Hemodynamics

TVI is similar to peak velocity. However, TVI may be more accurate. May see peak velocity given on the boards.

1. Determine stroke volume:

SV=LVOT area x LVOT TVI

1. CO=HR x SV

P=(4V₂)²P=pressureV=velocity To maintain flow continuity, flow speed must increase through a stenosis.In conjunction with this, the pressure drops in the stenosis

Area of a circle = ∏r²Therefore, LVOT area = ∏ x (1/2 LVOT diameter)²

Remember the TVI can be substituted for peak velocity

1.3cm²Remember that Peak velocity can be substituted for TVI.

Valve morphologyPeak and mean gradientsAortic valve area (Continuity equation and planimetry)Dimensionless index

This is the ratio between the LVOT velocity and AV velocity.When this ratio is <0.25, this is generally consistent with severe AS.

Doppler angle

• If it is not parallel to flow, it will underestimate the gradient

LVOT Doppler

• When AS exists, there is a zone of acceleration just before the aortic valve
• When the pulsed Doppler sample volume is obtained within this zone when obtaining the LVOT velocity, it will be flasely elevated
• Normal LVOT TVI is 18-22 cm

There is a temporal delay in the peripheral pressure.There is also a pressure “overshoot”These will lead to problems with aortic valve gradient.

This is a simultaneous LV, Ao, and FA tracing illustrating how erroneous the FA tracing is (temporal delay and pressure overshoot).

The peak to peak gradient is not simultaneous and is therefore not physiologic.