Predictors of Outcomes in Low-Flow, Low-Gradient Aortic Stenosis

Abstract

Background— Patients with low-flow, low-gradient aortic stenosis have a poor prognosis with conservative therapy but a high operative mortality if treated surgically. Recently, we proposed a new index of aortic stenosis severity derived from dobutamine stress echocardiography, the projected aortic valve area at a normal transvalvular flow rate, as superior to other conventional indices to differentiate true-severe from pseudosevere aortic stenosis. The objective of this study was to identify the determinants of survival, functional status, and change in left ventricular ejection fraction during follow-up of patients with low-flow, low-gradient aortic stenosis. Methods and Results— One hundred one patients with low-flow, low-gradient aortic stenosis (aortic valve area ≤1.2 cm 2 , left ventricular ejection fraction ≤40%, and mean gradient ≤40 mm Hg) underwent dobutamine stress echocardiography and an assessment of functional capacity using the Duke Activity Status Index. A subset of 72 patients also underwent a 6-minute walk test. Overall survival was 70±5% at 1 year and 57±6% at 3 years. After adjusting for age, gender, and the type of treatment (aortic valve replacement versus no aortic valve replacement), significant predictors of mortality during follow-up were a Duke Activity Status Index ≤20 ( P =0.0005) or 6-minute walk test distance ≤320 m ( P <0.0001, in the subset of 72 patients), projected aortic valve area at a normal transvalvular flow rate ≤1.2 cm 2 ( P =0.03), and peak dobutamine stress echocardiography left ventricular ejection fraction ≤35% ( P =0.03). More severe stenosis, defined as projected aortic valve area ≤1.2 cm 2 , was a predictor of mortality only in the no aortic valve replacement group. The Duke Activity Status Index, 6-minute walk test, and left ventricular ejection fraction improved significantly during follow-up in the aortic valve replacement group, but remained unchanged or decreased in the no aortic valve replacement group. Conclusion— In patients with low-flow, low-gradient aortic stenosis, the most significant risk factors for poor outcome were (1) impaired functional capacity as measured by Duke Activity Status Index or 6-minute walk test distance; (2) more severe valve stenosis as measured by projected aortic valve area at a normal transvalvular flow rate; and (3) reduced peak stress left ventricular ejection fraction, a composite measure accounting for both resting left ventricular function and contractile reserve.