Low Recurrence Rate in Treating Atrioventricular Nodal Reentrant Tachycardia with Triple Freeze-Thaw Cycles

Transcatheter ablation of atrioventricular nodal reentry tachycardia in children and congenital heart disease in the era of 3D mapping

Atrioventricular nodal reentrant tachycardia (AVNRT) is a common supraventricular tachycardia in children and congenital heart disease (CHD) patients. Nowadays, in large enough children, chronic treatment for symptomatic and recurrent AVNRT episodes relies on transcatheter ablation. Indeed, many three-dimensional (3D) mapping strategies and ablation techniques have been developed and it helped to increase success rates and to reduce complications. Therefore, this study aimed to perform an updated comprehensive review of the available literature regarding contemporary management of AVNRT in children. A literature search was performed using Google Scholar, PubMed, Springer, Ovid, and Science Direct. We found that in recent times many investigations have demonstrated that 3D mapping systems allow to localize more precisely the ablation substrate, with minimal use of fluoroscopy. The most frequently employed mapping strategies are the low-voltage bridge strategy together with the search for the SP potential and the Sinus Rhythm Propagation Map with the identification of areas of Wave Collision or Pivot Points. For transcatheter ablation in pediatric settings, radiofrequency (RF) ablation was first used in the 1990s, while cryoablation was introduced in 2003 and nowadays represents the most used energy for AVNRT ablation in this population. Indeed, its specific features, such as reversible cryomapping, cryoadhesion and the precision in lesion delivery, made this technique very appealing to decrease complications and fluoroscopy time. As regards AVNRT in CHD patients, it represents the third most common form of arrhythmia in children with CHD. However, in this subgroup ablation remains challenging and experience limited, since anatomy may be atypical and the areas of ablation less predictable or less accessible.

Zero-Fluoroscopy Catheter Ablation of Supraventricular Tachycardias in the Pediatric Population

Catheter ablation (CA) of supraventricular tachycardias (SVTs) is conventionally performed with the aid of X-ray fluoroscopy. Usage of a three-dimensional (3D) electro-anatomical mapping (EAM) system and intracardiac echocardiography (ICE) enables zero-fluoroscopy ablation, eliminating the harmful effects of radiation. We retrospectively analyzed the feasibility, effectiveness and safety of zero-fluoroscopy radiofrequency and cryoablation of various types of SVTs in pediatric patients. Overall, in 171 consecutive patients (12.5 ± 3.9 years), 175 SVTs were diagnosed and 201 procedures were performed. The procedural success rate was 98% (193/197), or more precisely, 100% (86/86) for AVNRT, 95.8% (91/95) for AVRT, 94.1% (16/17) for AT and 100% (2/2) for AFL. No complications were recorded. Follow-up was complete in 100% (171/171) of patients. During the mean follow-up period of 488.4 ± 409.5 days, 98.2% of patients were arrhythmia-free with long-term success rates of 98.7% (78/79), 97.5% (78/80), 100% (13/13) and 100% (2/2) for AVNRT, AVRT, AT and AFL, respectively. Zero-fluoroscopy CA of various types of SVTs in the pediatric population is a feasible, effective and safe treatment option.

Persistence of Palpitations After Slow Pathway Modification for AVNRT in Young People

Symptoms are the most common indication for ablation in children with atrioventricular nodal reentrant tachycardia (AVNRT). After the procedure, patients may continue to report palpitations. The objective of this study was to quantify the risk and duration of palpitations after pediatric slow pathway modification as well as demographic and technical associations. This was a retrospective review of consecutive patients at a pediatric center who underwent slow pathway modification for AVNRT from 2012 to 2018. Patients with a prior ablation attempt or congenital heart disease were excluded. Palpitations were documented in 35% of patients after ablation. Neither post-ablation echo beats nor other evidence of residual dual AV nodal physiology were associated with a higher risk of post-ablation palpitations. Of the 35 patients with post-ablation palpitations, the median time to resolution of palpitations was 48 months. Acute procedural success was achieved in all 100 cases. There were two recurrences of AVNRT during long-term follow-up and one instance of ectopic atrial tachycardia (3% SVT recurrence). Palpitations after AVNRT ablation occurred in approximately one-third of cases, despite a low recurrence of true arrhythmia. Prior to ablation, patients and families should be counseled that post-ablation palpitations are common and AVNRT recurrence is rare.

Long-Term Patient Experience Following Acutely Successful Ablation of Supraventricular Tachycardia Substrate in Children

Definitive treatment of supraventricular tachycardia (SVT) substrate involves catheter ablation. While objective success rates have been well established, long-term subjective patient experiences have not been well described. We quantify a subjective cure rate and characterize long-term patient experience after acutely successful ablation. A cross-sectional survey of pediatric patients with accessory pathways or atrioventricular nodal reentrant tachycardia who underwent acutely successful ablation from 2008 to 2012 was performed. Data were obtained from medical records and patient surveys. Patients with congenital heart disease other than patent ductus arteriosus, patent foramen ovale, or coronary artery abnormalities were excluded. Statistical analyses included Student's t-test and χ² analysis for continuous and categorical variables, respectively. Surveys were sent to 153 patients of which 147 responded with median follow-up of 7.2 (IQR 6.1-8.5) years. Of the 147 responders, 124 (84%) patients reported cure with a male predominance. Symptoms were present in 130/147 (88%) patients pre-ablation and in 53/147 (36%) post-ablation. Among those with post-ablation symptoms, 50/53 (94%) reported symptomatic improvement. Recurrence occurred in 23/147 (16%) patients and was more prevalent following cryoablation. Ablation of SVT substrate can be curative with excellent long-term results and patient satisfaction. Long-term subjective cure rate is high and there is a substantial decrease in symptoms post-ablation. Many patients continue to have symptoms following ablation; however, the majority of these patients consider themselves cured and symptoms can be attributed to other etiologies. Recurrence is uncommon and occurs more frequently following cryoablation.

Double cryoenergy application (freeze-thaw-freeze) at growing myocardium: Lesion volume and effects on coronary arteries late after energy application. Implications for efficacy and safety in pediatric patients

INTRODUCTION

Cryoenergy is accepted as an alternative to radiofrequency ablation (RFA) in childen for ablation of supraventricular tachycardia substrates. Single cryoenergy application has been shown to be inferior to RFA. Double cryoenergy application has therefore been introduced into clinical practice, but experience concerning efficacy is limited. Coronary artery stenosis has been reported as serious complication after RFA for arrhythmia substrates but not after single cryoablation. The purpose of the study was to assess lesion volume (efficacy) and risk of coronary artery damage (safety), late, that is, 6 months, after double cryoenergy application in a piglet model.

METHODS

Two sequential cycles of cryoenergy were delivered at -75°C for 4 minutes at the atrioventricular groove in five piglets. Animals were restudied after 6 months by coronary angiography and intracoronary ultrasound (ICUS). Ablation lesions were examined histologically and lesion volume was determined by three-dimensional morphometric analysis.

RESULTS

Cryolesion volume was 174.04 ± 67.18 mm³ for atrial and 238.69 ± 112.1 mm³ for ventricular lesions (P > .05). Ventricular lesions, 4.06 ± 1.05 mm, were significantly deeper than atrial lesions, 3.58 ± 0.78 mm, (P < .05). In two of the 29 lesions, cryoenergy induced minor coronary artery injury with mild medial and adventitial thickening as well as minimal intimal proliferation, which had neither been detected by coronary angiography nor by ICUS.

CONCLUSION

Late after double cryoenergy application at growing myocardium, subclinical minor affection of the coronary artery wall could be detected with minimal intimal proliferation. As lifetime sequelae of this finding remains unknown, further studies are warranted to address safety of repeated cycles of cryoenergy application for tachycardia substrates in children.

"A Song of Ice and Fire"-another verse from the world of ablation

The debate between the use of radiofrequency (RF) or cryoenergy for ablation near the atrioventricular (AV) conducting system or small coronaries has been fueled by the relative efficacies and risks of the two technologies, particularly in smaller hearts. The manuscript by Schneider et al adds another chapter to that ongoing debate.

Pseudo cryomapping for ablation of atrioventricular nodal reentry tachycardia: A single center North American experience

Background

Most literature for cryoablation of atrioventricular nodal reentry tachycardia (AVNRT) is based on −30 degree celsius cryomapping with 4 & 6 mm distal electrode catheters. The cryomapping mode is not available on the 6 mm cryocatheter in the United States. We describe a technique for ‘pseudo’ mapping at −80° using a 6 mm cryocatheter and report on short and long term outcomes.

Methods

A retrospective analysis of all index cases (n = 253) of cryoablation of AVNRT at a single North American institution during the period of 2003–2010 was performed. The majority of cases utilized a 6 mm distal electrode tip catheter. Long term follow up (2.4 ± 1.8 years) was performed via review of the medical record and by questionnaire or telephone if necessary.

Results

Acute ablation success was achieved in 93% of cases, with transient conduction defects noted in 39% of cases, and long term conduction defects in 1.6% of cases (4 patients with PR prolongation, 2 of which were permanent). General anesthesia, male gender and presence of structural heart disease were more common in the acute failure cohort. The recurrence rate for AVNRT was 8%. These patients tended to be younger and had more transient A-V conduction defects during the index procedure than those without a recurrence.

Conclusions

In conclusion, anatomic cryoablation of AVNRT utilizing a 6 mm electrode catheter with mapping performed at −80° Celsius is a safe procedure with good long term efficacy. Transient A-V block during the index procedure increases the risk of late recurrence.

Effects of Triple Cryoenergy Application on Lesion Formation and Coronary Arteries in the Developing Myocardium

To improve long-term outcome after cryoablation of substrates of supraventricular tachycardia, application of two and three consecutive freeze-thaw cycles has been performed. The effect of triple freeze-thaw cycles on lesion formation within developing myocardium and coronary arteries, however, has not been studied yet. In eight piglets (mean age 15 weeks, weight 15-20 kg), 30 cryolesions (three consecutive freeze-thaw cycles) were applied to the atrial aspect of both AV valve annuli (n = 18) as well as to ventricular myocardium below the valves (n = 12). Coronary angiography was performed before and after cryoenergy application. The animals were reevaluated by coronary angiography and intracoronary ultrasound (ICUS) after 48 h. All hearts were removed for histological examination of the lesions subsequently. After staining (hematoxylin-eosin, desmin immunohistochemistry), lesions was measured by planimetry with a digital virtual miscroscope analysis system and volumes of the cryolesions were calculated. Mean atrial lesion volume was 190.68 ± 167.53 mm³ (n = 18), and mean ventricular lesion volume was 184.34 ± 107.42 mm³ (n = 12). Compared with previously reported data on lesion volumes after single and double freeze-thaw cycles, lesions were significantly larger. Coronary arteries were unaffected on coronary angiography as well as on ICUS. No affection of coronary arteries was found on histological examination. Application of three consecutive freeze-thaw cycles resulted in increased lesion volume compared with single and double freeze-thaw cycles. No affection of the coronary arteries was evident. To evaluate the clinical benefit and safety of triple cryoenergy application for catheter ablation, prospective randomized trials are required.

Cryoablation Versus Radiofrequency Ablation in AVNRT: Same Goal, Different Strategy

Catheter ablation is nowadays the first therapeutic option for AVNRT, the most common benign supraventricular tachycardia. Both cryotherapy and radiofrequency energy may be used to ablate the slow pathway. This paper compares both techniques, evaluates results published in literature and gives feedback on some typical aspects of cryo- and RF ablation. Although both techniques have satisfying success rates in AVNRT ablation, with a higher safety profile of cryoablation towards creation of inadvertent atrioventricular block, it remains paramount that the operator respects the distinctive traits of each technique in order to obtain an optimal result in every patient.

Radiofrequency catheter ablation can be performed with high success rates and very low complication rates in children and adolescents

AIM

Radiofrequency catheter ablation is a standard treatment for tachyarrhythmia in children. Recently, several centres using cryoenergy for ablation have reported high success and low complication rates, but an increased risk of recurrence of arrhythmia. The aim of this study was to report success, complications and recurrence rates for radiofrequency catheter ablation in children under current conditions.

METHODS

A retrospective cohort study of 333 consecutive children undergoing radiofrequency catheter ablation over the last two decades.

RESULTS

Radiofrequency catheter ablation was performed successfully in 96.7% of patients, but was significantly less successful in patients with a right anterior or right anterolateral accessory pathway (81.8%). Overall mortality was 0%; there was only one (0.3%) major complication, a pericardial haemorrhage, and only 2.8% of the patients developed minor vascular complications at the puncture site. None of the patients developed a persistent atrioventricular block. Over a median observation time of 4.3 years (0.1; 17.8), recurrence of arrhythmia occurred in 9.3% of all patients, but 50% of children with right lateral accessory pathways.

CONCLUSION

Radiofrequency catheter ablation can be performed with high success and very low complication rates in children. Recurrence rates are substantially lower than those reported for cryoablation in the literature.