Identifying an appropriate endpoint for cryoablation in children with atrioventricular nodal reentrant tachycardia: Is residual slow pathway conduction associated with recurrence?

BACKGROUND

Cryoablation is increasingly used to treat atrioventricular nodal reentrant tachycardia (AVNRT) due to its safety profile. However, cryoablation may have higher recurrence than radiofrequency ablation (RFA), and the optimal procedural endpoint remains undefined.

OBJECTIVE

The purpose of this study was to identify the association of cryoablation procedural endpoints with postprocedural AVNRT recurrence.

METHODS

We performed a single-center, retrospective analysis of pediatric patients following successful first-time cryoablation for AVNRT between January 1, 2011, and December 31, 2019. Preablation inducibility of AVNRT was recorded. Procedural endpoints, including slow pathway (SP) conduction (presence of jump or echo beats) with and without isoproterenol, were identified. Recurrence was established from clinical notes and/or direct patient contact.

RESULTS

Of 256 patients, 147 (57%) were assessed on isoproterenol precryoablation, and 171 (47%) were assessed on isoproterenol postcryoablation. Mean cryolesion time was 2586 ± 1434 seconds. Following ablation, 104 (41%) had some evidence of residual SP conduction. With median follow-up time of 1.9 [0.7-3.7] years, recurrence occurred in 14 patients (5%). Complete elimination of SP conduction (with and without isoproterenol) had a hazard ratio for recurrence of 1.26 (95% confidence interval [CI] 0.42-3.8; P = .68) on univariate analysis and 1.39 (95% CI 0.36-5.4; P = .63) on multivariate analysis (including demographics, ablation time, 8-mm cryocatheter, and baseline inducibility).

CONCLUSION

The observed AVNRT recurrence rate after cryoablation was comparable to that of RFA. The presence of residual SP conduction was not associated with recurrence. This suggests that jump or single echo beat may be an acceptable endpoint in AVNRT cryoablation.

Transcatheter cryo-ablation of septal accessory pathways, multicenter observational study in Japan

BACKGROUND

Ablation using radiofrequency energy has to be carefully performed when the arrhythmia substrate is located in close proximity to the atrioventricular (AV) node due to the risk of inadvertent permanent AV block. The aim of this study was to evaluate the efficacy and safety of catheter-based cryo-therapy for septal accessory pathways (APs).

METHODS

A total of eleven patients (median = 56.3 years, range 13-74 years) with septal APs underwent cryoablation. Ice-mapping was performed during sinus rhythm and an AV reciprocating tachycardia utilizing the APs as a requisite limb with cooling of the catheter tip temperature to a maximum of -30℃ for less than 45 s. Cryo-ablation was performed for 4 min at a temperature of -80℃ only if ice-mapping abolished the pre-excitation or retrograde conduction over the AP without injury to the AV nodal conduction.

RESULTS

Cryo-ablation was acutely successful in all eleven patients. No permanent cryo-related complications or adverse outcomes were reported. During the follow-up (range 14-26 months), no patients experienced any arrhythmia recurrences.

CONCLUSION

Ice-mapping was a feasible and reliable method to determine the exact location of the APs owing to the possibility of validating the ablation site. Cryo-ablation of APs located near the AV junction is a safe and efficacious technique with a high success rate over the long term.

IRB INFORMATION

Ethical Committee of Japan Red Cross Yokohama City Bay Hospital #2018-19.

Cryoablation with an 8-mm tip catheter for typical AVNRT in children: a single center 5-year experience

BACKGROUND

In children with typical atrioventricular nodal reentrant tachycardia (tAVNRT), cryoablation is preferred over radiofrequency ablation (RFA) because of its safety profile and acceptable long-term success rates. In this study, we have assessed the utility of 8-mm tip cryocatheters for tAVNRT ablation in our center.

METHODS

All pediatric AVNRT patients who underwent cryoablation with an 8-mm tip cryocatheter in our center between 2013 and 2018 were included. EnSite™ (St. Jude Medical Inc., St. Paul, MN, USA) was used in all patients.

RESULTS

A total of 120 patients (64 females, 53%) were included in this study, and the mean age was 13.9 years with a standard deviation of 2.5 years. Eleven patients (9.1%) had structural heart disease, and 12 patients (10%) had additional arrhythmia substrate. The mean number of effective cryolesions was 8 with a standard deviation of 2.3. Fluoroscopy was used in three patients (2.5%). There were minor complications in only four patients (3.3%)-transient first-degree atrioventricular block or transient incomplete right bundle branch block. Acute success rate of cryoablation was 108/120 (90%). In twelve patients, cryoablation was suboptimal, or it failed. The procedure was completed successfully with RFA in the same session in ten patients. Overall acute success rate of ablation (Cryo ± RFA) was 98.5%. During a mean follow-up period of 24.6 months with a standard deviation of 11.3 months, three patients had recurrence (2.5%). Time between the beginning of the effective cryolesion and termination of AVNRT was found associated with acute success of cryoablation (p = 0.013).

CONCLUSIONS

Cryoablation of AVNRT with an 8-mm tip catheter in children appears to be safe, with an acceptable acute success rate and a low recurrence rate. A faster termination of AVNRT during the cryolesion, slowing down before ending with atrioventricular block, is a good indicator for acute success.

Cryofreezing catheter ablation of adenosine triphosphate sensitive atrial tachycardia

INTRODUCTION

Adenosine triphosphate (ATP) sensitive atrial tachycardia (AT) has been treated by radiofrequency catheter ablation. Cryofreezing energy has emerged as a novel energy source for catheter ablation. The aim of this study was to investigate the efficacy and safety of cryofreezing ablation for ATP-sensitive AT.

METHODS AND RESULTS

A total of six patients with ATP-sensitive ATs were included in this study. A single atrial extrastimulation was able to initiate and terminate these ATs in all six patients. The electrophysiological findings satisfied the diagnostic criteria of ATP-sensitive AT. The ablation catheter was located at the earliest activation site of atrial excitation during the AT, and cryofreezing energy was delivered through a cryoablation catheter to perform cryomapping at temperature of -30 or -80°C. When cryomapping successfully terminated the ATs, cryoablation at a temperature of -80°C was subsequently performed. The earliest atrial activation during AT was recorded at the Koch's triangle area associated with a distinct intra-atrial activation sequence from that recorded during ventricular pacing. Cryoablation was performed at successful cryomapping sites and resulted in the complete elimination of the AT in all six patients without affecting the bidirectional atrioventricular (AV) nodal conduction.

CONCLUSION

Cryofreezing energy was safe and effective in treating ATP-sensitive ATs even in patients with its origins located in the vicinity of the AV node.

Cryoablation of atrioventricular nodal re-entrant tachycardia: 7-year follow-up in 515 patients-confirmed safety but very late recurrences occur

Aims

Cryoablation is an alternative method to radiofrequency ablation for treatment of atrioventricular nodal re-entrant tachycardia (AVNRT). This study investigates the long-term safety and efficacy of cryoablation in AVNRT.

Methods and results

We studied 515 consecutive patients (317 women, mean age 50 years, range 13-89 years) undergoing a first cryoablation for AVNRT between 2003 and 2008. Ablations were performed with a 6-mm Freezor Xtra catheter. Six patients were acute failures; 494 out of 509 (97%) primarily successfully ablated patients were followed up for a mean of 7.1 years (range 2-12 years). About 11% (54/494 patients) of patients had recurrences of the index arrhythmia. Time to recurrence varied from days to 9 years; 14 patients (3%) had recurrences later than 2 years, 8 patients (2%) later than 3 years, and 6 patients (2%) later than 4 years. Recurrence rate was higher in patients with slow-slow or fast-slow AVNRT (n = 24) compared with the common slow-fast variant (25 vs. 10%; P = 0.04). Recurrence rate was not higher in patients with residual slow pathway conduction (jump with or without echo beat, n = 199, 39%). Transient atrioventricular (AV) block of the first-, second-, or third-degree during ablation was observed in 45 patients but had no impact on the risk of AVNRT recurrence. No late AV block occurred. Single vs. multiple applications or total amount of cryoenergy delivered did not differ between patients with and without recurrences.

Conclusion

Cryoablation in AVNRT is safe with a long-term efficacy of 88%; however, very late recurrences occur.

How to Approach Difficult Cases of AVNRT

OPINION STATEMENT

Our approach to the ablation of atrioventricular nodal reciprocating tachycardia (AVNRT), the most common supraventricular tachycardia, is as follows: We first attempt ablation in the right atrial posteroseptum anterior to the coronary sinus ostium with a 4-mm non-irrigated tip catheter. If ablation within the triangle of Koch is unsuccessful with radiofrequency (RF), we switch to cryoablation and target a more superior (mid septal) region. We also utilize cryoablation if RF ablation produces transient VA block (absence of retrograde conduction during junctional rhythm) or a fast junctional rhythm (<350 msec). If cryoablation were to fail, or is not available, we would then suggest ablation within the coronary sinus targeting the roof (2-4 cm from the os) using a 3.5-mm irrigated tip catheter. If tachycardia were still inducible despite these measures, we would then proceed with transseptal puncture (given our greater experience with this over a retrograde aortic approach) and perform RF ablation along the posteroseptal left atrium and inferoseptal mitral annulus utilizing an irrigated tip catheter. In our experience, cryoablation reliably results in elimination of the slow pathway. The only left atrial ablation for AVNRT at our institution in the past year was performed because a patent foramen ovale allowed for rapid left atrial access, facilitating left atrial ablation of the slow pathway.

[Cryoablation: Clinical applications in cardiac electrophysiology from their biophysical bases]

Cryoablation is an energy alternative to radiofrequency for ablation of various arrhythmias, where its unique biophysical properties offer a greater safety profile. Since its first use for the surgical treatment of different arrhythmias until its conceptualization in the current technical transcatheter, cryoablation has proven not to be only a safe source of energy, but also an effective source in the long-term. While the radiofrequency has been the energy most used for isolation of pulmonary veins in atrial fibrillation ablation, technological advances in cryoballon have managed to simplify the procedure without sacrificing its effectiveness. Cryoablation has been widely used for arrhythmias located in high-risk locations, such as the ablation of the atrioventricular nodal reentrant tachycardia and septal accessory pathways, due to its theoretical null risk of complete AV block. This review intends to give the clinical applications of the cryothermy through a thorough understanding of their biophysical basis.

Cryoablation therapy for atrioventricular nodal reentrant tachycardia in children: a multicenter experience of efficacy

Atrioventricular nodal reentrant tachycardia (AVNRT), a common tachycardia in children, is routinely treated by catheter ablation using radiofrequency or cryothermal energy. Acute success rates of 95-97 % are reported for cryoablation, similar to those achieved with radiofrequency ablation (RFA). However, early studies reported higher recurrence rates after cryoablation for treatment of AVNRT than those reported for RFA. This study evaluated the success and recurrence rates for cryoablation in a current cohort of pediatric patients across several institutions. Patients 21 years old or younger with AVNRT who underwent cryoablation at five participating centers between 2004 and 2009 were retrospectively reviewed. Patient demographics and procedural data were extracted from patient records and analyzed. A total of 434 patients with AVNRT who underwent cryoablation were identified. Cryoablation was used as the exclusive ablation method for 379 patients. For 97 % (368/379) of these patients, cryoablation was acutely successful. A higher acute success rate was found with the 6-mm-tip catheter (99 %) than with the 4-mm-tip catheter (91 %) (p < 0.01). Recurrence was experienced by 7.3 % of the patients. Recurrence was more likely for those treated with the 4-mm-tip catheter (6/42, 14 %) than for those who had the larger catheters (12/204, 6 %) No patient experienced permanent heart block. Success and recurrence rates for this cohort of patients were similar to those reported for RFA used to treat AVNRT in pediatric patients. The findings show a higher success rate and a lower recurrence rate after cryoablation with a 6-mm-tip catheter than after use of the 4-mm-tip catheter, with an associated excellent safety profile.

Post-ablation prolongation of atrioventricular nodal refractory period is correlated with long-term success of cryoablation for atrioventricular nodal reentrant tachycardia in the case of the persistence of a residual jump

PURPOSE

A residual slow pathway after successful cryoablation for atrioventricular nodal reentrant tachycardia (AVNRT) is correlated with a higher recurrence rate. We described determinants of recurrence in subjects with a residual jump.

METHODS

We analyzed the data of subjects with acute successful slow pathway cryoablation for AVNRT using a 6-mm-tip cryocatheter. Success was defined as AVNRT non-inducibility. Patients with no baseline elicitable jump, no inducible AVNRT, and transient first atrioventricular (AV) block at the last site were excluded.

RESULTS

From 371 patients who underwent cryoablation from May 2002 to March 2011, 303 fulfilled the entry criteria (mean age, 41 ± 16; 222 women). Baseline AV nodal effective refractory period (ERP) was 272 ± 57 ms, postprocedural 331 ± 64 (P < 0.001), and the mean of the difference (Δ ERP) 60 ± 41. At the end of the procedure, 64 patients (21 %) had a residual jump, of whom 22 with a single echo. At 12 months follow-up, the actuarial recurrence-free rate was 70.3 % in patients with a residual jump and 86 % in those without (P = 0.01). In patients with a jump, only Δ AV nodal ERP was correlated with recurrence (37 ± 41 vs. 68 ± 47 ms; P < 0.04) while a single echo was not. The actuarial rate of recurrence was 60.8 % in patients with a Δ AV nodal ERP ≤ 30 ms and 18.8 % in those with a Δ AV nodal ERP >30 ms (P < 0.01).

CONCLUSIONS

Suppression of slow pathway conduction is the optimal endpoint for AVNRT cryoablation. A residual jump can be tolerated if AV nodal ERP postcryoablation is prolonged >30 ms.