Area and gradient mismatch: The discordance of a small valve area and low gradients

While the clinical severity of aortic stenosis (AS) is based largely on symptoms, indications for surgical aortic valve replacement (SAVR) and/or transcutaneous (TAVR) rely upon calculated estimates of the hemodynamic significance and degree of valvular stenosis. Severe AS is defined as an aortic valve area (AVA) <1.0 cm² or indexed AVA <0.6 cm²/m², mean trans-valvular pressure gradient (ΔP) >40 mmHg, and/or peak trans-aortic velocity >4 m/s by Doppler echocardiography. Whether the above conditions must be met individually or collectively remains unclear. As noted, area/gradient match occurs when both the AVA and ΔP fall within the severe range. This may occur regardless of the presence of normal or abnormal ejection fraction and regardless of the presence or absence of low flow (defined as a stroke volume index on echocardiography <35 ml/m²). However, the AVA may be in the severe range, while the gradient may be in the non-severe range. This has been referred to as area/gradient mismatch and will be discussed further in this chapter.