Preload Stress Echocardiography
A New Tool to Confirm Severity of Low-Gradient Aortic Stenosis
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Low-Gradient Aortic Stenosis: A Challenging Entity
Low-gradient aortic stenosis (LGAS) is a challenging entity from both a diagnostic and therapeutic standpoint. LGAS is characterized by the concomitance of a small aortic valve area ([AVA] <1.0 cm2; consistent with severe stenosis) with a low gradient (<40 mm Hg; consistent with nonsevere stenosis) at echocardiographic examination. This discordant grading situation raises an uncertainty about the severity of the stenosis and thus the indication of aortic valve replacement (AVR). There are 3 main types of LGAS: (1) classical low-flow LGAS with reduced ejection fraction (LVEF); (2) paradoxical low-flow LGAS with preserved LVEF; and (3) normal-flow LGAS (Figure).1,2 In the first 2 types, the LGAS pattern is because of the presence of a low-flow state, which is defined in the guidelines as a stroke volume index <35 mL/m2.3,4 In normal-flow LGAS, the stroke volume index is normal, but the mean transvalvular flow rate (ie, stroke volume divided by LV ejection time) may nonetheless be low (<200 mL/s) because of prolonged systolic duration.1,2 Normal-flow LGAS may also occur as a result of reduced arterial compliance, which may dampen the gradients despite normal stroke volume and mean transvalvular flow.5 Several studies and meta-analyses have reported that AVR is associated with improved survival in patients with LGAS.1,2,6,7 In the guidelines for the management of valvular heart diseases,3,4 AVR is recommended (class I or IIa) in symptomatic patients with low-flow LGAS after confirmation of the presence of severe stenosis (Figure). The 2017 European Society of Cardiology/European Association for Cardio-Thoracic Surgery guidelines also mention that the stenosis is most likely not severe in patients with normal-flow LGAS, but they do not exclude the use of additional tests to confirm stenosis severity …