Fig. 1

Aortic pulsed wave velocity (PWV) estimation from 4D flow CMR. a Shared pre-processing step for all aortic PWV (aoPWV) strategies: aortic 3D segmentation, positioning of cross-sectional planes perpendicular to the aortic centreline between the distal descending aorta (1st plane) and proximal ascending aorta (25th plane), extraction of the corresponding 25 mean velocity curves, as well as Di distances between the 1st and the ith planes along the centreline. Of note, mean velocity curves were interpolated with a 1-ms time step using a spline function. b For strategy 1 (S1), aoPWV was defined as the ratio of the distance (D₂₅) between the most distal (#1) and most proximal (#25) planes to the transit time (TT₂₅) estimated from the corresponding normalized velocity waveforms. Transit time estimation methods are described in Fig. 2. c For strategy 2 (S2), intermediate distances (Di) and transit times (TT_i) were estimated as in S1 between plane 1 and each successive plane (#i), until the proximal ascending aortic plane is reached. Such process provides the plot at the bottom, which was then linearly fitted (L: TT_i = a*D_i + b). aoPWV was equal to reciprocal of the slope (a). d For strategy 3 (S3), transit time estimation was not needed since aoPWV was defined from the parameters of the plane (P: a × distance+b × time + c × velocity + d = 0) used to fit the systolic upslope of the normalized velocity curves corresponding to the 25 aortic planes illustrated in panel a