572301.fig.001
Figure 1: Initial ECG obtained in the pediatric ICU. Ectopic atrial tachycardia is present that is characterized by spontaneous termination and reinitiation, with a single low atrial escape beat before reinitiation (inset 1). Notice the change in P wave axis in lead V1 from biphasic to completely negative upon transition from the escape beat to the ectopic rhythm (white arrows), a finding highly suggestive of right atrial tachycardia [1]. This is followed by progressive prolongation of the PR interval until the P wave is obscured by the T wave (inset 2, black arrows), which is also common with this arrhythmia mechanism. The rhythm was slowest at the time of diagnosis, likely due to the large dose of benzodiazepine that had been ingested prior to admission.