Ablation of focal atrial arrhythmia in patients with congenital heart defects after surgery: Role of circumscribed areas with heterogeneous conduction

BACKGROUND: In patients late after surgical repair of congenital heart disease (CHD), areas with abnormal electrophysiologic properties may serve as slow conducting pathways within a macroreentrant circuit or may be the source of focal atrial tachycardia. OBJECTIVES: The purpose of this study was to evaluate the role of abnormal areas during focal atrial tachycardia prior to ablation. METHODS: Electroanatomic activation mapping of 62 atrial tachycardias was performed in 43 consecutive patients (37 +/- 12 years) after surgical repair of CHD. The mechanism of atrial tachycardia was scar related intra-atrial reentry (n = 27), cavotricuspid-related atrial flutter (n = 21), atrial fibrillation (n = 2), or focal atrial tachycardia (n = 10). During intra-atrial reentry, channels of slow conduction could be identified in all patients. Subsequent ablation was directed toward connecting two nonconductive borders. The site of origin during focal atrial tachycardia showed fractionated potentials and/or continuous electrical activity. RESULTS: Ablation directed at isolating the source area resulted in termination of focal atrial tachycardia in all cases. In two patients, ablation of an area showing continuous electrical activity giving rise to fibrillatory conduction resulted in termination of atrial fibrillation. Ablation of intra-atrial reentry was successful in 70%. Atrial flutter and focal atrial tachycardia were successfully ablated in all patients. No complications were observed. CONCLUSION: In patients with surgically corrected CHD, atrial tachycardia most often is caused by a macroreentrant mechanism but in some is the result of a focal mechanism. Areas of abnormal conduction may serve not only as a zone of slow conduction within a macroreentrant circuit but also as the site of origin of a focal atrial arrhythmia. Catheter ablation directed at "source isolation" is effective in eliminating focal atrial tachycardia in patients with CHD.     

Differentiating macroreentrant from focal atrial tachycardias occurred after circumferential pulmonary vein isolation

Macroreentrant and Focal Atrial Tachycardias. Background: Atrial tachycardias (ATs) are commonly observed following catheter ablation of atrial fibrillation (AF). The aim of this study was to identify ECG characteristics that differentiate focal from macroreentrant ATs after circumferential pulmonary vein isolation (CPVI). Methods and Results: One hundred and twenty ATs that occurred after CPVI were mapped using a 3‐dimensional mapping system in 87 patients with AF. Further ablation was performed to eliminate the ATs. The surface ECGs of 68 ATs in 41 consecutive patients (Group 1) were analyzed retrospectively to create diagnostic algorithms. The algorithms were tested in the second 46 consecutive patients (Group 2). Patients with macroreentrant AT had lower left atrial (LA) voltage than those with focal AT (1.3 ± 0.3 vs 1.5 ± 0.2 mV, P = 0.01). Focal AT had a higher incidence of a positive polarity in V6 compared with macroreentrant AT (88% vs 55%, P = 0.03). The positive amplitude of the flutter/P waves in V6 was higher for focal AT than macroreentrant AT. The cycle lengths of the focal ATs were longer than those for macroreentrant AT (296 ± 107 vs 244 ± 25 ms, P < 0.001). Right atrial macroreentrant AT had a higher incidence of a negative polarity in at least 1 precordial lead compared with LA macroreentry. The positive flutter waves in V1 could differentiate roof/mitral isthmus dependent from non‐roof/mitral isthmus dependent macroreentry. This algorithm correctly differentiated the focal from macroreentrant ATs with a sensitivity of 94%, specificity of 91%, and predictive accuracy of 92% in Group 2. Conclusion: Different electrophysiological properties may facilitate the differentiation between macroreentrant and focal ATs after CPVI. (J Cardiovasc Electrophysiol, Vol. 22, pp. 748‐755, July 2011)     

Catheter ablation of atrial flutter and macroreentrant atrial tachycardia.

Catheter ablation has evolved from an experimental technique to first-line therapy for the treatment of atrial flutter. Atrial flutter is characterized by a macroreentrant atrial tachycardia circuit. Successful ablation of atrial flutter involves (1) mapping the atrial flutter to define the conduction zones within the re-entrant circuit to determine whether the atrial flutter is isthmus-dependent, non-isthmus-dependent, or atypical; (2) interrupting the atrial flutter macroreentrant circuit with an ablation catheter by creating either focal or linear lesions within a critical zone of slow conduction that extends to anatomical borders; and (3) terminating the tachycardia and demonstrating conduction block within the atrial flutter circuit after ablation. This update discusses the classification schemes of atrial flutter and macroreentrant atrial tachycardias, reviews the technique of radiofrequency catheter ablation, and highlights recent ablation approaches for atrial flutters and macroreentrant atrial tachycardias.     

Acute effects of left atrial radiofrequency ablation on atrial fibrillation

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.     

Atrial Tachycardias Occurring Late After Open Heart Surgery

Atrial tachycardias are common after open heart surgery. Most commonly these are macro-reentrant including cavotricuspid isthmus dependent atrial flutter, incisional right atrial flutter and left atrial flutter. Focal atrial tachycardias occur less frequently. The specific type of atrial tachycardia highly depends on the type of surgical incision. Catheter ablation can be very effective, however requires a thorough understanding of anatomy and surgical technique.     

Dual independent atrial tachycardias after ablation of chronic atrial fibrillation

We report the case of a 71-year-old man with two atrial tachycardias evolving simultaneously and independently in two dissociated regions after extensive ablation for chronic atrial fibrillation. One tachycardia was a focal tachycardia originating from the right inferior pulmonary vein and activating the posterior left atrium with a 2:1 conduction block, while the other tachycardia was an atrial flutter circulating around the tricuspid annulus, activating the right atrium and the anterior wall of the left atrium. These two atrial tachycardias were successfully ablated prior to restoration of sinus rhythm.     

Supraventricular arrhythmia before and after surgical closure of atrial septal defects: spectrum, prognosis and management.

Supraventricular arrhythmias are often observed in patients before and after atrial septal defect repair. Although several papers report different incidences of sustained supraventricular arrhythmias, postoperative 'incisional' macroreentrant tachycardias have not been systematically investigated. METHODS: We reviewed 136 consecutive patients (79 female, 57 male, mean age 36.8+/-17.8 years) who underwent atrial septal defect repair at our institutions between January 1990 and January 1999. Coexisting valve disease requiring surgical intervention was noted in 13 patients (9.5%). The mean follow-up period was 78.8+/-30.1 months. RESULTS: Sustained supraventricular arrhythmias occurred in 12 patients (8.8%) before surgery (atrial fibrillation in 11 patients). Using multivariate analysis the occurrence of arrhythmia significantly correlated with the presence of coexisting heart disease (P< 0.001) and age at surgery (P=0.011) After surgery sustained supraventricular arrhythmias were recorded in 16 patients (11.7%). Eleven of them had atrial fibrillation, permanent in 8 cases, 4 'incisional' macroreentrant atrial tachycardia and 1 atrioventricular re-entry tachycardia. There was a significant correlation between pre and postoperative arrhythmia (P< 0.001). Two of the 4 patients with macroreentrant atrial tachycardia underwent successful radiofrequency catheter ablation, whereas the arrhythmia was controlled medically in the remaining 2 patients. CONCLUSIONS: Atrial fibrillation remains the most frequent form of arrhythmia before and after surgical closure of atrial septal defects in adulthood, and relates to age at the time of repair and coexisting heart disease. Incisional macroreentrant atrial tachycardia is an identifiable, albeit less common, form of tachycardia, which can be treated by transcatheter ablation.     

Focal Atrial Tachycardia:

Atrial Tachycardia. Introduction : Reports about the clinical and electrophysiologic characteristics of focal atrial tachycardia vary widely. Furthermore, the impact of age, gender, associated cardiac diseases, mechanism, location of atrial tachycardia, and the prediction of results of radiofrequency catheter ablation was not clear. The purpose of this study was to further understand the clinical and electrophysiologic characteristics of focal atrial tachycardia and the prediction of results of radiofrequency ablation.
Methods and Results: We searched the literature published between January 1969 and July 1997 using the key word "atrial tachycardia" from the MEDLINE and National Library of Medicine systems. The items analyzed were age, sex, cardiac disease, mechanism, attack pattern, cycle length, location, number of atrial tachycardias, results of ablation, and recurrence after ablation. Multivariate analysis showed that age and paroxysmal type of tachycardia were independent predictors of nonautomatic mechanism; age and presence of other cardiac diseases were independent predictors of multiple atrial tachycardias, and age also was the independent predictor of right-sided atrial tachycardia. Atrial tachycardia located in the right atrium was the only significant predictor of successful radiofrequency catheter ablation. Other cardiac diseases and multiple atrial tachycardias were the significant predictors of recurrence after initial successful radiofrequency catheter ablation.
Conclusion : Patient age is closely related to the clinical and electrophysiologic characteristics of atrial tachycardia based on our reanalysis, which found that patient age is an independent predictor of nonautomatic mechanism, right atrial location, existence of multiple atrial tachycardias, and recurrence of atrial tachycardia after initial successful ablation.     

Theory and practical approaches in catheter ablation of atrial flutter

Atrial flutter can be understood as atrial tachycardia due to a single intraatrial macroreentrant circuit that is determined by fixed or functional boundaries. In various types of atrial flutter, radiofrequency ablation became an established curative therapy. During the course of an ablation procedure, initially, the reentrant circuit has to be determined, e.g. by activation and entrainment mapping. Subsequently, the boundaries have to be identified. By connecting two appropriate boundaries with a linear lesion, the intraatrial reentrant circuit can be inhibited. Finally, it should be proven that the linear lesion results in a complete line of conduction block. Doing so, the acute and long-term results of atrial flutter ablation are comparable to those of other supraventricular tachycardias.     

Subcostal M-mode echocardiography of the right atrial wall for differentiation of supraventricular tachyarrhythmias with aberration from ventricular tachycardia

Atrial contractions can be reliably detected by subcostal M-mode echocardiography of the right atrial wall. Recognition of various rhythm disturbances, especially tachyarrhythmias, is facilitated in the simultaneously recorded nondiagnostic ECG. Differentiation between supraventricular tachycardias with aberration and ventricular tachycardia with atrioventricular dissociation is alleviated. However, this technique is of limited value in the diagnosis of ventricular tachycardia with retroconduction and is not useful in differentiating supraventricular tachycardias with wide QRS from ventricular tachycardia when atrial fibrillation coexists.     

Stable secondary arrhythmias late after intraoperative radiofrequency ablation of atrial fibrillation: incidence, mechanism, and treatment

INTRODUCTION: Intraoperative radiofrequency (RF) ablation is an effective treatment of atrial fibrillation (AF). However, secondary arrhythmias late after ablation may complicate the patient's course. We report on the incidence, mechanisms, and treatment of gap-related atrial flutter and other secondary arrhythmias during long-term follow-up. METHODS AND RESULTS: In 129 patients who underwent intraoperative RF ablation with placement of left atrial linear lesions using minimally invasive surgical techniques, secondary arrhythmias were analyzed during long-term follow-up (20 +/- 6 months). Transient atrial arrhythmias during the first 3 postoperative months were excluded. In 8 (6.2%) of 129 patients, sustained stable secondary arrhythmias were documented. Left atrial, gap-related atrial flutter was observed in 4 patients (3.1%). The flutter was treated by percutaneous RF ablation in 3 patients (2.3%) and with drugs in 1 patient (0.8%). In 2 patients (1.6%), right atrial isthmus-dependent atrial flutter occurred and was treated successfully by percutaneous RF ablation. In 2 patients (1.6%), ectopic right atrial tachycardias occurred and were treated with percutaneous RF ablation. CONCLUSION: Late after intraoperative RF ablation of atrial fibrillation, three types of stable secondary arrhythmias were observed in 6% of patients: left atrial gap-related atrial flutter, right atrial isthmus-dependent atrial flutter, and ectopic atrial tachycardia. Gaps after intraoperative RF ablation due to noncontinuous or nontransmural linear lesions may lead to stable left atrial macroreentrant tachycardias, requiring new interventional therapy.     

Atrial Macroreentry Involving the Myocardium of the Coronary Sinus: A Unique Mechanism for Atypical Flutter

Macroreentry Involving the Coronary Sinus. Atrial flutter involving either clockwise or counterclockwise rotation around the tricuspid annulus utilizing the subeustachian isthmus has been well described. However, macroreentrant atrial circuits in atypical atrial flutter in patients who have not undergone previous surgery or without atrial disease are not well defined. We describe a patient without structural heart disease who presented with an atrial macroreentrant rhythm. Entrainment mapping demonstrated a critical isthmus within the coronary sinus. Activation mapping demonstrated double potential throughout the length of the coronary sinus with disparate activation sequences. A circuit involving the myocardium of the coronary sinus, exiting in the lateral left atrium, down the interatrial septum, and reentering into the coronary sinus was identified. Successful ablation of the rhythm was accomplished by a circumferential radiofrequency application within the coronary sinus.     

非外科手术瘢痕相关性右心房房性心动过速：电解剖标测与消融

目的探讨非外科手术后的瘢痕相关性右心房房性心动过速（房速）的心内电生理和Carto三维电解剖标测特点及消融方法。方法2008年9月至2009年4月我中心诊治的14例无器质性心脏病基础的右心房房速患者,在Carto三维标测系统指导下行心内电生理检查、标测和射频消融。结果14例患者中有4例心内电生理检查和Carto电解剖标测符合右心房大折返性房速且在Carto电解剖电压标测中显示出“自发性瘢痕”,瘢痕分布于右心房游离壁。这4例患者年龄32～48岁,病史（23．40±15．43）个月,曾使用2种以上抗心律失常药物治疗无效。2例患者右心房轻至中度扩大,左心室射血分数均在正常范围,无明显器质性心脏病依据和心外科手术史及导管消融史。3例患者在瘢痕区内标测到缓慢传导的峡部,2例可诱发出三尖瓣峡部依赖性逆时针心房扑动（房扑）。在三尖瓣峡部、上腔静脉与瘢痕之间、下腔静脉与瘢痕之间、瘢痕与三尖瓣环之问,瘢痕与瘢痕之问或瘢痕区内缓慢传导的“峡部”进行线性消融。4例患者均即刻消融成功。随访（4．2±1．8）个月,3例未再发作心动过速,1例偶尔发作非持续性房速,服药控制良好。结论“自发性瘢痕”相关性右心房大折返性房速临床少见,三维电解剖电压标测可提高消融成功率。     

Catheter ablation of long-lasting persistent atrial fibrillation: critical structures for termination

BACKGROUND: The relative contributions of different atrial regions to the maintenance of persistent atrial fibrillation (AF) are not known. METHODS: 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. RESULTS: 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. CONCLUSION: 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.     

Adenosine-Sensitive Atrial Reentrant Tachycardia Originating from the Atrioventricular Nodal Transitional Area

Adenosine-Sensitive AT from AVN Area. Introduction : Atrial tachycardia shows wide variations in its electrophysiologic properties and sites of origin. We report an atrial tachycardia with ECG manifestations and electrophysiologic characteristics similar to an atypical form of AV nodal reentrant tachycardia (AVNRT).
Methods and Results : This supraventricular tachycardia was observed in 11 patients. It was initiated by atrial extrastimulation with an inverse relationship between the coupling interval of an extrastimulus and the postextrastimulus interval. Its induction was not related to a jump in the AH interval, and its perpetuation was independent of conduction block in the AV node. Ventricular pacing during tachycardia demonstrated AV dissociation without affecting the atrial cycle length. A very small dose of adenosine triphosphate (mean 3.9 ± 1.2 mg) could terminate the tachycardia. The earliest atrial activation during tachycardia was recorded at the low anteroseptal right atrium with a different intra-atrial activation sequence from that recorded during ventricular pacing, where the tachycardia was successfully ablated in 9 of 10 attempted patients. Bidirectional AV nodal conduction remained unatttched after successful ablation.
Conclusion : There may he an entity of adenosine-sensitive atrial tachycardia probably due to focal reentry within the AV node or its transitional tissues without involvement of the AV nodal pathways. This tachycardia can he ablated without disturbing AV nodal conduction from the right atrial septum.     

Surface electrocardiogram characteristics of atrial tachycardias occurring after pulmonary vein isolation

OBJECTIVE: The purpose of this study was to describe the surface electrocardiogram (ECG) morphology of common atrial tachycardias (ATs) that occur after pulmonary vein (PV) isolation. BACKGROUND: Focal ATs from reconnected PVs and macroreentrant mitral annular (MA) flutter are the most common form of ATs occurring after PV isolation. METHODS: Patients with persistent AT after PV isolation underwent mapping and ablation. Tachycardia origin and mechanism were determined using electroanatomic mapping and entrainment techniques. Patients with typical right atrial flutter occurring after PV isolation were also included for comparison. RESULTS: Thirty-nine tachycardias were identified in 36 patients, either focal left AT (n = 24) or MA flutter (n = 15). Focal ATs originated from reconnected segments of the right PVs (n = 14) and left PVs (n = 10). MA flutters were counterclockwise (CCL; n = 9) or clockwise (CL; n = 6). Patients with MA flutter had a shorter tachycardia cycle length (239 +/- 7 vs. 259 +/- 34 s; P <.05) than those with focal ATs. CCL MA flutter was positive in the inferior and precordial leads and had a significant negative component in leads I and aVL. CL MA flutter demonstrated the converse limb lead morphology with a significant negative F wave in the inferior leads and positive F wave in leads I and aVL. A negative component in lead I, when present, was best at differentiating CCL MA flutter from left PV ATs, while a positive F wave in lead I was best at differentiating CL MA flutter from CCL right atrial flutter. CONCLUSIONS: There are unique surface ECG characteristics for CL and CCL MA flutter and AT due to reconnected PVs; knowledge of these characteristics may help when planning an ablation strategy.     

Differential Effects of Adenosine on Focal and Macroreentrant Atrial Tachycardia

INTRODUCTION: The effects of adenosine on atrial tachycardia (AT) remain controversial, and the mechanistic implications of adenosine termination have not been fully established. The purpose of this study was to elucidate the differential effects of adenosine on focal and macroreentrant AT and describe the characteristics of adenosine-sensitive AT. METHODS AND RESULTS: Thirty patients received adenosine during AT. Tachycardia origins were identified as focal or macroreentrant during invasive electrophysiologic studies. Responses to adenosine were analyzed and characterized as tachycardia termination, transient suppression, or no effect. Electrophysiologic studies demonstrated a focal origin of tachycardia in 17 patients. Adenosine terminated focal tachycardias in 14 patients (dose 7.3 +/- 4.0 mg) and transiently suppressed the arrhythmias in three others (dose 10.0 +/- 6.9 mg). A macroreentrant mechanism was demonstrated in 13 patients; adenosine terminated only one of these tachycardias and had no effect on the remaining 12 patients (dose 10.2 +/- 2.9 mg). Four classes of adenosine-sensitive AT were identified. Class I consisted of nine patients with tachycardia arising from the crista terminalis; these tachycardias also terminated with verapamil (4/4). Class II consisted of four patients with repetitive monomorphic AT arising from diverse sites in the right atrium; these either slowed or terminated in response to verapamil (2/2). Class III consisted of the three patients with transient suppression and demonstrated electropharmacologic characteristics consistent with an automatic mechanism, including insensitivity to verapamil (2/2). In the one patient with macroreentrant AT that was comprised of decremental atrial tissue, adenosine terminated tachycardia in a zone of decremental slow conduction (Class IV); this tachycardia slowed with verapamil. CONCLUSIONS: Adenosine-sensitive AT is usually focal in origin and arises either from the region of the crista terminalis (inclusive of the sinus node) or from diverse atrial sites with an incessant nonsustained repetitive pattern. Although most forms of macroreentrant AT are insensitive to adenosine, rarely macroreentrant AT with zones of decremental slow conduction can demonstrate adenosine sensitivity.     

Dual-loop intra-atrial re-entry tachycardia in a patient with ischaemic cardiomyopathy.

A 65-year-old man with ischaemic cardiomyopathy (three prior coronary artery bypass surgery procedures), underwent catheter ablation for recurrent atrial flutter. Electrophysiological study initially revealed clockwise, tricuspid annulus/inferior vena cava isthmus dependent, atrial flutter. During radiofrequency energy ablation atrial flutter changed into a different atrial tachycardia without change in cycle length or interruption of the tachycardia. The new tachycardia was a right atrial free wall re-entry tachycardia. Thus the two atrial tachycardias formed a dual-loop ('figure-of-eight') re-entry circuit, possibly due to atrial scar tissue from multiple cardiac surgery procedures.