The heart and the arterial system constantly interact with each other through forward travelling waves and reflected waves. Wave Intensity (WI) is calculated as the product of the derivatives of the simultaneously recorded blood-pressure changes and blood-flow-velocity changes. Wave Intensity can be obtained at an arbitrary point in the circulatory system.
Blood pressure change waveform is conventionally measured invasively. Hitachi has developed a system to calculate blood pressure change noninvasively and with a high level of accuracy. Based on the similarity of the cyclic blood pressure change and its simultaneous vessel diameter change, a blood pressure waveform is derived non-invasively. This non-invasive pressure waveform can then be analyzed further.
WI is a new hemodynamic index which is potentially useful for analyzing interaction of the cardiovascular system, including contraction and dilatation characteristics, influence of reflected waves from peripherals, interaction of elastic and resistance vessels and an index related to time.
WI is a new indicator of blood flow dynamics, which is expected to help pave the way for analysis of the interference between the heart and the arterial system.