Time relationship between the ECG, dZ and dZ/dt waveforms. The more characteristic points of the dZ/dt waveform are identified as B, which is the opening moment to the aortic valve (identified as the local minima before the C point). The C is the maximum blood flow in the left ventricle (dZ/dtmax). The X reveals the closing of aortic valve (identified as local minima after C point) and the LVET (Left-Ventricular Ejection Time) is the time interval between the opening and closure of the aortic valve, i.e., the interval between the points B and X.