Investigators hypothesize that PEM fellow-performed cardiac POCUS, when supported by AI analysis for LV dysfunction, will demonstrate diagnostic accuracy comparable to complete echocardiogram interpretation in identifying (1) pericardial effusion and (2) left ventricular systolic dysfunction in children with preexisting cardiac disease. Investigators anticipate that AI will improve accuracy and image interpretation confidence among trainees. Prospective evaluation of this method may influence future ED workflows, enhance resource utilization, support training pathways, and potentially reduce time to diagnosis in this high-risk pediatric population.