Electrophysiological characteristics of junctional rhythm during ablation of the slow pathway in different types of atrioventricular nodal reentrant tachycardia

BACKGROUND: Junctional rhythm (JR) is commonly observed during radiofrequency (RF) ablation of the slow pathway for atrioventricular (AV) nodal reentrant tachycardia. However, the atrial activation pattern and conduction time from the His-bundle region to the atria recorded during JR in different types of AV nodal reentrant tachycardia have not been fully defined. METHODS: Forty-five patients who underwent RF ablation of the slow pathway for AV nodal reentrant tachycardia were included; 27 patients with slow-fast, 11 patients with slow-intermediate, and 7 patients with fast-slow AV nodal reentrant tachycardia. The atrial activation pattern and HA interval (from the His-bundle potential to the atrial recording of the high right atrial catheter) during AV nodal reentrant tachycardia (HA(SVT)) and JR (HA(JR)) were analyzed. RESULTS: In all patients with slow-fast AV nodal reentrant tachycardia, the atrial activation sequence recorded during JR was similar to that of the retrograde fast pathway, and transient retrograde conduction block during JR was found in 1 (4%) patient. The HA(JR) was significantly shorter than the HA(SVT) (57 +/- 24 vs 68 +/- 21 ms, P < 0.01). In patients with slow-intermediate AV nodal reentrant tachycardia, the atrial activation sequence of the JR was similar to that of the retrograde fast pathway in 5 (45%), and to that of the retrograde intermediate pathway in 6 (55%) patients. Transient retrograde conduction block during JR was noted in 1 (9%) patient. The HA(JR) was also significantly shorter than the HA(SVT) (145 +/- 27 vs 168 +/- 29 ms, P = 0.014). In patients with fast-slow AV nodal reentrant tachycardia, retrograde conduction with block during JR was noted in 7 (100%) patients. The incidence of retrograde conduction block during JR was higher in fast-slow AV nodal reentrant tachycardia than slow-fast (7/7 vs 1/11, P < 0.01) and slow-intermediate AV nodal reentrant tachycardia (7/7 vs 1/27, P < 0.01). CONCLUSIONS: In patients with slow-fast and slow-intermediate AV nodal reentrant tachycardia, the JR during ablation of the slow pathway conducted to the atria through the fast or intermediate pathway. In patients with fast-slow AV nodal reentrant tachycardia, there was no retrograde conduction during JR. These findings suggested there were different characteristics of the JR during slow-pathway ablation of different types of AV nodal reentrant tachycardia.     

Inducible atrioventricular nodal reentrant echo behind organic 2:1 infra-hisian block during sinus rhythm

A 77-year-old male patient with an intermittent 2:1 infra-Hisian block during sinus rhythm was presented with dizziness and near-syncope. During electrophysiological (EP) study, dual atrioventricular (AV) nodal pathways and retrograde fast pathway were easily induced by atrial and ventricular programmed stimulation, respectively. A typical slow-fast AV nodal reentrant echo beat also could be demonstrated by single atrial extrastimulation. Atrioventricular nodal reentrant tachycardia (AVNRT) can occasionally exhibit 2:1 AV block. Conversely, AV nodal reentry property had been rarely reported behind 2:1 infra-Hisian block. The EP presentation from this case may support the notion that tissues below the His are not part of the reentrant circuit of AVNRT.     

V-A block during atrioventricular nodal reentrant tachycardia: reentry confined to the AV node

Retrograde block during atrioventricular (AV) nodal reentrant tachycardia is considered a rare phenomenon that can potentially occur in the AV node or in the atrium. A patient with slow-fast AV nodal reentrant tachycardia and transient VA block localized in the AV node is presented. Pharmacological and stimulation maneuvers identified the site of block in the AV node and not in the atrium. Thus, AV nodal reentry can be confined to the AV node.     

Radiofrequency ablation of probable atrioventricular nodal reentrant tachycardia in children with documented supraventricular tachycardia without inducible tachycardia

The reproducible induction of supraventricular tachycardia (SVT) during electrophysiological study is critical for the diagnosis of atrioventricular nodal reentry tachycardia (AVNRT), and for determining a therapeutic endpoint for catheter ablation. In the sedated state, there are patients with reentry SVT due to AVNRT who are not inducible at electrophysiological study. This article reports on the empiric slow pathway modification for AVNRT in six pediatric patients (age 6-17, mean 13.3 years) with documented, recurrent, paroxysmal SVT in the setting of a structurally normal heart who were not inducible at electrophysiological study. Atrial and ventricular burst and extrastimulus pacing at multiple drive cycle lengths were performed in the baseline state, during an isuprel infusion, and during isuprel elimination. Single AV nodal (AVN) echo beats were present in all patients, while classic dual AVN physiology was present in three of six patients. Radiofrequency energy was administered in the right posteroseptal AV groove resulting in accelerated junctional rhythm in five of six patients. Postablation testing demonstrated the elimination of echo beats in four patients, while dual AVN physiology and echo beats persisted in two patients. At follow-up (22-49 months, mean 29.5 months), all patients are asymptomatic without recurrence of SVT and are not taking any antiarrhythmic medication. In selected patients, empiric slow pathway modification may be offered as a potential cure in children with recurrent paroxysmal SVT who are not inducible at electrophysiological study. Elimination of slow pathway conduction may serve as a surrogate endpoint, though is not necessary for long-term success.     

Cycle Length Alternation During Supraventricular Tachycardia: Occurrence and Mechanism in a Canine Model of AV Reentrant Tachycardia

Cycle length alternation (CLA) is commonly observed during supraventricular tachycardia (SVT) onset and termination. The present study was designed to gain insights into the mechanism and potential clinical relevance of CLA by comparing computer simulations of tachycardia to directly observed behavior in a canine model of AV reentrant tachycardia (AVRT). The computer model was based on the hypothesis that CLA is secondary to feedback between AV nodal output during SVT and subsequent AV nodal input, and used the measured anterograde AV nodal recovery curve (AV vs A1A2) to predict sequential AV and RR intervals during SVT. Orthodromic AVRT was created experimentally in 11 open-chested, autonomically-blocked (atropine plus nadolol) dogs using a sensing and pacing circuit that mimicked a retrograde-conducting accessory pathway. Steady-state cycle length and AV interval during experimental AVRT closely paralleled predictions made by the computer model. CLA appeared consistently at the onset of experimental AVRT at programmed VA intervals less than or equal to 100 msec (corresponding to VA less than or equal to 150 msec as measured clinically) in all dogs. The amplitude and duration of CLA increased as the VA interval decreased, and closely paralleled predictions based on the computer model. Abrupt accelerations in atrial pacing to the same rate as AVRT did not result in alternation of cycle length. In conclusion, alternation of cycle length results from feedback between AV nodal output and subsequent AV nodal input at the onset of reentrant supraventricular tachycardia, and does not require changes in autonomic tone or dual AV nodal pathways. CLA occurrence, amplitude, and duration are predictable based on AV node recovery properties, and depend on retrograde conduction properties of the reentrant circuit. The presence of CLA suggests that the AV node is an integral component of the SVT reentry circuit, and may be useful clinically to identify the mechanism of supraventricular tachycardias.     

Tachycardiomyopathy secondary to nonreentrant atrioventricular nodal tachycardia: recovery after slow pathway ablation

Nonreentrant atrioventricular (AV) nodal tachycardia is a rare form of arrhythmia due to simultaneous anterograde conduction in dual AV pathways, one atrial impulse triggering two ventricular complexes. We report the case of a 74-year-old man referred for incessant palpitations resistant to antiarrhythmic medication, and effort dyspnea. A nonreentrant AV nodal tachycardia is diagnosed with electrophysiological study. A dilated cardiomyopathy with left ventricular dysfunction is found with gated blood pool single-photon emission computed tomography. A radiofrequency catheter ablation of the slow pathway is successfully performed. The patient is reassessed 11 months after ablation. He is asymptomatic and left ventricular function has fully recovered.     

Pacing Maneuver in the Diagnosis of the Mechanism of Supraventricular Tachycardia

Pacing and entrainment maneuvers are essential for establishing the mechanism of supraventricular tachycardia (SVT), but may fail to do so if the SVT terminates or if pacing results in atrioventricular (AV) dissociation as opposed to entrainment of the arrhythmia. We present an unusual case of typical AV nodal reentrant tachycardia (AVNRT) with high degree AV block in which the diagnosis was confirmed using a novel maneuver consisting of simultaneous atrial and ventricular (A + V) pacing. The reproducible response to A + V pacing at varying cycle lengths established the diagnosis of AVNRT in this case. (PACE 2011; 34:e90–e93)     

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.     

Slow pathway ablation for atrioventricular nodal reentry using a right internal jugular vein approach: a case series

BACKGROUND: Inferior venous access to the right heart is not possible in some patients due to congenital or acquired obstruction of the inferior vena cava (IVC). Although right-sided electrophysiology procedures have been performed successfully in patients with a previously placed IVC filter by direct placement of catheters through the filter, an alternative approach is necessary in some patients. METHODS: This case series describes three patients with an IVC filter who underwent successful ablation of the slow pathway for typical atrioventricular (AV) nodal reentrant tachycardia using a superior vena cava (SVC) approach via the right internal jugular (IJ) vein. Two separate introducer sheaths were placed into the IJ vein using separate punctures. This permitted placement of a standard deflectable ablation catheter and an additional catheter in the right atrium to monitor for ventriculoatrial conduction during the junctional rhythm associated with ablation of the slow AV nodal pathway. RESULTS: Catheter ablation was successful in each patient. The number of radiofrequency current applications was 7, 17, and 27. There were no procedural complications and no patient had recurrent tachycardia during follow-up. CONCLUSIONS: Catheter ablation of the slow AV nodal pathway can be performed successfully and safely in patients with inferior venous barriers to the right heart using an SVC approach via the right IJ vein.     

Narrow Complex Tachycardia with VA Block: Diagnostic and Therapeutic Implications

To review our experience with cases of narrow complex tachycardia with VA block, highlighting the difficulties in the differential diagnosis, and the therapeutic implications. Prior reports of patients with narrow complex tachycardia with VA block consist of isolated case reports. The differential diagnosis of this disorder includes: automatic junctional tachycardia, AV nodal reentry with final upper common pathway block, concealed nodofascicular (ventricular) pathway, and intra-Hissian reentry. Between June 1994 and January 1996, six patients with narrow complex tachycardia with episodes of ventriculoatrial block were referred for evaluation. All six patients underwent attempted radiofrequency ablation of the putative arrhythmic site. Three of six patients had evidence suggestive of a nodofascicular tract. Intermittent antegrade conduction over a left-sided nodofascicular tract was present in two patients and the diagnosis of a concealed nodofascicular was made in the third patient after ruling out other tachycardia mechanisms. Two patients had automatic junctional tachycardia, and one patient had atroventricular nodal reentry with proximal common pathway block. Attempted ablation in the posterior and mid-septum was unsuccessful in patients with nodofascicular tachycardia. In contrast, those with atrioventricular nodal reentry and automatic junctional tachycardia readily responded to ablation. The presence of a nodofascicular tachycardia should be suspected if: (1) intermittent antegrade preexcitation is recorded, (2) the tachycardia can be initiated with a single atrial premature producing two ventricular complexes, and (3) a single ventricular extrastimulus initiates SVT without a retrograde His deflection. The presence of a nodofascicular pathway is common in patients with narrow complex tachycardia and VA block. Unlike AV nodal reentry and automatic junctional tachycardia, the response to ablation is poor.     

Failure of right atrial premature beats to reset atriofascicular tachycardia

A patient with a right atriofascicular (Mahaim) tachycardia was found to have inducible antidromic supraventricular tachycardia, but atrial premature beats from the right atrial free wall failed to reset the tachycardia. An interesting transition from AV nodal reentry tachycardia to Mahaim tachycardia is also presented.     

Atrioventricular Nodal Reentry: Evidence Supporting an Intranodal Location

The exact site of the reentrant circuit in AV nodal reentry remains controversial. While recent ablative techniques have yielded information, the interpretation of which suggests that the atrium is required, other explanations for these interpretations are available. Prior pathophysiological studies with three-dimensional reconstruction of the node suggest that it is a highly anisotropic structure and extends through Koch's Triangle. Data from humans suggesting the atria are not necessary include the presence of AV dissociation during supraventricular tachycardia (SVT), depolarization of atrial tissue surrounding the node without affecting SVT, pacing induced AH intervals exceeding those during SVT, and site dependency ofa critical AH interval (exceeding afrial refractoriness) that is required for initiation of AV nodal reentry.     

Atrioventricular Dissociation During Paroxysmal Junctional Tachycardia

We describe the rare occurrence of atrioventriculor dissociation in three patients during paroxysmal functional tachycardia. The mechanism of tachycardia was atrioventricular nodal reentry in two patients. The third patient had reentrant tachycardia that utilized the A V node for at least part of the reentrant circuit. This patient also had a nodoventricular pathway that may have participated in the reentrant circuit. In two patients, ventricular tachycardia was diagnosed prior to electrophysiologic assessment and medication to prevent tachycardia was not successful. After electrophysiological studies, treatment directed at suppressing AV nodel reentry prevented recurrent tachycardia. These case studies demonstrate the importance of detailed electrophysiological assessment of tachycardia in patients whose arrhythmia does not respond to empirical antiarrhythmic therapy. (PACE, Vol. 4, November-December, 1981)     

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 siow conducting pathway and retrograde conduction using a fast conducting path way. 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.     

Symptomatic Sinus Tachycardia with Perpetuating Slow Pathway: Successful Treatment with Radiofrequency Ablation

We report a case of sinus tachycardia with perpetuating slow pathway (SP) conduction in a 42‐year‐old woman who developed severe symptoms as a result of atrioventricular (AV) desynchronization. The restoration of an AV synchrony, achieved with selective radiofrequency ablation of the SP, eliminated the symptomatic arrhythmia and may represent a reasonable therapeutic option despite the fact that the patient has no AV‐node reentrant tachycardia. This case demonstrates the importance of AV timing.     

Acute effects of simvastatin to terminate fast reentrant tachycardia through increasing wavelength of atrioventricular nodal reentrant tachycardia circuit

Simvastatin (SV) leads to reduction of ventricular rhythm during atrial fibrillation on rabbit atrioventricular (AV) nodes. The aim of our study was (i) to determine the frequency‐dependent effects of SV in a functional model, and (ii) to assess the effects of SV to suppress experimental AV nodal reentrant tachycardia (AVNRT). Selective stimulation protocols were used with two different pacing protocols, His to atrial, and atrial to atrial (AA). An experimental AVNRT model with various cycle lengths was created in three groups of perfused rabbit AV nodal preparations (n = 24) including: SV 3 μm , SV 7 μm , and verapamil 0.1 μm . SV increased nodal conduction time and refractoriness by AA pacing. Different simulated models of slow/fast and fast/slow reentry were induced. SV caused inhibitory effects on the slow anterograde conduction (origin of refractoriness) more than on the fast anterograde conduction time, leading to an increase of tachycardia cycle length, tachycardia wavelength and termination of slow/fast reentrant tachyarrhythmia. Verapamil significantly suppressed the basic and frequency‐dependent intrinsic nodal properties. In addition, SV decreased the incidence of gap and echo beats. The present study showed that SV in a concentration and rate‐dependent manner increased the AV effective refractory period and reentrant tachycardia wavelength that lead to slowing or termination of experimental fast AVNRT. The direction‐dependent inhibitory effect of SV on the anterograde and retrograde dual pathways explains its specific antireentrant actions.     

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 < 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.     

Discordant Effects of Carotid Sinus Massage and Intravenous Adenosine in Atypical (Fast-Slow) Atrioventricular Nodal Reentrant Tachycardia

The precise mechanism underlying supraventricular tachycardia with a long R-P interval is often difficult to assess noninvasively. Carotid sinus massage has been used traditionally to produce transient AV nodal conduction delay at the bedside, and may be of diagnostic or therapeutic benefit. More recently, adenosine has also been shown to be useful in this situation. We report the case of a patient with an incessant long R-P tachycardia in whom the response to CSM was misleading while the response to adenosine was diagnostic. The electrophysiologic responses to both maneuvers are displayed, and a mechanism for the discordant responses is proposed.     

Age Related Changes in Dual AV Nodal Physiology

Dual atrioventricular nodal (DAVN) physiology has been reported in up to 63% of pediatric patients with anatomically normal hearts, yet atrioventricular nodal reentrant tachycardia (AVNRT) accounts for only 13%–16% of supraventicular tachycardia (SVT) in childhood. The incidence of AVNRT increases with age and becomes the most common form of SVT by adolescence. We investigated the age related electrophysiological responses to programmed atrial and ventricular stimulation in 14 pediatric patients who underwent intracardiac electro-physiological study prior to radiofrequency catheter ablation for AVNRT and who exhibited DAVN physiology. Single atrial and ventricular extrastimuli were placed following drive trains with cycle lengths of 400–700 ms and 350–500 ms, respectively. Six children (mean age 8.2 years, range 5.2–11.5 years) were compared to eight adolescents (mean age 16.6 years, range 13.3–20.7 years). Adolescents were found to have a significantly longer fast pathway effective refractory period (ERP) (median 375 vs 270 ms, P = 0.03), slow pathway ERP (median 270 vs 218 ms, P = 0.04), atrio-Hisian (AH) during AVNRT (median 300 vs 225 ms, P = 0.007), and AVNRT cycle length (median 350 vs 290ms, P = 0.03). There was a strong trend for the AH measured at the fast pathway ERP to be longer in adolescents than in children (median 258 vs 198 ms, P = 0.055). The AH at the fast pathway ERP was more strongly correlated with baseline cycle length than with age (r = 0.7, P = 0.01 vs r = 0.5, P = 0.7). There was no significant difference in the retrograde VA conduction between adolescents and children. These results demonstrate an age related difference in AV nodal response to programmed atrial stimuli in pediatric patients with DAVN physiology and AVNRT. These differences are consistent with mechanisms that may explain the increased incidence of AVNRT in adolescents compared to children.     

Treatment of left-sided extension of AV node: A valuable integration of advance imaging modalities and cryoablation

We present a case of successful cryoablation of the left extension of the atrioventricular (AV) node for treatment of a recurrent atrioventricular nodal reentry tachycardia without the use of fluoroscopy. Three-dimensional electroanatomic mapping system and intracardiac echocardiography were used to navigate catheters in the heart and position them according to anatomical landmarks. Due to the nature of cryoablation lesion formation, lesions were able to be applied safely in right atrium, as well as in left atrium, without damaging AV node or bundle of His.