Clinical efficacy of Doppler-echocardiographic indices of aortic valve stenosis: a comparative test-based analysis of outcome.

OBJECTIVES: This study was designed to assess which hemodynamic index best accounts for clinical severity of aortic stenosis (AS) and to analyze the value of low-dose dobutamine testing. BACKGROUND: Pressure gradient and valve area are suboptimal because they depend on flow rate, correlate poorly with symptoms, and provide limited prognostic information. Recently, new indices and low-dose inotropic stimulation have been introduced, but their clinical value remains uncertain. METHODS: A total of 307 consecutive patients with AS were included in an ambispective study design (71 +/- 12 years old; peak jet velocity: 3.7 +/- 1.1 m/s). Clinical and Doppler-echocardiographic data were obtained, as well as results of low-dose dobutamine infusion (47 patients). Using receiver-operator-characteristic curve analysis, we evaluated jet velocity, pressure gradient, valve area, resistance, stroke-work loss (SWL), and dobutamine-induced increase in area for predicting 1) symptomatic status at entry, 2) early (25% best discriminated clinical end points. Other independent predictors of prognosis were symptomatic status and left ventricular ejection fraction. Dobutamine testing added no value to baseline models. CONCLUSIONS: Non-flow-corrected indices show the highest clinical efficacy in aortic stenosis. Among these, SWL best predicts symptomatic status and outcome and therefore should be incorporated to aid patient management in unclear situations.

Stress Echocardiography in Aortic Stenosis: Insights into Valve Mechanics and Hemodynamics.

Stress interventions have been classically combined with cardiac catheterization recordings to understand the hemodynamic principles of valvular stenosis. Indices of aortic stenosis such as pressure gradient and valve area were based on simple hydraulic principles and have proved to be clinically useful for patient management during a number of decades. With the advent of Doppler echocardiography, these hemodynamic indices can be readily obtained noninvasively. Abundant evidence obtained using exercise and pharmacological stress echocardiography has demonstrated that the assumptions of classic hemodynamic models of aortic stenosis were wrong. Consequently, it is recognized that conventional indices may be misleading indicators of aortic stenosis significance in particular clinical situations. To improve diagnostic accuracy, several alternative hemodynamic models have been developed in the past few years, including valve resistance and left ventricular stroke work loss, among others. Nevertheless, these more-accurate indices should be obtainable noninvasively and need to demonstrate greater diagnostic and prognostic power than conventional indices; preliminary data suggest such superiority. Stress echocardiography is well established as the tool of choice for testing hypothesis and physical models of cardiac valve function. Although the final role of alternative indices is not yet well established, the new insights into valvular hemodynamics provided by this technique may change the clinical assessment of aortic stenosis.