Noninvasive measurement of aortic pressure waveform by ultrasound
At present, the aortic pressure (Pa) waveform can only be measured invasively. In this paper, we describe a new noninvasive method of measuring Pa. The aortic diameter (Da) pulse waveform was measured noninvasively from the suprasternal fossa using an echo-tracking system that was applied to the anterior and posterior aortic wall echoes. To eliminate viscoelastic distortion, the measured Da was converted to an estimate of Pa, named Pβ, using the stiffness parameter β, which revealed the viscoelastic relationship between the vessel diameter and its internal pressure. Pβ was then compared with the Pa pattern that was measured directly. Eight patients with ischemic heart disease who had undergone cardiac catheterization were examined by this method. Results showed that (1) the Da and Pa waveforms were similar; (2) the Pβ waveform resembled the Pa waveform more closely than did the Da waveforms for a single cardiac cycle (r = 0.970); and (3) in particular, Pβ resembled Pa most closely during the upslope phase of the ejection period (r = 0.996). Our results suggest that the Pa waveform can be accurately estimated from noninvasive measurements by this method.