Differential effects of adenosine on focal and macroreentrant atrial tachycardia

Five Criteria Predict Induction and Ablation of Supraventricular Tachycardia

INTRODUCTION

Current guidelines recommend electrophysiological study (EPS) and ablation for primary treatment of supraventricular tachycardia (SVT), but there is little information to guide patient selection for the procedure. The purpose of this study was to identify preoperative features that would predict whether patients with signs or symptoms of tachycardia were likely to have SVT induced and ablated at EPS.

METHODS

We performed a retrospective chart review of 1089 patients referred for EPS and ablation of SVT at 2 high volume centers. The population consisted of a derivation cohort of 810 patients and a validation cohort of 279 patients. We evaluated various clinical, EKG, and monitor features to determine which ones correlated with SVT induction or ablation.

RESULTS

Five preoperative findings predicted a high probability that SVT would be induced and ablated at EPS: 1. A characteristic EKG recording of SVT. 2. Termination of SVT with adenosine. 3. Termination of SVT or symptoms with vagal maneuvers. 4. An episode of SVT lasting ≥ 30 s on a monitor recording. 5. Pre-excitation on the baseline EKG. Patients exhibiting at least one of these features had a high probability of SVT induction and ablation, while those exhibiting none had a low probability (Induction, 76% vs. 19%, RR = 3.96 (2.76-5.69), p < .001; Ablation, 88% versus 26%, RR = 3.32 (2.48-4.46), p < .001). A point-based score was derived and validated that can be used to estimate the probability of induction and ablation for individual patients.

CONCLUSION

Simple criteria classify patients as having a high or low probability of SVT induction and ablation at EPS. They can be used as a guide for clinical decision making when considering invasive testing for patients with symptoms of tachycardia.

Atrial Tachycardias After Atrial Fibrillation Ablation: How to Manage?

With catheter ablation becoming effective for non-pharmacological management of AF, many cases of atrial tachycardia (AT) after AF ablation have been reported in the past decade. These arrhythmias are often symptomatic and respond poorly to medical therapy. Post-AF-ablation ATs can be classified into the following three categories: focal, macroreentrant and microreentrant ATs. Mapping these ATs is challenging because of atrial remodelling and its complex mechanisms, such as double ATs and multiple-loop ATs. High-density mapping can achieve precise identification of the circuits and critical isthmuses of ATs and improve the efficacy of catheter ablation. The purpose of this article is to review the mechanisms, mapping and ablation strategy, and outcome of ATs after AF ablation.

Clinical and Electrophysiological Correlates of Incessant Ivabradine-Sensitive Atrial Tachycardia

Background:

Incessant focal atrial tachycardia (FAT), if untreated, can lead to ventricular dysfunction and heart failure (tachycardia-induced cardiomyopathy). Drug therapy of FAT is often difficult and ineffective. The efficacy of ivabradine has not been systematically evaluated in the treatment of FAT.

Methods:

The study group consisted of patients with incessant FAT (lasting >24 hours) and structurally normal hearts. Patients with ventricular dysfunction as a consequence of FAT were not excluded. All antiarrhythmic drugs were discontinued at least 5 half-lives before the initiation of ivabradine. Oral ivabradine (adults, 10 mg twice 12 hours apart; pediatric patients: 0.28 mg/kg in 2 divided doses) was initiated in the intensive care unit under continuous electrocardiographic monitoring. A positive response was defined as the termination of tachycardia with the restoration of sinus rhythm or suppression of the tachycardia to <100 beats per minute without termination within 12 hours of initiating ivabradine.

Results:

Twenty-eight patients (mean age, 34.6±21.5 years; women, 60.7%) were included in the study. The most common symptom was palpitation (85.7%) followed by shortness of breath (25%). The mean atrial rate during tachycardia was 170±21 beats per minute, and the mean left ventricular ejection fraction was 54.7±14.3%. Overall, 18 (64.3%) patients responded within 6 hours of the first dose of ivabradine. Thirteen of 18 ivabradine responders subsequently underwent successful catheter ablation. FAT originating in the atrial appendages was a predictor of ivabradine response compared with those arising from other atrial sites ( P =0.046).

Conclusions:

Ivabradine-sensitive atrial tachycardia constitutes 64% of incessant FAT in patients without structural heart disease. Incessant FAT originating in the atrial appendages is more likely to respond to ivabradine than that arising from other atrial sites. Our findings implicate the funny current in the pathogenesis of FAT.

Atrial Tachyarrhythmias and Atrial Flutter: the Basics of Diagnostics and Modern Opportunities of Therapy

The article is devoted to the description of all types of atrial tachyarrhythmias, including inappropriate sinus tachycardia, which, as a rule, is not paid enough attention in the domestic literature, sinoatrial node reentrant tachycardia, focal and multifocal atrial tachycardia, atrial flutter, and atrial fibrillation. The electrophysiological mechanisms of development and electrocardiographic criteria for the diagnosis of these cardiac rhythm disturbances are presented. Along with this, the article discusses the modern view of the strategy and tactics of pharmacological cardioversion and preventive therapy in patients with the main types of atrial tachyarrhythmias and atrial flutter. It is noted that the prognosis for inappropriate sinus tachycardia, as a rule, is favorable, and therefore, aim of treatment is to reduce the symptoms, and in their absence medical treatment is not necessary. Much attention is paid to drug and interventional treatment of atrial flutter. It is emphasized that catheter ablation of isthmus-dependent atrial flutter in most cases is preferred over long-term pharmacotherapy. However, in prolonged observation (more than 3 years), nearly 1/3 of patients may develop paroxysmal atrial fibrillation. At the same time, catheter ablation of atypical atrial flutter is, in most cases, substantially less effective. The indications and side effects of catheter ablation of the sinus node are also discussed. The authors provide a critical analysis of traditional approaches to the treatment of atrial tachyarrhythmias and analyze new recommendations for the management of these patients presented in Europe and the USA. Based on these recommendations, clear algorithms for the management of patients with atrial tachyarrhythmias are given. The need to prevent thromboembolic complications in some types of atrial tachyarrhythmias is emphasized.

Focal atrial tachycardia ablation: Highly successful with conventional mapping

BACKGROUND/OBJECTIVE

Radiofrequency catheter ablation (RFCA) of focal atrial tachycardia (FAT) traditionally is guided by conventional endocardial mapping of earliest atrial activation; however, more recently electro-anatomical mapping is heralded as a more effective, albeit more expensive, tool to guide ablation. Herein we present the results of conventional mapping-guided RFCA. Apropos, we conducted a literature search of studies reporting > 10 FAT patients submitted to RFCA.

METHODS AND RESULTS

Conventional mapping-guided RFCA, performed in 63 FAT patients (aged 42.4 + 17.3 years; 14 with incessant tachycardia and 12 with tachycardiomyopathy (TCM)), was successful in 61 (96.8%) patients, applied for single foci in 59 (93.7%) and two foci in 4 patients, right (n = 46) or left sided (n = 17). The earliest atrial activation time at the ablation site was 41.3 ± 16.2 ms. Fluoroscopy time averaged 27.3 + 18.7 min, and procedure lasted 2.6 + 1.7 h. Complications occurred in two patients (sinus pauses in one needing a pacemaker and a large inguinal hematoma in one). Over 29.0 + 22.9 months, four patients (6.5%) had recurrences, of whom three were successfully re-ablated. All patients with TCM showed gradual improvement to normalization over 4-6 months. Literature search showed that RFCA success is equally high when guided with either conventional (88.5%) or electro-anatomical mapping (90%) with similar recurrences (9.6% vs. 9.5%).

CONCLUSION

Conventional mapping-guided RFCA of FAT had high success (96.8%) with low complication (3.2%) and recurrence rates (6.5%). TCM was fully reversible. These results are comparable to those achieved with the more expensive electro-anatomical mapping, which may be reserved for more complex cases or for those failing the conventional approach.

Supraventricular Tachycardia in Adult Congenital Heart Disease: Mechanisms, Diagnosis, and Clinical Aspects

Supraventricular arrhythmias represent a major source of morbidity in adults with congenital heart disease (ACHD). Anatomic variants and post-operative changes contribute to a unique electrophysiologic milieu ripe for the development of supraventricular tachycardia. Intra-atrial reentrant tachycardia is the most prevalent mechanism. Atrioventricular reciprocating tachycardia is common in lesions associated with accessory pathways. Abnormal anatomy complicates the management of atrioventricular nodal reentrant tachycardia. Tachycardia mediated by twin atrioventricular nodes is rare. Focal tachycardias are considerations in the ACHD population. Each of these tachycardia mechanisms is reviewed, focusing on the inherent diagnostic and therapeutic challenges.

Quantitative analysis of the right auricle with 256-slice computed tomography

PURPOSE

To quantitatively measure the morphology parameters of the right auricle with 256-slice multidetector computed tomography angiography (MDCTA) in healthy people.

MATERIALS AND METHODS

A retrospective analysis of 200 patients who had undergone coronary MDCTA with negative findings was performed. The raw imaging data were reconstructed and the right auricular volume, right atrial volume, right auricle height, base long and short axes, base perimeter and area, normal angle, and distance were quantitatively measured.

RESULTS

Men had significantly (P < 0.05) greater values than women in the right auricular volume (13.3 ± 4.0 vs. 11.7 ± 3.7 mL) and height (33.0 ± 5.0 vs. 30.5 ± 5.2 mm), the base long axis (34.4 ± 4.1 vs. 33.2 ± 3.9 mm), area (787.6 ± 177.6 vs. 771.0 ± 143.2 mm²) and perimeter (119.2 ± 17.5 vs. 115.0 ± 13.0), and the normal distance (22.4 ± 6.6 vs. 20.2 ± 6.7 mm). The normal 95 % reference range for the right auricular parameters was put forward. The right auricular parameters had a good correlation with the right atrium volume, aortic diameter, the body weight, height, and body surface area but a bad correlation with the vertebral body height. Significantly (P < 0.05) greater values were found in the normal angle and distance in subjects below than over 40 years of age. No other significant (P > 0.05) difference existed in the other right auricular parameters.

CONCLUSION

Quantitative measurements of the right auricle can help us get a good understanding of the right auricular morphology and its relationship with surrounding structures and are helpful for cardiac interventions of electrophysiology and radiofrequency ablation.

Executive Summary: European Heart Rhythm Association Consensus Document on the Management of Supraventricular Arrhythmias: Endorsed by Heart Rhythm Society (HRS), Asia-Pacific Heart Rhythm Society (APHRS), and Sociedad Latinoamericana de Estimulación Cardiaca y Electrofisiologia (SOLAECE)

This paper is an executive summary of the full European Heart Rhythm Association (EHRA) consensus document on the management of supraventricular arrhythmias, published in Europace. It summarises developments in the field and provides recommendations for patient management, with particular emphasis on new advances since the previous European Society of Cardiology guidelines. The EHRA consensus document is available to read in full at http://europace.oxfordjournals.org.

Unifying mechanism of sustained idiopathic atrial and ventricular annular tachycardia

BACKGROUND

Based on the current understanding of cardiac conduction system development and the observation that arrhythmogenic foci can originate in areas near the atrioventricular annuli, we hypothesized that focal annular tachycardias, whether atrial or ventricular, share a common mechanism. We, therefore, prospectively evaluated this hypothesis in patients with sustained atrial and ventricular tachycardia originating from the peri-tricuspid and mitral annuli.

METHODS AND RESULTS

Forty-nine consecutive patients with sustained, focal annular tachycardia comprised the study group. All underwent electrophysiological evaluation and the mode of tachycardia initiation, termination, sensitivity to catecholamine infusion, and response to adenosine/verapamil were evaluated. Electroanatomical activation maps identified the sites of arrhythmia origin. Tachycardias could be initiated or terminated or both with programmed stimulation in 46 of 46 patients and most (70%) were catecholamine facilitated. Of the 9 patients with sustained annular ventricular tachycardia, 3 were localized to the tricuspid annulus, and 6 to the mitral annulus. All the 9 ventricular tachycardias (100%) terminated with adenosine, 2 of 2 terminated with verapamil, and 2 of 2 terminated with Valsalva. Of the 40 patients with annular atrial tachycardia, 4 tachycardias were localized to the mitral annulus and 37 to the tricuspid annulus (including 9 para-Hisian), and all were adenosine sensitive.

CONCLUSIONS

Peri-annular atrial and ventricular tissue correspond to a region enriched with arrhythmogenic foci, which may reflect a common developmental origin. Furthermore, the sensitivity of these tachycardias to adenosine provides evidence for a shared arrhythmia mechanism, consistent with intracellular calcium overload and triggered activity.

A reappraisal on lidocaine-sensitive repetitive, uniform atrial tachycardia

BACKGROUND

Lidocaine sensitive, repetitive atrial tachycardia is an unusual arrhythmia whose electrophysiologic substrate remains undefined. We aimed to analyze the electropharmacologic characteristics of this arrhythmia with emphasis on its cellular substrate and response to drug challenges.

METHODS

We retrospectively analyzed a series of 18 patients from an electrocardiographic and electrophysiologic perspective and the response to pharmacological challenge.

RESULTS

There was no evidence of structural heart disease in 12 patients, 4 patients presented with systemic hypertension; one patient had a prior myocardial infarction and one a mitral valve prolapse. The arrhythmia depicted a consistent pattern in nine patients. The first initiating ectopic beat showed a long coupling interval, the cycle length of the second atrial ectopic beat presented the shortest cycle length and a further prolongation was apparent towards the end of the atrial salvos. Conversely, in the other nine cases, the atrial tachycardia cycle length was erratic. The arrhythmia was suppressed by asynchronous atrial pacing at cycle lengths longer than those of the atrial tachycardia. Intravenous lidocaine eliminated the arrhythmia in all patients, but intravenous verapamil suppressed the atrial tachycardia in only two patients while adenosine caused a transient disappearance in 2/8 patients. Only one patient responded to all the three agents. Radiofrequency ablation was successfully performed in 10 patients.

CONCLUSIONS

Repetitive uniform atrial tachycardia can be sensitive to lidocaine. In few cases, this rare focal arrhythmia may be also suppressed by adenosine and/or verapamil, which suggests a diversity of electrophysiologic substrates that deserve to be accurately identified.

Distinct pharmacologic substrate in lidocaine-sensitive, repetitive atrial tachycardia

Lidocaine-sensitive, repetitive atrial tachycardia is an uncommon arrhythmia. The electrophysiologic substrate is still unknown, and the pharmacologic responses have not been fully explored. The aim of this study was to investigate the effects of intravenous adenosine and verapamil in patients with lidocaine-sensitive atrial tachycardia. In 9 patients with repetitive uniform atrial tachycardia, the response to intravenous adenosine (12 mg), lidocaine (1 mg/kg body weight), and verapamil (10 mg) were sequentially investigated. Simultaneous 12-lead electrocardiogram (ECG) was recorded at baseline and continuously monitored thereafter. Tracings were obtained at regularly timed intervals right after the administration of each drug to evaluate changes in the arrhythmia characteristics. Repetitive atrial tachycardia was abolished by intravenous lidocaine in the 9 patients within the first 2 minutes after the end of injection. Adenosine suppressed the arrhythmia in 2 patients and shortened the runs of atrial ectopic activity in 1 patient, while verapamil was effective in 2 patients, 1 of them insensitive to adenosine and the other 1 sensitive to this agent. In 5 patients, the arrhythmia was abolished by radiofrequency ablation at different sites of the right atrium. Lidocaine-sensitive atrial tachycardia may eventually be also suppressed by adenosine and/or verapamil. This suggests that this enigmatic arrhythmia may be caused by different underlying electrophysiologic substrates and that at least in some cases, delayed afterdepolarizations seem to play a determining role.

Electrophysiologic properties of para-Hisian atrial tachycardia

BACKGROUND

Focal atrial tachycardia (AT) originates from preferential sites, including the tricuspid and mitral annuli. AT arising from the atrioventricular annuli is initiated and terminated with programmed stimulation and is, in general, adenosine and verapamil sensitive. Para-Hisian AT arising from the apex of the triangle of Koch has been considered to be a distinct entity, characterized by unique electrophysiological properties.

OBJECTIVE

We sought to more fully delineate the electrophysiological and electrocardiographic properties of para-Hisian AT in a large series of patients.

METHODS

The study population consisted of 38 patients (63 ± 15 years; 23 female) with AT from the para-Hisian region. The ATs were focal and originated from the anteroseptal tricuspid annulus, in close proximity to the His bundle recording. Proximity to the His bundle was confirmed by electrogram recordings, fluoroscopy, and centrifugal activation during three-dimensional mapping.

RESULTS

The mean AT cycle length was 421 ± 69 ms. AT was associated with a distinct P-wave morphology that was significantly narrower than the P wave during sinus rhythm. Adenosine (5.0 ± 1.5 mg) terminated AT in 34/35 patients. Intravenous verapamil terminated AT in three of three patients. Catheter ablation was attempted in 30 patients and was successful in 26 (87%).

CONCLUSION

The para-Hisian region is a source of focal AT, with properties consistent with AT arising circumferentially along the tricuspid and mitral annuli, and should be considered a subset of this broader group of "annular" ATs. The electropharmacologic findings in para-Hisian AT are mechanistically consistent with cyclic AMP-mediated triggered activity.

Atrial Tachycardias Occurring After Atrial Fibrillation Ablation: Strategies for Mapping and Ablation

The occurrence of left atrial tachycardias (AT) after catheter ablation for atrial fibrillation (AF) is common, especially after more extensive ablation of persistent AF. These AT are invariably symptomatic and often do not respond to medical therapy. The initial strategy involves ventricular rate control, cardioversion, and observation as some tachycardias may resolve with time. For persistent ATs, effective management frequently requires catheter intervention. Careful characterization of the tachycardia mechanism is essential in designing an effective ablation strategy that would also avoid further creation of pro-arrhythmic substrate. With this review, we summarize the incidence, mechanism, diagnosis and treatment of ATs occurring after AF ablation.

Antiarrhythmic Drug Therapy of Supraventricular Tachycardia

Pharmacologic therapy is commonly used for the acute treatment and termination of paroxysmal supraventricular tachycardia (SVT) and continues to be an important long-term option for some patients. Drug choice depends on the correct diagnosis of the arrhythmia and an understanding of its mechanism. Pharmacologic agents commonly used in the acute and chronic treatment of SVT are reviewed along with their effect on the various types of SVT. Drugs that are well tolerated with minimal side effects are preferred over agents with perhaps more efficacy but higher risk of toxicity.

Adenosine receptors and the heart: role in regulation of coronary blood flow and cardiac electrophysiology

Adenosine is an autacoid that plays a critical role in regulating cardiac function, including heart rate, contractility, and coronary flow. In this chapter, current knowledge of the functions and mechanisms of action of coronary flow regulation and electrophysiology will be discussed. Currently, there are four known adenosine receptor (AR) subtypes, namely A(1), A(2A), A(2B), and A(3). All four subtypes are known to regulate coronary flow. In general, A(2A)AR is the predominant receptor subtype responsible for coronary blood flow regulation, which dilates coronary arteries in both an endothelial-dependent and -independent manner. The roles of other ARs and their mechanisms of action will also be discussed. The increasing popularity of gene-modified models with targeted deletion or overexpression of a single AR subtype has helped to elucidate the roles of each receptor subtype. Combining pharmacologic tools with targeted gene deletion of individual AR subtypes has proven invaluable for discriminating the vascular effects unique to the activation of each AR subtype. Adenosine exerts its cardiac electrophysiologic effects mainly through the activation of A(1)AR. This receptor mediates direct as well as indirect effects of adenosine (i.e., anti-beta-adrenergic effects). In supraventricular tissues (atrial myocytes, sinuatrial node and atriovetricular node), adenosine exerts both direct and indirect effects, while it exerts only indirect effects in the ventricle. Adenosine exerts a negative chronotropic effect by suppressing the automaticity of cardiac pacemakers, and a negative dromotropic effect through inhibition of AV-nodal conduction. These effects of adenosine constitute the rationale for its use as a diagnostic and therapeutic agent. In recent years, efforts have been made to develop A(1)R-selective agonists as drug candidates that do not induce vasodilation, which is considered an undesirable effect in the clinical setting.

Electrophysiologic and electrocardiographic characteristics of focal atrial tachycardia arising from superior tricuspid annulus

OBJECTIVES

This study describes the electrophysiologic and electrocardiographic characteristics of focal atrial tachycardia (AT) arising from superior tricuspid annulus in six (1.9%) patients of a consecutive series of 320 patients.

METHODS

Six patients (mean age 42 +/- 22 years) with a mean cycle length of 326 ms of a consecutive series of 320 patients undergoing radiofrequency ablation for focal AT were mapped.

RESULTS

During electrophysiologic study, tachycardia could be induced in five patients with programmed atrial extrastimuli while a spontaneous onset and offset with 'warm-up and cool-down' phenomenon was seen in the other patient. During tachycardia, P-wave morphology in Lead I, II, III and aVF was upright in all the six patients. The precordial leads were dominantly negative or isoelectric in V(1)-V(2) and positive in V(5)-V(6) with a transition at V(3) or V(4). Moreover, the tachycardia was sensitive to intravenous administration of adenosine triphosphate in five of six patients.

CONCLUSIONS

Radiofrequency ablation was performed successfully in all patients (mean 4.5 +/- 1.2 applications). No recurrence of AT was observed after a mean follow-up of 8 +/- 6 months. Thus, AT arising from superior tricuspid annulus is rare. Radiofrequency ablation of this kind of AT is safe and effective.

Focal Atrial Tachycardias Arising from the Right Atrial Appendage: Electrocardiographic and Electrophysiologic Characteristics and Radiofrequency Ablation

OBJECTIVE

To characterize the electrocardiographic and electrophysiological features and frequency of focal atrial tachycardia (AT) originating from the right atrial appendage (RAA).

BACKGROUND

The RAA has been described as a site of origin of AT, but detailed characterization of these tachycardias is limited.

METHODS

Ten patients (3.8%) of 261 undergoing radiofrequency ablation (RFA) for focal AT are reported. Endocardial activation maps (EAM) were recorded from catheters at the CS (10 pole), tricuspid annulus (20 pole Halo catheter), and His positions. P waves were classified as negative, positive, isoelectric, or biphasic.

RESULTS

The mean age was 39 +/- 20 years, nine males, with symptoms for 4.1 +/- 5.1 years. Tachycardia was incessant in seven patients, spontaneous in one patient, and induced by programmed extrastimuli in two patients. These foci had a characteristic P wave morphology. The P wave was negative in lead V(1) in all patients, becoming progressively positive across the precordial leads. The P waves in the inferior leads were low amplitude positive in the majority of patients. Earliest EAM activity occurred on the Halo catheter in all patients. Mean activation time at the successful RFA site =-38 +/- 15 msec. Irrigated catheters were used in six patients, due to difficulty achieving adequate power. RFA was acutely successful in all patients. Long-term success was achieved in all patients over a mean follow up of 8 +/- 7 months.

CONCLUSIONS

The RAA is an uncommon site of origin for focal AT (3.8%). It can be suspected as a potential anatomic site of AT origin from the characteristic P wave and activation timing. Irrigated ablation catheters are often required for successful ablation. Long-term success was achieved with focal ablation in all patients.

Adenosine-insensitive focal atrial tachycardia: evidence for de novo micro-re-entry in the human atrium

OBJECTIVES

The purpose of this work was to describe the entity and mechanism of adenosine-insensitive focal atrial tachycardia (AT).

BACKGROUND

The majority of regular focal ATs demonstrate properties consistent with triggered activity, including termination by adenosine. Less commonly, AT may be due to enhanced automaticity, which is transiently suppressed by adenosine. Small re-entrant circuits may also give rise to focal AT, but limited data exist regarding this entity as a de novo arrhythmia in the human atrium.

METHODS

Eighty cases of focal AT were mapped in the electrophysiology laboratory and challenged with adenosine. Adenosine-sensitive and -insensitive groups were compared with regard to demographics, anatomical distribution, and electrogram characteristics at the tachycardia origin.

RESULTS

In response to adenosine, termination occurred in 67 cases (84%), transient suppression in 5 (6%), 6 were insensitive (8%), and 2 exhibited nonspecific responses. Adenosine-insensitive AT arose near the pulmonary vein ostia (4) and from the right atrium (2), whereas adenosine-sensitive AT arose from a wide distribution in both atria. Electrograms at the site of origin for adenosine-insensitive AT were highly fractionated, with longer durations and lower amplitudes compared with AT that terminated or was transiently suppressed. The electrograms at the origin of adenosine-insensitive ATs comprised 22% to 69% of the tachycardia cycle length, compared with 4% to 21% for adenosine-sensitive ATs. In 3 adenosine-insensitive ATs, entrainment was demonstrated with post-pacing intervals equivalent to the tachycardia cycle length.

CONCLUSIONS

The characteristics of adenosine-insensitive focal AT differ from adenosine-sensitive AT and are consistent with small re-entrant circuits. These data provide evidence that focal re-entry is a mechanism of AT and has an electropharmacologic profile that differs from AT due to automaticity and triggered activity.

Focal Atrial Tachycardia I: Clinical Features, Diagnosis, Mechanisms, and Anatomic Location

Atrial tachycardia (AT) may be focal or macroreentrant. In this review we will concentrate on focal AT. The diagnosis of focal AT may be made from a standard electrocardiogram (ECG); however, in some cases differentiation from other forms of supraventricular tachycardia may be difficult. Focal AT may be due to several different mechanisms, including abnormal automaticity, triggered activity, and microreentry. Focal AT does not occur randomly throughout the atria but has a characteristic anatomic distribution. In this review, we particularly focus on the clinical features, diagnosis, mechanisms, and anatomic location of focal AT.

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

INTRODUCTION

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.

METHODS AND RESULTS

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%).

CONCLUSION

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.

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

BACKGROUND

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.

OBJECTIVES

The purpose of this study was to determine the mechanism of focal ATs occurring after PV isolation.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Reentry Within the Cavotricuspid Isthmus: An Isthmus Dependent Circuit

BACKGROUND

We describe a new cavotricuspid isthmus (CTI) circuit.

METHODS

This study includes 8 patients referred for atrial flutter (AFL) ablation whose tachycardia circuit was confined to the septal CTI and the os of the coronary sinus (CS(OS)) region. Entrainment mapping was performed within the CTI, CS(OS), and other right atrial annular sites (tricuspid annulus (TA)). Electroanatomic mapping was available in 2 patients.

RESULTS

Sustained AFL occurred in all patients with mean tachycardia cycle length (TCL) of 318 +/- 54 (276 - 420) ms. During tachycardia, fractionated or double potentials were recorded at either the septal CTI and/or the region of CS(OS) in all, and concealed entrainment with post-pacing interval (PPI)--TCL < or = 25 ms occurred in this area; but manifest entrainment with PPI > TCL was demonstrated from the anteroinferior CTI and other annular sites in 7/8 patients. In one, tachycardia continued with conduction block at the anteroinferior CTI during ablation. Up to three different right atrial activation patterns (identical TCL) were observed. The tachycardia showed a counterclockwise (CCW) pattern in 6, a clockwise pattern in 2, and simultaneous activation of both low lateral right atrium and septum in 5. Electroanatomic mapping was available in 2, showing an early area arising from the septal CTI in 1, and a CCW activation sequence along the TA in another. Radiofrequency application to the septal CTI terminated tachycardia in 4, and tachycardia no longer inducible in all.

CONCLUSIONS

We describe a tachycardia circuit confined to the septal CTI/CS(OS) region, and hypothesize that this circuit involves slow conduction within the CTI and around the CS(OS), which acts as a central obstacle.

Nonautomatic focal atrial tachycardia: characterization and ablation of a poorly understood arrhythmia in 38 patients

Nonautomatic focal atrial tachycardia (NAFAT) is a rare and poorly understood arrhythmia either due to microreentry or triggered mechanism. NAFAT was defined as a focal atrial tachycardia which was inducible with pacing maneuvers in the electrophysiology lab. We reviewed the charts and EP study reports of all 38 patients with NAFAT, who underwent an EP study at our center between April 1994 and September 2000. Patients' were predominantly female (n = 31, 82%), aged 11-78 years (median 46). The mean age at presentation was 31 years (range 7-71 years). None of the patients had structural heart disease or had undergone prior heart surgery. Electroanatomic mapping (EAM) was performed in 22 patients and showed no scars in the atrium. A total of 45 foci were identified (range 1-3 foci/patient). Anatomically NAFAT foci were predominantly right atrial (n = 35) rather than left (n = 10). The NAFAT cycle length ranged from 270 to 490 (mean +/- SD; 380 +/- 69 ms) and was significantly lower in patients younger than 24 years of age. Ablation, attempted for 42 foci was successful in 33 (79%). The success rate in the EAM group was 20/25 foci (80%) compared to 13/18 (72%) in the non-EAM group. In conclusion, NAFAT is a rare arrhythmia which predominantly affects women with no other associated cardiac disease. It mainly occurs in the right atrium, affects all ages and is amenable to catheter ablation.

Response to adenosine differentiates focal from macroreentrant atrial tachycardia: validation using three-dimensional electroanatomic mapping

BACKGROUND

We previously proposed that adenosine has mechanism-specific effects on atrial tachycardia (AT), such that adenosine terminates AT attributable to triggered activity, transiently suppresses automatic rhythms, and has no effect on macroreentrant AT. This, however, remains controversial, because other studies have reported that adenosine terminates reentrant AT. To clarify this issue, we used 3D electroanatomic mapping to delineate the tachycardia circuit and thereby determine whether the response to adenosine differentiates focal from macroreentrant AT.

METHODS AND RESULTS

We examined the effect of adenosine on 43 ATs in 42 consecutive patients (59+/-15 years of age; 26 female) who received adenosine during tachycardia and whose mechanism of AT was characterized by pharmacological perturbation, entrainment, 3D electroanatomic mapping, and results of radiofrequency ablation. Eight tachycardias were macroreentrant (noncavotricuspid isthmus-dependent), and 35 ATs were focal (either triggered or automatic). Adenosine administered during AT (at doses sufficient to result in AV block) terminated or transiently suppressed focal AT in 33 of 35 cases, whereas 8 of 8 macroreentrant ATs were adenosine insensitive (P<0.001). Twenty-eight of 35 focal ATs were located along the crista terminalis or tricuspid annulus.

CONCLUSIONS

The response of AT to adenosine can immediately differentiate atrial tachycardia arising from a focal source from that attributable to macroreentry. This finding can be exploited to facilitate developing a focused, strategic ablative approach at the onset of a procedure.

Anatomic determinants of atrial arrhythmias: New insights from three-dimensional mapping

The recent development of new technologies for in vivo three-dimensional mapping of arrhythmias has enabled a better understanding of the richness of intracardiac anatomy and the relationship between anatomy and arrhythmogenesis. In the present manuscript we review two new technologies for in vivo mapping of atrial arrhythmias and explores the degree to which the anatomic complexity they reveal is important in determining the physiology of both focal and macroreentrant atrial tachycardias. These observations highlight the importance of including sufficient anatomic detail in modeling studies aimed at elucidating the pathophysiology of atrial arrhythmias. (c) 2002 American Institute of Physics.

Electrophysiological characteristics and radiofrequency ablation of focal atrial tachycardia originating from the superior vena cava

The initiation of focal atrial tachycardia (AT) from the superior vena cava (SVC) remains unclear. In 3 patients (2 females, 1 male; aged 57, 66 and 50 years, respectively) with focal AT arising from different parts of the SVC, the AT occurred spontaneously, rather than being induced by electrical stimulation. The cycle length of the tachycardia was highly variable, ranging between 190 and 300 ms in patient 1, 180 and 320ms in patient 2, and 200 and 300ms in patient 3. The clinical or associated arrhythmias were atrial fibrillation (AF) (patients 1, 3) and atrial flutter (AFL) (patients 2, 3). A presumed SVC potential that was earlier than the activation of all the other mapping sites was recorded during AT at the lower anterior (15-mm above the atriocaval junction), the mid-anterior (25-mm above the atriocaval junction) and the lower posterior aspect of the SVC (17-mm above the atriocaval junction. Radiofrequency (RF) ablation targeting the SVC focus with the SVC potential promptly eliminated the focal AT in all 3 patients. The coexistent typical AFL was ablated, but the AF was not. The follow-up period was 6, 6, and 3 months, respectively, for each of the patients under no antiarrhythmic medication; there has not been a recurrence of symptomatic palpitation. In conclusion, focal electrical firing in the SVC can initiate AT and this type of focal AT is always associated with AFL or AF. RF ablation guided by the presumed SVC potential is safe and highly effective in eliminating the tachycardia.

Lidocaine-sensitive atrial tachycardia: lidocaine-sensitive, rate-related, repetitive atrial tachycardia: a new arrhythmogenic syndrome

OBJECTIVES

The goal of this study was to report a variety of atrial tachycardia that might be caused by an unusual electrophysiologic substrate.

BACKGROUND

The mechanism of atrial tachycardias is attributed to re-entry, abnormal automaticity or triggered activity, based on their electropharmacological responses. A rate-related and lidocaine-sensitive atrial tachycardia has not been reported.

METHODS

Eight patients (3 women and 5 men, aged 14 to 60 years) with repetitive, uniform atrial tachycardias were studied. In six patients the arrhythmia had been refractory to at least three antiarrhythmic agents (class 1A and C sodium channel blockers, amiodarone, beta-adrenergic blocking agents, verapamil, digoxin). Conventional electrocardiograms, Holter recordings and B mode echocardiograms were performed in each patient. Intravenous lidocaine and verapamil were tested in the eight patients. Six patients underwent an electrophysiologic study.

RESULTS

The baseline electrocardiogram showed nearly incessant runs of atrial tachycardia in all patients. The mean atrial ectopic cycle length ranged from 376 to 502 ms. In seven patients a progressive prolongation of the cycle length from the beginning to the end of the salvos was documented. The arrhythmia was suppressed by increments of sinus node rate and by atrial pacing at cycle lengths longer than that of the atrial tachycardia. In all patients the arrhythmia was abolished by intravenous lidocaine, whereas intravenous verapamil was ineffective. Four symptomatic patients were successfully treated with radiofrequency ablation of the ectopic focus, and two patients were treated with oral mexiletine.

CONCLUSIONS

The peculiar electropharmacological responses of this arrhythmia suggest an uncommon underlying mechanism that remains to be elucidated.