carto Merge®) for ablation of Atrial Macro-Reentrant Tachycardias (AMRT) after surgical repair of Congenital Heart Disease (CHD)

AB18-3: Increased inducibility of macroreentrant left atrial tachycardia with addition of autonomic ganglionated plexi ablation to pulmonary vein antrum isolation

AB18-3: Increased inducibility of macroreentrant left atrial tachycardia with addition of autonomic ganglionated plexi ablation to pulmonary vein antrum isolation

A simple algorithm for defining the mechanism and the chamber of origin in atrial tachycardias

Introduction Although macroreentrant atrial tachycardia (MRAT) and focal atrial tachycardia (FAT) can be successfully cured by catheter ablation, the proper diagnosis and treatment of these arrhythmias can still be challenging. Aim The objective of this study is to develop an algorithm allowing rapid diagnosis of the mechanism and the chamber of origin of atrial tachycardia based on intracardiac catheter recordings from the right atrium and the coronary sinus (CS). Methods A 2-stepped algorithm was designed: (1) The time of biatrial activation expressed as a percentage of the tachycardia cycle length served to discriminate FAT from MRAT. (2) In FAT, the direction of activation of the CS catheter and the earliest atrial activation were used to define the chamber of origin. In MRAT, the time of right atrium activation was determined or entrainment was used at different sites. Thirty-two intracardiac recordings were reviewed off-line after the algorithm by 4 electrophysiologists blinded to the mechanism and the chamber of origin. The results of their analysis were compared with the intraoperative diagnosis. Results The algorithm correctly identified 11 (100%) of 11 FATs and 19 (90.4%) of 21 MRATs. The site of origin was correctly identified in 8 (72.7%) of 11 FATs and in 20 of 21 (95.2%) MRATs. The site of origin was misidentified in 3 FATs, all arising from the CS ostium. Conclusions This algorithm allows rapid discrimination between FAT and MRAT. The chamber of origin is detected with a high accuracy in MRAT. However, the earliest atrial activation taken as an isolated event is not a good predictor for the chamber of origin in FAT arising from the ostium of the CS.

Entrainment mapping for rapid distinction of left and right atrial tachycardias

Distinguishing left from right atrial tachycardia is a critical step for guiding ablation. The purpose of this study was to develop and validate a simple algorithm predicting the location of macroreentrant atrial tachycardia (AT) circuits from limited entrainment mapping in right atrium (RA) and coronary sinus (CS). In 180 patients with organized reentrant AT, entrainment was performed at the high RA, proximal CS, and distal CS. The difference between the postpacing interval (PPI) and tachycardia cycle length (TCL) was calculated at each site. The location of the AT reentrant circuit was determined by mapping and ablation. An algorithm predicting AT regions was developed from 104 ATs in the first 90 patients (group I) and prospectively evaluated in a validation cohort of 106 ATs in the second 90 patients (group II). In group I, PPI-TCL difference <50 or >50 ms at the high RA distinguished RA from LA reentrant circuits. For RA tachycardias, PPI-TCL difference at the proximal CS distinguished common flutter from lateral RA circuits. For LA circuits, PPI-TCL difference at the proximal and distal CS distinguished perimitral reentry from reentry involving the right pulmonary veins and septum. In group II, an algorithm based on PPI-TCL difference >50 or <50 ms at the high RA, proximal CS, or distal CS had sensitivity of 94%, specificity of 88%, and predictive accuracy of 93% for predicting the successful ablation region. Limited entrainment from sites accessible from the RA can expeditiously suggest the AT location to guide more detailed mapping and potentially avoid unnecessary transseptal punctures in some patients.

Ablation of Nonautomatic Focal Atrial Tachycardia in Children and Adults with Congenital Heart Disease

Nonautomatic focal atrial tachycardia (NAFAT) has been characterized in adults with structurally normal hearts. This article characterizes NAFAT in a population of patients with complex congenital heart disease. Electrophysiologic and electroanatomic mapping data and acute outcomes were reviewed in patients undergoing mapping and ablative procedures for atrial tachycardia at Children's Hospital, Boston, between January 1999 and December 2003. Twenty-two NAFAT foci were identified in 17 patients out of 216 patients studied. Fourteen of these 17 patients had congenital heart disease. The average age of the patients with a NAFAT mechanism was 27 years and there was no gender predilection. The presumptive diagnosis based on clinical grounds and surface ECG assessment in 11 of 17 patients with NAFAT was atrial flutter. None of the 17 patients were suspected of having a NAFAT mechanism by noninvasive assessment. Four of the 10 patients had both NAFAT and macroreentrant atrial tachycardias. NAFAT cycle lengths varied widely (200-680 ms) between patients. Sixteen of the 22 NAFAT foci were mapped to the anatomic right atrium (RA). Acute ablative success was achieved in 17 out of 22 foci (77%). NAFAT is relatively uncommon in a pediatric tertiary care setting, and in that setting occurs most often in adults with congenital heart disease. NAFAT is indistinguishable from other forms of atrial tachycardia by noninvasive means and can mimic other forms of atrial tachycardia on electrocardiogram. The foci were predominantly found in the RA and were, in most cases, acutely amenable to catheter ablation therapy.

Radiofrequency catheter ablation within the coronary sinus eliminates a macro-reentrant atrial tachycardia: Importance of mapping in the coronary sinus

We describe a patient who underwent radiofrequency (RF) catheter ablation of symptomatic atrial fibrillation. After left atrial (LA) catheter ablation and pulmonary vein isolation, a macro-reentrant atrial tachycardia (AT) with a critical isthmus at the mitral isthmus was induced by incremental atrial pacing from the coronary sinus. Extensive RF energy applications from endocardial sites using ablation catheters with 4 mm- and 8 mm- tips resulted in no discrete potentials being recorded from the endocardial sites of the isthmus, but the tachycardia could not be terminated. However, discrete potentials were recorded within the CS, and epicardial RF energy applications from the CS eliminated the tachycardia. Thus, mapping in the CS is useful for detecting residual conduction at epicardial sites along the mitral isthmus. RF catheter ablation within the CS should be considered when no distinct electrograms are recorded after extensive ablation from the endocardial sites and when distinct electrograms are recorded within the CS.

Left Atrial Tachycardia After Pulmonary Vein Isolation for Atrial Fibrillation

Left atrial tachycardia (AT) has been reported to occur after pulmonary vein isolation (PVI) for the treatment of atrial fibrillation (AF). We treated 3 patients who developed AT of different mechanisms following PVI. In case 1, focal AT originating at the ostium of the left superior PV was demonstrated and focal radiofrequency ablation was performed at the breakthrough point at the ostium of the left superior PV terminated the AT. In case 2, AT was shown to be counterclockwise macroreentrant AT around the left inferior PV through the conduction gap of the left sided posterior wall for which linear ablation was performed between left superior and inferior PVs. Focal ablation at the conduction gap terminated the AT. In case 3, a macroreentrant AT propagating around the mitral annulus was demonstrated and linear ablation between left inferior pulmonary vein and mitral annulus (mitral isthmus) terminated the AT.

Electrophysiological Findings During Ablation of Persistent Atrial Fibrillation With Electroanatomic Mapping and Double Lasso Catheter Technique

Pulmonary veins (PVs) can be completely isolated with continuous circular lesions (CCLs) around the ipsilateral PVs. However, electrophysiological findings have not been described in detail during ablation of persistent atrial fibrillation (AF). Forty patients with symptomatic persistent AF underwent complete isolation of the right-sided and left-sided ipsilateral PVs guided by 3D mapping and double Lasso technique during AF. Irrigated ablation was initially performed in the right-sided CCLs and subsequently in the left-sided CCLs. After complete isolation of both lateral PVs, stable sinus rhythm was achieved after AF termination in 12 patients; AF persisted and required cardioversion in 18 patients. In the remaining 10 patients, AF changed to left macroreentrant atrial tachycardia in 6 and common-type atrial flutter in 4 patients. All atrial tachycardias were successfully terminated during the procedure. Atrial tachyarrhythmias recurred in 15 of 40 patients at a median of 4 days after the initial ablation. A repeat ablation was performed at a median of 35 days after the initial procedure in 14 patients. During the repeat study, recovered PV conduction was found in 13 patients and successfully abolished by focal ablation of the conduction gap of the previous CCLs. After a mean of 8+/-2 months of follow-up, 38 (95%) of the 40 patients were free of AF. In patients with persistent AF, CCLs can result in either AF termination or conversion to macroreentrant atrial tachycardia in 55% of the patients. In addition, recovered PV conduction after the initial procedure is a dominant finding in recurrent atrial tachyarrhythmias and can be successfully abolished.

Reentrant and nonreentrant focal left atrial tachycardias occur after pulmonary vein isolation

Both focal and macroreentrant atrial tachycardia (ATs) can occur after pulmonary vein (PV) isolation for treatment of atrial fibrillation (AF). We report the response to pacing and pharmacologic maneuvers performed in patients with stable focal ATs after segmental PV isolation. The purpose of this study was to determine the mechanism of focal ATs occurring after PV isolation. Patients with persistent left AT after cessation of antiarrhythmic drug therapy presented for mapping and ablation. Electroanatomic mapping during AT was performed. Entrainment was performed from multiple right and left atrial sites. Single-beat resetting was performed. Adenosine was infused intravenously to determine the effect on the tachycardia. Five patients (3 men and 2 women; age 65 +/- 10 years) had focal left AT that persisted in response to pacing maneuvers. Four patients had ATs (cycle length 265 +/- 18 ms) that demonstrated focal areas of early activation at the septal aspect of the right lower (3 patients) or right upper (1 patient) PV ostium. Resetting demonstrated a flat-plus increasing curve in two patients. Adenosine was infused with transient AV block and no change to the tachycardia cycle length in three patients. Tachycardias were entrained from multiple left atrial sites. Recordings from the ablation catheter at the critical isthmus typically demonstrated mid-diastolic or long fractionated potentials. One tachycardia with a longer and more variable cycle length (480-598 ms) did not demonstrate fusion during pacing from distant sites. Persistent focal left ATs may occur after segmental PV isolation. Many of these tachycardias are caused by a focal reentrant circuit located at the PV ostium; however, focal nonreentrant rhythms also may occur.

Catheter Ablation of Long‐Lasting Persistent Atrial Fibrillation: Critical Structures for Termination

The relative contributions of different atrial regions to the maintenance of persistent atrial fibrillation (AF) are not known. Sixty patients (53 +/- 9 years) undergoing catheter ablation of persistent AF (17 +/- 27 months) were studied. Ablation was performed in a randomized sequence at different left atrial (LA) regions and comprised isolation of the pulmonary veins (PV), isolation of other thoracic veins, and atrial tissue ablation targeting all regions with rapid or heterogeneous activation or guided by activation mapping. Finally, linear ablation at the roof and mitral isthmus was performed if sinus rhythm was not restored after addressing the above-mentioned areas. The impact of ablation was evaluated by the effect on the fibrillatory cycle length in the coronary sinus and appendages at each step. Activation mapping and entrainment maneuvers were used to define the mechanisms and locations of intermediate focal or macroreentrant atrial tachycardias. AF terminated in 52 patients (87%), directly to sinus rhythm in 7 or via the ablation of 1-6 intermediate atrial tachycardias (total 87) in 45 patients. This conversion was preceded by prolongation of fibrillatory cycle length by 39 +/- 9 msec, with the greatest magnitude occurring during ablation at the anterior LA, coronary sinus and PV-LA junction. Thirty-eight atrial tachycardias were focal (originating dominantly from these same sites), while 49 were macroreentrant (involving the mitral or cavotricuspid isthmus or LA roof). Patients without AF termination displayed shorter fibrillatory cycles at baseline: 130 +/- 14 vs 156 +/- 23 msec; P = 0.002. Termination of persistent AF can be achieved in 87% of patients by catheter ablation. Ablation of the structures annexed to the left atrium-the left atrial appendage, coronary sinus, and PVs-have the greatest impact on the prolongation of AF cycle length, the conversion of AF to atrial tachycardia, and the termination of focal atrial tachycardias.

Scar-related right atrial macroreentrant tachycardia in patients without prior atrial surgery: Electroanatomic characterization and ablation outcome

Few descriptions of right atrial macroreentrant atrial tachycardia involving regions of spontaneous "scar" have been reported. We describe the electrocardiographic, electrophysiologic, and electroanatomic characteristics of an unusual RA macroreentrant atrial tachycardia in eight patients with spontaneous RA scarring. Eight of 286 patients with macroreentrant atrial tachycardia treated with radiofrequency ablation had RA spontaneous scarring and underwent conventional electrophysiologic studies and electroanatomic mapping. Eight patients (age 53 +/- 12 years) had symptoms for 58 +/- 62 months and had not responded to 2.5 +/- 0.8 antiarrhythmic drugs and 1.0 +/- 0.9 DC cardioversions. All patients had overall normal systolic function, and five had mild atrial enlargement. Scarring was present in the posterolateral wall extending from the crista terminalis toward the tricuspid annulus. The proportion of RA classified as scar was 31% +/- 14% (range 11%-46%). Stable circuits were around scar in seven patients, through a "channel" within the scar in four, and typical cavotricuspid isthmus-dependent flutter in five. Radiofrequency ablation sites included the cavotricuspid isthmus; between the inferior vena cava, superior vena cava, or crista terminalis and scar; or a channel in the scar. ECG morphology of the RA free wall tachycardias varied, depending upon whether cavotricuspid isthmus block was present. Radiofrequency ablation of all inducible circuits was successful in six patients and of all clinical circuits in seven. At follow-up of 20 +/- 13 months, six patients are free from macroreentrant atrial tachycardia, one has infrequent nonsustained macroreentrant atrial tachycardia, and one is controlled with previously ineffective medication. Five had sinus node dysfunction requiring permanent pacemaker implant. Extensive spontaneous scarring of the RA is an unusual cause of macroreentrant atrial tachycardias, both cavotricuspid isthmus dependent and independent in the same patient. Radiofrequency ablation is an effective treatment. Sinus node dysfunction requiring permanent pacemaker is common. The cause is unknown.

Mechanisms of Right Atrial Tachycardia Occurring Late After Surgical Closure of Atrial Septal Defects

Postatriotomy atrial tachycardia ablation. In patients without structural heart disease, the most frequently occurring AT is the common atrial flutter. In patients with repaired congenital heart disease other mechanisms of AT may occur, due to the presence of an atriotomy that can provide a substrate for reentry. The aim of the present study was to identify the mechanisms of atrial tachycardia (AT) occurring late after atrial septum defect (ASD) repair, with the help of a three-dimensional electroanatomical mapping system. Twenty-two consecutive patients presenting with AT underwent complete electroanatomic mapping (CARTO, Biosense Webster, Diamond Bar, CA) of spontaneously occurring and inducible right ATs. Complete maps of 26 ATs were obtained. Three tachycardia mechanisms were identified: single-loop macroreentrant atrial tachycardia (MAT) (n=7), double-loop MAT (n=18), and focal AT (n=1). In all MATs, protected isthmuses were identified as the electrophysiological substrate of the arrhythmia, most frequently the cavotricuspid isthmus (CTI) (n=24), and a gap between the inferior vena cava and a line of double potentials (n=11). A mean number of 13.5+/-2.1 radiofrequency applications were delivered to transect these critical parts of the circuit. During a follow-up of 25+/-16 months the RF ablation was acutely successful in all patients. Thirteen patients (59%) had an early recurrence of MAT and needed an additional ablation procedure. One of those patients needed two additional ablation procedures. Three-dimensional electroanatomic mapping is useful to identify postsurgical AT mechanisms; the CTI isthmus is involved in 92% MAT, and if the right atrial free wall (RAFW) abnormal tissue related to surgical scar is present this substrate contributes to the MAT circuit.

Prevalence, mechanisms, and clinical significance of macroreentrant atrial tachycardia during and following left atrial ablation for atrial fibrillation

The purpose of this study was to determine the prevalence and clinical significance of macroreentrant atrial tachycardia (AT) after left atrial (LA) circumferential ablation for atrial fibrillation (AF). Linear ablation for AF may result in macroreentrant AT. Three hundred forty-nine patients (age 54 +/- 11 years) underwent LA circumferential ablation for AF (paroxysmal in 227). Ablation lines were created around the left-sided and right-sided pulmonary veins, with additional ablation lines in the posterior LA and mitral isthmus. If macroreentrant AT was observed acutely in the electrophysiology laboratory, it was not ablated. If an organized AT occurred during follow-up, the initial strategy was rate control. If AT persisted for > 3 to 4 months, catheter ablation was performed. Seventy-one patients (20%) had spontaneous or induced macroreentrant AT (cycle length 244 +/- 31 ms) in the electrophysiology laboratory following LA circumferential ablation. During follow-up, 85 patients (24%) experienced spontaneous AT (cycle length 238 +/- 35 ms) at a mean of 44 +/- 62 days following LA circumferential ablation. Among the 71 patients with macroreentrant AT acutely following LA circumferential ablation, 39 (55%) developed AT during follow-up. Among the 85 patients with AT during follow-up, the tachycardia remitted without a repeat ablation procedure in 28 patients (33%), most commonly within 5 months. Twenty-eight of the 349 patients (8%) underwent a repeat ablation procedure for AT. The critical isthmus was localized to the mitral isthmus in 17 of 28 patients (61%). Macroreentrant AT is a common form of proarrhythmia after LA circumferential ablation for AF. Because it may resolve spontaneously, ablation of AT should be deferred for several months.

Biatrial and Three‐Dimensional Mapping of Spontaneous Atrial Arrhythmias in Patients with Refractory Atrial Fibrillation

While atrial fibrillation (AF) initiation in the pulmonary veins has been well-studied, simultaneous biatrial and three-dimensional noncontact mapping (NCM) has not been performed. We hypothesized that these two techniques would provide novel information on triggers, initiation, and evolution of spontaneous AF and permit study of different AF populations. The origin of atrial premature beats (APBs), onset of spontaneous AF and its evolution were analyzed in 50 patients with AF in the presence or absence of structural heart disease (SHD) and in different AF presentations (group A: Persistent, group B: Paroxysmal). In 45 patients, spontaneous APBs in the right atrium (RA; n = 60) and left atrium (LA; n = 25) with similar regional distributions regardless of heart disease status were demonstrated. In total, 22 patients (44%) had > or =2 disparate regional origins. Biatrial regional foci were seen with equal frequency in patients with SHD (31%), without SHD (40%), in group A (32%), and in group B (36%). Biatrial mapping and NCM showed organized monomorphic atrial tachyarrhythmias arising in the RA (17), septum (17), or LA (21) and were classified as atrial flutter (RA = 34, LA = 8), macro-reentrant atrial tachycardia (RA = 1, LA = 3) or focal atrial tachycardia (RA = 2, LA = 7). Their regional distribution was more extensive in patients with SHD and persistent AF compared with patients without SHD or paroxysmal AF. Simultaneous biatrial tachycardias were observed only in group A patients and those with SHD. Simultaneous biatrial and NCM permits successful AF mapping in different AF populations and demonstrates a biatrial spectrum of spontaneous triggers and tachycardias. Organized monomorphic tachycardias with multiple unilateral or biatrial locations are commonly observed in human AF. Patients with heart disease or persistent AF have a more extensive distribution as well as simultaneous coexistence of multiple tachycardias during AF.

Catheter Ablation of Tachycardias After Undergoing a Surgical Atriotomy Using a Multipolar Electrode Catheter

A variety of supraventricular tachyarrhythmias may occur in patients after undergoing a surgical atriotomy. The purpose of this study was to characterize them and determine the role of conventional mapping. In 45 patients after a surgical atriotomy, 68 atrial tachyarrhythmias were observed. A conventional mapping system with a 20-pole electrode catheter used in the electrophysiological study detected 39 atrial tachycardias (ATs). Type 1 atrial flutter (AFL) was observed in 23 and reverse type 1 AFL in 4. AT was classified into 3 subgroups, namely, incisional macroreentrant AT (n=31), incisional focal AT (n=1) and non-incisional AT (n=7). In the patients with incisional macroreentrant AT after the standard right atriotomy, the 20-pole electrode catheter placed on the incision could easily record the entire sequence of the atrial activation. Successful catheter ablation was achieved in all patients with incisional reentrant AT. The ablation site of incisional reentrant AT was the isthmus between the incision and the superior vena cava cannulation scar in 4, between the incision and the inferior vena cava cannulation scar in 22, and the area at the septal incision in 3. The remaining 2 incisional ATs were left atrial AT and right atrial transincisional AT. The conventional mapping system is still very useful for making an electrophysiological diagnosis in patients after a standard right atriotomy.

Recovered Pulmonary Vein Conduction as a Dominant Factor for Recurrent Atrial Tachyarrhythmias After Complete Circular Isolation of the Pulmonary Veins

Atrial tachyarrhythmias (ATa) can recur after continuous circular lesions (CCLs) around the ipsilateral pulmonary veins (PVs) in patients with atrial fibrillation (AF). This study characterizes the electrophysiological findings in patients with and without ATa after complete PV isolation. Twenty-nine of 100 patients had recurrent ATa after complete PV isolation by use of CCLs during a mean follow-up of approximately 8 months. A repeat procedure was performed in 26 patients with ATa and in 7 volunteers without ATa at 3 to 4 months after CCLs. No recovered PV conduction was demonstrated in the 7 volunteers, whereas recovered PV conduction was found in 21 patients with recurrent ATa (right-sided PVs in 9 patients and left-sided PVs in 16 patients). The interval from the onset of the P wave to the earliest PV spike was 157+/-66 ms in the right-sided PVs and 149+/-45 ms in the left-sided PVs. During the procedure, PV tachycardia activated the atrium and resulted in atrial tachycardia (AT) in 10 patients. All conduction gaps were successfully closed with segmental RF ablation. After PV isolation, macroreentrant AT was induced and ablated in 3 patients. In the 5 patients without PV conduction, focal AT in the left atrial roof in 2 patients and non-PV foci in the left atrium in 1 patient were successfully abolished; in the remaining 2 patients, no ablation was performed because of noninducible arrhythmias. During a mean follow-up of approximately 6 months, 24 patients were free of ATa without antiarrhythmic drugs. In patients with recurrent ATa after CCLs, recovered PV conduction is a dominant finding in approximately 80% of patients and can be successfully eliminated by segmental RF ablation. Also, mapping and ablation of non-PV arrhythmias can improve clinical success.

Prevention of Iatrogenic Atrial Tachycardia After Ablation of Atrial Fibrillation

Circumferential pulmonary vein ablation (CPVA) is effective in curing atrial fibrillation (AF), but new-onset left atrial tachycardia (AT) is a potential complication. We evaluated whether a modified CPVA approach including additional ablation lines on posterior wall and the mitral isthmus would reduce the incidence of AT after PV ablation. A total of 560 patients (291 men, 52%; age, 56.5+/-7.3 years) entered the study; 280 were randomized to CPVA alone (group 1) and 280 to modified CPVA (group 2). The primary end point was freedom from AT after the procedure. In group 1, 28 patients (10%) experienced new-onset AT, and 41 (14.3%) experienced recurrent AF. In group 2, 11 patients (3.9%) experienced AT, and 36 (12.9%) had recurrent AF. Group 1 was more likely to experience AT than group 2 (P=0.005). Freedom from AF after ablation was similar in both groups (P=0.57). Among those in group 1, gap-related macroreentrant AT was documented in 23 of the 28 patients (82%), and focal AT was found in 5 (18%). In group 2, gap-related macroreentrant AT was found in 8 of the 11 patients (73%), and focal AT was seen in 3 (27%). Two patients in group 1 and 1 patient in group 2 had both AT and AF. The strongest predictor of AT was the presence of gaps (P<0.001). Modified CPVA is as effective as CPVA in preventing AF but is associated with a lower risk of developing incessant AT.