Enlargement of Catheter Ablation Lesions in Infant Hearts With Cryothermal Versus Radiofrequency Energy

Recurrent single echo beats after cryoablation of atrioventricular nodal reentrant tachycardia: The pediatric population

BACKGROUND

Cryoablation for atrioventricular nodal reentrant tachycardia (AVNRT) is effective and safe with a reported limitation of lower success and higher recurrence rates. We have observed cases in which slow pathway conduction was eliminated as demonstrated by atrial extra-stimulus testing within 1 min of cryo-energy delivery but returned following tissue rewarming. Frequently, slow pathway conduction persisted despite multiple acutely successful lesions over a broad anatomic region. We aimed to determine if return of slow pathway conduction after elimination during cryoablation represents a risk for recurrent AVNRT with the same intermediate term results as slow pathway ablation. We hypothesize that remnant single echo beats in the absence of sustained slow pathway conduction and inducible AVNRT is an acceptable end point after clear slow pathway elimination during cryoablation.

METHODS

Retrospective chart review of patients undergoing attempted slow pathway ablation for AVNRT using solely cryoablation between January 2015-January 2018.

RESULTS

Forty-four patients met inclusion criteria with at-least 2 features of dual AVN physiology. 19 patients had return of slow pathway conduction shortly after clear elimination during cryoablation (Group A) while 25 did not (Group B). All in Group A had recurrent single echo beats but none had sustained slow pathway conduction at the end of the procedure nor AVNRT recurrence at 1 year.

CONCLUSION

Recurrent single echo beats with absent sustained slow pathway conduction and non-inducible AVNRT may be an acceptable endpoint for slow pathway ablation of AVNRT using cryoablation when there is elimination of slow pathway demonstrated during energy delivery.

Late effects of radiofrequency ablation lesions resulting in a progressive mitral valve perforation in a 2-month-old infant

There has been great concern with the use of radiofrequency ablation in infants since radiofrequency ablation lesions were shown to have a progressing nature in immature myocardium of animals. In this report, we present a 2-month-old infant with life-threatening medically refractory supraventricular tachycardia. Radiofrequency ablation successfully cured arrhythmia; however, late effects of radiofrequency ablation lesions resulted in a progressive mitral valve perforation requiring surgical repair.

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.

The quest for durable lesions in catheter ablation of atrial fibrillation - technological advances in radiofrequency catheters and balloon devices

INTRODUCTION

Atrial fibrillation is the most common cardiac arrhythmia and represents a growing clinical, social and economic challenge. Catheter ablation for symptomatic atrial fibrillation has evolved from an experimental procedure into a widespread therapy and offers a safe and effective treatment option. A prerequisite for durable PVI are transmural and contiguous circumferential lesions around the pulmonary veins. However, electrical reconnection of initially isolated pulmonary veins remains a primary concern and is a dominant factor for arrhythmia recurrence during long-term follow up. Areas covered: This article discusses the physiology of lesion formation using radiofrequency-, cryo- or laser- energy for pulmonary vein isolation and provides a detailed review of recent technological advancements in the field of radiofrequency catheters and balloon devices. Finally, future directions and upcoming developments for the interventional treatment of atrial fibrillation are discussed. Expert commentary: Durable conduction block across deployed myocardial lesions is mandatory not only for PVI but for any other cardiac ablation strategy as well. A major improvement urgently expected is the intraprocedural real-time distinction of durable lesions from interposed gaps with only transiently impaired electrical conduction. Furthermore, a simplification of ablation tools used for PVI is required to reduce the high technical complexity of the procedure.

Heart Rhythm Society: expert consensus statements-part 2

One of the most important roles for professional societies in medicine is assembling multiple stakeholders and experts to develop documents that can help guide and define policies and strategies for best medical care. Each year the Heart Rhythm Society (HRS) develops several consensus documents that address critical clinical subjects that have been identified by input from HRS members and HRS committees. Over the past 5 years, HRS has produced documents with multiple professional societies from around the world, and although the topics chosen for exploration center around arrhythmia management, the reviews and recommendations made in the documents are important for clinical cardiologists and generalists who are not arrhythmia specialists. When an internist or other primary care provider identifies a patient who may be having symptoms from an arrhythmia, the referral first is made to the clinical cardiologist and only later, if necessary, does an arrhythmia specialist become involved. These expert consensus statements are developed for specific clinical questions regarding arrhythmia management where there is controversy or uncertainty, often with less data from randomized controlled trials to help guide recommendations, which must then be made by extrapolation of existing data, observational data, and expert opinion. In this 2-part review, the consensus statements developed by the HRS over the past 5 years that pertain to adults are discussed in part 1; part 2 focuses on consensus statements that HRS has developed in conjunction with the Pediatric and Congenital Electrophysiology Society that address arrhythmia issues in children and adults with congenital heart disease.

Who Needs Catheter Ablation And Which Approach?

Catheter ablation therapy for atrial fibrillation (AF) has gained a significant role during maintenance of sinus rhythm compared to anti-arrhythmic medication. Catheter ablation techniques are also improved and progressed over years in parallel to better understanding of disease mechanisms and technological advancements. However, due to invasive nature of the therapy with its pertinent procedural risks, both appropriate patient selection and use of relevant approach should be considered by all electrophysiologists before decide to perform catheter ablation.

Optimizing outcomes of catheter ablation in infants and toddlers

Since the introduction of transcatheter ablation in the late 1980s, there has been significant technical development. With a very high success rate and low complication rate, ablation has now become the standard of care in children and adults. However, long-term data remain insufficient and the application of ablation therapy in small children is debatable. In this review, current treatment strategies and results in toddlers and infants will be discussed. There has been improvement in success rate and complication rate for ablation in small children. Technological advancements in non-fluoroscopic electroanatomical mapping systems (3D systems) have led to the reduction of radiation and have facilitated ablations in complex cases. However, long-term effects of ablation lesions in small children remain a potential concern.

Perspectives in ablation of arrhythmias in children and patients with congenital heart disease

Although most arrhythmias in children have a benign outcome, recurrent arrhythmic events have a significant impact on quality of life. Electrophysiology studies with ablation have good short-term success and an acceptably low complication rate. The long-term outlook for this patient group is incompletely defined, however. Factors that require special consideration in children include the need to limit the size, depth and number of lesions, and the radiation exposure incurred during fluoroscopy-guided catheters manipulation. The use of cryoablation seems promising in limiting lesion size. Three-dimensional (3D) mapping systems clearly have been shown to reduce the radiation dose. In congenital heart disease, these advances in technology have helped to further our understanding of the mechanisms underlying arrhythmias. It is anticipated that earlier intervention and newer operative techniques will reduce the incidence of postoperative arrhythmias in the future. For those patients who still develop tachyarrythmias after cardiac surgery, the use of three-dimensional systems and other new technologies permits more efficient intervention in the electrophysiology laboratory.

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.