The tall R on Electrocardiogram is the systole or heart pumping period, right after that is resting period or diastole and during this period the high precision software of ECP detecting the diastole and convey the pumping system to squeeze the lower limb and buttock from calf-thigh-buttock in extremely short sequence, lasting one-half of the duration of the diastole. The pumping period is the red line just before the peak on the T wave after R. The pumping push the blood forward and upward, increase pressure during diastole in coronary arteries.
Look at the longer and shorter interval of R-R on ECG, the pumping period remain after systole or right after heart pumps blood. Even though one with atrial fibrillation (AF), the high precision ECP will detect and squeeze accordingly under AF mode. This precision was not possible in those days, thanks to computer technology.