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

Role of radiofrequency ablation in the management of supraventricular arrhythmias: experience in 760 consecutive patients

INTRODUCTION

Several reports have demonstrated that radiofrequency catheter ablation provides effective control of a variety of supraventricular tachycardias. However, the efficacy, complications, risk of arrhythmia recurrence, and follow-up survival analysis have not been reported in a large series of consecutive patients with supraventricular arrhythmias with diverse electrophysiologic mechanisms. This report details the results of radiofrequency catheter ablation in 760 consecutive patients (386 males, 374 females) with a wide variety of supraventricular tachycardias treated at one center.

METHODS AND RESULTS

Arrhythmias were associated with the presence of an accessory pathway in 363 patients (384 accessory pathways), including four patients with Mahaim fibers and eight patients with the permanent form of junctional reciprocating tachycardia. The mechanism of the clinical arrhythmia was AV nodal reentrant tachycardia in 245 patients, and a primary atrial tachycardia in 20 patients (ectopic atrial tachycardia in 16 patients and sinus nodal reentry in 4 patients). Ablation of the reentrant circuit of atrial flutter within the right atrium was attempted in 13 patients. AV node ablation and permanent pacemaker implantation were performed in 119 patients with medically refractory atrial fibrillation or flutter. Radiofrequency catheter ablation was successful in 346 of 363 patients (95.3%, CI 93.1%-97.5%) with accessory pathways (367 of 384 pathways, 95.6%, CI 93.5%-97.6%) with a complication rate of 1.1% and a recurrence rate of 5.5%. Successful accessory pathway ablation was achieved for 179 of the first 192 pathways treated (93.2%, CI 89.7%-96.6%) and increased to 188 of 192 pathways (97.9%, CI 95.9%-99.9%) over the second half of the series. AV nodal reentry was successfully abolished in 244 of 245 patients (99.6%, CI 98.8%-100%) by selective ablation of the slow pathway in 234 patients and the fast pathway in 10 patients. The complication rate in this group was 2.0% with a recurrence rate of 6.5%. All 20 primary atrial tachycardias were successfully ablated with no complications and a recurrence rate of 15%. The reentrant circuit of atrial flutter was ablated successfully in 10 of 13 patients (77%) with recurrent atrial flutter in one additional patient. Complete AV block was achieved in 117 of 119 (98.3%, CI 96.0%-100%) patients with atrial fibrillation or flutter treated by AV nodal ablation with a complication rate of 0.8% and recurrence of AV conduction in 6%. The median duration of fluoroscopy exposure for the population was 23.4 minutes. The overall primary success rate for the entire population was 97.0% (737 of 760 patients, CI 95.8%-98.2%).

CONCLUSION

Thus, the results of this large series of patients demonstrates the safety and efficacy of radiofrequency ablation for the treatment of a wide variety of supraventricular arrhythmias. It also appears that increasing experience with these procedures increases the rate of successful ablation and decreases the risk of complications.

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.

Radiofrequency versus pharmacologic modification of the atrioventricular node

Although transcatheter radiofrequency modification of the atrioventricular (AV) node has been proposed as curative treatment in AV nodal reentry tachycardias, its role for the control of the ventricular rate in atrial tachyarrhythmias remains unclear. The aim of this study was to analyze the acute effect of radiofrequency current on AV nodal conduction and refractoriness, and to compare it with the effects of two antiarrhythmic drugs such as amiodarone (class III) and flecainide (class I). Twenty-one dogs were studied: (1) radiofrequency group (5 W for less than 45 seconds; 2 to 12 discharges; seven dogs); (2) amiodarone group (5 mg/kg intravenously; seven dogs); and (3) flecainide group (2 mg/kg intravenously; seven dogs). The following parameters were measured under basal conditions and after each procedure: AH interval, AV nodal functional refractory period, Wenckebach cycle length, minimum R-R interval during atrial fibrillation, and fitting of AV nodal function curve to a hyperbolic equation using its linear transformation. The AV nodal effective refractory period could not be calculated in any dog in the basal study because it was shorter than the atrial functional refractory period.(ABSTRACT TRUNCATED AT 250 WORDS)

Pseudo-pacemaker syndrome following inadvertent fast pathway ablation for atrioventricular nodal reentrant tachycardia

Atrioventricular nodal reentrant tachycardia that is refractory to drug treatment has recently been treated with radiofrequency catheter ablation. In this case report we describe a patient with atrioventricular nodal reentrant tachycardia in whom radiofrequency ablation of slow pathway was attempted, with inadvertent damage to the fast pathway. The patient developed marked first-degree atrioventricular block associated with symptoms mimicking pacemaker syndrome.

Supraventricular tachycardias: the role of surgery

Because of its high efficacy and low morbidity radiofrequency energy catheter ablation techniques have toppled the hierarchy of choice in the electrophysiological intervention armamentum. This review assesses current role of surgery and its foreseeable future. Most accessory AV pathways can be attained by endocardial manipulation and ablated. Surgical dissection of accessory pathways on the beating heart had documented that most pathways were paraannular, although right-sided pathways may be distant to the annulus. Results of accessory pathway ablation have shown that right-sided pathways are difficult to approach and ablate. Surgical ablation may currently be considered after failed catheter ablation. AV nodal modification using catheter ablation also yields excellent results. Radiofrequency energy creates a discrete lesion associated with discrete electrophysiological alteration. Surgical dissection is associated with more diffuse and extensive anatomical and electrophysiological changes and is no longer used even after failed catheter ablation. The arrhythmogenic anatomical substrate associated with atrial flutter is not yet well delineated in the coronary sinus os region. How to extend tissue modification for uniform success here is not yet known. Further surgical approach combined with extensive intraoperative cardiac mapping may ultimately prove a valuable guide for subsequent catheter technique. Atrial fibrillation is the last surgical frontier unchallenged by catheter techniques. Arrhythmogenic anatomical substrate is diffuse spreading over the entire atrial myocardium without a discrete target. The associated pathology is diffuse, severe, and progressive and present even in the so-called lone atrial fibrillation. Progression of underlying pathology can nullify the best designed surgical rationale in terms of sinus node chronotropic function, and atrial contractility. Currently used surgical techniques, i.e., the corridor and the Maze operations, have contributed to a better selection of patients. Surgery is still associated with significant morbidity and relative efficacy, and may be improved before becoming the electrophysiological intervention of choice for atrial fibrillation. In conclusion, atrial fibrillation is a greater surgical challenge, but has to be met with the same standard used for other supraventricular tachycardias.

Should radiofrequency therapy be performed in every symptomatic patient with supraventricular tachycardia? (Pro drug position)

The indication for treatment of paroxysmal supraventricular tachycardia depends on the frequency and severity of the tachycardia attacks. If the tachycardia attacks are mildly symptomatic and occur only once or twice a year, there is no indication for either continuous drug therapy or radiofrequency ablation. The only therapeutic measure required is termination of each acute event. If symptoms occur frequently, long-term antiarrhythmic drug therapy is then indicated and will be effective for chronic prophylaxis in most individuals with a low risk of proarrhythmic events. Only in patients with severe or life-threatening symptoms or cases refractory to drug therapy would radiofrequency ablation possibly be justified.

Extended protocol for demonstration of dual AV nodal physiology

The incidence of dual atrioventricular (AV) nodal physiology was evaluated in 22 patients (14 males, 8 females, age 52 +/- 18 years) undergoing electrophysiology studies for evaluation of ventricular tachycardia/nonsustained ventricular tachycardia (n = 11), supraventricular tachycardia (n = 5), and syncope (n = 6). Patients with AV node reentrant tachycardia were excluded. Thirteen patients had normal left ventricular function and nine patients (seven with coronary artery disease, two with dilated cardiomyopathy) had depressed left ventricular function. Single atrial extrastimuli (A2) were introduced after eight-beat drives at paced cycle lengths of 550 msec and 400 or 450 msec beginning at coupling intervals of 650 and 500 or 550 msec, respectively. The coupling interval was decreased at 10-msec intervals until AV node or atrial refractoriness. A second atrial extrastimulus (A3) was then added. A2 was fixed at 50 msec greater than the atrial or AV nodal refractory period. A3 was coupled to A2 at 650 and 500 or 550 msec and decremented as with single extrastimulation. Dual AV nodal physiology was defined by a 50-msec increase in A2H2 or A3H3 with a 10-msec decrement in the coupling interval or a discontinuous H1H2 versus A1A2 or H2H3 versus A2A3 curve. Using a single extrastimulus, 1 of 22 patients demonstrated dual AV nodal physiology. Using double extrastimuli, an additional four patients with dual AV nodal physiology were identified. The occurrence of dual AV nodal physiology determined using double extrastimuli is increased compared to using only a single extrastimulus (P = 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

Selective elimination of retrograde conduction by intraoperative neodymium: YAG laser photocoagulation in dogs

OBJECTIVES

The purpose of this study was to test the feasibility of selective elimination of ventriculoatrial (VA) conduction by limited laser photocoagulation of the atrioventricular (AV) node, and to analyze the histologic substrate of unidirectional retrograde block.

BACKGROUND

Atrioventricular node reentry requires intact retrograde conduction.

METHODS

Neodymium:yttrium-aluminum-garnet laser photocoagulation was performed during cardiopulmonary bypass through a right atriotomy in 15 dogs that had intact retrograde conduction before operation. Short laser pulses were delivered to an area between the coronary sinus orifice and the proximal His bundle. The end point of lasing was second-degree AV node block at a paced atrial cycle length of 250 ms.

RESULTS

Complete retrograde block developed immediately in 11 of the 15 dogs (group I), while AV conduction persisted in all 11. In 4 of the 15 dogs (group II), both AV and VA conduction remained intact. During a 3-month follow-up period, retrograde conduction remained absent in all group I dogs. Retrograde block was not reversed by isoproterenol. Anterograde AV node characteristics (Wenckebach cycle length, functional refractory period, ventricular rate during atrial fibrillation) were unchanged in five dogs and modified in six. Complete AV block did not develop. In four control dogs (group III, sham operation), anterograde and retrograde AV node characteristics were unchanged. The anterograde Wenckebach cycle lengths in groups I, II and III at 3 months measured 192 +/- 15 ms, 195 +/- 6 ms and 170 +/- 22 ms, respectively, whereas the retrograde Wenckebach cycle lengths in groups II and III measured 345 +/- 62 ms and 278 +/- 25 ms, respectively. Histologic study at 3 months in cases with unidirectional VA block showed the compact part of the AV node intact with destruction of the atrial approaches and the superficial layers of the proximal end of the node on the right side.

CONCLUSIONS

1) With limited laser photocoagulation of the proximal AV node area, VA conduction can be eliminated and anterograde AV node transmission maintained. 2) Destruction of the atrial approaches on the right side with preservation of the compact part of the AV node may result in unidirectional retrograde block.

Physiology of "atypical" atrioventricular junctional reentrant tachycardia occurring following radiofrequency catheter modification of the atrioventricular node

The physiology of atypical atrioventricular junctional reentrant tachycardia (AVJRT) occurring following catheter modification of the AV node is poorly defined. Six patients undergoing radiofrequency current catheter modification of the AV node had inducible atypical AVJRT before or after AV nodal modification. Typical AVJRT was differentiated from atypical AVJRT by a ventriculoatrial (VA) time < 60 msec in the His-bundle electrogram recording. Five of six patients had typical AVJRT and two had atypical AVJRT prior to AV nodal modification. Following anterior approach AV nodal modification, previously undetected atypical AVJRT was induced in four patients. Earliest retrograde atrial activation in the posterior septum was documented in all patients with atypical AVJRT prior to modification and in three of four patients with atypical AVJRT following modification. The AH intervals during tachycardia were 320 +/- 52 msec in typical AVJRT, 88 +/- 33 msec in the premodification atypical AVJRTs, and 172 +/- 12 msec in the postmodification atypical AVJRTs (P = 0.0001). The AH/HA ratios were 4.1 +/- 0.9 in typical AVJRT, 0.5 +/- 0.2 in the premodification atypical AVJRTs, and 0.9 +/- 0.2 in the postmodification atypical AVJRTs (P = 0.0001). Two patients with postmodification atypical AVJRT underwent further posterior approach AV node modification that resulted in VA block. One patient with postmodification atypical AVJRT had further anterior approach AV nodal modification that resulted in heart block. The retrograde limb of the atypical AVJRT seen following anterior approach AV nodal modification is a posterior, slow pathway.

Treatment of supraventricular tachycardias with transcatheter delivery of radiofrequency current

Medical therapy for the treatment of supraventricular tachycardias is frequently ineffective and associated with significant side effects, whereas curative surgical approaches have generally been limited by their considerable morbidity and cost. Greater understanding of the mechanisms underlying supraventricular tachycardias has improved our ability to precisely map endocardial areas critical to arrhythmogenesis. Advances in catheter ablation techniques and particularly the use of radiofrequency current to generate thermal energy for ablation have resulted in dramatic success rates for curative catheter ablation. This review examines the physics of radiofrequency current ablation and its application to the treatment of atrial fibrillation, atrial flutter, AV nodal reentrant tachycardia, and arrhythmias associated with the Wolff-Parkinson-White syndrome. The limitations, risks, and cost-effectiveness of this technique relative to medical and surgical approaches are also evaluated.

Dissociation of atrioventricular conduction and refractoriness following application of radiofrequency energy to the canine atrioventricular node: acute and chronic observations

The electrophysiology of AV nodal modification induced by radiofrequency energy (n = 5) or a sham procedure (n = 5) was studied in ten dogs. The five dogs that received radiofrequency energy had an AH prolongation > 100% from baseline values and this prolongation persisted throughout the 2-month study. The AV nodal functional refractory period was prolonged only acutely. These data indicate a dissociation between the effects on AV nodal conduction and refractoriness that was induced by this procedure. The five sham treated controls showed no acute or chronic electrophysiological changes. In the dogs that received radiofrequency energy, there was fibrosis of the approaches to the AV node and the region of the AV node itself. It is concluded that chronic modification of AV nodal conduction without concomitant changes in refractoriness can be induced by radiofrequency energy delivered in the proximal portion of the AV node. It would be anticipated that this procedure would not decrease the ventricular response to atrial fibrillation or flutter, may be effective in preventing AV nodal reentrant tachycardia by interfering with conduction either in the AV node or perinodal region. Since the AV node itself suffers at least moderate pathological damage, there may be an appreciable incidence of the late development of complete heart block after this procedure.

An anatomically guided approach to atrioventricular node slow pathway ablation

Radiofrequency ablation of the "slow" pathway of the atrioventricular (AV) node reentrant circuit may be guided by electrophysiologic ("slow pathway potential") or anatomic landmarks. Experience with a systematic, anatomically guided approach in 25 patients (20 women and 5 men, aged 38 +/- 15 years) with typical AV node reentry is described. The slow pathway is assumed to be the posterior input to the AV node, approaching the nodal region in the corridor between the tricuspid annulus and the orifice of the coronary sinus. A series of radiofrequency lesions are given to interrupt this corridor at its entrance to Koch's triangle. If this is unsuccessful, the series of lesions are repeated progressively at higher levels approaching the AV node. The major end point for success is elimination of the slow pathway as determined by extrastimulus testing. A mean of 1.2 +/- 0.2 ablative sessions (20 +/- 12 applications of energy) achieved clinical success in 24 of 25 patients (96%) at a follow-up of 8.6 +/- 2.2 months. Anterograde Wenckebach cycle length increased from 361 +/- 67 ms to 398 +/- 70 ms (p = 0.01), yet the atrio-Hisian interval in sinus rhythm did not change (69 +/- 17 ms before vs 65 +/- 15 ms after ablation), p = 0.22. Retrograde Wenckebach cycle length was not affected (348 +/- 78 ms before vs 366 +/- 82 ms after ablation). During ablation, transient third-degree AV block occurred in 6 patients with no permanent sequelae. This approach provides a systematic, expedient technique to eliminate slow pathway conduction based on anatomic landmarks.

Reappraisal of electrical cure of atrioventricular nodal reentrant tachycardia--lessons from a modified catheter ablation technique

A modified catheter ablation technique was studied prospectively in 29 patients with atrioventricular (AV) nodal reentrant tachycardia. A His bundle electrode catheter was used for mapping and ablation. Cathodic electroshocks (100-250 J) were delivered from the distal two electrodes (connected in common) of the His bundle catheter to the site selected for ablation. The optimal ablation site recorded the earliest retrograde atrial depolarization, simultaneous or earlier than the QRS complex, with absence of a His bundle deflection during AV nodal reentrant tachycardia. One additional electrical shock was delivered if complete abolition of retrograde VA conduction persisted for more than 30 min and AV nodal reentrant tachycardia was not inducible during isoproterenol and/or atropine administration. With a cumulative energy of 323 +/- 27 J and a mean of 2.3 +/- 0.5 shocks interruption or impairment of retrograde nodal conduction was achieved. Antegrade conduction, although modified, was preserved in 27 patients, with persistence of complete AV block in 2 patients. Two of the 27 patients still need antiarrhythmic agents to control tachycardia, the other 25 patients were free of tachycardia within a mean follow-up period of 13 +/- 2 months (range 7 to 20 months). Twenty-three patients received late follow-up electrophysiological studies (3-6 months after the ablation procedures), and the AV nodal function curves were classified into 4 types. The majority of the patients (15/23) had loss of retrograde conduction. Among the 8 patients with prolongation of retrograde conduction, 4 patients still had antegrade dual AV nodal property but all without inducible tachycardia. In conclusion, preferential interruption or impairment of retrograde conduction was the major, but not the sole, mechanism of electrical cure of AV nodal reentrant tachycardia.

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

OBJECTIVES

A comprehensive electrophysiologic study followed by selective radiofrequency ablation from three sites was performed in patients with atrioventricular (AV) node reentrant tachycardia to better delineate the nature of the tachycardia circuit.

BACKGROUND

We postulated that the retrograde fast pathway is the anterior superficial group of transitional cells and the slow pathway is the compact node with its posterior input of transitional cells. Twenty-three consecutive patients were studied. In nine, the atria could be dissociated from the tachycardia by delivery of an atrial extrastimulus during tachycardia.

METHODS

Radiofrequency ablation was performed with three approaches. The anterior approach was designed to interrupt the anterior superficial atrial input to the compact node, the posterior approach to interrupt the posterior atrial input to the compact node and the inferior approach to destroy the compact node itself.

RESULTS

Selective ablation of the retrograde fast pathway was achieved in seven patients, six with the anterior and one with the inferior approach. Anterograde fast pathway conduction was not affected, whereas retrograde fast pathway conduction was either abolished or markedly depressed. None had induction of echoes or tachycardia after ablation. Selective ablation of the slow pathway was successful in 13 patients, 1 with anterior, 3 with posterior and 9 with inferior approaches. In these 13 patients, both anterograde and retrograde fast pathway conduction were not affected, the dual pathway physiology was abolished and the tachycardia was not inducible after ablation. Ablation of both the retrograde fast pathway and the slow pathway occurred with the inferior approach in three patients.

CONCLUSIONS

We conclude that the retrograde fast pathway is likely to be the anterior superficial group of transitional cells, whereas the slow pathway is the compact node and its posterior input of transitional cells. A barrier seems to exist between the atrium and the tachycardia circuit. In a broad view of the AV node structure, the tachycardia circuit is confined to the node.

Treatment of supraventricular tachycardia due to atrioventricular nodal reentry by radiofrequency catheter ablation of slow-pathway conduction

BACKGROUND

Atrioventricular nodal reentrant tachycardia (AVNRT), the most common form of supraventricular tachycardia, results from conduction through a reentrant circuit comprising fast and slow atrioventricular nodal pathways. Antiarrhythmic-drug therapy is not consistently successful in controlling this rhythm disturbance. Catheter ablation of the fast pathway with radiofrequency current eliminates AVNRT, but it can produce heart block. We hypothesized that catheter ablation of the site of insertion of the slow pathway into the atrium would eliminate AVNRT while leaving normal (fast-pathway) atrioventricular nodal conduction intact.

METHODS AND RESULTS

Eighty patients with symptomatic AVNRT were studied. Retrograde slow-pathway conduction (in which the earliest retrograde atrial potential was recorded at the posterior septum, close to the coronary sinus) was present in 33 patients. The retrograde atrial potential was preceded by a potential consistent with activation of the atrial end of the slow pathway (ASP). In 46 of the 47 patients without retrograde slow-pathway conduction, a potential with the same characteristics as the ASP potential was recorded during sinus rhythm. Radiofrequency current delivered through a catheter to the ASP site (in the posteroseptal right atrium or coronary sinus) abolished or modified slow-pathway conduction in 78 patients, eliminating AVNRT without affecting normal atrioventricular nodal conduction. In the single patient without ASP, the application of radiofrequency current to the proximal coronary sinus ablated the fast pathway and AVNRT: Atrioventricular block occurred in one patient (1.3 percent) with left bundle-branch block, after inadvertent ablation of the right bundle branch. AVNRT has not recurred in any patient during a mean (+/- SD) follow-up of 15.5 +/- 11.3 months. Electrophysiologic study 4.3 +/- 3.3 months after ablation in 32 patients demonstrated normal atrioventricular nodal conduction without AVNRT:

CONCLUSIONS

Catheter ablation of the atrial end of the slow pathway using radiofrequency current, guided by ASP potentials, can eliminate AVNRT with very little risk of atrioventricular block.

Thermal ablation of perfused porcine left ventricle in vitro with the neodymium-YAG laser hot tip catheter system

Catheter ablation in the treatment of arrhythmias has been limited by the small lesion size achievable with a radiofrequency energy source. The feasibility of catheter ablation with a neodymium-yttrium-aluminum-garnet (Nd-YAG) laser hot tip catheter was tested because of the capability of achieving a high catheter-tissue contact temperature, which should result in a larger lesion. In a model of isolated perfused pig hearts, 77 endocardial lesions were produced with powers of 1 to 10 watts and peak measured temperatures of 40 degrees to 318 degrees C. Lesion size correlated with power and temperature, but the correlations were poor. High temperature lesions resulted in significant intramyocardial catheter penetration and only marginal increased lesion width. Catheter ablation with a Nd-YAG laser hot tip catheter is feasible, but carries a risk of perforation at high powers. High temperatures result in tissue dessication with a resultant fall in thermal conductivity that limits the radius of thermal injury and overall lesion size.

Conversion of typical to "atypical" atrioventricular nodal reentrant tachycardia after radiofrequency catheter modification of the atrioventricular junction

Typical atrioventricular (AV) nodal reentry tachycardia (AVNRT) is characterized by anterograde activation over a slowly conducting pathway and by retrograde activation through a rapidly conducting pathway. Preliminary reports suggest that radiofrequency catheter modification can eliminate typical AVNRT while preserving anterograde conduction. Radiofrequency catheter modification was used to treat 88 patients with typical AVNRT. After baseline electrophysiologic evaluation, the ablation catheter was positioned proximal and superior to the site of maximal His deflection. Radiofrequency energy was applied until there was significant attenuation of retrograde conduction, and elimination of AVNRT inducibility. Eighty-one patients were successfully treated and form the basis of this report. A new paroxysmal supraventricular tachycardia with RP greater than PR interval was induced at electrophysiologic testing after successful ablation in 9 patients (11%). Mean atrial-His activation time was 140 +/- 31 ms, and the ventriculoatrial activation time was 170 +/- 46 ms. This arrhythmia was induced only with ventricular pacing during isoproterenol infusion and appeared to be mediated by AV nodal reentry. New retrograde dual AV nodal physiology after modification was more frequent in patients with atypical tachycardia than in those without (4 of 9 vs 2 of 72; p less than 0.0001). Although none of the patients were treated, only 1 of 9 had an episode of spontaneous atypical tachycardia during a mean follow-up of 12 months. Results of this study confirm that typical AVNRT can be rendered noninducible without the complete destruction of reentrant pathways. Because induction of "atypical" AVNRT was not predictive of spontaneous arrhythmia recurrence, it should not be an indication for additional ablation sessions or long-term drug therapy.

High success rate of atrioventricular node ablation with radiofrequency energy

Radiofrequency current was introduced as an alternative energy source for transcatheter ablation of cardiac arrhythmias to avoid the complications associated with direct current shocks. Initial use of radiofrequency current for complete ablation of the atrioventricular (AV) node yielded only moderate success rates, presumably because of the small size of electrodes and difficulty in localizing the AV node. The use of a larger 4-mm tip electrode for delivery of radiofrequency current and a method to better localize the AV node were prospectively studied in 32 patients undergoing catheter ablation of the AV node. There were 21 men and 11 women with a mean age of 62 +/- 12 years. Complete AV block was achieved immediately in 31 patients (97%) and it persisted in 28 patients (88%) during a mean follow-up period of 12 +/- 6 months. Three patients who had return of AV condition required no drug therapy for control of ventricular rate during atrial fibrillation. The number of radiofrequency pulses used to achieve complete AV block ranged from 1 to 5 (mean 1.9 +/- 1.1). In greater than 50% of the cases, only one radiofrequency pulse was required. The mean power and duration of radiofrequency pulses were 21.2 +/- 4.5 W and 33 +/- 15 s, respectively. All patients developed a stable junctional escape rhythm within 45 min of successful ablation. The QRS configuration was unchanged in 30 patients. One patient had a new right bundle branch block after ablation. There were no complications related to the ablation procedure.(ABSTRACT TRUNCATED AT 250 WORDS)

Antitachycardia devices: realities and promises

Nonpharmacologic therapy for ventricular arrhythmias has gained growing attention with the development of the implantable cardioverter-defibrillator. In addition, the reports of adverse effects of drug therapy from several studies, including the Cardiac Arrhythmia Suppression Trial (CAST), have supported the need for these devices. The development of new implantable cardioverter-defibrillators that have the capability of antitachycardia pacing, bradycardia pacing, cardioversion and defibrillation has enhanced their clinical utility. The currently available implantable cardioverter-defibrillators have been shown to significantly improve survival after sudden cardiac arrest in patients with life-threatening ventricular arrhythmias. Newer devices with expanded capabilities may reduce mortality even further. In this report the features of currently available antitachycardia devices and implantable cardioverter-defibrillators are reviewed and the features and current implant data on newer antitachycardia devices are discussed.

Two phase radiofrequency catheter ablation of isolated ventricular endomyocardium

This report describes a two phase radiofrequency (TPRF) energy source producing two radiofrequency sinusoidal voltages of similar frequency but different phase angles between three points of wire. When delivered through an orthogonal electrode catheter array (OECA) TPRF energy produces a square-shaped lesion of the area covered by the five electrodes (0.8 cm2). The purposes of the study were: to create square-shaped lesions using TPRF energy; to compare the size of lesions created by single phase radiofrequency (SPRF) to that of TPRF energy; and to study the depth of such lesions and to create lesions of desired size by adjacent placement of the OECA using TPRF energy. Ablations were created in nine isolated bovine hearts using three power settings (10, 20, and 40 watts) and three pulse durations (5, 10, and 20 seconds). Pathological examination was performed to document the length, width, depth, and the microscopic changes of ablations. TPRF energy increases the size of lesion (P less than 0.001) and utilizes less power (P less than 0.008) at the same power setting and pulse duration compared to SPRF energy. This is possibly related to earlier rise in impedance with TPRF compared to SPRF ablations. The largest lesion for both SPRF (0.51 +/- 0.08 cm2) and TPRF (1.03 +/- 0.18 cm2) ablations were observed at 20 watts for 20 seconds. By adjacent placement of the OECA and TPRF energy desired size (6 cm2) lesions were created. There was no significant difference between the depth of SPRF versus TPRF ablations at comparable power setting and pulse duration. Pathological examination revealed the shape of lesions were elliptical or cross-shaped for SPRF and square for TPRF ablations. Microscopic examination revealed coagulation necrosis, edema, and few necrotic cardiac muscle strands.

CONCLUSIONS

TPRF energy can cause 1.2 cm2 lesions. TPRF compared to SPRF energy causes larger lesions but depth of lesions are not different than SPRF energy at the same power setting and pulse duration. By adjacent placement of OECA and TPRF energy desired size lesion can be created (6 cm2).

Diagnosis and cure of the Wolff-Parkinson-White syndrome or paroxysmal supraventricular tachycardias during a single electrophysiologic test

BACKGROUND

We conducted this study to determine the feasibility of an abbreviated therapeutic approach to the Wolff-Parkinson-White syndrome or paroxysmal supraventricular tachycardia, in which the diagnosis is established and radiofrequency ablation carried out during a single electrophysiologic test.

METHODS

One hundred six consecutive patients were referred for the management of documented, symptomatic paroxysmal supraventricular tachycardias (66 patients) or the Wolff-Parkinson-White syndrome (40 patients). All agreed to undergo a diagnostic electrophysiologic test and catheter ablation with radiofrequency current. No patient had had such a test previously.

RESULTS

Among the 66 patients with paroxysmal supraventricular tachycardias, the mechanism was found to be atrioventricular nodal reentry in 46 (70 percent) (typical in 44 and atypical in 2), atrioventricular reciprocating tachycardia involving a concealed accessory pathway in 16 (24 percent), atrial tachycardia in 2 (3 percent), and noninducible paroxysmal supraventricular tachycardia in 2 (3 percent). A successful long-term outcome was achieved in 57 of 62 patients (92 percent) with paroxysmal supraventricular tachycardia in whom ablation was attempted and in 37 of 40 patients (93 percent) with the Wolff-Parkinson-White syndrome. The only complications were one instance of occlusion of the left circumflex coronary artery, leading to acute myocardial infarction, and one instance of complete atrioventricular block. The mean (+/- SD) duration of the electrophysiologic procedures was 114 +/- 55 minutes.

CONCLUSIONS

The diagnosis and cure of paroxysmal supraventricular tachycardia or the Wolff-Parkinson-White syndrome during a single electrophysiologic test are feasible and practical and have a favorable risk-benefit ratio. This abbreviated therapeutic approach may eliminate the need for serial electropharmacologic testing, long-term drug therapy, antitachycardia pacemakers, and surgical ablation.

Percutaneous radiofrequency catheter ablation for supraventricular arrhythmias in children

Nineteen procedures were performed in 17 children, aged 10 months to 17 years, using catheter radiofrequency applications for the management of malignant or drug-resistant supraventricular tachyarrhythmias. Diagnoses were junctional ectopic tachycardia in 1 patient, atrioventricular (AV) node reentrant tachycardia in 4 and accessory pathway-mediated tachycardia in 12. Accessory pathway locations were left lateral (n = 4), posteroseptal (n = 3), left posterior (n = 2), right posterolateral (n = 1), right posterior paraseptal (n = 1), right intermediate septal (n = 1) and right anterior (n = 1). Ablation of accessory pathways was performed using 20 to 40 W of energy. The catheter was passed retrograde to the left ventricle in patients with a left-sided pathway and anterograde to the right atrium in those with a right-sided or posteroseptal pathway. In the 12 patients with an accessory pathway, radiofrequency applications were successful in 11 pathways and failed in 2. There were no recurrences of accessory pathway-mediated tachycardia. Atrioventricular node reentrant tachycardia was treated by AV node modification using 15 W of energy applied until first degree AV block occurred. After radiofrequency catheter ablation, there was a prolonged AH interval, tachycardia was not inducible and tachycardia recurred in one patient. For the patient with junctional ectopic tachycardia, 15 to 18 W of energy was delivered at the site of the maximal His bundle electrogram until sinus rhythm and normal AV conduction appeared. After a recurrence, a second procedure abolished tachycardia and AV conduction. In summary, radiofrequency catheter ablation was initially successful in 17 of 19 procedures and ultimately curative in 14 (82%) of 17 patients with no serious complications. Radiofrequency catheter ablation appears to be a safe and effective method for the management of supraventricular tachyarrhythmias in children.

Modification of atrioventricular node transmission properties by intraoperative neodymium-YAG laser photocoagulation in dogs

The purpose of this study was to test the feasibility of neodymium-yttrium-aluminum-garnet (Nd-YAG) laser photocoagulation of the atrioventricular (AV) node to control the ventricular rate during rapid atrial rhythms without creating AV block. In 12 dogs on normothermic cardiopulmonary bypass, short laser pulses were delivered to an area between the coronary sinus orifice and the site of the most proximally recorded His deflection until second degree AV block occurred at a paced atrial rate of 200 beats/min. Long-term effects on AV node function were followed up for 3 months. Three animals developed chronic high grade AV block. In nine animals with preserved 1:1 conduction, the mean (+/- SEM) critical atrial cycle length resulting in AV node Wenckebach periodicity increased from 183 +/- 6 to 261 +/- 24 ms (+43%), the mean RR interval during induced atrial fibrillation increased from 248 +/- 14 to 330 +/- 27 ms (+32%) and the shortest RR interval during atrial fibrillation increased from 215 +/- 11 to 275 +/- 20 ms (+28%). Laser effects were not reversed by isoproterenol infusion. Histologic examination of the irradiated area showed fibrotic changes in the AV node and fatty metamorphosis. This study suggests that 1) graded Nd-YAG laser photocoagulation of the AV node region in dogs results in long-term modification of anterograde AV node transmission properties; 2) 1:1 conduction during sinus rhythm usually remains preserved, but ventricular rate during rapid atrial rhythms is chronically reduced; and 3) progression to high grade AV block occurs in a minority of animals.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of cryosurgery in the management of cardiac arrhythmias

In the late 1970s, cryoablation of the AV node, accessory pathways, and ventricular tachycardia was first demonstrated and the technique was thought likely to assume an increasing importance in the surgical management of cardiac arrhythmias. However, more than 10 years later, cryotherapy is relatively sparingly used in these situations, and is at best an adjunctive means of therapy. The principal reason for this may lie in what was thought to be its major advantage: the fact that it is a highly selective, precise means of ablating myocardial tissue. Whereas electrophysiological mapping of tachycardia is able to identify apparently localized areas of arrhythmia substrate, relatively wide surgical destruction of myocardial tissue is frequently required to ensure successful tachycardia abolition: discrete, precise means of ablation are at a disadvantage. The future role for cryosurgery would seem to lie in those areas of arrhythmia management where selective ablation of substrate is essential. The ability of cryosurgery to modify (rather than simply ablate) AV nodal physiology in patients with AV nodal re-entrant tachycardia is such that it is likely to rival the recently reported catheter techniques for modification of the AV node.

Electrophysiologic characteristics of manifest and latent retrograde conduction in dogs

Atrioventricular (AV) nodal reentry requires intact retrograde ventriculoatrial (VA) conduction. The purpose of this study was to assess the contribution of various pacing and pharmacologic techniques to uncover VA conduction during apparent unidirectional VA block, and to evaluate the role of several biologic and electrophysiologic factors in concealment of retrograde conduction. Forty healthy dogs underwent catheter-electrophysiologic studies of AV and VA conduction. Group I (20 animals) had intact VA conduction. Group II (six animals) had VA dissociation with ventricular pacing initiated during sinus rhythm, but the presence of VA conduction was confirmed by isoproterenol infusion or by premature ventricular stimulation. In group III (14 animals), the above techniques failed to uncover VA conduction. Eight of 14 group III animals underwent thoracotomy and crushing or freezing of the sinoatrial (SA) node. Ventricular pacing initiated during sinus standstill was associated with 1:1 VA conduction in each experiment. VA conduction time and retrograde Wenckebach cycle length, both in the baseline state and during isoproterenol infusion, were significantly longer in the eight animals in group III than in those in group I. Age, gender, weight, breed, sinus cycle length, and anterograde AV conduction properties were not significantly different between groups I, II, and III. The data suggest that (1) in normal dogs, complete unidirectional VA block probably does not exist; (2) in the presence of anterograde input to the AV node, even sophisticated pacing and pharmacologic maneuvers may fail to uncover the presence of VA conduction; (3) although anterograde input is essential for concealment of VA conduction, the phenomenon is more closely associated with depressed retrograde than with anterograde AV nodal characteristics.(ABSTRACT TRUNCATED AT 250 WORDS)

Fulguration for AV nodal tachycardia: results in 42 patients with a mean follow-up of 23 months

This report describes a catheter ablation technique to treat atrioventricular nodal reentrant tachycardia while preserving anterograde conduction, and its application in 42 patients with drug-refractory repetitive episodes of tachycardia. One of these patients had common and reverse forms of tachycardia. Using atrial activation in the His-bundle lead as a reference, the optimal ablation site was selected by positioning an electrode catheter to obtain a synchronous or earlier atrial activation than the reference during tachycardia. At this site, His-bundle deflection was completely absent, or was present at a low amplitude (less than 0.1 mV). In the majority of patients, these criteria were found in the immediate vicinity of the site of proximal His-bundle recording (adjacent to the reference catheter). Shocks of 160 or 240 joules (J) were delivered at this site (mean +/- SD = 518 +/- 392 J/session) with a resulting preferential abolition of impairment of fast retrograde conduction. Anterograde conduction, though modified, was preserved in all patients, except for four (10%) patients who remained in complete heart block. Thirty patients (70%) remained free of arrhythmia without medication or pacemaker for a mean follow-up period of 23 +/- 13 (2-63) months. Six other patients (15%) were controlled with a previously ineffective medication.

Long-term follow-up of patients after transcatheter direct current ablation of the atrioventricular junction

The long-term follow-up study (41 +/- 23 months) of 47 patients undergoing direct current ablation because of drug-resistant supraventricular arrhythmias is reported. Significant early complications occurred in four patients and included hypotension, pericarditis, nonsustained polymorphic ventricular tachycardia and one sudden death. In 42 patients (86%), complete atrioventricular (AV) block was initially achieved. During the follow-up period, AV conduction resumed in 2 of these 42 patients. Of the seven patients in whom ablation was unsuccessful, two developed late complete AV block and three had symptomatic improvement. An improved activity level was reported among 83% of the patients with successful ablation. Health care utilization manifest as the number of hospital admissions per year before and after ablation decreased significantly after ablation (2.4 +/- 2.0 versus 0.3 +/- 0.5, p less than 0.001). Echocardiographic evaluation in five patients with a depressed left ventricular ejection fraction (27 +/- 7%) before ablation showed a significant increase (45 +/- 14%, p less than 0.05) after an average follow-up period of 31 months. New onset of congestive heart failure occurred after ablation in four patients, of whom two had no structural heart disease. The total mortality rate, including the one patient with sudden death, was 17% and was significantly higher among patients with underlying structural heart disease. Transcatheter direct current ablation is an effective treatment in patients with drug-resistant supraventricular tachycardia, providing a beneficial long-term outcome including an improved quality of life and a decrease in health care utilization.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical efficacy of radiofrequency current in the treatment of patients with atrioventricular node reentrant tachycardia

Eight women (mean age 41 years, range 24 to 62) with drug-resistant atrioventricular (AV) node reentrant tachycardia underwent radiofrequency catheter ablation. Radiofrequency energy was delivered in a unipolar mode with use of a back paddle as the anode placed between the two scapulae. The total applied energy was 2,233 +/- 1,919 J. The AH interval increased from 87 +/- 13 to 113 +/- 17 ms (p less than 0.05) and the PQ interval increased from 141 +/- 15 to 169 +/- 34 ms (p less than 0.05). The anterograde Wenckebach cycle length increased from 300 +/- 41 to 320 +/- 42 ms (p less than 0.05). Retrograde conduction was abolished in five patients. Atrioventricular node tachycardia was still inducible in three patients. During a follow-up period of 9 +/- 3 months, four patients remained clinically asymptomatic without drug therapy and four patients had recurrent symptoms. Three of the latter responded to previously unsuccessful antiarrhythmic drugs and the fourth patient underwent surgical cure for persistence of tachycardia. Right bundle branch block occurred in five patients; it was permanent in four and transient in one. In conclusion, radiofrequency catheter ablation represents a valuable but still investigational therapy in patients with drug-refractory AV node reentrant tachycardia.