It is rare for catheter ablation to be indicated as an arrhythmia treatment procedure in infants. The safety of catheter ablation in infants has been established by several studies, and the procedure is done to treat recalcitrant arrhythmias when absolutely necessary.^1-4 In this article, I describe a scenario in which an infant with congenital heart disease and other complicating medical conditions underwent successful catheter ablation of incessant atrial arrhythmias that could not be controlled with medical management. The patient required two catheter ablation procedures; the second one was done with a fluoroless technique. Fluoroless catheter ablation has been shown to be safe and successful in the pediatric population.⁵ As far as the author is aware, this is the first published description of fluoroless catheter ablation in an infant.

Case Description

The patient described here was a male infant born full-term; prenatal evaluation including fetal echocardiogram had confirmed the presence of congenital heart disease with dysplastic tricuspid valve and significant tricuspid regurgitation. In addition, the infant was known to have a dysplastic pulmonary valve with pulmonary stenosis. Since this was a ductal-dependent lesion for pulmonary blood flow, the patient was treated with prostaglandin E infusion for the first few days of life until transcatheter balloon valvuloplasty could be performed. This allowed for discontinuation of the prostaglandins, and spontaneous PDA closure without development of coarctation of the aorta. Other diagnostic possibilities such as Ebstein’s anomaly of the tricuspid valve, chromosomal abnormalities, and syndromes such as Noonan syndrome were ruled out.

The severity of the tricuspid regurgitation had resulted in right atrial enlargement, and consequently, he began to show evidence of atrial tachycardia (Figure 1). This was thought to be an ectopic atrial tachycardia, though immediately post his first surgery, there was suspicion that it could also be junctional ectopic tachycardia (JET). This was eventually proven during EP procedures to be a multifocal atrial tachycardia. At the time of his first surgical intervention with repair of tricuspid valve and surgical valvotomy of the pulmonary valve, cryoablation of the cavotricuspid isthmus was performed. Atrial arrhythmia continued after this surgery, and the patient was initially treated with IV esmolol for rate control. He continued to have breakthrough arrhythmia on esmolol, so amiodarone was also started. Unfortunately, the amiodarone could not be continued because the infant’s congenital screens returned positive for hypothyroidism. Endocrine specialists were consulted, and he was started on Synthroid therapy. With the addition of Synthroid therapy, his arrhythmia became even more intractable to medical management. Other medications were attempted, including sotalol, mexiletine, and flecainide, but eventually the only successful drug was IV lidocaine.

Therefore, the first EP study with catheter ablation was performed at 2 months of age, weight of 5.6 kg. At the time of this procedure, 3D mapping with EnSite NavX (St. Jude Medical) was attempted, but there was limited left-to-right vector spatial resolution because the NavX patches were likely cut too small. For skin patch placement in small-size pediatric patients, the patches can be trimmed to a smaller size, but if they are too small, they cannot generate sufficient electromagnetic field for catheter localization. This first EP procedure involved classic mapping for atrial tachycardia, and showed a low right atrial (likely crista) ectopic focus which was treated with radiofrequency (RF) ablation (Marinr 6Fr RF catheter, Medtronic, Inc.). A simplified minimal access, single-catheter mapping approach was utilized, with the ablation catheter advanced through a 6Fr sheath in the right femoral vein. Timing reference was P wave onset. Total fluoroscopy time for this first procedure was 20.8 minutes.

 
At the time of the first EP procedure, only one atrial focus was evident and was successfully treated, but afterwards there was arrhythmia recurrence with high burden. It became clear that the patient had true multifocal atrial tachycardia. IV and then oral beta blocker therapy was again utilized, and the patient was sent home for several months in good condition despite a daily arrhythmia burden of 30-40%. Medical management did provide rate control, and interval evaluations by echocardiogram did not demonstrate worsening tricuspid regurgitation, increased ventricular size, or diminished systolic function. The patient was allowed to grow. At 6 months of age, despite higher doses of propranolol and the addition of flecainide therapy, the arrhythmia burden increased and he was readmitted for IV medical management.  

Since the arrhythmia burden remained significant despite drug therapy, re-ablation was attempted at 6 months of age, patient weight 11 kg. At this procedure, the strategy of minimal access with two EP catheters was again employed, with a single RIJ sheath to introduce a 5Fr 10-pole AFocus catheter (St. Jude Medical) for pacing, recording, standard mapping, and 3D mapping, and a single RFV sheath for the ablation catheter. The NavX patches were again trimmed to fit the small body surface area, but care was taken to not over-trim. For this procedure, they were successful in providing excellent three-dimensional spatial resolution, allowing for complete fluoroless technique. The arrhythmia focus was quickly identified with rapid LAT and standard mapping techniques. The decapolar spiral catheter provided an initial target zone, and the ablation catheter helped localize more precisely the areas of early atrial activation in the medial right atrium close to the IVC/RA junction (Figure 2). Cryoablation is the preferred modality for ablation in fluoroless situations for safety reasons, and was utilized to successfully eliminate the focal atrial tachycardia. There was a second arrhythmia focus superiorly above the tricuspid annulus that was also successfully treated with cryoablation (not shown in figure). The procedure time was two hours.

After the second ablation, the patient’s antiarrhythmic therapy was discontinued and he has remained arrhythmia free for over one year.

Summary

The primary advantage of fluoroless ablation in children is elimination of significant radiation exposure and limiting exposure in patients with chronic illness. Therefore, it has become a priority at congenital heart centers. In this case with multifocal ectopic atrial tachycardia, several important ablation strategies allowed for successful arrhythmia treatment including pre-procedure planning, gentleness of approach, general anesthesia, modified 3D NavX mapping system, minimal access, high-density mapping with a small decapolar spiral catheter, and cryoablation. ■

Acknowledgements: The Florida Hospital for Children pediatric EP lab staff members: Maribel Pontieri, RN, BSN; Saturnino Echeverria, RRT, RCIS; Stephanie Stevenson, RCIS, CCT, ASRN.

Disclosures: The author has no conflicts of interest to report regarding the content herein.   

References

1. Kugler JD, Danford DA, Deal BJ, et al. Radiofrequency catheter ablation of tachyarrhythmias in children and adolescents. The Pediatric Electrophysiology Society. N Engl J Med. 1994;300:1481-1487.
2. Blaufox AD, Felix GL, Saul JP, Pediatric Catheter Ablation Registry. Radiofrequency catheter ablation in infants ≤18 months old: when is it done and how do they fare? Short-term data from the pediatric ablation registry. Circulation. 2001;104:2803-2808.
3. Blaufox AD. Catheter ablation of tachyarrhythmias in small children. Indian Pacing Electrophysiol J. 2005;5(1):51-62.
4. Kugler JD, Danford DA, Houston KA, et al. Pediatric radiofrequency catheter ablation registry success, fluoroscopy time, and complication rate for supraventricular tachycardia: comparison of early and recent eras. J Cardiovasc Electrophysiol. 2002;13:336-341.
5. Smith G, Clark JM. Elimination of fluoroscopy use in a pediatric electrophysiology laboratory utilizing three-dimensional mapping. Pacing Clin Electrophysiol. 2007;30(4):510-518.