The impact of age on the electrophysiological characteristics and different arrhythmia patterns in patients with Wolff-Parkinson-White syndrome.

INTRODUCTION: Information about the impact of age on the electrophysiological characteristics of accessory pathways (APs) in patients with Wolff-Parkinson-White (WPW) syndrome remains limited. METHODS AND RESULTS: A total of 1,885 consecutive patients (mean age 43 ± 17 years, male 61.5%) with WPW syndrome who were referred to the tertiary center for an electrophysiological study and radiofrequency catheter ablation were investigated. The patients were divided into 4 groups based on their age (Group 1: <20; Group 2: 20-39; Group 3: 40-59; Group 4: ≧60 years old). With age, more left-sided APs (53.2%, 67.7%, 71.7%, 75.7%, P < 0.001) and a longer duration of the arrhythmia (4.3 ± 2.8 years, 10.1 ± 7.0 years, 12.4 ± 10.9 years, 14.0 ± 12.4 years, P < 0.001) were noted. The incidence of concealed APs (53.5%, 53.0%, 57.8%, 60.9%, P = 0.01), and orthodromic atrioventricular (AV) reentrant tachycardia (92.4%, 94.2%, 96.5%, 96.3%, P = 0.023) increased with age. The tachycardia cycle length, antegrade (275.5 ± 42.2 ms, 286.7 ± 62.7 ms, 302.5 ± 66.5 ms, 315.2 ± 80.2 ms, P < 0.001) and retrograde AP effective refractory periods (APERPs) (254.0 ± 42.5 ms, 263.3 ± 51.8 ms, 274.5 ± 100.5 ms, 292.7 ± 57.0 ms, P < 0.001), atrial ERP, antegrade AV node effective refractory period (AVNERP), and ventricular effective refractory period (VERP) lengthened as the age increased. The incidence of decremental APs, multiple APs, and a catecholamine response were similar. The duration of the catheter ablation, total fluoroscopy time, acute success rate, complication rate, and incidence of a secondary procedure were similar between the different age groups. CONCLUSION: The electrophysiological characteristics and pattern of the arrhythmic attack associated with the AP changed with age.

Gender differences of electrophysiological characteristics in focal atrial tachycardia.

Gender differences of supraventricular tachycardias such as atrioventricular nodal re-entry, atrioventricular re-entry, and atrial fibrillation have been reported. There is little evidence of the effect of gender on focal atrial tachycardia (FAT). The study consisted of 298 patients who were referred to this institution for radiofrequency catheter ablation of FAT from October 1992 to April 2008 and included 156 men (52%) and 142 women (48%). Men were significantly older than women (57.9 +/- 18.2 vs 47.2 +/- 19.0 years old, p <0.001). Women had more associated arrhythmias (17.0% vs 28.9%, p = 0.01), mostly due to an increased incidence of atrioventricular nodal re-entrant tachycardia. Men had more cardiovascular co-morbidities (19.9% vs 9.9%, p = 0.02), a mechanism of increased automaticity (19.1% vs 8.1%, p = 0.01), and nonparoxysmal tachycardia (14.7% vs 4.4%, p = 0.01). No gender differences were noted among FAT number, left atrial involvement, shortest tachycardia cycle, success rate of catheter ablation, or recurrence rate of FAT. Mean duration of follow-up was 63.2 +/- 47.5 months. Premenopausal women had a lesser cardiovascular co-morbidity (15.3% vs 4.3%, p = 0.04) and a greater incidence of a mechanism of increased automaticity (13.4% vs 2.9%, p = 0.03). In conclusion, gender differences in electrophysiologic characteristics were noted in FAT.

Electrophysiologic characteristics and catheter ablation of focal atrial tachycardia with more than one focus.

BACKGROUND: Information about the electrophysiologic characteristics and long-term outcome of catheter ablation in patients with multiple focal atrial tachycardia (AT) is limited. OBJECTIVE: The purpose of this study was to investigate the electrophysiologic characteristics and long-term outcome of catheter ablation in patients with multiple focal AT. METHODS: Two hundred fifty-one patients who were referred for radiofrequency catheter ablation of focal AT were included for analysis. RESULTS: Forty-four patients who had focal AT with more than one focus were identified. Comparing focal AT with a single focus to that with more than one focus, the existence of a left atrial focus, cardiovascular comorbidity, nonparoxysmal tachycardia, shortest tachycardia cycle length, success rate of the ablation, and procedure time all differed. Multivariate logistic analysis revealed that a left atrial focus, cardiovascular comorbidity, and shortest tachycardia cycle length were independent predictors of focal AT with more than one focus. Noncontact mapping of the right atrium revealed larger low-voltage zone and longer total activation time for focal AT with more than one focus. Patients who had focal AT with more than one focus and a failed ablation had a greater number of focal ATs and mechanisms of nonparoxysmal tachycardia. Multivariate logistic analysis revealed that only the number of focal ATs predicted a failed ablation. CONCLUSION: Focal ATs with more than one focus have different electrophysiologic characteristics. This study provides new insight into the development and atrial remodeling of focal AT with multiple foci.

Induced atrial tachycardia after circumferential pulmonary vein isolation of paroxysmal atrial fibrillation: electrophysiological characteristics and impact of catheter ablation on the follow-up results.

INTRODUCTION: Atrial tachycardia (AT), including focal and reentrant AT, can occur after circumferential pulmonary vein isolation (CPVI). The aim of this study was to investigate the electrophysiological characteristics of induced AT and its clinical outcome. METHODS AND RESULTS: In our series of 160 patients with paroxysmal atrial fibrillation (AF), 45 ATs were induced by high-current burst pacing after CPVI in 26 patients. All induced ATs were mapped using a three-dimensional (3D) mapping system. Noninducibility was the endpoint of the ablation of the AT. Gap-related AT was considered if the AT was related to the CPVI lesions. A 16-slice multidetector computed tomography scan was performed in all patients to correlate the anatomical structure with electroanatomical mapping. Thirty-five (78%) reentrant ATs and 10 (22%) focal ATs were identified. Of those, 34 were gap-related ATs (24 reentrant and 10 focal ATs). Reentrant AT had more gaps in the left atrial appendage ridge than did focal AT (39.6% vs 0%, P = 0.02). Focal AT had a higher incidence of gap in the PV carina compared with reentrant AT (80% vs 10%, P < 0.001). Reentrant ATs were mostly terminated during the ablation creating the mitral and roof lines with crossing of the gaps. During a mean follow-up of 21 +/- 8 months, only one patient (0.6%) with induced mitral reentry had a recurrent AT. CONCLUSION: The location of the AT gap may be related with the complex anatomy of the LA. The induced ATs after CPVI can be eliminated by catheter ablation.

The results of radiofrequency catheter ablation of supraventricular tachycardia in children.

BACKGROUND: Radiofrequency (RF) catheter ablation represents a major advance in the management of children with cardiac arrhythmias and has rapidly become the standard of care for the first-ling therapy of supraventricular tachycardias (SVTs). The purpose of this study was to investigate the results of the RF catheter ablation of SVTs in pediatric patients. METHODS: From December 1989 to August 2005, a total of 228 pediatric patients (age: 9 +/- 7 years, range: 5-18 years; male:female = 117:111) with clinically documented SVT underwent an electrophysiologic study and RF catheter ablation at our institution. RESULTS: The arrhythmias included atrioventricular reentrant tachycardia (AVRT; n = 140, 61%), atrioventricular nodal reentrant tachycardia (AVNRT; n = 66, 29%), atrial tachycardia (AT; n = 11, 5%), and atrial flutter (AFL; n = 11, 5%). The success rate of the RF catheter ablation was 92% for AVRT, 97% for AVNRT, 82% for AT, and 91% for AFL, respectively. Procedure-related complications were infrequent (8.7%; major complications: high grade AV block (2/231, 0.9%); minor complications: first degree AV block (6/231, 2.6%), reversible brachial plexus injury (2/231, 0.9%), and local hematomas or bruises (10/231, 4.3%)). The recurrence rate was 4.7% (10/212) during a follow-up period of 86 +/- 38 months (0.5-185 months). CONCLUSIONS: The RF catheter ablation was a safe and effective method to manage children with paroxysmal and incessant tachycardia. The substrates of the arrhythmias differed between the pediatric and adult patients. However, the success rate of the ablation, complications, and recurrence during childhood were similar to those of adults.

The specific electrophysiologic characteristics in children with the atypical forms of atrioventricular nodal reentrant tachycardia.

BACKGROUND: Atrioventricular nodal reentrant tachycardia (AVNRT) is well known to be one of the most common supraventricular tachycardias in childhood. However, information about the atypical forms of AVNRT in childhood is limited. The purpose of this retrospective study was to investigate the clinical and electrophysiologic characteristics in pediatric patients with the atypical forms of AVNRT. METHODS: One hundred and three pediatric patients with AVNRT were included (aged 8-18 years; 44 male, 59 female). There were 10 (9.7%) children with the atypical forms (group 1), 86 (83.4%) with the slow-fast form (group 2) and 7 (6.9%) with the fast-slow form of AVNRT (group 3). The electrophysiologic characteristics and results of the radiofrequency catheter ablation were compared among these 3 groups. RESULTS: Group 2 patients were associated with an older age when compared with the other two groups. A significantly higher incidence of retrograde dual atrioventricular nodal pathways and a higher percentage of ventricular pacing- and extrastimulation-induced AVNRT were demonstrated in the children with the fast-slow form of AVNRT. The children with the atypical forms of AVNRT had a greater difference in the antegrade 1:1 conduction (100 +/- 73 vs. 52 +/- 41 vs. 35 +/- 26 ms, p = 0.003). Furthermore, the children with the slow-fast form of AVNRT had a greater difference in the retrograde 1:1 conduction (125 +/- 97 vs. 42 +/- 35 vs. 65 +/- 79 ms, p = 0.012). CONCLUSION: This study demonstrated that the pediatric patients with the atypical forms of AVNRT had different electrophysiologic characteristics than those with the slow-fast or fast-slow forms of AVNRT. The results of radiofrequency catheter ablation were similar for all children with the slow-fast, fast-slow and atypical forms of AVNRT.

Noncontact three-dimensional mapping guides catheter ablation of difficult atrioventricular nodal reentrant tachycardia.

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.

The electrophysiologic characteristics of atrioventricular nodal reentry tachycardia with eccentric retrograde activation.

BACKGROUND: The occurrence of eccentric retrograde atrial activation has been demonstrated to be from 6 to 8% in patients with atrioventricular nodal reentrant tachycardia (AVNRT) by several previous reports. However, most of those reports were limited by the absence of coronary sinus venography to confirm if the retrograde activation was truly left sided. The purposes of this study were to 1) determine the incidence of left sided retrograde atrial activation in our center, 2) determine the specific electrophysiologic characteristics of eccentric and concentric atrial activation and 3) determine the outcome of radiofrequency catheter ablation for AVNRT with eccentric retrograde atrial activation. METHODS: From November 2001 to July 2004, 290 consecutive patients with AVNRT who underwent an electrophysiologic study and radiofrequency ablation were included. Group 1 consisted of AVNRT patients with eccentric retrograde atrial activation; group 2 consisted of AVNRT patients with concentric retrograde atrial activation. The electrophysiologic characteristics of the group 1 and group 2 patients were then compared. RESULTS: The incidence of AVNRT with eccentric retrograde activation confirmed by CS venography was 6.5%. There were more females and atypical AVNRT in patients with retrograde eccentric conduction. There was more VA block after ablation and tachycardia induction by right ventricular pacing/extrastimuli in eccentric rather than concentric retrograde atrial activation. A shorter antegrade fast functional refractory period of the AV node was demonstrated in the atypical eccentric group as compared to the atypical concentric group. CONCLUSION: This study demonstrated the different electrophysiologic characteristics between the AVNRT patients with eccentric and concentric retrograde atrial activation. Successful ablation sites were similar to the standard RA ablation sites in patients with retrograde eccentric conduction.

High-resolution mapping around the eustachian ridge during typical atrial flutter.

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.

Coronary sinus morphology in different types of supraventricular tachycardias.

BACKGROUND: Atrioventricular nodal reentry tachycardia (AVNRT) is based on the concept of dual AV node pathways that are functionally and anatomically distinct. The bigger coronary sinus ostium (CSO) in patients with AVNRT compared to other supraventricular tachycardias (SVTs) may produce separation of atrial inputs into the AV node or create anisotropic conduction, thus giving rise to a different AV nodal physiology. Previous studies measuring the size of the CSO using CS angiography between patients with AVNRT and other SVTs showed conflicting results. Besides, no previous studies have compared the CS morphology of the different forms of AVNRT. OBJECTIVES: This study compares the size and morphology of the CS among patients with typical AVNRT, atypical AVNRT and accessory pathways mediated reentrant tachycardia (AVRT). METHODS: Ninety-six patients with clinically documented SVTs were divided into three groups. The diameter of the CS was measured in LAO projection during end ventricular systole (by choosing the last ventricular inward motion). The CSO as well as 5, 10 and 15 mm inside the CS were measured. CS morphology is defined as either wind-sock shape or tubular shape. RESULTS: The size of the CS ostium was 13.58 +/- 3.98, 15.93 +/- 4.86 and 12.50 +/- 2.83 mm for the atypical AVNRT, typical AVNRT and AVRT, respectively (p = 0.03). There was significant difference in the size of the CS from the ostium until 15 mm into the CS between 1) typical AVNRT and AVRT, 2) typical AVNRT and atypical AVNRT. Typical and atypical AVNRT patients had more windsock morphology CS (13/32, 40.6% and 10/32, 31.2%) compared to AVRT which had only one (1/32, 3.1%) windsock morphology (p = 0.002). CONCLUSION: The easier CS cannulation in patients with typical AVNRT could be due to a bigger CS size and to a more windsock morphology. The CS size and morphology may be a very important substrate of tachycardia in patients with AVNRT.

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.

Effects of right bundle branch block during atrioventricular nodal reentrant tachycardia.

BACKGROUND: The significant role of bundle branch block during atrioventricular nodal reentrant tachycardia (AVNRT) is not clear. The purposes of this study were to study the effects of complete right bundle branch block (RBBB) on electrophysiological parameters during AVNRT and to define the significance of complete RBBB during AVNRT. METHODS AND RESULTS: According to characteristics of electrocardiogram during sinus rhythm and AVNRT, 50 patients who underwent catheter ablation for slow-fast AVNRT were divided into three groups. Group I included 20 patients who had narrow QRS (< or = 110 ms) during sinus rhythm and AVNRT. Group II included 18 patients who had persistent RBBB (< or = 120 ms) during sinus rhythm and AVNRT. Group III included 12 patients who had narrow QRS during sinus rhythm, but they had narrow QRS and transient RBBB during AVNRT. The atrio-His (AH) interval (296+/-60 vs. 288+/-75 ms), His-ventricular (HV) interval (36+/-11 vs. 35+/-11 ms), His-atrial (HA) interval (72+/-24 vs. 71+/-28 ms), VA(HRA) interval (defined as the interval between the onset of ventricular depolarization and the onset of atrial activity of right high atrium; 34+/-24 vs. 37+/-25 ms), VA(CSO) interval (defined as the interval between the onset of ventricular depolarization and the onset of atrial activity of coronary sinus ostium; 13+/-28 vs. 26+/-23 ms) and tachycardia cycle length (TCL; 368+/-67 vs. 359+/-73 ms) during AVNRT were similar between group I and group II (all P > 0.05). In group III, the AH interval (255+/-81 vs. 246+/-83 ms), HV interval (44+/-5 vs. 42+/-11 ms), HA interval (66+/-19 vs. 70+/-15 ms), VA(HRA) interval (27+/-15 vs. 29+/-16 ms), VA(CSO) interval (23+/-25 vs. 21+/-25 ms) and TCL (322+/-76 vs. 316+/-77 ms) were not significantly different between AVNRT with narrow QRS and those with transient RBBB (all P > 0.05). CONCLUSIONS: Persistent RBBB and transient RBBB have no significant effects on the electrophysiological parameters during AVNRT. These findings suggest that RBBB might not influence the conduction of lower common pathway or the circuit of AVNRT.

The electrophysiologic characteristics in patients with only ventricular-pacing inducible slow-fast form atrioventricular nodal reentrant tachycardia.

BACKGROUND: Atrioventricular nodal reentrant tachycardia (AVNRT) can be usually induced by atrial pacing or extrastimulation. However, it is less commonly induced only by ventricular pacing or extrastimulation. OBJECTIVE: The purpose of this retrospective study was to investigate the electrophysiologic characteristics in patients with slow-fast form AVNRT that could be induced only by ventricular pacing or extrastimulation. METHODS: The total population was 1497 patients associated with AVNRT. There were 1373 (91.7%) patients who had slow-fast form AVNRT included in our study. Group 1 (n = 45) could be induced only by ventricular pacing or extrastimulation, and Group 2 (n = 1328) could be induced by only atrial stimulation or both atrial and ventricular stimulation. The electrophysiologic characteristics of the group 1 and group 2 patients were compared. RESULTS: Group 1 patients had a significantly lower incidence of both antegrade and retrograde dual AV nodal pathways. The pacing cycle length (CL) of the antegrade 1:1 fast pathway (FP) and antegrade ERP of the FP were both significantly shorter in Group 1 patients. Mean antegrade FRP of the fast and slow pathways were significantly shorter in Group 1 patients. The differences of pacing CL of 1:1 antegrade conduction, antegrade ERP and FRP were much longer in Group 2 patients. CONCLUSION: This study demonstrated the patients with slow-fast form AVNRT that could be induced only by ventricular stimulation had a lower incidence of dual AV nodal pathways and the different electrophysiologic characteristics (shorter pacing CL of the antegrade 1:1 FP, antegrade ERP of the FP and the differences of pacing CL of 1:1 antegrade conduction, antegrade ERP and FRP) from the other patients. The specific electrophysiologic characteristics in such patients could be the reason that could be induced only by ventricular stimulation.

Electrophysiological mechanisms and catheter ablation of complex atrial arrhythmias from crista terminalis:.

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.

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

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

Characteristics of virtual unipolar electrograms for detecting isthmus block during radiofrequency ablation of typical atrial flutter.

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.

Functional characterization of the crista terminalis in patients with atrial flutter: implications for radiofrequency ablation.

OBJECTIVES: The 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. BACKGROUND: The CT is a posterior barrier during typical AFL. However, the CT has transverse conduction capabilities in patients with upper loop re-entry (ULR). METHODS: Twenty-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 (CV(L)) and transverse (CV(T)) conduction velocity along and across the CT were measured. The width of the CT conduction gap was evaluated to guide radiofrequency ablation (RFA). RESULTS: No 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, CV(L) was greater than CV(T) (1.28 +/- 0.43 vs. 0.73 +/- 0.30 m/s, p < 0.001). The CV(L)/CV(T) 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. CONCLUSIONS: Most 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.

High-resolution mapping around the crista terminalis during typical atrial flutter: new insights into mechanisms.

INTRODUCTION: The aim of this study was to delineate activation patterns around the crista terminalis (CT) using high-resolution noncontact mapping. METHODS AND RESULTS: Twenty-six patients with typical atrial flutter (20 counterclockwise and 6 clockwise) were enrolled in the study. A noncontact mapping system was used to map atrial flutter. There were three activation patterns around the line(s) of block. Type I (n = 6) showed activation around a single complete line of block located in the CT. Type II (n = 17) showed activation around a single incomplete line of block with a conduction gap in the CT. Type III (n = 3) showed activation around double lines of block, one located in the CT and the other located in the sinus venosa region. Simultaneous activation around the tricuspid annulus and through the CT gap could result in double loop reentry (n = 12). After successful ablation of the cavotricuspid isthmus (CTI) in 24 patients, upper loop reentry was still induced in 12 patients with double loop reentry. Subsequent ablation of the CT gap was performed successfully in these 12 patients, and no arrhythmia was inducible thereafter. During the follow-up period of 8.4 +/- 4.1 months, there was no recurrence of atrial flutter in any patient. CONCLUSION: During typical atrial flutter, the CT might be an incomplete barrier. Simultaneous conduction through the CTI and CT gap could result in double loop reentry. Radiofrequency ablation of the CTI and CT gap was effective in eliminating this arrhythmia.

Focal atrial tachycardia: new insight from noncontact mapping and catheter ablation.

BACKGROUND: This study investigated the electrophysiologic characteristics, atrial activation pattern, and effects of radiofrequency (RF) catheter ablation guided by noncontact mapping system in patients with focal atrial tachycardia (AT). METHODS AND RESULTS: In 13 patients with 14 focal ATs, noncontact mapping system was used to map and guide ablation of AT. AT origins were in the crista terminalis (n=8), right atrial (RA) free wall (n=3), Koch triangle (n=1), anterior portion of RA-inferior vena cava junction (n=1), and superior portion of tricuspid annulus (n=1); breakout sites were in the crista terminalis (n=5), RA free wall (n=5), middle cavotricuspid isthmus (n=2), and RA-superior vena cava junction (n=2). ATs arose from the focal origins (11 ATs inside or at the border of low-voltage zone), with preferential conduction, breakout, and spread to the whole atrium. After applications of RF energy on the earliest activation site or the proximal portion of preferential conduction from AT origin, 13 ATs were eliminated without complication. During the follow-up period (8+/-5 months), 11 (91.7%) of the 12 patients with successful ablation were free of focal ATs. CONCLUSIONS: Focal AT originates from a small area and spreads out to the whole atrium through a preferential conduction. Application of RF energy guided by noncontact mapping system was effective and safe in eliminating focal AT.

Effects of a blocked atrial beat on the atrioventricular nodal recovery property in patients with dual nodal pathways.

Dual AVN physiology can be demonstrated by a variety of maneuvers. To determine whether AVN recovery times following a blocked extrastimulus facilitate or obscure detection of dual AVN physiology, 11 patients (9-17 years) were studied with dual AVN pathways by using single and double atrial extrastimuli. With a single atrial extrastimuli, the premature atrial stimulus (A2) was coupled to basic atrial beats (A1). The fast and slow AVN recovery curves were constructed with plots of the nodal conduction time against the recovery time (A1A2,A2H2). With double atrial extrastimuli, a fixed blocked A2 beat (A2B) was followed by a scanning atrial beat (A3). The nodal recovery property post-A2B was studied by plots of A2BA3,A3H3. In all patients the recovery curve of the fast pathway post-A2B had a leftward shift when compared to that of the pre-A2B curve (i.e., the AH was shortened at the same recovery time). The window of slow pathway conduction post-A2B disappeared totally in five patients and decreased significantly in six patients (post-A2B: 26 +/- 42 ms; pre-A2B: 80 +/- 65 ms, P < 0.05). In the six patients that still had slow pathway conduction post-A2B, the slow pathway effective refractory period post-A2B was significantly less than that of pre-A2B (215 +/- 38 vs 268 +/- 16 ms, P < 0.05). The fast pathway effective refractory period post-A2B was also diminished significantly (235 +/- 62 vs 357 +/- 76 ms, P < 0.0001). The authors conclude that blocked atrial beats decrease the visibility of the slow pathway conduction.