Hemodynamic Classifications of Aortic Stenosis and Relevance to Prognosis

Abstract

Hemodynamic classifications of aortic valve stenosis (AS) have important prognostic implications. In normal flow state, severe AS is defined as peak aortic velocity ≥ 4.0 m/s, mean transaortic gradient (MG) ≥ 40 mmHg, and aortic valve area (AVA) < 1.0 cm 2 . However, numerous studies have shown that severe AS (based on AVA < 1.0 cm 2 ) with low gradient (MG < 40 mmHg) is prevalent due to low flow state, in the setting of reduced and preserved left ventricular ejection fraction (LVEF). Thus, the hemodynamic classifications of AS with AVA < 1.0 cm 2 were expanded to include the transvalvular flow state and pressure gradients. These flow-gradient patterns include normal flow/very high gradient, normal flow/high gradient, low flow/high gradient, low flow/low gradient with reduced LVEF, low flow/low gradient with preserved LVEF, and normal flow/low gradient. Among these, the low-gradient AS subgroups are challenging, particularly to differentiate true-severe AS (where aortic valve replacement is necessary) and pseudo-severe AS (where conservative management is recommended). Additional diagnostic studies such as dobutamine stress echocardiography and/or cardiac computed tomography, as well as other parameters such as projected AVA and/ or valvuloarterial impedance may be helpful. This chapter will review diagnostic approaches and prognostic implications of different AS subtypes.