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. 2021 Mar 11;8(1):G19–G59. doi: 10.1530/ERP-20-0035

Figure 12.

Figure 12

Worked example of the energy-loss index (ELI): From the image (A), the LVOT cross-sectional area can be calculated: LVOT CSA = π × (LVOTd ÷ 2)2 = 3.5 cm2. The cross-sectional area of the ST junction (STJ) depicted in image (B) is: STJ CSA = π × (STJ diameter ÷ 2)2 = 6.6 cm2. Using the CW trace in image (C), AV Vmax is 3.1 m/s; mean gradient 27 mmHg; AV VTI 55 cm. Using the PW trace in image (D), LVOT VTI is 14 cm. Aortic valve area using the continuity equation is: AVA = LVOT VTI ÷ AV VTI × LVOT CSA = 14 cm ÷ 55 cm × 3.5 cm2 = 0.9 cm2. After indexing for BSA (1.7 m2 in this patient), the AVAi is 0.51 cm2/m2. This is an example of low-gradient AS whereby both the AVA and AVAi suggest severe stenosis yet the AV Vmax and mean gradient only suggest moderate stenosis. The energy-loss index is defined as: ELI = (AVA × STJ CSA) ÷ (STJ CSA – AVA). ELI = (0.9 × 6.6) ÷ (6.6 – 0.9) = 1.04 cm2. Indexed for BSA = 0.61 cm2/m2. An ELI < 0.6 cm2/m2 is consistent with severe AS, therefore this patient has been re-classified as moderate AS when accounting for the pressure-recovery phenomenon.