Nature of dual atrioventricular node pathways and the tachycardia circuit as defined by radiofrequency ablation technique

Familial atrioventricular nodal re-entrant tachycardia: A case seriers and a systematic review

Multiple reports of familial clustering suggest that genetic factors may contribute in the pathogenesis of atrioventricular nodal re-entrant tachycardia (AVNRT). We report three cases of AVNRT in a father and his two sons along with a review of literature of other similar cases. Electrophysiological studies induced typical AVNRT, which was successfully eliminated by radiofrequency ablation in all of them. Of the 22 reported cases, 96% had typical (slow-fast) variant of AVNRT. The predominant pattern of inheritance appears to be autosomal dominant, though other patterns may exist. Further research is needed to understand the genetic influence of AVNRT and its pathophysiology.

Long-Term Follow-Up After Catheter Ablation of Atrioventricular Nodal Reentrant Tachycardia in Children

Background—

Catheter ablation of the slow conducting pathway (SP) is treatment of choice for atrioventricular nodal reentrant tachycardia (AVNRT). Although there are abundant data on AVNRT ablation in adult patients, little is known about the long-term results ≥3 years after AVNRT ablation in pediatric patients.

Methods and Results—

Follow-up data from 241 patients aged ≤18 years who had undergone successful AVNRT ablation were analyzed. Median age at ablation had been 12.5 years, and median follow-up was 5.9 years. Radiofrequency current had been used in 168 patients (70%), whereas cryoenergy had been used in 73 patients (30%). Procedural end point of AVNRT ablation had been either SP ablation (no residual dual atrioventricular nodal physiology) or SP modulation (residual SP conduction allowing for a maximum of one atrial echo beat). After the initial AVNRT ablation, calculated freedom from AVNRT was 96% at 1 year, 94% at 3 years, 93% at 5 years, and 89% at 8 years. Age, sex, body weight, the choice of ablation energy, and the procedural end point of AVNRT ablation did not impact freedom from AVNRT. Six of 22 AVNRT recurrences (27%) occurred ≥5 years after ablation. No late complications including atrioventricular block were noted.

Conclusions—

Cumulatively, catheter ablation of AVNRT continued to be effective in >90% of our pediatric patients during the long-term course. A significant part of recurrences occurred >5 years post ablation. Body weight, energy source, and the end point of ablation had no impact on long-term results. No adverse sequelae were noted.

[Dual AV nodal nonreentry tachycardia (DAVNNT): unrecognized differential diagnosis with far-reaching consequences]

BACKGROUND

The dual atrioventricular nodal nonreentry tachycardia (DAVNNT) is a rare form of tachycardia which occurs due to a time delayed double antegrade conduction via the slow and fast atrioventricular nodal pathways. Its epidemiology is not known so far. The aim of this article is to present the clinical findings in a series of patients with DAVNNT.

MATERIALS AND METHODS

We retrospectively analyzed our database of patients who successfully underwent radiofrequency catheter ablation between January 2012 and March 2013 due to diagnosed supraventricular tachycardia.

RESULTS

In 3 out of 231 patients DAVNNT could be successfully treated by slow pathway modulation/ablation. Patients presented with widely varying symptoms including syncope, palpitations which had been mistaken as atrial fibrillation, and inappropriate defibrillator shocks due to suspected ventricular tachycardia.

CONCLUSIONS

The DAVNNT seems to be more common than previously thought. This important differential diagnosis needs to be taken into consideration as slow pathway modulation can be curative while a misdiagnosis, such as atrial fibrillation or ventricular tachycardia might result in over-treatment in patients with this arrhythmia.

Effects of slow pathway ablation on fast pathway function in patients with atrioventricular nodal reentrant tachycardia: cryo- vs. radiofrequency ablation

BACKGROUND

In typical atrioventricular nodal reentrant tachycardia, radiofrequency (RF) ablation of the slow pathway (SP) is known to change the effective refractory period of the fast pathway (ERP(FP)) after successful RF ablation of the SP. The purpose of this study was to ascertain the mechanism of the ERP(FP) changes after SP ablation by comparing the results of both cryo- and RF ablation.

METHODS AND RESULTS

A total of 112 patients were enrolled prospectively and their electrophysiological properties analyzed before and after successful SP ablation. Patients were grouped into cryoablation (n=54) and RF ablation (n=58) groups and each group was subdivided into complete ablation (CG) and modification (MG) based on the presence of the SP after successful ablation. CG was performed in 64 patients: 30 by cryoablation and 34 by RF ablation. In patients who underwent complete SP ablation, the ERP(FP) was shortened significantly after cryoablation (375 ± 74 vs. 281 ± 39 ms, P<0.01), without significant change in the atrio-His (AH) or sinus cycle length (SCL) interval. Similarly, the ERP(FP) was shortened significantly (358 ± 106 vs. 289 ± 84 ms, P=0.01) also after RF ablation without change in AH or SCL interval.

CONCLUSIONS

ERP(FP) shortening was observed after complete SP ablation with both cryo- and RF ablation without significant changes in indices of autonomic activity.

Atrioventricular nodal reentrant tachycardia treatment using novel potential

Radiofrequency ablation of atrioventricular nodal reentrant tachycardia is commonly guided by slow and sharp bipolar potentials of the atrioventricular slow nodal pathway. We optimized the morphology of the guiding potential by unipolar mapping of the slow nodal pathway. We identified a novel unipolar dual-component atrial electrogram at the anterior limb of the coronary sinus ostium. The first component was a positive delta-wave type that corresponded to the isoelectric phase on a bipolar electrogram. The second component had fast biphasic morphology and corresponded to the R wave on a bipolar atrial electrogram. Of 104 consecutive patients with typical atrioventricular nodal reentrant tachycardia, 51 were treated with ablation guided by the novel potential, and 53 underwent ablation using the conventional technique. There was no recurrence of tachycardia in any of these patients. In those treated by the novel potential, there was significantly less radiofrequency power applied and a shorter duration of application than in patients treated by the traditional approach. The novel approach to mapping and ablation of the slow nodal pathway in atrioventricular nodal reentrant tachycardia guided by unipolar recording was safe and effective, and comparable to the traditional technique.

Ablation of atrioventricular nodal reentrant tachycardia in a patient with reversal of slow and fast pathways inputs into the atrioventricular node

We report a case of atrioventricular nodal reentrant tachycardia (AVNRT) coexistent with His bundle anomaly and atrial septal defects. The His-bundle potential was recorded at the coronary sinus (CS) ostium. Fractionated atrial potentials and an A:V electrogram ratio 1:3 were recorded at the anterior septum of the tricuspid annulus approximately 2 cm from CS ostium. Radiofrequency catheter ablation at the anterior septum of the tricuspid annulus effectively eliminated AVNRT.

The atrioventricular nodal reentrant tachycardia circuit: A proposal

Several models of the atrioventricular nodal reentrant tachycardia circuit have been proposed. Recently, there has been experimental and clinical electrophysiology evidence that the right and left inferior extensions of the human atriventricular node and the atrionodal inputs they facilitate may provide the anatomic substrate of the slow pathway. Inferior nodal extensions appear to constitute a necessary limb of the tachycardia circuit in all forms of atrioventricular nodal reentrant tachycardia and represent the ablation target for all forms of this arrhythmia. Anatomic variations of multiple atrionodal inputs via atrial transitional cells may create the conditions for tachycardia inducibility and differing patterns of retrograde atrial activation. In the present article, we summarize the available evidence and propose a comprehensive model of the tachycardia circuit for all forms of atrioventricular nodal reentrant tachycardia based on the concept of atrionodal inputs.

Incidence and Mechanism of Dislocated Fast Pathway in Various Forms of Atrioventricular Nodal Reentrant Tachycardia

BACKGROUND

The incidence and mechanism of the dislocated antegrade fast pathway (A-FP) were examined in various forms of atrioventricular nodal reentrant tachycardia (AVNRT).

METHODS AND RESULTS

To localize the A-FP, 5 atrial sites comprising the inferior coronary sinus ostium (CSOS), apex of the triangle of Koch (A-TOK), and 3 equidistant sites on the atrioventricular junction extending from A-TOK to CSOS (site S, M, and I) were pace mapped at 100 beats/min in 71 patients with slow-fast (n=49), fast-slow (n=7) and slow-intermediate (n=15) forms of AVNRT. The site with the shortest interval between the stimulus and His potential recorded at the A-TOK (shortest St-H) was defined as the A-FP site. The A-FP was located at A-TOK in 31 patients (nondislocated group), and inferior to A-TOK in 40 patients (site S in 26, M in 13, and I in one patient; dislocated group). There was no significant difference in the location of the A-FP among the 3 forms of AVNRT. Although the shortest St-H did not differ between groups, the St-H at A-TOK in the dislocated group was significantly longer than that in the nondislocated group. Additionally, the His potential preceding that of the A-TOK was observed more frequently inferior to the A-TOK in the dislocated group than in the nondislocated group, suggesting that the A-FP dislocation was accompanied by displacement of the His bundle.

CONCLUSIONS

Dislocated A-FP was frequently and uniformly observed among various forms of AVNRT, and is probably caused by inferior displacement of the entire atrioventricular node - His bundle apparatus.

Classification and differential diagnosis of atrioventricular nodal re-entrant tachycardia

Recent evidence on atrioventricular nodal re-entrant tachycardia has identified several types of this common arrhythmia, with potential therapeutic implications. This article reviews the relevant new information, discusses the differential diagnosis of atrioventricular nodal re-entrant tachycardia, and summarizes the electrophysiological criteria for classification of the various forms of the arrhythmia.

Long-term follow-up of patients with P-R prolongation after catheter ablation of slow pathway for atrioventricular node re-entrant tachycardia

BACKGROUND

Long-term impact of interval between P wave and R wave (P-R) prolongation on prognosis of patients with successful catheter ablation of slow atrioventricular nodal pathway was investigated.

METHODS

Among 436 patients undergoing slow-pathway ablation for atrioventricular node re-entrant tachycardia (AVNRT), 17 (3.9%) experienced permanent P-R prolongation. Ablation target sites where conduction block was induced were located in mid- or anteroseptum. Fast junctional rhythm with ventriculoatrial conduction block was observed in eight patients immediately before atrioventricular block.

RESULTS

Antegrade slow-pathway conduction was eliminated in 16 patients, and retrograde fast- and slow-pathway conduction was abolished in all patients. There was no recurrence of AVNRT after an average of 38 +/- 12 month follow-up. There was no deterioration of atrioventricular block in these patients. Average PR interval prior to hospital discharge and at the end of follow-up was 0.24 +/- 0.02 sec and 0.23 +/- 0.02 sec, respectively (p >0.05). Left ventricular ejection fraction remained unchanged in these patients (p >0.05).

CONCLUSIONS

Radiofrequency catheter ablation of slow pathway for AVNRT is associated with a small risk of atrioventricular block. PR prolongation after successful slow-pathway ablation is associated with benign prognosis.

Narrow QRS Tachycardia with Ventriculoatrial Dissociation Mediated by a Left Fasciculoventricular Fiber

A 30-year-old man presented with narrow QRS tachycardia. The intracardiac electrocardiogram showed an atrial-HIS (AH) interval of 75 msec and a HIS-ventricular (HV) interval of 44 msec during baseline. Atrial incremental pacing revealed HV shortening, with apparent incomplete right bundle branch block (RBBB) morphology without QRS complex axis deviation. The induced tachycardia exhibited several QRS morphologies: a narrow QRS, complete RBBB and complete left bundle branch block (LBBB) morphology. Spontaneous conversion of the QRS pattern from wide to narrow was observed. The cycle length of the tachycardia was significantly shortened (from 316 to 272 ms) from LBBB morphology to narrow QRS complex. The atrial activation was dissociated from the ventricular activation during all tachycardias. Each QRS complex during tachycardia was preceded by a HIS deflection and HV interval was 35 ms, which was shorter than that of sinus rhythm. HIS deflection was earlier than right bundle potential during all kinds of tachycardia. This tachycardia is most likely mediated by a left fasciculoventricular fiber which connects the HIS bundle below the atrioventricular node to the myocardial tissue of the left ventricle. The HIS-Purkinje system is used as an antegrade conduction limb and the fasciculoventricular fiber as a retrograde limb in the tachycardia circuit.

Acute and Long-Term Results of Slow Pathway Ablation in Patients with Atrioventricular Nodal Reentrant Tachycardia-An Analysis of the Predictive Factors for Arrhythmia Recurrence

BACKGROUND

Predictors of atrioventricular nodal reentrant tachycardia (AVNRT) recurrence after radiofrequency ablation including the importance of residual slow pathway conduction are not known. The aim of this study was to report the acute and long-term results of slow pathway ablation in a large series of consecutive patients with AVNRT and to analyze the potential predictors of arrhythmia recurrence with a particular emphasis on the residual slow pathway conduction after ablation.

METHODS

The study included 506 consecutive patients with AVNRT (mean age 52.6 +/- 16 years, 315 women) who underwent slow pathway ablation using a combined electrophysiological and anatomical approach. The end point of ablation procedure was noninducibility of the arrhythmia. The primary end point of the study was the recurrence of AVNRT.

RESULTS

Acute success was achieved in 500 patients (98.8%). After ablation, 471 patients (93%) were followed up for a mean of 903 +/- 692 days. Of the 465 patients with successful ablation, 24 patients (5.2%) developed AVNRT recurrences during the follow-up. No significant differences in the cumulative rates of AVNRT recurrence were observed in groups with or without electrophysiological evidence of residual slow pathway conduction (P = 0.25, log-rank test). Multivariate analysis identified only age as an independent predictor of AVNRT recurrence (hazard ratio 0.96, 95% confidence interval 0.94-0.99, P = 0.004) with younger patients being at an increased risk for arrhythmia recurrence.

CONCLUSIONS

Our study demonstrated that only younger age, but not other clinical or electrophysiological parameters including residual slow pathway conduction predicted an increased risk for AVNRT recurrence after slow pathway radiofrequency ablation.

Catheter ablation in the year 2000

After its introduction in 1987, radiofrequency catheter ablation became established as a safe and effective therapy for the cure of many cardiac arrhythmias in people. The possibility of assessing the relationship between the anatomical target and the electrophysiologic changes produced by radiofrequency pulse delivery has also provided significant improvement in the physician's knowledge of the pathophysiology of the underlying rhythm disturbance. Nowadays, using this therapy, success rates well above 90% with recurrence rates lower than 5% are expected after treatment of most regular supraventricular arrhythmias. As catheter ablation techniques develop, success rates in the range of those obtained for regular supraventricular arrhythmias are expected in the future in the treatment of regular ventricular and irregular supraventricular arrhythmias.

Variation of P-QRS relation during atrioventricular node reentry tachycardia

OBJECTIVES

The main objective of this study was to characterize the phenomenon of variation in the P-QRS relation during atrioventricular node reentry tachycardia.

BACKGROUND

Variation of P-QRS relation during tachycardia has been observed occasionally in atrioventricular node reentry tachycardia. However, the incidence, the characteristics and the mechanisms of this phenomenon have not been investigated previously.

METHODS

Retrospective analysis was performed in 311 consecutive patients with slow-fast form and 108 patients with atypical or multiple form of atrioventricular node reentry tachycardia to examine whether variation of P-QRS relation with changes in AH, HA and AH/HA (A = atria; H = His bundle) ratio occurred during tachycardia.

RESULTS

A total of 28 patients, 8 with slow-fast and 20 with atypical or multiple tachycardias, were found to manifest this phenomenon. There were 6 males and 22 females, with an average age of 38+/-16 years. In 10 patients, this phenomenon occurred transiently following electrical induction of the tachycardia. In 15 patients, changes in AH, HA and AH/HA ratio were associated with the occurrence of Wenckebach or 2:1 block proximal to the His bundle (H) recording site without interruption of the tachycardia. In nine patients, three with nonsustained tachycardia and six after administration of adenosine triphosphate, this phenomenon was observed at the termination of the tachycardia. This phenomenon was usually accompanied by a mild lengthening of the tachycardia cycle length.

CONCLUSIONS

Variation of P-QRS relation with or without block may occur during atrioventricular node reentry tachycardia, especially in atypical or multiple-form tachycardias. It was postulated that decremental conduction in the distal common pathway, which exists between the distal link of the reentry circuit and the H, is primarily responsible for this phenomenon.

Junctional tachycardia during radiofrequency ablation of the slow pathway in patients with AV nodal reentrant tachycardia: effects of autonomic blockade

INTRODUCTION

The autonomic nervous system richly innervates the peri-AV nodal region and may be activated during radiofrequency (RF) ablation for AV nodal reentrant tachycardia, resulting in the generation of junctional tachycardia. The purpose of this prospective study was to determine the role of the autonomic nervous system in the genesis of junctional tachycardia.

METHODS AND RESULTS

We compared the characteristics of junctional tachycardia in patients with (n = 10) and without (n = 10) autonomic blockade undergoing RF ablation for AV nodal reentrant tachycardia. Intravenous administration of atropine (0.04 mg/kg) and propranolol (0.2 mg/kg) were used to block the autonomic nervous system. There were no differences in clinical variables and baseline electrophysiologic characteristics between the two groups except for slightly longer effective refractory periods of the fast pathway and of the atrium in the autonomic blockade group. The autonomic blockade shortened the baseline sinus cycle length and effective refractory period of the ventricle only but not other electrophysiologic characteristics of the AV node. The junctional tachycardia was observed during ablation in each patient, but its occurrence and cycle length, as well as numbers of consecutive junctional beats, were not altered by the autonomic blockade.

CONCLUSION

Our results indicate that the muscarinic and beta-adrenergic components of the autonomic nervous system play no role in the genesis of junctional tachycardia.

New evidence that AV node slow pathway conduction directly influences fast pathway function

INTRODUCTION

Shortening of the AV node fast pathway effective refractory period (ERP) following successful slow pathway ablation may be a nonspecific effect of energy application at the AV junction or may be due to elimination of a direct effect of slow pathway conduction on the fast pathway.

METHODS AND RESULTS

Twenty-six consecutive patients (20 women and 6 men; mean age 45 +/- 3 years) with typical AV nodal reentrant tachycardia who underwent successful slow pathway ablation (defined as complete elimination of dual AV node physiology) were studied. The fast pathway ERP (at a drive train cycle length of 600 msec) was determined prior to ablation (baseline) and following unsuccessful and successful ablation attempts. Successful slow pathway ablation shortened the fast pathway ERP significantly (317 +/- 9 msec; P < 0.001) compared to baseline (386 +/- 12 msec), whereas unsuccessful ablations had no effect (376 +/- 11 msec). Sinus cycle length, the AH interval, and blood pressure were unchanged following successful ablation. Shortening of the fast pathway ERP did not correlate with the number of energy applications or with two measures of the proximity between the slow and the fast pathway.

CONCLUSION

These results support the hypothesis that shortening of the fast pathway ERP following slow pathway ablation is due to elimination of a direct effect of slow pathway conduction on fast pathway function rather than a nonspecific effect of repeated energy delivery at the AV junction.

[Long-term follow up of patients with nodal reentry tachycardia who had undergone radiofrequency ablation]

INTRODUCTION

The aim of this study was to assess the long term results (minimum of 3 years) of radiofrequency catheter ablation in patients with common (slow-fast) atrioventricular nodal reentrant tachycardia.

PATIENTS AND METHODS

Sixty consecutive patients (mean age 56 +/- 16 years, range 14 to 83, 16 men and 44 women) underwent slow pathway (n = 51, Group A) or fast pathway (n = 9, Group B) radiofrequency catheter ablation between January 1992 and March 1994. All patients were followed at 1, 3, 6 and 12 months after ablation with serial examinations and electrocardiograms and the last follow-up was made on April 1997.

RESULTS

During a mean follow-up period of 48 +/- 7 months (range 38 to 63) all evaluated patients remained asymptomatic. Eight recurrences were observed at a mean of 1 +/- 2 months (range, 0.5 to 7) after a successful ablation procedure. A second procedure was effective in eliminating the dual atrioventricular nodal pathway in each of them. In Group A patients, the pre-ablation PR interval, at 12 months after ablation and at last follow-up were 122 +/- 11, 124 +/- 13 and 124 +/- 15 ms, respectively. In Group B patients, the pre-ablation PR interval, at 12 months after ablation and at last follow-up were 130 +/- 24, 200 +/- 12, 200 +/- 24 ms, respectively. No significant atrioventricular conduction disturbances in any patient were observed. One patient developed a new onset left bundle branch block and 4 patients died of noncardiac causes.

CONCLUSIONS

In patients with atrioventricular nodal reentrant tachycardia, radiofrequency catheter ablation is a safe and effective therapy, with substantial good results that persist during long term follow-up, with a low recurrence rate and without complications during short and long term outcome.

Electrophysiology of the atrio-AV nodal inputs and exits in the normal dog heart: radiofrequency ablation using an epicardial approach

INTRODUCTION

We studied the effects of selective and combined ablation of the fast (FP) and slow pathway (SP) on AV and VA conduction in the normal dog heart using a novel epicardial ablation technique.

METHODS AND RESULTS

For FP ablation, radiofrequency current (RFC) was applied to a catheter tip that was held epicardially against the base of the right atrial wall. SP ablation was performed epicardially at the crux the heart. Twenty-three dogs were assigned to two ablation protocols: FP/SP ablation group (n = 17) and SP/FP ablation group (n = 6). In 12 of 17 dogs, FP ablation prolonged the PR interval (97 +/- 10 to 149 +/- 22 msec, P < 0.005) with no significant change in anterograde Wenckebach cycle length (WBCL). Subsequent SP ablation performed in 8 dogs further prolonged the PR interval and the anterograde WBCL (117 +/- 22 to 193 +/- 27, P < 0.005). Complete AV block was seen in 1 of 8 dogs, whereas complete or high-grade VA block was seen in 6 of 8 dogs. In the SP/FP ablation group, SP ablation significantly increased WBCL with no PR changes. Combined SP/FP ablation in 6 dogs prolonged the PR interval significantly, but no instance of complete AV block was seen. VA block was found in 50% of these cases. Histologic studies revealed that RFC ablation affected the anterior and posterior atrium adjacent to the undamaged AV node and His bundle.

CONCLUSION

Using an epicardial approach, combined ablation of the FP and SP AV nodal inputs can be achieved with an unexpectedly low incidence of complete AV block, although retrograde VA conduction was significantly compromised.

Effects of slow pathway ablation on fast pathway function in patients with atrioventricular nodal reentrant tachycardia

INTRODUCTION

This study investigated whether fast pathway conduction properties are altered by slow pathway ablation in patients with AV nodal reentrant tachycardia.

METHODS AND RESULTS

Forty consecutive patients who underwent successful ablation of the slow pathway were prospective subjects for the study. Isoproterenol was used to enhance conduction and to differentiate interactive mechanisms. Potential electrotonic interactions were assessed by comparing patients with and those without residual dual AV node physiology after slow pathway ablation. Paired and unpaired t-tests were used when appropriate P < 0.05 was considered statistically significant. In the entire study population, heart rates were not significantly different before and after slow pathway ablation (RR = 770 +/- 114 msec before and 745 +/- 99 msec after, P = 0.07). Anterograde fast pathway conduction properties were unchanged after slow pathway ablation (effective refractory period, 348 +/- 84 msec before and 336 +/- 86 msec after, P = 0.13; shortest 1:1 conduction, 410 +/- 93 msec before and 400 +/- 82 msec after, P = 0.39). Retrograde fast pathway characteristics also were similar before and after ablation. Neither anterograde nor retrograde fast pathway conduction properties during isoproterenol infusion were changed by slow pathway ablation. When the study population was further divided into patients with (n = 13) or without (n = 27) residual dual AV node physiology, no significant change was detected in fast pathway function in either group after slow pathway ablation.

CONCLUSIONS

Fast pathway conduction characteristics were not affected by slow pathway ablation. In patients with AV nodal reentrant tachycardia, observations suggest that fast and slow pathways are functionally distinct.

Catheter-induced atrioventricular nodal block during radiofrequency ablation

This study examined the incidence and significance of catheter-induced atrioventricular nodal block (AVNB) during a radiofrequency ablation procedure that uses stiff large-tip steerable ablation catheters. AVNB was noted in 10 (1.6%) of 613 consecutive patients undergoing radiofrequency ablation therapy for atrioventricular nodal (AVN) reentrant tachycardia (592 patients) or atrioventricular reentry tachycardia incorporating a midseptal accessory pathway (21 patients). Of these 10 patients, 9 underwent AVN modification for AVN reentrant tachycardia and 1 for ablation of a midseptal accessory pathway. One patient had two episodes of AVNB during two sessions undertaken because of recurrence of tachycardia. No patient had a preexisting conduction defect before the study. In all 10 patients, AVNB was transient, and it lasted for a mean of 9.1 +/- 19 minutes. It occurred during positioning of the ablation catheter in the junctional area before (8 patients) or after (2 patients) the start of radiofrequency current applications. Complete AVNB was noted on six occasions, second-degree AVNB on four occasions, and first-degree AVNB on one occasion. All blocks were associated with narrow QRS ventricular beats and with a site of block proximal to the His bundle. The mean ventricular heart rate during AVNB was 60 +/- 23 beats/min. Two patients had transient asystole, with one having loss of consciousness. No patient required special treatment for heart block. One-to-one conduction resumed after repositioning of the catheters, and the subsequent ablation procedure was successfully completed in 8 of the 10 patients. During a follow-up of 20 +/- 12 months, none of the patients had severe dizziness or syncope, and none required implantation of a permanent pacemaker. In conclusion, transient AVNB due to mechanical injury occurs during positioning of a stiff large-tip steerable ablation catheter in the junctional area. Delivery of radiofrequency current to the site that provokes catheter-induced AVNB should be avoided.

Radiofrequency ablation for supraventricular and ventricular tachycardia in young patients

Radiofrequency ablation therapy was conducted in 86 consecutive children and young patients with a mean age of 14 +/- 3 years (range = 3-18). Fifty-two patients had Wolff-Parkinson-White syndrome, one had re-entry tachycardia incorporating a nodoventricular fiber, 22 had atrioventricular node re-entry tachycardia, two had atrial tachycardia and nine had idiopathic ventricular tachycardia. Radiofrequency ablation was successful in 50 of the 52 patients (96%) with Wolff-Parkinson-White syndrome and the one with nodoventricular fiber. Radiofrequency modification of the atrioventricular node using the inferior approach was successful in eliminating atrioventricular node re-entry tachycardia in 20 of the 22 patients (91%). Radiofrequency ablation in the two patients with atrial tachycardia was unsuccessful. Of the nine patients with idiopathic ventricular tachycardia, eight from the left ventricle and one from the right ventricular outflow tract, eight were successfully ablated (88%). Follow-up over a period ranging from 1 to 46 months (21 +/- 13) revealed a recurrence of tachycardia in seven patients; a late electrophysiological study in 38 patients revealed the induction of tachycardia in 11 patients (seven with accessory pathway-mediated tachycardia, three with atrioventricular node re-entry tachycardia and one with idiopathic ventricular tachycardia). All 11 patients were successfully ablated by a second trial. In conclusion, radiofrequency ablation therapy is effective and safe in pediatric patients with supraventricular and ventricular tachycardia and should be considered as the therapy of choice in this group of patients.

Posterior fast atrioventricular node pathways: implications for radiofrequency catheter ablation of atrioventricular node reentrant tachycardia

OBJECTIVES

This study sought to present evidence that fast atrioventricular (AV) node pathways with posterior exit sites may participate in typical AV node reentry.

BACKGROUND

Catheter ablation of the slow AV node pathway in the posteroseptal right atrium is the preferred therapeutic approach in patients with AV node reentrant tachycardia. Despite the success achieved with this approach, electrophysiologic changes consistent with fast pathway ablation are occasionally observed. One potential explanation is the presence of an aberrant posterior fast pathway.

METHODS

The location of fast and slow AV node pathways was determined by atrial activation mapping along the tricuspid valve annulus during tachycardia and was further confirmed by the effect of radiofrequency catheter ablation.

RESULTS

Seven patients with AV node reentrant tachycardia had evidence of a posterior fast pathway near the coronary sinus os. Abolition of anterograde and retrograde fast pathway conduction followed radiofrequency ablation in the posteroseptal region in six patients. Consistent with fast pathway ablation, the AH interval increased from 70 +/- 24 to 195 +/- 35 ms (mean +/- SD), and tachycardia was no longer inducible. Selective slow pathway ablation was performed in one other patient with a posterior fast pathway.

CONCLUSIONS

Functionally fast AV node pathways may be located in the posteroseptal right atrium, where slow pathway modification is performed. These data delineate the limitation of an anatomically guided slow pathway ablative approach and emphasize the importance of detailed mapping and localization of the retrograde fast pathway exit site before ablation. Failure to recognize the presence of posterior fast AV node pathways may account for sporadic examples of AV block, complicating posteroseptal ablation in patients with AV node reentry.

Perinodal slow potential as a local guide for transcatheter radiofrequency ablation of atrioventricular nodal reentrant tachycardia: therapeutic efficacy and electrophysiological mechanisms of success

BACKGROUND

A specific local indicator in the Koch's triangle could be critical to the complication-free treatment of atrioventricular nodal reentrant tachycardia by transcatheter radiofrequency ablation. Recording of perinodal slow potential reflects a slow conduction area, and probably indicates the location of the slow pathway component of the circuit. Specific ablation of the slow pathway would carry the least risk of atrioventricular block.

METHOD AND RESULTS

Guided by the mapped perinodal slow potential, atrioventricular nodal reentrant tachycardia was successfully eliminated in all of 55 consecutive patients in one session. Fifty two patients (94.5%) had confirmed slow potential at the final success sites. Despite the good result, the underlying electrophysiological mechanisms of early success from slow-potential-guiding catheter ablation were heterogeneous: selective slow pathway eradication in 31 patients (56.4%, group A), selective slow pathway modification in 18 patients (32.7%, group B), inadvertent fast pathway damage in six patients (10.9%, group C). Group B patients had the preservation of dual atrioventricular nodal pathways, adequate atrio-Hisian delay, fast pathway facilitation, and a higher frequency of inducible, single non-conducted nodal echo (15/18, 83.3% v 6/31, 19.4% in group A, P << 0.001). The upper communicating path of the circuit was implicated as another site of radiofrequency destruction. Three recurrences were documented in follow up study. However, reablation by the same approach caused complete atrioventricular block in one patient (1.7%, 1/58 procedures). None of the local characteristics of ablation sites was an independent predictor of procedure outcome.

CONCLUSIONS

Perinodal slow potential is not a specific slow pathway indicator in transcatheter radiofrequency ablation of atrioventricular nodal reentrant tachycardia. Multiple strategic sites of the reentry circuit may be damaged through similar local signals.

Change in delay of atrioventricular conduction after radiofrequency catheter ablation for atrioventricular nodal re-entry tachycardia

OBJECTIVE

To monitor atrioventricular conduction after radiofrequency ablation for atrioventricular nodal re-entry tachycardia.

DESIGN

Measurement of PR interval from 12 lead surface electrocardiograms before; at 0, 24, 48, 72, and 96 hours; and at 1 and 6 months after radiofrequency ablation.

PATIENTS

40 consecutive patients with atrioventricular nodal re-entry tachycardia. The anterior approach was used in 23 patients, the posterior approach in 17.

RESULTS

With the anterior approach the PR interval increased significantly and progressively until 48 hours after ablation (maximum 282 (SD 62.2) ms, before ablation 142 (29.5) ms; P < 0.0001). Up to 96 hours no further change was observed, but one month after ablation the PR interval had decreased to a value not significantly different from that 24 hours after the procedure (231 (51.2) ms). In one patient total atrioventricular block developed 24 hours after an uncomplicated procedure and a permanent pacemaker was implanted. With the posterior approach the PR interval increased slightly in the first 24 hours (156 (22.7) ms, before ablation 144 (21.2) ms P = 0.004), but it had returned to preablation values at 1 month. One patient developed second degree atrioventricular block during the first 24 hours after ablation, despite delivery of all radiofrequency pulses posterior to Koch's triangle at sites without His bundle deflection. PR intervals at 6 months did not differ significantly from the values at 1 month.

CONCLUSION

After the anterior approach the progressive delay in atrioventricular conduction up to 48 hours after radiofrequency ablation for atrioventricular nodal re-entry tachycardia warrants continuous in hospital monitoring of patients for at least two days after the procedure.

Ablative therapy for atrioventricular nodal reentry arrhythmias

Recent studies in the clinical electrophysiology laboratory have advanced our understanding of the physiologic anatomy of the atrioventricular (AV) junction and have helped direct new curative techniques for the treatment of AV nodal (junctional) reentry. In most patients, it appears that the AV node or the inputs to the AV node that constitute the "slow" pathway are located caudal to the compact AV node and His bundle region near the os of the coronary sinus. In contrast, conduction over the "fast" pathway appears to be located along the anterior tricuspid annulus proximal to the traditional His bundle recording position. This physiologic heterogeneity has allowed the development of curative techniques for AV nodal reentry. The current preferred technique involves ablation of the slow pathway by delivering radiofrequency lesions in the region of the coronary sinus ostium. Although several different localization techniques have been developed, the overall success rate for the procedure developed, the overall success rate for the procedure includes a primary success rate that should be over 95%, a 5% to 10% late recurrence rate, and a complication rate of under 2%. Complete heart block as a complication of slow AV nodal pathway ablation is rate but can occur. The improvements in the results of radiofrequency ablation for the treatment of AV nodal reentry have resulted in the increased use of this procedure clinically. It is now reasonable to offer young patients AV nodal modification as primary therapy for AV nodal reentry and to apply the technique in all age groups to drug-resistant patients.

The architecture of the atrioventricular conduction axis in dog compared to man: its significance to ablation of the atrioventricular nodal approaches

AV Node in Dog and Man.

INTRODUCTION

Advances in treating patients with dual atrioventricular nodal pathways have called for a better understanding of the morphology of the approaches to the atrioventricular node. In this respect, it has recently been suggested that, in dog, anatomically discrete muscle bundles originating from the sinus node represent the substrate of the dual pathways recognized electrophysiologically in patients with atrioventricular nodal reentrant tachycardia. This concept is at odds with most anatomic studies of the human specialized atrioventricular junctional area. In this study, therefore, we studied histologically the junctional area in dog hearts, comparing them with our own findings in human heart and the descriptions of the earliest investigators.

METHODS AND RESULTS

Five dog and six human hearts were prepared for histology and sectioned serially in different planes. Reconstructions were then made from each of three dog and two human hearts sectioned in orthogonal planes. Gross differences in the anatomy of the atrioventricular junctional area and in the structure of the conduction system were obvious between dog and human hearts. The penetrating portion of the conduction axis was longer in the dog, being much more extensively embedded in the central fibrous body. The atrioventricular node, in both dog and man, was composed of a zone of transitional cells overlying a compact region. The zone of transitional cells in the dog was more extensive posteriorly than anteriorly. No bundles insulated anatomically by fibrous tissue were found either in the internodal atrial myocardium or in the approaches to the atrioventricular node. Our findings in both dog and man are comparable with the initial descriptions of the atrioventricular junctional area.

CONCLUSION

Although the disposition of the conduction system in dog and man is basically similar, there are important differences which relate to the gross anatomy. The anatomic substrate for functional duality of the inputs to the atrioventricular node remains unclear, since our study confirms that the concept of insulated atrionodal tract has no morphologic basis.

Radiofrequency ablation therapy in atypical or multiple atrioventricular node reentry tachycardias

Electrophysiologic study and radiofrequency ablation therapy were performed in 23 patients with atypical (8 patients) or multiple (15) atrioventricular node reentry tachycardias. Dual pathways with anterograde fast and slow pathway conductions were demonstrated in 16 patients. Studies on retrograde conduction revealed the presence of three different pathways, including fast (15 patients), intermediate (17), and slow (16). The radiofrequency current was applied to the inferior aspect, one-third anterior two-thirds posterior between the His bundle and the ostium of the coronary sinus, of Koch's triangle along the tricuspid annulus in all patients. Application of the current resulted in selective ablation or modification of both retrograde intermediate and slow pathway conductions in 20 patients. In two patients retrograde fast pathway conduction was also modified. Complete atrioventricular block occurred in the remaining patient. Sixteen patients had no induction of tachycardia or echo, 4 had induction of a single echo, and 2 had induction of the slow-fast form tachycardia; one of those 2 patients underwent a second trial and was successful. A median application of 2 was delivered at a power of 25 +/- 5 W and a duration of 18 +/- 4 sec. The total fluoroscopic time was 25 +/- 21 minutes. The anterograde fast pathway conduction was unaffected; the shortest atrial paced cycle length that sustained 1:1 fast pathway conduction was 329 +/- 65 msec and 330 +/- 68 msec before and after ablation, respectively. A follow-up electrophysiologic study was performed in 16 patients 60 +/- 15 days after ablation. Eleven had no induction of tachycardia or echo, and five had induction of < 3 echoes. This study demonstrated that radiofrequency ablation with the inferior approach is effective and safe in atypical or multiple atrioventricular node reentry tachycardias. It resulted in ablation of the slow pathway and retrograde intermediate pathway conduction with preserved atrioventricular conduction.

Evolving concepts in radiofrequency catheter ablation of atrioventricular nodal reentry tachycardia

Our results and those of others (Table I) suggest that both anatomic and electrogram (potential) approaches are highly successful in eliminating AVNRT. The use of slow-pathway potentials appears to minimize lesion delivery and to be associated with a very small likelihood of complete AV block. Approaches aimed directly at the midseptum also appear to reduce lesion delivery. It is important, however, to understand that the fast and slow AV-nodal pathways are not always confined to anterosuperior (fast) and posteroinferior (slow) locations (at least as they are determined fluoroscopically). On occasion, the slow pathway may be ablated anteriorly and the fast pathway posteriorly. Our three inadvertent successful fast-pathway ablations support these findings. We prefer to conceptualize the AV node as having three ablation zones. Ablation in the anterosuperior zone most often affects fast-pathway conduction; ablation in the posteroinferior zone most often affects slow pathway conduction; and ablation in the midseptal region predominantly affects slow-pathway conduction. Lesions applied to the midseptum do, however, appear more likely to affect inadvertently the fast (or both) pathway(s), probably because of the anatomic convergence of the posteroinferior and anterosuperior AV-nodal approaches in this region. A preliminary report by Wu et al. supports this three-zone concept. The subsequent larger series reported by this group has raised concern that midseptal approaches may be associated with too great a risk of complete AV block. On the other hand, approaches guided exclusively by potentials may be associated with much longer procedure times. Controversy exists over the acceptable end point for ablation procedures. We have not found it necessary routinely to eliminate dual-nodal conduction to maintain a low (3.2%) overall recurrence rate. Aggressive attempts to eliminate all evidence of slow-pathway conduction must be balanced against the risk of inadvertent complete AV block. In conclusion, cumulative data and our clinical experience with ablation of AVNRT suggest that it is possible to be both pragmatic and highly successful. The key components of our approach are (1) an anatomically based, systematic, time-limited search for potentials; (2) elimination of unnecessary lesions that are too atrial or too ventricular to involve the reentrant circuit; (3) a caudocephalad approach that avoids excessively anterior initial lesions, which may result in inadvertent complete AV block; and (4) avoidance of unnecessary lesions in the most inferoposterior sector, which results in patient discomfort and low clinical efficacy. This approach is safe (with minimal risk of AV block), reproducible, and efficacious.

Late clinical and electrophysiologic outcome of radiofrequency ablation therapy by the inferior approach in atrioventricular node reentry tachycardia

A late electrophysiologic study was conducted in 182 of 289 patients with slow-fast atrioventricular node reentry tachycardia 81 +/- 36 days after radiofrequency ablation therapy by the inferior approach. Of these 182 patients, electrophysiologic study immediately after ablation revealed a selective modification of the slow pathway in 159, a modification of both the slow and fast pathways in 15, a modification of the fast pathway alone in 3, and failure of ablation in 5. One hundred two patients had no induction of echoes; 75 had induction of fewer than four echoes; and 5 had induction of sustained tachycardia with or without isoproterenol infusion. The late electrophysiologic study in these 182 patients revealed a persistent effect without changes in conduction properties in 161 (88%) patients. A change in conduction properties was noted in 21 patients, including 5 with resumption of slow- or fast-pathway conduction with induction of sustained tachycardia, 8 with improved fast- or slow-pathway conduction, and 8 with an additional depression of fast- or slow-pathway conduction. Of the 102 patients with no induction of echoes and the 75 patients with induction of fewer than four echoes during the immediate postablation electrophysiologic study, 5 (3 and 2, respectively) patients had induction of tachycardia. Of the 5 patients with induction of sustained tachycardia in the immediate postablation electrophysiologic study, 3 continued to have induction of sustained tachycardia; 1 had induction of echoes only; and 1 had no induction of echoes.(ABSTRACT TRUNCATED AT 250 WORDS)

NASPE Young Investigator Awardee-1993. Computer model of the atrioventricular node predicts reentrant arrhythmias

INTRODUCTION

Following atrial premature beats, the AV node may exhibit sustained reentrant tachyarrhythmias, isolated echo beats, or discontinuities in the recovery curve (the plot of conduction time versus atrial cycle length). A computer model was used to examine the hypothesis that spatial variation of AV nodal passive electrical resistance may account for these phenomena.

METHODS AND RESULTS

A computer model of a rectangular lattice of electrotonically linked elements whose ionic kinetics simulated nodal ionic flux was developed. The model showed that there exists a resistance value that minimizes the effective refractory period, because high resistance prevents depolarization of distal elements, while low resistance allows leakage of depolarizing current by electrotonic transmission, preventing activation of proximal elements. High resistances stabilized reentry by slowing conduction. Simulations incorporating equal resistance values between elements predicted increased AV nodal conduction times with increasing prematurity of atrial impulses. A model with a gradual change in resistance between fibers produced discontinuities and tachycardia, but not both simultaneously. Uniform anisotropy produced preferential transverse block, leading to echo beats and "fast-slow" tachycardia, but not recovery curve discontinuities. Nonuniform anisotropy could produce reentry, but tachycardia often occurred without discontinuities. Dividing the lattice into two electrotonically linked parallel pathways with different resistance values ("dual pathway model") predicted recovery curve discontinuities, echo beats, and tachycardia. At critical atrial cycle lengths, only the (high resistance) slow pathway conducted antegradely, while the fast pathway conducted retrogradely, to generate the typical "slow-fast" tachycardia. Responses of the dual pathway model to ablation were consistent with clinical data, including the previous observation of a decrease in fast pathway effective refractory period after slow pathway ablation.

CONCLUSION

Differences in passive electrical resistance of electronically linked dual pathways within the AV node may account for functional longitudinal dissociation, reentrant arrhythmias, and responses to catheter ablation therapy.

Double loop figure-of-8 reentry as the mechanism of multiple atrioventricular node reentry tachycardias

Seven patients with multiple atrioventricular node reentry tachycardia were analyzed to unravel the mechanism of these tachycardias. Six of the seven patients showed anterograde dual atrioventricular node pathways and one showed anterograde conduction through the fast pathway. Three types of retrograde pathways were noted among these seven patients: (1) the fast pathway with the earliest atrial activation at the His bundle area; (2) the intermediate pathway with the earliest atrial activation at the ostium of the coronary sinus; and (3) the slow pathway with the earliest atrial activation at the ostium of the coronary sinus. All seven patients used the intermediate pathway for retrograde conduction. However, one patient showed evidence of retrograde slow pathway conduction with demonstrable retrograde dual pathways, and another showed evidence of retrograde fast pathway conduction with a shift of atrial activation sequence when conduction switched to the intermediate pathway. Four different types of reentry circuits using either the fast or the slow pathway as the anterograde limb and one of the three retrograde pathways as the retrograde limb were demonstrated in these seven patients, resulting in two types of tachycardias in four patients and three types of tachycardias in three patients. A change in tachycardia type could be induced with atrial or ventricular stimulation. A radiofrequency current delivered to the inferior aspect of Koch's triangle along the tricuspid anulus in five patients resulted in selective ablation or modification of the intermediate pathway or the slow pathway, with preservation of anterograde atrioventricular conduction and abolition of tachycardias. The findings suggest that a double loop figure-of-8 reentry circuit including a fast pathway, a slow pathway, and an intermediate pathway is responsible for multiple atrioventricular node reentry tachycardias.

Junctional tachycardia: a useful marker during radiofrequency ablation for atrioventricular node reentrant tachycardia

OBJECTIVES

The aim of this study was to evaluate junctional tachycardia as a useful marker during radiofrequency ablation for atrioventricular (AV) node reentrant tachycardia.

BACKGROUND

Junctional tachycardia appears to be a response of the atrioventricular node to injury and is seen during both radiofrequency AV node ablation and slow and fast pathway ablation for AV node reentrant tachycardia. We hypothesized that junctional tachycardia heralding AV node block and that associated with slow or fast pathway ablation may have different characteristics that could be useful in preventing inadvertent AV block.

METHODS

Characteristics of junctional tachycardia were examined after 59 radiofrequency ablation sessions in 53 consecutive patients with a mean age (+/- SD) of 41.6 +/- 16.5 years. Type 1 junctional tachycardia was followed by transient second- or third-degree AV block (n = 5) or permanent third-degree AV block (n = 1). Type 2 junctional tachycardia was followed by normal AV conduction (n = 53).

RESULTS

Fifty-one patients had typical AV node reentrant tachycardia, and two patients had atypical tachycardia. Fast pathway ablation was attempted during 6 sessions and slow pathway ablation during 53 sessions. Patients underwent 15.3 +/- 10 radiofrequency applications, with a mean duration of 24 +/- 9.7 s. Junctional tachycardia was observed an average of 2.8 +/- 1.8 times per ablation session. Type 1 junctional tachycardia had a significantly faster rate than that of type 2 (cycle length 363 +/- 44 vs. 558 +/- 116, p < 0.001). In addition, type 1 junctional tachycardia was associated with predominantly ventriculoatrial block whereas type 2 was associated with predominantly 1:1 ventriculoatrial conduction (2 of 6 vs. 47 of 53 episodes, p < 0.05).

CONCLUSIONS

We conclude that junctional tachycardia leading to AV block can be recognized by a faster junctional rate and ventriculoatrial block. This is a useful marker of impending AV block during slow and fast pathway ablation.

Morphology of the cardiac conduction system in patients with electrophysiologically proven dual atrioventricular nodal pathways

INTRODUCTION

Although the electrophysiologic criteria for dual atrioventricular nodal pathways are well established, the anatomical substrate is still unclear.

METHODS AND RESULTS

We examined the hearts from 10 patients who had been studied electrophysiologically prior to cardiac transplantation. All 10 patients were male, aged 22 to 60 years. Nine of the 10 patients had dual atrioventricular nodal pathways according to accepted criteria. Histologic studies of the atrioventricular conduction system showed normal structure of the atrioventricular node in all 10 hearts, with minor variations within the node in 3 cases, within the penetrating bundle in 3 cases, and within the nonbranching bundle in 3 cases. The atrial approaches to the atrioventricular node were generally scanty in 6 hearts. The solitary case that was shown electrophysiologically to lack dual pathways had no obvious difference in the structure of the nodal area other than sparsity of transitional cells. We were unable to locate any extranodal atrial tracts as described by other investigators.

CONCLUSION

The anatomical substrate for conduction over dual pathways may be too subtle to be detected by gross morphologic studies. Since dual pathways were unmasked in all patients but one during electrophysiologic studies, it may be that the potential for these pathways is ubiquitous.

Interventional electrophysiology--state-of-the-art 1993

The field of clinical electrophysiology has broadened significantly in the last several years, spawning a new discipline known as Interventional or Therapeutic Electrophysiology. In the United States, Electrophysiology has its own training path and accreditation requirements. One of the reasons for the growth of interest in electrophysiology is the exciting introduction of nonpharmacologic methods of arrhythmia therapy, including curative radiofrequency catheter ablation and implanted devices for antitachycardia pacing/defibrillation. The arrhythmia specialist now has at his/her disposal a wide range of options for patients with symptomatic or life-threatening cardiac arrhythmias.

A simple technique for selective radiofrequency ablation of the slow pathway in atrioventricular node reentrant tachycardia

OBJECTIVES

A simple technique was designed for radiofrequency ablation therapy of atrioventricular (AV) node reentrant tachycardia.

BACKGROUND

This technique was based on the hypothesis that slow pathway conduction reflects conduction through the compact node and its posterior atrial input.

METHODS

A total of 100 consecutive patients were studied; there were 37 men and 63 women, with a mean age of 48 +/- 15 years. All 100 patients had induction of sustained tachycardia with (51 patients) or without (49 patients) administration of isoproterenol or atropine, or both. The ablation catheter was initially manipulated to record the largest His bundle deflection from the apex of Koch's triangle. It was then curved downward and clockwise to the area of the compact node when His deflection was no longer visible and the ratio of atrial to ventricular electrogram was < 1. The radiofrequency current was delivered from the 4-mm tip electrode a mean of 5 +/- 7 times at a power of 25 +/- 4 W for a duration of 21 +/- 4 s. The total fluoroscopic time was 19 +/- 11 min.

RESULTS

Selective ablation (56 patients) or modification (26 patients) of the slow pathway without affecting anterograde and retrograde fast pathway conduction was achieved in 82 patients. Ablation or modification of both the retrograde fast pathway and the slow pathway but with preservation of anterograde fast pathway conduction was noted in 12 patients. Ablation or modification of the retrograde fast pathway alone or both anterograde and retrograde fast pathway conduction was noted in three patients. Complete AV node block occurred in three patients. Seventy-three patients had no induction of echo beats or tachycardia and 24 patients had induction of a single echo beat after ablation. Follow-up study was performed in 62 patients 76 +/- 18 days after ablation. Thirty-nine patients had no induction of echo beats or tachycardia, 22 had induction of echo beats alone and 1 patient had induction of sustained tachycardia.

CONCLUSION

Selective ablation of the slow AV node pathway can be achieved by a simple procedure with a high success rate and few complications.

Catheter radiofrequency ablation of slow pathway in patients with atrioventricular nodal re-entrant tachycardia

Selective ablation of slow pathway by radiofrequency current in 12 patients with atrioventricular (AV) nodal dual pathway and tachycardia was performed in our section. A large-tip ablation catheter was positioned around the ostium of the coronary sinus. The slow pathways of all the 12 patients were abolished permanently. Both the antegrade and retrograde conduction of fast pathway was not affected. There was no recurrence after 178 days follow-up.