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.     

Mechanisms of AV Node Reentrant Tachycardia in Young Patients With and Without Dual AV Node Physiology

Recent advances in electrophysiological mapping and radiofrequency catheter ablation have demonstrated the participation of perinodal atrial tissue or pathways in atrioventricular node reentrant tachycardia (AVNRT). Current concepts of the role of these pathways in the genesis of the various forms of AVNRT continue to evolve. In view of these recent advances, this study investigated the electrophysiology of AVNRT in young patients, and factors potentially associated with variant forms of this arrhythmia. Detailed programmed stimulation and catheter mapping were performed in 35 consecutive young patients with AVNRT. This group consisted of 15 male and 20 female patients, with a mean age of 12.1 ± 4.2 years (range 3–18 years). Of the 35 patients, 23 demonstrated dual AV node physiology, either in response to a critically timed extrastimulus (n = 17) or to rapid pacing (n = 6). The common form (antegrade slow-retrograde fast) of AVNHT was demonstrated in 21 of these 23 patients. Antegrade fast-retrograde slow (n = 1) and antegrade slow-retrograde slow (n = 1) forms of AVNRT were identified in the 2 other patients. In contrast, only 5 of the 12 patients who did not demonstrate dual AV node physiology had the common form of AVNRT (P = 0.03). Eive of these patients also had the slow-slow form of AVNRT, while 1 patient each had a fast-slow and fast-fast form of AVNRT. Patients with dual AV node physiology were older (14.2 ± 2.0 years) and more likely to be female (16 of 23) than patients in whom dual A V node physiology was not identified, where the mean age was 10.6 ± 4.2 years and only 4 of 12 patients were female (P = 0.02 for age and P = 0.07 for gender). These observations suggest that the physiology of AV node reentry may evolve as a function of age, with slow-fast AVNRT prevalent in adolescents. However, absence of dual AV node physiology should not preclude diagnosis of AVNRT in young patients with supraventricular tachycardia, in whom atypical forms of AVNRT may be common.     

Cryoablation versus Radiofrequency Ablation for Atrioventricular Nodal Reentrant Tachycardia: Patient Pain Perception and Operator Stress

Background: Cryoablation (CRYO) is an alternative to radiofrequency (RF) ablation in the treatment of atrioventricular nodal reentrant tachycardia (AVNRT). This study aims to evaluate the differences in patient pain perception and operator stress between CRYO and RF ablation in the treatment of AVNRT. Methods: Patients with supraventricular tachycardia underwent electrophysiology study. Twenty patients (eight males, age 46.5 ± 12.5 years) diagnosed with AVNRT were randomized to receive CRYO (11) with a 6‐mm‐tip catheter or RF (nine) with a 4‐mm‐tip catheter. Patients’ pain perception and operator stress were assessed with a visual analogue scale (VAS) from 0 to 10 at the end of procedure. Results: There was no significant difference in acute procedural success (CRYO 100% vs RF 89%, P = 0.257). There was no complication of permanent atrioventricular block in either group. The number of energy applications was significantly higher in the CRYO group (2.8 ± 1.2 vs 1.6 ± 0.9, P = 0.02). The fluoroscopic time was significantly reduced in the CRYO group (6.0 ± 4.9 vs 10.9 ± 5.4 minutes, P = 0.049) with no difference in procedure time (CRYO 49.3 ± 12.5 vs RF 54.5 ± 17.0 minutes, P = 0.462). Patients in the CRYO group experienced significantly less pain than patients in the RF group (VAS 2.3 ± 2.8 vs 5.4 ± 3.4, P = 0.024). The operator also experienced significantly less stress during CRYO than RF (VAS 1.9 ± 0.8 vs 6.2 ± 1.6, P < 0.001). There was no recurrence in both groups at 6‐month follow‐up. Conclusions: CRYO, as compared with RF, produces less pain in patients and less stress in operator in the treatment of AVNRT. (PACE 2011; 2–7)     

Modification of antegrade slow pathway is not crucial for successful catheter ablation of common atrioventricular nodal reentrant tachycardia

We tested the hypothesis that in some patients affected by typical AVNRT, successful catheter ablation treatment may be achieved independently of specific measurable electrophysiological modifications of antegrade AV node conducting properties. Standard electrophysiological parameters and comparable antegrade AV node function curves were obtained, before and after successful ablation, in 104 patients (mean age 52 +/- 16 years; 69 women and 35 men) affected by the common form of AVNRT. The end point of the ablation procedure was noninducibility of AVNRT and of no more than one echo beat. For the purpose of this study, AV node duality was defined as an increase of > or = 50 ms in the A2H2 interval in response to a 10 ms decrease of the A1A2 coupling interval. Before ablation, AV node duality was present in 65 patients (62%) and absent in 39 patients (37%). Ablation caused measurable modifications of electrophysiological properties of the AV node in most patients with elicited AV node duality, but not in most patients without demonstrable AV node duality. After ablation, AV node duality persisted in 20 patients who had it before, whereas a new duality that could not be elicited before appeared in 5 patients. During 19 +/- 6 months of follow-up, clinical AVNRT recurred in 1 of 45 patients who had disappearance of AV node duality after ablation, in 1 of 34 patients who did not show AV node duality before and after ablation, and in 1 of 20 patients who had persistence of AV node duality after ablation. In conclusion, modifications of antegrade conduction properties of the AV node are not crucial for the cure of AVNRT in many patients.     

The different ablation effects on atrioventricular nodal reentrant tachycardia in children with and without dual nodal pathways

BACKGROUND: Previous studies in adults have shown a significant shortening of the fast pathway effective refractory period (ERP) after successful slow pathway ablation. However, information on atrioventricular nodal reentrant tachycardia (AVNRT) in children is limited. The purpose of this retrospective study was to investigate the different effects of radiofrequency (RF) catheter ablation in pediatric AVNRT patients between those with and without dual atrioventricular (AV) nodal pathways. METHODS: From January 1992 to August 2004, a total 67 pediatric patients with AVNRT underwent an electrophysiologic study and RF catheter ablation at our institution. We compared the electrophysiologic characteristics between those obtained before and after ablation in the children with AVNRT with and without dual AV nodal pathways. RESULTS: Dual AV nodal pathways were found in 37 (55%) of 67 children, including 36 (54%) with antegrade and 10 (15%) with retrograde dual AV nodal pathways. The antegrade and retrograde fast pathway ERPs in children with dual AV nodal pathways were both longer than the antegrade and retrograde ERPs in children without dual AV nodal pathways (300 +/- 68 vs 264 +/- 58 ms, P = 0.004; 415 +/- 70 vs 250 +/- 45 ms, P < 0.001) before ablation. In children with antegrade dual AV nodal pathways, the antegrade fast pathway ERP decreased from 300 +/- 68 ms to 258 +/- 62 ms (P = 0.008). The retrograde fast pathway ERP also decreased after successful ablation in the children with retrograde dual AV nodal pathways (415 +/- 70 vs. 358 +/- 72 ms, P = 0.026). CONCLUSION: The dual AV nodal physiology could not be commonly demonstrated in pediatric patients with inducible AVNRT. After a successful slow pathway ablation, the fast pathway ERP shortened significantly in the children with dual AV nodal pathways.     

Linear Lesion Cryoablation for the Treatment of Atrioventricular Nodal Re‐entry Tachycardia in Pediatrics and Young Adults

Background: Radiofrequency (RF) ablation is a relatively safe and effective method for treatment of atrioventricular nodal re‐entry tachycardia (AVNRT), but carries a 1–2% risk of AV nodal injury. Cryothermal ablation reduces the risk of AV block, but has had decreased procedural success and increased recurrence of tachycardia. We sought to evaluate the technique of linear lesion cryoablation (LLC) for treatment of AVNRT. Methods: Single institution retrospective cohort study. Each patient underwent slow pathway modification using either RF, single lesion cryoablation, or LLC. Procedural success, recurrence, freedom from tachycardia 12 months following ablation and fluoroscopy time were compared between ablation methods. Results: A total of 125 patients, median age 15.5 (4.7–23.1) years, underwent ablation: 32 RF energy, 31 single lesion cryoablation, 62 LLC. Procedural success was obtained in 94% of the LLC group compared to 58% using single lesion cryoablation (P ≤ 0.001). Ninety‐seven percent of the LLC group was free from tachycardia recurrence, significantly higher than with single lesion cryoablation (68%, P = 0.001) and equal to that of RF (97%, P = NS). Fluoroscopy time was reduced in the LLC group compared to both single lesion and RF groups (P = 0.02). There was no permanent AV nodal injury in the cryoablation groups. Conclusion: LLC is an effective means of treatment for AVNRT and is associated with significantly improved procedural success and freedom from recurrence compared to single lesion methods, while at the same time obtaining equivalent efficacy to RF. (PACE 2010; 1304–1311)     

Cryoablation of Typical Atrioventricular Nodal Reentrant Tachycardia in Children: Six Years’ Experience and Follow‐Up in a Single Center

Background: Cryoablation is an effective and safe treatment for children with supraventricular tachycardias when the reentry circuit is located near the atrioventricular (AV) junction. We retrospectively reviewed consecutive cryoablation procedures for the treatment of atrioventricular nodal reentrant tachycardia (AVNRT) in children and young adults in a single pediatric center. Methods: From October 2002 to October 2008, cryoablation was attempted in 76 pediatric patients (mean age 11.3 ± 2.4 years, range: 6–16.4 years) with symptomatic typical AVNRT. Cryomapping, used to identify the tissue site for safe arrhythmia ablation, was performed at ?30°C for a maximum of 60 seconds. The efficacy of the cryomapping procedure was assessed in terms of disappearance of dual‐AV node physiology and noninducibility of AVNRT. Results: Cryoablations were from 4 to 8 minutes long at ?75°C. A single “bonus” cryoapplication (?75°C for minimum 6 minutes) was delivered to consolidate the acutely successful cryoablation for 64 consecutive patients. After the cryoablation procedure, patients were assessed at 1, 3, 6, 12, 18, and 24 months (and then every year thereafter) by a clinical evaluation and standard electrocardiogram, Holter monitoring, and exercise stress testing. No permanent cryo‐related complications were reported. Seventy‐four (97.4%) patients were successfully acutely ablated. During a mean follow‐up of 29.5 months (range 2–74 months), five (6.8%) acutely successful pediatric patients experienced arrhythmia recurrence. We did not identify any predictive factors of AVNRT recurrence. Conclusions: Acute and long‐term results demonstrate that cryoablation of AVNRT can be considered a safe and effective procedure in pediatric patients. (PACE 2010; 475–481)     

The results of radiofrequency catheter ablation of supraventricular tachycardia in children

BACKGROUNDS: Radiofrequency (RF) catheter ablation represents a major advance in the management of children with cardiac arrhythmias and has rapidly become the standard of care for the first-ling therapy of supraventricular tachycardias (SVTs). The purpose of this study was to investigate the results of the RF catheter ablation of SVTs in pediatric patients. METHODS: From December 1989 to August 2005, a total of 228 pediatric patients (age: 9 +/- 7 years, range: 5-18 years; male:female = 117:111) with clinically documented SVT underwent an electrophysiologic study and RF catheter ablation at our institution. RESULTS: The arrhythmias included atrioventricular reentrant tachycardia (AVRT; n = 140, 61%), atrioventricular nodal reentrant tachycardia (AVNRT; n = 66, 29%), atrial tachycardia (AT; n = 11, 5%), and atrial flutter (AFL; n = 11, 5%). The success rate of the RF catheter ablation was 92% for AVRT, 97% for AVNRT, 82% for AT, and 91% for AFL, respectively. Procedure-related complications were infrequent (8.7%; major complications: high grade AV block (2/231, 0.9%); minor complications: first degree AV block (6/231, 2.6%), reversible brachial plexus injury (2/231, 0.9%), and local hematomas or bruises (10/231, 4.3%)). The recurrence rate was 4.7% (10/212) during a follow-up period of 86 +/- 38 months (0.5-185 months). CONCLUSIONS: The RF catheter ablation was a safe and effective method to manage children with paroxysmal and incessant tachycardia. The substrates of the arrhythmias differed between the pediatric and adult patients. However, the success rate of the ablation, complications, and recurrence during childhood were similar to those of adults.     

Ten Year Follow-Up After Radiofrequency Catheter Ablation for Atrioventricular Nodal Reentrant Tachycardia in the Early Days Forever Cured,or a Source for New Arrhythmias?

BACKGROUND: Radiofrequency (RF) catheter ablation is highly effective with a low complication rate. However, lesions created by RF energy are irreversible, inhomogeneous, and therefore potentially proarrhythmic. OBJECTIVES: The aim of this study was to examine the magnitude and importance of long-term proarrhythmic effects of RF energy. METHODS AND RESULTS: Between 1991 and 1995, 120 patients underwent RF ablation for atrioventricular nodal reentrant tachycardia (AVNRT). Patient data were collected by contacting patients and/or filling out a questionnaire, and medical files were screened for recurrent, documented arrhythmias, pharmacological treatment, and repeated EP study. Referring cardiologists were asked about recurrences of tachyarrhythmias. Fourteen patients (11%) were lost to follow-up. During a mean follow-up of 10 years, six patients died. Recurrences of AVNRT were not any more observed after 3 years after ablation. A total of 29 patients (24%) suffered from new arrhythmias, 6 from type 1 atrial flutter, 6 from atrial tachycardia, 9 from atrial fibrillation, and finally 16 from symptomatic premature atrial contractions (PACs), needing medical treatment or a combination of these arrhythmias. Nine patients underwent pacemaker implantation, 4 after developing procedural atrioventricular (AV) conduction disturbances, 2 after His ablation for permanent atrial fibrillation, 1 patient for sick sinus syndrome, and another 2 patients after developing late AV block, respectively, 7 and 9 years after ablation. CONCLUSION: During long-term follow-up after RF ablation for AVNRT, no AVNRT recurrences were observed, but 29 patients (24%) suffered from new arrhythmias or late AV block. This potential proarrhythmic effect of RF energy promotes the application of alternative energy sources for ablative therapies for cardiac arrhythmias.     

Spontaneous Accelerated Junctional Rhythm: An Unusual but Useful Observation Prior to Radiofrequency Catheter Ablation for Atrioventricular Node Reentrant Tachycardia in Young Patients

Between May 1990 and March 1995, 5 of 29 young patients (ages 4.2–25 years; median 14.1 years) undergoing RF ablation for atrioventricular node reentrant tachycardia (AVNRT) presented with spontaneous accelerated junctional rhythm (AJR) (CL = 500–750 ms), compared to 0 of 58 age matched controls undergoing RF ablation for a concealed AV accessory pathway (P = 0.004). In 3 of the 5 patients with AVNRT and AJR, junctional beats served as a trigger for reentry. During attempted slow pathway modification in the five patients with AVNRT and AJR, AVNRT continued to be inducible until the AJR was entirely eliminated or dramatically slowed. These 5 patients are tachycardia-free in followup (median 15 months; range 6–31 months) with only 1 of the 5 patients continuing to experience episodic AJR at rates slower than observed preablation. Episodic spontaneous AJR is statistically associated with AVNRT in young patients and can serve as a trigger for reentry. Successful modification of slow pathway conduction may be predicted by the elimination of AJR or its modulation to slower rates, suggesting that the rhythm is secondary to enhanced automaticity arising near or within the slow pathway.     

A higher than expected prevalence of AV nodal reentrant tachycardia in patients receiving implantable cardioverter-defibrillators

Background: Epidemiologic studies have indicated that the prevalence of paroxysmal supraventricular tachycardia (SVT) is approximately two to three of 1000 persons, of whom 50–60% have atrioventricular node reentrant tachycardia (AVNRT). Although SVT has been reported to account for a significant portion of inappropriate shocks in patients receiving implantable cardioverter‐defibrillators (ICDs), the incidence of AVNRT is unknown. Objective: To define the incidence of AVNRT in patients with ICDs. Methods and Results: Of 426 patients followed with an ICD, 15 patients with AVNRT were identified (3.5%). AVNRT was noted preimplant in eight patients. One had remote AVNRT and had undergone radiofrequency (RF) ablation several years prior to ICD implantation. Three patients had known episodes and underwent RF ablation prior to ICD implant. Four had AVNRT induced at preimplant electrophysiology study and three had RF ablation prior to ICD implant. Seven patients had clinical episodes of AVNRT after ICD implant and six of seven received inappropriate ICD therapy for AVNRT. All seven patients underwent RF ablation for treatment of AVNRT. No patient who underwent RF ablation had further clinical episodes of SVT, and only one had further inappropriate ICD therapy for sinus tachycardia. Conclusion: The substantially higher prevalence of AVNRT in our followed ICD population (3.5%) compared to the general population may be due to detection bias or electroanatomic changes in the atrioventricular nodal area induced by the accompanying heart disease. In any case, further studies to evaluate the inducibility of AVNRT prior to ICD implant, its prognostic implications, and the role of RF ablation to prevent inappropriate shocks are warranted. (PACE 2011; 34:584–586)     

Is Vagal Innervation to the Atrioventricular Node Impaired After Radiofrequency Ablation of the Slow Atrioventricular Nodal Pathway?

To assess the potentially adverse effects of RF catheter ablation (RFCA) of the slow AV nodal pathway on the parasympathetic innervation to the AV node in patients with AV nodal reentrant tachycardia (AVNRT), AV nodal conduction was evaluated following vagal stimulation by means of a phenylephrine bolus injection (200 μg) before and after RFCA in ten patients (mean age, 37 ± 14 years). Nine patients with AV reentrant tachycardia (AVRT) due to a left free wall accessory pathway served as a control group (mean age of 37 ± 12 years). Whereas no prolongation of the AH interval was observed in the AVNRT group following the phenylephrine bolus during sinus rhythm, despite a significant slowing in sinus rate, phenylephrine administration in AVRT patients was associated with both slowing of the sinus rate and prolongation of the AH interval. Following successful RFCA, the same responses were observed. To delineate the indirect effect of heart rate on AV conduction in response to the phenylephrine bolus, the AH interval was also measured during fixed atrial pacing. A marked prolongation of the AH interval occurred in both groups following phenylephrine administration. This prolongation was biphasic in 50% of A VNRT patients before ablation, suggesting a predominant effect of vagal stimulation on the fast AV nodal pathway. RFCA was associated with disappearance of discontinuous AV conduction in all but one patient with AVNRT. Vagal stimulation caused the same amount of AH interval prolongation as before RFCA in both study groups. In conclusion, patients with AVNRT have a preserved modulation of AV nodal conduction in response to vagal stimulation during sinus rhythm. In addition, vagal stimulation seems to exert a predominant effect on the fast A V nodal pathway. RFCA of the slow AV nodal pathway in patients with A VNRT does not cause detectable damage to the vagal innervation to the AV node.     

Radiofrequency Catheter Ablation for AV Nodal Reentrant Tachycardia Associated with Persistent Left Superior Vena Cava

Slow A V nodal pathway ablation using RF is highly effective for patients with refractory A V nodal reentrant tachycardia (AVNRT). We report three catheter ablation cases using RF current in patients associated with persistent left superior vena cava (PLSVC). Three patients with drug refractory AVNHT of common variety were involved in this study. An electrode catheter introduced through the left subclavian vein inserted directly into the coronary sinus, a typical anatomical finding of PLSVC. The ablation procedure was initially performed at the posteroinferior region of Koch's triangle. A slow pathway potential could not be found from that area; nonsustained junctional tachycardia (NSJT) did not occur during the delivery of RF current; there was failure to eliminate slow AV nodal pathway conduction. The catheter then was moved into the bed of the proximal portion of the markedly enlarged coronary sinus. A slow AV nodal pathway potential was recorded through the ablation catheter, and the delivery of RF current caused NSJT in two patients. Complete elimination of slow AV nodal pathway conduction was accomplished in these two patients by this method. No adverse effects were provoked by this procedure. Catheter ablation of the slow A V nodal pathway guided by a slow pathway potential and the appearance of NSJT was feasible and safe in the area of the coronary sinus ostium in patients associated with PLSVC.     

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.     

Cryoablation with an 8‐mm Tip Catheter for Pediatric Atrioventricular Nodal Reentrant Tachycardia Is Safe and Efficacious with a Low Incidence of Recurrence

Background: Cryoablation with 4‐ and 6‐mm tip ablation catheters has been demonstrated to be safe and effective in the treatment of atrioventricular nodal reentrant tachycardia (AVNRT) in pediatric patients, albeit with a higher rate of clinical recurrence. Limited information is available regarding efficacy, mid‐term outcomes, and complications related to the use of the 8‐mm Freezor Max Cryoablation catheter (Medtronic, Minneapolis, MN, USA) in pediatric patients. Methods: We performed a retrospective review of all pediatric patients with normal cardiac anatomy who underwent an ablation procedure for treatment of AVNRT using the 8‐mm tip Cryoablation catheter at three large pediatric academic arrhythmia centers. Results: Cryoablation with an 8‐mm tip catheter was performed in 77 patients for treatment of AVNRT (female n = 40 [52%], age 14.8 ± 2.2 years, weight 62.0 ± 13.9 kg). Initial procedural success was achieved in 69 patients (69/76, 91%). Transient second‐ or third‐degree atrioventricular (AV) block was noted in five patients (6.5%). There was no permanent AV block. Of the patients successfully ablated with Cryotherapy, there were two recurrences (2/70, 2.8%) over a follow‐up of 11.6 ± 3.3 months. Conclusion: Cryoablation with an 8‐mm tip ablation catheter is both safe and effective with a low risk of recurrence for the treatment of AVNRT in pediatric patients. (PACE 2010; 33:681–686)     

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.     

Radiofrequency and cryoablation therapies for supraventricular arrhythmias in the young: five-year review of efficacies

Background: Cryoablation (Cryo) has augmented radiofrequency (RF) as the ablation energy choice for most supraventricular tachycardias (SVT). Although initial acute results and more recent, but limited, 3–36‐month follow‐up studies have been reported, more longer follow‐up information is required to determine actual efficacy. Methods: Data from patients with structurally normal hearts who underwent reentrant forms of SVT ablation at our institution from January 2005 to December 2009 were reviewed. These included demographics, clinical and electrophysiologic findings, and ablative energies used. Following apparent acute success, all patients were then reevaluated for any potential recurrences of SVT or preexcitation up to 5 years later. Results: A total of 155 patients (83 male) were reviewed (mean age 13.4 ± 3.7 years). Ablations were predominantly right‐sided (75%). Atrioventricular reciprocating tachycardia was seen in 74% and atrioventricular node reciprocating tachycardia (AVNRT) in 17% of patients. For concerns of atrioventricular node integrity, Cryo ± RF was user‐preferred for anteroseptal accessory fiber locations and AVNRT. Acute success rate was 98% and chronic 83.2% over the next 5 years. Among patients with accessory pathways, recurrence was pathway number and location dependent: significantly higher (P < 0.05) if they were right anterior‐anteroseptal, multiple, or with a broad‐distribution pattern. There were no significant differences in recurrence rates with use of RF or its combination with Cryo. Conclusion: Radiofrequency ablation and Cryo are both effective therapies for pediatric patients. Although use of Cryo with RF in combination may enhance safety while affording comparable success, risk of recurrence still persists in the current era among patients depending on accessory pathways connection location and characteristics. (PACE 2012; 35:711–717)     

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)     

The history of AV nodal reentry

Though patients with AV nodal reentry are now routinely cured by catheter ablation, the basic mechanism of this disorder is still under debate. The putative mechanism of AV node reentry was first discovered by the elegant work of Gordon Moe. He demonstrated the existence of dual pathways and echo beats in rabbits. Building on these seminal observations, the mechanism of AVNRT has burgeoned to include the possibility of left atrial input into the node. The first curative nonpharmacologic procedures involved surgical dissection around the AV node and the procedure was rapidly supplanted by catheter ablation procedures. The initial ablative procedure targeted the fast pathway, but later observations showed that ablation of the slow pathway was more effective and safer. Cure of AV nodal reentry which is the most common cause of paroxysmal supraventricular tachycardia became possible through the cooperative efforts of anatomists, physiologists, surgeons, and clinical electrophysiologists.     

Radiofrequency Catheter Ablation for AV Nodal Reentry: A Technique for Rapid Transection of the Slow AV Nodal Pathway

Selective radiofrequency (RF) catheter ablation of the slow AV nodal puthway has shed new light on the anatomy and physiology of the atrioventricular junction. The recording of “slow pathway potentials” facilitates localization of the slow pathway and has led to a concept of multiple pathway components with atrial insertion sites covering a potentially broad region surrounding the coronary sinus os. The critical area for complete interruption of the slow pathway may be larger than lesion size produced by ablation at a single site, resulting in multiple RF applications with lengthy sessions and prolonged radiation exposure. Information from both old and recent literature suggests that the slow AV nodal pathway is represented by a group of fibers originating from the posteroinferior interatrial septum and coursing anterosuperiorly near the tricuspid annulus before converging upon the compact AV node. Based on this anatomical arrangement, the present study was conducted to evaluate a technique designed to transect the slow pathway by producing a linear RF lesion perpendicular to the orientation of the slow pathway within the mid-portion of Koch's triangle. Using this technique, 30 of 30 patients with common AV nodal reentry ivere rendered noninducible using 1 to 3 RF applications. Total procedure time averaged 3.4 ± 1.1 hours and fluoroscopy time averaged 14.8 ± 4.6 minutes. As a marker of efficacy, episodic nonsustained atrial tachycardia (NSAT) during RF delivery occurred in 28 of 30 (93%) successful applications. Three patients experienced tachycardia recurrence and were successfully ablated by repeat procedure. Conduction characteristics and refractoriness of the fast pathway were unchanged in 23 of 23 patients reevaluated at a mean of 7.2 weeks postablation. Two of 30 (6%) patients experienced procedure related complications but there were no instances of AV block. We conclude that the technique of producing a linear lesion by continuous migratory RF application in the manner described safely and effectively eliminates AV nodal reentry, simplifies the procedure, and minimizes radiation exposure to the patient and the physician.