Atypical atrial flutter originating in the right atrial free wall

Localized Re-Entry Is a Frequent Mechanism of De Novo Atypical Flutter

BACKGROUND

Limited data exist about the origins and mechanisms of atypical atrial flutter that occurs in the absence of prior ablation or surgery.

OBJECTIVES

The aims of this study were to report a large cohort of patients who presented for catheter ablation of de novo atypical flutters, to identify the most common locations and mechanisms of arrhythmia, and to describe outcomes after ablation.

METHODS

Demographic, electrophysiological, and outcome data were collected for patients who underwent ablation of de novo atypical flutter.

RESULTS

The mechanisms of 85 atypical flutters were identified in 62 patients and localized to the left atrium (LA) in 58 and right atrium (RA) in 27. In the LA, mechanisms were classified as macro-re-entry in 29 (50%) and localized re-entry in 29 (50%), whereas in the RA, mechanisms were macro-re-entry in 8 (30%) and localized re-entry in 19 (70%) (proportion of localized re-entry in the LA vs. RA, P = 0.08). Nine patients had both localized and macro-re-entrant atypical flutters. In the LA, localized re-entry was commonly found in the anterior LA, followed by the pulmonary veins and septum. In the RA, localized re-entry was found at various sites, including the lateral or posterior RA, septum, and coronary sinus ostium. During 39.4 months (Q1-Q3: 18.2-65.8 months) of follow-up, atrial arrhythmias occurred in 66% of patients after a single ablation and in 50% after >1 ablation. Among patients who underwent repeat ablation, compared with the index arrhythmia, different tachycardia circuits or arrhythmias were documented in 13 of 18 cases (72%).

CONCLUSIONS

Atypical atrial flutters in patients without prior surgery or complex ablation are often due to localized re-entry (approximately 50% in the LA and a higher frequency in the RA). Other atrial tachycardias commonly occur during long-term follow-up following ablation, suggesting progressive atrial myopathy in these patients.

Characteristics and Ablation Outcomes of Atrial Tachycardia in Patients with Prior Cardiac Surgery vs. Spontaneous Scars: Where Are the Differences?

(1) Background: Atrial scars play an important role in atrial tachycardia (AT). They can not only be found in patients with prior cardiac surgery (PCS) but also in patients without PCS or significant structural heart disease, in which case the scar is called a spontaneous scar (SS). This study aims to compare the characteristics, mechanisms and ablation outcomes of AT in patients with PCS and SS. (2) Methods: We retrospectively reviewed electrophysiological and ablative characteristics of ATs in 46 patients with PCS and 18 patients with SS. (3) Results: There were averages of 1.52 and 2.33 ATs per patient in the PCS group and SS group, respectively (p < 0.01). Cavo-tricuspid isthmus dependent atrial flutter (CTI-AFL) was presented in most patients in both groups (93.50% vs. 77.80%, p = 0.17), whereas the SS group had a higher occurrence of scar-mediated reentrant AT (SMAT) and focal AT (FAT) compared with the PCS group (88.90% vs. 39.10%, p < 0.01; 22.2% vs. 2.2%, p < 0.05). There were no significant differences in acute success rate between the two groups, whereas patients with SS had lower long-term success rate (87.0% vs. 61.1%, p < 0.05) and higher occurrence of sinus node dysfunction (SND) (4.3% vs. 22.2%, p < 0.05). (4) Conclusions: CTI-AFL is common in both patients with PCS and SS, and routine CTI ablation is recommended. Compared with patients with PCS, patients with SS have more ATs, especially with higher occurrence of SMAT and FAT, and had a lower long-term success rate and higher incidence of SND.

Interpretation of Typical and Atypical Atrial Flutters by Precision Electrocardiology Based on Intracardiac Recording

Atrial flutter is a term encompassing multiple clinical entities. Clinical manifestations of these arrhythmias range from typical isthmus-dependent flutter to post-ablation microreentries. Twelve-lead electrocardiogram (ECG) is a diagnostic tool in typical flutter, but it is often unable to clearly localize atrial flutters maintained by more complex reentrant circuits. Electrophysiology study and mapping are able to characterize in fine details all the components of the circuit and determine their electrophysiological properties. Combining these 2 techniques can greatly help in understanding the vectors determining the ECG morphology of the flutter waveforms, increasing the diagnostic usefulness of this tool.

Pathophysiology of Atypical Atrial Flutters

Atypical atrial flutters are complex supraventricular arrhythmias that share different pathophysiological aspects in common. In most cases, the arrhythmogenic substrate is essentially embodied by slow-conducting areas eliciting re-entrant circuits. Although atrial scarring seems to promote slow conduction, these arrhythmias may occur even in the absence of structural heart disease. To set out the ablation strategy in this setting, three-dimensional mapping systems have proved invaluable over the last decades, helping the cardiac electrophysiologist understand the electrophysiological complexity of these circuits and easily identify critical areas amenable to effective catheter ablation.

Mapping and Ablation of Atypical Atrial Flutters

Atypical atrial flutters are complex, hard-to-manage atrial arrhythmias. Catheter ablation has progressively emerged as a successful treatment option with a remarkable role played by irrigated-tip catheters and 3D electroanatomic mapping systems. However, despite the improvement of these technologies, the ablation results may be still suboptimal due to the progressive atrial substrate modification occurring in diseased hearts. Hence, a patient-tailored approach is required to improve the long-term success rate in this scenario, aiming at achieving specific procedure end points and detecting any potential arrhythmogenic substrate in each patient.

Extensive right atrial free wall low-voltage zone as the substrate for atrial fibrillation: successful ablation by scar homogenization

AIMS

Prior studies have described a variety of mechanisms for atrial fibrillation (AF) originating in the right atrium (RA). In this study, we report a series of patients in whom an extensive right atrial free wall low-voltage zone (LVZ) served as the AF substrate.

METHODS AND RESULTS

Five patients with a clinical syndrome of paroxysmal AF and atrial tachycardia (AT) underwent electrophysiologic evaluation. Five patients (3 M; age 52 ± 7 years) had symptomatic paroxysmal AF for (28 ± 17 months) not responsive to medical therapy. At the initial EP study, AT was inducible in four patients and was spontaneous in one patient. In all patients, tachycardia instability precluded detailed AT mapping. Sinus or pace maps indicated an extensive LVZ in the lateral RA trabeculated free wall which consisted of regions of low amplitude complex signals interspersed between electrically silent areas. Radiofrequency ablation aimed at rendering the LVZ electrical inert was successful in eliminating AF in four of five patients. At a follow-up of 28 ± 15 months, one patient had an isolated recurrence of AF. However, two patients required repeat ablation for recurrent AT.

CONCLUSION

An extensive LVZ in the trabeculated RA free wall constitutes an unusual substrate for AF. These patients also demonstrate unstable ATs originating from the same zone. Radiofrequency ablation to render the low-voltage zone electrically inert is an effective strategy to manage AF and AT.

Phase singularity point tracking for the identification of typical and atypical flutter patients: A clinical-computational study

Atrial Flutter (AFL) termination by ablating the path responsible for the arrhythmia maintenance is an extended practice. However, the difficulty associated with the identification of the circuit in the case of atypical AFL motivates the development of diagnostic techniques. We propose body surface phase map analysis as a noninvasive tool to identify AFL circuits. Sixty seven lead body surface recordings were acquired in 9 patients during AFL (i.e. 3 typical, 6 atypical). Computed body surface phase maps from simulations of 5 reentrant behaviors in a realistic atrial structure were also used. Surface representation of the macro-reentrant activity was analyzed by tracking the singularity points (SPs) in surface phase maps obtained from band-pass filtered body surface potential maps. Spatial distribution of SPs showed significant differences between typical and atypical AFL. Whereas for typical AFL patients 70.78 ± 16.17% of the maps presented two SPs simultaneously in the areas defined around the midaxialliary lines, this condition was only satisfied in 5.15 ± 10.99% (p < 0.05) maps corresponding to atypical AFL patients. Simulations confirmed these results. Surface phase maps highlights the reentrant mechanism maintaining the arrhythmia and appear as a promising tool for the noninvasive characterization of the circuit maintaining AFL. The potential of the technique as a diagnosis tool needs to be evaluated in larger populations and, if it is confirmed, may help in planning ablation procedures.

Is proximal coronary sinus involved in the circuit in some cases of ECG "typical" atrial flutter?

AIM

It is commonly conceived that coronary sinus (CS) participates in atrial flutter (AFL) circuit but limited to the fibers surrounding its ostium. We evaluated the involvement of proximal CS in typical AFL.

METHODS

Twenty AFL patients underwent entrainment mapping using postpacing interval minus AFL cycle length (PPI-AFL CL) including CS where a decapolar catheter was positioned with proximal bipole 1 cm from the ostium.

RESULTS

We compared patients with proximal CS within the circuit (group 1, PPI-AFL CL ≤ 20 ms + concealed entrainment) and those without (group 2, PPI-AFL CL > 20 ms). Group 1 patients were older, 77.5 ± 4 vs 71 ± 12 years (P < 0.05). No difference was found in AFL CL, PPI-AFL CL at cavotricuspid isthmus (CTI) entry, plateau, and septal site. Group 1 patients had shorter PPI-AFL CL at proximal CS (9 ± 3 vs 40 ± 15 ms; P < 0.001) and fragmented mesodiastolic CS atrial potentials (APs) (106 ± 27 vs 58.5 ± 22 ms; P < 0.001). A mid-septal unexcitable scar was found in five of eight group 1 patients vs one of 12 group 2 patients (P < 0.05). All were ablated at CTI. A patient had AFL recurrence and underwent a second attempt: PPI-AFL CL was 60 ms at CTI entry and less than or equal to 20 ms at septal CTI and proximal CS; AFL was terminated 1 cm inside CS, applying RF at a fragmented AP.

CONCLUSION

Proximal CS appears to be involved in a substantial subset of typical AFL patients, in whom advanced age, fragmented CS APs, and the presence of right atrial scar are prevalent. Proximal CS might be considered as an un-"innocent by-stander," but able, in rare cases, to generate a second AFL circuit.

Spontaneous scar-based reentrant atrial flutter: Electrophysiologic characteristics and ablation outcome in a retrospective analysis

BACKGROUND

The understanding of spontaneous scar-based reentrant atrial arrhythmia is limited. We aim to characterize the electrophysiologic and mapping features of spontaneous scar-based atrial flutter (AFL) and outcomes of catheter ablation.

METHODS

Consecutive patients with a diagnosis of AFL who underwent catheter ablation from January 2012 to June 2015 were screened. Scars were detected in 12 patients and were included in this study. All had negative coronary angiography. These patients were divided into right AFL (seven patients) and left AFL groups (five patients) based on electrophysiologic mappings.

RESULTS

Compared to patients with right AFL, the size of right atrium (RA) was smaller and left atrium (LA) was larger in the left AFL group. The proportion of the scar area was 11.1 ± 11.7 % in the RA AFL group and 7.8 ± 2.8 % in the LA AFL group. The difference was significant (P = 0.001). The acute success rates of ablation were 85.7% and 100%, respectively, in patients with right and left AFL (P = 0.304). During the follow-up, expansion of the scar area was noted in three patients with recurrent right AFL. No scar expansion was noted in one patient with recurrent left AFL. In addition, three patients with right AFL required permanent pacemaker implantation for sinus node dysfunction, and no one required pacemaker in patients with left AFL.

CONCLUSIONS

Spontaneous scar could serve as substrate for AFL in RA or LA. Compared to left AFL, there was a higher rate of recurrence and pacemaker implantation in patients with right AFL.

Catheter Ablation of Incisional Atrial Tachycardia

Tachycardias after atrial incisions represent frequent and serious problem. The majority of them are based on a re-entry electrical activation around a combination of anatomic and surgically created obstacles. Considering significant progress of cardiovascular surgery during the last decade along with potential large amount of open-heart procedures in the near future the number of incisional tachycardias has a tendency to increase. The aim of this work was to quantify the magnitude of the problem, characterize the tachycardias after different surgical operations and to analyze possible interventional treatment strategies. Nowadays evolution of mapping and ablation technologies may contribute to radically treatment of this type of arrhythmias while there are still a lot of issues that should be solved to improve the results of interventional treatment of incisional tachycardias.

Atrial Flutter, Typical and Atypical: A Review

Clinical electrophysiology has made the traditional classification of rapid atrial rhythms into flutter and tachycardia of little clinical use. Electrophysiological studies have defined multiple mechanisms of tachycardia, both re-entrant and focal, with varying ECG morphologies and rates, authenticated by the results of catheter ablation of the focal triggers or critical isthmuses of re-entry circuits. In patients without a history of heart disease, cardiac surgery or catheter ablation, typical flutter ECG remains predictive of a right atrial re-entry circuit dependent on the inferior vena cava-tricuspid isthmus that can be very effectively treated by ablation, although late incidence of atrial fibrillation remains a problem. Secondary prevention, based on the treatment of associated atrial fibrillation risk factors, is emerging as a therapeutic option. In patients subjected to cardiac surgery or catheter ablation for the treatment of atrial fibrillation or showing atypical ECG patterns, macro-re-entrant and focal tachycardia mechanisms can be very complex and electrophysiological studies are necessary to guide ablation treatment in poorly tolerated cases.

P wave morphology in guiding the ablation strategy of focal atrial tachycardias and atrial flutter

Focal atrial tachycardias arise preferentially from specific locations within the atria. Careful analysis of the P wave can provide useful information about the chamber and likely site of origin within that chamber. Macro-reentrant atrial flutter also tends to occur over a limited number of potential circuits. In this case, the ECG usually gives a guide to the chamber of origin, but unless it shows a specific morphology it is less useful in delineating the circuit involved. Nonetheless, prior knowledge of the likely chamber of origin helps to plan the ablation strategy.

Catheter ablation of atrial arrhythmias: state of the art

Catheter ablation is at the forefront of the management of a range of atrial arrhythmias. In this Series paper, we discuss the underlying mechanisms and the current role of catheter ablation for the three most common atrial arrhythmias encountered in clinical practice: focal atrial tachycardia, atrial flutter, and atrial fibrillation. The mechanisms of focal atrial tachycardia and atrial flutter are well understood, and these arrhythmias are amenable to curative catheter ablation with high success rates. In most cases, paroxysmal atrial fibrillation is initiated by triggers located within pulmonary vein musculature. Circumferential ablation to isolate this musculature is associated with high success rates for elimination of paroxysmal atrial fibrillation in selected populations. Because of the problem of recurrent pulmonary vein connection, more than one procedure will be needed in about 30% of patients, and new technologies are being developed to reduce this occurrence. The mechanisms that sustain persistent atrial fibrillation are not well understood and are the subject of continuing investigation. As such, ablation approaches and technologies for this arrhythmia are still evolving.

Arrhythmias (IV). Clinical approach to atrial tachycardia and atrial flutter from an understanding of the mechanisms. Electrophysiology based on anatomy

In 2009, 2343 catheter ablation procedures were performed in Spain for focal atrial tachycardia or atrial flutter (typical and atypical), with a yearly growth rate of 8%, indicating the clinical importance of these arrhythmias. The classic categorization of atrial tachycardia and atrial flutter based on rate and morphological criteria has become almost irrelevant at a time when clinical electrophysiology may lead to curative intervention based on a definition of the mechanism, making it necessary to bring laboratory experience closer to clinical practice. In this review we outline our present understanding of atrial tachycardia mechanisms, both focal and macroreentrant, and attempt to establish the conceptual links with classic concepts that may help the clinician to make a differential diagnosis and establish therapeutic indications, including that of an electrophysiologic study. Some of the concepts may seem complex, but we thought it important to provide an overview of the electrophysiological methods that may eventually lead to the description of the anatomic bases of the arrhythmias; currently, these are easier to understand thanks to the virtual anatomic casts built using computerized navigation systems.

Radiofrequency ablation of coronary sinus-dependent atrial flutter guided by fractionated mid-diastolic coronary sinus potentials

Background

The efficacy of radiofrequency (RF) ablation of an uncommon coronary sinus (CS)-dependent atrial flutter (AFL) was evaluated using conventional electrophysiological criteria in a highly selected subset of patients with typical and atypical AFL.

Methods

Fourteen patients with atrial flutter (11 males, mean age 69 ± 9 years) without previous right or left atrial RF ablation were included. Heart disease was present in eight patients. Baseline ECG suggested typical AFL in 12 patients and atypical AFL in two. Mean AFL cycle length was 324 ± 64 ms at the time of RF ablation in the CS. Lateral right atrium activation was counterclockwise (CCW) in 13 patients and clockwise in one. CS activation was CCW in all. Criteria for CS ablation included the presence of CS mid-diastolic fractionated atrial potentials (APs) associated with concealed entrainment with a postpacing interval within 20 ms. Success was defined as termination of AFL and subsequent noninducibility.

Results

The initial target for ablation was the cavotricuspid isthmus (CTI) in 11 patients and the CS with further CTI ablation in three. AP duration at the CS target site was 122 ± 33 ms, spanning 40 ± 12% of the AFL cycle length. CS ablation site was located 1–4 cm from the CS ostium. Ablation was successful in all patients. Mean time to AFL termination during CS ablation was 39 ± 52 s (<20 s in eight patients). No recurrence of ablated arrhythmia occurred during a follow-up of 18 ± 8 months.

Conclusions

The CS musculature is a critical part of some AFL circuits in patients with typical and atypical AFL. AFL can be terminated in patients with CS or CTI/CS AFL reentrant circuits by targeting CS mid-diastolic fragmented APs.

Electrical remodelling of the left and right atria due to rheumatic mitral stenosis

AIMS

To characterize the atrial remodelling in mitral stenosis (MS).

METHODS AND RESULTS

Twenty-four patients with severe MS undergoing commissurotomy and 24 controls were studied. Electrophysiological evaluation was performed in 12 patients in each group by positioning multi-electrode catheters in both atria to determine the following: effective refractory period (ERP) at 10 sites at 600 and 450 ms; conduction time; conduction delay at the crista terminalis (CT); and vulnerability for atrial fibrillation (AF). P-wave duration (PWD) was determined on the surface ECG. In the remaining 12 patients in each group, electroanatomic maps of both atria were created to determine conduction velocity and identify regions of low voltage and electrical silence. Patients with MS had larger left atria (LA) (P < 0.0001); prolonged PWD (P = 0.0007); prolonged ERP in both LA (P < 0.0001) and right atria (RA) (P < 0.0001); reduced conduction velocity in the LA (P = 0.009) and RA (P < 0.0001); greater number (P < 0.0001) and duration (P< 0.0001) of bipoles along the CT with delayed conduction; lower atrial voltage in the LA (P < 0.0001) and RA (P < 0.0001); and more frequent electrical scar (P = 0.001) compared with controls. Five of twelve with MS and none of the controls developed AF with extra-stimulus (P = 0.02).

CONCLUSION

Atrial remodelling in MS is characterized by LA enlargement, loss of myocardium, and scarring associated with widespread and site-specific conduction abnormalities and no change or an increase in ERP. These abnormalities were associated with a heightened inducibility of AF.

Prediction of the atrial flutter circuit location from the surface electrocardiogram

Identification of atypical atrial flutter (AFL) (non-cavo-tricuspid isthmus-dependent) prior to the electrophysiology laboratory is potentially useful because it allows appropriate procedural planning and enables discussion of the likely success rates and risks of the procedure with the patient. Typical counterclockwise AFL has a stereotypic appearance, the electrocardiogram (ECG) is predictive of the diagnosis in the majority of cases, and ablation procedures are associated with a high degree of safety and success. Atypical right atrial and left AFLs have a highly variable flutter wave morphology and may appear atypical, resemble typical flutter or appear to be focal in origin. Targeting these complex and often multiple re-entrant circuits is aided by expertise and use of electroanatomic mapping systems. This review will address whether there are clues from the 12-lead ECG which assist in the localization of AFL circuits.

Atrial macroreentry tachycardia in patients without obvious structural heart disease or previous cardiac surgical or catheter intervention: characterization of arrhythmogenic substrates, reentry circuits, and results of catheter ablation

INTRODUCTION

Atrial macroreentry tachycardia (AMRT) in patients without obvious structural heart disease or previous surgical or catheter intervention has not been characterized in detail.

METHODS AND RESULTS

Electroanatomical mapping and ablation of right or left AMRT were performed in 33 patients. Right atrial central conduction obstacle was formed by an electrically silent area (ESA) in 15 (68%) patients and by a line of double potentials (DPs) in seven (32%) patients. Left atrial ESAs were found in all 11 patients with the left AMRT. Reentry circuit was reconstructed in 19 (86%) patients with right AMRT and seven (64%) patients with left AMRT. Of the ESA-related right AMRT, eight (50%) were double-loop reentry circuits utilizing a narrow critical isthmus within the ESA and eight (50%) were single-loop reentry circuits with a critical isthmus bounded by ESA and either ostium of the vena cava. Single-loop DP-related AMRTs had the critical isthmus between the DP line and the ostium of the inferior vena cava (IVC). Left AMRTs included a variety of single-, double-, or triple-loop reentry circuits and their critical isthmuses. During the 37 +/- 15 month follow-up, atrial tachyarrhythmia-free clinical outcome was achieved in 21 (95%) patients (18 patients, 82%, without antiarrhythmic drugs) with the right AMRT and in nine (82%) patients (six patients, 55%, without antiarrhythmic drugs) with the left AMRT.

CONCLUSION

The majority of right and left AMRTs were related to the presence of ESA. Ablation can be successful with a favorable risk of atrial tachyarrhythmia recurrence.

Atrial flutter: from ECG to electroanatomical 3D mapping

Atrial flutter is a common arrhythmia that may cause significant symptoms, including palpitations, dyspnea, chest pain and even syncope. Frequently it’s possible to diagnose atrial flutter with a 12-lead surface ECG, looking for distinctive waves in leads II, III, aVF, aVL, V1,V2. Puech and Waldo developed the first classification of atrial flutter in the 1970s. These authors divided the arrhythmia into type I and type II. Therefore, in 2001 the European Society of Cardiology and the North American Society of Pacing and Electrophysiology developed a new classification of atrial flutter, based not only on the ECG, but also on the electrophysiological mechanism. New developments in endocardial mapping, including the electroanatomical 3D mapping system, have greatly expanded our understanding of the mechanism of arrhythmias. More recently, Scheinman et al, provided an updated classification and nomenclature. The terms like common, uncommon, typical, reverse typical or atypical flutter are abandoned because they may generate confusion. The authors worked out a new terminology, which differentiates atrial flutter only on the basis of electrophysiological mechanism.

Usefulness and limitations of the surface electrocardiogram in the classification of right and left atrial flutter

Atrial flutter is a common arrhythmia that may cause significant symptoms, including palpitations, dyspnoea, chest pain and even syncope. Frequently, it is possible to diagnose atrial flutter with a 12-lead surface electrocardiogram (ECG), looking for distinctive waves in leads II, III, aVF, aVL, V1 and V2. Puech and Waldo developed the first classification of atrial flutter in the 1970s. These authors divided the dysrhythmia into types I and II. Therefore, in 2001, the European Society of Cardiology and the North American Society of Pacing and Electrophysiology developed a new classification of atrial flutter based not only on the ECG, but also on the electrophysiological mechanism. More recently, Scheinman and colleagues have provided an updated classification and nomenclature. Terms such as common, uncommon, typical, reverse typical or atypical flutter are abandoned, because they may generate confusion. The authors worked out a new terminology, which differentiates atrial flutter only on the basis of electrophysiological mechanism.

Substrate Mapping to Detect Abnormal Atrial Endocardium With Slow Conduction in Patients With Atypical Right Atrial Flutter

OBJECTIVES

The purpose of this study was to investigate the relationship between the abnormal substrate and peak negative voltage (PNV) in the right atrium (RA) with atypical flutter.

BACKGROUND

The impact of a local abnormally low voltage electrogram on the local activation pattern and velocity of atrial flutter (AFL) remains unclear.

METHODS

Twelve patients with clinically documented AFL were included to undergo noncontact mapping of the RA. The atrial substrate was characterized by the: 1) activation mapping; 2) high-density voltage mapping; and 3) conduction velocity along the flutter re-entrant circuit. The normalized PNV (i.e., the relative ratio to the maximal PNV) in each virtual electrode recording was used to produce the voltage maps of the entire chamber. The protected isthmus was bordered by low voltage zones.

RESULTS

Atypical AFL of the RA was induced by atrial pacing in 12 patients, including 10 upper loop re-entry and 2 RA free wall re-entry flutter. These protected isthmuses were located near the crista terminalis. The mean width of the protected isthmus was 1.7 +/- 0.3 cm and mean voltage at the isthmus was -0.91 +/- 0.39 mV. The conduction velocities within these paths were significantly slower than outside the path (0.30 +/- 0.18 m/s vs. 1.14 +/- 0.41 m/s, respectively; p = 0.004). The ratiometric PNV of 37.6% of the maximal PNV had the best cut-off value to predict slow conduction, with a high sensitivity (92.3%) and specificity (85.7%).

CONCLUSIONS

Characterization of the RA substrate in terms of the unipolar PNV is an effective predictor of the slow conduction path within the critical isthmus of the re-entrant circuit.

Progressive and Persistent Atrial Inexcitability

Sinus node disease is characterized by the presence of significant sinus bradycardia or prolonged sinus pauses, and is attributed to either primary failure of sinus node automaticity or sino-atrial conduction disturbance. We present two patients with symptomatic bradycardia due to idiopathic global atrial inexcitability.

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

BACKGROUND

Few descriptions of right atrial macroreentrant atrial tachycardia involving regions of spontaneous "scar" have been reported.

OBJECTIVES

We describe the electrocardiographic, electrophysiologic, and electroanatomic characteristics of an unusual RA macroreentrant atrial tachycardia in eight patients with spontaneous RA scarring.

METHODS

Eight of 286 patients with macroreentrant atrial tachycardia treated with radiofrequency ablation had RA spontaneous scarring and underwent conventional electrophysiologic studies and electroanatomic mapping.

RESULTS

Eight patients (age 53 +/- 12 years) had symptoms for 58 +/- 62 months and had not responded to 2.5 +/- 0.8 antiarrhythmic drugs and 1.0 +/- 0.9 DC cardioversions. All patients had overall normal systolic function, and five had mild atrial enlargement. Scarring was present in the posterolateral wall extending from the crista terminalis toward the tricuspid annulus. The proportion of RA classified as scar was 31% +/- 14% (range 11%-46%). Stable circuits were around scar in seven patients, through a "channel" within the scar in four, and typical cavotricuspid isthmus-dependent flutter in five. Radiofrequency ablation sites included the cavotricuspid isthmus; between the inferior vena cava, superior vena cava, or crista terminalis and scar; or a channel in the scar. ECG morphology of the RA free wall tachycardias varied, depending upon whether cavotricuspid isthmus block was present. Radiofrequency ablation of all inducible circuits was successful in six patients and of all clinical circuits in seven. At follow-up of 20 +/- 13 months, six patients are free from macroreentrant atrial tachycardia, one has infrequent nonsustained macroreentrant atrial tachycardia, and one is controlled with previously ineffective medication. Five had sinus node dysfunction requiring permanent pacemaker implant.

CONCLUSIONS

Extensive spontaneous scarring of the RA is an unusual cause of macroreentrant atrial tachycardias, both cavotricuspid isthmus dependent and independent in the same patient. Radiofrequency ablation is an effective treatment. Sinus node dysfunction requiring permanent pacemaker is common. The cause is unknown.

Right Atrial Tachycardia in a Patient with Severe Atrial Conduction Disturbances and an Anatomically Normal Heart

We describe a case of abnormal right atrial (RA) conduction in a patient with atrial tachycardia (AT) but no history of structural heart disease or cardiac surgery. Following ablation of AT, the patient experienced typical atrial flutter (AFL) and a postcardioversion ECG suggestive of low atrial rhythm. Repeat EPS and three-dimensional electroanatomic activation mapping showed unusual RA activation during SR. This case illustrates the possibility that abnormal intraatrial conduction may lead to unusual patterns of activation in the RA which can serve as a necessary substrate for the initiation and maintenance of macro-reentry circuits.

Value of entrainment mapping in determining the isthmus-dependent nature of atrial flutter in the presence of amiodarone

INTRODUCTION

Entrainment mapping is a useful procedure for localizing macroreentrant tachycardia circuits. In patients with isthmus-dependent atrial flutter, entrainment mapping from the isthmus during tachycardia results in postpacing intervals (PPI) close to the tachycardia cycle length (TCL). However, the influence of antiarrhythmic drugs on the method's value is not clearly established. The aim of our study was to assess the value of entrainment mapping in the presence of amiodarone in patients undergoing radiofrequency ablation (RFA) of isthmus-dependent atrial flutter.

METHODS AND RESULTS

The study consisted of 83 patients with isthmus-dependent atrial flutter: 52 were taking amiodarone at the time of RFA (group 1) and 31 were in a drug-free state (group 2). Entrainment mapping was performed from the cavotricuspid isthmus, and PPI minus TCL was determined. The two groups had similar baseline clinical characteristics. In all patients, RFA of the isthmus resulted in termination of tachycardia, confirming the isthmus-dependent nature of the flutter. TCL was significantly longer in group 1 than in group 2 (263 +/- 31 msec vs 238 +/- 27 msec, P < 0.0002). PPI minus TCL at the isthmus was significantly longer in group 1 than in group 2 (17 +/- 17 msec vs 8 +/- 4 msec, P < 0.01). More patients in group 1 had PPI-TCL>20 msec compared to group 2 (37% vs 10%, P = 0.01).

CONCLUSION

Amiodarone significantly alters the entrainment mapping response from the isthmus. In this setting, long return cycles exceeding the TCL by >20 msec do not exclude isthmus-dependent atrial flutter.

Non-contact mapping to guide radiofrequency ablation of atypical right atrial flutter

OBJECTIVES

This study was aimed at evaluating the efficacy of non-contact mapping and ablation of non-incisional atypical right atrial (RA) flutters.

BACKGROUND

The majority of atypical RA flutters were reported in patients after surgical incision of the RA.

METHODS

The study group consisted of 15 patients (61 +/- 13 years, 8 males) with atypical atrial flutter (AFL). The RA activation during AFL was delineated using a non-contact mapping system (EnSite 3000 with Precision Software, Endocardial Solutions, St. Paul, Minnesota). The narrowest part of each reentrant circuit was targeted using radiofrequency energy.

RESULTS

In all 15 patients, non-contact mapping showed AFLs confined to the RA with RA activation time accounting for 100% of the cycle length (210 +/- 19 ms). During single-loop re-entry in seven patients, the activation wave front circulated around the central obstacle (CO) in the anterolateral wall with conduction through the channel between the CO and the crista terminalis (CT). During figure-of-eight re-entry in eight patients, simultaneous upper and lower loop re-entry through the conduction gap in the CT was found in four patients, and simultaneous upper loop and free-wall single-loop re-entry was observed in four patients. Radiofrequency ablation of the free-wall channel and/or CT gap was effective in eliminating these AFLs in 13 patients. During a follow-up of 16.8 +/- 3.8 months, two patients had recurrence of left AFL, and one had recurrence of atrial fibrillation.

CONCLUSIONS

Atypical RA flutters could arise from single-loop or double-loop figure-of-eight re-entry. Radiofrequency ablation of the free-wall channel and/or the CT gap was effective in eliminating these arrhythmias.

Noncontact and Electroanatomic Mapping of Atrial Flutter in Surgically Repaired Sinus Venosus Atrial Septal Defect and Rerouting of Anomalous Pulmonary Venous Drainage

Atypical atrial flutter with two prior failed ablations, complicating surgically repaired sinus venosus atrial septal defect and partial anomalous pulmonary venous connection, mapped by noncontact and electroanatomic mapping, is described. Electroanatomic and noncontact mapping clearly identified a narrow zone of normal voltage and activation which was targeted, with successful termination of the arrhythmia.

Atypical flutter: a review

Understanding of typical flutter circuits led the way to the study of other forms of macroreentrant tachycardias of the atria, and to their treatment by catheter ablation. It has become evident that the ECG classification of atrial flutter and atrial tachycardia by a rate cutoff and the presence or absence of isoelectric baselines between atrial deflections is not a valid indicator of tachycardia mechanism. Macroreentrant circuits where activation rotates around large obstacles are the most common arrhythmias found in patients with atypical forms of flutter or atrial tachycardia, especially after surgery for congenital heart disease, however, focal mechanisms can also be found. Large areas of low voltage electrograms, suggestive of severe myocardial damage (fibrosis or infiltration) can be found in many atypical macroreentrant tachycardias at the center of the circuit. Many of these circuits can be mapped precisely, critical isthmuses can be defined, and effective catheter ablation can be performed. The need to match activation maps with anatomy precisely, makes computer assisted, anatomically precise mapping a useful tool. Entrainment techniques have to be used sparingly to avoid tachycardia interruption. In complex cases, ablation can be done in sinus rhythm, after definition of conducting channels between low voltage areas and scars or anatomic obstacles. Long-term prognosis is uncertain and depends on the underlying pathology.