A 70-year-old man with chronic hypertension and hyperlipidemia presents with progressive dyspnea on exertion and exertional chest pain. On examination there is a harsh late-peaking systolic murmur at the right upper sternal border radiating to the carotids, with diminished and delayed carotid upstrokes. Echocardiogram shows severe aortic stenosis with valve area 0.7 cm2 and mean gradient 48 mm Hg. Which is the most appropriate next step in management?