Prospective assessment of the frequency of low gradient severe aortic stenosis with preserved left ventricular ejection fraction: Critical impact of aortic flow misalignment and pressure recovery phenomenon

Summary Background The frequency of paradoxical low-gradient severe aortic stenosis (AS) varies widely across studies. The impact of misalignment of aortic flow and pressure recovery phenomenon on the frequency of low-gradient severe AS with preserved left ventricular ejection fraction (LVEF) has not been evaluated in prospective studies. Aims To investigate prospectively the impact of aortic flow misalignment by Doppler and lack of pressure recovery phenomenon correction on the frequency of low-gradient (LG) severe aortic stenosis (AS) with preserved LVEF. Methods Aortic jet velocities and mean pressure gradient (MPG) were obtained by interrogating all windows in 68 consecutive patients with normal LVEF and severe AS (aortic valve area [AVA] ≤ 1 cm 2 ) on the basis of the apical imaging window alone (two-dimensional [2D] apical approach). Patients were classified as having LG or high-gradient (HG) AS according to MPG  35 mL/m 2 or ≤ 35 mL/m 2 , on the basis of the 2D apical approach, the multiview approach (multiple windows evaluation) and AVA corrected for pressure recovery. Results The proportion of LG severe AS was 57% using the 2D apical approach alone. After the multiview approach and correction for pressure recovery, the proportion of LG severe AS decreased from 57% to 13% (LF-LG severe AS decreased from 23% to 3%; NF-LG severe AS decreased from 34% to 10%). As a result, 25% of patients were reclassified as having HG severe AS (AVA ≤ 1 cm 2 and MPG ≥ 40 mmHg) and 19% as having moderate AS. Hence, 77% of patients initially diagnosed with LG severe AS did not have “true” LG severe AS when the multiview approach and the pressure recovery phenomenon correction were used. Conclusions Aortic flow misevaluation, resulting from lack of use of multiple windows evaluation and pressure recovery phenomenon correction, accounts for a large proportion of incorrectly graded AS and considerable overestimation of the frequency of LG severe AS with preserved LVEF.