For the given filling pressure and systolic pressure, the ventricle's performance is known as Left ventricular contractility. The dP dt ratio gives the LV Contractility and it is determined using time interval between 1 and 3m/sec on MR velocity CW spectrum during isovolumetric contraction. Here is the Left Ventricular Contractility formula which helps you in the LV Contractility calculation on your own. LV Contractility formula requires isovolumetric contraction as the input.