Step 1: Obtain a PWD the VTI of the LVOT. The dp/dt is the rate of pressure change using the 4V2 formula over time during isovolumic contraction.  During isovoumic contraction the pressure dramatically increases.   To measure the RATE of the pressure increase, a mitral regurgitant jet is required.  The time for the pressure to increase where the velocity of the mitral regurgitant jet changes from 1 m/sec (4 mmHg) to 3 m/sec (36 mmHg) is the dp/dt.  This 32 mmHg pressure change occurs before the aortic valve opens and before significant left ventricular volume has been ejection. The pressure difference divided by the time difference will yield the dp/dt.  The rate of the dp/dt is an indication of the contractility of the left ventricle as a whole.