A 79-year-old female with a history of coronary artery disease and a prior myocardial infarction presents with exertional dyspnea. There is a II/VI systolic ejection murmur at the right upper sternal border with a soft S2 heart sound. Echocardiography reveals an ejection fraction of 25% and a mean pressure gradient across the aortic valve of 30 mm Hg. The aortic valve area measured 0.9 cm2. Coronary angiography reveals no new coronary stenosis. Which of the following is the most appropriate next step?
A. Surgical aortic valve repalcement
B. Dobutamine stress echocardiography
C. Treadmill exercise stress testing
D. No further therapy is required