Introduction: To determine the true effective orifice area (EOA) in aortic stenosis (AS), ideally, a transvalvular volume flow rate (TVFR) of ≥250 ml/s is required. EOA is underestimated in patients with low-flow states; however, dobutamine stress echocardiography (DSE) cannot be utilized for all of them.
Hypothesis: We assessed the hypothesis that a novel method we developed using valve resistance can correctly estimate true EOA without DSE.
Methods and Results: We studied 324 patients (age 72 ± 12 years; 163 women) whose aortic valve EOA was calculated with echocardiography. TVFR was defined as stroke volume divided by ejection time. Valve resistance was calculated as the mean transvalvular pressure gradient multiplied by 1,333, with the product divided by TVFR. Regression curves were fitted for groups stratified by TVFR, with the data paired to EOA and valve resistance, identifying the curve of a TVFR ≥250 ml/s group (Figure left). Assuming that valve resistance is flow independent, we estimated true EOA (eEOA) based on the ideal EOA-valve resistance relationship using the valve resistance. In 38 patients who underwent DSE because of low-flow, low-gradient AS (EOA 0.79 ± 0.19 cm2, TVFR 182 ± 38 ml/s), eEOA calculated using a resting valve resistance correlated well with the DSE results (r = 0.876, Figure right).
Conclusions: Estimation of true EOA using aortic valve resistance is feasible without stress testing. In routine clinical echocardiography, our method would be useful to perceive the actual severity, even if low-flow, low-gradient AS.