Impact of blood pressure on the Doppler echocardiographic assessment of severity of aortic stenosis

Objective: To investigate the impact of blood pressure (BP) on the Doppler echocardiographic (Doppler-echo) evaluation of severity of aortic stenosis (AS). Methods: Handgrip exercise or phenylephrine infusion was used to increase BP in 22 patients with AS. Indices of AS severity (mean pressure gradient (ΔP_mean), aortic valve area (AVA), valve resistance, percentage left ventricular stroke work loss (% LVSW loss) and the energy loss coefficient (ELCo)) were measured at baseline, peak BP intervention and recovery. Results: From baseline to peak intervention, mean (SD) BP increased (99 (8) vs 121 (10) mm Hg, p<0.001), systemic vascular resistance (SVR) increased (1294 (264) vs 1552 (372) dyne x s/cm⁵, p<0.001) and mean (SD) transvalvular flow rate (Q_mean) decreased (323 (67) vs 306 (66) ml/s, p = 0.02). There was no change in ΔP_mean (36 (13) vs 36 (14) mm Hg, p = NS). However, there was a decrease in AVA (1.15 (0.32) vs 1.09 (0.33) cm², p = 0.02) and ELCo (1.32 (0.40) vs 1.24 (0.42) cm², p = 0.04), and an increase in valve resistance (153 (63) vs 164 (74) dyne x s/cm⁵, p = 0.02), suggesting a more severe valve stenosis. In contrast, % LVSW loss decreased (19.8 (6) vs 16.5 (6)%, p<0.001), suggesting a less severe valve stenosis. There was an inverse relationship between the change in mean BP and AVA (r= -0.34, p = 0.02); however, only the change in Q_mean was an independent predictor of the change in AVA (r = 0.81, p<0.001). Conclusions: Acute BP elevation due to increased SVR can affect the Doppler-echo evaluation of AS severity. However, the impact of BP on the assessment of AS severity depends primarily on the associated change in Q_mean, rather than on an independent effect of SVR or arterial compliance, and can result in a valve appearing either more or less stenotic depending on the direction and magnitude of the change in Q_mean.