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.

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.

Predictors of early and late recurrence of atrial fibrillation after catheter ablation of paroxysmal atrial fibrillation.

INTRODUCTION: The outcome of patients with early recurrence of atrial fibrillation (AF) (within one month) after ablation procedure is controversial. Furthermore, the predictors of early and late (up to mean follow-up 30 months) recurrence of AF are not investigated in depth. AIMS OF THE STUDY: The aim of the present study was to investigate the predictors of early and late recurrence of AF after catheter ablation of arrhythmogenic foci initiating AF in patients with paroxysmal AF. METHODS AND RESULTS: The study included 207 patients (155 men; mean age 62 +/- 13 years) who received catheter ablation of paroxysmal AF. Eighty-one (39%) patients had early recurrence of AF. Five clinical variables were related to the early recurrence of AF: (1) old age (>/=65 years) ( P = 0.004); (2) presence of associated cardiovascular disease ( P = 0.01); (3) presence of multiple AF foci ( P = 0.004); (4) presence of AF foci from left atrial free wall ( P = 0.039); (5) left atrial enlargement ( P = 0.038). Multivariate analysis demonstrated that presence of multiple AF foci could predict early recurrence of AF ( P = 0.013; ratio = 2.24; 95% CI 1.18 to 4.25). During the follow-up period (30 +/- 11 months), 70 (34%) patients had late recurrence of AF, and two clinical variables were related to the late recurrence of AF: (1) presence of early recurrence of AF ( P = 0.025); (2) presence of multiple AF foci ( P = 0.034). Multivariate analysis found that presence of early recurrence of AF could predict late recurrence of AF ( P = 0.046; hazard ratio = 1.62; 95% CI 1.01 to 2.59). Late recurrence of AF happened in 35 (43%) of the 81 patients with early recurrence of AF, and in 35 (28%) of the 126 patients without early recurrence of AF. CONCLUSIONS: Early AF recurrence could predict late AF recurrence.

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.

Spontaneous transition of 2:1 atrioventricular block to 1:1 atrioventricular conduction during atrioventricular nodal reentrant tachycardia: evidence supporting the intra-Hisian or infra-Hisian area as the site of block.

INTRODUCTION: The incidence of spontaneous transition of 2:1 AV block to 1:1 AV conduction during AV nodal reentrant tachycardia has not been well reported. Among previous studies, controversy also existed about the site of the 2:1 AV block during AV nodal reentrant tachycardia. METHODS AND RESULTS: In patients with 2:1 AV block during AV nodal reentrant tachycardia, the incidence of spontaneous transition of 2:1 AV block to 1:1 AV conduction and change of electrophysiologic properties during spontaneous transition were analyzed. Among the 20 patients with 2:1 AV block during AV nodal reentrant tachycardia, a His-bundle potential was absent in blocked beats during 2:1 AV block in 8 patients, and the maximal amplitude of the His-bundle potential in the blocked beats was the same as that in the conducted beats in 4 patients and was significantly smaller than that in the conducted beats in 8 patients (0.49 +/- 0.25 mV vs 0.16 +/- 0.07 mV, P = 0.007). Spontaneous transition of 2:1 AV block to 1:1 AV conduction occurred in 15 (75%) of 20 patients with 2:1 AV block during AV nodal reentrant tachycardia. Spontaneous transition of 2:1 AV block to 1:1 AV conduction was associated with transient right and/or left bundle branch block. The 1:1 AV conduction with transient bundle branch block was associated with significant His-ventricular (HV) interval prolongation (66 +/- 19 ms) compared with 2:1 AV block (44 +/- 6 ms, P < 0.01) and 1:1 AV conduction without bundle branch block (43 +/- 6 ms, P < 0.01). CONCLUSION: The 2:1 AV block during AV nodal reentrant tachycardia is functional; the level of block is demonstrated to be within or below the His bundle in a majority of patients with 2:1 AV block during AV nodal reentrant tachycardia, and a minority are possibly high in the junction between the AV node and His bundle.

Use of fluoroscopic views for detecting Marshall's vein in patients with cardiac arrhythmias.

INTRODUCTION: Recently, several studies showed that focal atrial fibrillation (AF) can be initiated by ectopic beats from the vein of Marshall (VOM). However, the incidence and best fluoroscopic views of VOM have never been reported. METHODS AND RESULTS: 106 patients (Non-AF = 52, AF = 54) underwent balloon-occluded coronary sinus angiography using seven fluoroscopic views (PA, Lateral, RAO 30 degrees, RA 30 degrees + Caudal 20 degrees, LAO 30 degrees, LAO 60 degrees, LAO 60 degrees + Cranial 20 degrees ). The total incidence of VOM was 74.5% (79/106), without significant difference in age (81.1 vs. 71.0%, >65 vs.

Clinical outcome of very late recurrence of atrial fibrillation after catheter ablation of paroxysmal atrial fibrillation.

INTRODUCTION: High recurrence rate is still a major problem associated with ablation of paroxysmal atrial fibrillation (AF). Most of the recurrences occur within 6 months after ablation. The characteristics of very late recurrent AF (>12 months after ablation) have not been reported. METHODS AND RESULTS: Two hundred seven patients with drug-refractory AF underwent successful focal ablation or isolation of AF foci. After the first ablation procedure, Holter monitoring and event recorders were used to evaluate symptomatic recurrent AF. A second ablation procedure was recommended if the antiarrhythmic drugs could not control recurrent AF. During long-term follow-up (mean 30 +/- 11 months, up to 51 months), 70 patients had recurrent AF, including 13 patients (6%) with very late (>12 months) recurrent AF (group 1) and 57 patients (28%) with late (within 12 months after ablation) recurrent AF (group 2). Group 1 patients had a significantly lower incidence of multiple (> or = 2) AF foci (23% vs 63%, P = 0.02) than group 2 patients. In addition, the incidence of antiarrhythmic drugs use (38% vs 84%, P = 0.001) to maintain sinus rhythm after the first episode of recurrent AF was significantly lower in group 1 than group 2 patients, and the incidence of a second intervention procedure (8% vs 35%, P = 0.051) tended to be lower in group 1 than group 2 patients. CONCLUSION: The incidence of very late recurrent AF after ablation of paroxysmal AF is very low, and the clinical outcome of patients with very late recurrent AF is benign.

Catheter ablation of paroxysmal atrial fibrillation initiated by non-pulmonary vein ectopy.

BACKGROUND: Most of the ectopic beats initiating paroxysmal atrial fibrillation (PAF) originate from the pulmonary vein (PV). However, only limited data are available on PAF originating from the non-PV areas. METHODS AND RESULTS: Two hundred forty patients with a total of 358 ectopic foci initiating PAF were included. Sixty-eight (28%) patients had AF initiated by ectopic beats (73 foci, 20%) from the non-PV areas, including the left atrial posterior free wall (28, 38.3%), superior vena cava (27, 37.0%), crista terminalis (10, 3.7%), ligament of Marshall (6, 8.2%), coronary sinus ostium (1, 1.4%), and interatrial septum (1, 1.4%). Catheter ablation eliminated AF with acute success rates of 63%, 96%, 100%, 50%, 100%, and 0% in left atrial posterior free wall, superior vena cava, crista terminalis, ligament of Marshall, coronary sinus ostium, and interatrial septum, respectively. During a follow-up period of 22+/-11 months, 43 patients (63.2%) were free of antiarrhythmic drugs without AF recurrence. CONCLUSIONS: Ectopic beats initiating PAF can originate from the non-PV areas, and catheter ablation of the non-PV ectopy has a moderate efficacy in treatment of PAF.

Novel concept of atrial tachyarrhythmias originating from the superior vena cava: insight from noncontact mapping.

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.

Double potential interval and transisthmus conduction time for prediction of cavotricuspid isthmus block after ablation of typical atrial flutter.

BACKGROUND: Complete bi-directional isthmus block is the endpoint of typical atrial flutter ablation. The purpose of this study was to investigate the feasibility of the local double potential (DP) interval and the change in transisthmus conduction time for predicting complete isthmus block after ablation of the cavotricuspid isthmus. METHODS: The study population consisted of 32 patients with typical atrial flutter after a procedure of radiofrequency (RF) ablation of the cavotricuspid isthmus (16 had incomplete block and 16 had complete block). The transisthmus conduction time was determined during pacing from the proximal coronary sinus and low lateral right atrium before and after RF ablation. The DP interval close to the ablation line was evaluated after final RF energy application. RESULTS: In the counterclockwise direction, transisthmus conduction time had an increase of 37 +/- 25.4% and 127.3 +/- 35.5% (P < 0.001), and the DP interval was 63.3 +/- 8.7 ms and 120 +/- 17.4 ms (P < 0.001) after achievement of incomplete and complete block, respectively. The sensitivity, specificity, positive and negative predictive values of an increase in the transisthmus conduction time > or =50% were 100%, 81%, 84% and 100%, respectively; those of DP interval > or =100 ms were 100%. In the clockwise direction, transisthmus conduction time had an increase of 38.8 +/- 28.6% and 135.7 +/- 63.6% (P < 0.001), and the DP interval was 63.6 +/- 13.8 ms and 127.7 +/- 27.1 ms (P < 0.001) after achievement of incomplete and complete block, respectively. The sensitivity, specificity, positive and negative predictive values of an increase in the transisthmus conduction time > or =50% were 100%, 67%, 83% and 100%, respectively; those of the DP interval > or =100 ms were 100%. CONCLUSIONS: The transisthmus conduction time > or =50% increase or DP interval > or =100 ms was feasible to predict complete bi-directional isthmus block.

Determinants of successful ablation of idiopathic ventricular tachycardias with left bundle branch block morphology from the right ventricular outflow tract.

The aim of the study was to define the factors that may predict the outcomes of radiofrequency ablation from the right ventricular outflow tract (RVOT) in patients with idiopathic VT with a QRS morphology of LBBB. Endocardial mapping and RF ablation from the RVOT were performed in 35 patients (14 men, mean age 41 +/- 14 years), and VT was successfully ablated in 30 patients. There was no significant difference with regard to clinical characteristics and electrophysiological findings between patients with successful and failed ablation. The VTs with successful ablation showed an rS (n = 16) or QS (n = 14) pattern in lead V1, and all five VTs with failed ablation showed an rS pattern in lead V1. Although the absence of an R wave in lead V1 did not differ between patients with successful and failed ablation (P = 0.13), the absence of an R wave in lead V1 predicted VT successfully ablated from the RVOT (positive predictive value 100%; negative predictive value 24%). The VTs with successful ablation had a median precordial transitional zone at lead V4 (range V3-V6), whereas all five VTs with failed ablation had precordial transition zones at lead V3 (P = 0.004). Furthermore, a presence of an R wave in lead V1 associated with a precordial transition zone at lead V3 predicted VT not successfully ablated from the RVOT (positive predictive value 100%; negative predictive value 100%). In conclusion, some VTs with LBBB and inferior or normal axis cannot be ablated from the RVOT. The presence of an R wave in lead V1 associated with a precordial transition zone at lead V3 suggest that some VTs may not arise from the RVOT.

Noncontact three-dimensional mapping and ablation of upper loop re-entry originating in the right atrium.

OBJECTIVES: This study was aimed at delineating the reentrant circuit of right atrial (RA) upper loop re-entry using noncontact three-dimensional mapping. BACKGROUND: Various forms of atypical atrial flutter including lower loop re-entry and left atrial flutter have been demonstrated. However, little is known about upper loop re-entry in the RA. METHODS: The study population consisted of eight patients (65 +/- 12 years, seven men) with atypical atrial flutter. Right atrial activation during atrial flutter was visualized using a noncontact mapping system (EnSite-3000 with Clarity Software, St. Paul, Minnesota) for a three-dimensional reconstruction of the endocardial depolarization. The narrowest part of the re-entrant circuit was targeted using radiofrequency catheter ablation. RESULTS: Noncontact mapping showed macro-re-entry confined to the RA free wall with RA activation time accounting for 100% of the cycle length (214 +/- 21 ms) in all eight patients. Two patients had counterclockwise activation, and six patients had clockwise activation around the central obstacle, which was composed of the crista terminalis, the area of functional block, and superior vena cava. The lower turn-around points were located at the conduction gap in the crista terminalis. Radiofrequency linear ablation of the conduction gap in the crista terminalis was performed and eliminated atrial flutter in six patients without recurrence during a follow-up of 3.2 +/- 1.1 months. CONCLUSIONS: Atypical atrial flutter could arise from upper loop re-entry in the RA with conduction through the gap in the crista terminalis. Radiofrequency linear ablation of the conduction gap was effective in eliminating this atrial arrhythmia.