Wave intensity analysis in the great arteries — What has been learnt during the last 25 years? Part 1

Wave intensity analysis (WIA) was introduced 25 years ago for the study of arterial wave propagation. The mathematical derivation of the method is complex, but the results are simple to use and WIA has since been established as a valuable technique for investigating the cardio-arterial interaction. WIA has several advantages; the most important of them is that it is a time-domain technique, which enables the direct association between waves and events during the cardiac cycle. Further, WIA allows for the separation of the measured pressure and velocity waveforms, and derived wave intensity, into their forward and backward directions, and also provides a means for the determination of the arrival time of reflected waves to the measurement site. This powerful technique has been used in several locations in the vascular system for investigating a wide range of physiological and clinical questions, but this review will focus on the clinical application of WIA, as demonstrated from in vivo and clinical studies in the aorta, pulmonary arteries and pulmonary veins