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
The dilemma in this situation is quite common. Is the pressure gradient of 30 mm Hg across the aortic valve (in the moderate range) accurate, or is it reduced because the left ventricular systolic function is poor and the ventricle is too weak to create adequate force to open the aortic valve fully? (Note the aortic valve area is in the severe range.) The best diagnostic test to determine if this phenomenon ― termed “low-flow, low-gradient aortic stenosis” ― is present is to infuse dobutamine and repeat the measurements.
If severe aortic valve stenosis is indeed present, the valve area calculation will remain below 1.0 cm2, and the pressure gradient will increase with dobutamine infusion. If the aortic stenosis is moderate, the valve area will increase and the pressure gradient may not increase to a large degree with dobutamine.
Alternatively, using the “dimensionless index,” another echocardiographic measurement can be helpful since this is a “flow independent” parameter. If the dimensionless index is less than 0.25, then severe aortic stenosis is present.