Echocardiography reveals an ejection fraction of 25%, severe left ventricular hypertrophy, and global hypokinesis. The aortic valve leaflets appear heavily calcified, with restricted motion. The peak and mean gradients across the aortic valve are 40 and 28 mm Hg, and the valve area is 0.8 cm2. Right heart catheterization shows a cardiac output of 3.1 L/min.

##### Does this patient's aortic stenosis account for her clinical presentation?

Managing patients who have suspected severe aortic stenosis, left ventricular dysfunction, and low aortic valve gradients can be challenging. Although data for surgical intervention are not as robust for these patient subsets as for patients like Mr. A, several case series have suggested that survival in these patients is significantly better with surgery than with medical therapy alone.

Specific factors predict whether patients with ventricular dysfunction and low gradients will benefit from aortic valve replacement. Dobutamine stress echocardiography is helpful in distinguishing true severe aortic stenosis from “pseudostenosis,” in which leaflet motion is restricted due to primary cardiomyopathy and low flow. Distinguishing between true aortic stenosis and pseudostenosis is of paramount value, as surgery is associated with improved long-term outcomes in patients with true aortic stenosis (even though they are at higher surgical risk), whereas those with pseudostenosis will not benefit from surgery.

Infusion of dobutamine increases the flow across the aortic valve (if the left ventricle has contractile reserve; more on this below), and an increasing valve area with increasing doses of dobutamine is consistent with pseudostenosis. In this situation, treatment of the underlying cardiomyopathy is indicated as opposed to replacement of the aortic valve .

Contractile reserve is defined as an increase in stroke volume (> 20%), valvular gradient (> 10 mm Hg), or peak velocity (> 0.6 m/s) with peak dobutamine infusion. The presence of contractile reserve in patients with aortic stenosis identifies a high-risk group that benefits from aortic valve replacement.

Treatment of patients who have inadequate reserve is controversial. In the absence of contractile reserve, an adjunct imaging study such as computed tomography may be of value in detecting calcified valve leaflets, as the presence of calcium is associated with true aortic stenosis. Comorbid conditions should be taken into account as well, given the higher surgical risk in this patient subset, as aortic valve replacement in this already high-risk group of patients might be futile in some cases.

The ACC/AHA guidelines now give dobutamine stress echocardiography a class IIa indication (meaning the weight of the evidence or opinion is in favor of usefulness or efficacy ) for determination of contractile reserve and valvular stenosis for patients with an ejection fraction of 30% or less or a mean gradient of 40 mm Hg or less.

Ms. B underwent dobutamine stress echocardiography. It showed increases in ejection fraction, stroke volume, and transvalvular gradients, indicating that she did have contractile reserve and true severe aortic stenosis . Consequently, she was referred for surgical aortic valve replacement.