Atrioventricular Nodal Reentrant Research Articles

Novel method to avoid serious injurious effects on the atrioventricular nodal (AVN) conduction during catheter ablation of the AVN slow pathway utilizing cryofreezing energy

BackgroundSlow pathway elimination of the atrioventricular node (AVN) is essential to treat AVN reentrant tachycardia (AVNRT). However, injury to the AVN conduction (IAVN) is one of the serious complications. Cryofreezing energy is expected to reduce the incidence of IAVN. This study aimed to investigate the usefulness of a novel method to avoid IAVN during cryoablation of AVNRT. MethodsA total of 157 patients (average age, 65.8 years; male, 71) suffering from AVNRT were included. Once the AVNRT terminated during cryo-ablation, then rapid atrial constant pacing (RACP) was performed during freezing at a rate lower 10 bpm than that inducing Wenchebach AV block in 74 (47.1 %) patients (Group A). The RACP rate was decreasingly reduced by 10 bpm in case of the occurrence of IAVN. When the RACP reached 100 bpm, the cryoablation was prematurely terminated. Group B patients (83 = 52.9 %) underwent cryoablation during sinus rhythm. All patients were allocated in a randomized fashion. We compared the severity of the IAVN between Groups A and B. ResultsThere were no significant differences at 12 months regarding the freedom from the AVNRT between Groups A and B. However, the duration of the IAVN was significantly longer in Group B than A (p = 0.02). There were no significant differences regarding the distance between the His recording sites and successful ablation sites between Groups A and B. No permanent IAVN requiring pacemaker implantation was provoked in either group. ConclusionRACP was useful to avoid sustained and serious IAVN during cryoablation of AVNRT.

Utility of the aVL Lead in the Electrocardiographic Diagnosis of Atrioventricular Nodal Re-Entrant Tachycardia

Background: Reciprocating atrioventricular tachycardia can be categorized into common slow–fast atrioventricular node re-entrant (AVNRT) and orthodromic atrioventricular reciprocating tachycardia (AVRT). The electrocardiogram (ECG) during tachycardia is useful in distinguishing these two mechanisms. The presence of a pseudo- R0-wave in lead V1 or pseudo-S-wave in the inferior leads has been widely used, although the value of an isolated aVL lead has not been evaluated yet. To determine whether an isolated aVL lead of the surface 12-lead ECG is useful for the differential diagnosis between AVNRT and AVRT. Methods: This cross sectional observational study was conducted at the department of Cardiology, National Institute of Cardiovascular Diseases & Hospital, for 1-year period. Patient admitted in NICVD due to supraventricular tachycardia and was screened as a case of AVNRT & AVRT were approached for inclusion of the study. After initial management all patients were subjected to perform electrophysiological study and radiofrequency ablation. The specific pattern of changes in aVL lead were recorded in each cases and were analyze to determine the sensitivity, specificity and positive predictive values to estimate AVRT & AVNRT. Informed written consent was taken from the subject and ethical issues were ensured. Total 60 patients were included for final analysis. Data analysis was done by statistical program Statistical Package for Social Science (SPSS) version 20.0. Results: Among the 60 study population, mean age was 41.28±11.21 SD (years) [age range: 18-65 years]. Total 44 patients (73%) had AVNRT and 16 patients (27%) had found AVRT in Electrophysiological evaluation. About 61.7% patients were female and 38.3% patients were male in this study with no significant gender difference in between AVNRT and AVRT group (p>0.05). Total 43.3% patients had aVL notch on ECG. Among patients who had AVNRT, 54.5% had aVL notch and among patients who had AVRT, 12.5% had aVL .........

Antiarrhythmic Medication in Neonates and Infants with Supraventricular Tachycardia

Supraventricular tachycardia (SVT) is the most common arrhythmia in neonates and infants, and pharmacological therapy is recommended to prevent recurrent episodes. This retrospective study aims to describe and analyze the practice patterns, effectiveness, and outcome of drug therapy for SVT in patients within the first year of life. Among the 67 patients analyzed, 48 presented with atrioventricular re-entrant tachycardia, 18 with focal atrial, and one with atrioventricular nodal re-entrant. Fetal tachycardia was reported in 27%. Antiarrhythmic treatment consisted of beta-receptor blocking agents in 42 patients, propafenone in 20, amiodarone in 20, and digoxin in 5. Arrhythmia control was achieved with single drug therapy in 70% of the patients, 21% needed dual therapy, and 6% triple. Propafenone was discontinued in 7 infants due to widening of the QRS complex. After 12 months (6–60), 75% of surviving patients were tachycardia-free and discontinued prophylactic treatment. Patients with fetal tachycardia had a significantly higher risk of persistent tachycardia (p: 0.007). Prophylactic antiarrhythmic medication for SVT in infancy is safe and well tolerated. Arrhythmia control is often achieved with single medication, and after cessation, most patients are free of arrhythmias. Infants with SVT and a history of fetal tachycardia are more prone to suffer from persistent SVT and relapses after cessation of prophylactic antiarrhythmic medication than infants with the first episode of SVT after birth.

Fast-slow atrioventricular nodal reentrant tachycardia phenotype mimicking the slow-slow type

Abstract Background Fast-slow (F/S-) atrioventricular (AV) nodal reentrant tachycardia (AVNRT) is characterized by a short atrio-His (AH) interval and the earliest site of atrial activation (EAA) in the proximal coronary sinus (EAA-CS), while slow-slow (S/S-) AVNRT presents a long AH interval and EAA-CS. Those intracardiac appearances are initial indicators for making a diagnosis. Purpose To identify an unknown phenotype of F/S-AVNRT. Methods Among 46 consecutive patients with F/S-AVNRT, 6 patients (1 man, age 59±9) had an apparent but not typical (pseudo-) S/S-AVNRT during an electrophysiologic study. In 2 patients, pseudo-S/S-AVNRT was clinically documented. Results In all 6 patients, the diagnosis of F/S-AVNRT was made by an exclusion of atrial tachycardia with findings of 1) a V-A-V response following ventricular entrainment or 2) termination without atrial capture by ventricular pacing, and an exclusion of AV reentrant tachycardia with a ventriculoatrial dissociation during an initial (so-called QRS transition) zone of ventricular entrainment. An initial A-A-V activation sequence on atrial induction of F/S-AVNRT observed in 1 patient and Wenckebach-type AV block during ongoing F/S-AVNRT developing in 3 patients suggested the presence of the lower common pathway (LCP). Like the typical S/S-AVNRT, pseudo-S/S-AVNRT was induced with atrial stimulation after a jump in the AH interval or double ventricular response. However, in all patients, the pseudo-S/S-AVNRT transited to F/S-AVNRT following AV block in a single cycle and/or pseudo-S/S-AVNRT transited from spontaneously or triggered by atrial contractions. Importantly, on these transitions, the atrial cycle length (CL) and EAA-CS remained unchanged, that is, the atrial CL of S/S-AVNRT was almost identical to that of F/S-AVNRT, suggesting that the essential circuit of both tachycardias was identical. Actually, both tachycardias were cured by ablation at a single site in the traditional slow pathway (SP). Collectively, the pseudo-S/S-AVNRT was diagnosed as another phenotype of F/S-AVNRT accompanied by sustained antegrade conduction via another bystander (likely the left-sided or superior) SP breaking through the His bundle owing to the repetitive antegrade block at the LCP occurring by linking phenomenon, thus representing a long AH interval during the ongoing F/S-AVNRT. When the antegrade conduction is blocked at the bystander SP during the pseudo-S/S-AVNRT, releasing the linking phenomenon, the subsequent antegrade conduction reach the His-bundle via the fast pathway, thus returning to F/S-AVNRT. Conclusions An unknown, but not rare F/S-AVNRT phenotype exists that apparently mimics the typical S/S-AVNRT and is also an unknown subtype of apparent S/S-AVNRT. The presence of this pseudo-S/S-AVNRT suggests the limitation of classifying types of AVNRT based on AH and HA intervals during tachycardia. Understandings of this phenotype can advance a diagnosis of atypical AVNRT with multiple phenotypes. Funding Acknowledgement Type of funding sources: None.

Atrioventricular Nodal Reentrant Tachycardia in Very Elderly Patients: A Single-center Experience.

We present a series of elderly patients older than 80 years who had recurrent palpitations for decades and who were subsequently diagnosed with atrioventricular (AV) nodal reentrant tachycardia (AVNRT). Through a retrospective chart analysis, we identified 12 patients (nine females and three males) aged 88 years ± 3.7 years (range: 80–92 years) seen at our center from 2015 to 2016 for recurrent palpitations and supraventricular tachycardia (SVT) who were ultimately diagnosed with AVNRT. These patients had palpitations and had been treated for anxiety and panic attacks for decades. They underwent electrophysiology (EP) study and successful ablation of the slow pathway. The demographic data, symptoms, and EP characteristics during the EP studies of the patients were evaluated. All 12 patients experienced palpitations and all but three had documented SVT on a loop recorder or an event monitor. During EP study, all patients displayed slow-pathway conduction. Nine patients demonstrated discontinuous AV nodal conduction curves, while three showed continuous AV nodal conduction curves. The observed tachycardia rates were 496.7 ms ± 25.7 ms. Three patients had atrial fibrillation (AF), which was noted during monitoring with the implanted loop recorders. Tachycardia was induced with both burst atrial pacing and atrial extrastimuli in five patients and with extrastimuli only in two patients. In five patients, no tachycardia induction was noted, but these individuals showed evidence of dual AV node physiology. Successful elimination of residual slow-pathway conduction postablation and/or noninducibility of tachycardia in the postablation period were achieved in all patients. All patients remained symptom-free over a period of one year. The patients who had AF in addition to AVNRT also did not present any recurrent AF following AVNRT ablation but are being monitored for recurrence. AVNRT in elderly people is often confused with panic attacks; hence, reports of panic attacks in elderly people should be properly evaluated for an arrhythmic etiology.

Atrioventricular nodal echoes over a wide echo window as a therapeutic end point for the catheter-guided radiofrequency ablation of atrioventricular nodal reentrant tachycardia: a prospective study.

In previous retrospective studies, it was shown that the presence of residual single atrioventricular node (AVN) echoes with an echo zone longer than 30 ms may increase the rate of recurrence after radiofrequency ablation (RFA) of slow pathway in patients with AVN reentrant tachycardia (AVNRT). Based on that, some centres perform additional RFA in these patients. However, this opinion has never been tested prospectively and many centres do not perform re-ablation in these patients. The purpose of this study was to test whether persistence of a single AVN echo over a wide echo zone is a valid end point for RFA. In this prospective study, 576 patients who had a non-inducible arrhythmia post-RFA of AVNRT were divided into those with a remnant echo over a wide echo zone (case group) and those reaching classical end points (control group). The primary end point of the study was recurrence and patients were followed for 34.5 ± 18.8 months. In the control group (n = 510), 14 patients (2.7%) had a recurrence while no recurrence was seen in the case group (n = 66) (final cure rate, 97.3 vs. 100%; difference, 2.7%; upper bound of the 98% CI, 0.0488; P < 0.0001 for non-inferiority). Two complete heart blocks (0.4%) happened in the control group and none in the case group (P = 0.784). Non-inducibility in the presence of a wide echo window is non-inferior to non-inducibility in the presence of narrow echo window or no AVN echoes. In general, the presence of a single echo beat is not an indication for further ablation and this applies for both narrow and wide windows.

The effect of atrial pacing site on electrophysiological properties of the atrioventricular junction and induction of atrioventricular nodal reentry in patients with typical atrioventricular nodal reentrant tachycardia.

Clinical studies in humans have shown the site of atrial stimulation to influence atrioventricular (AV) conduction times and refractory periods, the demonstration of dual AV nodal (AVN) pathways, and induction of AVN reentry. These studies often found conflicting results. Moreover, among enrolled patients a minority of them were found to have AVN reentrant tachycardia (AVNRT). The purpose of this study was to investigate the effect of right and left atrial pacing on the electrophysiological properties of the AV junction in the typical AVNRT population. Ninety-two consecutive patients with typical AVNRT were included. Atrial pacing was performed from the high right atrium (HRA) and the left atrium via the proximal coronary sinus (CS). Stimulation from either the HRA or the CS could result in dual AVN physiology and AVNRT. No site-dependent differences in the ease of induction of dual AVN pathways with variability of initiation from either site were found. However, AVNRT was easier to induce from the HRA. With CS pacing the leftward but not the rightward AVN approaches were the entry point to the AV node because of significantly shorter AH conduction times compared to HRA pacing. Conduction over the leftward AVN extensions could initiate the tachycardia with significantly shorter critical AH interval compared to conduction over the rightward AVN extensions; however, the AH interval during AVNRT and its cycle length were not significantly different. Rightward and leftward AVN extensions are regular features of the AV node. Their different electrophysiological properties lead to variation in the demonstration of discontinuous AVN conduction and AVNRT during right and left atrial pacing. Despite the observation that the left AVN extensions could compose the entry point to the reentrant circuit, there is no evidence that they constitute the critical component of sustained typical AVNRT.

Differential diagnosis of a narrow QRS tachycardia

The differential diagnosis of a narrow QRS tachycardia requires on the one hand knowledge about the clinical data of the tachycardia patient but on the other hand a systematic step by step analysis of the electrocardiogram (ECG) is the most successful approach. Apart from the question of regularity or irregularity of the QRS complexes, the presence and detection of P waves is also of importance. The P wave timing in relation to the preceding and the following QRS complexes as well as the numerical relationship of P waves and QRS complexes allow a well-founded suspected diagnosis to be achieved in most cases. Even the differentiation between atrioventricular (AV) nodal reentrant tachycardia (AVNRT) versus orthodromic AV reentrant tachycardia (AVRT), e.g. by accessory leads, is in most cases possible in a surface ECG. Obviously, there are constellations which need an invasive electrophysiological procedure for a definitive diagnosis.

Differentiation between atrioventricular reentrant tachycardia (AVRT) and AV nodal reentrant tachycardia (AVNRT)

Differentiation between atrioventricular reentrant tachycardia (AVRT) and AV nodal reentrant tachycardia (AVNRT) can be sometimes challenging in the EP lab. RV pacing during SVT produces progressive QRS fusion before QRS morphology becomes stable. This fusion zone (FZ) may differentiate AVRT from AVNRT independent of entrainment success. PPI-TCL during RV entrainment can help in differentiation; however it has some fallacies and limitations. We thought to compare the accuracy of atrial preexcitation (AP) & Stimulus to atrial (S-A) interval fixation in relation to fusion zone in identifying the mechanism of SVT. We studied retrospectively and prospectively the effect of properly timed RVP on atrial timing during FZ. 118 SVT patients had RVP within 40 ms shorter than tachycardia cycle length (TCL). S–A interval and atrial CL were measured during FZ and with each QRS complex thereafter. A fixed S–A interval was defined as variation 9 patients were excluded due to cycle length oscillation > 10 ms before the onset of RVP and 6 patients had atrial tachycardia (VA dissociation with RVP) and were excluded. In the remaining 103 patients, PPI-TCL was significantly longer in AVNRT patients but postpacing response couldn’t be assessed in 12 patients who showed consistent termination of tachycardia during RVP entrainments; 3 AVNRT patients (5%) & 9 AVRT patients (22%). And when assessed it was not diagnostic in additional 4 (6%) patients with AVNRT ( We can conclude that during RVP within 40 ms of the tachycardia cycle length, fixed S–A interval and AP in relation to FZ were superior to PPI-TCL measurement in identifying the mechanism of SVT.

A case of typical atrioventricular nodal (AVN) reentrant tachycardia confined to the compact AV node, showing a variety of rare electrophysiological findings, including eccentric AVN echoes

Herein, we report the case of a 49-year-old woman with typical atrioventricular nodal (AVN) reentrant tachycardia, confined to the compact atrioventricular node, showing numerous rare electrophysiological findings such as unique AVN reentrant echoes, double ventricular responses, latent retrograde dual AVN pathways, antegrade triple AVN pathways, and longitudinal dissociation within the lower final common pathway.

Arritmias supraventriculares paroxísticas

Paroxysmal supraventricular tachycardias are fast and usually regular rhythms that require some structures above the bifurcation of the His bundle to be continued, and often are caused by reentrant circuit. The 3 most common types are: atrioventricular nodal reentrant, tachycardias mediated by an accessory pathway and atrial tachycardias. They are characterized by a considerable heterogeneity of clinical presentations (ranging from almost asymptomatic forms to those producing a certain disability). They usually occur in people without structural heart disease, and their prognosis is generally benign. Differential diagnosis with other regular tachycardia with a narrow QRS complex is to be made, and electrophysiological study is sometimes necessary for an accurate diagnosis. The treatment of choice for symptomatic patients is generally catheter ablation.

Is atrioventricular nodal reentrant tachycardia possible in patients with first degree AV block?

Purpose of the study: Typical Atrioventricular (AV) Node Re-entrant Tachycardia (AVNRT) occurs in patients with dual AV nodal pathway, a rapid pathway used for retrograde conduction and a slow pathway used for the anterograde conduction. In sinus rhythm the patients have generally the signs of conduction through the rapid pathway with a normal or short PR interval. The purpose of the study was to evaluate the prevalence of patients with 1st degree AV block and with AVNRT and their clinical characteristics. Methods: 1040 patients, 366 males, 665 females were admitted for typical AVNRT. They were aged from 6 to 90 years (mean age 50±19). Initial ECG and clinical data were collected. Electrophysiological study was systematic. Results: Spontaneous 1st degree AV Block (AVB) was rare and noted in 8 patients. The prevalence of the association 1st degree AV Block and AVNRT was 0.8%. AVB was suprahisian in 7 of 8 and infrahisian in one of them. Five patients complained of AVNRT at exercise. Two patients had an ischemic heart disease. Patients with AVB were significantly older (71.5±16 years) than patients without AVB (50±19) (p<0.002). AVNRT was induced in control state in 5 patients. The rate of tachycardia was slow between 130 and 160 bpm. AVNRT was induced after isoproterenol in 3 patients and the rate was higher (180 to 200 bpm). Ablation of slow pathway was performed in 7 patients. Transitory 2nd degree AVB was noted in 1 patient. AVNRT was not inducible after ablation. PR interval remained unchanged. At atrial pacing, the rate of 2nd degree AVB occurrence decreased, due to the disappearance of the conduction through the slow pathway. Two patients developed transitory well-tolerated 2nd degree AVB one day after ablation. One patient presented apparent sinus bradycardia related to a concealed conduction through AV node. One year after ablation none of the patients required pacemaker implantation and patients were free of tachycardia. Conclusions: The occurrence of AVNRT in patients with 1st degree AV block is exceptional and concerns old patients. The prevalence was 0.8%. Ablation of slow pathway might be safely performed without a need of pacemaker implantation. Transitory 2nd degree AVB can be noted the day after ablation.

National Registry on Cardiac Electrophysiology (2010 and 2011)

Based on a survey sent to Portuguese centers that perform diagnostic and interventional electrophysiology and/or implant cardioverter-defibrillators (ICDs), the authors analyze the number and type of procedures performed during 2010 and 2011 and compare these data with previous years.In 2011, a total of 2533 diagnostic electrophysiologic procedures were performed, which were followed by ablation in 2013 cases, a steady increase over previous years. The largest share of this increase compared to 2010 was in atrial fibrillation, which is now the second most frequent indication for ablation, after atrioventricular nodal reentrant tachycardia.The total number of ICDs implanted in 2011 was 1084, of which 339 were biventricular (BiV) cardiac resynchronization devices (BiV ICDs). This represents an increase in the total number relative to previous years, 2011 being the first year in which the rate of new ICD implantations in Portugal exceeded 100 per million population. However, compared to 2010, the number of BiV ICDs implanted decreased, despite the recent publication of updated European guidelines on device therapy in heart failure, which clarified and expanded the indications for implantation of these devices.Some comments are made on the current status of cardiac electrophysiology in Portugal and on factors that may influence its development in the coming years.

Registo Nacional de Eletrofisiologia Cardíaca (2010 e 2011)

Based on a survey sent to Portuguese centers that perform diagnostic and interventional electrophysiology and/or implant cardioverter-defibrillators (ICDs), the authors analyze the number and type of procedures performed during 2010 and 2011 and compare these data with previous years.In 2011, a total of 2533 diagnostic electrophysiologic procedures were performed, which were followed by ablation in 2013 cases, a steady increase over previous years. The largest share of this increase compared to 2010 was in atrial fibrillation, which is now the second most frequent indication for ablation, after atrioventricular nodal reentrant tachycardia.The total number of ICDs implanted in 2011 was 1084, of which 339 were biventricular (BiV) cardiac resynchronization devices (BiV ICDs). This represents an increase in the total number relative to previous years, 2011 being the first year in which the rate of new ICD implantations in Portugal exceeded 100 per million population. However, compared to 2010, the number of BiV ICDs implanted decreased, despite the recent publication of updated European guidelines on device therapy in heart failure, which clarified and expanded the indications for implantation of these devices.Some comments are made on the current status of cardiac electrophysiology in Portugal and on factors that may influence its development in the coming years.

The study of the relation between different end points of slow atrioventricular nodal pathway ablation and clinical efficiency in patients with atrioventricular nodal reentrant tachycardia (slow-fast kind)

ObjectiveThe study of the Relation between different end points of slow atrioventricular nodal pathway ablation and clinical efficiency in patients with atrioventricular nodal reentrant tachycardia.Methods350 patients with atrioventricular nodal re-entrant...

The Use of Transtelephonic Loop Recorders for the Assessment of Symptoms and Arrhythmia Recurrence After Radiofrequency Catheter Ablation

Radiofrequency catheter ablation (RFA) is an effective treatment of arrhythmias. However, patients often remain symptomatic after the procedure. We aimed to assess the arrhythmia recurrence after successful RFA in relation to patients' symptoms using transtelephonic loop recorders. Thirty-six consecutive patients (age 50 +/- 14 years, 17 males/19 females) were enrolled after successful RFA for atrioventricular (AV) nodal reentrant tachycardia (n = 21), AV reentrant tachycardia (n = 8), atrial tachycardia (n = 2), atrial fibrillation/flutter (n = 4), and ventricular tachycardia (n = 1). During 23 +/- 6 days of follow-up, 679 events were recorded, 246 of which were true arrhythmic events, mostly (56%) asymptomatic. The vast majority of these true arrhythmic events were due to trivial arrhythmias (extrasystoles or sinus tachycardia), equally distributed among symptomatic and asymptomatic episodes. Arrhythmia relapse was shown in four patients, who had a total of nine episodes, eight of which were symptomatic. No high degree AV block was detected. Overall, symptom recurrence had low sensitivity (44%) and high specificity (95%) for the detection of any arrhythmia, and high sensitivity (89%) but low specificity (58%) for the detection of relapse. In conclusion, transtelephonic monitoring was a useful tool for the assessment of symptoms after RFA and its use may be reserved for the most symptomatic patients to detect a relapse or to reassure them for the benign nature of their symptoms.

Transesophageal Electrophysiologic Study to Determine the Inducibility After Successful Ablation of Supraventricular Tachycardia in Children

Radiofrequency ablation has become first-line therapy for supraventricular tachycardia in all age groups, but there has been a concern regarding the long-term effectiveness of the procedure in children. This study aimed to determine the inducibility after successful ablation of supraventricular tachycardia in children; assessment was performed using a transesophageal electrophysiologic study. A total of 63 patients who had been treated successfully for supraventricular tachycardia with radiofrequency ablation were included in the study. A transesophageal electrophysiologic study was performed 2 months after radiofrequency ablation. Tachycardia was induced in nine of 34 symptomatic and five of 29 asymptomatic patients by a transesophageal electrophysiologic study. Ten patients had recurrence of the same type of supraventricular tachycardia seen previously, and two had a new type of arrhythmia during a transesophageal electrophysiologic study. Tachycardia inducibility rate was 16% in all patients, 22.8% in patients with atrioventricular reentrant tachycardia, and 8% in patients with atrioventricular nodal reentrant tachycardia. Radiofrequency ablation is a safe and effective method to manage children with supraventricular tachycardia, but patients must be observed for recurrence and new arrhythmias. Sustained tachycardia may also be induced in asymptomatic patients. A transesophageal electrophysiologic study is effective and safe for follow-up of radiofrequency ablation for assessment, diagnosis, and treatment of patients.

Potential-guided versus anatomic-guided approach for slow pathway ablation of the common type atrioventricular nodal reentry tachycardia: a randomized study

Objective — The present study aimed to compare the effectiveness and safety of the potential-and the anatomic-guided approach for slow pathway ablation in patients with recurrent episodes of symptomatic common type atrioventricular (AV) nodal reentrant tachycardia.Methods — Two hundred and twenty-eight patients were randomly assigned to undergo either a potential- (n = 114,47% men, mean age 52.85 ± 14.04 years) or an anatomic-guided approach (n = 114, 50% men, mean age 52.45 ± 14.46 years) for radiofrequency ablation of the slow pathway.The mean duration of the follow-up period was 26.7 ± 7.9 and 24.8 ± 7.6 months in the potential- and anatomic-guided approach, respectively (P > 0.05).Results — The success rate for slow pathway ablation was 100% in both ablative methods.The mean duration of atrial electrograms at the successful ablation sites of the potential- and the anatomic-guided approaches was 69 ± 14 msec and 57 ± 10 msec, respectively (P = 0.001).There were no significant differences between the potential- and the anatomic-guided approach regarding the duration of the procedure (121.13 ± 56.83 vs. 109.93 ± 57.12 min, P = 0.139), the duration of fluoroscopic exposure (6.12 ± 3.32 vs. 6.64 ± 3.33 min, P = 0.239) or the mean number of radiofrequency applications delivered (3.96 ± 2.77 vs. 4.33 ± 2.73, P = 0.311). Residual dual AV nodal pathway following successful ablation was observed in 9.6% of patients who underwent the potential-guided approach and in 23.7% of patients who underwent the anatomic method (P = 0.004). During follow-up, arrhythmia recurrence was observed in four patients (1.8%), two in each group (P > 0.05).Conclusions — The efficacy and safety of the slow pathway ablation is very high using either the potential- or the anatomic-guided approach.

Utilization of Retrograde Right Bundle Branch Block to Differentiate Atrioventricular Nodal from Accessory Pathway Conduction

Defining whether retrograde ventriculoatrial (V-A) conduction is via the AV node (AVN) or an accessory pathway (AP) is important during ablation procedures for supraventricular tachycardia (SVT). With the introduction of ventricular extrastimuli (VEST), retrograde right bundle branch block (RBBB) may occur, prolonging the V-H interval, but only when AV node conduction is present. We hypothesized that when AP conduction was present, the V-A interval would increase less than the V-H interval, whereas with retrograde nodal conduction, the V-A interval would increase at least as much as the V-H interval. We retrospectively reviewed the electrophysiological studies of patients undergoing ablation for AVN reentrant tachycardia (AVNRT) (55) or AVRT (50), for induction of retrograde RBBB during the introduction of VEST, and the change in the measured V-H and V-A intervals. Results were found to be reproducible between independent observers. Out of 105 patients, 84 had evidence of induced retrograde RBBB. The average V-H interval increase with induction of RBBB was 53.7 ms for patients with AVRT and 54.4 ms for patients with AVNRT (P = NS). The average V-A interval increase with induction of RBBB was 13.6 ms with AVRT and 70.1 ms with AVNRT (P < 0.001). All patients with a greater V-H than V-A interval change had AVRT, and those with a smaller had AVNRT. Induction of retrograde RBBB during VEST is common during an electrophysiological study for SVT. The relative change in the intervals during induction of RBBB accurately differentiates between retrograde AVN and AP conduction.

Utility of the aVL lead in the electrocardiographic diagnosis of atrioventricular node re-entrant tachycardia

Reciprocating atrioventricular tachycardia can be categorized into common slow-fast atrioventricular node re-entrant (AVNRT) and orthodromic atrioventricular reciprocating tachycardia (AVRT). The electrocardiogram (ECG) during tachycardia is useful in distinguishing these two mechanisms. The presence of a pseudo-R'-wave in lead V1 or pseudo-S-wave in the inferior leads has been widely used, although the value of an isolated aVL lead has not been evaluated yet. To determine whether an isolated aVL lead of the surface 12-lead ECG is useful for the differential diagnosis between AVNRT and AVRT. Consecutive patients referred for paroxysmal regular supraventricular tachycardia radiofrequency ablation were prospectively evaluated. Patients with atrial tachycardia, bundle branch block, manifested pre-excitation, and those undiagnosed after electrophysiology study were excluded. We compared the standard criteria with the value of an isolated aVL lead to distinguish between AVNRT and AVRT. One hundred and one patients were included; 73.3% were AVNRT and 26.7% AVRT. Patients with AVNRT were older (49.4 +/- 16.4 vs. 36.0 +/- 18.7 years, P = 0.001). The aVL notch and the standard criteria were found more frequently in AVNRT than in AVRT (aVL notch: 51.3 vs. 7.4%, P< or = 0.001; pseudo-S-wave 45 vs. 8.6% P = 0.001; and pseudo-R'-wave in V1 39.7 vs. 11.5%, P = 0.008, respectively). The aVL notch sensitivity and specificity to determine the final diagnosis were higher than the standard criteria (aVL notch 48.6 and 92.6%; pseudo-S-wave 45 and 91.3%; and pseudo-R'-wave in V1 39.7 and 88.5%, respectively). The presence of a notch in aVL lead appeared to be as sensitive and specific as the standard electrocardiographic criteria for the differential diagnosis of AVNRT.