Is There a Difference in Tachycardia Cycle Length during SVT in Children with AVRT and AVNRT?

There are limited adult data suggesting the tachycardia cycle length (TCL) of atrioventricular reentry tachycardia (AVRT) is shorter than atrioventricular nodal reentry tachycardia (AVNRT), though little data exist in children. We sought to determine if there is a difference in TCL between AVRT and AVNRT in children.

A single-center retrospective review of children with supraventricular tachycardia (SVT) from 2000 to 2015 was performed.

Age ≤ 18 years, invasive electrophysiology study (EPS) confirming AVRT or AVNRT.

Atypical AVNRT, congenital heart disease, antiarrhythmic medication use at time of EPS. Data were compared between patients with AVRT and AVNRT via t-test, χ² test, and linear regression.

A total of 835 patients were included (12 ± 4 years, 52 ± 31 kg, TCL 321 ± 55 ms), 539 (65%) with AVRT (270 Wolff-Parkinson-White, 269 concealed pathways) and 296 (35%) with AVNRT. Patients with AVRT were younger (11.7 ± 4.1 years vs 13.0 ± 3.6 years, P < 0.001) and smaller (49 ± 22 kg vs 57 ± 43 kg, P < 0.001). In the baseline state, the TCL was shorter in AVRT than AVRNT (329 ± 51 ms vs 340 ± 60 ms, P = 0.04). In patients requiring isoproterenol to induce SVT, there was no difference in TCL (290 ± 49 ms vs 297 ± 49 ms, P = 0.26). When controlling for age, there was no difference in TCL between AVRT and AVNRT at baseline or on isoproterenol. The regression equation for TCL in the baseline state was TCL = 290 + 4 (age), indicating the TCL will increase by 4 ms above a baseline of 290 ms for each year of life.

When controlling for age, there is no difference in the TCL between AVRT and AVNRT in children. Age, not tachycardia mechanism, is the most significant factor in predicting TCL.