Echocardiography Measurements

The continuity equation is useful in calculating valve areas in both stenotic 
and regurgitant lesions.

Left ventricular contractility can be measured by calculating a change in 

pressure in the ventricle during isovolumetric contraction phase (dp/dt).

Pressure half time (PHT) is the time taken for the peak early diastolic 

pressure gradient to drop to half its value. It is measured in milliseconds. 

It is useful in calculating the mitral valve orifice area, and is a commonly 

used tool to assess severity of aortic and mitral regurgitation. It is typically 

29% of the deceleration time (DT). In other words

PHT = 0.29 x DT

It has also been defined as the time interval from the maximum velocity 

(Vmax) to the point where the velocity drops to Vmax / √2. This figure 

should help

Pressure half-time is more useful with native valves than with prosthetic 

valves, as it can overestimate the orifice area of normal functioning 

prosthetic valves.

Pressure half-time is useful in calculating effective mitral valve area in 

mitral stenosis

                                                           MVA = 220 / PHT

For example, if the pressure half time is 280 ms, the mitral valve area is 

220 / 280 = 0.79cm2