Aortic Stenosis Suspected to Be Severe Despite Low Gradients
- aortic valve stenosis
- echocardiography, Doppler
- echocardiography, stress
- multidetector computed tomography
The American College of Cardiology/American Heart Association and European Society of Cardiology/European Association for Cardio-Thoracic Surgery guidelines generally recommend aortic valve replacement (AVR) in patients with severe aortic stenosis (AS) who have symptoms, have left ventricular (LV) systolic dysfunction, or undergo coronary artery bypass graft surgery or other heart surgery.1,2 These guidelines propose a peak aortic jet velocity >4.0 m/s, a mean transvalvular gradient >40 mm Hg, and an aortic valve area (AVA) <1.0 cm2 as the criteria to be used for the identification of severe AS. However, clinicians are often confronted with patients with discordant findings, the most frequent being the combination of a small AVA (<1.0 cm2) consistent with the presence of severe AS with a low mean gradient (<40 mm Hg) rather indicating the presence of moderate AS. This situation raises uncertainty regarding the actual severity of the stenosis as well as the potential indication of AVR if the patient is symptomatic.
Such discordance between AVA (small) and gradient (low) is often related to the presence of low LV outflow. Indeed, given that the pressure gradient is directly related to the squared function of transvalvular flow rate, even a modest decrease in flow rate can result in an important reduction in gradient and thus lead to an underestimation of stenosis severity. Hence, a patient with bona fide severe AS may indeed present with a low gradient if cardiac output is reduced. Moreover, this low-flow, low-gradient condition may occur in the context of either a reduced (ie, classical low flow) or preserved (ie, paradoxical low flow) LV ejection fraction (LVEF; Figure 1).3,4 However, such discordance may also be observed in patients with normal LVEF and cardiac output, in which case it may be attributable to measurement errors, a small …