Projected aortic valve area reflects true severity in patients with paradoxical low-flow low-gradient severe aortic stenosis: a Multicenter Aortic Stenosis Assessment (MASA) study

Background: We hypothesized a subset of patients with paradoxical low-flow, low-gradient (PLFLG), severe aortic stenosis (AS) despite preserved left ventricular ejection fraction (LVEF) might be pseudo-severe AS due to low-flow rate, and the measurement of projected aortic valve area (AVAproj) could discriminate from true-severe to pseudo-severe AS. Methods: Graded dobutamine or ergometer stress echocardiography was performed in 25 patients with PLFLG severe AS (AVA≤1.0cm2; stroke volume index≤35ml/m2; mean pressure gradient (PG) ≤40mmHg). AVA calculated by the continuity equation was plotted against transvalvular flow rate (Q) at each stage; valve compliance (VC) was derived as the slope of the regression line fitted to the AVA versus Q plot. Projected AVA was calculated: AVAproj = AVArest + VC × (250 – Qrest). Results: Peak velocity (PV), mean PG and AVA gradually increased during stress protocol (all p<0.001). Twelve patients (48%) revealed AVAproj <1.0cm2, and 13 patients (52%) had AVAproj ≥1.0cm2. Although LV volumes and LVEF were not differrent, patients with AVAproj <1.0cm2 had a higher PV (3.8±0.4 vs. 3.2±0.4m/s) and mean PG (34±6.3 vs. 23±4.8mmHg, all p<0.01) and smaller AVA (0.66±0.16 vs. 0.88±0.16cm2, p<0.01) compared to those with AVAproj ≥1.0cm2. Baseline PV ≥3.5m/s, mean PG ≥28.5mmHg, and left atrial volume ≥46.7ml predicted AVAproj <1cm2 with the sensitivity of 83%, 83%, 83% and the specificity of 91%, 83%, 75%, respectively (Figure). Conclusions: Half of patients with PLFLG severe AS revealed pseudo-severe AS. Stress echocardiography is useful for determining the true severity of PLFLG AS.