OBJECTIVES: To study the association of time intervals on adenosine therapy with the occurrence of refractory supraventricular tachycardia (SVT) in children. METHODS: We reviewed 334 episodes of presumed SVT requiring adenosine in children (<18years) who visited 4 academic hospital emergency departments (EDs) from July 2013 through June 2017. Refractory SVT was defined as an SVT episode persisting after 2 doses of adenosine. Clinical and electrocardiographic findings, and symptom-to-adenosine (symptom-to-ED plus ED-to-adenosine) time of refractory and responsive SVT episodes were compared. Multivariable logistic regression was performed to identify factors associated with the occurrence of refractory SVT. RESULTS: Of 211 SVT episodes, 42 episodes of refractory SVT (19.9%) were noted (overall sinus conversion rate, 79.6%). The refractory episodes were associated with a higher frequency of known structural heart diseases (9.5% vs. 1.8%; P=0.030) and a longer median ED-to-adenosine time (15.5 vs. 11.0min; P=0.018). The association of the ED-to-adenosine time with refractory SVT remained significant after adjustment (for increment of 1min; aOR, 1.02; 95% CI, 1.007-1.04). CONCLUSIONS: Delayed adenosine therapy is associated with the occurrence of refractory SVT in children, supporting the need for prompt adenosine therapy.