LAUSR

INTRODUCTION We analyzed the relationship between flow (Q) and aortic valve opening area (AVA) using a sequence of echocardiographic stress tests of increasing strength. Low-dose dobutamine stress echocardiography (DSE) has been used to differentiate pseudo-severe from true severe aortic stenoses. Because the Q-response to DSE is so variable between individuals, AVA has been projected to a standardized flow (AVAproj) using linear interpolation. A linear Q-to-AVA-relation implies that AVA shows an unconstrained increase. We applied three stress maneuvers of increasing strength to investigate whether AVA shows signs of saturation. METHODS We performed an echocardiographic exam at rest, during the passive leg raise maneuver ("PLR"), maximal dobutamine infusion ("Dmax"), and their combination ("Dmax+PLR") in 45 patients with severe low-flow, low-gradient aortic stenosis. We analyzed the effect of the stress maneuver on Q, AVA, valve compliance (VC) and AVAproj. We also compared the proportion of patients with non-conclusive test (ΔQ<20%) between stress maneuvers. We computed the Akaike Information Criterion (AIC) to compare a linear with a saturating function for the Q-AVA-relation. RESULTS Q gradually increased from "PLR" to "Dmax" to "Dmax+PLR" (p<0.0001), while the number of non-conclusive tests concomitantly diminished from n=35 to n=3. The stress sequence increased AVA (p<0.001), but decreased AVAproj (p=0.006) and VC (p=0.005). In the pooled Q-AVA-data, the AIC-value was lower for the saturating (sigmoidal) model compared to the linear model fitting (-1593 versus -1504). CONCLUSION "Dmax+PLR" is capable of reducing the number of non-conclusive DSE tests. With increasing stress strength, the Q-AVA-relation progressively flattens, indicating saturation.