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

Abstract

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 (DP 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) (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 .T ransvalvular pressure gradient and aortic valve area (AVA) are the standard indices to determine the haemodynamic severity of aortic stenosis (AS).1 2 However, a patient's physiological state can affect these indices and therefore the assessment of AS severity. Pressure gradients and AVA vary with transvalvular flow and flow-mediated forces.3-10 Valve resistance, % left ventricular stroke work loss (% LVSW loss) and the energy loss coefficient (ELCo) have been proposed as alternative indices of AS severity that may be less sensitive to transvalvular flow.7 11-21 However, this has not been corroborated in individual patients when transvalvular flow was altered using exercise or inotropic infusion. The impact of blood pressure (BP) on the assessment of AS severity has received less attention.2 Traditionally, low systolic BP (SBP) and a decreased pulse pressure have been considered signs of severe AS, whereas the presence of hypertension excluded severe AS. 22 However, recent data demonstrate that hypertension commonly coexists with and is a risk factor for AS. [23][24][25][26][27] Hypertension can lead to an underestimation of AS severity on physical examination. 22Furthermore, BP and systemic vascular resistance may influence the assessment of the haemodynamic severity.2 In a catheterisation study, Laskey et al 28 observed a decrease in transvalvular pressure gradient and a potential underestimation of AS severity when peripheral resistance was increased. Similarly, induction of hypertension in an animal model of supravalvular AS resulted in a decrease in pressure gradient and an increase in the area of the supravalvular stenosis. 29In contrast, pressure gradient increased and valve area decreased when systemic vascular resistance was increased in a...

Hypertension in aortic stenosis: More questions than answers

“…In an experimental model, in vitro, echocardiographic and hemodynamic assessment of the effect of hypertension on the AVA and transvalvular flow parameters showed no flow changes secondary to changes in afterload [29]. On the other hand, significant changes in afterload caused by drugs or physical activity can modify the LV function, the transvalvular gradient and the volume flow [31]. This effect was confirmed in vivo in a porcine heart model.…”

Discordance in Grading Methods of Aortic Stenosis by Pre-Cardiopulmonary Bypass Transesophageal Echocardiography

“…In patients with AS, AVA by the continuity equation is inversely related to blood pressure because of changes in transvalvular flow. 25 Thus, without controlling for the effects of general anesthesia, one would expect pre-CPB TEE AVA calculations to yield different values than preoperative TTE AVA calculations in the same patients. Although factors such as LVOT diameter underestimation and beat-to-beat variability in blood flow make AVA calculations prone to error, these problems affect both preoperative TTE and pre-CPB TEE and do not explain increased discordance during pre-CPB TEE.…”

Time to Treat Hypertension in Patients With Aortic Stenosis

“…Moreover, when determining the severity of AS and making decisions about the timing of valve replacement, it is important to recognize that systemic HTN can influence the assessment of AS severity (generally causing overestimation of severity; Figure). 17 After valve replacement is performed, there may be a greater tendency toward systemic HTN because of the increased flow from the relief of valvular afterload, which may mitigate the expected favorable effects of LV unloading with valve replacement and limit symptomatic improvement. For all these reasons, both before and after valve replacement, treatment of systemic HTN should be an important objective of medical therapy.…”