Supraventricular nonreentrant tachycardia due to simultaneous conduction through dual atrioventricular nodal pathways

Tachycardia-Induced Cardiomyopathy

This is a typical example of a tachycardia-induced cardiomyopathy due to incessant tachycardia with moderately increased ventricular rate. This was due to nonreentrant atrioventricular nodal tachycardia that gave rise to two ventricular complexes for every atrial complex. It describes a rare finding of the presence of retrograde concealed conduction in the fast pathway. Curative catheter ablation led to improvement of symptoms with reversal of tachycardia-induced cardiomyopathy.

Doubling of the ventricular rate by interpolated junctional extrasystoles resembling supraventricular tachycardia

In a study of seven cases of paroxysmal supraventricular tachycardia, it was noted that the fast rate was not caused by the mechanism of rapid firing, reentry, or dual atrioventricular nodal conduction but by an abrupt doubling of the rate by interpolation of junctional extrasystoles between adjacent sinus beats while the sinus mechanism remained undisturbed. Dual ventricular response to a single atrial depolarization was seriously considered in each case. The intervals separating the junctional extrasystoles tended to be quite fixed, thus conforming to the pattern of junctional parasystole with an intrinsic rate very close to the rate of the dominant sinus rhythm. The paroxysms of tachycardia were transient, lasting a few seconds to 3.5 minutes. The onset and termination of the paroxysms were completely unpredictable and appeared unrelated to any change in the basic sinus rate or other identifiable mechanism. In only one case, case 7, the concept of dual ventricular response appeared tenable. However, as will be discussed later, the mechanism of junctional parasystole was found to be physiologically more acceptable.

Nonreentrant supraventricular tachycardia misdiagnosed as inappropriate sinus tachycardia

We report a case of a woman with incessant palpitations initially misdiagnosed as inappropriate sinus tachycardia that proved refractory to β-blockers. At the time of electrophysiologic testing, a sustained narrow-complex tachycardia with a 1:2 atrioventricular relationship was repeatedly initiated by a posterior fascicle depolarization induced by means of a timed ventricular extrastimulus. The tachycardia was repeatedly terminated with a timed atrial extrastimulus, which excluded junctional bigeminy and confirmed the diagnosis of nonreentrant supraventricular tachycardia. Catheter ablation of the slow pathway eliminated dual-pathway conduction and tachycardia.

Nonreentrant atrioventricular nodal tachycardia due to triple nodal pathways manifested by radiofrequency ablation at coronary sinus ostium

We report a case of complex supraventricular tachycardia manifested by radiofrequency delivery. Initially, the patient presented with orthodromic atrioventricular reentrant tachycardia via a left-sided accessory pathway that was successfully eliminated. Atrial tachycardia originating from coronary sinus ostium was also induced. Radiofrequency delivery at the coronary sinus ostium induced a narrow QRS tachycardia with irregular R-R intervals. A detailed analysis explained that the tachycardia could be a nonreentrant mechanism due to triple atrioventricular nodal pathways: an atrial excitation evokes double ventricular response due to simultaneous activation of the fast and slow pathways, and the next one activates ventricle through the intermediate pathway.

Simultaneous Dual Fast and Slow Pathway Conduction upon Induction of Typical Atrioventricular Nodal Reentrant Tachycardia: Electrophysiologic Characteristics in a Series of Patients

INTRODUCTION

Simultaneous dual atrioventricular nodal conduction (SDNC) through slow (SP) and fast pathway (FP) is a rare phenomenon observed upon the induction of atrioventricular nodal reciprocating tachycardia (AVNRT). The aim of this study is to report the electrophysiological features of patients showing typical AVNRT induced through SDNC.

METHODS AND RESULTS

Among 461 consecutive patients with typical AVNRT submitted to radiofrequency catheter ablation (RFCA), seven patients (1.5%) with SDNC at tachycardia onset (group I: 6 female; age 60-72 years, mean 65.2 +/- 3.8 years) and 118 age-matched controls (group II: 60 female; age 60-88 years, mean 68.4 +/- 6.8 years) were considered. Controls were further subdivided into two subgroups according to age: subgroup A (94 patients, age 60-75 years) and subgroup B (24 patients, age >75 years). The value of the following parameters was significantly higher in group I than in group II and in subgroup A: A-H interval [113 +/- 26 vs. 89 +/- 27 (P < 0.01) vs. 84 +/- 19 (P < 0.001)], ventriculoatrial conduction effective refractory period [355 +/- 85 vs. 293 +/- 87 (P < 0.05) vs. 281 +/- 82 (P < 0.05)], SP conduction time upon AVNRT induction [444 +/- 104 vs. 350 +/- 72 (P < 0.01); vs. 345 +/- 67 (P < 0.001)], AVNRT cycle length [484 +/- 103 vs. 396 +/- 71 ms (P < 0.05); vs. 384 +/- 69 (P < 0.05)], and rate of AVNRT induction from ventricle [71% vs. 10% (P = 0.001); vs. 6% (P = 0.001)]. Differences were mostly not significant between group I and subgroup B. SP location and RFCA success rate were similar in all groups.

CONCLUSION

In a population of AVNRT patients, SDNC at AVNRT induction is infrequent and it prevails beyond the fifth decade of life and in females. SDNC is associated with peculiar AVN conduction features, which resemble the age-related modifications of AVN conduction.

Dual Conduction in a Mahaim Fiber

The case of an 8-year-old girl with incessant nonsustained left bundle branch block-like tachycardia refractory to antiarrhythmic drug therapy is reported. Electrophysiologic study revealed the presence of a right-sided accessory atriofascicular pathway. Episodes of nonsustained tachycardia were found to be based upon a dual response in AV conduction over the Mahaim fiber to one P wave. No reentrant tachycardia could be induced. The arrhythmia was cured by catheter ablation targeting a Mahaim potential at the right lateral tricuspid annulus. The findings can be explained by longitudinal dissociation in a single Mahaim fiber, a fiber distally diverging into two fibers with different conduction times, or (less likely) two closely located Mahaim fibers with different conduction times.

Dual Antegrade Response Tachycardia Induced Cardiomyopathy

We report a rare case of tachycardia induced cardiomyopathy resulting from nearly incessant dual antegrade response tachycardia. Criteria necessary for sustaining dual antegrade responses are discussed, including: (1) sufficient antegrade dissociation of the AV node; (2) absence of retrograde conduction over each AV nodal pathway following antegrade conduction over its counterpart; (3) difference between fast and slow pathway conduction times exceeding His-Purkinje refractoriness; and (4) critical timing of sinus impulses relative to preceding AV nodal conduction. Both the arrhythmia and cardiomyopathy were successfully treated by slow pathway ablation.

Incessant nonreentrant tachycardia due to simultaneous conduction over dual atrioventricular nodal pathways mimicking atrial fibrillation in patients referred for pulmonary vein isolation

It has been reported that conduction over the fast and slow pathways of the AV node can occur simultaneously, leading to a double ventricular response from each atrial beat. We report the cases of two patients referred to us for evaluation of symptomatic, incessant, and irregular narrow-complex tachycardia, misdiagnosed as atrial fibrillation, for consideration of pulmonary vein isolation. At presentation, careful evaluation of the electrograms revealed the presence of two ventricular activations for each atrial beat. At electrophysiologic study, both patients were found to have nonreentrant tachycardias arising from simultaneous conduction over the fast and slow pathways of the AV node. In one patient, the tachycardia had resulted in cardiomyopathy. Slow AV nodal pathway ablation performed in both patients resulted in cure of their tachycardias and recovery of ventricular function in the patient with cardiomyopathy.

Double ventricular response via dual atrioventricular nodal pathways resulting with nonreentrant supraventricular tachycardia and successfully treated with radiofrequency catheter ablation

We report a patient with a complex nonreentrant supraventricular tachycardia because of double ventricular response resulting from antegrade dual atrioventricular (AV) nodal pathways. We could induce double ventricular response and confirm dual AV nodal pathways by AV simultaneous pacing during basic stimulation proceeding with programmed atrial single extrastimulation. As far as we know, it is the first report about the application of the AV simultaneous basic stimulation to prove the sustained nonreentrant tachycardia because of simultaneous conduction over dual AV nodal pathways. This was also confirmed by absence of the arrhythmia immediately after the elimination of the slow pathway conduction by radiofrequency ablation.

Incessant nonreentrant atrioventricular nodal tachycardia due to multiple nodal pathways treated by radiofrequency ablation of the slow pathways

In patients with dual AV nodal physiology, simultaneous anterograde fast and slow pathway conduction resulting in an unusual form of nonreentrant AV nodal tachycardia has been observed. We describe the case of a young patient with an incessant form of complex supraventricular tachycardia who underwent electrophysiologic evaluation, which showed simultaneous conduction via multiple AV nodal pathways that caused a unique form of incessant nonreentrant AV nodal tachycardia. Radiofrequency ablation of the spatially closed intermediate and slow pathways effectively treated the tachycardia. The electrophysiologic determinants of simultaneous conduction through the multiple nodal pathways and the apparently different behavior of the fast pathway before and after ablation are discussed.

Paroxysmal supraventricular tachycardia caused by 1:2 atrioventricular conduction in the presence of dual atrioventricular nodal pathways

One-to-two atrioventricular conduction, ie, the double response to a single sinus or atrial impulse, resulting in two QRS complexes for one P wave, is a rare manifestation of dual atrioventricular (AV) nodal pathways. This report describes the case of a 61-year-old woman with continuous episodes of supraventricular tachycardia caused by independent conduction to the ventricles of sinus impulses over both the fast and the slow AV nodal pathway, giving rise to a ventricular rate that was twice the sinus rate. A wide spectrum of electrocardiographic manifestations of 1:2 AV conduction was observed on the surface electrocardiogram. The diagnosis was suggested by several elements including evidence of dual AV nodal pathways during sinus rhythm and cycle length alternans during tachycardia. The patient underwent successful slow pathway ablation with complete disappearance of symptoms and electrocardiographic manifestations of 1:2 AV conduction.

Association between nonreentrant supraventricular tachycardia and atrioventricular node reentrant tachycardia: a presentation of dual AV node physiology

Persistent simultaneous conduction of P waves over a fast and a slow nodal pathway defines the nonreentrant type of supraventricular tachycardia, usually not associated with reciprocating movements. We report a unique association between this uncommon tachycardia and a usual AV nodal reentrant tachycardia, made possible by the existence of three different nodal pathways.

One-to-two atrioventricular conduction causing nonreentrant tachycardia: successful treatment with radiofrequency ablation

The anatomical substrate for AV nodal reentrant tachycardia (AVNRT) is well known and is due to anterograde conduction through a slow conducting pathway and retrograde conduction using a fast conducting pathway. In this report, we describe a patient with AVNRT who also presented with frequent episodes of paroxysmal nonreentrant tachycardia due to the occurrence of two conducted ventricular beats for each sinus depolarization. Palpitations and arrhythmias were abolished after radiofrequency ablation of the slow pathway.

Electrocardiographic manifestations of dual atrioventricular node conduction during sinus rhythm

OBJECTIVES

The objective of this study was to correlate electrocardiographic (ECG) PR interval changes during normal sinus rhythm with recent observations regarding the anatomy and physiology of the dual, slow and fast atrioventricular (AV) pathways.

BACKGROUND

The least common manifestation of dual AV conduction is an abrupt PR interval change in the setting of sinus rhythm. Whereas isolated cases of this phenomenon have been reported, the relatively large series we have collected makes it possible to correlate the ECG findings with the anatomy, composition and electrophysiology of the dual AV pathways.

METHODS

The ECGs of 21 patients with sinus rhythm and PR interval changes consistent with dual AV node physiology were studied. Observations include duration of the short and long PR intervals, the difference between the two and the events responsible for the PR interval change.

RESULTS

Eighteen of the 21 ECGs exhibited an abrupt and persistent PR interval change. Two of the other three ECGs manifested PR interval alternans, with slow and fast pathway, and a Wenckebach type I AV block; in the third ECG, findings compatible with simultaneous conduction along both pathways in response to a single stimulus were noted. Events responsible for the PR change included atrial premature complexes, atrial tachycardia, interpolated ventricular premature complexes and interpolated junctional premature complexes. In two the PR interval change appeared during a regular sinus rhythm.

CONCLUSIONS

The behavior of the PR interval is consistent with dual AV conduction. The PR interval duration hypothesized to represent slow pathway conduction is in keeping with the calculated anatomic length of the slow pathway. The Wenckebach type I block in the slow and fast pathways, as well as the altered conduction time in the slow pathway parallel with changing sinus rate, is evidence that the pathway is influenced by autonomic (?parasympathetic) innervation, supporting the premise that the pathways contain AV node-like tissue.

Nonreentrant supraventricular tachycardia due to double ventricular response via dual atrioventricular nodal pathways

Narrow and wide QRS tachycardias associated with various rhythm disturbances were recognized during 24-hour ambulatory eletrocardiographic monitoring in a 65-year-old man with coronary artery disease. Laddergram analysis revealed the presence of dual atrioventricular nodal pathways. Non-reentrant supraventricular tachycardia due to simultaneous fast and slow conduction through the dual atrioventricular nodal pathways was confirmed by electrophysiologic study. The atrial rate determined the occurrence of simultaneous conduction, and extrastimulation failed to induce a double ventricular response. Enhanced vagal activity was thought to play a critical role in provoking this phenomenon. Radiofrequency catheter ablation of the slow pathway eliminated the arrhythmias.

Nonreentrant supraventricular tachycardia due to simultaneous conduction over fast and slow AV node pathways: successful treatment with radiofrequency ablation

A 55-year-old woman with frequent problematic supraventricular tachycardia is presented. The tachycardia was irregular with predominantly normal QRS morphology and was refractory to multiple antiarrhythmic drugs. At electrophysiology study, the tachycardia was inducible with atrial or ventricular extrastimuli and dual pathways were observed. In contrast to the situation usually seen with dual atrioventricular node physiology, the slow pathway had a longer effective refractory period than the fast pathway and reentrant tachycardia was not induced. Simultaneous conduction over the fast and slow pathways during sinus rhythm was shown to be the mechanism for clinical tachycardia. The tachycardia was successfully treated using radiofrequency ablation of the slow pathway.

Double Ventricular Responses to a Single Atrial Depolarization in a Patient with Dual AV Nodal Pathways

Electrophysiological study was performed in a patient with atrioventricular nodal reentrant tachycardia (AVNRT). Double ventricular responses through dual AV nodal pathways were observed by atrial extrastimulus technique followed by initiation of AVNRT. The difference in conduction time between the slow and fast AV nodal pathways was longer than 320 msec. A ventricular extrastimulus delivered during sinus rhythm, which was not followed by ventriculoatrial conduction, also induced AVNRT. These findings indicated the presence of an antegrade critical delay and retrograde block in the slow AV nodal pathway, criteria necessary for the occurrence of a double ventricular response.

Paroxysmal nonreentrant supraventricular tachycardia due to simultaneous fast and slow pathway conduction in dual atrioventricular node pathways

Electrophysiologic studies were performed on a 49 year old woman who had paroxysmal nonreentrant supraventricular tachycardia due to simultaneous anterograde conduction through dual atrioventricular (AV) node pathways. Slow pathway conduction was inversely related to the preceding sinus cycle length and fast pathway conduction was determined by the Hs-A interval (measured from the His potential due to slow pathway conduction to the onset of the subsequent atrial electrogram). Major determinants of sustained simultaneous anterograde fast and slow pathway conduction during sinus rhythm were 1) a retrograde unidirectional block in both fast and slow pathways, and 2) a critical conduction delay in the slow pathway and a long enough Hs-A interval to allow sequential conduction of impulse from both pathways. Flecainide was successful in preventing recurrences of the tachycardia by eliminating slow pathway conduction during long-term follow-up.

Pseudosimultaneous fast and slow pathway conduction: a common electrophysiologic finding in patients with dual atrioventricular nodal pathways

Two ventricular responses following termination of rapid atrial pacing were noted in 24 of 87 patients with dual atrioventricular (AV) nodal pathways and supraventricular tachycardia. In all 24 patients, the AH intervals of the first and second ventricular responses were comparable with those of the fast and slow pathways, respectively. Careful analysis of the whole pacing sequence revealed that, in 21 patients, this phenomenon resulted from sustained slow pathway conduction with long AH intervals. In these patients, as the AH interval of each paced beat was progressively lengthened during pacing, the corresponding His bundle and ventricular responses were pushed one cycle behind the current atrial paced beat, so that the last paced beat was followed by two His bundle and ventricular responses. In only three patients did double ventricular responses result from simultaneous fast and slow pathway conduction. One of these three patients also showed two ventricular responses resulting from sustained slow pathway conduction. Several factors predispose to the occurrence of this phenomenon in patients with dual AV nodal pathways. These include an ability to sustain slow pathway conduction, a longer slow pathway AH interval, a shorter sinus AH interval (fast pathway) and a shorter atrial paced cycle length that sustains slow pathway conduction. In conclusion, sustained slow pathway conduction with resultant long AH intervals is the mechanism of two ventricular responses following termination of atrial pacing in most patients with dual AV nodal pathways. This phenomenon should be distinguished from the rare occurrence of double ventricular responses to an atrial impulse due to simultaneous fast and slow pathway conduction.

Determinants of simultaneous fast and slow pathway conduction in patients with dual atrioventricular nodal pathways

Double His bundle and ventricular responses to a single atrial impulse caused by a simultaneous fast and slow pathway conduction was observed during electrophysiologic study in three patients with dual-pathway atrioventricular nodal reentrant paroxysmal supraventricular tachycardia. In patient No. 1 this phenomenon occurred during rapid atrial pacing, in patient No. 2 during both rapid atrial pacing and delivery of a single atrial extrastimulus, and in patient No. 3 during delivery of double atrial extrastimuli. Retrograde unidirectional block in the slow pathway was suggested by retrograde induction of tachycardia at a long ventricular paced cycle length and/or long ventricular coupling interval in all three patients. Our findings suggest that major determinants of this phenomenon include: a sufficient conduction delay in the slow pathway so that the distal tissue is able to respond for the second time, and a retrograde unidirectional block in the slow pathway so that the fast pathway impulse will not enter and collide with the oncoming slow pathway impulse.

Unusual mechanism of PR interval variation and nonreentrant supraventricular tachycardia as manifestation of simultaneous anterograde fast and slow conduction through dual atrioventricular nodal pathways

Noninvasive recordings in a 69-year-old woman showed two distinct PR intervals of about 0.21 and 0.58 s, suggestive of dual AV nodal conduction. Various unusual mechanisms of transition from short to long and from long to short conduction intervals and phenomena of concealed conduction were due to the presence of two functionally separated intranodal pathways. Refractoriness of the slow pathway was associated with bradycardia. Episodes of tachycardia exhibited a one-to-two relationship between P-waves and ventricular activations as a consequence of simultaneous anterograde fast and slow conduction leading to double ventricular responses to single P-waves.

Double atrial responses to a single ventricular impulse due to simultaneous conduction via two retrograde pathways

Electrophysiologic studies were performed in two patients. In one patient (Case 1) with ventricular pre-excitation and paroxysmal supraventricular tachycardia, studies after diltiazem administration showed two QRS responses to a single atrial stimulus during atrial pacing at a cycle length of 300 ms. The first QRS response with full pre-excitation and short PR interval was consistent with accessory pathway conduction, while the second QRS response with a normal duration and an atrio-His bundle interval of 350 ms was consistent with normal pathway conduction. The second QRS response was followed by initiation of supraventricular tachycardia. Studies after verapamil administration on a separate day disclosed two atrial responses to a single QRS complex during ventricular pacing at cycle lengths between 330 and 280 ms, suggesting simultaneous retrograde accessory and normal pathway conduction. In Case 2 with a supraventricular tachycardia using a fast atrioventricular nodal pathway for anterograde and a slow ventriculoatrial pathway for retrograde conduction, two atrial responses to a single QRS complex were observed during ventricular pacing at cycle lengths between 500 and 400 ms. The first atrial response showed a stimulus to atrial interval of 120 ms and an atrial activation sequence with the low septal right atrium being earlier than other atrial sites, suggesting retrograde fast pathway conduction. The second atrial response showed a stimulus to atrial interval of 505 ms and an atrial activation sequence with low septal right atrium being simultaneous with the proximal coronary sinus, suggesting retrograde slow pathway conduction.(ABSTRACT TRUNCATED AT 250 WORDS)