Complex electrophysiological characteristics in atrioventricular nodal reentrant tachycardia with continuous atrioventricular node function curves

BACKGROUND

Although typical atrioventricular nodal reentrant tachycardia (AVNRT) with discontinuous AV node function curves has been well studied, there has been a lack of any significant information about AVNRT without evidence of dual AV nodal pathway physiology during atrial extrastimulus testing or atrial pacing.

METHODS AND RESULTS

Group 1 included 9 patients with continuous curves during atrial extrastimulus testing but without a jump (> or = 50 ms) of the atrial-His bundle (AH) interval during incremental atrial pacing. The maximal AH interval during atrial pacing (266 +/- 61 versus 168 +/- 27 ms, P = .007) or extrastimulus testing (290 +/- 60 versus 176 +/- 18 ms, P = .005) shortened significantly after ablation. Antegrade and retrograde AV node properties were similar before and after ablation. Group 2 included 14 patients with continuous curves and a jump of the AH interval during incremental atrial pacing. The atrial pacing cycle length with 1:1 AV conduction and effective refractory period (ERP) of the antegrade AV node increased significantly, whereas the maximal AH interval during atrial pacing (358 +/- 70 versus 203 +/- 28 ms, P = .001) or extrastimulus testing (338 +/- 75 versus 196 +/- 34 ms, P = .002) shortened significantly after ablation. Group 3 included 24 patients with discontinuous curves. The maximal AH interval during atrial pacing or extrastimulus testing and the ERP of the antegrade fast AV node shortened, whereas the ERP of the antegrade AV node increased significantly after ablation. The maximal AH interval before ablation, extent of decrease in maximal AH interval after ablation, ERP of the retrograde AV node before ablation, and tachycardia cycle length were significantly shorter in group 1 than groups 2 and 3.

CONCLUSIONS

In AVNRT with continuous AV node function curves, dual AV nodal pathway physiology may or may not be demonstrated during atrial pacing. Significant shortening of the maximal AH interval during atrial pacing after radiofrequency ablation suggests successful elimination of AVNRT.

Electrophysiologic characteristics and radiofrequency catheter ablation in atrioventricular node reentrant tachycardia with second-degree atrioventricular block

INTRODUCTION

Detailed electrophysiologic study of AV nodal reentrant tachycardia (AVNRT) with 2:1 AV block has been limited.

METHODS AND RESULTS

Six hundred nine consecutive patients with AVNRT underwent electrophysiologic study and radiofrequency catheter ablation of the slow pathway. Twenty-six patients with 2:1 AV block during AVNRT were designated as group I, and those without this particular finding were designated as group II. The major findings of the present study were: (1) group I patients had better anterograde and retrograde AV nodal function, shorter tachycardia cycle length (during tachycardia with 1:1 conduction) (307 +/- 30 vs 360 +/- 58 msec, P < 0.001), and higher incidence of transient bundle branch block during tachycardia (18/26 vs 43/609, P < 0.001) than group II patients; (2) 21 (80.8%) group I patients had alternans of AA intervals during AVNRT with 2:1 AV block. Longer AH intervals (264 +/- 26 vs 253 +/- 27 msec, P = 0.031) were associated with the blocked beats. However, similar HA intervals (51 +/- 12 vs 50 +/- 12 msec, P = 0.363) and similar HV intervals (53 +/- 11 vs 52 +/- 12, P = 0.834) were found in the blocked and conducted beats; (3) ventricular extrastimulation before or during the His-bundle refractory period bundle could convert 2:1 AV block to 1:1 AV conduction.

CONCLUSIONS

Fast reentrant circuit, rather than underlying impaired conduction of the distal AV node or infranodal area, might account for second-degree AV block during AVNRT. Slow pathway ablation is safe and effective in patients who have AVNRT with 2:1 AV block.

Results of radiofrequency ablation in patients with clinically documented, but noninducible, atrioventricular node reentrant tachycardia and orthodromic atrioventricular reciprocating tachycardia

Among 1,281 patients with symptomatic supraventricular tachycardia, 34 patients (2.7%) with presumed diagnosis of atrioventricular node reentrant tachycardia and orthodromic atrioventricular reciprocating tachycardia did not have inducible tachycardia in the electrophysiologic laboratory. Application of radiofrequency energy to the presumed arrhythmogenic sites could achieve a high success rate, with a low recurrence rate in these patients.

Effect of high intensity drive train stimulation on dispersion of atrial refractoriness: role of autonomic nervous system

OBJECTIVES

This study evaluated the effect of high intensity drive train (S1) stimulation on the atrial effective refractory period (ERP) and its relation to the autonomic nervous system.

BACKGROUND

High intensity S1 stimulation was demonstrated to shorten the ventricular ERP and to increase dispersion of refractoriness. These effects may be due to local release of neurotransmitters. The response of the atrium and ventricle to neurotransmitters was different. The effects of high intensity S1 stimulation at the atrial tissue were evaluated.

METHODS

Forty patients without structural heart disease were studied. In group 1, 20 patients, the atrial ERP was measured at 0, 7, 14, 21 and 28 mm away from the S1 site under both twice diastolic threshold and high intensity (10 mA) S1 stimulation. The same protocol was repeated after sequential administration of propranolol (0.2 mg/kg body weight) and atropine (0.04 mg/kg). In group 2, the other 20 patients, the atrial ERP was studied at three atrial sites (high lateral right atrium [HLRA], right posterior interatrial septum [RPS] and distal coronary sinus [DCS] with twice diastolic threshold and high intensity S1 stimulation at baseline and after sequential autonomic blockade. The three atrial sites were randomly assigned as the S1 location.

RESULTS

In group 1, high intensity S1 stimulation shortened the atrial effective refractory period most prominently at the site of S1: (mean +/- SD) 13.3 +/- 6.4% (p < 0.001), 8.1 +/- 3.8% (p < 0.001), 4.8 +/- 4.3% (p < 0.001), 3.7 +/- 4.7% (p < 0.001) and 0.5 +/- 2.6% at 0, 7, 14, 21 and 28 mm from the S1 site, respectively. The effect of high intensity S1 stimulation was blunted with propranolol and autonomic blockade but persisted after atropine alone. High intensity S1 stimulation also increased dispersion of refractoriness (from 23 +/- 11 ms to 31 +/- 12 ms, p = 0.01), which was eliminated with autonomic blockade. In group 2, high intensity S1 stimulation had similar effects at different locations (ERP shortening of 10.8 +/- 2.7%, 10.8 +/- 2.2% and 12.2 +/- 4.6% at the HLRA, RPS and DCS, respectively). The responses to sequential autonomic blockade were similar to those in group 1. However, high intensity S1 stimulation at HLRA increased dispersion of refractoriness, but at DCS it reduced dispersion of refractoriness.

CONCLUSIONS

High intensity S1 stimulation led to local shortening of the atrial ERP and increased dispersion of refractoriness. These effects were blunted with propranolol and autonomic blockade. High intensity S1 stimulation at the HLRA increased dispersion of atrial refractoriness, whereas the same stimulation at the DCS decreased dispersion of atrial refractoriness.

Electrophysiologic characteristics and radiofrequency catheter ablation of fast-slow form atrioventricular nodal reentrant tachycardia

This study demonstrates that the fast-slow form of atrioventricular nodal reentrant tachycardia is usually catecholamine-sensitive and its electrophysiologic characteristics are significantly different from those of the slow-fast form. However, radiofrequency catheter ablation is a safe and effective treatment for patients with the fast-slow form of atrioventricular nodal reentrant tachycardia.

Radiofrequency catheter ablation of slow pathway in 760 patients with atrioventricular nodal reentrant tachycardia--long-term results

BACKGROUND

Although selective radiofrequency catheter ablation of the slow atrioventricular (AV) nodal pathway has provided a curative therapy for patients with AV nodal reentrant tachycardia, information about the long-term result of radiofrequency catheter ablation in patients with different types of AV nodal reentrant tachycardia was not available. This study was to investigate the long-term effect of selective slow pathway ablation in a large group of consecutive patients with AV nodal reentrant tachycardia.

METHODS

From December 1990 to June 1996, 760 consecutive patients with clinically documented AV nodal reentrant tachycardia received radiofrequency catheter ablation of antegrade and/or retrograde slow AV nodal pathway at this electrophysiologic laboratory. The data of electrophysiologic characteristics and long-term follow-up were collected. The success rate, complication rate and recurrence rate were analyzed.

RESULTS

There were 669 slow-fast form AV nodal reentrant tachycardia, 27 fast-slow form AV nodal reentrant tachycardia, 13 variant form AV nodal reentrant tachycardia, and 51 multiple forms of AV nodal reentrant tachycardia. The electrophysiologic characteristics were different among these four groups. However, radiofrequency catheter ablation attained a 99% success rate in all the four groups with different types of tachycardia. There were 5 accidental injuries to AV conduction. Three of the 5 patients needed implantation of pacemakers. During the follow-up period, there were 14 (1.8%) recurrence of AV nodal reentrant tachycardia. All of the 14 patients had a successful second ablation without recurrence.

CONCLUSIONS

This study demonstrated that radiofrequency catheter ablation of slow pathway was a highly effective treatment modality for patients with various types of AV nodal reentrant tachycardia. Furthermore, the incidence of complication rate and recurrence rate were low in an experienced center.

Long-term results of radiofrequency catheter ablation in patients with Wolff-Parkinson-White syndrome

BACKGROUND

Information about the long-term results of radiofrequency catheter ablation, electrophysiologic characteristics of differently located accessory pathways, and the difference between a single accessory pathway and multiple accessory pathways was limited.

METHODS

Nine hundred and thirty-one patients with 1016 accessory pathways (APs) received electrophysiologic study and radiofrequency catheter ablation between July 1, 1989 and June 31, 1996. Group 1 included 856 (91.9%) patients with a single AP and Group 2 included 75 (8.1%) patients with multiple APs. The follow-up period was 48 +/- 37 months (range, 2 to 84 months).

RESULTS

Nine hundred and thirteen patients (98.1%) had successful ablation with a complication rate of 1.5%. In Group 1, left free wall pathways were ablated with fewer radiofrequency pulses, shorter procedure time, shorter radiation exposure time and a lower recurrence rate than those at other locations. Comparisons between Group 1 and Group 2 showed that the latter had higher incidences of antidromic tachycardia (3% vs 13%, p < 0.05) and atrial flutter/fibrillation (26% vs 37%, p < 0.05). Regarding radiofrequency catheter ablation, Group 2 needed more radiofrequency pulses (8.7 +/- 7.8 vs 5.5 +/- 7.7, p < 0.001), longer procedure time (3.3 +/- 1.4 vs 2.1 +/- 1.0 hours, p < 0.05) and radiation time (49 +/- 27 vs 29 +/- 19 minutes, p < 0.001), and a higher recurrence rate (10.6% vs 3.3%, p < 0.005) than those in Group 1. Thirty-six patients (4%) with recurrence had more right-side pathways than those without recurrence. In addition, difficult ablation (longer procedure time, longer radiation time and more radiofrequency pulses) was associated with a higher recurrence rate.

CONCLUSIONS

These findings demonstrated that a high success rate with a low recurrence and low complication rate of radiofrequency catheter ablation could be achieved in a large population with APs during a long follow-up period.

A new electrocardiographic algorithm using retrograde P waves for differentiating atrioventricular node reentrant tachycardia from atrioventricular reciprocating tachycardia mediated by concealed accessory pathway

OBJECTIVES

The purpose of this study was to use an electrocardiographic (ECG) algorithm, derived from the results of radiofrequency ablation, to discriminate atrioventricular node reentrant tachycardia (AVNRT) from atrioventricular reciprocating tachycardia (AVRT) and to localize a concealed accessory pathway, prospectively.

BACKGROUND

Information about ECG criteria for differentiating AVNRT from AVRT is limited and has not been confirmed by surgical or catheter ablation.

METHODS

Four hundred six ECGs (obtained from 406 different patients) that demonstrated narrow QRS complex (< 0.12 s) supraventricular tachycardia with an RP' interval less than the P'R interval or pseudo r' wave in lead V1 or pseudo S wave in inferior leads, or both, were examined, and the results were confirmed by radiofrequency catheter ablation. The initial 226 ECGs were analyzed to develop a stepwise algorithm, and the subsequent 180 ECGs were prospectively evaluated by the new algorithm.

RESULTS

The presence of a pseudo r' wave in lead V1 or a pseudo S wave in leads II, III, aVF indicated anterior-type AVNRT with an accuracy of 100%. With the difference of RP' intervals in leads V1 and III > 20 ms, posterior-type AVNRT could be differentiated from AVRT utilizing a posteroseptal pathway with a sensitivity of 71% (95% confidence interval [CI] 55% to 89%), a specificity of 87% (95% CI 67% to 97%) and a positive predictive value of 75% (95% CI 56% to 91%). According to the polarity of retrograde P waves in leads V1, II, III, aVF and I during AVRT, the concealed accessory pathway could be localized to one of the nine regions on the atrioventricular annuli with an accuracy of 75% (for a right midseptal pathway) to 93.8% (for a left posterior pathway). Overall, the new algorithm had an accuracy of 97.8% in discriminating AVNRT from AVRT and 88.1% in localizing a concealed accessory pathway, prospectively. Prediction was incorrect in only 15 patients (9.1%).

CONCLUSIONS

The new ECG algorithm derived from the analysis of retrograde P waves during tachycardia could provide a criterion for differential diagnosis between AVNRT and AVRT and for predicting the location of concealed accessory pathways.

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

INTRODUCTION

Although the mechanism and radiofrequency catheter ablation of counterclockwise (typical) atrial flutter have been studied extensively, information about the electrocardiographic and electrophysiologic characteristics and effects of radiofrequency ablation in patients with clockwise atrial flutter is limited.

METHODS AND RESULTS

Thirty consecutive patients with clinically documented paroxysmal clockwise atrial flutter were studied. Endocardial recordings and entrainment study using a "halo" catheter with 10 electrode pairs in the right atrium were performed. Radiofrequency energy was applied to the inferior vena cava-tricuspid annulus (IVC-TA) and/or coronary sinus ostium-tricuspid annulus (CSO-TA) isthmus to evaluate the effects of linear catheter ablation. Eighteen patients had both counterclockwise and clockwise atrial flutters, and 12 patients had only clockwise atrial flutter. Both forms of atrial flutter had similar flutter cycle lengths (232 +/- 30 vs 226 +/- 25 msec, P = 0.526) but reverse activation sequences. Right atrial pacing at a cycle length 20 msec shorter than the flutter cycle length from the CSO-TA isthmus, IVC-TA isthmus, and the area between the two isthmuses revealed concealed entrainment with stimulus-to-P wave intervals of 32 +/- 19, 95 +/- 14, and 50 +/- 17 msec (P = 0.022) in the counterclockwise form, and 110 +/- 12, 40 +/- 20, and 60 +/- 15 msec (P = 0.018) in the clockwise form. In clockwise atrial flutter, 20 patients with biphasic P waves in the inferior leads had the presumed exit site of slow conduction area located at the low posterolateral right atrium; 10 patients with positive P waves in the inferior leads had the presumed exit site located at the mid-high posterolateral right atrium. Among the 18 patients with both forms of atrial flutter, linear ablation lesions directed at the IVC-TA isthmus eliminated both forms of atrial flutter in 14 patients; in the remaining 4 patients, CSO-TA linear lesions eliminated the counterclockwise form and IVC-TA lesions eliminated the clockwise form. Among the 12 patients with the clockwise form only, CSO-TA linear lesions eliminated flutter in 2 and IVC-TA linear lesions eliminated flutter in 10 patients. Successful ablation was confirmed by creation of bidirectional conduction block in the IVC-TA and/or CSO-TA isthmus during pacing from the proximal coronary sinus and right posterolateral atrium sandwiching the linear lesions. During the follow-up period of 17 +/- 8 months, 2 patients had recurrence of clockwise atrial flutter, 1 patient had new onset of atypical atrial flutter, and 2 patients had new onset of atrial fibrillation.

CONCLUSIONS

Counterclockwise and clockwise atrial flutters may have overlapping slow conduction areas with different exit sites. Radiofrequency catheter ablation using the linear method directed at the IVC-TA and CSO-TA isthmuses was feasible and effective in treating both forms of atrial flutter.

Accessory atrioventricular pathways with only antegrade conduction in patients with symptomatic Wolff-Parkinson-White syndrome. Clinical features, electrophysiological characteristics and response to radiofrequency catheter ablation

Information about accessory pathways conducting only in the antegrade direction is limited. The purposes of the present study were to prospectively investigate the clinical features, electrophysiological characteristics, effects of radiofrequency catheter ablation and recurrent atrial fibrillation after successful ablation in patients with accessory pathways conducting only in the antegrade direction, and to compare them with those who had pathways capable of bidirectional conduction in a consecutive series of 759 patients. Electrophysiological studies and radiofrequency catheter ablation were performed in 33 study patients with antegrade-only accessory pathways and in 377 patients with bidirectional accessory pathways for comparison. The patients with accessory pathways conducting only in the antegrade direction were older (47 +/- 16 vs 40 +/- 16 years, P = 0.037) and had a higher incidence of atrial fibrillation (100% vs 27.1%, P < 0.001) as well as related syncope (33.3% vs 10.1%, P = 0.001). The study patients also had more accessory pathways located in the posterior septum and a higher incidence of retrograde atrioventricular nodal conduction. The biophysical variables, success and complication rates of radiofrequency ablation were similar in both groups. During the follow-up period of 32 +/- 12 months, symptomatic atrial fibrillation after successful ablation did not recur in 79% and 81% of patients with unidirectional and bidirectional accessory pathways, respectively. Furthermore, old age and cardiovascular diseases were independent predictors of recurrent atrial fibrillation after radiofrequency ablation. In conclusion, this study showed that atrial fibrillation with preexcitation was the usual presentation in patients who had symptomatic Wolff-Parkinson White syndrome with an antegrade-only accessory pathway, and might be related to antegrade conduction of the accessory pathway. Therefore elimination of antegrade-only and bidirectional pathways by radiofrequency ablation could prevent the recurrence of symptomatic atrial fibrillation in younger patients without cardiac disease.

Long-term results of radiofrequency catheter ablation in patients with multiple accessory pathways

Information on the long-term results of radiofrequency catheter ablation in a large group of patients with multiple accessory pathways (APs) was not available. This study included 858 patients with Wolff-Parkinson-White syndrome who underwent electrophysiologic study and radiofrequency catheter ablation: 73 patients (8.5%) had multiple APs. Sixty-six patients had 2 APs, 5 had 3 APs, 1 had 4 APs, and 1 had 5 APs. The most common combination pattern of these pathways were concealed APs (38 patients, 52%). Localization of accessory pathways showed a higher incidence of right free wall (22% vs 11%, p < 0.05), anteroseptal, and midseptal APs (9% vs 5%, p < 0.05) in patients with multiple APs than in patients with 1 AP. The most common anatomic sites for multiple APs were 2 APs in the left wall (21 patients, 28%). Although the success rate was similar (98% vs 99%, p > 0.05), procedure time (3.1 +/- 1.2 vs 2.0 +/- 1.1 hours, p < 0.05) and radiation exposure time (48 +/- 26 vs 29 +/- 19 minutes, p < 0.05) were longer in patients with multiple APs. The recurrence rate was higher in patients with multiple APs (9.5% vs 2.5%, p < 0.05), and the most common site of recurrent APs was in the left free wall (7.2%); in contrast, it was in the right free wall in patients with 1 AP. These findings demonstrated that a high success rate of radiofrequency catheter ablation was found in patients with multiple APs; however, the higher recurrence rate in patients with multiple APs should be considered.

Effects of isoproterenol in facilitating induction of slow-fast atrioventricular nodal reentrant tachycardia

This study demonstrates that patients with poorer conduction properties of the anterograde slow and retrograde fast pathways usually need isoproterenol to facilitate induction of atrioventricular nodal reentrant tachycardia. Isoproterenol infusion usually facilitates induction of tachycardia by enhancing the retrograde ventriculoatrial conduction.

Paradox of accessory pathway block after radiofrequency ablation in patients with the Wolff-Parkinson-White syndrome

Although pacing technique has demonstrated that the most common site of conduction block in a manifest accessory pathway (AP) was between the AP and the ventricle, most of the block sites have been found to be between the atrium and AP after successful radiofrequency ablation. Furthermore, the block site in a concealed AP after successful radiofrequency catheter ablation has not been reported in the literature, and comparisons between a manifest and concealed AP have not been performed. This study included 219 consecutive patients undergoing successful radiofrequency catheter ablation of a single AP. AP potential was recorded at the successful target site in 76 of 92 (82.6%) patients with manifest APs, and in 99 of 127 (77.9%) patients with concealed APs. All the left-sided APs (including left posteroseptal APs) were ablated by a ventricular approach, and right-sided APs (including anteromidseptal and right posteroseptal APs) were ablated by an atrial approach. The site of conduction block was determined by analyzing and comparing the local electrograms recorded before and after radiofrequency ablation at successful ablation sites. Conduction block of manifest APs was between the atrial-AP (A-AP) in 69 patients (75%) and between the AP-ventricle (AP-V) interface in 7 patients (7.6%), whereas the conduction block of concealed APs occurred between the AP-V in 90 patients (70.9%) and between the A-AP interface in 9 patients (7.1%). Neither the preablation electrogram nor electrophysiologic characteristics of APs predicted the site of conduction block. Furthermore, neither the location of the APs nor the position of the ablation catheter affected the block site. It was concluded that the most common site of conduction block during successful radiofrequency catheter ablation of a manifest and concealed AP was between the A-AP and AP-V interface, respectively, and the impedance mismatch theory explained only part of the findings.

Dimension and related anatomical distance of Koch's triangle in patients with atrioventricular nodal reentrant tachycardia

INTRODUCTION

The dimension of Koch's triangle in patients with AV nodal reentrant tachycardia has not been well described. Understanding the dimension and anatomical distance related to Koch's triangle might be useful in avoiding accidental AV block during ablation of the slow pathway. The purposes of this study were to define the dimension of Koch's triangle and its related anatomical distance and correlate these parameters with the successful ablation sites in patients with AV nodal reentrant tachycardia.

METHODS AND RESULTS

We studied 218 patients with AV nodal reentrant tachycardia. The distance between the presumed proximal His-bundle area and the base of the coronary sinus orifice (DHis-OS) measured in the right anterior oblique view was used to define the dimension of Koch's triangle. The distance of the proximal His-bundle recording site from the successful ablation site (DHis-Ab) and the distance as a fraction of the entire length of Koch's triangle (DHis-Ab/DHis-Os) were determined. The mean DHis-Os and DHis-Ab were 25.9 +/- 7.9 and 13.4 +/- 3.8 mm, respectively. DHis-Os negatively correlated with patient age (r = -0.41, P < 0.0001) and body mass index (r = -0.18, P = 0.004). Among the patients with successful ablation sites in the medial area, DHis-Os was longer (27.2 +/- 6.6 vs 24.6 +/- 8.4 mm, P < 0.005), DHis-Ab was similar (12.9 +/- 3.1 vs 13.9 +/- 4.0, P > 0.05) and DHis-Ab/DHis-Os was smaller (0.48 +/- 0.04 vs 0.74 +/- 0.11, P < 0.05). Furthermore, the patients with successful ablation sites in the medial location needed more radiofrequency pulse numbers than those in the posterior location (6 +/- 4 vs 4 +/- 3, P < 0.05).

CONCLUSION

The site of successful slow pathway ablation was consistently about 13 mm from the site recording the proximal His-bundle deflection in patients with AV nodal reentrant tachycardia despite marked variability in the dimensions of Koch's triangle; therefore, patients with large triangles required ablation in the medial region rather than the posterior region. Care should be taken when delivering radiofrequency energy to the posteroseptal area in patients with shorter DHis-Os to avoid injury to AV node.

Dual AV node pathway physiology in patients with Wolff-Parkinson-White syndrome

Published data on the relationship between dual AV node pathway physiology, locations and numbers of accessory pathways are limited. The purpose of this study is to appraise the dual AV node pathway physiology in a large group of patients with accessory AV pathways. A consecutive series of 759 patients was included for analysis. The incidence of antegrade or retrograde dual AV node pathway physiology and AV node reentrant tachycardia was similar for patients with accessory pathway at different locations. However, the incidence of bidirectional dual AV node pathway physiology (11.1%) and fast-slow type AV node reentrant echo (8.3%) was significantly higher in anteromidseptal accessory pathways. The incidence of antegrade (24.2% vs. 30.8%, P > 0.05), retrograde (4.9% vs. 2.9%, P > 0.05) and bidirectional dual AV node pathway physiology (3.0% vs. 2.9%, P > 0.05) was similar between the patients with a single pathway and multiple accessory pathways. Furthermore, the patients with multiple accessory pathways had a higher incidence of slow-fast form AV node reentrant tachycardia (8.8% vs. 3.0%, P = 0.034) and fast-slow form AV node reentrant echo (8.8% vs. 2.7%, P = 0.02). Thirty-four patients (4.5%) received slow pathway ablation for AV node reentrant tachycardia and none had recurrent tachycardia during the follow up period (26 +/- 7, range 1-56 months). We conclude that it is possible to find dual AV node pathway physiology in patients with accessory pathways because this phenomenon was not rare, especially in patients with a single pathway located in the anteromidseptal area or in patients with multiple accessory pathways.

Electrophysiologic characteristics and anatomical complexities of accessory atrioventricular pathways with successful ablation of anterograde and retrograde conduction at different sites

INTRODUCTION

Catheter ablation may eliminate anterograde and retrograde accessory pathway conduction at closely adjacent but anatomically discrete sites. However, the mechanisms of this discrepancy, the electrophysiologic and anatomical characteristics, and information about systematic study from a large patient population are not available. The purpose of this study was to investigate the electrophysiologic characteristics and anatomical complexities of the accessory pathway in which anterograde and retrograde conduction was successfully ablated at different sites.

METHODS AND RESULTS

Thirty-eight (10.9%) patients (19 men and 19 women; mean age 37 +/- 2.4 years) fulfilling the criteria of having separate ablation sites for anterograde and retrograde conduction were designated as group I, and the other 310 patients (215 men and 95 women; mean age 47 +/- 0.6 years) were designated as group II. The patients with right-sided free-wall pathways had the highest incidence (18.6%) of separate ablation sites. The anatomical distance between anterograde and retrograde directions (left anterior oblique view, 13 +/- 0.6 vs 8 +/- 0.9 mm, P < 0.01; right anterior oblique view, 17 +/- 0.6 vs 5 +/- 0.7 mm, P < 0.01), and incidence of conduction impairment in one direction after successful ablation of another direction (15% vs 78%, P < 0.05) differed significantly between left and right free-wall pathways. The mean distances obtained from left (7 +/- 0.4 vs 14 +/- 0.4 mm, P < 0.05) and right (7 +/- 1.1 vs 15 +/- 0.9 mm, P < 0.05) anterior oblique views were shorter in patients who had impairment of conduction properties than those in patients without impaired conduction after successful ablation of one direction.

CONCLUSIONS

This study showed that anatomical and functional dissociation of the accessory pathway into anterograde and retrograde components was possible. Further study on the relation between electrophysiologic and pathologic characteristics would be helpful to confirm these findings.

Electrophysiologic characteristics, electropharmacologic responses and radiofrequency ablation in patients with decremental accessory pathway

OBJECTIVES

This study sought to characterize the functional properties of decremental accessory atrioventricular (AV) pathways and to investigate their pharmacologic responses.

BACKGROUND

Although decremental AV pathways associated with incessant reciprocating tachycardia have been studied extensively, information about the electrophysiologic characteristics and pharmacologic responses of anterograde and retrograde decremental AV pathways is limited.

METHODS

Of 759 consecutive patients with accessory pathway-mediated tachyarrhythmia, 74 with decremental AV pathways were investigated (mean age 43 +/- 18 years). After baseline electrophysiologic study, the serial drugs adenosine, verapamil and procainamide were tested during atrial and ventricular pacing. Finally, radiofrequency catheter ablation was performed.

RESULTS

Five patients had anterograde decremental conduction over the accessory pathway but had no retrograde conduction. Of the 64 patients with retrograde decremental conduction over the accessory pathway, anterograde conduction over the pathway was absent in 41 (64%), intermittent in 5 (8%) and nondecremental in 18 (28%). In the remaining five patients, anterograde and retrograde decremental conduction over the same pathway was found. The anterograde and retrograde conduction properties and extent of decrement did not differ between anterograde and retrograde decremental pathways. Posteroseptal pathways had the highest incidences of anterograde and retrograde decremental conduction. Intravenous adenosine, procainamide and verapamil caused conduction delay or block, or both, in 10 of 10, 10 of 10 and 4 of 10 of the anterograde and 20 of 20, 20 of 20 and 8 of 20 of the retrograde decremental pathways, respectively. All patients had successful ablation of the decremental pathways without complications. During the follow-up period of 31 +/- 19 months, only one patient experienced recurrence.

CONCLUSIONS

Decremental accessory pathways usually had functionally distinct conduction characteristics in the anterograde and retrograde directions. Their pharmacologic responses suggested the heterogeneous mechanisms of decremental conduction.

Multiple anterograde atrioventricular node pathways in patients with atrioventricular node reentrant tachycardia

OBJECTIVES

This study sought to investigate electrophysiologic characteristics and possible anatomic sites of multiple anterograde slow atrioventricular (AV) node pathways and to compare these findings with those in dual anterograde AV node pathways.

BACKGROUND

Although multiple anterograde AV node pathways have been demonstrated by the presence of multiple discontinuities in the AV node conduction curve, the role of these pathways in the initiation and maintenance of AV node reentrant tachycardia (AVNRT) is still unclear, and possible anatomic sites of these pathways have not been reported.

METHODS

This study included 500 consecutive patients with AVNRT who underwent electrophysiologic study and radiofrequency ablation. Twenty-six patients (5.2%) with triple or more anterograde AV node pathways were designated as Group I (16 female, 10 male, mean age 48 +/- 14 years), and the other 474 patients (including 451 with and 23 without dual anterograde AV node pathways) were designated as Group II (257 female, 217 male; mean age 52 +/- 16 years).

RESULTS

Of the 21 patients with triple anterograde AV node pathways, AVNRT was initiated through the first slow pathway only in 3, through the second slow pathway only in 8 and through the two slow pathways in 9. Of the five patients with quadruple anterograde AV node pathways, AVNRT was initiated through all three anterograde slow pathways in three and through the two slower pathways (the second and third slow pathways) in two. After radiofrequency catheter ablation, no patient had inducible AVNRT. Eleven patients (42.3%) in Group I had multiple anterograde slow pathways eliminated simultaneously at a single ablation site. Eight patients (30.7%) had these slow pathways eliminated at different ablation sites; the slow pathways with a longer conduction time were ablated more posteriorly in the Koch's triangle than those with a shorter conduction time. The remaining seven patients (27%) had a residual slow pathway after delivery of radiofrequency energy at a single or different ablation sites. The patients in Group I had a longer tachycardia cycle length, poorer retrograde conduction properties and a higher incidence of multiple types of AVNRT than those in Group II.

CONCLUSIONS

Multiple anterograde AV node pathways are not rare in patients with AVNRT. However, not all of the anterograde slow pathways were involved in the initiation and maintenance of tachycardia. Radiofrequency catheter ablation was safe and effective in eliminating critical slow pathways to cure AVNRT.

Co-existence of atrial tachycardia and common atrial flutter: electrophysiological characteristics and radiofrequency catheter ablation

Four patients, who had no prior atrial surgery, underwent radiofrequency ablation for clinically documented typical atrial flutter. In addition to typical atrial flutter re-entrant atrial tachycardia was initiated during electrophysiological study in these four patients. We used earliest atrial endocardial activation and concealed entrainment pace mapping with short stimulus-P interval (< 40 ms) to identify the exit site of slow conduction are of atrial flutter were located at the posteromedial right atrium between the coronary ostium and the tricuspid annulus and those of slow conduction area of atrial tachycardia were located at high lateral right atrium in all four patients. Radiofrequency energy applied to these exit sites successfully eliminated both atrial flutter and atrial tachycardia in these four patients. Typical atrial flutter and re-entrant atrial tachycardia with two distinct re-entrant circuits concomitantly occurring in patients without prior atrial surgery are rare. Radiofrequency ablation can abolish both atrial tachyarrhythmias in the same ablation session.

Longitudinal clinical and electrophysiological assessment of patients with symptomatic Wolff-Parkinson-White syndrome and atrioventricular node reentrant tachycardia

BACKGROUND

Functional changes of the accessory AV pathways and dual AV node pathways are very important for patients with Wolff-Parkinson-White syndrome or AV node reentrant tachycardia who refuse to receive long-term medication or radiofrequency catheter ablation. However, no studies of serial clinical and electrophysiological characteristics in these patients have been performed.

METHODS AND RESULTS

One hundred thirteen patients with Wolff-Parkinson-White syndrome or AV node reentrant tachycardia were included in this study. The first and second follow-up electrophysiological studies were performed in years 5 and 10 after the baseline study, respectively. Conduction properties of the accessory pathways became poor over time. After a mean follow-up period of 9 +/- 1 years, antegrade ventricular preexcitation and retrograde accessory pathway conduction disappeared in 22.5% and 7.8% (P < .01), respectively; dual AV node pathway physiology persisted and retrograde fast pathway disappeared in 10.8% of the patients. Baseline conduction properties of the antegrade and retrograde accessory pathways and the retrograde fast pathway independently predicted late loss of conduction. Spontaneous disappearance of the original tachyarrhythmias occurred in 10.3% of all patients, and newly developed tachyarrhythmias in 15.2%. The incidence (38.5%) of newly developed atrial fibrillation was significantly higher in patients with manifest accessory pathways. Furthermore, symptom scores and attack frequency increased significantly over time in the patients with accessory pathways and AV node reentrant tachycardia.

CONCLUSIONS

Disappearance of the original tachycardia and changing patterns of tachycardia, also with an increase in symptom scores and attack frequency, suggested that a detailed evaluation of these events is important and early intervention with radiofrequency ablation would be helpful.

Electrophysiological mechanisms in successful radiofrequency catheter modification of atrioventricular junction for patients with medically refractory paroxysmal atrial fibrillation

BACKGROUND

Mechanisms and changes of electrophysiological (EP) characteristics in successful radiofrequency (RF) modification of right midseptal and posteroseptal areas for controlling rapid ventricular response to atrial fibrillation (Af) are not clear.

METHODS AND RESULTS

We studied 50 patients with medically refractory paroxysmal Af. Group 1 consisted of 40 patients without dual atrioventricular (AV) node physiology with modification sites located in the mid/posteroseptal area. Of the 40 patients, 36 had successful modification (follow-up of 14 +/- 8 months), and 3 had AV block. Late follow-up electrophysiological study (98 +/- 10 days) showed pattern 1 (67%) with prolongation of AV node effective refractory period (ERP, > or =40 milliseconds) and Wenckebach block cycle length (WBCL, > or =40 milliseconds); pattern 2 (22%) with prolongation of AH interval (> or =20 milliseconds), ERP, and WBCL; and pattern 3 (11%) without any change in AV node conduction parameter. Change in ventricular rate negatively correlated with change of WBCL in patterns 1 (r=-.691, P=.019) and 2 (r=-.90, P=.01). Group 2 consisted of 10 patients with dual AV node pathway; elimination of slow pathway property was performed. Late follow-up electrophysiological study (92+/-7 days) showed that change in ventricular rate negatively correlated with change in AV node ERP (r=-.926, P=.0001) and WBCL (r=-.969, P=.0001). Four patients without significant modification effect had success after RF energy was delivered to higher levels (follow-up, 15+/-7 months).

CONCLUSIONS

RF modification of right mid/posteroseptal area is feasible in 92% of patients with paroxysmal Af. Mechanisms of successful modification might be elimination of posterior input and/or partial injury of the compact node. Furthermore, simple elimination of slow pathway might be inadequate for control of ventricular rate in patients with little difference in conduction properties between fast and slow pathways.

Radiofrequency catheter ablation of common atrial flutter: comparison of electrophysiologically guided focal ablation technique and linear ablation technique

OBJECTIVES

The purpose of this study was to study electrophysiologic characteristics and compare the electrophysiologically guided focal ablation technique and linear ablation technique in patients with common atrial flutter in a prospective randomized fashion. Background. Catheter ablation of the common atrial flutter circuit can be performed with different techniques. To date, these two techniques have not been compared prospectively in a randomized study.

METHODS

Sixty patients with drug-refractory common atrial flutter were randomly assigned to undergo radiofrequency catheter ablation performed with the electrophysiologically guided focal ablation (Group I) or linear ablation technique (Group II). In Group I, radiofrequency energy was delivered to the site characterized by concealed entrainment with a short stimulus-P wave interval (<40 ms) and a postpacing interval equal to the atrial flutter cycle length. In Group II, continuous migratory application of radiofrequency energy was used to create two linear lesions in or around the inferior vena cava-tricuspid ring isthmus. Serial 24-h ambulatory electrocardiographic (Holter) and follow-up electrophysiologic studies were performed to assess recurrence of tachycardia and possible atrial arrhythmogenic effects.

RESULTS

Successful elimination of the flutter circuit was achieved in 28 of 30 patients in Group I and 29 of 30 patients in Group II. More atrial premature beats and episodes of short run atrial tachyarrhythmias in the early period (within 2 weeks) after ablation were found in Group II. Recurrence rate (2 of 28 vs. 3 of 29) and incidence of new sustained atrial tachyarrhythmias (3 of 28 vs. 3 of 29) was similar in the two groups. Occurrence of recurrent atrial flutter and new sustained atrial tachyarrhythmias was related to associated cardiovascular disease and atrial enlargement in both groups. However, in Group II, the procedure time (104 +/- 17 vs. 181 +/- 29 min, p<0.01) were significantly shorter than those in Group I.

CONCLUSIONS

Radiofrequency ablation of the common atrial flutter circuit was safe and effective with either the electrophysiologically guided focal ablation or linear ablation technique. However, the linear ablation technique was time-saving.

Prediction of successful ablation site of concealed posteroseptal accessory pathways by a novel algorithm using baseline electrophysiological parameters: implication for an abbreviated ablation procedure

BACKGROUND

Radiofrequency catheter ablation of concealed posteroseptal accessory pathways (APS) has been a relatively difficult task for electrophysiologists. Without a detailed mapping procedure, the left versus the right posteroseptal AP could not be distinguished. We investigated the electrophysiological characteristics of concealed posteroseptal APs and defined criteria from baseline parameters to predict the successful ablation site. Validity of the criteria was prospectively verified.

METHODS AND RESULTS

Eighty-nine consecutive patients with a single concealed posteroseptal AP underwent successful radiofrequency catheter ablation. Of the initial 48 patients (group 1), the right posteroseptal area was first mapped. If no ideal electrogram could be obtained, or after several ineffective radiofrequency pulses, the left posteroseptal area was then mapped. Special attention was paid to the stability of the coronary sinus catheter with the most proximal electrode straddling the ostium, verified by coronary sinus venography, in all patients. Six patients (12.5%) had the earliest retrograde atrial activation at the middle electrode of the coronary sinus catheter, and successful ablation could only be achieved at the left posteroseptal area. For patients who presented with the earliest atrial activation at the proximal electrode, the presence of long RP' tachycardia suggested a right endocardial approach, while the delta VA (defined as the difference in the VA intervals between that recorded at the His bundle catheter and that at one of the electrode groups recording the earlier atrial activation) >-25 ms during tachycardia suggested a left endocardial approach. The subsequent 41 patients (group 2) were randomized into two subgroups. The initial mapping site was guided by the algorithm in group 2B, while it was not in group 2A. The successful ablation site could be predicted accurately in 18 (90%) of the 20 patients in group 2B. The radiofrequency pulses, ablation time, and fluoroscopic time were markedly reduced in Group 2B, mainly because of the omission of unnecessary mapping procedure in the right posteroseptal area in patients with "left atrio-left ventricular" fibers.

CONCLUSIONS

By the algorithm based on baseline electrophysiological parameters, the successful ablation site could be accurately predicted in a majority of patients with concealed posteroseptal APs. Radiofrequency pulses, ablation time, and fluoroscopic time were markedly reduced.

Efficiency of heating during radiofrequency catheter ablation of accessory atrioventricular pathways

Adequate heating with myocardial thermal injury is necessary for successful ablation. This study was designed to examine the relationship between power, temperature, and efficiency of heating during radiofrequency catheter ablation of accessory pathways in 76 patients. During each application of radiofrequency energy, temperature was continually monitored by use of an ablation catheter with a thermistor embedded in the tip of the distal electrode. The efficiency of heating varied by location, with the greatest efficiency of heating for posteroseptal energy applications (2.7 +/- 2.3 degrees C/W), which were significantly greater than for left-sided (2.1 +/- 1.9 degrees C/W, P < 0.01) or right-sided (1.0 +/- 1.1 degrees C/W, P < 0.01) applications. For patients with left free wall and posteroseptal pathways, the temperature, radiofrequency power, time to peak temperature and efficiency of heating were similar between the successful and unsuccessful pulses. However, the mean temperature (53.5 +/- 4.5 vs. 45.1 +/- 5.1 degrees C, P < 0.01) and radiofrequency power (49.6 +/- 5.2 vs. 40.3 +/- 10.2 watt, P < 0.05) differed significantly between the successful and unsuccessful ablation pulses in patients with right free wall pathways. To achieve greater efficiency of heating and higher temperature, it is reasonable to use higher power outputs (40-50 W) in radiofrequency ablation of right free wall pathways, whereas less power outputs (30-40 W) are likely to produce adequate heating of posteroseptal and left free wall pathways, and minimize the risk of impedance rise and coagulum formation.