Value of left ventricular ejection time percentage in the evaluation of severity of aortic stenosis: its usefulness in stress dobutamine echocardiography

Backgrounds The assessment of aortic stenosis (AS) is challenging especially in low flow, low ejection fraction conditions. Historically the prolongation of ejection time (ET) has been related to severity of AS but it relays on stroke volume (SV), heart rate and valvular and vascular loads but its use is limited when SV is reduced. According to Gorlin equation, ET is inversely related to aortic valve area (AVA), however in presence of low SV, ET could be in normal range despite reduced AVA. Objective Our aim was: 1) to verify if the difference between ET corrected by SV and measured ET is useful to assessing the severity of AS especially in low flow, low EF patients and 2) if this parameter could be useful during stress dobutamine echocardiography (SDE) to distinguish between true AS and pseudostenosis. Methods We retrospectively studied 234 patients (p), age average 67 ± 16 years with AS mild / moderate (AVA ≥ 1 cm2) 25 p and severe AS (AVA < 1 cm2) 209 p with Doppler echocardiography. SDE was performed in 17 p with low flow, low gradient, low ejection fraction. ET was measured as the time interval between the onset and the end of left ventricular outflow tract profile registered with PW in apical 5-chamber view. ET predicted (ETpre) for each SV was estimated from the formula of Harley et al. (J Clin Invest 1969;48:895-905): ETpre = 0.002 x SV + 0.106. The difference between ET measured (ETm) and ETpre which would express the degree of AS was calculated in two ways: as the difference in absolute values (ETm – ETpre) and as percentage of the difference (∆ ET %): ((ETm-ETpre)/ETpre) x 100. Statistical analysis was performed with Pearson correlation, Student´s t test and ROC curves. Results 1) ET difference and AVA. ETm was 330 ± 40 ms and ETpre 230 ± 40 ms (p<0.001). There was a logarithmic correlation (r ═ 0.60 p<0.001) between AVA and ∆ ET % . A ∆ ET % of 32 % had a sensitivity of 80 % and specificity of 72 % to predict AVA < 1 cm2 (AUC 0.832 - ROC curve). The correlation between AVA and ETm – ETpre was lower, although the correlation was statistically significant (r ═ 0.40 p<0.001). In 85 p who had an ET less than 320 ms (normal upper limit) a ∆ ET of 32 % had a sensitivity of 77 % and specificity of 66 % to predict an AVA < 1 cm2 (AUC 0.683 - ROC curve). 2) ∆ ET % in SDE. In 17 p with stress dobutamine echocardiography, 12 presented true AS and 5 pseudostenosis (AVA ˃ 1 cm2 after dobutamine infusion). There was not statistically significant difference between ∆ ET % in the two groups in basal stage but ∆ ET % decreased significantly from 5 gamma to 20 gamma in pseudostenosis group (table). Conclusions ∆ ET % would allow assessing the severity of AS with simple measurements such as ET and SV. ∆ ET % could be useful during SDE to differentiate between true AS and pseudostenosis from the early stages of the test.