Simplified "ATP test" for noninvasive diagnosis of dual AV nodal physiology and assessment of results of slow pathway ablation in patients with AV nodal reentrant tachycardia

INTRODUCTION: We recently reported that administration of adenosine triphosphate (ATP) during sinus rhythm identifies dual AV nodal physiology (DAVNP) in 76% of patients with inducible sustained AV nodal reentrant tachycardia (AVNRT) at electrophysiologic (EP) study. In that report, however, the ATP test was considered positive for DAVNP only when the results were reproducible at a given dose of ATP. The aim of the present study was to assess the value of a simplified ATP test for noninvasive diagnosis of DAVNP and abolition or modification of the slow pathway (SP) after radiofrequency ablation (RFA) in patients with inducible sustained AVNRT. METHODS AND RESULTS: The value of a single dose of ATP was studied in 105 patients with inducible sustained AVNRT and in 31 control patients before placement of EP catheters in the cardiac chambers. ATP (10 to 60 mg, in 10-mg increments) was injected during sinus rhythm until ECG signs of DAVNP (> or = 50 msec increase or decrease in PR interval in two consecutive beats, or occurrence of > or = 1 AV nodal echo beat) or > or = second-degree AV block was observed. DAVNP was observed in only 1 (3.2%) control patient. The test could be completed in 96 study patients. DAVNP was found by ATP test in 72 (75%) patients, whereas it was diagnosed by EP criteria in 82 (85%) patients. DAVNP by ATP test disappeared in 27 (96%) of 28 patients who underwent SP abolition and in 18 (60%) of 30 patients who underwent SP modification. In the 12 patients with persistent DAVNP determined by ATP test after SP modification, the number of beats conducted over the SP was significantly reduced (from 6.3+/-3.3 to 2.5+/-2.2 beats; P = 0.002). CONCLUSION: A single administration of ATP during sinus rhythm (at a given dose) enables noninvasive diagnosis of DAVNP in a high percentage of patients with inducible AVNRT and reliably confirms the results of RFA of the SP.     

Adenosine in the noninvasive diagnosis of dual AV nodal conduction: use as a follow-up parameter after slow pathway ablation in AVNRT

OBJECTIVE: The aim of this study was to evaluate if administration of adenosine during sinus rhythm to patients with PSVT of unknown mechanism is capable to detect dual AV nodal conduction and furthermore to evaluate this diagnostic parameter as a controlling test after slow pathway ablation in AVNRT. METHODS AND RESULTS: Before electrophysiological study 35 consecutive patients with PSVT were given adenosine during sinus rhythm. After radiofrequency ablation the adenosine test was repeated in a subset of 19 patients. The electrophysiological study revealed 19 patients (54%) with typical AVNRT (study group), 10 (29%) with atrioventricular reentry tachycardia (AVRT), 4 (11%) with ectopic atrial tachycardia (EAT) and 2 patients (6%) with inducible atrial flutter (AF) (control group). We observed a sudden increment of the PQ interval of more than 50 msec between two consecutive beats in 15 of 19 patients (79%) in the study group (75+/-35 msec) and in 2 patients (1 with EAT, AF) of the control group (19+/-12 msec) (p<0.001). After slow pathway radiofrequency ablation the sudden increment of PQ interval persisted in 4 of 12 patients (33%) of the study group. Three of these 4 patients had a relapse of AVNRT during a follow-up of 3 months. CONCLUSION: The administration of adenosine during sinus rhythm is an excellent noninvasive diagnostic test for identifying dual AV nodal conduction and additionally for verifying radiofrequency ablation results in patients with AVNRT.     

Adenosine-5'-triphosphate test for the noninvasive diagnosis of concealed accessory pathway

OBJECTIVES: This study assessed the use of adenosine triphosphate (ATP) in the noninvasive diagnosis of concealed accessory pathway (AP) and dual atrioventricular (AV) node physiology in patients with inducible AV reentrant tachycardia (AVRT). BACKGROUND: Administration of ATP during sinus rhythm identifies dual AV node physiology in 76% of patients with inducible sustained slow/fast AV nodal reentry tachycardia (AVNRT). METHODS: Incremental doses of ATP were intravenously administered during sinus rhythm to 34 patients with inducible sustained AVRT involving a concealed AP and to 27 control patients without AP or dual AV node physiology. One study group patient could not complete the study and was excluded from analysis. RESULTS: The AV reentrant echo beats (AVRE), or AVRT, suggestive of the presence of concealed AP, were observed after ATP administration in 24 (73%) study patients and in none of the control group. Electrocardiographic signs suggestive of dual AV node physiology were observed after ATP administration in 7 (21%) study patients and in none of the control group. Most instances of AVRE/AVRT were preceded by a slight increase (<50 ms) in PR interval. In 8 of 9 patients tested, neither AVRE nor AVRT was no longer observed following ATP administration after successful radiofrequency ablation of the AP. In the remaining patient, a different AVRE due to the presence of an additional AP was observed. CONCLUSIONS: Administration of ATP during sinus rhythm may be a useful bedside test for identifying patients with concealed AP who are prone to AVRT and those with associated dual AV node pathways.     

Conduction properties of the antegrade fast and slow AV nodal pathways associated with AV nodal reentrant tachycardia.

To elucidate differences in conduction properties among the normal atrioventricular (AV) node and the antegrade fast and slow dual AV nodal pathways (DAVNPW), AV nodal conduction curves were analyzed quantitatively in 38 patients. Eighteen patients had antegrade DAVNPW with AV nodal reentrant tachycardia (AVNRT) (dual pathways group) and the remaining 20 had smooth AV nodal conduction curves, without evidence of AV nodal dysfunction (control group). The effective refractory period (ERP) of the antegrade fast pathway was longer than that of the normal AV node (at both basic cycle lengths of 700 and 500 msec, p less than 0.01). Although the atrial premature beats were delayed by a longer ERP in the fast pathway, there was no significant difference in the degree of prolongation of AV nodal conduction time related to shortening of the coupling interval (i.e., ratio of A2H2 increment to A1A2 decrement) between these two pathways. On the other hand, the ERP of the antegrade slow pathway was similar to that of the normal AV node. The degree of prolongation of AV nodal conduction time (relative to the shortening of the coupling interval) was greater in the antegrade slow pathway than in the normal AV node. In conclusion, these findings suggest that in DAVNPW with AVNRT: (1) the antegrade fast pathway is similar to the AV node and its conduction properties are unlikely to be better than those of the normal AV node and (2) the antegrade slow pathway has quantitatively poorer conduction properties than the normal AV node, since it has a greater degree of decremental conduction.     

The adenosine triphosphate test: a bedside diagnostic tool for identifying the mechanism of supraventricular tachycardia in patients with palpitations.

OBJECTIVES: This study assesses the value of the "ATP test" (injection of adenosine triphosphate [ATP] during sinus rhythm) for identifying patients with palpitations of unclear etiology who actually have atrioventricular (AV) nodal re-entry tachycardia (AVNRT) or AV re-entry tachycardia (AVRT). BACKGROUND: Because AVNRT and AVRT can be cured with radiofrequency ablation, documentation of spontaneous AVNRT or AVRT usually prompts referral for electrophysiologic (EP) evaluation. However, these paroxysmal arrhythmias may elude clinical diagnosis. We recently showed that administration of ATP during sinus rhythm often reveals dual AV node physiology or a concealed accessory pathway (AP) in patients with documented AVNRT or AVRT. Thus, we postulated that the ATP test could identify patients with palpitations who actually have AVNRT or AVRT and would therefore benefit from EP evaluation. METHODS: One hundred forty-six patients (54 with "palpitations without documented arrhythmias" and 92 with "documentation of arrhythmias of unclear mechanism") underwent a noninvasive ATP test. ATP was injected during sinus rhythm using 10 mg increments. The ATP test was considered positive when prospectively defined signs of dual AV node physiology or concealed AP were disclosed in the electrocardiogram. These findings were correlated with the results of EP evaluation. RESULTS: A positive ATP test predicted induction of AVNRT or AVRT with a positive predictive value of 93% (sensitivity 71%) but a negative predictive value of 37% (specificity 76%). CONCLUSIONS: A bedside ATP test identifies patients with palpitations who are likely to have AVNRT or AVRT (and who are therefore likely to benefit from EP evaluation) with a high positive predictive value.     

Reentrant and nonreentrant forms of atrio-ventricular nodal tachycardia mimicking atrial fibrillation

BACKGROUND: Atrial fibrillation (AF) manifests disorganized atrial activity and irregular R-R intervals on electrocardiogram (ECG). Variation in R-R intervals can also be seen with other supraventricular tachycardias that may mimic AF. OBJECTIVE: We report our observations on three patients who were referred to our center to undergo pulmonary vein (PV) isolation for erroneously diagnosed AF in the setting of dual atrio-ventricular (AV) nodal pathways manifesting as AV nodal reentrant tachycardia (AVNRT) and/or double response during sinus rhythm. METHODS AND RESULTS: These three subjects (two females) were derived from a group of 456 consecutive patients undergoing AF ablation at our center over a 3-year period. All three patients had been symptomatic for over 2 years, having failed two or more antiarrhythmic medications. In each case AF was initially diagnosed on ECG and/or recordings from ambulatory monitoring. However, in all three cases the correct diagnosis was established during the invasive electrophysiologic study. In one patient during the stimulation protocol, two narrow complex tachycardias were serially induced (cycle lengths: 305 and 360 msecs; VA time: 60 and 240 msecs). The latter was confirmed to be atypical AVNRT and during this tachycardia, block in upper pathway was observed. In the other two patients, sinus rhythm with repetitive runs of double response and isolated junctional beats were observed in the absence of retrograde conduction. Successful slow pathway modification was performed in each subject and all three patients have remained arrhythmia free over a mean follow-up of 31 +/- 16 months off antiarrhythmic medications. CONCLUSIONS: AF can be erroneously diagnosed in patients with dual AV nodal pathways manifesting double response and/or AVNRT. Incorporating a stimulation protocol as a part of the AF ablation procedure may help in diagnosing these rare clinical presentations that can be cured by slow pathway modification alone.     

Pseudo-atrial fibrillation, rare manifestation of multiple anterograde atrioventricular nodal pathways

In patients with dual or multiple atrioventricular (AV) nodal pathways manifesting nonreentrant tachycardia or unusual forms of AV nodal reentry, paroxysmal atrial fibrillation is often misdiagnosed and patients may erroneously be considered for pulmonary vein isolation. Multiple anterograde slow AV nodal pathways, identified by >1 discontinuity in the anterograde AV nodal conduction curve, are not rare in patients with slow-fast AV nodal reentrant tachycardia (AVNRT). However, only 1 slow AV nodal pathway is usually involved in anterograde conduction during tachycardia. It was reported that patients with multiple anterograde slow AV nodal pathways presented with different tachycardia cycle lengths. For the first time, 2 patients with AVNRT in which maintenance of tachycardia was strictly dependent on participation of 3 different anterograde slow AV nodal pathways in an uniquely alternating sequence are reported. In both patients, a single application of radiofrequency energy in the posterior aspect of Koch's triangle eliminated simultaneously all evidence of anterograde slow pathway conduction. These findings implied that functional differences in a determined circuit based on nonuniform anisotropy rather than anatomically distinct pathways form the electrophysiologic basis for this rare variant of AVNRT. In conclusion, particularly in patients with lone atrial fibrillation who are potential candidates for pulmonary vein isolation, careful analysis of the surface electrocardiogram during irregular supraventricular tachycardia and invasive electrophysiologic examination helps identify rare arrhythmia mechanisms that can be cured by slow pathway ablation alone.     

Double ventricular responses during extrastimulation of atrioventricular nodal reentrant tachycardia

In patients with dual atrioventricular (AV) nodal pathways,double ventricular responses to a single atrial depolarizationhave been shown to occur, but virtually only during a trialpacing in sinus rhythm. We report on a patient with a slow-fastform of AV nodal reentrant tachycardia who exhibited doubleventricular responses following extrastimulation during AV nodalreentrant tachycardia. The phenomenon of double ventricularresponses during the tachycardia was demonstrated by ex trastimulationfrom the proximal coronary sinus. Retrograde unidirectionalblock in the slow pathway, and an anterograde effective refractoryperiod that was shorter in the fast pathway than that in theslow pathway, are suggested.     

Use of adenosine as a diagnostic tool for dual atrioventricular nodal pathways: response of control patients to incremental doses of adenosine

BACKGROUND: Adenosine at low doses preferentially blocks fast over slow pathway conduction in patients with dual atrioventricular (AV) nodal physiology and typical AV nodal reentrant tachycardia (AVNRT). During atrial pacing, this effect is manifested as an abrupt increase in the AH interval with low doses of adenosine. This demonstration of dual AV nodal physiology may be useful as a diagnostic tool during electrophysiologic studies in patients with supraventricular tachycardia who are not easily inducible, as clear demonstration of dual AV nodal pathways may indicate that AVNRT is a likely diagnosis and that further attempts at arrhythmia induction should be tailored in that direction. However, to be a useful test, adenosine should not cause an abrupt increase in AH interval in patients without dual AV nodal physiology. HYPOTHESIS: This study was designed to investigate the prevalence of dual AV nodal pathways with administration of adenosine in patients with no history suggestive of AVNRT. METHODS: Thirty-seven patients who had no prior history of AVNRT and were undergoing electrophysiologic study for standard indications were enrolled. Baseline Wenckebach cycle length (WCL) and AV nodal effective refractory periods were measured at atrial pacing cycle lengths of 400 and 600 ms. The atrium was then paced at WCL + 50 ms, and WCL + 100 ms, while incrementally larger doses of intravenous adenosine were administered until AV nodal block occurred. RESULTS: The mean (+/- standard deviation) doses of adenosine required to cause AV nodal block while pacing at WCL + 50 ms and WCL + 100 ms were 7.1 +/- 3.9 and 7.4 +/- 4.5 mg, respectively. In 1 of 37 patients (2.7%, 95% confidence interval 0-8%), an abrupt prolongation of the AH interval was seen with the administration of adenosine during atrial pacing as well as during the atrial refractory period determination. In all other patients, no dual AV nodal physiology was demonstrated during the refractory period determination, and there were only gradual changes in the AH interval with atrial pacing during administration of adenosine. CONCLUSION: Among patients with no history suggestive of AV nodal reentrant tachycardia, only 2.7% have clinically silent dual AV nodal pathways using this method. Incremental adenosine infusion during electrophysiologic study can be used as a highly specific diagnostic tool for patients with dual AV nodal pathways.     

Multiple AV nodal pathways in patients with AV nodal reentrant tachycardia--more common than expected?

AIMS: It was the purpose of this study to determine the incidence of more than two AV nodal pathways in patients with AVNRT. METHODS AND RESULTS: In 78 consecutive patients with AV-nodal reentrant tachycardias (AVNRT) (50 females, 28 males, mean age 52.8 +/- 14.6 years), the number of sudden AH increases by 50 ms or more (AH-jump) was analysed during atrial extrastimulation. The incidence of two AV nodal pathways was accepted to be present in patients with AVNRT without an AH-jump ('smooth curve'). The following forms of tachycardia were induced: a typical AVNRT (slow-fast) in 67 patients, an atypical AVNRT (fast-slow) in 12 patients and a slow-slow-AVNRT in 4 patients. Five patients had two forms of AVNRT. 47 patients (60.3%) showed two AV nodal pathways, 27 patients (34.6%) had three AV-nodal pathways and 4 patients (5.1%) exhibited four AV-nodal pathways. For successful catheter ablation of AVNRT in patients with more than two pathways, more radiofrequency energy applications were required (9.2 +/- 6.3) compared with patients with only two pathways (6.7 +/- 4.8). Furthermore, in patients with more than two AV-nodal pathways, the catheter intervention resulted more frequently in a modulation of slow pathway conduction than in an ablation of the slow pathway(s). CONCLUSION: The incidence of more than two AV-nodal pathways in patients with AVNRT was unexpectedly high at about 40%. Thus, these tachycardias require a meticulous electrophysiological evaluation for successful ablation.     

Simultaneous antegrade dual AV node conduction initiates AV nodal re-entrant tachycardia (a rare initiation mechanism)

Typical atrioventricular nodal reentrant tachycardia (AVNRT) is the most common paroxysmal supraventricular tachycardia among adults. The concept of dual pathway physiology remains widely accepted, although this physiology likely results from the functional properties of anisotropic tissue within the triangle of Koch, rather than anatomically distinct tracts of conduction. AVNRT is typically induced with anterograde block over the fast pathway and conduction over the slow pathway, with subsequent retrograde conduction over the fast pathway. On rare occasions, anterograde AV node conduction occurs simultaneously through fast and slow pathways resulting in two ventricular beats in response to one atrial beat. We report a case of AVNRT where the tachycardia is always induced by the same mechanism described above. Successful ablation was achieved by slow pathway modification.     

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.     

Atrioventricular nodal reentry tachycardia in children: curative treatment by high frequency catheter ablation

BACKGROUND: Atrioventricular nodal reentrant tachycardia (AVNRT) is one of the most common forms of supraventricular tachycardia in the pediatric population. PATIENTS AND METHODS: 41 children with a mean age of 9.6 (3.7-16) years with recurrent atrioventricular nodal reentrant tachycardia (AVNRT) refractory to medical treatment (n = 38) and recurrent syncope (n = 3) underwent electrophysiologic (EP) study. In all patients dual AV-nodal physiology could be demonstrated during EP study and typical form of AVNRT (mean heart rate 220/min) could be induced by programmed atrial stimulation. A steerable 7 F ablation catheter was placed at the inferoparaseptal region of the tricuspid valve annulus close to the orifice of the coronary sinus with the intention to record a late fractionated local atrial electrogram during sinus rhythm. Starting at this point radiofrequency current (500 kHz) with a target temperature of 70 degrees C was delivered with the intention to ablate the slow pathway. If a slowly accelerated junctional rhythm (< 120/min) occurred during energy discharge, programmed atrial stimulation was repeated. Otherwise radiofrequency current was delivered step by step up to a septal position next to the tricuspid valve annulus. Slow pathway ablation was defined as lack of evidence of dual AV nodal pathways during repeated atrial stimulation. Slow pathway modulation was defined as maximal one atrial echoimpulse after ablation. RESULTS: The number of energy applications ranged from 1-19 (median 6). In 35/41 patients slow pathway ablation could be achieved; in six patients the slow pathway was modulated. In none of the patients permanent high grade AV block was observed. During follow-up (mean 4.1 years) two patients had a recurrent episode of AVNRT after slow pathway modulation. All other patients are still free of AVNRT without medical treatment. CONCLUSION: Selective radiofrequency current ablation/modulation of the slow pathway is a safe and curative treatment of AVNRT in young patients.     

Electrophysiologic Spectrum of Atrioventricular Nodal Behavior in Patients with Atrioventricular Nodal Reentrant Tachycardia Undergoing Selective Fast or Slow Pathway Ablation

AV Nodal Behavior After Ablation. Introduction; The objective of this report is to delineate the atrioventricular (AV) nodal electrophysiologic behavior in patients undergoing fast or slow pathway ablation for control of their AV nodal reentrant tachycardia (AVNRT).
Methods and Results: One hundred sixteen consecutive patients with symptomatic AVNRT were included. Twenty-two patients underwent fast pathway ablation with complete abolition of AVNRT in all and development of complete AV block in five patients. Of 17 patients with intact AV conduction postablation, 12 had demonstrated antegrade dual pathway physiology during baseline study, which was maintained in three and lost in nine patients postablation. Two patients with successful fast pathway ablation developed uncommon AVNRT necessitating a slow pathway ablation. Twenty-one patients demonstrated both common and uncommon forms of AV nodal reentry during baseline study. The earliest site of atrial activation was close to the His-bundle recording site (anterior interatrial septum) during common variety and the coronary sinus ostium (posterior interatrial septum) during the uncommon AV nodal reentry in all 21 patients. Ninety-six patients underwent successful slow pathway ablation. Among these, the antegrade dual pathway physiology demonstrable during baseline study (60 patients) was maintained in 25 and lost in 35 patients postablation.
Conclusion: These data suggest that: (1) dual pathway physiology may persist after successful ablation, which might be a reflection of multiple reentrant pathways in patients with AVNRT: and (2) the retrograde pathways during common and uncommon AVNRT have anatomically separate atrial breakthroughs. These findings have important electrophysiologic implications regarding the prevailing concept of the AV nodal physiology in patients with AVNRT.     

Distal end of the atrioventricular nodal artery predicts the risk of atrioventricular block during slow pathway catheter ablation of atrioventricular nodal re-entrant tachycardia

OBJECTIVE—To search for a reliable anatomical landmark within Koch's triangle to predict the risk of atrioventricular (AV) block during radiofrequency slow pathway catheter ablation of AV nodal re-entrant tachycardia (AVNRT).
PATIENTS AND METHODS—To test the hypothesis that the distal end of the AV nodal artery represents the anatomical location of the AV node, and thus could be a useful landmark for predicting the risk of AV block, 128 consecutive patients with AVNRT receiving slow pathway catheter ablation were prospectively studied in two phases. In phase I (77 patients), angiographic demonstration of the AV nodal artery and its ending was performed at the end of the ablation procedure, whereas in the subsequent phase II study (51 patients), the angiography was performed immediately before catheter ablation to assess the value of identifying this new landmark in reducing the risk of AV block. Multiple electrophysiologic and anatomical parameters were analysed. The former included the atrial activation sequence between the His bundle recording site (HBE) and the coronary sinus orifice or the catheter ablation site, either during AVNRT or during sinus rhythm. The latter included the spatial distances between the distal end of the AV nodal artery and the HBE and the final catheter ablation site, and the distance between the HBE and the tricuspid border at the coronary sinus orifice floor.
RESULTS—In phase I, nine of the 77 patients had complications of transient (seven patients) or permanent (two patients) complete AV block during stepwise, anatomy guided slow pathway catheter ablation. These nine patients had a wider distance between the HBE and the distal end of the AV nodal artery, and a closer approximation of the catheter ablation site to the distal end of the AV nodal artery, which independently predicted the risk of AV block. In contrast, none of the available electrophysiologic parameters were shown to be reliable. When the distance between the distal end of the AV nodal artery and the ablation target site was more than 2 mm, the complication of AV block virtually never occurred. In phase II, all 51 patients had successful elimination of the slow pathways without complication when the ablation procedure was guided by preceding angiography with identification of the distal end of the AV nodal artery.
CONCLUSIONS—The distal end of the AV nodal artery shown by angiography serves as a useful landmark for the prediction of the risk of AV block during slow pathway catheter ablation of AVNRT.


Keywords: atrioventricular nodal artery; atrioventricular nodal re-entrant tachycardia; catheter ablation; heart block.     

Junctional rhythm occurring during AV nodal reentrant tachycardia ablation,is it different among Egyptians?

IntroductionRadio frequency ablation of the slow pathway has become first-line therapy for the elimination of AV nodal reentrant tachycardia (AVNRT). Slow pathway ablation is guided by a combination of fluoroscopic landmarks, electrogram morphology, and the induction of accelerated junctional rhythm (JR) during the application of radiofrequency energy. Although JR occurs usually during slow pathway ablation of AVNRT, the pattern of JR has not been adequately studied.¹³Aim of the studyTo investigate in detail the characteristics of junctional rhythm occurring during radiofrequency ablation of atrioventricular nodal reentrant tachycardia AVNRT among Egyptians.MethodsThis study included 30 patients who underwent electrophysiological study for narrow complex supraventricular regular tachycardia which revealed to be AVNRT.ResultsThirty (100%) patients showed induction of junctional rhythm at the successful ablation sites. JR was a very sensitive predictor of successful ablation but not so specific with specificity of 60%. Sex patterns of JR were observed. The most common pattern of JR was sinus–junctional–junctional (SJJ) while sinus–junctional-block (SJB) was the least. The most specific pattern for effective ablation was junctional–junctional–junctional (JJJ), while intermittent burst was the least. P value is 0.001 i.e. highly significant.ConclusionJunctional rhythm is a sensitive predictor of successful ablation. The pattern of JR is a useful predictor of successful ablation. Egyptian population has distinctive patterns of JR during AVNRT ablation.     

Atrioventricular nodal reentrant tachycardia in children: effect of slow pathway ablation on fast pathway function

INTRODUCTION: Prior studies in adults have shown significant shortening of the fast pathway effective refractory period after successful slow pathway ablation. As differences between adults and children exist in other characteristics of AV nodal reentrant tachycardia (AVNRT), we sought to characterize the effect of slow pathway ablation or modification in a multicenter study of pediatric patients. METHODS AND RESULTS: Data from procedures in pediatric patients were gathered retrospectively from five institutions. Entry criteria were age <21 years, typical AVNRT inducible with/without isoproterenol infusion, and attempted slow pathway ablation or modification. Dual AV nodal pathways were defined as those with > or =50 msec jump in A2-H2 with a 10-msec decrease in A1-A2. Successful ablation was defined as elimination of AVNRT inducibility. A total of 159 patients (age 4.4 to 21 years, mean 13.1) were studied and had attempted slow pathway ablation. AVNRT was inducible in the baseline state in 74 (47%) of 159 patients and with isoproterenol in the remainder. Dual AV nodal pathways were noted in 98 (62%) of 159 patients in the baseline state. Ablation was successful in 154 (97%) of 159 patients. In patients with dual AV nodal pathways and successful slow pathway ablation, the mean fast pathway effective refractory period was 343+/-68 msec before ablation and 263+/-64 msec after ablation. Mean decrease in the fast pathway effective refractory period was 81+/-82 msec (P < 0.0001) and was not explained by changes in autonomic tone, as measured by changes in sinus cycle length during the ablation procedure. Electrophysiologic measurements were correlated with age. Fast pathway effective refractory period was related to age both before (P = 0.0044) and after ablation (P < 0.0001). AV block cycle length was related to age both before (P = 0.0005) and after ablation (P < 0.0001). However, in dual AV nodal pathway patients, the magnitude of change in the fast pathway effective refractory period after ablation was not related to age. CONCLUSION: Lack of clear dual AV node physiology is common in pediatric patients with inducible AVNRT (38%). Fast pathway effective refractory period shortens substantially in response to slow pathway ablation. The magnitude of change is large compared with adult reports and is not completely explained by changes in autonomic tone. Prospective studies in children using autonomic blockade are needed.     

动态心电图对伴长不应期快径的房室结双径路的诊断价值

目的：明确24h动态心电图对伴长不应期快径的房室结双径路（DAVNP）的诊断价值。方法：对84例DAVNP合并房室结折返性心动过速（AVNRT）的患者进行24h动态心电图（DCG）监测。结果：3例患者在DCG示间歇性PR间期延长．伴心悸等不适。食管电生理显示快径有效不应期（ERP）延长，大于500ms。结论：DAVNP患者有时快径呈间歇性延长，DCG有助于其确定。     

Long-term outcome of AV node modulation in 387 consecutive patients with AV nodal reentrant tachycardia

Aim of this study was to assess the long-term results of AV-node modulation in patients with AV nodal reetrant tachycardia. METHODS: From December 1991 until September 1999, AV node modulation (ablation of the fast pathway or ablation/modification of the slow pathway) was performed in 387 consecutive patients with clinically apparent AV nodal reentrant tachycardia. Follow-up data was available in 95% of patients with a mean of 41 +/- 26 months after ablation. RESULTS: Acute success rate was 97%. During long-term follow-up recurrence rate was 7.4% without any difference between fast and slow pathway ablation. Recurrence occurred in 23% of patients with persistent dual AV node physiology after ablation (modification of the slow pathway) in contrast to 3% without dual AV node physiology (ablation of the slow pathway) (p = 0.002). The presence of a dual AV node physiology after slow pathway modulation was the only predictor of recurrence during long-term follow-up. The complication rate was 5.7%. The incidence of complete heart block was 1% without any difference between fast and slow pathway ablation. CONCLUSIONS: Catheter modulation of the AV node for the treatment of AV nodal reentrant tachycardia is effective and safe. During long-term follow-up, the recurrence rate was low. Modulation of the slow pathway is associated with a significantly higher recurrence rate than ablation of the slow pathway.     

程控刺激不能诱发的房室结折返性心动过速慢径消融的临床疗效评估

目的　评价程控刺激不能诱发的房室结折返性心动过速 (AVNRT)射频消融慢径的临床疗效。方法　 6 1例有心动过速病史且心电图疑诊为AVNRT的病人 ,电生理检查有房室结双径(DAVNP)但不能诱发AVNRT ,随机分为两组。A组 30例不消融而进行临床随访 ,当心动过速复发且经心电图证实为窄QRS心动过速者接受射频消融阻断慢径。B组 31例接受射频消融以阻断慢径 ,术后临床随访。结果　A、B两组分别有 2 4例和 2 7例病人完成随访。A组 2 4例随访中分别在 1年内发作心动过速 ,再次接受消融阻断慢径后随访 (12 .1± 12 .2 )个月 ,仅 1例复发心动过速 (4.2 % ) ,与消融前比较差异有显著性 (P <0 .0 0 0 1)。B组 2 7例平均随访 (2 4 .2± 17.6 )个月 ,1例复发心动过速 (3.7% ) ,与A组病人消融前相比差异有显著性 (P <0 .0 0 0 1) ,而与其消融后比较差异无显著性 (P >0 .0 5 )。结论　有阵发性心动过速病史且心电图疑诊为AVNRT的病人 ,电生理检查有DAVNP而不能诱发心动过速者 ,射频消融阻断慢径具有良好的临床疗效。