chest pain; children; Covid 19; adult; blood sampling; cardiologist; child; chronic disease; clinical feature; conference abstract; controlled study; coronavirus disease 2019; echocardiography; electrocardiogram; electrocardiography; emergency ward; female; follow up; habit; heart left bundle branch block; human; human tissue; major clinical study; male; medical record; nonhuman; pandemic; patient referral; pediatric cardiology; retrospective study; Severe acute respiratory syndrome coronavirus 2; sinus tachycardia; supraventricular tachycardia; thorax pain; Turkey (republic); vulnerability; young adult; endogenous compound; troponin