Electrophysiological Behavior of Atrioventricular Node After Selective Fast or Slow Pathway Ablation in Patients with Atrioventricular Nodal Reentrant Tachycardia

One hundred twenty consecutive patients with symptomatic atrioventricular nodal reentrant tachycardia (AVNRT) underwent catheter ablation using radiofrequency energy. Fast pathway ablation was attempted in the first 16 consecutive patients by application of radiofrequency current in the anterior and superior aspect of the tricuspid annulus. Successful results were accomplished in 13 patients, complete atrioventricular (AV) block occurred in three. One hundred four patients underwent ablation of the slow pathway in the posterior and inferior aspect of the tricuspid annulus, which was successful in 98 patients. The remaining six patients subsequently underwent a fast pathway ablation with successful results in four and AV block in two. Therefore. 102 (98%) of the last 104 patients became free of AVNRT while maintaining intact AV conduction. This study characterizes the electrophysiological properties of the residual AV node following a selective fast or slow pathway ablation.     

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.     

High success rate with cryomapping and cryoablation of atrioventricular nodal reentrytachycardia

INTRODUCTION: Cryoablation is a new alternative to radiofrequency (RF) ablation for treatment of atrioventricular nodal reentry tachycardias (AVNRT). Mapping with reversible effect on the arrhythmia substrate or the AV node can be done before irreversible ablation is performed. This study evaluates an approach with systematic cryomapping, ablating only in areas with prompt effect on the arrhythmia substrate and evaluates whether the success rates and procedure times are similar to RF ablation. METHODS AND RESULTS: Seventy-five consecutive patients with typical slow-fast AVNRT were studied. Cryomapping at -30 degrees C was performed before ablation with a goal temperature of -70 degrees C for 240 seconds. The ablation procedure was successful in 74 of the 75 patients, giving an acute success rate of 99%. During a mean follow-up of 338 days, 70 of the 74 primarily successfully ablated patients were free from the treated arrhythmia, giving a recurrence rate of 5% and a total success rate of 93%. Total procedure time including a 30-minute test after successful ablation was 126+/-55 minutes. Fluoroscopy time was 18.5+/-14.9 minutes. CONCLUSION: Cryoablation of AVNRT appears to be as effective as RF ablation both acute and in long term with minimal risks for unwanted injuries on the conduction system. The procedure can be done with reasonable procedure and fluoroscopy times.     

Predictors of acute and long-term success of slow pathway ablation for atrioventricular nodal reentrant tachycardia: a single center series of 1,419 consecutive patients

Background: Atrioventricular nodal reentrant tachycardia (AVNRT) is the most common mechanism of supraventricular tachycardia. Slow pathway (SP) ablation is the first‐line treatment approach with a high acute success rate and a low risk of inadvertent complete atrioventricular (AV) block. However, there is still some uncertainty as to the most appropriate procedural endpoints and the impact of these on risk of recurrence. We report the acute and long‐term results of SP ablation in a large single‐center consecutive series and analyze predictors of acute success and late recurrence. Methods: The study included 1,448 consecutive procedures in 1,419 patients with AVNRT (mean age 49 ± 17 years, 66% women) who underwent SP ablation using a combined electrophysiologic and anatomic approach. Univariate and multivariate analysis was performed for potential predictors of acute success and late recurrence. Results: Acute success was achieved in 98.1%. Transient (first, second, or third degree) AV block occurred during the procedure in 20 (1.41%) patients. One patient (0.07%) had persistent first‐degree and transient second‐degree AV block after ablation and underwent pacemaker implant at day 21. Of the 1,391 patients with successful ablation, 22 patients (1.5%) developed AVNRT recurrence during a follow‐up period of 63 ± 38 months. The only independent predictor of reduced procedural success was the presence of atypical AVNRT (hazard ratio 3.1, P = 0.04). Independent predictors of AVNRT recurrence were age <20 years and female gender (hazard ratios 14.1 and 3.7, respectively). No significant difference in the incidence of late recurrence was observed in patients with or without residual slow‐pathway conduction, or according to use of isoproterenol testing or general anesthesia. However, patients with a single echo with recurrence had a significantly larger echo window (median 85 ms) than those without (median 30 ms, P = 0.01). Conclusions: This study demonstrates in a large consecutive single‐center series that SP ablation using radiofrequency energy is a highly effective procedure with an extremely low risk of inadvertent AV block and a low recurrence rate. We found that single‐AV nodal echo beats represented a procedural endpoint that did not predict AVNRT recurrence but that a large echo window is associated with recurrence. Recurrence rates in this series were higher in young women, possibly reflecting a more conservative approach to ablation in this age group. (PACE 2011; 34:927–933)     

房室结双径路消融中特殊电生理现象分析与处理

目的 :分析房室结折返性心动过速 (AVNRT)慢径路消融中特殊电生理现象及处理体会。方法 :慢径路消融前常规行心内电生理检查。结果 :有特殊电生理现象者 8例 ,其中 3例患者AVNRT开始时表现为房室 2 :1传导 ,阻滞点在希氏束以上部位 ;3例患者房室结功能曲线呈连续性 ;1例为慢 -慢型AVNRT ;1例心内电生理检查未能诱发出AVNRT。所有患者慢径消融均成功。结论 :术前应行详细的心内电生理检查和仔细鉴别 ,其消融方法与典型AVNRT相同     

Junctional Rhythm—A Suitable Surrogate Endpoint in Catheter Ablation of Atrioventricular Nodal Reentry Tachycardia?

INTRODUCTION: Current AHA/ACC guidelines state that junctional rhythm (JR) is an acceptable endpoint in patients undergoing radiofrequency ablation (RFA) for narrow complex tachycardia in the presence of dual AV nodal physiology, but in the absence of inducible AVNRT. Only limited data are available on the utility of JR as a marker of successful slow pathway ablation. We sought to further characterize the sensitivity, specificity, and predictive value of JR in AVNRT ablation. METHODS: A retrospective analysis was performed of 387 consecutive patients with documented narrow complex tachycardia referred for ablation, with dual AV nodal physiology and inducible AVNRT at electrophysiological study. RFA of slow pathway was performed, with the presence or absence of JR recorded for each application and inducibility tested using atrial stimulation protocol and isoproterenol. RESULTS: Successful ablation was achieved in 385 of 387 patients using a total of 1,861 applications of radiofrequency energy. JR occurred in 692 applications, giving a sensitivity and specificity of JR as an indicator of successful ablation of 99.5% and 79.1% and a positive predictive value of 55.5%. CONCLUSIONS: This study confirms that successful ablation of slow pathway seldom occurs in the absence of JR. Although JR almost invariably occurs with successful ablation, its lack of specificity and low positive predictive value questions the use of it as an endpoint in AVNRT ablations, and the guidelines should reflect this.     

Palpitations Occur Frequently Following Radiofrequency Catheter Ablation for Supraventricular Tachycardia, But Do Not Predict Pathway Recurrence

Radiofrequency ablation of extranodal pathways is an effective treatment for supraventricular tachycardia, but late recurrences of pathway conduction do occur. To determine if recurrence of palpitations following ablation predicts pathway recurrence, we interviewed 77 patients who were at Jeast 4 weeks status-post successful ablation of an accessory pathway (43 overt, 11 concealed)or a slow pathway (23)for AV nodal reentrant tachycardia. Palpitations were reported by 45 (58%)patients postablation, and 28 (36%)patients reported palpitations lasting ≥10 seconds and/or felt their symptoms represented recurrent tachycardia (major palpitations). Repeat electrophysiological testing was performed 3 months postablation in 53 patients, including 34 patients with palpitations (22 with major symptoms). Eight (10%)patients had recurrent pathway conduction demonstrated on repeat testing: two had no symptoms prior to restudy and six had major symptoms. One patient had major symptoms, but was found to have inducible atrial tachycardia and not pathway recurrence on restudy. Thus, 15 (68%)of 22 patients with major symptoms who were restud-ied had no pathway recurrence or inducible arrhythmia to explain their symptoms. Of the 24 patients not restudied, none has had documented recurrent tachycardia or overt pathway conduction by electrocardiogram over a mean follow-up of 335 ± 138 (range 132–616)days. Thus, palpitations, including palpitations reminiscent of preablation symptoms, are common following radiofrequency ablation and often do not predict pathway recurrence. Repeat electrophysiological testing is frequently required to document long-term success of radiofrequency ablation for supraventricular tachycardia in patients with recurrence of major symptoms.     

Determination of Repetitive Slow Pathway Conduction for Evaluation of the Efficacy of Radiofrequency Ablation in AVNRT

LUKAC, P., et al.: Determination of Repetitive Slow Pathway Conduction for Evaluation of the Efficacy of Radiofrequency Ablation in AVNRT. Aims: To determine whether the loss of repetitive slow pathway conduction identifies a successful radiofrequency ablation of atrioventricular nodal reentry tachycardia (AVNRT). Methods and results: Thirty nine consecutive patients undergoing ablation of AVNRT using the slow pathway approach were included. At baseline and after each radiofrequency application with an episode of junctional rhythm, repetitive slow pathway conduction was assessed as follows: Effective refractory period of the fast pathway was determined. The coupling interval of the first atrial extrastimulus (A2) was set at 30 ms below the effective refractory period of the fast pathway to ensure its conduction via the slow pathway. The second atrial extrastimulus (A3) was introduced at progressively longer coupling intervals starting from 200 ms until: (1) it propagated to the His bundle or (2) an anterogradely blocked AV nodal echo of A2 appeared before a conducted A3 depolarized the atrium in the His bundle electrogram. The response was termed repetitive slow pathway conduction if A3 was conducted with an   AH > 200 ms   . Application was considered successful if no AVNRT could be induced. Repetitive slow pathway conduction was present after 1 of 39 successful and after 34 of 40 ineffective applications   (P < 0.0001)   . Repetitive slow pathway conduction identified a successful application with 97% sensitivity, 86% specificity, 86% positive predictive value, and 97% negative predictive value. Conclusion: The presence of repetitive slow pathway conduction identifies an unsuccessful application with a clinically meaningful negative predictive value. (PACE 2003; 26[Pt. I]:827–835)     

Frequency of spontaneous and inducible atrioventricular nodal reentry tachycardia in patients with idiopathic outflow tract ventricular arrhythmias

OBJECTIVES: We sought to assess the frequency of spontaneous or inducible atrioventricular nodal reentry tachycardia (AVNRT) in patients referred for radiofrequency ablation (RFA) of idiopathic outflow tract ventricular arrhythmias. BACKGROUND: In patients with no obvious heart disease, AVNRT and outflow tract ventricular tachycardia (VT) are the most frequently encountered supraventricular and ventricular tachycardias, respectively. An increased coexistence of the two arrhythmias has been recently suggested. METHODS: In 68 consecutive patients referred for RFA of an idiopathic ventricular outflow tract arrhythmia, a stimulation protocol including repeated bursts of rapid atrial pacing, up to triple atrial extrastimuli during sinus rhythm and rapid ventricular pacing was performed before and after isoproterenol infusion following RFA of the ventricular arrhythmia. In patients with inducible AVNRT, RFA of the slow pathway was performed. RESULTS: Of the 68 study patients, 17 (25%) had either spontaneous AVNRT documented prior to RFA of the ventricular arrhythmia (n = 4) or inducible AVNRT at the time of RFA of the ventricular arrhythmia (n = 13). AVNRT was induced by atrial pacing in 15 (88%) of 17 patients: in 3 patients without isoproterenol and in 12 patients during isoproterenol infusion. Uncomplicated RFA of the slow pathway was successfully achieved in all patients with inducible AVNRT. CONCLUSION: Spontaneous or inducible AVNRT is relatively common in patients with idiopathic outflow tract ventricular arrhythmias. Atrial stimulation, especially when performed after isoproterenol infusion plays a major role in AVNRT inducibility. Although we performed RFA of the slow pathway in patients with inducible AVNRT and no prior tachycardia documentation, the question whether this is mandatory remains unsettled.     

Electrophysiology of inducible atrial flutter in patients with atrioventricular nodal reentrant tachycardia

An association between atrial flutter and atrioventricular nodal reentrant tachycardia (AVNRT) has been observed, but the underlying mechanisms are poorly defined. This issue was therefore investigated by comparing the electrophysiological properties of AVNRT patients with and without inducible atrial flutter and those of patients with a history of flutter. Twenty-nine patients with clinically documented atrial flutter and 104 with AVNRT were studied. Atrial flutter was induced in 38 (37%) AVNRT patients during standardized electrophysiological testing before radiofrequency ablation. The atrial relative refractory periods in AVNRT patients with inducible flutter (260 +/- 30 ms) were significantly shorter than those of either patients with a history of flutter (282 +/- 30 ms; P = 0.02) or AVNRT patients without inducible flutter (284 +/- 38 ms; P = 0.006). The atrial effective refractory periods in AVNRT patients with inducible flutter (205 +/- 31 ms) were shorter than in AVNRT patients without inducible flutter (227 +/- 40 ms; P = 0.01). The maximum AH interval during premature atrial stimulation in patients with clinical flutter (239 +/- 94 ms) was shorter than in AVNRT patients either with (290 +/- 91 ms; P = 0.04) or without inducible flutter (313 +/- 101 ms; P = 0.002). However, no significant differences were found in the maximum AH interval achieved during incremental atrial pacing among different groups. Our data show that a non-clinical flutter could more often be induced in those who had short atrial refractoriness. Despite their anatomical proximity, the slow pathway conduction of AVNRT and the isthmus slow conduction of flutter may be related to different mechanisms.     

Sustained Slow Pathway Conduction: Superior to Dual Atrioventricular Node Physiology in Young Patients with Atrioventricular Nodal Reentry Tachycardia?

BACKGROUND: Young patients with atrioventricular nodal reentry tachycardia (AVNRT) frequently do not display discrete dual AV node physiology (DAVNP) as classically defined. The purpose of the study was to investigate the prevalence of sustained slow pathway conduction (SSPC; PR > RR during atrial pacing) in young patients with AVNRT and compare it to dual atrioventricular node physiology. METHODS: The presence of SSPC and DAVNP was prospectively assessed before and after radiofrequency catheter ablation in 61 young patients (age 4-23 years) with typical AVNRT. RESULTS: Prior to ablation, 32 (52%) displayed DAVNP, while 46 (75%) displayed SSPC; 7 patients (11%) had neither marker. Patients with DAVNP were older than those without (15 +/- 3 vs 13 +/- 4, P = 0.027) and the prevalence increased with age (38% <13 years, 50% 13-15, 70% >15, P = 0.041), while SSPC showed no age predilection. Patients under 13 years displayed SSPC more commonly than DAVNP (81% vs 38%, P = 0.004). DAVNP persisted after ablation in 10/32 (31%) patients, compared to 6/46 (13%) with persistent SSPC after ablation. The ability to use loss of the marker (present before, absent after ablation) as a surrogate for successful ablation was greater for SSPC than for DAVNP (66% vs 36%, P = 0.001). CONCLUSION: SSPC is more common than DAVNP in young patients with AVNRT. SSPC is eliminated more frequently than DAVNP after acutely successful ablation, and appears to be a better indicator of the substrate for AVNRT. Elimination of SSPC may serve as a useful surrogate endpoint for slow pathway ablation.     

Meta-analysis to assess the appropriate endpoint for slow pathway ablation of atrioventricular nodal reentrant tachycardia

Background: There are little data on the appropriate endpoint for slow pathway ablation that balances acceptable procedural times, recurrence rates, and complication rates. This study compared recurrence rates of three commonly utilized endpoints of slow pathway ablation for atrioventricular nodal reentrant tachycardia (AVNRT). Methods: We performed a meta‐analysis of AVNRT slow pathway ablation cohorts by searching electronic databases, the Internet, and conference proceedings. Inclusion criteria were age >18 years, >20 human subjects per study, primary AVNRT ablation, English language publication, and >1 month of follow‐up. Data were analyzed with a fixed‐effects model using Comprehensive Meta‐Analysis software version 2.2.046 (Biostat, Englewood, NJ, USA). Results: We included 10 studies encompassing 1,204 patients with a mean age of 41–53 years. Endpoints were complete slow pathway ablation, residual jump only, and single remaining echo beat. Pooled estimates revealed 28 of 641 patients (4.4%) with complete slow pathway ablation, 13 of 192 patients (6.8%) with a residual jump only, and 24 of 371 patients (6.5%) with one echo had recurrences. With uniform isoproterenol use after ablation, there was no significant difference in recurrence rates among the endpoints. However, when isoproterenol was utilized after ablation only if needed to induce AVNRT before ablation, a significantly higher recurrence rate occurred in patients with a residual jump (P = 0.002), a single echo (P = 0.003), or the combined group of a residual jump and/or one echo (P = 0.001). Conclusions: Isoproterenol should be used routinely after slow pathway modification, when a residual jump and/or single echo remain. (PACE 2011; 34:269–277)     

Rapid atrial pacing: a useful technique during slow pathway ablation

BACKGROUND: Catheter ablation is the treatment of choice for atrioventricular nodal reentrant tachycardia (AVNRT) with a success rate of 95-98%. The appearance of junctional rhythm during radiofrequency (RF) application to the slow pathway has been consistently reported as a marker for the successful ablation of AVNRT. Ventriculoatrial (VA) conduction during junctional rhythm has been used by many as a surrogate marker of antegrade atrioventricular nodal (AVN) function. However, VA conduction may not be an accurate or consistent marker for antegrade AVN function and reliance on this marker may leave some patients at risk for antegrade AVN injury. OBJECTIVE: The purpose of this study is to describe a technique to ensure normal antegrade AVN function during junctional rhythm at the time of RF catheter ablation of the slow pathway. METHODS: Retrospective review of all patients less than 21 years old who underwent RF ablation for AVNRT at our institution from January 2002 to July 2005. During RF applications, immediately after junctional rhythm was demonstrated, RAP was performed to ensure normal antegrade AVN function. Postablation testing was performed to assess AVN function and tachycardia inducibility. RESULTS: Fifty-eight patients underwent RF ablation of AVNRT during the study period. The mean age +/- SD was 14 +/- 3 years (range: 5-20 years). The weight was 53 +/- 15 Kg (range: 19-89 Kg). The preablation Wenckebach cycle length was 397 +/- 99 msec (range: 260-700 msec). Fifty-four patients had inducible typical AVNRT, and four patients had atypical tachycardia. The mean tachycardia cycle length +/- SD was 323 +/- 62 msec (range: 200-500 msec). Patients underwent of 8 +/- 7 total RF applications (median: 7; range 1 to 34), for a total duration of 123 +/- 118 seconds (median: 78 sec, range: 20-473 sec). Junctional tachycardia was observed in 52 of 54 patients. RAP was initiated during junctional rhythm in all patients. No patient developed any degree of transient or permanent AVN block. Following ablation, the Wenckebach cycle length decreased to 364 +/- 65 msec (P < 0.01). Acutely successful RF catheter ablation was obtained in 56 of 58 patients (96%). CONCLUSION: Rapid atrial pacing during radiofrequency catheter ablation of the slow pathway is a safe alternative approach to ensure normal AVN function.     

房室折返性心动过速合并房室结双径路的射频消融治疗

目的:探讨房室折返性心动过速(AVRT)合并房室结双径路(AVNDP)的电生理特征和射频消融术式的选择。方法:对640例阵发性室上性心动过速(PSVT)进行电生理检查,观察PSVT发作时传导的顺序,然后进行消融治疗。结果:640例PSVT中检出AVRT AVNDP 68例,检出率为10.6%;有8例诱发房室结折返性心动过速,对此类患者进行慢径消融治疗。随访所有经治患者均无复发。结论:AVRT合并AVNDP者阻断房室旁道是消融成功的关键;房室旁道作为"旁观者"时也应作房室旁道消融;如仅有(AH)跳跃但无心动过速者无需接受房室结改良。     

Abnormal Atrioventricular Node Conduction and Atrioventricular Nodal Reentrant Tachycardia in Patients Older Versus Younger Than 65 Years of Age

Study Objective: We examined the possible role of atrioventricular node (AVN) conduction abnormalities as a cause of AVN reentrant tachycardia (RT) in patients >65 years of age.
Study Population: Slow pathway radiofrequency catheter ablation (RFCA) was performed in 104 patients. Patients in group 1 (n = 14) were >65 years of age and had AV conduction abnormalities associated with structural heart disease. Patients in group 2 (n = 90) were <65 years of age and had lone AVNRT.
Results: Patients in group 1 versus group 2 (66% vs. 46% men) had a first episode of tachycardia at an older age than in group 2 (68 ± 16.8 vs 32.5 ± 18.8 years, P = 0.007). The history of arrhythmia was shorter in group 1 (5.4 ± 3.8 vs 17.5 ± 14, P = 0.05) and was associated with a higher proportion of patients with underlying heart disease than in group 2 (79% vs 3%, P < 0.001). The electrophysiological measurements were significantly shorter in group 2: atrial-His interval (74 ± 17 vs 144 ± 44 ms, P = 0.005), His-ventricular (HV) interval (41 ± 5 vs 57 ± 7 ms, P = 0.001), Wenckebach cycle length (329 ± 38 vs 436 ± 90 ms, P = 0.001), slow pathway effective refractory period (268 ± 7 vs 344 ± 94 ms, P = 0.005), and tachycardia cycle length (332 ± 53 vs 426 ± 56 ms, P = 0.001). The ventriculoatrial block cycle length was similar in both groups. The immediate procedural success rate was 100% in both groups, and no complication was observed in either group. One patient in group 2 had recurrence of AVNRT. One patient with a 98-ms HV interval underwent permanent VVI pacemaker implantation before RFCA procedure.
Conclusion: In patients undergoing RFCA for AVNRT at >65 years of age had a shorter history of tachycardia-related symptoms than patients with lone AVNRT. The longer AVN conduction intervals and refractory period might explain the late development of AVNRT in group 1.     

Cryoablation for Presumed Atrioventricular Nodal Reentrant Tachycardia in Pediatric Patients

Background: Little data exist on the outcomes of cryoablation for the treatment of presumptive atrioventricular nodal reentrant tachycardia (AVNRT) in a pediatric population. Methods: We performed a retrospective chart review of patients undergoing cryoablation from January 2006 to October 2010 for presumed AVNRT at the Children's Hospital Colorado. Inclusion criteria were age ≤ 18, normal heart structure, no prior ablation procedures, documented narrow complex tachycardia, and no inducible tachycardia or other tachycardia mechanisms during electrophysiology study. Results: Thirteen patients underwent cryoablation for presumed AVNRT. Cryoablation catheter tip size varied from 4 to 8 mm with a median of eight cryoablation lesions. Isoproterenol was utilized preablation in 54% and none postablation. Procedural endpoints, per written report, were loss of sustained slow pathway, change in Wenckebach cycle length, and no specific endpoint. Procedural endpoints, per measured data, were a decrease in patients exhibiting sustained slow pathway conduction. Maximum atrial‐His (AH) interval with atrial overdrive pacing was reduced from 266 ms preablation to 167 ms postablation, p = 0.006. The number of patients with an AH jump was reduced from 6 to 2. After follow‐up of 13.8 ± 14.3 months, 23% (3/13) had documented tachycardia recurrence. No statistical significance was determined when comparing electrophysiology testing parameters pre‐ and postablation among the group with recurrence versus the group without recurrence. Conclusions: Cryoablation can be considered as a safe alternative to radiofrequency ablation for the treatment of presumed AVNRT among pediatric patients, albeit with a recurrence rate of 23%. (PACE 2012; 35:1319–1325)     

Relation between the AH interval and the ablation site in patients with atrioventricular nodal reentrant tachycardia

The determinants of slow pathway conduction in patients with AV nodal reentrant tachycardia (AVNRT) are still unknown, and great differences in the AH interval during slow pathway conduction are observed between patients. In 35 patients with typical AVNRT who underwent successful slow pathway ablation (defined as complete elimination of dual pathway physiology), the A2H2 interval at the "jump" during programmed atrial stimulation and the AH interval during AVNRT (as a reflection of slow pathway conduction time) and the fluoroscopic distance between the successful ablation site and the His-bundle recording site and between the coronary sinus ostium (CSO) and the His-bundle recording site were determined. The mean (+/- SEM) AH interval during slow pathway conduction was 323 +/- 12 ms with programmed stimulation and 310 +/- 10 ms during AVNRT. The mean number of energy applications was 8 +/- 1 (range 1-21). The mean distances between (1) the successful ablation site and the His bundle recording site and (2) between the CSO and the His-bundle recording site were 24 +/- 1 and 28 +/- 1 mm in the RAO and 23 +/- 1 and 28 +/- 1 mm in the LAO projections, respectively. The AH interval during slow pathway conduction correlated significantly with the distance between the successful ablation site and the His-bundle (P < 0.001) but not with the distance between CSO and His-bundle recording site. There is a significant correlation between the AH interval during slow pathway conduction and the distance of the successful ablation site from the His bundle. This relationship (1) suggests that, in addition to functional factors, anatomic factors influence slow pathway conduction and (2) may be helpful in determining the initial energy application site during slow pathway ablation.     

Successful Slow Pathway Ablation in a Patient with Atrioventricular Nodal Reentrant Tachycardia Having a Proximal Common Pathway

Radiofrequency catheter ablation was attempted in a patient with atrioventricular nodal reentrant tachycardia (AVNRT). AVNRT was easily inducible but an intermittent loss of the atrial activation was observed during AVNRT suggesting the presence of a proximal common pathway. During sinus rhythm, a relatively delayed activation that was compatible with a slow potential, was recorded anterior to the ostium of coronary sinus, and radiofrequency catheter ablation application (20 watts) to the site induced junction tachycardia. After an additional radiofrequency catheter ablation application to close the site, AVNRT became noninducible without deterioration of atrioventricular conduction through a fast pathway. This is the first case in which radiofrequency catheter ablation application to the slow potential recording site has been successful, even in AVNRT having a proximal common pathway.     

射频消融的延迟效应对手术效果及并发症的影响

目的 :探讨射频消融延迟效应对手术效果及并发症的影响。方法 :回顾分析 1998～ 2 0 0 2年住院的室上速 4例 ,年龄 15～ 4 5岁 ,男女各 2例 ,其中房室结折返性心动过速 (AVNRT) 2例 ,右侧显性预激 (B- WPW) 2例 ,射频消融均未成功 ,在消融过程中 2例 B- WPW出现短暂旁路前传消失 ,2例 AVNRT出现短暂快速交界性心律及一过性 度房室传导阻滞。结果 :2例 B- WPW术后 1个月复查心电图预激消失 ,2例 AVNRT分别于术后 3d和 1周出现持续 度房室传导阻滞和 度 型房室传导阻滞 ,经激素治疗后房室传导均恢复正常。所有患者术后均未再发作室上速。结论 :射频消融术后组织及电学损伤范围可进一步加大从而产生延迟现象 ,它可对患者有益也可产生不利影响 ,因此射频消融时要密切注意可能产生延迟反应的电生理现象。     

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.