In children, the first episode of supraventricular tachycardia occurs at various ages. The aim of this study is to describe age-specific tachycardia mechanisms, clinical findings, and outcome in a contemporary cohort of paediatric patients with supraventricular tachycardia.

Retrospective analysis of 531 consecutive patients with structurally normal hearts under the age of 18 years who underwent invasive electrophysiological study for supraventricular tachycardia. The study population was divided into two groups, early-onset group (n = 57) and late-onset group (n = 474), according to the age of the occurrence of the first tachycardia before or after the age of 12 months.

Accessory pathway-mediated tachycardia was more common (82.5 versus 50.1%, p < 0.001) and the proportion of left-sided accessory pathways was more pronounced (74.5 versus 53.7%, p = 0.01) in the early-onset group than in the late-onset group. The antegrade and retrograde refractory periods of the accessory pathways were similar in both groups, but pre-excitation was more common in the early-onset group (50.9 versus 31.9%, p = 0.007). Typical atrioventricular nodal re-entrant tachycardia was more common (36.7 versus 7.0%, p < 0.001) in the late-onset group. There was no difference among the two groups regarding overall outcome.

Accessory pathway-mediated re-entrant tachycardia is the most common mechanism of recurrent supraventricular tachycardia in infants with structurally normal hearts who are later referred to an electrophysiological study. These pathways often cause pre-excitation and tend to be located on the left side whereas their refractory period is not different from that of patients with late-onset tachycardia.

The aim was to attach importance to the hazards of ventricular pre-excitation on left ventricular systolic function and size.

We analysed the clinical, electrophysiological, and echocardiographic characteristics of the 25 cases with abnormal ventricular wall motion, left ventricular systolic dysfunction, or dilation with co-existing right-sided overt accessary pathways before and after ablation or medication during March 2011 and June 2017. Moreover, we compared the therapy effect between patients with ventricular pre-excitation-induced dilated cardiomyopathy and idiopathic dilated cardiomyopathy without ventricular pre-excitation.

Abnormal ventricular wall motion was demonstrated using M-mode echocardiography in 23 cases. The basal segments of the interventricular septum became thin and moved similarly to an aneurysm with typical bulging during end-systole, which was observed in 16 cases. Dilated cardiomyopathy was diagnosed in 14 cases. A total of 23 patients underwent successful ablations and received medications, and the other two patients received only oral medications because of young age. The prognosis of pre-excitation-induced dilated cardiomyopathy is better than idiopathic dilated cardiomyopathy. All the cases with abnormal ventricular wall motion demonstrated recovery of normal left ventricular ejection fraction and decreased left ventricular end-diastolic diameter through ablation.

Ventricular pre-excitation caused by right-sided accessory pathways may result in abnormal ventricular wall motion, left ventricular systolic dysfunction, dilation, and even dilated cardiomyopathy. In some cases with dilated cardiomyopathy, ventricular pre-excitation may not be the cause of disease but a harmful factor which hampered the recovering of left ventricular systolic function. These conditions are indications for ablation with good prognosis.

Radiofrequency catheter ablation is the mainstay of therapy for supraventricular tachyarrhythmias. Conventional radiofrequency catheter ablation requires the use of fluoroscopy, thus exposing patients to ionising radiation. The feasibility and safety of non-fluoroscopic radiofrequency catheter ablation has been recently reported in a wide range of supraventricular tachyarrhythmias using the EnSite NavX™ mapping system. The NO-PARTY is a multi-centre, randomised controlled trial designed to test the hypothesis that catheter ablation of supraventricular tachyarrhythmias guided by the EnSite NavX™ mapping system results in a clinically significant reduction in exposure to ionising radiation compared with conventional catheter ablation.

The study will randomise 210 patients undergoing catheter ablation of supraventricular tachyarrhythmias to either a conventional ablation technique or one guided by the EnSite NavX™ mapping system. The primary end-point is the reduction of the radiation dose to the patient. Secondary end-points include procedural success, reduction of the radiation dose to the operator, and a cost-effectiveness analysis. In a subgroup of patients, we will also evaluate the radiobiological effectiveness of dose reduction by assessing acute chromosomal DNA damage in peripheral blood lymphocytes.

NO-PARTY will determine whether radiofrequency catheter ablation of supraventricular tachyarrhythmias guided by the EnSite NavX™ mapping system is a suitable and cost-effective approach to achieve a clinically significant reduction in ionising radiation exposure for both patient and operator.