Passive Leg Raise Stress Echocardiography in Severe Paradoxical Low-Flow, Low-Gradient Aortic Stenosis

Background: Dobutamine stress echocardiography is used to increase transvalvular flow in patients with low-flow, low-gradient aortic stenosis (AS). Dobutamine fails to increase the stroke volume index (SVI) in one third of patients. The aim of this study was to test whether passive leg raise (PLR) added to dobutamine could increase SVI and transvalvular flow in patients with severe paradoxical low-flow, low-gradient AS. Methods: Forty-five patients with apparent severe low-flow, low-gradient AS on the basis of traditional measurements were included. Twenty-five were categorized as belonging to the paradox group (left ventricular ejection fraction [EF] >= 50%) and 20 to the low EF group (left ventricular EF < 50% or "classical" low-flow, low-gradient AS) for comparison. A four-step stress echocardiographic examination was performed: resting conditions (rest), PLR alone (PLR), maximal dobutamine infusion rate (Dmax), and a combination of Dmax and PLR (Dmax+PLR). Aortic valve area, SVI, and mean transvalvular flow were calculated using both the velocity-time integral (VTI) of left ventricular outflow tract and the Simpson method. Changes compared with rest and between the stress maneuvers were analyzed. Results: In the paradox group, compared with rest, left ventricular end-diastolic volume was significantly decreased with Dmax but was completely restored with Dmax+PLR (rest vs Dmax vs Dmax+PLR: 61 +/- 15 vs 49 +/- 18 mL [P < .001] vs 61 +/- 18 mL [P = NS]). The smallest increase in SVI in the paradox group was observed during Dmax (PLR vs Dmax vs Dmax+PLR: VTI, 38 +/- 4 mL/m(2) [P < .001] vs 36 +/- 7 mL/m(2) [P = .019] vs 41 +/- 7 mL/m(2) [P < .001]; Simpson, 28 +/- 6 mL/m(2) [P < .001], 21 +/- 7 mL/m(2) [P = NS], 27 +/- 7 mL/m(2) [P = NS]). Compared with Dmax, Dmax+PLR was able to achieve a higher SVI (VTI, 36 +/- 7 vs 41 +/- 7 mL/m(2) [P < .001]; Simpson, 21 +/- 7 vs 27 +/- 7 mL/m(2) [P < .001]) and transvalvular flow with the Simpson method only (179 +/- 56 vs 219 +/- 56 mL/sec, P < .001), as well as a higher mean gradient (34 +/- 10 vs 39 +/- 12 nnnn Hg, P = .003) and AVA with the Simpson method (0.64 +/- 0.21 vs 0.73 +/- 0.21 cm(2), P = .026). In the low EF group, only SVI VTI (31 +/- 8 vs 35 +/- 7 mL/m(2), P = .034) and mean gradient (29 +/- 12 vs 34 +/- 14 mm Hg, P = .003) were higher with Dmax+PLR. The proportion of patients with SVI VTI >= 35 mL/m(2) and increases of SVI VTI of >20% compared with rest was highest with Dmax+PLR in both groups. Conclusions: Dobutamine decreases preload in paradoxical low-flow, low-gradient AS. Adding PLR counteracts this effect, resulting in increased SVI and flow (in one method). The combined stress maneuver allowed reclassification of some patients from severe to moderate AS and may therefore be useful in selected cases in this population in which severity is uncertain.