A 2-month-old female infant from Mumbai is brought to the pediatric emergency department with severe dyspnea, intercostal retractions, and hepatomegaly. The mother reports that the baby has been feeding poorly and gaining weight slowly since birth. On auscultation, there is a loud systolic murmur at the left lower sternal border with a palpable thrill. Chest X-ray shows marked cardiomegaly and pulmonary edema. Echocardiography reveals a large ventricular septal defect (VSD) with a large left-to-right shunt and elevated pulmonary artery pressure. What is the most appropriate initial management strategy?