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This study was aimed at evaluating the efficacy of non-contact mapping and ablation of non-incisional atypical right atrial (RA) flutters.The majority of atypical RA flutters were reported in patients after surgical incision of the RA.The study group consisted of 15 patients (61 ± 13 years, 8 males) with atypical atrial flutter (AFL). The RA activation during AFL was delineated using a non-contact mapping system (EnSite 3000 with Precision Software, Endocardial Solutions, St. Paul, Minnesota). The narrowest part of each reentrant circuit was targeted using radiofrequency energy.In all 15 patients, non-contact mapping showed AFLs confined to the RA with RA activation time accounting for 100% of the cycle length (210 ± 19 ms). During single-loop re-entry in seven patients, the activation wave front circulated around the central obstacle (CO) in the anterolateral wall with conduction through the channel between the CO and the crista terminalis (CT). During figure-of-eight re-entry in eight patients, simultaneous upper and lower loop re-entry through the conduction gap in the CT was found in four patients, and simultaneous upper loop and free-wall single-loop re-entry was observed in four patients. Radiofrequency ablation of the free-wall channel and/or CT gap was effective in eliminating these AFLs in 13 patients. During a follow-up of 16.8 ± 3.8 months, two patients had recurrence of left AFL, and one had recurrence of atrial fibrillation.Atypical RA flutters could arise from single-loop or double-loop figure-of-eight re-entry. Radiofrequency ablation of the free-wall channel and/or the CT gap was effective in eliminating these arrhythmias. [Copyright &y& Elsevier]

: ObjectivesThe aim of the study was to investigate the conduction properties and anisotropy of the crista terminalis (CT) in patients with atrial flutter (AFL) using non-contact mapping.: BackgroundThe CT is a posterior barrier during typical AFL. However, the CT has transverse conduction capabilities in patients with upper loop re-entry (ULR).: MethodsTwenty-two patients (16 males, 63 ± 15 years) with typical AFL and ULR were included. Non-contact mapping of the right atrium during AFL and pacing from coronary sinus (CS) and low anterolateral right atrium (LARA) was performed to evaluate transverse conduction across the CT. During ULR, the longitudinal (CVL) and transverse (CVT) conduction velocity along and across the CT were measured. The width of the CT conduction gap was evaluated to guide radiofrequency ablation (RFA).: ResultsNo transverse CT gap conduction was found during typical AFL. Transverse CT gap conduction was found in three patients during CS pacing and in three patients during LARA pacing. During ULR, CVL was greater than CVT (1.28 ± 0.43 vs. 0.73 ± 0.30 m/s, p < 0.001). The CVL/CVT ratio was 1.95 ± 0.77, which was inversely related to the CT gap width (15.7 ± 6.8 mm) (p < 0.001). The RFA of the CT gap was successful in 18 patients. Four patients had recurrence of arrhythmias during the follow-up of 11 ± 3 months.: ConclusionsMost of the CT conduction gaps were functional and only appeared during ULR. The width of the CT gap was inversely related to the anisotropic ratio of the CT. The RFA of the CT gap was effective in eliminating ULR. [Copyright &y& Elsevier]

Noncontact Mapping of SVC Tachycardia. Introduction: Information about the activation patterns inside the superior vena cava (SVC) and entry and exit sites at the SVC-right atrial (RA) junction during SVC tachyarrhythmia is limited. Methods and Results: A detailed characterization of electrophysiologic mechanisms and ablation strategies was performed using a noncontact three-dimensional mapping system in two cases of SVC tachycardia. The first case demonstrated SVC tachycardia originating from an ectopic focus inside the SVC, with sustained depolarization and conduction to the atrium. Entry and exit sites across the SVC-RA junction were located very close to each other. The second case demonstrated two different reentrant circuits, one inside the SVC and the other into and out of the SVC-RA junction. The entry and exit sites were located far away from each other. Conclusion: Noncontact mapping may help to reveal the mechanism of SVC tachyarrhythmias and to locate entry and exit sites at the SVC-RA junction as a guide for catheter ablation.(J Cardiovasc Electrophysiol, Vol. 14, pp. 533-539, May 2003). [ABSTRACT FROM AUTHOR]

Background: Although the reentrant circuit of typical atrial flutter (AFL) has been well recognized, the activation around the Eustachian ridge (ER) has not been fully characterized. The aim of this study was to delineate the activation patterns around the ER during typical AFL using high-resolution noncontact mapping. Methods: Fifty-three patients (M/F = 43/10, 62 ± 14 years) with typical AFL were included. The high-resolution mapping of the right atrium using a noncontact mapping system during AFL and pacing from the coronary sinus (CS) was performed to evaluate the conduction through the ER. Results: Three types of activation patterns around the ER could be classified according to the ER conduction during AFL and CS pacing. Type I (n = 21, M/F = 16/5, 61 ± 13 years) exhibited conduction block at the ER during AFL and CS pacing. The local unipolar electrograms at the ER exhibited long double potentials (DPs) (109 ± 12 ms, range 77–153 ms) during AFL and CS pacing (84 ± 18 ms, range 48–129 ms). Type II (n = 8, M/F = 7/1, 61 ± 15 years) exhibited conduction block at the ER during AFL, but conduction through the ER during CS pacing. The unipolar electrograms exhibited long DPs (119 ± 12 ms, range 97–141 ms) at the ER during the tachycardia and an rS pattern during CS pacing. Type III (n = 24, M/F = 20/4, 61 ± 16 years) exhibited an activation wavefront that passed along the ER, with the sinus venosa as the posterior barrier during AFL. During CS pacing, all cases exhibited conduction through the ER with an rS pattern. Conclusions: This study is the first to demonstrate the three patterns of activation along the ER during AFL and CS pacing. This finding suggested that the ER is an anatomic and functional barrier during typical AFL. [ABSTRACT FROM AUTHOR]

LIN, Y.-J.,et al.: Electrophysiological Mechanisms and Catheter Ablation of Complex Atrial Arrhythmias from Crista Terminalis: Insight from Three-Dimensional Noncontact Mapping. Paroxysmal atrial fibrillation (PAF) can be initiated by ectopic activation from the crista terminalis. The crista terminalis conduction gap is also a critical isthmus in atrial reentrant arrhythmias like upper and lower loop reentry. The aim of this study was to investigate the mechanism and results of catheter ablation for complex atrial arrhythmias originating from the crista terminalis using the noncontact mapping system (NCM). The study population consisted of six patients (5 men, 1 woman; 70± 9 years) with drug refractory PAF and typical/atypical atrial flutter. NCM identified the earliest ectopic activation originating from the crista terminalis in these six patients. The reentry circuit of atypical atrial flutter propagated around the upper crista terminalis in five patients, and lower crista terminalis in one patient. The reentry circuit of atypical atrial flutter and the initial reentry circuit of AF conducted through the crista terminalis gap in all patients. Radiofrequency applications were delivered on the sites of ectopy, which initiated AF. Substrate modification was also performed over the crista terminalis gap (six patients) and cavotricuspid isthmus (three patients) responsible for the reentry. During a mean follow-up of 9± 5 months (range 5–18 months), five patients were free of AF without antiarrhythmic drugs, and one patient did not have AF or atrial flutter using propafenone. NCM demonstrated the mechanism of crista terminalis ectopy-initiating AF and associated typical/atypical atrial flutter. Catheter ablation of crista terminalis ectopy and substrate for the reentry guided by NCM successfully eliminated these atrial arrhythmias.(PACE 2004; 27:1231–1239) [ABSTRACT FROM AUTHOR]

Discusses a case of a woman with a narrow complex tachycardia with ventriculoatrial dissociation after catheter ablation of atrioventricular nodal reentrant tachycardia. Factors that favor nodofascicular tachycardia; Observation on the junctional tachycardia related to injury to the atrioventricular node; Differential diagnosis.

Abstract: Background: Atrioventricular nodal reentrant tachycardia (AVNRT) is the most common supraventricular tachycardia in adulthood. Although selective ablation of the slow AV nodal pathway can cure AVNRT, accidental AV block may occur. The details on the electrophysiologic characteristics, quantitative data on the voltage inside Koch''s triangle, and the use of three-dimensional noncontact mapping to facilitate the catheter ablation of AVNRT associated with a high-risk for AV block or other arrhythmias have been limited. Methods and results: Nine patients (M/F =5/4, 34±23 years, range 17–76) with clinically documented AVNRT were included. All patients had undergone previous sessions for slow AV nodal pathway ablation but they had failed, because of repetitive episodes of complete AV block during the RF energy applications. Further, one patient had a complex anatomy and 4 patients were associated with other tachycardias, respectively. The electrophysiologic studies revealed that 4 patients had the slow–fast, 4 the slow–intermediate and one the fast–intermediate form of AVNRT. Noncontact mapping demonstrated two types of antegrade AV nodal conduction, markedly differing sites of the earliest atrial activation during retrograde VA conduction, and a lower range of voltage within Koch''s triangle. The lowest border of the retrograde conduction region was defined on the map, and the application of the RF energy was delivered below that border to prevent the occurrence of AV block. The distance between the successful ablation lesions and the lowest border of the retrograde conduction region was significantly shorter in the patients with the slow–intermediate form of AVNRT than in those with the slow–fast form (5.5±3.4 vs. 15±7.6 mm; p <0.05). After the ablation procedure, either rapid pacing or extrastimulation could not induce any tachycardia, and there was no recurrence during the follow-up (10.3±5.4, 2 to 22 months). Conclusions: Noncontact mapping could effectively demonstrate the antegrade and retrograde atrionodal conduction patterns, electrophysiologic characteristics of Koch''s triangle, and guide the successful catheter ablation in difficult AVNRT cases. [Copyright &y& Elsevier]

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 ≤ 0.001). Voltage measurement revealed significant differences between reverse typical AFL and ULR in leads I, II, aVR, aVF, V1, and V2 (p &#60; 0.001). A new diagnostic algorithm based on negative or isoelectric/flat flutter wave polarity and amplitude ≤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. [Copyright &y& Elsevier]

Right Atrial Substrate of Supraventricular Tachyarrhythmias. Background:Voltage mapping has been used to detect diseased myocardium. However, accurate determination of the local atrial voltage at the same site, and simultaneous recordings from multiple mapping sites were limited. The purpose of this study was to investigate the right atrial (RA) substrate properties in patients with supraventricular tachyarrhythmias (SVT).Methods and Results:Forty patients (aged 55± 20 years) undergoing noncontact mapping and ablation of SVT constituted the study population. There were eight patients with atrioventricular node reentrant tachycardia (AVNRT), eight patients with focal atrial tachycardia (AT), 14 patients with atrial flutter (AFL), and 10 patients with atrial fibrillation (AF). The mean peak negative voltage (PNV) was analyzed in virtual unipolar electrograms, which were obtained from 256 equally distributed RA endocardial sites during sinus rhythm (SR), atrial pacing, and tachycardia. The mean PNV of global RA during SR (−1.34± 0.22 vs.−0.90± 0.40 vs.−1.00± 0.36 vs.−0.85± 0.35 mV, P= 0.04), atrial pacing at cycle lengths of 500 ms (−1.30± 0.29 vs.−0.70± 0.35 vs.−0.76± 0.25 vs.−0.64± 0.26 mV, P= 0.02), and 300 ms (−1.54± 0.47 vs.−0.94± 0.21 vs.−0.75± 0.27 vs.−0.57± 0.22 mV, P<0.01) were significantly greater in patients with AVNRT compared to AT, AFL, and AF. Furthermore, the mean PNV decreased during atrial pacing with shorter pacing cycle length was demonstrated only in patients with AFL and AF.Conclusion:Negative unipolar voltage analysis of global RA showed different RA substrate characteristics during various SVT. The substrate property of activation and cycle length-dependent voltage reduction may be related to the development of AFL and AF.(J Cardiovasc Electrophysiol, Vol. 16, pp. 1-8, March 2005) [ABSTRACT FROM AUTHOR]

Focal Atrial Tachycardia. Introduction:Adenosine can terminate most focal atrial tachycardias (ATs). However, information about the termination mechanism is limited. This study investigated the effects and mechanism of adenosine on terminating focal AT using a three-dimensional noncontact mapping system.Methods and Results:The study consisted of 7 patients (4 men and 3 women; age 44± 29 years) with focal AT. Cycle length variation and atrial activation pattern at baseline and just before AT termination by adenosine (3–12mg) were analyzed. Noncontact mapping demonstrated focal AT propagated from the origin (O) with preferential conduction and spread away from the breakout sites to the whole atrium. Compared to baseline AT, termination episodes revealed higher mean beat-to-beat variation of AT cycle length (11.7± 11.7 msec vs 4.7± 4.5 msec, P<0.001) and standard deviation of normalized AT cycle length (0.033± 0.014 vs 0.011± 0.005, P<0.001). In termination episodes, adenosine significantly decreased the peak negative voltage of AT-O (–27.2± 15.3%, P<0.01), preferential conduction (proximal:–32.1± 18.7, mid:–28.4± 22.8, distal portion:–29.6± 21.4%, P<0.01), and breakout (–31.4± 12.5%, P<0.01). However, adenosine did not affect voltage in nontermination episodes. Adenosine shifted the locations of AT-O in 5 of 10 AT episodes with termination. Mean number of shifting AT-O was 2.4± 1.5 (range 1–4), with maximum shifting distance of 15.0± 3.1 (range 10–19) mm. Focal activation at AT-O simply disappeared in all termination episodes and therefore was not due to conduction block within preferential conduction or breakout site. Catheter ablation lesions covered 50% of total shifting origins, without late recurrence.Conclusion:Adenosine-induced AT termination was associated with significantly decreased electrogram voltage, shifting AT-O locations, and disappearance of focal activation.(J Cardiovasc Electrophysiol, Vol. 15, pp. 1-7, December 2004) [ABSTRACT FROM AUTHOR]

Repolarization Changes During SVT. Introduction: Previous literature has documented the association between narrow QRS supraventricular tachycardia (SVT) and pronounced ST-T segment change. The aim of this study was to evaluate repolarization changes during SVT initiation and demonstrate the possible mechanism. Methods and Results: Fifty-one consecutive patients (20 men and 31 women; mean age 46.1 ± 16.4 years) with narrow QRS SVT (32 patients with AV nodal reentrant tachycardia and 19 patients with AV reentrant tachycardia) were included. We retrospectively analyzed the intracardiac recordings and ST-T segment changes on 12-lead surface ECGs during SVT initiation. Twenty-six (51%) patients developed ST segment repolarization changes during SVT initiation. Patients with shorter baseline sinus cycle length, shorter tachycardia cycle length, elevated systolic blood pressure before tachycardia induction, and greater reduction of systolic blood pressure had a higher incidence of repolarization changes. However, multivariate analysis showed that reduction of systolic blood pressure after SVT induction was the only independent predictor of repolarization changes. Furthermore, the maximal degree of ST segment depression during SVT correlated with the reduction of systolic blood pressure (r = 0.75, P < 0.001). Conclusion: Repolarization changes during SVT initiation were caused mainly by concurrent hemodynamic change after SVT initiation with abrupt cycle length shortening. [ABSTRACT FROM AUTHOR]

Objectives: The purpose of this study was to investigate the characteristics of the second component of local virtual unipolar electrograms recorded at the ablation line during coronary sinus (CS) pacing after radiofrequency ablation (RFA) of the cavotricuspid isthmus (CTI) for typical atrial flutter (AFL).Background: Radiofrequency ablation of the CTI can produce local double potentials at the ablation line. The second component of unipolar electrograms represents the approaching wavefront in the right atrium opposite the pacing site. We hypothesized that the morphologic characteristics of the second component of double potentials would be useful in detecting complete CTI block.Methods: Radiofrequency ablation of the CTI was performed in 52 patients (males = 37, females = 15, 62 ± 12 years) with typical AFL. The noncontact mapping system (Ensite 3000, Endocardial Solutions, St. Paul, Minnesota) was used to guide RFA. Virtual unipolar electrograms along the ablation line during CS pacing after RFA were analyzed. Complete or incomplete CTI block was confirmed by the activation sequence on the halo catheter and noncontact mapping.Results: Three groups were classified after ablation. Group I (n = 37) had complete bidirectional CTI block. During CS pacing, the second component of unipolar electrograms showed an R or Rs pattern. Group II (n = 12) had incomplete CTI block. The second component of unipolar electrograms showed an rS pattern. Group III (n = 3) had complete CTI block with transcristal conduction. The second component of unipolar electrograms showed an rSR pattern.Conclusions: A predominant R-wave pattern in the second component of unipolar double potentials at the ablation line indicates complete CTI block, even in the presence of transcristal conduction. [Copyright &y& Elsevier]