18-Month-Old with Lethargy and Accelerated Idioventricular Rhythm in Prehospital Setting: A Case Report

We report a case of accelerated idioventricular rhythm (AIVR) identified by Emergency Medical Services (EMS) monitoring of an infant presenting with lethargy and respiratory distress. Accelerated idioventricular rhythms are rare ventricular rhythms originating from the His-Purkinje system or ventricular myocytes, consisting of >3 monomorphic beats with gradual onset and termination.¹ An AIVR is usually well-tolerated and does not require treatment, though sustained arrythmia may induce syncope, and the rhythm has been seen in newborn infants with congenital heart diseases.¹ Monitoring ill children with ECG can identify such dysrhythmias in the prehospital setting.

An 18-month-old male presented to their pediatrician with lethargy and respiratory distress, prompting activation of EMS. The patient was placed on a 4-lead ECG initially revealing monomorphic QRS complexes at a rate of 170 beats per minute (BPM). A 12-lead ECG was interpreted as sinus tachycardia by the paramedics who noted the QRS complexes were "getting taller and shorter" with a stable rapid heart rate. The clinician then noted a consistently wide tachycardia which spontaneously converted to a narrow complex tachycardia. The QRS pattern remained variable, with notation of variable R-wave height. After arrival to the emergency department, pediatric cardiology was consulted and interpreted the prehospital ECG findings as accelerated idioventricular rhythm. The patient experienced multiple occurrences of accelerated idioventricular rhythm during hospitalization without associated hypoxia or decreased perfusion.

Accelerated idioventricular rhythm is relatively rare entity without underlying cardiac disease and most cases are asymptomatic or benign. In the pediatric population, AIVR is generally related to congenital heart defects, cardiac tumors, and cardiomyopathies. In the prehospital setting, continuous ECG monitoring should be a part of care by Advanced Life Support personnel in children with altered mental status, respiratory distress, unexplained syncope, or suspected arrhythmias and 12 lead ECG should be considered if there is any abnormality noted. While this patient did not experience persisting morbidity from AIVR, the potentially hazardous rhythm would not have been recognized without the astute observation, clinical management and persistent follow up of the prehospital clinicians.