Development of a non-invasive real-time measurement system of wave intensity

Time-normalized wave intensity (WI) is a new hemodynamic index, which is defined as (dP/dt)(dU/dt) at any site of the circulation, where dP/dt and dU/dt are the time derivatives of blood pressure and velocity, respectively. WI provides information about the dynamic behavior of the heart and vascular system and their interaction. We have developed a new real-time measurement system for obtaining WI based on a conventional color Doppler system. The blood pressure waveforms were obtained non-invasively from the arterial diameter-change waveforms by an echo-tracking method. Using a 7.5 MHz linear array probe, we obtained carotid arterial WI, and analyzed the characteristics of the heart and vascular interactions. The results suggest that the system has great potential for clinical usefulness