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Echocardiography Exam 2 Practice Test

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Which measurement is used to calculate the left ventricular outflow tract area for the continuity equation in assessing aortic stenosis?
Correct Answer:
Left ventricular outflow tract diameter
Explanation:
The measurement used to calculate the LVOT area in the continuity equation is the LVOT diameter. The cross-sectional area of the LVOT is derived from this diameter with the formula area = π(D^2)/4, because stroke volume equals LVOT area times the LVOT velocity-time integral (VTI). The LVOT diameter is measured in the parasternal long-axis view, inner-edge to inner-edge, just below the aortic valve, in systole. The LVOT velocity gives the VTI for flow, not the area. The aortic root diameter and the RVOT diameter aren’t used in this LVOT area calculation. Since the area scales with the square of the diameter, tiny measurement errors in the LVOT diameter can lead to large errors in the calculated aortic valve area.

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