A 52-year-old man with a history of hypertension presents to the emergency department with acute chest pain radiating to the left arm. On examination, a new early diastolic murmur is heard at the left sternal border. ECG shows ST elevation in leads II, III, and aVF. Cardiac enzymes are elevated. Transthoracic echocardiography reveals acute aortic regurgitation with a flail aortic cusp. What is the most appropriate immediate next step in management?