Rome, Italy - A new study testing cryoablation in pediatric patients with atrioventricular nodal reentrant tachycardia (AVNRT) indicates that the procedure is safe, with excellent immediate results.[1] Arrhythmia recurrence in almost one third of the patients during follow-up, however, means that future studies of cryosurgical methods, particularly in young people, will have to specifically investigate the etiology of recurrences in this group, according to Dr Fabrizio Drago and colleagues (Bambino Gesu Hospital, Rome, Italy). Their study appears in the April 5, 2005 issue of the Journal of the American College of Cardiology.

Radiofrequency (RF) ablation is currently the preferred means of treating supraventricular tachycardias (SVT), but, because the lesion created by RF is typically very close to the AV node or His bundle, it carries a risk of atrioventricular block. Cryoablation has the advantage of permitting cryomapping before the creation of permanent lesions and is generally better tolerated than RF. While cryoablation is being used more and more frequently in adult patients, its safety and efficacy in children and teens have not been specifically tested.

In their study, Drago et al treated 26 patients ranging in age from five to 20 (mean age 13) years who had AVNRT, Wolff-Parkinson-White syndrome, or reentrant SVT due to concealed accessory pathways using a cryoablation catheter. Cryomapping at -30°C was performed in all patients to identify the appropriate site, and then ablation was performed at -75°C for approximately four to eight minutes.

No cryoablation-related complications were seen, and cryoablation was acutely successful in 24 out of 26 patients. Over a follow-up period of up to two years, however, seven patients (29%) out of the 24 had arrhythmia recurrence, all occurring within one year of their procedures; these patients were subsequently treated with RF ablation or drug therapy or did not require drugs.

Drago et al speculate that a slightly lower-than-average number of cryoablation deliveries to the target site and/or warmer-than-average temperatures may have played a role in the failure to eradicate arrhythmias in these patients. Given the small numbers of patients in this study, the investigators say, the potential importance of cryoablation characteristics associated with long-term arrhythmia eradication should be explored further. Of note, four patients in the no-recurrence group had had previous RF ablation, whereas no patients in the recurrence group had had previous treatment.

Still, they say, given the "excellent" safety of the procedure, cryoablation could be considered as a possible first-line therapy in young people.

"We do think that in dealing with children, it's better to do a procedure with a little bit lower success rate and no risks than to do a procedure with an higher long-term success rate, but with the risk, even if low, of severe complications," Drago commented in a press statement.

To heartwire, Drago emphasized that the techniques used for reentry circuit ablation in his study could easily be replicated by other clinicians. He added that his paper should not necessarily change how doctors are currently performing ablation but emphasized that cryoablation should be "the first interventional choice" in children with SVT and that this is particularly true in very young children and in those with the reentry circuit located very close to the His bundle.