This paper describes the study of an integrated system for the detection of the B-C-X characteristic points of impedance cardiography (ICG) signals, to evaluate the stroke volume of a patient. It compares a discrete-time digital approach and a continuous-time digital architecture, using a level-crossing Analog-to-Digital Conversion (LC-ADC). The results show that the measurement accuracy of the stroke volume, with a relative error between 9% and 13%, is sufficient for practical use and opens the opportunity for future fully integrated circuit solutions. This study also points out that, unlike ECG, the continuous-time digital approach does not bring any improvements for ICG-based systems.