Q. A 1-month-old female is brought to the office by her mother for a well-child visit. Her mother reports that the patient is doing well. On examination, pulse is 120/min and respirations are 30/min. Oxygen saturation is 95% on room air. Physical examination shows a noncyanotic patient that is breathing well without difficulty. Lung auscultation is normal. Chest examination reveals a harsh holosystolic murmur with an audible thrill that presents at the lower left sternal border. Blood pressure is 80/40 mmHg in the right arm and 76/36 mmHg in the right leg. A chest x-rays shows enlargement of the left heart. What is the diagnosis?