(Circulation. 2000;101:765.)
© 2000 American Heart Association, Inc.
Clinical Investigation and Reports |
Assessment of Aortic Valve Stenosis Severity
A New Index Based on the Energy Loss Concept
From the Laboratoire de génie biomédical, Institut de recherches cliniques de Montréal, Montreal (D.G., P.P., F.S., L.-G.D.), and Quebec Heart Institute/Laval Hospital, Laval University, Ste-Foy, Quebec (P.P., J.G.D.), Canada.
Background—Fluid energy loss across stenotic aortic valves is influenced by factors other than the valve effective orifice area (EOA). We propose a new index that will provide a more accurate estimate of this energy loss.
Methods and Results—An experimental model was designed to measure
EOA and energy loss in 2 fixed stenoses and 7
bioprosthetic valves for different flow rates and 2 different
aortic sizes (25 and 38 mm). The results showed that the
relationship between EOA and energy loss is influenced by both flow
rate and aortic cross-sectional area (AA) and that the
energy loss is systematically higher (15±2%) in the large aorta. The
coefficient (EOAxAA)/(AA-EOA) accurately
predicted the energy loss in all situations
(r2=0.98). This coefficient is more closely
related to the increase in left ventricular workload than
EOA. To account for varying flow rates, the coefficient was indexed for
body surface area in a retrospective study of 138 patients with
moderate or severe aortic stenosis. The energy loss index
measured by Doppler echocardiography was
superior to the EOA in predicting the end points, which were defined as
death or aortic valve replacement. An energy loss index 
0.52
cm2/m2 was the best predictor of adverse
outcomes (positive predictive value of 67%).
Conclusions—This new energy loss index has the potential to reflect the severity of aortic stenosis better than EOA. Further prospective studies are necessary to establish the relevance of this index in terms of clinical outcomes.
Key Words: echocardiography • hemodynamics • valves • stenosis
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