[Answer] A 1-year-old boy is brought to the emergency department for evaluation of poor feeding irritability and sweating. The child is lethargic but arousable. He has labored breathing very rapid pulses and dusky color. His RR is 68/min HR 300/min and BP 70/45 mmHg. He has weak brachial pulses and absent radial pulses a capillary refill of 6 seconds SPO2 85% on RA and good bilateral BS. You administer high-flow O2 and place the child on a cardiac monitor and see the rhythm (SVT). The child has no history of congenital heart disease IV access has beeb established. Which therapy is most appropriate for this child?