Use of a Three-Dimensional, Nonfluoroscopic Mapping System for Catheter Ablation of Typical Atrial Flutter

Recent studies have shown that typical atrial flutter (AFL) results from right atrial reentry around the tricuspid annulus (TA), constrained between the TA and crista terminalis (CT) on the free-wall and the TA and eustachian ridge (ER) on the septum. Creation of a complete line of conduction block across the subeustachian isthmus, between the TA and ER, elminates AFL. The accuracy of fluoroscopy in localizing the anatomical boundaries and previous radiofrequency application sites is limited. This article describes an approach for utilizing a new three-dimensional nonfluoroscopic electroanatomical mapping system (CARTO) to examine the global right atrial activation pattern in patients during AFL, localize the anatomical boundaries, and create a complete line of conduction block by ablation across the subeustachian isthmus. During AFL, the locations of CT and ER are identified by double atrial potentials recorded along the intercaval region and between the inferior vena cava and coronary sinus ostium, respectively. Radiofrequency ablation across the subeustachian isthmus is performed during coronary sinus pacing. Beginning at TA, the ablation electrode is moved toward ER in 2–3 mm increments. Each movement is marked on the right atrial map to visualize the ablation line. In the event of residual conduction across the ablation line, defects in the ablation line are located by mapping along the previous ablation sites guided by CARTO system to locate the transition from the double atrial potentials (indicating block) to a single atrial potential (indicating conduction). Radiofrequency ablation to the site showing the single atrial potential along the ablation line produces complete conduction block across the subeustachian isthmus. In conclusion, the new electroanatomical mapping system allows precise 3-D localization of the anatomical boundaries of the AFL reentrant circuit, and facilitates ablation by accurately locating defects in the ablation line.(PACE 1998; 21:1279–1286)     

Unusual Intraatrial Reentry Following the Mustard Procedure Defined by Multisite Magnetic Electroanatomic Mapping

SARDANA, R., et al .: Unusual Intraatrial Reentry Following the Mustard Procedure Defined by Multisite Magnetic Electroanatomic Mapping. This report describes a patient with d-TGA post Mustard repair who presents with atrial arrhythmias. Two distinct intraatrial reentrant tachycardias were discovered and successful catheter ablation was performed in a unique atrial location not previously described. This case also explores the use of magnetic electroanatomic mapping in guiding catheter ablation. (PACE 2003; 26[Pt. I]:902–905)     

A Clinical Study of the Application of Endocardial Fulguration in the Treatment of Recurrent Atrial Flutter

Endocardial catheter fulguration has been recently proposed for treatment of arrhythmias originating within the right atrium. In this study the authors attempted to use this technique in eight patients with paroxysmal common atrial gutter. Numerous antiarrhythmic agents failed to prevent recurrences of the episodes, which occurred frequently over periods of at least 4 months. In every procedure, we used a 7F quadripolar catheter electrode introduced via the subclavian vein into the lower part of the right atrium. The two distal electrodes allowed the recording of bipolar double potentials where the critical slow pathway of the reentrant circuit was localized. A unipolar electrogram recording by the tip electrode gave us the location of the area to be ablated when this electrogram was in complete concordance with a small step in the descending part of the F waves in II, III and aVF. This step corresponded to the very depolarization of the reentry area. A DC shock of 100 to 120 J was delivered between the tip electrode and a paddle applied to the left chest wall. Sinus rhythm resumed instantaneously. No mechanical or electrical complications were noted. Three patients are free of relapses without antiarrhythmic drugs (follow-up: 14 to 17 months); three others are also free of relapses, but antiarrhythmic agents were required for treatment of other supraventricular dysrhythmias (follow-up: 3 to 17 months); atrial flutter recurred within several days and persisted in spite of two more procedures in two patients. We conclude that endocardial catheter fulguration of paroxysmal and recurrent atrial flutter seems to be effective therapy. Nevertheless, more experience is required in order to confirm these results.     

Magnetoelectroanatomic mapping of arrhythmias in structural heart disease using a novel multielectrode catheter:

Electroanatomic mapping with CARTO requires point-by-point acquisition using the mapping catheter's bipolar tip electrode. This study evaluates the utility of a novel 26-electrode catheter (Qwikstar) for electroanatomic mapping of arrhythmias in patients with structural heart disease. The multielectrode catheter acquires activation times and anatomic data simultaneously from its tip and shaft electrodes. Eight patients (6 men, 2 women, age 47 years [37, 65]) with atrial tachycardia (n = 6) and ventricular tachycardia (n = 2) due to congenital heart disease (n = 4) and cardiomyopathy (n = 4) were studied. Using the multielectrode catheter, the electroanatomic map was constructed in two stages: (1) a scout map using the minimum number of tip and shaft electrode data points that covered > 70% of the tachycardia cycle length and/or the majority of the chamber volume, and (2) a complete map using additional tip electrode data points. A total of 36 (28, 510) tip electrode and 38 (34, 42) shaft electrode electroanatomic data points comprised the scout map. The complete map was constructed with a total of 102 (73, 134) tip electrode electroanatomic data points. In three patients, the scout map suggested a cavotricuspid isthmus dependent atrial flutter that was confirmed with the complete map. In another four patients, the scout map identified the earliest site of focal activation, which was also confirmed with the complete map. In comparison, activation mapping using the bipolar catheter (Navistar) in a group of arrhythmia-matched control subjects required 210 (180, 320) electroanatomic data points (P = 0.012 vs multielectrode catheter complete map). In conclusion, for large macroreentrant or focal arrhythmias in patients with structural heart disease, the multielectrode catheter can generate a scout map that accurately guides complete electroanatomic mapping using fewer point-by-point acquisitions than the bipolar catheter.     

Atrial Flutter Ablation using a Technique for Detection of Conduction Block within the Posterior Isthmus

Catheter ablation orientated on the induction of a functional intraatrial block within the posterior isthmus of the tricuspid annulus has been shown to effectively abolish atrial flutter. In order to improve and simplify the current technique, a strategy based on an electrode catheter for combined right atrial and coronary sinus mapping and stimulation was explored prospectively. Twenty-four consecutive patients referred for catheter ablation of recurrent type I atrial flutter were included. A steerable 7 Fr catheter (Medtronic/Cardiorhythm) composed of two segments with 20 electrodes was used for right atrial and coronary sinus activation mapping and stimulation. Multiple steering mechanisms allowing intubation and positioning of the distal part within the coronary sinus were incorporated into the device. Adequate positioning of the mapping catheter was achieved solely via a transfemoral approach in all patients after 7.7 +/- 4.6 minutes, providing stable electrogram recordings during the entire ablation procedure. Radiofrequency current ablation (16.3 +/- 9.6 pulses) caused a significant bidirectional increase of the mean intraatrial conduction times via the posterior isthmus irrespective to the stimulation interval. Significant changes of intraatrial conduction properties were induced during ablation in 22 of 24 patients (bidirectional block: n = 18, unidirectional block: n = 3, conduction delay: n = 1, unchanged conduction: n = 2). Following ablation atrial flutter was noninducible in all patients. Twenty-two of 24 patients (92%) remained free of atrial flutter episodes during a follow-up of 12.5 +/- 5.7 months. Two of six patients without a bidirectional conduction block had a recurrence of atrial flutter. Atrial flutter ablation guided by the induction of an intraatrial conduction block can be effectively performed with this novel strategy for combined mapping of the posterior tricuspid isthmus, including coronary sinus and right atrial free wall. This transfemoral approach has a high accuracy with respect to the detection of radiofrequency current-induced changes of intraatrial conduction patterns.     

Usefulness of the Noncontact Mapping System to Elucidate the Conduction Property for the Treatment of Common Atrial Flutter

Background: The functional role of the cavotricuspid isthmus (CTI) for common atrial flutter (cAFL) remains to be elucidated. In the present study, we examined whether the EnSite system (St. Jude Medical, St. Paul, MN, USA), a noncontact mapping system, is useful to evaluate the conduction properties of CTI to minimize radiofrequency (RF) ablation applications for cAFL. Methods: We enrolled 22 consecutive patients with cAFL (64.1 ± 9.5 years old, M/F 21/1) treated with the EnSite system and examined the conduction properties during cAFL and during atrial pacing. In addition, the effectiveness of the system was evaluated in comparison with the conventional ablation group (67 ± 8.9 years old, n = 15, M/F 13/2). Result: In 11 out of the 22 patients, CTI block line was achieved by fewer RF applications on a presumed single activation pathway which the EnSite system showed (point ablation [PA] group), and the remaining 11 patients needed additional linear ablation (additional ablation [AA] group). The number of RF applications in the PA group was significantly smaller than that in the conventional group. During the lower lateral right atrial pacing at a cycle length of 600 ms, the CV of the CTI in the PA group was smaller compared to that in the AA group (1.36 ± 0.61 vs 2.17 ± 0.66 m/s, P < 0.05), although the CV during cAFL (averaged cycle length 245 ± 34 ms) was not different in both groups. Conclusions: These results indicate that targeting the presumed single line identified by EnSite could be an optional therapy for cAFL RF ablation, and diverse conduction properties in CTI are related to the success rate of this procedure. (PACE 2012;35:1464–1471)     

Macroreentrant atrial flutter around a common atrioventricular canal in an infant with complicated congenital heart anomaly

This report describes a 2-year-old male infant after repair of complicated congenital heart anomalies including common atrioventricular canal (CAVC), in which macroreentrant atrial flutter around the CAVC was demonstrated by electroanatomic mapping (CARTO) using a single catheter. Radiofrequency catheter ablation at the isthmus between the CAVC and the inferior vena cava eliminated the atrial flutter successfully.     

Atrial Flutter Mapping and Ablation I

Endocardial mapping has led to a detailed knowledge of reentry mechanisms in atrial flutter. Multipolar and deflecting tip catheters allow recording local electrograms from multiple areas of the right atrium, and from the coronary sinus. In common flutter, with the typical "sawtooth" pattern, there is circular activation of the right atrium in a "counterclockwise" direction, descending in the anterior and lateral walls, and ascending in the septum and posterior wall. Superior and inferior vena cava, linked by a "line" of functional block in the posterolateral wall, make the central obstacle for circular activation. The cranial and caudal turning points are the atrial "roof," and the isthmus between the inferior vena cava and the tricuspid valve. Complex conduction patterns, probably including slow conduction are detectable in the low septal area, around the coronary sinus. Atypical flutter, without the sharp negative deflections of common flutter, sometimes shows circular activation in the right atrium, rotating in the opposite direction of common flutter (clockwise). Other atypical flutters show no circular right atrial activation, and only partial data from coronary sinus activation, combined with the response to atrial stimulation (entrainment) allow the diagnosis of left atrial reentry, without a precise delimitation of the circuits. In patients having undergone cardiac surgery, atypical flutter may be based on reentry around surgical scars. To our knowledge, the mechanism of type II flutter has not been disclosed in humans.     

Use of a New Non-Fluoroscopic Three-Dimensional Mapping System in Type I Atrial Flutter Ablation

We studied 40 patients who underwent cavo-tricuspid isthmus ablation for typical counterclockwise atrial flutter with cooled tip catheters between 2001 and 2003. Complete bi-directional isthmus block was created in all patients. A new, three-dimensional (3D), non-fluoroscopic mapping system was used in 20 patients (test group), and conventional fluoroscopy in 20 others (conventional group), using anatomic and electrophysiologic criteria in both groups. We measured the total procedure, ablation procedure, and overall fluoroscopy times, and the total number of radiofrequency (RF) applications delivered in the two groups. The overall fluoroscopy time was shorter in the test group (mean 8.8 minutes, range 2–17 minutes) than the conventional group (29.7 minutes, range 12–57 minutes; P < 0.001). Though the overall procedure time was similar in both groups (92.5 ± 28.6 minutes vs 106.5 ± 20.9 minutes; P = 0.067) the ablation duration (25.1 ± 6.6 minutes versus 43.3 ± 19.6 minutes; P = 0.0051) and the total RF applications (10.6 ± 9.4 versus 16.4 ± 9.4; P = 0.044) were smaller in the test group. The use of a new, 3D non-fluoroscopic mapping system markedly reduced the fluoroscopy exposure during typical atrial flutter ablation. It was also associated with a significant reduction in ablation time and in the number of RF applications. Since atrial flutter ablation is one of the most frequently performed procedures, this system may significantly reduce the overall amount of radiation exposure in high-volume laboratories.     

Electroanatomic mapping of the right atrium with a right atrial basket catheter and three-dimensional intracardiac echocardiography

The ablation of arrhythmias progresses towards an approach based upon application of linear lesions between nonconducting anatomic/electrical areas. Hence the identification of detailed anatomy together with electrical behavior becomes increasingly important. This study aims to achieve true electroanatomic mapping by the use of three-dimensional intracardiac imaging of the right atrium combined with use of a right atrial basket to obtain detailed electrical information. We studied nine patients, seven requiring atrial flutter ablation. A 9 Fr, 9 MHZ intracardiac echo catheter was pulled back from SVC to IVC using respiratory and ECG gating. The images, recorded on a Clearview ultrasound machine, were reconstructed using commercially available software. The intracardiac basket was placed into the atrium using the markers and fluoroscopy to allow orientation. Isochronal maps were obtained from the basket in sinus rhythm, pacing from different sites within the atrium and in atrial flutter. Isochronal maps were constructed and superimposed on the ICE image. The maps with pacing were consistent with that which was expected, confirming the validity of this approach. We were able to visualize changes in activation sequence following the placement of bidirectional isthmus block. True electroanatomic mapping is possible by the use of three-dimensional ICE reconstruction of the right atrium with electrical activation obtained from an intracardiac basket. This has significance for anatomically based arrhythmia ablations such as the ablation of atrial flutter, atrial fibrillation, with transcatheter MAZE procedures and pulmonary vein isolation. Further developments in software will allow such maps to be produced simultaneously with greater rapidity.     

Late Recurrence of Atrial Flutter Following Radiofrequency Catheter Ablation

The success rate for catheter ablation of atrial flutter has been reported to be approximately 90%, but recurrences are common and can be seen in up to 20% of cases. Most of these recurrences are seen within a few weeks following ablation. We report on a patient who developed a recurrence of type I atrial flutter 2 years after an initially successful radiofrequency catheter ablation procedure. Whether the recurrent atriai flutter is due to a new reentrant circuit resulting from slow progression of atrial disease or due to the changes produced by radiofrequency energy in the nearby myocardium is not clear. Further work to define the electrophvsiological changes in the atrial myocardium produced by radiofrequency energy, as well as long-term follow-up of patients undergoing radiofrequency catheter ablation for atrial flutter may help in answering these questions.     

Catheter Ablation of Focal Atrial Tachycardia from the Aortic Cusp: The Role of Electroanatomic Mapping and Intracardiac Echocardiography

Catheter ablation of periatrioventricular (peri‐AV) nodal atrial tachycardias (AT) from the noncoronary aortic cusp (NCC) can be challenging due to the close proximity of the AV node In such cases, intracardiac echocardiography (ICE) together with three‐dimensional mapping system can be helpful in guiding the ablation catheter and in assessing the anatomic relationship of the aorta to the surrounding structures. We report two patients with AT originating near the AV node who underwent successful catheter ablation from the NCC. ICE proved useful in positioning the ablation catheter within the aortic cusps. Electroanatomic mapping enabled tagging the earliest activation site and renavigation back. (PACE 2013; 36:e19–e22)     

Atrial Flutter Mapping and Ablation II. Radiofrequency Ablation of Atrial Flutter Circuits

The definition of the anatomical substrate of reentry in at rial flutter has allowed the recognition of narrow, critical areas of the circuit, where radiofrequencv ablation can interrupt reentry. In common flutter the isthmus between the inferior vena cava and the tricuspid valve appears the best target, but ablation between the coronary sinus and tricuspid valve can also be effective in some cases. In atypical flutter using the same circuit as common flutter in a “clockwise” direction, ablation of the same isthmus is effective. Flutter interruption is the main objective, but it does not mean complete isthmus ablation. If flutter remains inducible, new applications are delivered in the isthmus, until it is made noninducible. Complications are rare. Despite attaining noninducibility, flutter may recur, and new procedures may he needed to prevent recurrence. Atrial fibrillation can occur in up to 30% of the cases during follow-up, but it is generally well controlled with antiarrhythmic drugs, that were ineffective to treat flutter before ablation. In reentry circuits based on surgical atrial scars, ablation of an isthmus between the scar and the inferior vena cava can also be effective. Left atrial circuits are not known well enough to guide successful ablation.     

Relation Between Left Atrial Size and Secondary Atrial Arrhythmias After Successful Catheter Ablation of Common Atrial Flutter

Catheter ablation ptovides an effective cure for patients with typical atrial flutter. However, these patients may have the potential to develop atrial tachyarrhythmias other than common atrial flutter. This study examines clinical and echocardiographic predictors for the occurrence of uncommon atrial flutter or atrial fibrillation after abolition of common atrial flutter. The study population comprised 17 patients (12 men, 5 women, age 32–74 years) who underwent successful radiofrequency catheter ablation of common atrial flutter. Common atrial flutter did not recur in any patient during a median follow-up time of 8 (range 1–25) months. Within a median of 7 (range 1–223) days, however, symptomatic atrial tachyarrhythmias occurred in 8 of 17 patients (47%): uncommon atrial flutter (n = 4); atrial fibrillation (n = 3); and both uncommon atrial flutter and atrial fibrillation in one patient. Preablation left atrial volume was significantly larger in patients who developed secondary arrhythmias compared with patients who remained in sinus rhythm (57.9 ± 15.6 vs 43.7 ± 16.4 cm³, P < 0.05). Enlarged left atrial volume dichotomized at 51 cm³ independently predicted postablation atrial arrhythmias (x²=5.11, rel. risk = 5.3, P < 0.05). On Kaplan-Meier analysis, time to occurrence of postablation atrial arrhythmias was significantly shorter in patietits with enlarged left atrium (P < 0.02). In conclusion, symptomatic uncommon atrial flutter and atrial fibrillation develops in a substantial proportion of patients after successful ablation of common atrial flutter. Out of a series of clinical and echocardiographic parameters, preablation left atrial size is the best predictor for the occurrence of these postablation atrial arrhythmias.     

Randomized Comparison of Efficacy of Cooled Tip Catheter Ablation of Atrial Flutter: Anatomic Versus Electrophysiological Complete Isthmus Block

There is a subset of patients with failed ablation of the cavotricuspid isthmus (CTI) using standard catheters and with 10% of the patients having recurrences. The purpose of this study was to compare the cooled and standard ablation with regard to acute successful electrophysiological achievement of bidirectional isthmus block and the subacute anatomic characteristics of the lesions. This randomized, experimental study compares the effects of ablation on the isthmus using a cooled catheter with those of a standard ablation catheter in 16 pigs. In 12 animals, CTI block was achieved after ablation (8/8 cooled and 4/8 standard). In two animals, it was not possible to achieve complete isthmus block and two had persistent slow conduction (all four using the standard catheter). After 1 week, the animals were slaughtered. The size of the lesion was greater with the irrigated tip catheters. Transmural lesions were found in 14 animals. A complete line of anatomic isthmus block was not documented after thefirst line in six animals, four with the standard and two with the cooled catheter. A conduction block was never present across gaps > or = 5 mm. In conclusion cooled catheters achieved a complete line of electrophysiological and anatomical block in a significantly higher percentage than the standard catheters.     

Electroanatomic mapping of endocardial right ventricular activation as a guide for catheter ablation in patients with arrhythmogenic right ventricular dysplasia

Arrhythmogenic right ventricular dysplasia is a structural heart disease characterized by fibrofatty degeneration of right ventricular myocardium and arrhythmias of right ventricular origin. The aim of this study was to characterize endocardial right ventricular activation by electroanatomic mapping as a guide for catheter ablation in patients with arrhythmogenic right ventricular dysplasia. Electroanatomic mapping and entrainment procedures were performed in 5 patients with arrhythmogenic right ventricular dysplasia. Endocardial mapping during ventricular tachycardia demonstrated a focal activation pattern with radial spreading of activation from a site of earliest ventricular activation in all directions. Right ventricular activation time (127 +/- 34 ms) was markedly shorter than tachycardia cycle length (415 +/- 92 ms). The site of earliest ventricular activation was found in an aneurysmal outflow tract (n = 2), at the border of aneurysms near the tricuspid annulus (n = 2), and at the apex of the right ventricle (n = 1). Entrainment mapping criteria of these areas of earliest endocardial activity were consistent with exit sites of a reentrant circuit in an area of abnormal myocardium. Fractionated potentials were found 61 +/- 29 ms before the onset of the QRS complex at these sites. Catheter ablation rendered the "clinical" ventricular tachycardia noninducible in four patients but "nonclinical" faster ventricular tachycardias were inducible in three patients. During the follow-up of 7 +/- 3 months after ablation, the frequency of therapies in 4 patients with an implantable cardioverter defibrillator decreased from 49 +/- 61 episodes per month before ablation, to 0.3 +/- 0.5 episodes per month after ablation (P < 0.05). Electroanatomic mapping during ventricular tachycardia facilitates localization of exit sites in relation to aneurysms in diseased right ventricle and may guide catheter ablation in patients with arrhythmogenic right ventricular dysplasia.     

Classic and Concealed Entrainment of Typical and Atypical Atrial Flutter

Classic and concealed entrainment was demonstrated in a patient with spontaneous typical atrial flutter and pacing induced atypical atrial flutter. The form of enirainment manifested depended on the site of pacing and the direction of tachycardia as determined by endocardial mapping.