Percutaneous catheter modification of the atrioventricular node. A potential cure for atrioventricular nodal reentrant tachycardia

Antegrade slow pathway mapping of typical atrioventricular nodal reentrant tachycardia based on direct slow pathway capture

BACKGROUND

Radiofrequency (RF) ablation of typical atrioventricular nodal reentrant tachycardia (tAVNRT) is performed without revealing out the location of antegrade slow pathway (ASp). In this study, we studied a new electrophysiological method of identifying the site of ASp.

METHODS

This study included 19 patients. Repeated series of very high-output single extrastimulations (VhoSESts) were delivered at the anatomical slow pathway region during tAVNRT. Tachycardia cycle length (TCL), coupling interval (CI), and return cycle (RC) were measured and the prematurity of VhoSESts [ΔPM (= TCL - CI)] and the prolongation of RCs [ΔPL (= RC - TCL)] were calculated. Pacing sites were classified into two categories: (i) ASp capture sites [DSPC(+) sites], where two different RCs were shown, and ASp non-capture sites [DSPC(-) sites], where only one RC was shown. RF ablation was performed at DSPC(+) sites and/or sites with catheter-induced mechanical trauma (CIMT) to ASp.

RESULTS

DSPC(+) sites were shown in 13 patients (68%). RF ablation was successful in all patients without any degree of atrioventricular block nor recurrence. Total number of RF applications was 1.8 ± 1.1. Minimal distance between successful ablation sites and DSPC(+)/CIMT sites and His bundle (HB) electrogram recording sites was 1.9 ± 0.8 mm and 19.8 ± 6.1 mm, respectively. ΔPL of more than 92.5 ms, ΔPL/TCL of more than 0.286, and ΔPL/ΔPM of more than 1.565 could identify ASp with sensitivity of 100%, 91.1%, and 88.9% and specificity of 92.9%, 97.0%, and 97.6%, respectively.

CONCLUSIONS

Sites with ASp capture and CIMT were close to successful ablation sites and could be useful indicators of tAVNRT ablation.

Recurrent single echo beats after cryoablation of atrioventricular nodal reentrant tachycardia: The pediatric population

BACKGROUND

Cryoablation for atrioventricular nodal reentrant tachycardia (AVNRT) is effective and safe with a reported limitation of lower success and higher recurrence rates. We have observed cases in which slow pathway conduction was eliminated as demonstrated by atrial extra-stimulus testing within 1 min of cryo-energy delivery but returned following tissue rewarming. Frequently, slow pathway conduction persisted despite multiple acutely successful lesions over a broad anatomic region. We aimed to determine if return of slow pathway conduction after elimination during cryoablation represents a risk for recurrent AVNRT with the same intermediate term results as slow pathway ablation. We hypothesize that remnant single echo beats in the absence of sustained slow pathway conduction and inducible AVNRT is an acceptable end point after clear slow pathway elimination during cryoablation.

METHODS

Retrospective chart review of patients undergoing attempted slow pathway ablation for AVNRT using solely cryoablation between January 2015-January 2018.

RESULTS

Forty-four patients met inclusion criteria with at-least 2 features of dual AVN physiology. 19 patients had return of slow pathway conduction shortly after clear elimination during cryoablation (Group A) while 25 did not (Group B). All in Group A had recurrent single echo beats but none had sustained slow pathway conduction at the end of the procedure nor AVNRT recurrence at 1 year.

CONCLUSION

Recurrent single echo beats with absent sustained slow pathway conduction and non-inducible AVNRT may be an acceptable endpoint for slow pathway ablation of AVNRT using cryoablation when there is elimination of slow pathway demonstrated during energy delivery.

Patients' and procedural characteristics of AV-block during slow pathway modulation for AVNRT-single center 10year experience

BACKGROUND

Permanent AV-block is a recognized and feared complication of slow pathway modulation for AVNRT. We aimed to assess incidence of transient and permanent AV-block as well as consequences of transient AV-block in a large contemporary AVNRT ablation cohort.

METHODS

We searched our single center prospective ablation database for occurrence of transient and permanent AV-block during slow pathway modulation between January 2004 and October 2015. We analyzed patients' and procedural characteristics as well as outcome of patients in whom transient or permanent AV-block occurred.

RESULTS

Of 9170 patients who underwent a catheter ablation at our institution between January 2004 and October 2015, 2101 patients (64% women, mean age 50±18years) underwent slow pathway modulation. In three patients, permanent AV-block occurred during RF application. Additional two patients had transient AV-block that recovered (after a few minutes and 25min), but recurred within two days of the procedure. All five patients underwent dual chamber pacemaker implantation (0.2%). Transient AV-block related to RF delivery occurred in 44 patients (2%). Transient mechanical AV-block occurred in additional 17 patients (0.8%). In 12 patients, ablation was continued despite transient AV-block. One of these patients developed permanent AV-block.

CONCLUSION

Permanent AV-block following slow pathway modulation is a rare event, occurring in 0.2% of patients in a large contemporary single center cohort. Transient AV-block is more frequent (2%).

How to Approach Difficult Cases of AVNRT

OPINION STATEMENT

Our approach to the ablation of atrioventricular nodal reciprocating tachycardia (AVNRT), the most common supraventricular tachycardia, is as follows: We first attempt ablation in the right atrial posteroseptum anterior to the coronary sinus ostium with a 4-mm non-irrigated tip catheter. If ablation within the triangle of Koch is unsuccessful with radiofrequency (RF), we switch to cryoablation and target a more superior (mid septal) region. We also utilize cryoablation if RF ablation produces transient VA block (absence of retrograde conduction during junctional rhythm) or a fast junctional rhythm (<350 msec). If cryoablation were to fail, or is not available, we would then suggest ablation within the coronary sinus targeting the roof (2-4 cm from the os) using a 3.5-mm irrigated tip catheter. If tachycardia were still inducible despite these measures, we would then proceed with transseptal puncture (given our greater experience with this over a retrograde aortic approach) and perform RF ablation along the posteroseptal left atrium and inferoseptal mitral annulus utilizing an irrigated tip catheter. In our experience, cryoablation reliably results in elimination of the slow pathway. The only left atrial ablation for AVNRT at our institution in the past year was performed because a patent foramen ovale allowed for rapid left atrial access, facilitating left atrial ablation of the slow pathway.

Cryoablation Versus Radiofrequency Ablation in AVNRT: Same Goal, Different Strategy

Catheter ablation is nowadays the first therapeutic option for AVNRT, the most common benign supraventricular tachycardia. Both cryotherapy and radiofrequency energy may be used to ablate the slow pathway. This paper compares both techniques, evaluates results published in literature and gives feedback on some typical aspects of cryo- and RF ablation. Although both techniques have satisfying success rates in AVNRT ablation, with a higher safety profile of cryoablation towards creation of inadvertent atrioventricular block, it remains paramount that the operator respects the distinctive traits of each technique in order to obtain an optimal result in every patient.

Paroxysmal Supraventricular Tachycardia: A Century of Progress

This article reviews progress in the understanding of AV junctional reentrant tachycardia and accessory pathway-mediated tachycardia in the twentieth century and in the early part of the twenty-first century. Emphasis is placed on the contributions of John Uther and the department he founded at Westmead Hospital.

Atrioventricular nodal reentrant tachycardia associated with idiopathic ventricular tachycardia: clinical and electrophysiologic characteristics

BACKGROUND

Case reports have described the coexistence of ventricular tachycardia (VT) and supraventricular tachycardia in the same patient. This study examines the frequency of dual atrioventricular nodal (AVN) physiology, AVN echo beats, and atrioventricular nodal reentrant tachycardia (AVNRT) in patients with VT.

METHODS

Programmed atrial and ventricular stimulation was performed in 132 consecutive patients referred for electrophysiologic study of symptomatic VT. Of the 132, 99 patients had structural heart disease, and 33 patients had idiopathic ventricular tachycardia (IVT).

RESULTS

Among the 33 patients with IVT, 23 had dual AVN physiology. Compared with patients with structural heart disease undergoing VT ablation, dual AVN pathways (70% vs 27%, P < .0001), dual AVN pathways with echo beats (24% vs 8%, P = 0.03), and AVNRT (21% vs 1%, P = .0002) were more common in patients with IVT.

CONCLUSION

Dual AVN physiology and AVNRT appear to be associated with IVT. This finding suggests that patients with IVT should undergo a complete electrophysiologic evaluation, and the diagnosis of coexistent AVNRT should be considered in this population.

The history of AV nodal reentry

Though patients with AV nodal reentry are now routinely cured by catheter ablation, the basic mechanism of this disorder is still under debate. The putative mechanism of AV node reentry was first discovered by the elegant work of Gordon Moe. He demonstrated the existence of dual pathways and echo beats in rabbits. Building on these seminal observations, the mechanism of AVNRT has burgeoned to include the possibility of left atrial input into the node. The first curative nonpharmacologic procedures involved surgical dissection around the AV node and the procedure was rapidly supplanted by catheter ablation procedures. The initial ablative procedure targeted the fast pathway, but later observations showed that ablation of the slow pathway was more effective and safer. Cure of AV nodal reentry which is the most common cause of paroxysmal supraventricular tachycardia became possible through the cooperative efforts of anatomists, physiologists, surgeons, and clinical electrophysiologists.

History of arrhythmias

A historical overview is given on the techniques to record the electrical activity of the heart, some anatomical aspects relevant for the understanding of arrhythmias, general mechanisms of arrhythmias, mechanisms of some specific arrhythmias and nonpharmacological forms of therapy. The unravelling of arrhythmia mechanisms depends, of course, on the ability to record the electrical activity of the heart. It is therefore no surprise that following the construction of the string galvanometer by Einthoven in 1901, which allowed high-fidelity recording of the body surface electrocardiogram, the study of arrhythmias developed in an explosive way. Still, papers from McWilliam (1887), Garrey (1914) and Mines (1913, 1914) in which neither mechanical nor electrical activity was recorded provided crucial insights into re-entry as a mechanism for atrial and ventricular fibrillation, atrioventricular nodal re-entry and atrioventricular re-entrant tachycardia in hearts with an accessory atrioventricular connection. The components of the electrocardiogram, and of extracellular electrograms directly recorded from the heart, could only be well understood by comparing such registrations with recordings of transmembrane potentials. The first intracellular potentials were recorded with microelectrodes in 1949 by Coraboeuf and Weidmann. It is remarkable that the interpretation of extracellular electrograms was still controversial in the 1950s, and it was not until 1962 that Dower showed that the transmembrane action potential upstroke coincided with the steep negative deflection in the electrogram. For many decades, mapping of the spread of activation during an arrhythmia was performed with a "roving" electrode that was subsequently placed on different sites on the cardiac surface with a simultaneous recording of another signal as time reference. This method could only provide reliable information if the arrhythmia was strictly regular. When multiplexing systems became available in the late 1970s, and optical mapping in the 1980s, simultaneous registrations could be made from many sites. The analysis of atrial and ventricular fibrillation then became much more precise. The old question whether an arrhythmia is due to a focal or a re-entrant mechanism could be answered, and for atrial fibrillation, for instance, the answer is that both mechanisms may be operative. The road from understanding the mechanism of an arrhythmia to its successful therapy has been long: the studies of Mines in 1913 and 1914, microelectrode studies in animal preparations in the 1960s and 1970s, experimental and clinical demonstrations of initiation and termination of tachycardias by premature stimuli in the 1960s and 1970s, successful surgery in the 1980s, the development of external and implantable defibrillators in the 1960s and 1980s, and finally catheter ablation at the end of the previous century, with success rates that approach 99% for supraventricular tachycardias.

Catheter Ablation Therapy for Atrial Fibrillation

Since cases were first reported in 1994, catheter ablation of atrial fibrillation has undergone rapid development and expansion. The procedure began as an attempt to recreate the Maze III operation with a catheter technique. Understanding the contribution of the pulmonary veins to the initiation and maintenance of atrial fibrillation led to dramatic changes in procedural technique. The segmental ostial and the circumferential approaches have emerged as the 2 dominant methods. Efforts continue in academic centers to better understand the pathophysiology of the arrhythmia and to further refine the ablation procedure to improve patient outcomes.

Outcomes of radiofrequency catheter ablation of atrioventricular reciprocating tachycardia in patients with congenital heart disease

OBJECTIVES

Assessment of clinical outcomes of catheter ablation of atrioventricular reciprocating tachycardias in patients with congenital heart disease (CHD).

BACKGROUND

Atrioventricular reciprocating tachycardias occur in patients with CHD and may be poorly tolerated.

METHODS

Retrospective review of all 105 such ablations in 83 patients performed between 03/90 and 02/02 at one institution.

RESULTS

The dominant arrhythmia mechanism was accessory pathway (70 patients, 84%), and the most common indications were drug-refractory tachycardia, life-threatening arrhythmia, and elective presurgical ablation. Congenital heart disease diagnoses were diverse, with one third of patients having Ebstein's anomaly. Twenty patients (24%) had catheter access limited by prior surgeries or occluded vascular access. Of 109 accessory pathways (APs), 74 (68%) were manifestly preexcited, and 71 (65%) were located on the right atrioventricular groove. Fourteen patients (20%) had multiple pathways. There were 2 major complications (1 death, 1 hemorrhage), and 3 minor complications (5.5% of procedures). Acute success rate was 80% per procedure, 82% for left- and 70% for right-sided APs. Acute success rates for patients with Ebstein's anomaly were similar to patients with other CHD diagnoses, but Ebstein's patients were more likely to have recurrence. At 44 +/- 35 months follow-up, successful ablation was achieved in 59% of procedures and 68% of patients, with 19 patients (23%) undergoing one or more repeat ablations.

CONCLUSIONS

Compared to patients with normal cardiac anatomy, patients with CHD of all varieties have lower rates of acute and long-term success for ablation for atrioventricular reciprocating tachycardias.

Role of Compact Node and Posterior Extension in Direction-Dependent Changes in Atrioventricular Nodal Function in Rabbit

INTRODUCTION

AV nodal conduction properties differ in the anterograde versus the retrograde direction. The underlying substrate remains unclear. We propose that direction-dependent changes in AV nodal function are the net result of those occurring in the slow and fast pathways.

METHODS AND RESULTS

Anterograde and retrograde AV nodal properties were determined with a premature protocol before and after posterior extension (slow pathway) ablation, and before and after upper compact node (fast pathway) ablation. Each ablation was performed in a different group of six rabbit heart preparations. In control, nodal minimum conduction time (NCTmin) and effective refractory period (ERPN) typically were longer, and maximum conduction time (NCTmax) was shorter in the retrograde compared to the anterograde direction. Posterior extension ablation prolonged anterograde ERPN from 91 +/- 10 ms to 141 +/- 15 ms (P < 0.01) and shortened NCTmax from 150 +/- 13 ms to 82 +/- 7 ms (P < 0.01) but did not affect retrograde conduction. Thus, the posterior extension normally contributes to the anterograde but not retrograde recovery curve. Compact node ablation prolonged anterograde conduction (NCTmin increased from 57 +/- 2 ms to 73 +/- 7 ms, P < 0.01) but did not alter ERPN and NCTmax. This ablation abolished retrograde conduction in two preparations and resulted in retrograde slow pathway conduction in four, the latter being interrupted by posterior extension ablation. Thus, the compact node accounts for the baseline of the recovery curve in both directions. Ablation of the compact node results in anterograde slow pathway conduction over the entire cycle length range and may result in retrograde slow pathway conduction.

CONCLUSION

Direction-dependent properties of the AV node arise from those of the compact node-based fast pathway and posterior extension-based slow pathway. Normal AV node has bidirectional dual pathways.

Role of the compact node and its posterior extension in normal atrioventricular nodal conduction, refractory, and dual pathway properties

INTRODUCTION

The functional origin of AV nodal conduction, refractory, and dual pathway properties remains debated. The hypothesis that normal conduction and refractory properties of the compact node and its posterior nodal extension (PNE) play a critical role in the slow and the fast pathway, respectively, is tested with ablation lesions targeting these structures.

METHODS AND RESULTS

A premature atrial stimulation protocol was performed before and after PNE ablation in six isolated rabbit heart preparations. Discrete (approximately 300 microm) histologically controlled PNE lesions amputated the AV nodal recovery curve from its left steep portion reflecting slow pathway conduction and prevented reentry without affecting the right smooth fast pathway portion of the curve. The ablation shortened A2H2max from 159 +/- 16 ms to 123 +/- 11 msec (P < 0.01) and prolonged the effective refractory period from 104 +/- 6 msec to 119 +/- 11 msec (P < 0.01) without affecting A2H2min (55 +/- 9 msec vs 55 +/- 8 msec; P = NS) and functional refractory period (174 +/- 7 msec vs 175 +/- 6 msec; P = NS). These results did not vary with the input reference used. In six other preparations, lesions applied to the compact node after PNE ablation shifted the fast pathway portion of the recovery curve to longer conduction times and prolonged the functional refractory period, suggesting a compact node involvement in the fast pathway.

CONCLUSION

The normal AV nodal conduction and refractory properties reflect the net result of the interaction between a slow and a fast pathway, which primarily arise from the asymmetric properties of the PNE and compact node, respectively.

An overview of contemporary approaches to antiarrhythmic therapy

This review discusses the evolution in the approach to the therapy of cardiac arrhythmias that has occurred during the past 2 decades. The major changes have been driven by advances in understanding arrhythmia mechanisms, in bioengineering, and in clinical trials. It seems likely that progress in understanding the cellular and molecular basis of arrhythmias and their response to drug therapy may allow further identification of patient subsets in which specific therapies are indicated or contraindicated.

Characteristics, circuit, mechanism, and ablation of reentry in the rabbit atrioventricular node

INTRODUCTION

The circuitry underlying AV nodal reentry remains debated. We developed a model of AV nodal reentry and assessed the role of nodal inputs, compact node, and its posterior nodal extension (PNE) in this phenomenon.

METHODS AND RESULTS

A fine scanning of short coupling interval range with an atrial premature beat consistently initiated slow-fast AV nodal reentrant beats that occurred 37+/-31 msec (mean+/-SD) after His-bundle activation in 11 of 16 consecutive rabbit heart preparations. The repeated testing (>40 times) of a chosen coupling interval within reentry window (6+/-9 msec, n = 11) yielded reentrant intervals that varied by 2+/-1 msec (mean SD for 40 beats+/-SD, n = 11). The breakthrough point of reentrant activation, as assessed from four perinodal sites, varied in different preparations from diffuse (4) to anterior (1), medial (3), or posterior (3); mean reentrant interval did not differ between perinodal sites. Antegrade perinodal activation pattern did not differ at reentrant versus nonreentrant coupling intervals and thus was not a primary determinant of reentry. A PNE ablation (n = 4) interrupted the slow pathway conduction and prevented reentry without affecting antegrade perinodal activation or fast pathway conduction.

CONCLUSION

A reproducible model of AV nodal reentrant beats was developed and used to study underlying circuitry. The AV nodal reentry involves unaltered antegrade perinodal activation, slow PNE conduction and retrograde broad invasion of perinodal tissues starting at a preparation-dependent breakthrough point. A PNE ablation abolishes the reentry.

Low temperature and low energy radiofrequency modification of atrioventricular nodal slow pathways in pediatric patients

OBJECTIVES

To report our experience using low temperature and energy in the modification of the slow pathway in pediatric patients with atrioventricular nodal reentrant tachycardia.

BACKGROUND

A concern in performing a slow pathway modification is the possible damage of the normal AV conduction system. Lesion size has been shown to have a linear relationship with temperature. Previous reports have used energy of 25-50 W that generate temperatures of 60 degrees C -70 degrees C for successful procedures.

METHODS

Report of results of attempted AV nodal slow pathway modification in 17 consecutive pediatric patients < 15 years of age at The Children's Hospital of Philadelphia from April 1995 to November 1997 using low temperature and energy.

RESULTS

There were 18 successful slow pathway modifications with 1 recurrence in 17 patients. The maximum energy used during successful lesions was 32.7 +/- 13.8 W (range 15-50 W) with a mean energy of 26.4 +/- 13.3 W (range 12-48 W). The peak temperature during these lesions was 55.1 degrees C +/- 4.1 degrees C (range 48 degrees C-64 degrees C) with a mean temperature of 47.9 degrees C +/- 2.7 degrees C (range 44 C-540C). The mean number of radiofrequency lesions required for a successful modification was 5.8 +/- 6.7 (median 4.0, range 1-26). Patients have been followed for 2.08 +/- 0.79 years.

CONCLUSIONS

Slow pathway modification can be performed successfully with a low incidence of recurrence in the pediatric patient using low energy and temperature. It is possible that this may lead to smaller lesions.

Presence and significance of the left atrionodal connection during atrioventricular nodal reentrant tachycardia

It has been suggested that the anatomic substrates of dual atrioventricular nodal pathways are likely to be the atrionodal connections. During atrioventricular nodal re-entrant tachycardia (AVNRT) or ventricular pacing (VP), an earliest retrograde atrial activation in the coronary sinus (CS) distal to the ostium (CS breakthrough) would suggest the presence of an exit from a left atrionodal connection. The aim of the study was to evaluate the incidence of such an atrial retrograde activation in the CS during AVNRT and VP. The retrograde atrial activation was recorded during typical AVNRT (38 patients, 27 women, mean age 44 +/- 18 years) by a multipolar catheter in the CS, a decapolar catheter in the His bundle position, and a deflectable quadripolar catheter along the tricuspid annulus anterior to the CS ostium. In 31 patients the retrograde atrial activation was recorded also during VP at a similar cycle length. A CS breakthrough was found in 18 patients during AVNRT (47%) and in 13 patients during VP (42%). Presence or absence of CS breakthrough was concordant between AVNRT and VP in 90% of the patients. A CS breakthrough, suggesting a left-sided atrionodal connection, is frequently recorded both during AVNRT and VP. In patients with a CS breakthrough pattern, the absence of correlation between the His bundle to the earliest CS retrograde atrial electrogram interval and AVNRT cycle length, or any other atrial activation times recorded in the posterior and anterior region of the Koch's triangle, would suggest that the left-sided atrionodal connection is a bystander during typical AVNRT.

Electrophysiologic characteristics of different ectopic rhythms during slow pathway ablation in patients with atrioventricular nodal reentrant tachycardia

The presence of ectopic rhythm has been considered to be the most important marker for successful slow pathway ablation, but the details of different ectopic rhythms have not been well described. This study included 83 consecutive patients with typical AV node reentrant tachycardia who underwent slow pathway ablation. The interval between the atrial signals of the His bundle electrogram and the distal ablation catheter [A(H)-A(Ab)], and the interval between the atrial components of the distal ablation catheter and the ostium of coronary sinus catheter [A(Ab)-A(CSos)] were measured. One hundred episodes of ectopic rhythm occurred with 81 (81%) successful applications. There are two different origins and three activation sequences of ectopic rhythms, including HIS rhythm (78 applications, the earliest atrial activation in the His bundle electrogram), CSos rhythm (6 applications, the earliest atrial signal in the coronary sinus ostium electrogram) and CSos preceding HIS (CSos-->HIS) rhythm (16 applications, the atrial activation sequences changing from CSos to HIS rhythm). The CSos rhythm had a shorter mean cycle length (445 +/- 81 vs. 511 +/- 132 vs. 579 +/- 140 ms, p < 0.05), a shorter [A(Ab)-A(CSos)] interval (-2.5 +/- 9.8 vs. 14.1 +/- 11.2 vs. 12.8 +/- 8.4 ms, p < 0.05) and a lower success rate (33% vs. 84% vs. 94% p < 0.05) than HIS rhythm and CSos-->HIS rhythm. Otherwise, the mean cycle length of ectopic rhythm was significant shorter in successful than in failed ablation (506 +/- 135 vs. 559 +/- 118 ms, p = 0.04). In conclusion, we found two different origins and three activation sequences of ectopic rhythms. CSos rhythm had a lower success rate in ablation of slow pathway, thus it was a poor marker for successful ablation.

Catheter ablation for atrioventricular nodal reentrant tachycardia

The current status of catheter ablation techniques for the management of atrioventricular nodal reentry tachycardia is outlined in this article. Some pertinent aspects of the atrioventricular nodal anatomy and physiology are discussed, to the extent that they are essential for understanding of the mechanism of this arrhythmia and the technique of catheter ablation.

Origin of junctional rhythm during radiofrequency ablation of atrioventricular nodal reentrant tachycardia in patients without structural heart disease

Junctional rhythm is commonly observed during radiofrequency catheter ablation of the fast or slow pathways of atrioventricular nodal reentrant tachycardia (AVNRT). However, the origin of these beats remains unclear. We analyzed the retrograde atrial activation sequence of 16 patients (mean +/- SD: 41.2 +/- 18.9 years old) undergoing catheter ablation for typical AVNRT with detailed catheter mapping of the triangle of Koch. The earliest atrial activations were concordant during tachycardia and junctional rhythm in only 5 of 16 patients. The findings suggest that junctional rhythm is unlikely to represent direct stimulation of the atrioventricular (AV) node via a discrete slow pathway but rather results from enhanced automaticity from > or =1 sites in the AV nodal transitional zone. The ensuing atrial activation pattern results from anisotropic spread from these sites. In addition, these data imply that the original concept of the AV node comprising 2 anatomically defined pathways may not be valid, and that a functionally defined pathway model may be a more accurate representation.

Driving issues related to arrhythmic syncope

The safety of driving in patients with cardiac arrhythmias is a common concern. Although the risk of driving in these patients cannot be reduced to zero, available data and expert consensus suggest that most patients with arrhythmias can return to driving with a relatively low risk of harm to themselves and others, that is, a risk within the limits deemed acceptable by society. Specific recommendations for allowing patients with various cardiac rhythm abnormalities to drive are reviewed in detail.

Radiofrequency catheter ablation of the anterosuperior and posteroinferior atrial approaches to the AV node for treatment of AV nodal reentrant tachycardia: techniques for selective ablation of "fast" and "slow" AV node pathways

Radiofrequency catheter ablation has been established as a first-line curative treatment modality in patients with symptomatic AV nodal reentrant tachycardia (AVNRT). The successful sites of stepwise catheter ablation approaches of the so-called fast and slow pathways strongly suggest that AVNRT involves the atrial approaches to the AV node. The typical fast pathway ablation sites are located anterosuperior toward the apex of the triangle of Koch, which also contains the compact AV node, whereas the usual slow pathway ablation sites are located posteroinferior toward the base of the triangle of Koch at a greater distance to the compact AV node and bundle of His. Accordingly, ablation studies with large patient cohorts have demonstrated that fast pathway ablation carries a higher risk of inadvertent complete AV block. Thus, the slow pathway is clearly the primary target site, and fast pathway ablation is rarely necessary. Different approaches for slow pathway ablation have been elaborated: anatomically oriented stepwise techniques, ablation guided by double potentials recorded within the area of the slow pathway insertion, and combined techniques. The modern concept of AVNRT suggests that this arrhythmia involves the highly complex three-dimensional nonuniform anisotropic AV junctional area. Accordingly, mapping and ablation studies demonstrated that the anterior approach is not identical with fast pathway ablation, and the posterior approach is not identical with slow pathway ablation. Therefore, it is essential for interventional electrophysiologists to familiarize themselves with the anatomic and electrophysiologic details of this complex and variable specialized AV junctional region. In this review, the anatomic and pathophysiologic aspects of the AV junctional area as they relate to interventional therapy are summarized briefly, and the catheter techniques for ablation of the so-called fast and slow AV nodal pathways for the treatment of AVNRT are described.

Slow AV nodal pathway ablation utilizing a unique temperature controlled radiofrequency energy system

Thirty-nine consecutive patients with symptomatic AV nodal reentrant tachycardia (AVNRT) underwent temperature guided slow AV nodal pathway ablation (group 1). Forty-three consecutive patients undergoing nontemperature guided slow AV nodal pathway ablation late in our experience compose the control population (group 2). Slow pathway ablation was achieved in all patients of both groups. The mean fluoroscopy and ablation times for group 1 were significantly shorter than for group 2 (26.1 +/- 14.9 vs 33.9 +/- 18.9 min, P < 0.05; 19.9 +/- 12.1 vs 30.9 +/- 23.3 min, P < or = 0.02). There were no episodes of coagulum formation in group 1, while there were 15 episodes (7.1% of energy applications) in group 2 (P = 0.0006) despite a significantly higher applied power in group 1 (53.4 +/- 25.1 vs 35.6 +/- 9.5W, P = 0.0001). Successful energy applications were associated with significantly higher temperatures than unsuccessful applications in group 1 (55.6 degrees +/- 5.8 degrees C vs. 52.9 degrees +/- 6.8 degrees C, P < or = 0.03). The minimum temperature required for successful ablation was 48 degrees C for two patients (5%) and was > or = 50 degrees C for the remainder of patients (37/39 [95%]). The catheter ablation system used in this study was safe, effective, and prevented coagulum formation while delivering relatively high power. In addition, shorter ablation times and radiation exposure were seen with this system. Although successful energy applications and the production of junctional rhythm were associated with higher achieved temperatures, temperature alone did not predict either endpoint. Future prospective, randomized trials are needed to confirm these findings and further evaluate the value of temperature monitoring.

Assessment of atrioventricular nodal electrophysiological characteristics after radiofrequency catheter ablation of the slow pathway in atrioventricular nodal reentrant tachycardia--3-month follow up

Radiofrequency catheter ablation of the slow pathway is commonly used to treat atrioventricular (AV) nodal reentrant tachycardia. However, there has been little study of the follow-up assessment of AV nodal physiology. We compared AV nodal electrophysiological characteristics before, immediately after, and again 3 months after successful catheter ablation in 17 patients (mean age 50 +/- 16 years). Sinus cycle length, Wenckebach cycle length, A-H interval at a paced cycle length of 600 ms, effective refractory period and functional refractory period of the fast pathway were significantly changed immediately after catheter ablation, but had recovered 3 months after the procedure. There were no significant differences between the electrophysiological parameters immediately after catheter ablation and those 3 months after the procedure under the intravenous injection of atropine sulfate. We conclude that, due to changes in autonomic nervous tone, AV nodal electrophysiological characteristics are influenced immediately after catheter ablation of the slow pathway in AV nodal reentrant tachycardia.

Selective slow pathway ablation in atrioventricular nodal reentrant tachycardia--comparison of different methods and the site of slow pathway ablation

The optimum potential of the slow pathway (SP) was investigated by determining the effectiveness and safety of high-radiofrequency catheter ablation to treat atrioventricular nodal reentrant tachycardia (AVNRT). The subjects consisted of 29 patients with AVNRT (11 men, with a mean age of 54 +/- 15 years). Three ablation methods were used: a) Method A used the earliest atrial activation site, which is retrograde to the slow pathway, b) Method SP used the SP potential, and c) Method SW, in which ablation was performed stepwise starting from the coronary sinus and moving toward the recording site of the His bundle potential. Five, 20, and 4 patients underwent Methods A, SP, and SW, respectively. The fewest number of applications was needed with Method SP (11 +/- 9, 6 +/- 4, and 13 +/- 9), and the delivered energy was also lowest with Method SP (9151 +/- 6119, 3712 +/- 2168, and 12183 +/- 4090 J, with Methods A, SP, and SW, respectively). In Method SP, the interval between the atrium and SP was significantly longer at sites which cured tachycardia, than at sites at which ablation was ineffective (88 +/- 26 vs 66 +/- 22 msec, p < 0.05). The SP potential showed a humped shape in 18 of 20 patients. Method SP was the most efficient ablation method for treating AVNRT.

Prognostic significance of transient complete atrioventricular block during radiofrequency ablation of atrioventricular node reentrant tachycardia

One hundred eighty-six consecutive patients underwent radiofrequency ablation and were divided into 2 groups: group 1 included 19 patients (13 women, mean age 50 +/- 15 years) with transient atrioventricular (AV) block during the procedure. The duration of AV block ranged from 4 seconds to 30 minutes (mean 2.8 +/- 7.0 minutes); and group 2 included 167 patients (142 women, mean age 40 +/- 17 years) without transient AV block. Follow-up was 8.6 +/- 8.3 months in group 1 and 10.1 +/- 9.4 months in group 2. No significant differences were observed between the 2 groups concerning the ablation approach (fast or slow pathway), the number of radiofrequency applications, and recurrences of tachycardia. Four patients from group 1 who underwent fast pathway ablation developed late complete AV block, whereas no patient in group 2 had such a complication (p = 0.0001). Late complete AV block occurred 20 hours, 6 days, 1 month, and 25 days after ablation, respectively, and was not related to the duration of transient AV block. Another patient from group 1 developed an asymptomatic 2:1 AV block during exercise, 3 months after slow pathway ablation. Transient AV block, a common finding occurring as often during fast as during slow pathway ablation, did not preclude recurrences of tachycardia but was associated with late complete AV block.

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.

A direct midseptal approach to slow atrioventricular nodal pathway ablation

OBJECTIVES

The purpose of this study was to describe a midseptal approach to selective slow pathway ablation for the treatment of AV nodal reentrant tachycardia (AVNRT). In addition, predictors of success and recurrence were evaluated.

METHODS

Selective ablation of the slow AV nodal pathway utilizing radiofrequency (RF) energy and a midseptal approach was attempted in 60 consecutive patients with inducible AVNRT.

RESULTS

Successful slow pathway ablation or modification was achieved in 59 of 60 patients (98%) during a single procedure. One patient developed inadvertent complete AV block (1.6%). A mean of 2.7 +/- 1.4 RF applications were required with mean total procedure, ablation, and fluoroscopic times of 191 +/- 6.3, 22.8 +/- 2.3, and 28.2 +/- 1.8 minutes, respectively. The PR and AH intervals, as well as the antegrade and retrograde AV node block cycle length, were unchanged. However, the fast pathway effective refractory period was significantly shortened following ablation (354 +/- 13 msec vs 298 +/- 12 msec; P = 0.008). The A/V ratio at successful ablation sites were no different than those at unsuccessful sites (0.22 +/- 0.04 vs 0.23 +/- 0.03). Junctional tachycardia was observed during all successful and 60 of 122 (49%) unsuccessful RF applications (P < or = 0.0001). A residual AV nodal reentrant echo was present in 15 of 59 (25%) patients. During a mean follow-up of 20.1 +/- 0.6 months (11.5-28 months) there were four recurrences (5%), 4 of 15 (27%) in patients with and none of 44 patients without residual slow pathway conduction (P = 0.002).

CONCLUSIONS

A direct midseptal approach to selective ablation of the slow pathway is a safe, efficacious, and efficient technique. Junctional tachycardia during RF energy application was a highly sensitive but not specific predictor of success and residual slow pathway conduction was associated with a high rate of recurrence.

Microwave ablation of the atrioventricular junction in open-chest dogs

The use of microwave energy for ablation of the atrioventricular (AV) junction was examined in open-chest dogs. Using a specially designed microwave catheter and a 2450 MHz generator, microwave energy was delivered to the AV junction according to one of two protocols. In protocol 1, increasing amounts of energy were delivered until irreversible AV block occurred. In protocol 2, only two applications of energy were used, one at low energy and the other at an energy found to be high enough to cause irreversible AV block. Each dog received between one and six applications of microwave energy. The amount of energy delivered per application ranged from 25.6 to 311.4 J. No AV block was seen at 59.4 +/- 28.3 J. Reversible AV block was seen with an energy of 120.6 +/- 58 J. Irreversible AV block was seen at 188.1 +/- 75.9 J. Irreversible AV block could be achieved in each animal. There was no difference in the energy required to cause irreversible AV block between the two protocols. The tissue temperature measured near the tip of the microwave catheter was correlated with both the amount of energy delivered and the extent of AV block caused. Histologic examination demonstrated coagulation necrosis of the conduction system. Microwave energy is a feasible alternative energy source for myocardial ablation. Since tissue damage is due exclusively to heating and the resulting rise in temperature can be measured, microwave energy may have advantages over currently existing energy sources in terms of both titrating delivered energy and monitoring the extent of tissue destruction.

Slow pathway ablation in patients with atrioventricular node reentrant tachycardia and a prolonged PR interval

OBJECTIVES

We sought to assess the safety and efficacy of selective slow pathway ablation using radiogfrequency energy and a transcatheter technique in patients with a prolonged PR interval and atrioventricular (AV) node reentrant tachycardia.

BACKGROUND

Although both fast and slow AV node pathways can be ablated in patients with AV node reentrant tachycardia, slow pathway ablation, by obviating the risk of AV block, appears to be safer. However, the safety and efficacy of selective slow pathway ablation using transcatheter radiofrequency energy in patients with a prolonged PR interval during sinus rhythm are unclear.

METHODS

The seven study patients with a prolonged PR interval (mean +/- SD 237 +/- 26 ms) comprised three women and four men with a mean age of 31 +/- 15 years. The slow pathway was targeted in all seven patients at the posterior/inferior interatrial septal aspect of the tricuspid annulus. Two patients presented with the uncommon variety of AV node reentrant tachycardia after initial fast pathway ablation; in the remaining five patients, the AV node reentrant tachycardia was of the common variety.

RESULTS

A single radiofrequency pulse at 30 W successfully abolished the slow pathway in both the anterograde and the retrograde direction in the two patients with uncommon AV node reentrant tachycardia. A mean of 5 +/- 3 radiofrequency pulses were required in the remaining five patients with reentrant tachycardia of the common variety. The postablation PR interval and AH interval remained unchanged. The shortest cycle length of 1:1 AV conduction was prolonged significantly (from 327 +/- 31 to 440 +/- 59 ms, p < 0.01, as was the AV node effective refractory period (from 244 +/- 35 to 344 +/- 43 ms, p < 0.01). During a mean follow-up interval of 20 +/- 6 months, no patient developed symptoms suggestive of AV node reentrant tachycardia or had evidence of second- or third-degree AV block.

CONCLUSIONS

These data suggest that the AV node slow pathway can be ablated in patients with AV node reentrant tachycardia who demonstrate a prolonged PR interval during sinus rhythm.

Anatomic definition of a vulnerable extranodal site in AV node reentry

The success of methods that ablate atrioventricular (AV) node reentry demonstrates that extranodal tissue is part of the reentry circuit. The hypothesis of this study is that atrial tissue approaching the posterior AV node is part of the AV node reentry circuit and is especially suitable for complete division with sparing of AV conduction. This study measured AV node function after either an anterior or posterior perinodal incision. The only significant change noted in antegrade function was a lengthening of the Wenckebach point after the posterior incision. Retrograde AV conduction and ventricular echoes were abolished by the posterior incision, whereas the anterior incision had no discernible effect on retrograde AV node function. Anatomic analysis of the two incisions showed that the posterior incision completely interrupted the posterior atrial input to the AV node, whereas the anterior incision spared the medial input to the AV node. The atrial tissue posterior to the AV node is anatomically suited for complete interruption. Ablation of atrial tissue posterior to the AV node is proposed for abolishing AV node reentrant tachycardia.

Radiofrequency catheter ablation as a cure for idiopathic tachycardia of both left and right ventricular origin

OBJECTIVES

The purpose of this study was 1) to investigate the efficacy and safety of radiofrequency energy catheter ablation as curative treatment for idiopathic tachycardia of both left and right ventricular origin, and 2) to compare the usefulness of different methods used to map the site of origin of idiopathic ventricular tachycardia.

BACKGROUND

Percutaneous radiofrequency catheter ablation has been used with dramatic success in the treatment of patients with Wolff-Parkinson-White syndrome, atrioventricular node reentrant tachycardia and bundle branch reentrant tachycardia. Limited data are available on the use of radiofrequency energy catheter ablation as curative treatment for idiopathic tachycardia of both left and right ventricular origin.

METHODS

Twenty-eight consecutive patients (13 to 71 years old) presenting with idiopathic ventricular tachycardia were enrolled in the study. The site of origin of both left and right ventricular tachycardia was mapped using earliest endocardial activation times during tachycardia and by pace mapping. These mapping techniques were compared.

RESULTS

Radiofrequency ablation was successful in all eight patients (100%) with left ventricular tachycardia. Tachycardia recurred in one patient. The ablation procedure was complicated by mild aortic insufficiency in one patient. Right ventricular outflow tract tachycardia was successfully ablated in 17 (85%) of 20 patients. The success rate at follow-up was 85%. In one patient, the ablation procedure was complicated by acute ventricular perforation and death. Pace maps from successful ablation sites were better than pace maps from unsuccessful sites (p < 0.004). Endocardial activation times at successful ablation sites were not different from unsuccessful sites (p < 0.13).

CONCLUSIONS

Radiofrequency catheter ablation is an effective treatment for idiopathic ventricular tachycardia. The site of origin of tachycardia is best identified using pace mapping. Significant complications can occur and should be considered in the risk/benefit analysis for each patient.

Slow potentials in the atrioventricular junctional area of patients operated on for atrioventricular node tachycardias and in isolated porcine hearts

OBJECTIVES

The purpose of this study was to 1) investigate extracellular electrograms in the atrioventricular (AV) junctional area of patients with AV node reentrant tachycardia, 2) compare them with recordings made in isolated porcine hearts, and 3) study their origin.

BACKGROUND

Electrograms with slow components have been used to target the delivery of radiofrequency energy for the cure of AV node reentrant tachycardia. The origin of these electrograms is unknown.

METHODS

In 12 human and 19 porcine hearts, extracellular recordings were made simultaneously from 64 sites. In five other porcine hearts, intracellular recordings were made at sites at which extracellular electrograms revealed slow potentials. Histologic investigations were carried out in four of these hearts.

RESULTS

Electrograms with slow components were recorded in five human and eight porcine hearts. These signals were found at sites up to 12 mm from the His bundle. Characteristics of the electrograms did not differ significantly among human and porcine hearts. Electrophysiologic evidence for multiple pathways was present in four hearts. Superficial impalements with microelectrodes at sites with slow potentials showed action potentials with AV node characteristics. In the majority of these recordings, the upstroke coincided with the downstroke of slow potentials. Histologic investigations of the sites of impalement revealed transitional cells directly underneath the endocardium.

CONCLUSIONS

Slow potentials were recorded in both human and porcine hearts in similar measure. They arise from transitional cells and have action potentials similar to N cells.

Atrioventricular nodal reentry tachycardia: electrophysiologic comparisons in patients with and without 2:1 infra-His block

Patients with atrioventricular nodal reentry tachycardia (AVNRT) occasionally may demonstrate a 2:1 infra-His block during tachycardia. However, the electrophysiologic background of this phenomenon has not been established so far. In the present study we compared the electrophysiologic parameters of 10 consecutive patients with a transient 2:1 infra-His block during AVNRT of the common type (Group A) with those of 17 consecutive patients without this phenomenon during tachycardia (Group B). Transient 2:1 infra-His block occurred without termination of the tachycardia in all 10 patients of Group A. The tachycardia sustained despite intermittent or permanent conduction disturbance of the infrahisian tissue in 8 of these 10 patients. In comparison, the electrophysiologic parameters of 17 patients without 2:1 block during AVNRT of the common type (Group B) were analyzed. A significantly longer antegrade (318 +/- 58 ms vs. 259 +/- 50 ms) and retrograde (308 +/- 59 ms vs. 239 +/- 20 ms) AV conduction capacity could be demonstrated in these patients. The tachycardia cycle length did not differ significantly between the two groups, although the mean tachycardia cycle length was 48 ms longer in patients of Group B. These observations demonstrate an advanced conduction capacity in patients with a transient infra-His block during AVRNT of the common type. This study underlines that the reentry circuit in AVNRT is not necessarily dependent on infrahisian tissue.

Alternating Wenckebach periods and allied arrhythmias

Alternating Wenckebach periods (AWPs) are episodes of 2:1 block during which the PR, AH, or AV intervals of the conducted beats gradually increase until a greater degree of block ensues. Most episodes occur at the AV node, but some have also been reported in other structures. AWPs are usually attributed to multilevel block due to transverse (horizontal) dissociation. This assumption was initially based on a method in which the solutions to difficult electrocardiographic rhythms were arrived at by analysis and deduction based on the knowledge existing at that particular time. Subsequently, it was reinforced by information extrapolated from intracardiac recordings performed in patients with documented multilevel block in separate anatomical structures (atria, AV node, and His bundle), as well as from microelectrode studies and computer simulations. Although AWPs are frequently observed in clinical tracings, those occurring at the AV node are best categorized during incremental atrial stimulation because then they occupy a specific point in the wide spectrum of tachycardia dependent AV nodal conduction disturbances. In fact, the A:H ratios occurring in the episodes where the degree of block increases can be represented by "universal" mathematical formulas. However, in the clinical setting, drugs affecting the electrophysiology of the node can alter the pacing induced symmetry by producing additional differential effects on the various levels. The latter still requires further elucidation.

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.

"AV nodal" reentry: Part II: AV nodal, AV junctional, or atrionodal reentry?

The classical model of "atrioventricular (AV) nodal" reentrant tachycardia suggests that the reentrant circuit is entirely within the compact AV node and that AV nodal tissue is present proximal and distal to the circuit. Recent evidence from mapping studies and from examination of the effects of curative procedures, however, suggests that the upper end of the circuit uses perinodal atrial or transitional tissue. Moreover, the anatomical substrate of dual "AV nodal" pathways is likely to be the multiple connections between compact AV node and atrium rather than discrete intranodal pathways. The antegrade slow pathway appears to be situated at the posteroinferior approaches to the AV node in the region between the coronary sinus orifice and the tricuspid annulus. The retrograde fast pathway appears to be situated in the anterior atrionodal connections at the apex of Koch's triangle, close to the His bundle. The lower turnaround point of the circuit is likely to be within the AV node.

Radiofrequency catheter ablation of supraventricular arrhythmias in patients with congenital heart disease: results and technical considerations

OBJECTIVES

The aim of this study was to report the results and techniques of radiofrequency ablation for treatment of supraventricular arrhythmias in patients with congenital structural heart disease.

BACKGROUND

The management of patients with congenital and other structural heart disease may be complicated by serious arrhythmias due to Wolff-Parkinson-White syndrome or by atrial arrhythmias after cardiac surgery. Ablation techniques using radiofrequency current are revolutionizing the management of arrhythmias, but reports have included few with structural heart disease.

METHODS

Fifteen patients with significant heart disease underwent radiofrequency ablation: 11 with Wolff-Parkinson-White syndrome and 4 with intraatrial reentrant tachycardia after atrial surgery. Seven had Ebstein's anomaly, complex in two, and the rest had other defects. Coexistence of structural defects introduced significant technical difficulties to radiofrequency ablation in patients with the Wolff-Parkinson-White syndrome and was accomplished by adaptation of current techniques. Ablation of intraatrial reentrant tachycardia was performed by finding early atrial activation sites with electrogram fractionation for radio-frequency application.

RESULTS

Radiofrequency ablation was initially successful in 14 of 15 patients, with cure in 10 and clinical improvement in 14. Two patients subsequently underwent cardiac surgery without perioperative arrhythmias.

CONCLUSIONS

Radiofrequency ablation in patients with congenital heart disease and arrhythmias in both safe and effective and may be the preferred approach to treatment in some patients. In patients who are to undergo surgical correction or palliation, preoperative radiofrequency ablation of the tachycardia substrate is effective and may be preferred to operative accessory pathway division. The ablation of intraatrial reentrant tachycardia shows promise in the management of patients who have undergone extensive atrial surgery, and it may eventually become the preferred approach, particularly when there are contraindications to the use of antiarrhythmic agents.

Therapeutic end points for the treatment of atrioventricular node reentrant tachycardia by catheter-guided radiofrequency current

OBJECTIVES

The purpose of this prospective study was to test the hypothesis that the elimination of inducible repetitive atrioventricular (AV) node reentry despite the persistence of slow AV pathway conduction is a valid end point for radiofrequency catheter ablation procedures in patients with supraventricular tachycardia due to AV node reentry.

BACKGROUND

Although modification of AV node physiology by radiofrequency current can eliminate AV node reentrant tachycardia, therapeutic end points that are definitive of a satisfactory result in patients undergoing modification of the slow AV pathway have not been established. Applications of radiofrequency current at selected sites may eliminate all evidence of slow pathway conduction or sufficiently modify the refractory properties of the slow pathway to preclude sustained arrhythmias. Accordingly, total abolition of dual AV node physiology may not be necessary to prevent arrhythmia recurrence.

METHODS

Radiofrequency catheter ablation of the slow AV pathway was attempted in 59 patients with typical AV node reentry. Tissue ablation was performed with a continuous wave of 500-kHz radiofrequency current. Twenty-five to 35 W was applied for 60 s at the site selected for tissue destruction.

RESULTS

Dual AV node physiology was eliminated completely in 35 patients (59%), persisted without inducible AV node reentry in 13 patients (22%) and persisted with inducible single AV reentrant beats in 11 patients (19%). In patients with persistent dual AV node physiology, the maximal difference between the effective refractory period of the fast and slow pathways was reduced from 104 +/- 62 ms before the procedure to 37 +/- 37 ms after AV conduction had been modified (p < 0.001). During a mean follow-up interval of 15 months (range 4 to 28), only one patient (2%) had a recurrence of the tachycardia.

CONCLUSIONS

Results demonstrate that when complete elimination of dual AV node physiology is difficult, modification of slow pathway conduction to the extent that repetitive AV node reentry cannot be induced is a definitive end point that portends a good prognosis.