Table 1.
Echocardiographic parameters for aortic stenosis severity assessment. AS = aortic stenosis; AV = aortic valve; AVA = aortic valve area; AVAproj = projected aortic valve area; AoA = cross-sectional area of the ascending aorta; BSA = body surface area; CSA = cross-sectional area; ELI = energy loss index; EOA = effective orifice area; LVOT = left ventricle outflow tract; N = number of instantaneous measurements; P = pressure; Qrest = flow at rest; sBP = systolic blood pressure; SVi = stroke volume index; v = velocity; VC = valve compliance; VR = velocity ratio; VTI = velocity time integral.
| Units | Formula/Method | Severe AS Cutoff | |
|---|---|---|---|
| AS jet velocity | m/s | Direct measure | >4.0 |
| Mean pressure gradient | mmHg | ΔP = Σ4v2/N | >40 |
| EOA | cm2 | Continuity equationAVA = (CSALVOT ∗ VTILVOT)/VTIAV | <1.0 |
| Indexed EOA | cm2/m2 | EOA normalized by BSA | <0.6 |
| Dimensionless index | VR = VLVOT/VAV | <0.25 | |
| Energy loss index | cm2/m2 | Indexed EOA accounting for ascending aorta ELI = [(AVA ∗ AoA)/AoA−AVA]/BSA | <0.5–0.6 |
| Valvuloarterial impedence | mmHg/mL/m2 | ZVA = (sBP + ∆Pnet)/SVi | 4.5–5 |
| Projected valve area at normal flow | cm2 | Estimated EOA at normal flowAVAproj = AVArest + VC ∗ (250−Qrest) | <1.0 |