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Atrial tachycardias are commonly encountered in patients undergoing catheter ablation of persistent atrial fibrillation (AF). Unlike typical atrial flutter that can be readily recognized and ablated, these post-AF tachycardias can arise from a wide variety of locations and involve a multiplicity of mechanisms. Apart from diagnostic challenges, radiofrequency ablation to eliminate the tachycardias may require multiple approaches. In addition, specialized techniques such as epicardial and chemical ablation may be required for definitive treatment. This review describes the various mechanisms and approaches to mapping and ablation of these challenging tachycardias., (© 2021 Wiley Periodicals LLC.)

Purpose: The endpoint for radiofrequency catheter ablation (RFA) of cavo-tricuspid isthmus (CTI)-dependent atrial flutter (AFL) is complete conduction block along the CTI. The purpose of this study is to evaluate the utility of the temporal relationship between the P wave and the local atrial electrograms in determining complete CTI block., Methods: RFA of CTI was performed in 125 patients (age 63 ± 11 years). During pacing from the coronary sinus (CS), the intervals from the peak of the P wave (P peak ) in lead V 1 to the second component of the local atrial electrogram (A 2 ) along the ablation line (P peak -A 2 ) and from the end of the P wave (P end ) to A 2 (P end -A 2 ) were investigated before and after complete block in the first 100 patients (training set). In the next 25 patients (validation set), P peak -A 2 and P end -A 2 intervals were prospectively assessed to determine CTI block., Results: The mean P peak -A 2 and P end -A 2 immediately before complete block were - 15±24 and - 39±23 ms compared to 49 ± 17 and 21 ± 16 ms after CTI block (P < 0.0001). P peak -A 2 ≥ 20 ms and P end -A 2 ≥ 0 ms predicted CTI block with 98% sensitivity and 95% specificity and 96% sensitivity and 100% specificity, respectively. In the validation set, the positive and negative predictive values of P peak -A 2 ≥ 20 ms or P end -A 2 ≥ 0 ms were 100 and 96%, respectively. The diagnostic accuracy was 98%., Conclusions: During pacing from the CS, the temporal relationship between the P wave in lead V 1 and A 2 is a simple and reliable indicator of complete block during RFA of CTI-AFL.

Background: Large-tip (10 mm) catheters (LTCs) and open-irrigation-tip catheters (OITCs), both capable of creating large lesions, are more effective than conventional catheters for cavotricuspid isthmus (CTI) ablation. However, it is not clear whether complete CTI block can be achieved more efficiently using an LTC or an OITC. The purpose of this study was to compare the efficiency of radiofrequency catheter ablation (RFA) of the CTI using LTC versus OITC to eliminate atrial flutter (AFL)., Methods and Results: Sixty consecutive patients (age = 62 ± 10 years) with typical AFL were randomized to undergo RFA of CTI using an LTC (10 mm) or an OITC. If complete CTI block was not achieved by ≤30 minutes of RFA, patients were allowed to cross over to ablation with the other catheter. A 3-dimensional electroanatomical mapping system was used for catheter navigation only with the OITC. The mean duration of RFA to achieve CTI block in 50% of the patients was 6.8 ± 2.2 minutes with an LTC and 11.7 ± 2.7 minutes with an OITC (P = 0.001). After 30 minutes of RFA, CTI block was achieved in 26/30 (87%) and 25/30 patients (83%) using an LTC and an OITC, respectively (P = 1.0). After crossover, CTI block was achieved in 4/5 (80%) and in 4/4 patients (100%) with an LTC and OITC, respectively (P = 1.0). LTC was associated with a lower volume of intravenous fluid administration (388 ± 365 mL versus 865 ± 451 mL, P = 0.0001) and a trend for shorter procedure duration (95 ± 31 minutes versus 114 ± 50 minutes, P = 0.09) than the OITC. At 6 ± 3 months, 30/30 patients (100%) in the LTC and 27/30 patients (90%) in the OITC groups remained free from AFL, respectively (P = 0.24). Except for one inconsequential steam-pop during RFA with the OITC, there were no complications., Conclusions: Complete CTI block is achieved more rapidly using an LTC than an OITC, and with a similar clinical efficacy. , (© 2011 Wiley Periodicals, Inc.)

Depending on the ablation strategy, up to 30% to 50% of patients will develop an atrial tachycardia after undergoing radiofrequency catheter ablation of atrial fibrillation. This review discusses the mechanisms, mapping techniques, and catheter ablation of atrial tachycardias that occur after radiofrequency ablation of atrial fibrillation.

Background: The esophagus may be mobile during a left atrial (LA) ablation procedure for atrial fibrillation (AF)., Objective: The goal of the study was to determine whether the location of the esophagus is stable in patients undergoing a repeat LA ablation procedure., Methods: Forty-two patients underwent repeat LA ablation a mean of 7 +/- 2 months after the initial procedure. Cinefluoroscopic images of the esophagus during a barium swallow were recorded and the course of the esophagus was tagged on the 3D map. The position of the esophagus at the index and repeat procedure were compared., Results: At the index procedure, the esophagus was located near the left pulmonary veins (PVs) in 20 (48%), right PVs in 13 (31%), and at the mid LA in 9 (21%) patients. During the repeat procedure, the esophagus was found to be near the left PVs in 22 (52%), right PVs in 11 (26%), and at the mid LA in 9 patients (21%). In 35 of the 42 patients (83%), there was no change in the esophageal location, and in the remaining seven patients (17%), its position had shifted by > or =1 cm (range 1.0-4.0 cm)., Conclusions: In more than 80% of patients presenting for a repeat LA ablation procedure, the esophagus is in the same position relative to the PVs as during the initial procedure. Therefore, if radiofrequency ablation at a particular location was limited by the position of the esophagus, safe ablation at that site is unlikely to be feasible during a repeat procedure.

Background: Patients who have previously undergone ablation of atrial fibrillation may experience cavotricuspid isthmus (CTI)-dependent atrial flutter during follow-up. The effects of left atrial (LA) ablation on the characteristics of CTI-dependent flutter have not been described., Methods and Results: Fifteen patients underwent ablation of CTI-dependent flutter late after LA ablation of AF. The ECG, biatrial activation patterns, and LA voltage maps during flutter were analyzed. Thirty age- and gender-matched patients who underwent ablation of CTI-dependent flutter without prior LA ablation served as control subjects. Among the patients with prior LA ablation, mapping revealed counterclockwise activation around the tricuspid annulus in 12 of 15 patients (80%) and clockwise activation in 3 of 15 patients (20%). The flutter waves in the inferior leads were upright in 9 of the 15 patients (60%) with prior LA ablation and in none of the control subjects (P<0.001). The upright flutter waves in the inferior leads in patients with counterclockwise flutter corresponded to craniocaudal activation of the right atrial free wall. LA activation contributed little to the genesis of the flutter waves in these patients because of a significant reduction in bipolar LA voltage (0.44+/-0.20 versus 1.54+/-0.19 mV in patients with biphasic/negative flutter waves; P<0.001)., Conclusions: CTI-dependent flutter that occurs after LA ablation of atrial fibrillation often has atypical ECG characteristics because of altered LA activation. In patients presenting with atrial flutter after LA ablation, entrainment mapping should be performed at the CTI even if the ECG is uncharacteristic of CTI-dependent flutter.

Objectives: This study was designed to determine the prevalence and clinical significance of atrial flutter (AFL) that occurs during catheter ablation for atrial fibrillation (AF)., Background: Atrial flutter frequently occurs in patients with AF., Methods: Pulmonary vein isolation was performed in 133 consecutive patients (age 52 +/- 11 years) for paroxysmal (n = 112) or persistent (n = 21) AF. A clinical episode of AFL was documented in 40 of the 133 patients (30%). During the ablation procedure, AFL occurred in 86 patients (65%), either spontaneously (n = 36) or by rapid atrial pacing (n = 50), with AFL being typical in the majority (80%). Cavo-tricuspid isthmus ablation was performed in 28 of the 133 patients., Results: Among the 105 patients who did not undergo isthmus ablation, 25 patients (24%) were documented to have symptomatic AFL during a mean follow-up of 609 +/- 252 days. Among the clinical variables of age, gender, history of clinical AFL, ejection fraction, left atrial diameter, duration of AF, and occurrence of AFL during ablation, only a history of clinical AFL (p = 0.05) and occurrence of typical AFL during the ablation (p = 0.01) were independent predictors of symptomatic AFL during follow-up. The incidence of symptomatic AFL during follow-up was similar among patients who did and did not have long-term freedom from recurrent AF., Conclusions: In patients with AF who have either a history of AFL or an episode of typical AFL during an electrophysiologic study, symptomatic AFL is common after pulmonary vein isolation. Therefore, cavo-tricuspid isthmus ablation is appropriate during pulmonary vein isolation if AFL has been observed clinically or in the electrophysiology laboratory.

Objectives: The purpose of this prospective study was to compare radiofrequency catheter ablation of the cavotricuspid isthmus using a strictly anatomic approach to an approach guided by a bipolar voltage map to avoid high voltage zones in the cavotricuspid isthmus., Background: It is not clear whether local atrial electrogram amplitude influences the achievement of complete cavotricuspid isthmus block during radiofrequency catheter ablation for atrial flutter., Methods: Thirty-two patients with atrial flutter were randomized to cavotricuspid isthmus ablation using an anatomical approach (group I, 16 patients) or guided by a bipolar voltage map (group II, 16 patients). A 3-dimensional electroanatomic mapping system and an 8-mm-tip ablation catheter were used in all patients. With the anatomical approach, an ablation line was created in the cavotricuspid isthmus at a 6 o'clock position in the 45 degree left anterior oblique projection. During voltage-guided ablation, a high-density bipolar voltage map of the cavotricuspid isthmus was created, and then contiguous applications of radiofrequency energy were delivered to create an ablation line through the cavotricuspid isthmus sites with the lowest bipolar voltage., Results: Complete cavotricuspid isthmus conduction block was achieved in 100% of patients in each group. The mean maximum voltages along the line were 3.6 +/- 1.5 mV in group I, and 1.2 +/- 0.9 mV in group II (P < .01). Creating a high-density voltage map was associated with approximately 15-minute increase in the total procedure time (P = .2). During a mean follow-up of 177 +/- 40 days, there were no recurrences of atrial flutter in either group. There were no complications in either group., Conclusions: When cavotricuspid isthmus ablation for atrial flutter is performed with an 8-mm-tip catheter, complete block can be achieved in all patients regardless of local voltage. Ablation of high voltage zones is not associated with a higher recurrence rate. Therefore, anatomic ablation without voltage mapping is the preferred initial approach for cavotricuspid isthmus ablation.

Introduction: Acutely, when left atrial ablation is performed during atrial fibrillation (AF), the AF may persist and require cardioversion, or it may convert to sinus rhythm or to atrial tachycardia/flutter. The prevalence of these acute outcomes has not been described., Methods and Results: Left atrial ablation, usually including encirclement of the pulmonary veins, was performed during AF in 144 patients with drug-refractory AF. Conversion to sinus rhythm occurred in 19 patients (13%), to left atrial tachycardia in 6 (4%), and to atrial flutter in 6 (4%). In the 6 patients with a focal atrial tachycardia, the mean cycle length was 294 +/- 45 ms. The tachycardia arose in the left atrial roof in 3 patients, the left atrial appendage in 2, and the anterior left atrium in 1. In 3 of 6 patients, the focal atrial tachycardia originated in an area that displayed a relatively short cycle length during AF. In 6 patients, AF converted to macroreentrant atrial flutter with a mean cycle length of 253 +/- 47 ms, involving the mitral isthmus in 5 patients and the septum in 1 patient. All atrial tachycardias and flutters were successfully ablated with 1 to 15 applications of radiofrequency energy., Conclusion: When left atrial ablation is performed during AF, the AF may convert to atrial tachycardia or flutter in approximately 10% of patients. Focal atrial tachycardias that occur during ablation of AF may be attributable to driving mechanisms that persist after AF has been eliminated, whereas atrial flutter results from incomplete ablation lines.

Introduction: A corridor of double potentials along the ablation line has been recognized to be an indicator of complete cavotricuspid isthmus block. Isoproterenol is used to confirm cavotricuspid isthmus block, but the effects of isoproterenol on the double potential interval (DPI), either in the absence or presence of amiodarone, are unknown., Methods and Results: Thirty-two patients with isthmus-dependent atrial flutter underwent successful ablation of the cavotricuspid isthmus. The procedure was performed in the drug-free state in 23 patients, and 2 to 7 days after discontinuation of chronic amiodarone therapy in 9 patients. Electrograms recorded along the ablation line before and during isoproterenol infusion were analyzed after isthmus block was achieved. Double potentials were recorded along the entire ablation line upon achievement of complete isthmus block in all patients. The DPI in 9 patients treated with amiodarone was longer than in the other patients (147 +/- 32 msec vs 119 +/- 19 msec, P < 0.001). The DPI increased as the pacing cycle length shortened in patients treated with amiodarone, but not in the other patients. At all pacing cycle lengths, isoproterenol shortened the DPI to a greater extent in the patients treated with amiodarone than in the other patients., Conclusion: Amiodarone results in rate-dependent prolongation of the DPI during coronary sinus pacing after ablation of the cavotricuspid isthmus. Isoproterenol shortens the DPI despite the presence of complete isthmus block, and this effect is accentuated in the presence of amiodarone.

Large atrial electrogram amplitudes recorded in the cavotricuspid isthmus (CTI) may reflect thick atrial musculature. For this reason, in patients with atrial flutter, the efficacy of an application of conventional radiofrequency energy may be related to the amplitude of the local atrial electrogram. In 100 consecutive patients (mean age 59 +/- 13 years) with atrial flutter, contiguous applications of radiofrequency energy were delivered in the CTI. The criterion for complete CTI block was the presence of widely split double potentials (>110 ms) along the entire ablation line during pacing from the coronary sinus and posterolateral right atrium. The atrial electrogram amplitude was measured before and after applications of radiofrequency energy at sites of gaps in the ablation line. Complete CTI block was achieved in 90 (90%) of the 100 patients. The mean atrial electrogram amplitudes at gap sites where an application of radiofrequency energy did and did not result in complete block were 0.36 +/- 0.42 and 0.67 +/- 0.62 mV, respectively (P < 0.01). The positive and negative predictive values (for complete block) of a >/=50% decrease in electrogram amplitude after an application of radiofrequency energy were 100% and 35%, respectively. The mean atrial electrogram amplitude is larger at CTI sites where complete isthmus block cannot be achieved with conventional radiofrequency energy. The efficacy of conventional radiofrequency ablation may be improved by identifying areas in the CTI where the voltage is relatively low.

Introduction: The cavotricuspid isthmus can be ablated using an anatomic approach or an electrogram mapping approach in which sites at which there is a gap in the line of block are targeted. The aim of this study was to compare the anatomic and electrogram mapping approaches for creating a line of block in the cavotricuspid isthmus after an initial, unsuccessful anatomically directed ablation line., Methods and Results: The subjects of this study were 63 patients with isthmus-dependent atrial flutter in whom a single series of contiguous applications of radiofrequency energy guided by fluoroscopy in the cavotricuspid isthmus did not result in complete block. The patients were randomly assigned to additional ablation on an anatomic basis (n = 31) or guided by single potentials or narrowly split double potentials during coronary sinus pacing (n = 32). After every 15 applications of radiofrequency energy, the alternate approach was used until complete block was achieved. Before cross-over, complete block was achieved in 6 patients (19%) with the anatomic approach compared with 19 patients (59%) with the electrogram mapping approach (P < 0.005). The electrogram mapping approach also was more effective than the anatomic approach in achieving complete isthmus block after the first cross-over (72% vs 23%, P < 0.005) and after the second cross-over (80% vs 42%, P < 0.05)., Conclusion: When there is incomplete block after an initial series of applications of radiofrequency energy in the cavotricuspid isthmus, complete block is achieved more efficiently with an electrogram mapping approach than with an anatomic approach.

Introduction: Incidental left atrial appendage (LAA) isolation may occur during radiofrequency ablation of persistent atrial fibrillation (AF). The study aims to describe the mechanisms and long‐term thromboembolic risk related to incidental LAA isolation. Methods: Patients who experienced incidental LAA isolation after AF ablation were included. Culprit sites where ablation resulted in LAA isolation were identified. Thromboembolic risk despite oral anticoagulation (OAC) was compared to that in a propensity‐matched control group without LAA isolation. Results: Forty‐one patients with LAA isolation, and 82 matched patients without LAA isolation were included. The patient age, ejection fraction, LA diameter, and CHA2DS2‐VASc score were 64 ± 11 years, 55 ± 12%, 45.0 ± 7 mm and 2.62 ± 1.5, respectively. Culprit sites included the LAA base, mitral isthmus, inferior LA, Bachmann′s bundle, coronary sinus, and Marshall vein. After 4.2 ± 3.6 years follow‐up, thromboembolism occurred in 7 of 41 patients (17%) with LAA isolation versus 3 of 82 patients (4%) without isolation (log rank p <.009, HR 5.14, 95% CI [1.32–19.94], p =.02). Patients with and without thromboembolism had similar CHA2DS2‐VASc scores (2.65 ± 1.3 vs. 2.71 ± 0.76, p =.89). Thromboembolism occurred during noncompliance with or temporary discontinuation of OAC in four of the seven patients. Conclusions: Incidental LAA isolation may occur during ablation of atrial arrhythmias in the vicinity of, or even at sites remote from the appendage. Patients with incidental LAA isolation had higher rates of thromboembolism compared to patients without isolation. Since thromboembolism may occur despite prescription for OAC, the risks of LAA isolation must be weighed against clinical benefit and appendage occlusion devices should be considered in vulnerable patients. [ABSTRACT FROM AUTHOR]

Background: The role of the ligament of Marshall (LOM) in patients with atrial fibrillation (AF) has not been well defined.Objective: The purpose of this study was to describe the role of the LOM in patients with AF and related arrhythmias.Methods: Fifty-six patients (mean age 63 ± 11 years; persistent AF in 48 [86%]; ejection fraction 0.49 ± 0.13; left atrial diameter 4.7 ± 0.6 cm) with LOM-mediated arrhythmias were included.Results: A LOM-pulmonary vein (PV) connection was present in 18 patients (32%) and was eliminated with radiofrequency (RF) ablation at the left lateral ridge or crux (n = 12), at the mitral annulus (n = 3), or with alcohol/ethanol (EtOH) ablation of the vein of Marshall (VOM; n = 3). A LOM-mediated atrial tachycardia (AT) was present in 13 patients (23%). Thirty-one patients with refractory mitral isthmus conduction were referred for potential EtOH ablation. In the 6 patients in whom VOM was injected during perimitral reentry, EtOH resulted in slowing in 3 patients and termination in 1 patient. In others, EtOH infusion resulted in complete isolation of the left-sided PVs and left atrial appendage. Repeat RF and adjunctive EtOH ablation of the VOM tended to be more effective in creating conduction block across the mitral isthmus than RF ablation alone (P = .057).Conclusion: The LOM is responsible for a variety of arrhythmia mechanisms in patients with AF and atrial tachycardia. It may be ablated at any point along its course, at the mitral annulus, at the lateral ridge/PV antrum, and epicardially in the coronary sinus and the VOM itself. EtOH ablation of the VOM may be an adjunctive strategy in patients with refractory perimitral reentry. [ABSTRACT FROM AUTHOR]

Intra-Atrial Conduction Block. A 42-year-old woman with a history of cardiomyopathy and multiple ablation procedures for atrial tachycardia developed intra-atrial conduction block that mimicked atrioventricular (AV) nodal block during radiofrequency ablation at the cavotricuspid isthmus. She was treated with atrial pacing (from the coronary sinus), which overcame intra-atrial conduction block and resulted in AV nodal conduction. (J Cardiovasc Electrophysiol, Vol. 23, pp. 1258-1261, November 2012) [ABSTRACT FROM AUTHOR]

Objectives: 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).Background: Linear ablation for AF may result in macroreentrant AT.Methods: 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.Results: 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%).Conclusions: 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. [ABSTRACT FROM AUTHOR]