Electrophysiologic characteristics and radiofrequency catheter ablation in patients with clockwise atrial flutter

Differences between typical and reverse typical atrial flutter identified by ultrahigh resolution mapping

BACKGROUND

Although atrial flutter (AFL) is a common arrhythmia that is based on a macro-reentrant tachycardia around the tricuspid annulus, the factors giving rise to typical AFL (t-AFL) versus reverse typical AFL (rt-AFL) are unknown. To investigate the difference between t-AFL and rt-AFL circuits using ultrahigh resolution mapping of the right atrium.

METHODS

We investigated 30 isthmus-dependent AFL patients (mean age 71, 28 male) who underwent first-time cavo-tricuspid isthmus (CTI) ablation guided by Boston Scientific's Rhythmia mapping system and divided them into two groups: t-AFL (22 patients) and rt-AFL (8 patients). We compared the anatomy and electrophysiology of their reentrant circuits.

RESULTS

Baseline patient characteristics, use of antiarrhythmic drugs, prevalence of atrial fibrillation, AFL cycle length (227.1 ± 21.4 vs. 245.5 ± 36.0 ms, p = .10), and CTI length (31.9 ± 8.3 vs. 31.1 ± 5.2 mm, p = .80) did not differ between the two groups. Functional block was observed at the crista terminalis in 16 patients and at the sinus venosus in 11. No functional block was observed in three patients, all of whom belonged to the rt-AFL group. That is, functional block was observed in 100% of the t-AFL group as opposed to 5/8 (62.5%) of the rt-AFL (p < .05). Slow conduction zones were frequently observed at the intra-atrial septum in the t-AFL group and at the CTI in the rt-AFL group.

CONCLUSION

Mapping with ultrahigh-resolution mapping showed differences between t-AFL and rt-AFL in conduction properties in the right atrium and around the tricuspid valve, which suggested directional mechanisms.

[Atrial Flutter: up-to-date Problem Evaluation with Clinical Positions]

The review provides current ideas about the etiology and prevalence of atrial flutter (AF), mechanism and substrate of arrhythmogenesis, and principles of clinical and electrophysiological classification of this arrhythmia. Methods for conservative and surgical treatments of AF, including their comparative aspect, are described in detail. The review presented recent data on efficacy and potential risks of different approaches to reversing the arrhythmia. The authors indicated a need for early diagnosis and strict control of the sinus rhythm in AF, which would help a successful intervention not only to completely cure the existing arrhythmia but also to prevent other heart rhythm disorders, primarily atrial fibrillation.

Diagnosis and management of typical atrial flutter

Typical atrial flutter (AFL) is a common atrial arrhythmia that may cause significant symptoms and serious adverse effects including embolic stroke, myocardial ischemia and infarction, and rarely a tachycardia-induced cardiomyopathy as a result of rapid atrioventricular conduction. As a result of the well-defined anatomic and electrophysiological substrate, and the relative pharmacologic resistance of typical AFL, radiofrequency catheter ablation has emerged in the past decade as a safe and effective first-line treatment. This article reviews the electrophysiology of typical AFL and the techniques currently used for its diagnosis and management.

Diagnosis and management of typical atrial flutter

Can "past decade" be rephrased to refer to more specific years? Typical atrial flutter (AFL) is a common atrial arrhythmia that may cause significant symptoms and serious adverse effects, including embolic stroke, myocardial ischemia and infarction, and, rarely, a tachycardia-induced cardiomyopathy resulting from rapid atrioventricular conduction. As a result of the well-defined anatomic and electrophysiologic substrate and the relative pharmacologic resistance of typical AFL, radiofrequency catheter ablation has emerged since its first description in 1992 as a safe and effective first-line treatment. This article reviews the electrophysiology of typical AFL and techniques currently used for its diagnosis and management.

Ablation of difficult right-sided accessory pathways aided by mapping of tricuspid annular activation using a Halo catheter : Halo-mapping of right sided accessory pathways

OBJECTIVE

To demonstrate that the use of a 20-pole catheter (Halotrade mark) positioned around the tricuspid valve annulus (TVA) is helpful in rapidly localising right free wall accessory pathways (AP), enhancing catheter stability during ablation, and leading to increased success in ablating these challenging pathways.

PATIENTS AND METHODS

Seven consecutive patients who underwent Halo-mapping of right-sided AP were studied. All but one had previously failed ablation. With a Halo catheter deployed at TVA, the accessory pathway location was rapidly identified using the sites of earliest atrial (A) activation during ventricular (V) pacing or orthodromic tachycardia, or earliest V-activation during sinus rhythm or A-pacing were identified. The stability of the ablation catheter was guided fluoroscopically (with reference to the stationary Halo), and electrically (contact artefact between the ablation catheter and Halo poles).

RESULTS

AP locations were identified by the Halo (anterior in one patient, antero-lateral in one, lateral in two, and postero-lateral in three) where similar local VA/AV intervals were recorded at both the ablation catheter and Halo bipoles recording the shortest VA/AV intervals (four of seven patients), contact artefact between the ablation catheter and those Halo bipoles was seen (six of seven patients), or both (three of seven patients). All APs were ablated successfully after a mean RF duration of 5+/-2 min, and 25+/-17 min post Halo deployment without clinical recurrence at 12+/-4 months follow-up.

CONCLUSION

A Halo positioned at the TVA can ease the localisation of right-sided AP, facilitate catheter stability during ablation, and guides successful ablation.

A new electrocardiographic algorithm to differentiate upper loop re-entry from reverse typical atrial flutter

OBJECTIVES

This study was performed to differentiate upper loop re-entry (ULR) from reverse typical atrial flutter (AFL).

BACKGROUND

Right atrial ULR and reverse typical AFL have different mechanisms and ablation strategies, but similar electrocardiographic characteristics.

METHODS

This study included 26 patients with reverse typical AFL and 20 patients with ULR. The noncontact mapping system (EnSite-3000, Endocardial Solutions, St. Paul, Minnesota) was used to confirm diagnosis and guide successful radiofrequency ablation. Flutter wave polarity and amplitude in the 12-lead surface electrocardiogram were determined by two independent electrophysiologists.

RESULTS

The flutter wave polarity in leads I and aVL was significantly different between the reverse typical AFL and ULR groups (p < or = 0.001). Voltage measurement revealed significant differences between reverse typical AFL and ULR in leads I, II, aVR, aVF, V1, and V2 (p < 0.001). A new diagnostic algorithm based on negative or isoelectric/flat flutter wave polarity and amplitude < or =0.07 mV in lead I was useful for diagnosis of ULR, with an accuracy of 90% to 97%, a sensitivity of 82% to 100%, and a specificity of 95%.

CONCLUSIONS

Polarity and voltage measurement of flutter wave in lead I can differentiate reverse typical AFL from ULR.

Catheter ablation of atrial flutter and macroreentrant atrial tachycardia

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

Different patterns of interatrial conduction in clockwise and counterclockwise atrial flutter

BACKGROUND

The terms counterclockwise (CC) and clockwise (C) atrial flutter (Afl) are used to describe right atrial activation around the tricuspid valve in the left anterior oblique view. The manner in which the left atrium is activated, as reflected by coronary sinus (CS) recordings, has not been systematically evaluated.

METHODS AND RESULTS

Nine patients with both CC and C Afl underwent electrophysiological study with CS recordings during both rhythms with the use of a decapolar catheter with the tip placed in the distal CS. Patterns of CS activation during each type of Afl as well as during during sinus rhythm were categorized into 1 of 3 patterns: sequential proximal-to-distal, sequential distal-to-proximal, and fused, indicating activation from different directions. In 7 of 9 patients, the pattern of CS activation in CC Afl and C Afl differed, with a proximal-to-distal pattern in CC Afl and a fused pattern in C Afl. In 2 patients, pacing the high right atrial septum near the presumed site of Bachmann's bundle in sinus rhythm showed a similar fused pattern of CS activation.

CONCLUSIONS

These results demonstrate different patterns of CS activation in CC Afl and C Afl in the majority of patients and are consistent with a model in which the left atrium is activated predominantly over Bachmann's bundle during C Afl and over the CS os in CC Afl. These findings may have implications for maintenance of Afl, interpretation of flutter wave morphology on surface ECG, and left atrial mechanical function in Afl.

Management of atrial flutter

Atrial flutter is a macroreentrant arrhythmia that is associated with cardiovascular and pulmonary disease. In the United States, 200,000 new cases of atrial flutter can be expected to develop every year with a male to female ratio of over 2:1. This arrhythmia is associated with atrial fibrillation in over half the cases. It is also associated with an increased risk of thromboembolic complications, but less than that is seen with atrial fibrillation. The most common form of atrial flutter involves a large reentrant circuit within the right atrium, encircling the tricuspid annulus. Other, less common forms of atrial flutter may involve other anatomic barriers, atriotomy scars, and infarcted areas of the atria. Treatment of atrial flutter often involves electrical cardioversion and/or antiarrhythmic medications. Type I and Type III antiarrhythmic drugs are often used to terminate or prevent recurrent episodes and Type II (beta-blockers) and Type IV (calcium channel blockers) can be used to control the ventricular rate during atrial flutter. However, antiarrhythmic drugs alone control atrial flutter in only 50% to 60% of patients. Since the early 1990s, radiofrequency catheter ablation has been used to interrupt the reentrant circuit and prevent recurrences of atrial flutter. Radiofrequency ablation is acutely successful in over 90% of cases and avoids the long-term toxicity seen with antiarrhythmic drugs. Advanced mapping techniques and newer methods of delivering the radiofrequency lesions are being used to delineate unusual forms of atrial flutter and to minimize fluoroscopic exposure during the procedure.

Complications associated with radiofrequency catheter ablation of cardiac arrhythmias

Catheter ablation using radiofrequency energy has evolved as a safe and effective means for the treatment of various supraventricular and ventricular arrhythmias. Despite the overall efficacy of radiofrequency catheter ablation, cardiovascular complications can occur in a small number of patients. The purpose of this article is to review the current understanding of the risks and complications that can occur during catheter ablation procedures.

Catheter ablation for cardiac arrhythmias

The safety and efficacy of catheter ablation for treatment of most types of cardiac arrhythmias are well established. These arrhythmias and arrhythmia substrates include AVNRT, accessory pathways, focal atrial tachycardia, atrial flutter, idiopathic ventricular tachycardia, and bundle-branch re-entry. Catheter ablation is considered as an alternative to pharmacologic therapy in the treatment of these cardiac arrhythmias.

[Characteristics of atrial electrograms recorded in radiofrequency induced block lines in an experimental model]

AIM

To analyze and quantify atrial electrogram modifications following the induction of linear lesions in the atrial wall using radiofrequency ablation procedures.

METHODS

An epicardial multiple electrode (221 unipolar electrodes) was used in 12 Langendorff perfused rabbit hearts to analyze atrial activation before and after radiofrequency induction of a linear lesion in the left atrial wall. After confirming the existence of conduction blockade in the lesion zone by epicardial mapping and propagation vector analysis, six electrodes each were selected in the lesioned and non-lesioned zones in all experiments, comparing the amplitude, maximum negative slope and morphology of the electrograms in both zones, before (control) and after radiofrequency delivery.

RESULTS

Analysis of the reproducibility of the measurements in two consecutive cycles showed a variation of 1 +/- 5% for amplitude (NS) and 1 +/- 9% for maximum negative slope (NS). In the non-damaged zone, amplitude (105 +/- 22%) and slope (92 +/- 16%) (values normalized with respect to those recorded before radiofrequency) did not vary significantly following radiofrequency, and simple electrograms were the most frequent recordings (82 vs 83% in control; NS). Amplitude (19 +/- 7%, p < 0.001) and slope (24 +/- 11%; p < 0.001) decreased significantly in the lesion zone, as did the percentage of simple electrograms (6 vs 86% in control; p < 0,001). In this same zone the morphology could not be determined in 12% of the recordings, while multiple electrograms were obtained in 15% (vs 2% in control; p < 0.01), and the most frequent type corresponded to double electrograms (67 vs 12% in control, p < 0.001), with both components coinciding in time with atrial activation in the zones proximal and distal to the lesion line.

CONCLUSIONS

Electrograms recorded directly in radiofrequency induce block lines show a significant decrease in amplitude and maximum negative slope. Double electrograms predominate in these recordings, both components of which represent activation on either side of the lesion. In a small proportion of cases simple and multiple electrograms can also be recorded in the block line.

Right atrial angiographic evaluation of the posterior isthmus: relevance for ablation of typical atrial flutter

BACKGROUND

Gaining anatomic information about the posterior isthmus is not generally part of flutter ablation procedures. We postulated that right atrial (RA) angiography could rationalize the ablation approach by revealing the conformation of the isthmus.

METHODS AND RESULTS

In 100 consecutive patients, biplane RA angiography was performed before ablation to guide catheter contact with the isthmus along its length. Angiography showed a wide variation in the width of the isthmus (17 to 54 mm; 31.3+/-7.9), its angle with the inferior vena cava in the right anterior oblique projection (68 degrees to 114 degrees; 90.3+/-9.0 degrees ), and its lateral position relative to the inferior vena cava in the left anterior oblique projection. A deep sub-Eustachian recess was revealed in 47%, with a mean depth of 4.3+/-2.1 mm (1.5 to 9.4). A Eustachian valve was visualized in 24%. Ablation resulted in bidirectional conduction block (which could be transient) in all, with a median of 2 dragging radiofrequency (RF) applications (2.3+/-2.5 RF applications; 57 degrees C, < or =99 seconds each). Permanent block was achieved in 99%, with a median of 3 RF applications (3.4+/-3.0). The presence of a Eustachian valve or concave isthmus was associated with statistically more RF applications; the same trend was seen for patients with deep pouches. The number of RF applications decreased statistically throughout the study, indicating a learning curve. No patient had a recurrence after a follow-up of 13+/-11 months.

CONCLUSIONS

Right atrial angiography reveals a highly variable isthmus anatomy, often showing particular configurations that can make ablation more laborious. Rational adaptation of the ablation approach to these anatomic findings may contribute to successful ablation.

Electrophysiologic characteristics and ablation of an atypical atrial flutter in the right atrium

Subeustachian isthmus-dependent typical atrial flutter has been well studied. We demonstrate a case with atypical atrial flutter involving only the base of the right atrium around the inferior vena cava. Entrainment pacing and mapping studies documented a distinct circuit traversing the subeustachian isthmus, propagating through the posterobasal right atrium, and skirting the inferior vena cava. Successful radiofrequency ablation of the arrhythmia was accomplished by creating a linear lesion at the subeustachian isthmus. Mapping of the inferior vena cava region and the demonstration of concealed entrainment are essential steps in establishing the mechanism of the atypical atrial flutter.

Predictors of success in radiofrequency catheter ablation of atrial flutter

Radiofrequency catheter ablation of typical atrial flutter at the isthmus between the tricuspid annulus and the inferior vena cava is established. However in selected patients, the creation of a continuous linear lesion at the targeted isthmus requires a lengthened procedure or is not feasible at all and atrial flutter recurrences are common. In a retrospective analysis, we found that an intraoperatively determined distance between the tricuspid annulus and the inferior vena cava of <.2.5 cm is an independent predictor of a lengthened or failed ablation procedure. Additional equipment, e.g., long introducer sheaths, adapted ablation catheter design, or irrigated tip ablation, as well as alternative ablation approaches, e.g., linear lesions between the tricuspid annulus and Eustachian ridge, have been invented in order to increase the acute success rate or decrease fluoroscopy and procedure time. In a prospective study on the effects of various conduction properties at the isthmus between tricuspid annulus and inferior vena cava following radiofrequency ablation of atrial flutter, we showed previously that others than a complete bidirectional conduction block predicts a high recurrence rate of atrial flutter. For determination of transisthmal conduction properties following ablation, established mapping approaches are documentation of double potentials at the ablation line and right atrial activation sequence following posteroseptal and low lateral right atrial pacing. Novel threedimensional mapping systems, i.e., Carto(R) and EnSite(R), may further enhance the accuracy of conventional mapping techniques.

[Radiofrequency ablation as the first line of treatment in patients with common atrial flutter. The arguments con]

After years of development, radiofrequency ablation of common flutter circuits is a well established procedure. Once the structure of the circuit, and its critical isthmus, were defined, effective approaches to ablation have been developed, improving initial results. The problem of recurrence has been largely controlled, and the present recurrence rate is 10-15%. The large majority of recurrences can be treated successfully by a new ablation, with a very low incidence of second recurrence. Nevertheless, isthmus ablation is not a curative procedure, because it does not address the cause of flutter, only a necessary link in the circuit. The electrophysiologic and/or anatomic abnormalities of the atrium or atria persist after ablation. Perhaps for this reason there is an incidence of atrial fibrillation in 25-30% of cases after successful flutter ablation. On the other hand, some clinical data suggest that a first episode of flutter has a low incidence of recurrence after cardioversion. For all these reasons flutter ablation should not be considered as first line treatment in all episodes of atrial flutter, but of those with recurrences and/or poor tolerance.

Reduction of atrial fibrillation inducibility by radiofrequency ablation: an experimental study

A study is made of the antifibrillatory effects of radiofrequency (RF)-induced atrial lesions using nine Langendorff-perfused rabbit hearts in which the atrial electrophysiological properties and atrial fibrillation (AF) inducibility were modified by atrial stretching. Using a multiple electrode consisting of 121 unipolar electrodes, determinations were made of the atrial refractory periods, conduction velocity, wavelength of the atrial activation process, and the inducibility of sustained AF episodes (duration over 30 s) by atrial burst pacing in four situations: (a) control; (b) following dilatation of the right atrium; (c) after adding an RF linear lesion at the cava-tricuspid annulus isthmus; and (d) after adding two RF linear lesions rounding the base of the right atrial appendage and extending from the inferior zone of the sulcus terminalis to the anterior wall of the appendage. Under control conditions, AF was not induced in any of the experiments. The wavelengths were 10.5 +/- 1.2 cm for basic cycles of 250 ms and 6.6 +/- 0.5 cm for cycles of 100 ms. Following dilatation, a significant decrease was recorded in the atrial refractory periods, conduction velocity, and wavelength, which reached values of 6.1 +/- 0.7 cm (250-ms cycle, P < 0.01), and 3.9 +/- 0.3 cm (100-ms cycle, P < 0.01); AF was induced in five cases (P < 0.05). After producing the lesion at the cava-tricuspid isthmus, the electrophysiological modifications induced by atrial dilatation persisted (wavelength = 6.2 +/- 0.6 cm (250-ms cycle) and 4.3 +/- 0.3 cm (100-ms cycle); P < 0.01 vs the control) and AF was triggered in eight cases (P < 0.0001). In turn, on adding the two lesions at the right atrial free wall and appendage, AF was induced only in one experiment (P = NS vs control), and the dilatation-induced decrease in refractoriness and wavelength was attenuated. Nevertheless, differences remained significant with respect to the controls, with the exception of the functional refractory periods determined at cycles of 100 ms. In this phase, the wavelength was 6.6 +/- 0.7 cm (250-ms cycle, P < 0.01 vs control) and 4.9 +/- 0.5 cm (100-ms cycle; P < 0.05). Atrial conduction between the zones separated by the lesions was blocked at any frequency, or selectively at rapid atrial activation frequencies.

IN CONCLUSION

(a) the production of three linear lesions in the right atrium (cava-tricuspid isthmus, atrial appendage, and inferior free wall) reduces AF inducibility in the experimental model used; (b) conduction block (either absolute or frequency dependent) through the lesions, reduction in tissue mass caused by lesion creation, and possibly the attenuation of the shortening of atrial refractoriness and wavelength in the zones not separated by the lesions are implicated in the reduction of AF inducibility; and (c) the single lesion in the cava-tricuspid isthmus does not impede AF inducibility.

Radiofrequency ablation of atrial flutter due to administration of class IC antiarrhythmic drugs for atrial fibrillation

In selected patients, atrial fibrillation (AF) converts to atrial flutter (AFI) due to treatment with class IC antiarrhythmic drugs. In this study, we prospectively investigated the effects of AFI ablation and continuation of drug therapy in patients with AF who developed AFI due to long-term administration of class IC antiarrhythmic drugs. The study population consisted of 187 patients from an AF registry with paroxysmal AF who were orally treated with flecainide (n = 96) or propafenone (n = 91). Twenty-four patients (12.8%) developed AFI during the course of treatment. In 20 of these patients (10.7%), electrophysiologic study revealed typical AFI. These patients underwent radiofrequency ablation of AFI. Ablation failed in 1 patient. All patients continued preexisting drug treatment. Recurrence of AF was assessed by ambulatory Holter monitoring and serial questionnaires. During a mean follow-up of 11 +/- 4 months, the incidence of AF episodes was significantly lower in patients with a combined therapy (2.7 +/- 3.6 per year) than in control subjects with a sole drug treatment (7.8 +/- 9.2 per year, p <0.05) and than before therapy (10.2 +/- 5.4 per year, p <0.001). Subgroup analysis revealed that 7 patients (36.8%) remained symptom free with no evidence of atrial tachyarrhythmia. Eight additional patients (42.1%) had ongoing paroxysmal AF, however, with a significantly lower incidence of AF episodes than before therapy (2.3 +/- 1.6 per year vs 11.5 +/- 5.0 per year, p <0.001). In the remaining 4 patients (14.7%), no beneficial effect of AFI ablation was found. It is concluded that in patients with AF who develop typical AFI due to administration of class IC antiarrhythmic agents, a combined therapy with catheter ablation of AFI and continuation of drug treatment is highly effective in reducing occurrence and duration of atrial tachyarrhythmias.

[The ablation of atrial flutter. The long-term results after 8 years of experience]

OBJECTIVE

Since the 1990's radiofrequency ablation radiofrequency ablation of atrial flutter has evolved in its methods and results. We have reviewed the long term outcome in 62 patients with typical (common) or reversed (clockwise) flutter undergoing radiofrequency ablation between 1990 and 1997.

PATIENTS AND METHODS

Fifty men and 12 women, aged 22-78 years (57 +/- 12) with flutter recurring after cardioversion and antiarrhythmic drugs make this series. Flutter was typical in 59 cases and reversed in 3. There was no heart disease in 14, bronchopulmonary disease in 10, coronary disease in 9, cardiomyopathies in 6 and other processes in the remainder. In 5 cases with previous surgery for atrial or ventricular septal defect, Ebstein's anomaly or myxoma, we treated also a macro-reentry tachycardia around the atriotomy in the right atrium. Radiofrequency ablation was directed to the inferior vena cava-tricuspid isthmus in typical and reversed flutter, and to the isthmus between the inferior end of the atriotomy and the inferior vena cava, in the lateral right atrium, in the atriotomy tachycardias. We subdivided our patients in Group 1 (24 patients), treated until the end of 1994, and Group 2 (38 patients) treated since 1995 using specially designed catheters and trying to produce isthmus block as the endpoint of the procedure.

RESULTS

Radiofrequency ablation interrupted flutter in 61 of 62 cases (98.4%), and the atriotomy tachycardia in all 5. The number of application in Group 1 was 18.6 +/- 10.1 vs 12 +/- 10 in Group 2 (p < 0.05). Follow-up was 40 +/- 24 months in Group 1 vs 16 +/- 9.5 in Group 2. Flutter recurred in 58% of Group 1 and 13% of Group 2 patients (p < 0.001), usually 1-3 months after radiofrequency ablation and they were successfully treated by new radiofrequency ablation with a small number of applications. There was no recurrence of atriotomy tachycardia. Atrial fibrillation occurred in 14 patients (23%) (11 paroxysmal, 3 persistent), with equal incidence in both groups. At the end of follow-up 85% of the patients were in sinus rhythm, although 6 needed pacemakers for sinus node dysfunction (3) or AV ablation (3). Antiarrhythmic drugs were used by 46% of patients in Group 1 and 26% in Group 2 (p = NS) for atrial arrhythmias or recurrent flutter.

CONCLUSIONS

Radiofrequency ablation is an effective treatment for flutter and macro-reentry atriotomy tachycardia. Progress in methods have improved results significantly. Atrial fibrillation can still be a problem in 20-25% of the patients after flutter control.

New electrocardiographic criteria for the differentiation between counterclockwise and clockwise atrial flutter: correlation with electrophysiological study and radiofrequency catheter ablation

OBJECTIVE

To develop new electrocardiographic (ECG) criteria for the differentiation between counterclockwise and clockwise atrial flutters.

BACKGROUND

Traditionally, the ECG differentiation between counterclockwise and clockwise atrial flutters is based on the flutter wave polarity in the inferior leads. However, determination of flutter wave polarity is subjective and sometimes difficult, especially in flutter waves of undulating pattern.

PATIENTS

The study comprised 37 consecutive patients with drug resistant atrial flutter; 30 had counterclockwise and 17 had clockwise atrial flutter (10 had both forms of atrial flutter). The isthmus dependence was confirmed by entrainment study and catheter ablation. The ECG patterns of both types of atrial flutter were compared and the flutter wave polarity in the inferior leads was determined by four independent cardiologists.

RESULTS

The flutter wave polarity in the inferior leads appeared negative in 24, positive in one, and equivocal in five of the counterclockwise atrial flutters; polarity appeared negative in one, positive in 10, and equivocal in six of the clockwise atrial flutters. However, the aVF/lead I flutter wave amplitude ratio was > 2.5 in all counterclockwise but < 2.5 in all clockwise atrial flutters. The flutter wave nadirs in the inferior leads corresponded to the upstrokes in V1 in all counterclockwise atrial flutters, but corresponded to the downstrokes in V1 in all clockwise atrial flutters.

CONCLUSIONS

The flutter wave polarity in the inferior leads does not correlate well with the flutter wave rotating direction. However, counterclockwise and clockwise atrial flutters can be differentiated by new ECG criteria with high accuracy.

Electropharmacologic effects of class I and class III antiarrhythmia drugs on typical atrial flutter: insights into the mechanism of termination

BACKGROUND

Acute effects of class I and class III antiarrhythmia drugs on the reentrant circuit of typical atrial flutter are not fully studied. Furthermore, the critical electrophysiologic determinants of flutter termination by antiarrhythmia drugs are not clear.

METHODS AND RESULTS

The study population consisted of 36 patients (mean age, 53+/-17 years) with clinically documented typical atrial flutter. A 20-pole "halo" catheter was positioned around the tricuspid annulus. Incremental pacing was performed to measure the conduction velocity along the isthmus and lateral wall, and extrastimulation was performed to evaluate atrial refractory period in the baseline state and after intravenous infusion of ibutilide, propafenone, and amiodarone. Efficacy of these drugs in conversion of typical atrial flutter and patterns of termination were also determined. Ibutilide significantly increased the atrial refractory period and decreased conduction velocity in the isthmus at short pacing cycle length. It terminated atrial flutter in 8 (67%) of 12 patients after prolongation of flutter cycle length due to increase (86+/-19%) of conduction time in the isthmus. Propafenone predominantly decreased conduction velocity with use dependency and significantly increased atrial refractory period, but it only converted atrial flutter in 4 (33%) of 12 patients. Amiodarone had fewer effects on atrial refractory period and conduction velocity than did ibutilide and propafenone, and it terminated atrial flutter in only 4 (33%) of 12 patients. Termination of typical atrial flutter was due to failure of wave front propagation through the isthmus, which occurred with cycle length oscillation, abruptly without variability of cycle length, or after premature activation of the reentrant circuit.

CONCLUSIONS

Ibutilide, with a unique increase in atrial refractoriness, was more effective in conversion of atrial flutter than were propafenone and amiodarone.

Intracardiac stimulation of human parasympathetic nerve fibers induces negative dromotropic effects: implication with the lesions of radiofrequency catheter ablation

INTRODUCTION

The dromotropic effects of intracardiac parasympathetic nerve stimulation have not been well studied; furthermore, the effects of radiofrequency ablation lesions on parasympathetic nerve stimulation are not clear.

METHODS AND RESULTS

Group I: intracardiac electrical stimulation in the right posteroseptal and anteroseptal areas under different stimulation strengths; group II: intracardiac electrical stimulation before and 10 minutes after intravenous propranolol; group III: intracardiac electrical stimulation before and 5 minutes after intravenous atropine. Among the 10 patients with AV nodal reentrant tachycardia (group IV) and the 10 patients with atrial flutter (group V), atrial fibrillation was induced before and after successful ablation, and intracardiac electrical stimulation in the right posteroseptal area was performed before and after successful ablation. The maximal response and complete decay of the response occurred within 2 to 6 seconds of initiation or termination of parasympathetic nerve stimulation. This negative dromotropic effect disappeared after atropine was administered, but not after propranolol. After successful ablation, parasympathetic stimulation still induced negative dromotropic effects.

CONCLUSION

Electrical stimulation of parasympathetic nerve fibers near the posteroseptal and anteroseptal areas could induce a negative dromotropic effect, and this effect was preserved after successful radiofrequency ablation of slow pathway and isthmus conduction.

Role of autonomic tone in facilitating spontaneous onset of typical atrial flutter

OBJECTIVES

This study sought to study the change in autonomic tone that precedes the initiation of paroxysmal atrial flutter.

BACKGROUND

An abrupt change in the autonomic tone of the heart is an important initiating factor in the pathogenesis of ventricular tachyarrhythmias and paroxysmal atrial fibrillation. Whether the autonomic tone has a role in the initiation of paroxysmal atrial flutter has not been reported.

METHODS

Holter electrocardiographic recording was used to investigate the changes in heart rate variability before the onset of paroxysmal atrial flutter.

RESULTS

A total of 12 patients with paroxysmal atrial flutter were analyzed. An increase in the normalized value of the low frequency (LF) component and the LF/high frequency (HF) ratio and a decrease in the normalized value of the HF component began at 6 min before the onset of episodes of paroxysmal atrial flutter, which indicated that sympathovagal balance had shifted to more sympathetic predominance.

CONCLUSIONS

An increase in sympathetic modulation or vagal withdrawal, or both, may facilitate the initiation of atrial flutter.

Long-term outcome of radiofrequency catheter ablation for typical atrial flutter: risk prediction of recurrent arrhythmias

INTRODUCTION

Little is known about the predictors of recurrent atrial flutter or fibrillation after successful radiofrequency ablation of typical atrial flutter. In addition, there is only limited evidence suggesting that elimination of atrial flutter would modify the natural history of atrial fibrillation in patients who experienced both of these arrhythmias. The aims of the present study were to investigate the long-term results of radiofrequency catheter ablation and to examine the predictors for late occurrence of atrial fibrillation in a large population with typical atrial flutter.

METHODS AND RESULTS

The study population consisted of 144 patients (mean age 56 +/- 18 years) with successful ablation of clinically documented typical atrial flutter. In the first 50 patients, successful ablation was defined as termination and noninducibility of atrial flutter; for the subsequent 94 patients, successful ablation was defined as achievement of bidirectional isthmus conduction block and no induction of atrial flutter. The clinical and echocardiographic variables were analyzed in relation to the late occurrence of atrial flutter or fibrillation. Over the follow-up period of 17 +/- 13 months, 14 (9.7%) patients had recurrence of typical atrial flutter. In the first 50 patients, 8 (16%) had recurrence of atrial flutter, compared with only 6 (6%) of the following 94 patients. Patients with incomplete isthmus block had a significantly higher incidence of recurrent atrial flutter than those with complete isthmus block (6/16 vs 0/78, P < 0.0001) in the following 94 patients. There was no predictor for recurrence of atrial flutter after successful ablation as determined by univariate and multivariate analysis. Although successful ablation of atrial flutter eliminated atrial fibrillation in 45% of patients with a prior history of atrial fibrillation, 31 (21.5%) of 144 patients undergoing this procedure developed atrial fibrillation during the follow-up period. Univariate analysis revealed that three clinical variables were related to the occurrence of atrial fibrillation: (1) the presence of structural heart disease; (2) a history of atrial fibrillation before ablation; and (3) inducible sustained atrial fibrillation after ablation. By multivariate analysis, only a history of atrial fibrillation and inducible sustained atrial fibrillation could predict the late development of atrial fibrillation after atrial flutter ablation.

CONCLUSION

Radiofrequency catheter ablation of typical atrial flutter is highly effective and associated with a low recurrence rate of atrial flutter, but atrial fibrillation continues to be a long-term risk for patients undergoing this procedure. The presence of structural heart disease and prior spontaneous or inducible sustained atrial fibrillation increases the risk of developing atrial fibrillation.

Acute and long-term effects of consecutive radiofrequency applications on conduction properties of the subeustachian isthmus in type I atrial flutter

INTRODUCTION

Bidirectional conduction block at the subeustachian isthmus predicts long-term efficacy of atrial flutter ablation. Limited data are available on the incidence and outcome of minor conduction changes such as unidirectional or incomplete block. This prospective study sought to systematically assess discrete acute and long-term alterations of bidirectional conduction prior to a complete conduction block.

METHODS AND RESULTS

In 41 patients with type I atrial flutter, pulse propagation through the subeustachian isthmus during low lateral and proximal coronary sinus pacing was documented and analyzed following each consecutive radiofrequency (RF) application. In cases of altered conduction properties and noninducibility of atrial flutter, patients were followed-up for 12 months. Three sets of results were found. First, following RF application, 23 patients presented a progressive conduction delay prior to a complete conduction block. Second, RF application did not always affect counterclockwise and clockwise conduction simultaneously or to the same extent. In 13 patients, an initial alteration of counterclockwise conduction was present before an alteration of clockwise conduction; in 5 patients, clockwise conduction was primarily affected. Third, the recurrence rate of typical atrial flutter was 9% (2/22) in patients with a complete bidirectional conduction block, 54% (7/13) in patients with unidirectional conduction block, and 100% (6/6) in patients with sole bidirectional conduction delay.

CONCLUSION

In 50% of the patients, consecutive RF applications resulted primarily in a progressive conduction delay rather than a sudden conduction block. Since counterclockwise and clockwise conduction were not always affected simultaneously or to the same extent, lateral as well as septal pacing is recommended for improvement of bidirectional conduction block. Normalization of primarily altered conduction and, therefore, recurrence of atrial flutter are high in all patients without bidirectional block.

Role of the surface electrocardiogram in the diagnosis of patients with supraventricular tachycardia

In this era of interventional electrophysiology, the accuracy of the electrocardiogram in diagnosis of supraventricular tachycardia could be improved by detailed endocardial mapping and confirmed by results of radiofrequency catheter ablation. This article describes the electrocardiographic characteristics for different types of supraventricular tachycardia: atrial fibrillation, atrial flutter, atrial tachycardia, atrioventricular reciprocating tachycardia using an accessory pathway, and atrioventricular node reentrant tachycardia. Several limitations, including the identification of P wave morphologies and polarities and separation between the terminal part of T wave and P wave during tachycardia, should be resolved before an accurate algorithm of the 12-lead surface electrocardiogram is developed for the diagnosis of supraventricular tachycardia.

Characterization of low right atrial isthmus as the slow conduction zone and pharmacological target in typical atrial flutter

BACKGROUND

Previous electrophysiological studies in patients with typical atrial flutter suggested that the slow conduction zone might be located in the low right atrial isthmus, which is a path formed by orifice of inferior vena cava, eustachian valve/ridge, coronary sinus ostium, and tricuspid annulus. The conduction characteristics during atrial pacing and responses to antiarrhythmic drugs of this anatomic isthmus were unknown.

METHODS AND RESULTS

Forty-four patients, 20 patients with paroxysmal supraventricular tachycardia (group 1) and 24 patients with clinically documented paroxysmal typical atrial flutter (group 2), were studied. A 20-pole halo catheter was situated around the tricuspid annulus. Incremental pacing from the low right atrium and coronary sinus ostium was performed to measure the conduction time and velocity along the isthmus and lateral wall in the baseline state and after intravenous infusion of procainamide or sotalol. In both groups, conduction velocity in the isthmus during incremental pacing was significantly lower than that in the lateral wall before and after infusion of antiarrhythmic drugs. Furthermore, gradual conduction delay with unidirectional block in the isthmus was relevant to initiation of typical atrial flutter. Compared with group 1, group 2 had a lower conduction velocity in the isthmus and shorter right atrial refractory period. Procainamide significantly decreased the conduction velocity, but sotalol did not change it. In contrast, sotalol significantly prolonged the atrial refractory period with a higher extent than procainamide. After infusion of procainamide, the increase of conduction time in the isthmus accounted for 52+/-19% of the increase in flutter cycle length, and 5 of 12 patients (42%) had spontaneous termination of typical flutter. After infusion of sotalol, typical flutter was induced in only 6 of 12 patients (50%) without significant prolongation of flutter cycle length.

CONCLUSIONS

The low right atrial isthmus with rate-dependent slow conduction properties is critical to initiation of typical human atrial flutter. It may be the potentially pharmacological target of antiarrhythmic drugs in the future.