Effect of radiofrequency catheter ablation of accessory pathways on autonomic tone in children

Background: Radiofrequency catheter ablation is standard treatment for chil dren with re-entrant supraventricular tachycardias. Autonomic changes have been noted after such ablation for atrioventricular nodal re-entry tachycar dia, but not as well documented with atrioventricular re-entry over an acce ssory pathway. Methods and results: In 10 normal paediatric volunteers and 12 children ref erred for electrophysiologic testing and radiofrequency ablation of suprave ntricular tachycardia, con-invasive autonomic function tests and tilt-table testing were performed, and the variability in 24-h heart rate was analyse d. Patients with supraventricular tachycardia underwent these tests both 24 -72 h before and 24 h after ablation. Patients with tachycardia underwent a dditional autonomic testing to assess the sensitivity of baroreceptors and the intrinsic heart rate with autonomic blockade immediately before and aft er ablation. One non-invasive autonomic function test, namely handgrip, dem onstrated significant differences (p < 0.05) in diastolic blood pressure be fore and after ablation, though these values did not differ from controls. Significant decreases were noted in two indexes of the variability of heart rate before and after ablation (p < 0.05). Certain tilt test variables als o demonstrated significant differences between controls and those with tach ycardia subsequent to ablation. Intracardiac testing demonstrated changes ( p < 0.05) in sinus cycle lengths, effective refractory periods and/or blood pressures at baseline and during testing of the sensitivity of barorecepto rs before and after ablation. These changes were consistent with increased sympathetic or decreased parasympathetic tone. With autonomic blockade, the se differences were abolished. Conclusions. Catheter ablation of accessory pathways in children was associ ated with changes consistent with increased sympathetic or decreased parasy mpathetic tone. These autonomic changes persisted 24 h after the ablation p rocedure.