Electrocardiographic and electrophysiologic characterization of atypical atrial flutter in man: use of activation and entrainment mapping and implications for catheter ablation

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.

Atypical atrial flutter: review of mechanisms, advances in mapping and ablation outcomes

PURPOSE OF REVIEW

Atrial flutter (AFL) is the second most prevalent arrhythmia after atrial fibrillation (AF). It is a macro-reentrant tachycardia that is either cavotricuspid isthmus dependent (typical) or independent (atypical). This review aims at highlighting mechanism, diagnosis and treatment of atypical AFL and the recent developments in electroanatomic mapping.

RECENT FINDINGS

Incidence of left AFL is at an exponential rise presently with increase in AF ablation rates. The mechanism of left AFL is most often peri-mitral, roof-dependent or within pulmonary veins in preablated, in contrast to posterior or anterior wall low voltage areas in ablation naïve patients. Linear lesions, compared to pulmonary vein isolation alone, have higher incidence of atypical right or left AFL. Catheter ablation for atypical AFL is associated with lower rates of thromboembolic events, transfusions, and length of stay compared to typical AFL.

SUMMARY

Advances in mapping have allowed rapid simultaneous acquisition of automatically annotated points in the atria and identification of details of macro-reentrant circuits, including zones of conduction block, scar, and slow conduction.

Significance of post-pacing intervals shorter than tachycardia cycle length for successful catheter ablation of atypical flutter

AIMS

During entrainment mapping of macro-reentrant tachycardias, the time difference (dPPI) between post-pacing interval (PPI) and tachycardia cycle length (TCL) is thought to be a function of the distance of the pacing site to the re-entry circuit and dPPI < 30 ms is considered within the re-entry circuit. This study assessed the importance of PPI < TCL as a successful target for atypical flutter ablation.

METHODS AND RESULTS

A total of 177 ablation procedures were investigated. Surface electrocardiograms (ECGs) were evaluated and combined activation and entrainment mapping were performed to choose ablation sites. Each entrainment sequence immediately preceding static radiofrequency delivery at the same site was analysed. A total of 545 entrainment sequences were analysed. dPPI < 0 ms was observed in 45.3% (247/545) sequences. Ablation resulted in tachycardia termination more often at sites with dPPI < 0 (27.8% vs. 14.5%, P < 0.001) and with a progressively increasingly inverse correlation between dPPI duration and ablation success [odds ratio (OR): 0.974; 95% confidence interval (CI) 0.960-0.988; P < 0.001]. Tachycardia termination or cycle length prolongation also occurred more often at sites with dPPI < 0 (50.6% vs. 33.2%, P < 0.001) and with a similar inverse correlation with dPPI duration (OR: 0.972; 95% CI 0.960-0.984; P < 0.001). Twelve-lead synchronous isoelectric intervals were observed in 64.4% (163/253) flutter ECGs and were associated with a dPPI < 0 (75.3% vs. 55.8%, P < 0.001).

CONCLUSION

When combined with activation mapping, a negative dPPI is a more effective parameter for identifying a target for successful ablation compared to a dPPI = 0-30 ms. Its occurrence is associated with a critical small narrow slow-conducting isthmus at the target site.

Comparison of clockwise and counterclockwise right atrial flutter using high-resolution mapping and automated velocity measurements

BACKGROUND

Only few studies have been performed that explore the electrophysiological differences between clockwise (CW) and counterclockwise (CCW) right atrial (RA) cavotricuspid isthmus (CTI)-dependent atrial flutter (AFL) using the high-resolution Rhythmia mapping system.

OBJECTIVES

We sought to compare CW and CCW CTI-dependent AFL in pure right AFL patients (pts) using the ultra-high-definition (ultra-HD) Rhythmia mapping system and we mathematically developed a cartography model based on automatic velocity RA measurements to identify electrophysiological AFL specificities.

METHODS AND RESULTS

Thirty-three pts were recruited. The mean age was 71 ± 13 years old. The sinus venosus (SV) block line was present in 32/33 of cases (97%) and no significant difference was found between CCW and CW CTI AFL (100% vs. 91%; p = .7). No line was localized in the region of the crista terminalis (CT). A superior gap was present in the posterior line in 14/31 (45.2%) but this was similarly present in CCW AFL, when compared to CW AFL (10/22 [45.5%] vs. 4/10 [40%]; p = .9). When present, the extension of the posterior line of block was observed in 18/31 pts (58%) without significant differences between CCW and CW CI AFL (12/22 [54.5%] vs. 6/10 [60%]; p = .9) The Eustachian ridge line of block was similarly present in both groups (82% [18/22] vs. 45.5% [5/11]; p = .2). The absence of the Eustachian ridge line of block led to significantly slowed velocity in this area (28 ± 10 cm/s; n = 8), and the velocities were similarly altered between both groups (26 ± 10 [4/22] vs. 29.8 ± 11 cm/s [4/11]; p = .6). We created mathematical, three-dimensional RA reconstruction-velocity model measurements. In each block localization, when the block line was absent, velocity was significantly slowed (≤20 cm/s). A systematic slowdown in conduction velocity was observed at the entrance and exit of the CTI in 100% of cases. This alteration to the conduction entrance was localized at the lateral side of the CTI for the CCW AFL and at the septal side of the CTI for CW AFL. The exit-conduction alteration was localized at the CTI septal side for the CCW AFL and at the CTI lateral side for the CW AFL.

CONCLUSION

The ultra-HD Rhythmia mapping system confirmed the absence of significant electrophysiological differences between CCW and CW AFL. The mechanistic posterior SV and Eustachian ridge block lines were confirmed in each arrhythmia. A systematic slowing down at the entrance and exit of the CTI was demonstrated in both CCW and CW AFL, but in reverse positions.

Ultra-high resolution mapping of reverse typical atrial flutter: electrophysiological properties of a right atrial posterior wall and interatrial septum activation pattern

PURPOSE

We aimed to elucidate the right atrial posterior wall (RAPW) and interatrial septum (IAS) conduction pattern during reverse typical atrial flutter (clockwise AFL: CW-AFL).

METHODS

This study included 30 patients who underwent catheter ablation of CW-AFL (n = 11) and counter-clockwise AFL (CCW-AFL; n = 19) using an ultra-high resolution mapping system. RAPW transverse conduction block was evaluated by the conduction pattern on propagation maps and double potentials separated by an isoelectric line. The degree of blockade was evaluated by the %blockade, which was calculated by the length of the blocked area divided by the RAPW length. IAS activation patterns were also investigated dependent on the propagation map.

RESULTS

The average %blockade of the RAPW was significantly smaller in patients with CW-AFL than those with CCW-AFL (25 [3-74]% vs. 67 [57-75]%, p < 0.05). CW-AFL patients exhibited 3 different RAPW conduction patterns: (1) a complete blockade pattern (3 patients), (2) moderate (> 25% blockade) blockade pattern (2 patients), and (3) little (< 25% blockade) blockade pattern (6 patients). In contrast, the little blockade pattern was not observed in CCW-AFL patients. Of 11 CW-AFL patients, 4, including all patients with an RAPW complete blockade pattern, had an IAS activation from the wavefront from the anterior tricuspid annulus (TA), and 6 had an IAS activation from the wavefronts from both the anterior TA and RAPW. One patient had IAS activation dominantly from the wavefront from the RAPW.

CONCLUSIONS

RAPW transverse conduction blockade during CW-AFL was less frequent than during CCW-AFL, which possibly caused various IAS activation patterns.

Coronary Sinus Activation and ECG Characteristics of Roof-Dependent Left Atrial Flutter After Pulmonary Vein Isolation

BACKGROUND

The electrocardiographic and intracardiac activation features of left atrial roof-dependent macroreentrant flutter have been incompletely characterized.

METHODS

Patients post-pulmonary vein (PV) isolation with roof-dependent atrial flutter based on activation and entrainment mapping were included. ECG and coronary sinus activation were compared with mitral annular (MA) flutter.

RESULTS

The roof-dependent left atrial flutter circled the right PVs in 32 of 33 cases. Two forms of roof flutters were identified, posteroanterior, ascendant on posterior wall and descendant on anterior wall (n=24); and anteroposterior, ascendant on the anterior wall and descendent on the posterior wall (n=9). Both forms had positive large amplitude P waves in V₁ through V₂ with decreasing amplitude in V₃ through V₆. Posteroanterior roof flutters had positive P wave in the inferior and negative P wave in leads I and aVL similar to counterclockwise MA flutter, but coronary sinus activation was simultaneous for roof and proximal to distal for counterclockwise. Anteroposterior roof flutters were similar to clockwise MA flutter with negative P in inferior leads and transition to flat or negative P in V₃ through V₆. Coronary sinus activation time ≤39 ms identified roof versus MA flutter (sensitivity: 100% and specificity: 97%).

CONCLUSIONS

Roof-dependent flutter around right PVs is more common than around left PVs. The ECG pattern for roof-dependent flutter around right PVs is similar to MA flutter with frontal plane axis dictated by septal activation. Roof-dependent flutter can be distinguished from MA flutter by more simultaneous rather than sequential coronary sinus activation.

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.

Rapid Mapping of Right Atrial Tachycardia Using a New Multielectrode Basket Catheter

INTRODUCTION

The mapping of atrial tachycardia (AT) can often be challenging and time-consuming, especially in patients with ATs that develop following cardiac surgery or are concomitant with atrial fibrillation. Recently, a new multielectrode basket catheter (MBC) has become available; we hypothesized that the MBC could be utilized to diagnose AT circuits.

METHODS AND RESULTS

This study included 51 consecutive patients undergoing catheter ablation of clinically documented right-sided ATs (including 17 cases following cardiac surgery). Using a NavX system, 2 activation maps of the ATs were created, one using the new MBC (32 mm, 31 poles) and the other using a circular catheter. The time needed to complete the activation maps and the points acquired with both mapping catheters were compared. In all 64 ATs, including 34 non-cavotricuspid isthmus-dependent ATs, the AT activation maps created by both catheters were essentially identical. The number of points acquired to complete the activation maps did not differ significantly between the MBC and the circular catheter (387 [285-511] vs. 374 [269-533], P = 0.19), but the mapping time was significantly shorter using the MBC (4.0 [3.0-6.0] minutes vs. 8.0 [6.5-10.0] minutes, P < 0.0001). Inadvertent mechanical AT termination (n = 6) was observed only during mapping with the circular catheter.

CONCLUSION

In patients with right-sided ATs, the use of an MBC could save mapping time.

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.

Predictors of unusual ECG characteristics in cavotricuspid isthmus-dependent atrial flutter ablation

BACKGROUND

An unusual 12-lead electrocardiographic pattern may be present in patients with cavotricuspid isthmus (CTI)-dependent flutter.

OBJECTIVE

 Using baseline patient characteristics and echocardiography, we sought to study predictors of unusual electrocardiogram (ECG) characteristics in patients with CTI-dependent atrial flutter.

METHODS

 This was a dual-center, retrospective cohort study of 147 patients undergoing electrophysiology study and ablation for CTI-dependent atrial flutter.

RESULTS

Among this cohort, 23 patients (16%) had unusual 12-lead ECG characteristics. Using multivariate logistic regression, we found two clinical predictors for having an unusual ECG pattern. A clockwise (CW) pattern at time of electrophysiology study was the strongest predictor of an unusual ECG pattern (odds ratio 15.3, 95% confidence interval [CI] 4.0-59.4, P < 0.005). In addition, patients with decreased systolic function had a 3.5 greater odds (95% CI 1.1-11.5, P = 0.037) of having an unusual ECG pattern.

CONCLUSIONS

Our data demonstrate that among patients suffering from CTI-dependent atrial flutter who are referred for ablation, 16% will have unusual ECG patterns. Patients with CW atrial activation and left ventricle dysfunction have greater odds of manifesting unusual patterns by surface electrocardiogram.

Accurate ECG diagnosis of atrial tachyarrhythmias using quantitative analysis: a prospective diagnostic and cost-effectiveness study

Quantitative ECG Analysis.

INTRODUCTION

Optimal atrial tachyarrhythmia management is facilitated by accurate electrocardiogram interpretation, yet typical atrial flutter (AFl) may present without sawtooth F-waves or RR regularity, and atrial fibrillation (AF) may be difficult to separate from atypical AFl or rapid focal atrial tachycardia (AT). We analyzed whether improved diagnostic accuracy using a validated analysis tool significantly impacts costs and patient care.

METHODS AND RESULTS

We performed a prospective, blinded, multicenter study using a novel quantitative computerized algorithm to identify atrial tachyarrhythmia mechanism from the surface ECG in patients referred for electrophysiology study (EPS). In 122 consecutive patients (age 60 ± 12 years) referred for EPS, 91 sustained atrial tachyarrhythmias were studied. ECGs were also interpreted by 9 physicians from 3 specialties for comparison and to allow healthcare system modeling. Diagnostic accuracy was compared to the diagnosis at EPS. A Markov model was used to estimate the impact of improved arrhythmia diagnosis. We found 13% of typical AFl ECGs had neither sawtooth flutter waves nor RR regularity, and were misdiagnosed by the majority of clinicians (0/6 correctly diagnosed by consensus visual interpretation) but correctly by quantitative analysis in 83% (5/6, P = 0.03). AF diagnosis was also improved through use of the algorithm (92%) versus visual interpretation (primary care: 76%, P < 0.01). Economically, we found that these improvements in diagnostic accuracy resulted in an average cost-savings of $1,303 and 0.007 quality-adjusted-life-years per patient.

CONCLUSIONS

Typical AFl and AF are frequently misdiagnosed using visual criteria. Quantitative analysis improves diagnostic accuracy and results in improved healthcare costs and patient outcomes.

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.

Role of High Frequency Atrial Pacing for the Termination of Acute Atrial Fibrillation and Atypical Atrial Flutter

BACKGROUND

The aim of this study was to assess the efficacy of high-frequency (HF) pacing from the right atrial appendage (RAA) or coronary sinus ostium (CS-Os) for the termination of acute atrial fibrillation (AF) and atypical atrial flutter (AAFL) during an electrophysiological (EP) study.

METHODS

128 episodes of acute fast atrial arrhythmias (FAAs; 93 AF and 35 AAFL) were analyzed in 110 patients. Patients were initially observed for 60s leading to spontaneous termination of 28 FAAs. The remaining 100 FAAs (70 AF) episodes were randomized to the following strategies: (A) pacing at RAA using up to 10 consecutive 20-Hz trains followed by the same stimulation protocol at CS-Os if RAA pacing failed, (B) pacing at CS-Os using the same stimulation protocol followed by HF pacing at RAA, or (C) observation up to 6 minutes ("no pacing").

RESULTS

The 20-Hz pacing at both RAA and CS-Os was associated with higher conversion of AAFL, as compared to strategy C (60% and 77% vs 11%; P < 0.05). Only HF pacing at CS-Os was superior to observation strategy for the conversion of AF (21% vs 4%; P < 0.05).

CONCLUSIONS

The 20-Hz pacing protocol is superior to observation strategy for interruption of either acute AF or acute AAFL episodes; however, its efficacy is higher in AAFLs. These results can be helpful for the termination of acute atrial tachyarrhythmias during EPstudy and should be further evaluated in patients with implantable devices capable of antitachycardia pacing.

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.

Common atrial flutter and atrial fibrillation are not always two stages of the same disease. A long-term follow-up study in patients with atrial flutter treated with cavo–tricuspid isthmus ablation

OBJECTIVE

Both atrial flutter and atrial fibrillation (AF) frequently develop in the same patient. There is therefore reasonable doubt that flutter ablation may not solve the clinical problem, owing to the occurrence/recurrence of AF. The aim of this study was to establish whether cavo-tricuspid isthmus ablation is curative in patients with common atrial flutter alone or combined with AF.

METHODS

One hundred and forty-one patients (114 male, 27 female, mean age 63 +/- 10 years) who had cavo-tricuspid isthmus ablation were followed up for 44 +/- 20 months. Before ablation, 48 patients had only atrial flutter (group A), whereas 93 patients had both atrial flutter and AF. Among the latter, during antiarrhythmic therapy, 31 patients had only atrial flutter (group B1), whereas 62 patients (group B2) continued to experience both arrhythmias.

RESULTS

During follow-up, 27% of group A and 61% of group B patients had documented recurrent AF (P < 0.001). AF recurred in 51% of group B1 and in 66% of group B2 patients (P = NS). Permanent AF occurred in 6% of group A, 3% of group B1 and 21% of group B2 (P < 0.01). Specific symptom scale scores significantly decreased in all groups, particularly in group A. Two patients of group B had cerebral ischaemic attacks.

CONCLUSIONS

Over a long-term follow-up, cavo-tricuspid isthmus ablation is curative in >70% of patients with atrial flutter alone. Therefore, if no AF is documented, more extensive ablation is not needed. By contrast, cavo-tricuspid isthmus ablation is frequently unable to prevent AF in patients with both atrial flutter and AF, although in some cases a significant clinical benefit may be obtained.

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.

Entrainment mapping for rapid distinction of left and right atrial tachycardias

BACKGROUND

Distinguishing left from right atrial tachycardia is a critical step for guiding ablation.

OBJECTIVES

The purpose of this study was to develop and validate a simple algorithm predicting the location of macroreentrant atrial tachycardia (AT) circuits from limited entrainment mapping in right atrium (RA) and coronary sinus (CS).

METHODS

In 180 patients with organized reentrant AT, entrainment was performed at the high RA, proximal CS, and distal CS. The difference between the postpacing interval (PPI) and tachycardia cycle length (TCL) was calculated at each site. The location of the AT reentrant circuit was determined by mapping and ablation. An algorithm predicting AT regions was developed from 104 ATs in the first 90 patients (group I) and prospectively evaluated in a validation cohort of 106 ATs in the second 90 patients (group II).

RESULTS

In group I, PPI-TCL difference <50 or >50 ms at the high RA distinguished RA from LA reentrant circuits. For RA tachycardias, PPI-TCL difference at the proximal CS distinguished common flutter from lateral RA circuits. For LA circuits, PPI-TCL difference at the proximal and distal CS distinguished perimitral reentry from reentry involving the right pulmonary veins and septum. In group II, an algorithm based on PPI-TCL difference >50 or <50 ms at the high RA, proximal CS, or distal CS had sensitivity of 94%, specificity of 88%, and predictive accuracy of 93% for predicting the successful ablation region.

CONCLUSION

Limited entrainment from sites accessible from the RA can expeditiously suggest the AT location to guide more detailed mapping and potentially avoid unnecessary transseptal punctures in some patients.

Separating atrial flutter from atrial fibrillation with apparent electrocardiographic organization using dominant and narrow F-wave spectra

OBJECTIVES

The purpose of this study was to separate atrial flutter (AFL) with atypical F waves from fibrillation (AF) with "apparent organization."

BACKGROUND

We hypothesized that F-wave spectra should reveal a dominant and narrow peak in AFL, reflecting its single macro-re-entrant wave front, but broad spectra in AF, reflecting multiple wave fronts.

METHODS

We identified 39 patients with electrocardiograms (ECGs) of "AFL/AF" or "coarse AF" from 134 consecutive patients referred for ablation: 21 had AFL (18 atypical, 3 typical), 18 had AF, and all were successfully ablated. Filtered atrial ECGs were created by cross-correlating F waves to successive ECG time points. Dominant peaks between 3 and 10 Hz were identified from power spectra of X (lead V5), Y (aVF), and Z (V1) axes, and for each, we calculated height (relative to two adjacent spectral points) and area ratio to envelopes of bandwidth 0.625, 1.25, 2.5, 3.75, and 5 Hz (range 0 to 1, where higher ratios reflect narrower peaks).

RESULTS

Dominant peaks had greater relative height for AFL than AF (three-axis mean: 14.2 +/- 6.4 dB vs. 6.6 +/- 2.1 dB; p < 0.001). Peak area ratios were also higher for AFL than AF for all envelopes (p < 0.001). For the 2.5-Hz envelope, the separation (0.61 +/- 0.14 vs. 0.35 +/- 0.05, respectively; p < 0.001) enabled a ratio > or =0.44 to identify all cases of AFL from AF (p < 0.001). A panel of seven cardiologists blinded to clinical data provided lower diagnostic accuracy (82.1%; p < 0.01).

CONCLUSIONS

In ambiguous ECGs with atypical F waves, spectral evidence for a solitary activation cycle separates AFL from AF with "apparent organization." This approach might improve bedside ECG diagnosis and shed light on intra-atrial organization of both rhythms.

Clinical prediction of cavotricuspid isthmus dependence in patients referred for catheter ablation of "typical" atrial flutter

INTRODUCTION

Typical atrial flutter (AFL) can be cured by catheter ablation of the cavotricuspid isthmus (CTI). The surface electrocardiogram (ECG) is not always diagnostic of isthmus dependence of AFL. The aim of this study was to evaluate clinical parameters for the prediction of isthmus-dependent AFL.

METHODS AND RESULTS

Sixty consecutive adult patients without suspected atriotomy-related AFL, congenital heart disease, or previous AFL ablation, referred for catheter ablation of presumed typical AFL were studied. All patients had distinct flutter waves in the inferior leads, suggestive of CTI-dependent AFL, either on presentation to the electrophysiology (EP) lab or documented on prior ECG. Electrophysiology study was performed in the standard fashion. Patients who presented to the EP laboratory not in AFL underwent arrhythmia induction with a burst pacing protocol. A clinical history of persistent AFL (P = 0.0001) and existence of AFL on presentation to the EP laboratory (P = 0.0001) were strong predictors of CTI dependence. History of atrial fibrillation (P = 0.19), structural heart disease (P = 0.6), hypertension (P = 0.4), and previous cardiac surgery (P = 0.5), as well as the nature of AFL-related symptoms (P = 0.5), were not predictors of CTI-dependent AFL documented during EP study.

CONCLUSION

In patients with ECG suggestive of typical AFL, the presence of persistent rather than paroxysmal AFL and presentation to the EP laboratory in AFL are strong predictors of CTI-dependent AFL. A paroxysmal pattern of AFL predicts noninducibility of CTI-dependent AFL during EP study. CTI ablation may therefore be less effective in these patients.

Flutter-Like P Waves in a Case of Atrioventricular Reciprocating Tachycardia

Typical atrial flutter is characterized by its sawtooth flutter wave in leads II, III, aVF, and V1. Atrioventricular reciprocating tachycardia is characterized by its small retrograde P wave after completion of QRS complex, where sawtooth flutter-like P waves are rarely seen in the electrocardiogram during atrioventricular reciprocating tachycardia. We report on a 62-year-old patient who presented the characteristic sawtooth flutter-like P waves in the electrocardiogram during attack of supraventricular tachycardia. By electrophysiologic study, the mechanism of his supraventricular tachycardia was atrioventricular reciprocating tachycardia using the left posterior lateral concealed accessory pathway for retrograde conduction. The accessory pathway was successfully ablated by radiofrequency ablation therapy.

Superior Vena Cava Flutter: Electrophysiology and Ablation

INTRODUCTION

Reentry within a major thoracic vein has been suggested as a cause of atrial arrhythmias. However, little is known about these potential reentrant circuits.

METHODS AND RESULTS

Atypical atrial flutter was induced and mapped in 67 out of 225 atrial flutter ablation procedures. Reentry around the superior vena cava (SVC) was suspected in three patients. The suspected SVC flutter was induced and terminated by pacing in all patients. Fusion was demonstrated during flutter entrainment by subeustachian isthmus pacing in all of them. The postpacing interval following entrainment by pacing from different sites of the right atrium (RA) or coronary sinus was longer than the flutter cycle length. Macroreentry within the SVC was demonstrated both by sequential activation and a postpacing interval matching the flutter cycle length when pacing from different sites around the SVC in all patients. Atrial-venous-atrial electrogram sequence was demonstrated following flutter entrainment by atrial pacing. Flutter was terminated by an electrical stimulus delivered to the SVC, which was not propagated to the trabeculated RA, in one patient, and linear radiofrequency application from the distal SVC to the posterior wall of the RA, or to the superoseptal portion of the crista terminalis, in the other two.

CONCLUSION

Macroreentry within the SVC is a distinctive mechanism responsible for rapid atrial activation, which is different from other reported flutter mechanisms, such as upper loop reentry. SVC longitudinal radiofrequency application can eliminate the arrhythmia without the need for complete electrical disconnection of the vein.

Separating non-isthmus- from isthmus-dependent atrial flutter using wavefront variability

OBJECTIVES

The aim of this study was to separate isthmus-dependent atrial flutter (IDAFL) from non-isthmus-dependent atrial flutter (NIDAFL) from the electrocardiogram (ECG) based on functional differences.

BACKGROUND

The ECG analyses of F-wave shape suboptimally separate NIDAFL from IDAFL. The authors hypothesized that anatomic and functional differences may result in greater wavefront variability in NIDAFL than IDAFL, allowing their separation. The authors tested this hypothesis in patients undergoing ablation for atrial flutter using a novel ECG algorithm to detect subtle F-wave variability, validated by intracardiac measurements.

METHODS

In 62 patients (23 NIDAFL, 39 IDAFL) ECG atrial wavefronts were represented as correlations of an F-wave template to the ECG over time. Correlations in orthogonal ECG lead-pairs were plotted at each time point to yield loops reflecting temporal and spatial regularity in each plane. The ECG analyses were compared with intracardiac standard deviations of: 1) atrial electrograms (temporal variability), and 2) bi-atrial activation time differences (spatial variability).

RESULTS

Atrial ECG temporospatial loops were reproducible in IDAFL, but varied in NIDAFL (p < 0.01) suggesting greater variability that correctly classified IDAFL (39 of 39 cases) from NIDAFL (22 of 23 cases; p < 0.001). Intra-atrial mapping confirmed greater temporal variability for NIDAFL versus IDAFL, in lateral (p < 0.01) and septal (p = 0.03) right atrium, and proximal (p = 0.02) and distal (p < 0.01) coronary sinus. Spatial variability was greater in NIDAFL than IDAFL (p = 0.02).

CONCLUSIONS

Greater cycle-to-cycle atrial wavefront variability separates NIDAFL from IDAFL and is detectable from the ECG using temporospatial analyses. These results have implications for guiding ablation and support the concept that IDAFL and NIDAFL lie along a spectrum of intracardiac organization.

Correlation of atrial electrocardiographic amplitude with radiofrequency energy required to ablate cavotricuspid isthmus-dependent atrial flutter

OBJECTIVES

The purpose of this study was to evaluate a possible correlation between atrial ECG amplitude in common atrial flutter (AFL) and radiofrequency (RF) energy required to achieve cavotricuspid isthmus block.

BACKGROUND

The amount of RF delivery required for ablation of typical AFL is variable. This variation has been attributed to the cavotricuspid isthmus anatomy. Atrial ECG amplitude can be a marker of atrial anatomic variations and therefore may correlate with RF duration required to achieve cavotricuspid isthmus block.

METHODS

Seventy consecutive patients were prospectively studied. Ablation of the cavotricuspid isthmus was performed by creating a line of block between the inferior tricuspid annulus and the inferior caval vein using 8-mm-tip electrode catheters. If more than 20 minutes of RF time was required to achieve conduction block, the catheter was changed to an irrigated-tip catheter. Atrial ECG amplitude was assessed in leads II, III, aVF, and aVL.

RESULTS

A total of 14 +/- 11 minutes of RF energy was delivered to achieve block in all patients; 12 patients (8%) required more than 20 minutes. Atrial ECG amplitude showed highly significant correlations with cumulative RF energy (F and P waves in lead II: r = 0.703 and r = 0.737, P < .001). P-wave amplitude <0.2 mV and/or flutter wave amplitude <0.35 mV in lead II have a high negative predictive value to predict <20 min RF delivery (96% and 89% respectively).

CONCLUSIONS

A significant correlation exists between atrial ECG amplitude and amount of RF required to ablate typical AFL. Atrial ECG amplitude may be a surrogate marker of characteristics of isthmus anatomy. These findings may influence the choice of catheter used for cavotricuspid isthmus ablation.

Relationship Between Anatomic Location of the Crista Terminalis and Double Potentials Recorded During Atrial Flutter:

INTRODUCTION

The activation sequence in typical atrial flutter (AFL) around the tricuspid annulus is well described. However, activation of the remainder of the right atrium (RA) is not well defined. Previous studies have shown a linear block at the crista terminalis (CT) during AFL. The aim of this study was to evaluate the relationship between the location of the CT and the line of block by intracardiac echocardiography (ICE).

METHODS AND RESULTS

Twenty-one patients with typical AFL were included in the study. The ICE imaging catheter (9-French with 9-MHz ultrasound transducer) was advanced to the RA. Under ICE guidance, a 20-pole roving catheter was used to map double potentials (DPs) during AFL, and three-dimensional images of the RA were reconstructed. During counterclockwise (CCW), clockwise (CW) AFL, or both, a line of conduction block manifested by DPs was identified at a septal site adjacent to the CT in 12 patients and in the posteroseptal RA in 9 patients.

CONCLUSION

The functional line of block in CCW and CW AFL is localized not at the CT but at the septal edge of the CT or in the posteroseptal RA.

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.

Importance of ablating all potential right atrial flutter circuits in postcardiac surgery patients

OBJECTIVES

In patients with atrial flutter (AFL) and postoperative right atrial incisional scars, we sought to assess if the use of additional ablative lesions that targeted all potential re-entrant circuits, regardless of the presenting type of flutter, would prevent long-term recurrence.

BACKGROUND

Patients with AFL and incisional scars have a complex atrial substrate that may promote multiple mechanisms of intra-atrial re-entry.

METHODS

Twenty-nine patients with single right atrial incisional scars undergoing ablation for scar-dependent (n = 15) and cavotricuspid isthmus (CTI)-dependent (n = 14) flutter were studied.

RESULTS

In the scar-dependent group, 9 of 15 (60%) patients had inducible or spontaneous CTI-dependent flutter immediately after ablation. In the group with CTI flutter, 7 of 14 (50%) patients had scar-related flutter immediately after ablation. If a second type of flutter was found during the initial ablation, a second ablation was performed either along the isthmus (scar-dependent group) or from the scar to another anatomic boundary (isthmus-dependent group). Patients were followed for 24 +/- 5 months and 18 +/- 6 months in the scar- and CTI-dependent groups, respectively. In the scar-dependent group, five of six (83%) who underwent only a single flutter line had recurrence at 3 +/- 1 months. In the isthmus-dependent group, three of seven (42%) patients who had only one flutter line performed had recurrence at 5 +/- 3 months. There was no flutter recurrence in patients who initially received two different flutter lines or in patients who subsequently underwent a second flutter line at follow-up.

CONCLUSIONS

In patients with postoperative right atrial incisional scar and flutter, multiple ablation lines that target both scar-related and classic isthmuses appear necessary to prevent long-term recurrence.

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.

Atrial flutter vector loops derived from the surface ECG: does the plane of the loop correspond anatomically to the macroreentrant circuit?

We hypothesized that if the right atrial circuit during isthmus dependent atrial flutter provides the dominant contribution to the surface electrocardiogram (ECG), the three-dimensional vector loop of the flutter waves would primarily be in a plane approximately parallel to the tricuspid ring. Twenty vectorcardiograms of isthmus dependent atrial flutter derived from 12-lead ECGs of 19 patients recorded prior to radiofrequency ablation were analyzed. The plane of each loop, described by azimuth and elevation angles relative to the frontal plane, was estimated with two methods: 1) plane of maximum loop area and 2) plane of best fit. The plane of maximum loop of the loops had mean azimuth of -58 +/- 37 degrees. and elevation of 15 +/- 15 degrees. The plane of best fit of the loops had mean azimuth of -50 +/- 46 degrees and elevation of 15 +/- 14 degrees. Thus, clinical implications include the potential to predict atrial flutter mechanisms prior to intracardiac mapping.

Surface electrocardiographic characteristics of right and left atrial flutter

BACKGROUND

There is little information about the surface expression of non-cavotricuspid isthmus (CTI)-dependent right atrial (RA) or left atrial (LA) flutter circuits.

METHODS AND RESULTS

We retrospectively evaluated 32 episodes (in 26 patients) of atypical RA and 22 episodes (in 21 patients) of LA flutter. The surface ECG of 13 patients with lower-loop reentry was similar to that of their pattern during counterclockwise (CCW) CTI atrial flutter (AFL), except for decreased amplitude of the terminal forces in the inferior leads. In 11 of 24 episodes characterized by high or multiple breaks over the crista, the ECG showed changes that depended on the initial activation sequence of the LA. In 7 of 8 episodes of upper-loop reentry, the ECG pattern completely mimicked that for clockwise (CW) CTI AFL. All 11 patients with an LA septal circuit showed a typical ECG pattern characterized by prominent forces in lead V1 with flat deflections in the other surface leads. Eleven patients with other LA circuits had a more variable pattern but showed decreased voltage in the inferior leads compared with that of a group with CCW-CTI AFL (1.6+/-1 vs 2.68+/-0.7 mV, respectively; P<0.05).

CONCLUSIONS

The RA surface-ECG patterns different from those of CCW or CW-CTI could still be CTI dependent. In contrast, a typical CW-CTI surface pattern was always seen in patients with upper-loop reentry, which was non-CTI dependent. LA AFL circuits had either flat or low-amplitude forces in the inferior leads.

Electrocardiographic and electrophysiological characteristics of atrial fibrillation organized into atrial flutter by oral administration of class I antiarrhythmic agents

The aim of this study was to evaluate the electrocardiographic (ECG) and electrophysiological characteristics of atrial fibrillation (AF) that organized into atrial flutter during oral administration of class I antiarrhythmic agents. The former clinical study included 72 consecutive patients (58 paroxysmal AF, 14 persistent AF) in whom class I antiarrhythmic agents were orally administered in the outpatient clinic for termination or prophylaxis of AF. The clinical background and ECG variables were compared between the patients with and without atrial flutter during class I antiarrhythmic agents therapy. An electrophysiological study was performed in ten patients with paroxysmal AF (five with [group A] and five without atrial flutter [group B] during oral class I antiarrhythmic agents therapy. Local electrograms from five different atrial sites (high and low right free wall, high and low septum, and distal coronary sinus) were analyzed during induced AF. The activation pattern of the right free wall during AF was also analyzed using a Halo catheter. Atrial flutter was documented during class I antiarrhythmic agents therapy in 14 (24%) patients with paroxysmal AF, whereas in none with persistent AF. The mean cycle length (f-f interval) and amplitude of the fibrillation waves in leads II and V1 from the surface ECG were significantly greater in the patients with than in those without atrial flutter. In the electrophysiological study, the mean cycle lengths for the low and high right free wall were significantly longer in group A than in group B, whereas those for the low septums and distal coronary sinus did not differ between the two groups. During the induced AF, the ratio of time exhibiting a consistent activation pattern (cranio-caudal, caudo-cranial, or undetermined) along the right free wall was significantly greater in group A than in group B. Atrial flutter newly developed during class I antiarrhythmic agents therapy in patients with coarse AF on the surface ECG and a relatively organized activation in the right atrial free wall. The observation of these findings may facilitate the identification of candidates for hybrid pharmacologic and ablative therapies.

Relationship between polarity of the flutter wave in the surface ECG and endocardial atrial activation sequence in patients with typical counterclockwise and clockwise atrial flutter

BACKGROUND

The relation between ECG and activation patterns within atria in typical atrial flutter (AFL) patients (pts) has not been defined due to the lack of simultaneous multisite right and left atrial mapping.

METHODS

In 13 pts with AFL, a Halo catheter was positioned along tricuspid annulus and multipolar catheters were placed in right atrial appendage, His bundle region, coronary sinus (CS), proximal portion of right pulmonary artery (Bachmann's bundle region, BB) and esophagus (Eso) to record right and left atrial activation simultaneously.

RESULTS

In counterclockwise (CCW) AFL (11 pts), 9 showed negative flutter wave (F) and 2 positive F in the inferior leads. CCW/negative F; CS electrograms (EGs) were proximal to distal, Eso EGs were inferior to superior and BB activation was later than CS and Eso. positive F; BB activation was earlier than CS. Eso EGs were superior to inferior or simultaneous. In clockwise (CW) AFL (7 pts), 5 showed positive F and 2 negative F. CW/positive F; BB activation preceded Eso and CS. Eso EGs were superior to inferior. CS EGs were proximal to distal (1), middle to proximal, distal (3) or proximal, distal to middle (1). negative F; CS EGs were proximal to distal. CS activation was earlier than BB or CS and BB activation were simultaneous. Eso EGs were inferior to superior.

CONCLUSION

Impulse conduction to the left atrial free wall through either lower or upper interatrial connection is a major determinant of ECG morphology in AFL.