"Incessant" atrioventricular (AV) reciprocating tachycardia utilizing left lateral AV bypass pathway with a long retrograde conduction time

A permanent junctional reciprocating tachycardia with an atypically located accessory pathway successfully ablated from within the middle cardiac vein

Permanent form of junctional reciprocating tachycardia (PJRT) is an uncommon form of atrioventricular re-entrant tachycardia due to an accessory pathway characterized by slow and decremental retrograde conduction. The majority of accessory pathways in PJRT are localized in the posteroseptal zone. Despite the high success rate, failure may occur during endocardial radiofrequency catheter ablation due to epicardial insertion of the accessory pathway. We report a case of PJRT in a 25-year-old man in whom the accessory pathway was located epicardially in the posteroinferior region and ablated from within the middle cardiac vein by radiofrequency catheter ablation.

Electrophysiological characteristics and radiofrequency ablation of accessory pathways with slow conductive properties

BACKGROUND

Atrioventricular accessory pathways (AP) with unusually long ventriculo-atrial (VA) conduction times are present in a significant subset of patients with the Wolff-Parkinson-White (WPW) syndrome, not including patients with the permanent form of atrioventricular junctional reciprocating tachycardia.

METHODS AND RESULTS

We compared the electrophysiological characteristics and outcomes after radiofrequency (RF) ablation in 34 patients with the WPW syndrome, a VA interval >80 ms, and paroxysmal tachycardia with an RP/PR ratio <1 (the slow group), vs 80 patients with WPW syndrome and a VA interval <80 ms (the fast group). AP were found in the posteroseptal region significantly more often in the slow than in the fast group. In addition, the decremental conductive properties of the AP were more common in the slow than in the fast group. Catheter ablation of AP was highly successful in both groups, although ablation required a greater number of RF applications and longer procedure times in the slow group, especially for AP with decremental conductive properties.

CONCLUSIONS

A posteroseptal AP location was more common in AP associated with long conduction times than in AP with typical conductive properties. Both types of AP were successfully ablated, although the slow group required longer procedures and more RF energy deliveries.

Double atrial responses to a single ventricular impulse in long RP' tachycardia

Double atrial responses (DARs) to a single ventricular impulse have been described in patients with long RP' tachycardia. To define the determinants for the occurrence of DARs, 8 cases with long RP' tachycardia were examined. The mechanism of long RP' tachycardia was the orthodromic atrioventricular reciprocating tachycardia (AVRT) involving a slow conducting concealed accessory pathway in 4 cases and uncommon (fast-slow) type of atrioventricular nodal reentrant tachycardia (AVNRT) in the other 4 cases. Programmed and rapid ventricular pacing was performed during sinus rhythm and also rapid ventricular pacing during tachycardia (i.e., entrainment). The retrograde effective refractory period (ERP) and the retrograde maximal 1:1 conduction rate of the fast and slow conducting pathways were examined. In 1 of the 4 cases with AVRT, DARs were observed during programmed and rapid ventricular pacing, performed during sinus rhythm and also during entrainment. In 1 of the 4 cases with AVNRT, DARs were observed only during entrainment. The determinants of DARs in cases with long RP' tachycardia were: (1) presence of two different retrogradely conducting pathways; (2) short ERP of the retrograde fast and slow conducting pathways and a short minimal pacing cycle length at which 1:1 ventriculoatrial conduction occurs via these pathways; (3) crucial conduction delay in the slow conducting pathway; and (4) preexisting antegrade unidirectional block in the slow conducting pathway or the antegrade block in the slow conducting pathway produced by collision with a previous retrograde impulse during entrainment.

Catheter ablation of permanent junctional reciprocating tachycardia with radiofrequency current

OBJECTIVES

This study evaluated accessory pathway location, its relation to retrograde P wave polarity on the surface electrocardiogram and radiofrequency ablation efficacy and safety in a large group of patients with permanent junctional reciprocating tachycardia.

BACKGROUND

Permanent junctional reciprocating tachycardia is an uncommon form of reciprocating tachycardia, almost incessant from infancy and usually refractory to drug therapy. It is characterized by RP > PR interval and usually by negative P waves in leads II, III, aVF and V4 to V6. Retrograde conduction occurs through an accessory pathway with slow and decremental properties. Although this accessory pathway has been classically located in the posteroseptal zone, other locations have been recently reported.

METHODS

The study included 32 patients (20 men, 12 women, mean [+/- SD] age 29 +/- 15 years) with a diagnosis of permanent junctional reciprocating tachycardia confirmed at electrophysiologic study. Seven patients had depressed left ventricular function. Radiofrequency energy was applied at the site of the earliest retrograde atrial activation during tachycardia.

RESULTS

There were 33 accessory pathways. The site of the earliest retrograde atrial activation was posteroseptal in 25 patients (76%), midseptal in 4 (12%), right posterior in 1 (3%), right lateral in 1 (3%), left posterior in 1 (3%) and left lateral in 1 (3%). Thirty pathways were ablated with a right approach; in 11 patients with posteroseptal pathway the ablation was performed through the coronary sinus. Three pathways were ablated with a left approach. Positive retrograde P wave in lead I suggested that ablation could be performed from the right side; if negative, it did not exclude ablation from this approach. All the accessory pathways were successfully ablated, with a median of 3 and a mean of 5.6 +/- 5 radiofrequency applications of 70 +/- 26 s in duration. In two patients with the accessory pathway in the midseptal zone, a transient second- and third-degree atrioventricular block, respectively, was observed after ablation. At a mean follow-up of 18 +/- 12 months, 31 patients (97%) are asymptomatic without antiarrhythmic therapy (95% confidence interval [CI] 84% to 99%). Recurrences were observed in four patients (13%) (95% CI 4% to 29%), three of whom had the accessory pathway ablated successfully at a second session. All patients with depressed left ventricular function showed a marked improvement after successful ablation.

CONCLUSIONS

In our experience, most of the patients with permanent junctional reciprocating tachycardia had posteroseptal pathways; all these pathways were ablated from the right side. P wave configuration may be helpful in suggesting the approach to the site of ablation. Catheter ablation using radiofrequency energy is an effective therapy for permanent junctional reciprocating tachycardia.

Radiofrequency ablation therapy in concealed left free wall accessory pathway with decremental conduction

An electrophysiologic study followed by transcatheter radiofrequency ablation therapy was performed in two adult patients with a permanent form of junctional tachycardia. Both patients had no structural heart disease and exhibited a normal resting ECG. The P wave during tachycardia was negative in leads 1, 3, and aVF, biphasic over V6, and positive in V1 and aVL in both patients, while the P-R/R-P interval ratio during tachycardia was 0.82 and 0.36, respectively, in both patients. Both patients displayed an eccentric atrial activation sequence with the earliest atrial activation occurring at the distal coronary sinus and a decremental retrograde conduction property during incremental ventricular pacing, suggesting the presence of a concealed slowly conducting left free wall accessory pathway. The tachycardia used the normal atrioventricular pathway for anterograde conduction and the concealed show left accessory pathway for retrograde conduction. It was terminated following adenosine administration in both patients; termination of tachycardia was due to a block in the retrograde accessory pathway in one patient and due to a block in the atrioventricular node in the other patient. Radiofrequency ablation was performed by the retrograde transaortic approach. The radiofrequency f4p4ent was delivered to the site of the earliest atrial activation during tachycardia at the ventricular aspect of the mitral annulus. The successful ablation site had a ventriculoatrial (VA) interval of 120 and 130 ms, respectively, and was located at the posterolateral and lateral aspects of the mitral annulus. Following ablation, there was no VA conduction; however, conduction through the normal atrioventricular pathway was noted during isoproterenol infusion in both patients. There was no induction of tachycardia. This study demonstrates that the permanent form of junctional tachycardia in adults can incorporate a concealed left free wall accessory pathway with a decremental property. Radiofrequency ablation therapy is effective and safe in this form of arrhythmia.

Diagnosis and localization of accessory pathways

The WPW syndrome is a curable disease. The evolution of nonpharmacological methods of accessory pathway ablation has had a significant impact on management strategies in patients with arrhythmias mediated by accessory pathways. Despite an incidence of preexcitation in the general population of 0.1% to 0.3%, curative therapy is underutilized. This review has highlighted the traditional and newer methods of diagnosing and localizing accessory pathways. The number of patients benefiting from definitive therapy will parallel increased physician awareness of these methods.

Atrioventricular block in the atypical form of junctional reciprocating tachycardia: evidence supporting the atrioventricular node as the site of reentry

Serial electrophysiologic studies were performed in 19 patients with the atypical form of supraventricular tachycardia having a long RP and short PR interval. In all 19 patients, supraventricular tachycardia was found to have a 1:1 P-QRS relation during initial control electrophysiologic studies, and in all 19 patients, electrophysiologic studies suggested that junctional reentry was the mechanism of supraventricular tachycardia. Seven of the 19 patients developed atrioventricular (AV) block during initiation of supraventricular tachycardia or after induction of supraventricular tachycardia following various drug administrations in subsequent studies. In three patients, second degree block within the His bundle or block distal to the His bundle recording site occurred after administration of quinidine. In one patient it occurred after procainamide, and in another patient it occurred after atropine. In one patient, 2:1 block proximal to the His deflection occurred after verapamil. In the remaining patient, a transient Wenckebach block proximal to the His deflection was noted after adenosine triphosphate. In this latter patient, 2:1 AV block was also noted after propranolol and digoxin. The site of reentry in these seven patients with AV block during supraventricular tachycardia was confined to the AV node area. Their supraventricular tachycardia did not involve a slowly conducting paraseptal accessory pathway because the distal AV node, His bundle and ventricle were not found to be necessary links in the tachycardia circuit.

Permanent form of junctional reciprocating tachycardia with only even-numbered beats

An analysis of the electrocardiogram of a patient with the permanent form of junctional reciprocating tachycardia is presented. The patient demonstrated near-incessant tachycardia, with a 1:1 atrioventricular relationship and a retrograde P wave (P') occurring closer to the succeeding QRS complexes (ie, with a P'R interval that is shorter than the RP' interval). Each tachycardia episode was characterized by alternating short and long cardiac cycles due to alternation of retrograde conduction time (RP' interval), retrograde Wenckebach periodicity, and an even number of ectopic P' waves. The authors propose that there is an accessory AV connection with decremental functional properties that arborizes into two atrial branches with different conduction times. The fast branch initially exhibits a 3:2 retrograde conduction block followed by a cycle length-dependent 2:1 retrograde conduction block, thereby permitting alternate use of the slow branch, which is the weakest component of the reciprocating process.

Use of transient entrainment during ventricular tachycardia to localize a critical area in the reentry circuit for ablation

We have previously shown that demonstration of any of the criteria for transient entrainment is possible only when pacing is performed orthodromically proximal to the area of slow conduction in a reentrant circuit with an excitable gap. Pacing orthodromically distal to the area of slow conduction will not permit demonstration of the transient entrainment criteria (concealed entrainment). Additionally, the demonstration of one form of concealed entrainment, namely pacing during a ventricular tachycardia from a site which increases the tachycardia to the pacing rate but does not change the morphology of the QRS complexes, we suggest also identifies the area of slow conduction is a keystone for maintenance of the reentrant circuit, ablation of this area should be expected to provide effective therapy of the tachycardia. Thus, we propose that using the principles of transient entrainment, one should be able to localize a critical area of slow conduction in the reentrant circuit of a ventricular tachycardia, ablate it effectively, and thereby successfully treat the ventricular tachycardia.

Differential electrophysiologic properties of decremental retrograde pathways in long RP' tachycardia

Long RP' supraventricular tachycardias (SVT) often demonstrate both slow and decremental conduction properties in the retrograde pathway of the reentrant circuit. The electrophysiologic properties of these pathways are poorly understood. We studied 10 patients with long RP' SVT (RP'/RR, 0.52 to 0.71); five had the unusual form of atrioventricular nodal reentry (fast-slow) and five patients had accessory AV pathways with slow, decremental retrograde conduction properties. During SVT, the effects of intravenous adenosine (37.5 to 150 micrograms/kg), which increases potassium current (iK) in supraventricular tissue and hyperpolarizes membrane potential toward Ek (-90 mV), and the response to slow-inward channel blockade with verapamil (0.10 to 0.20 mg/kg iv) were evaluated. Adenosine and verapamil has similar effects in the presence of fast-slow AV nodal reentry since both agents terminated SVT by producing block in the retrograde slow AV nodal pathway. In contrast, adenosine and verapamil had differential effects on retrograde conduction in decremental accessory pathways. Adenosine terminated all episodes of SVT in the retrograde decremental pathway, whereas verapamil had a direct effect on this tissue in only two of five patients. Decremental retrograde accessory pathways can therefore demonstrate at least two types of electrophysiologic responses. Pathways that respond only to adenosine-induced hyperpolarizing K+ current likely comprise depressed fast-Na+ channel tissue, i.e., partially depolarized (greater than -60 to -70 mV) atrial tissue. In contrast, decremental accessory pathways that respond to both modulation of the slow-inward calcium current and K+ conductance have pharmacologic properties similar to those of the AV node and may represent more completely depolarized atrial fibers with resting membrane potentials of -60 mV or less.