Fig 1.
The sketch of the in vitro model.
A and B, the two points chosen for the pulse wave velocity measurement; C, the water tank; D, a piece of sponge; E, the homogeneous rubber tubing; F, the perfusion pump; G, the pressure transducer; H, the ultrasound system; I, the linear array transducer. The pulse wave transit time between point A and B could be obtained by respectively recording the flow spectrum at point A and point B. The PWV of part A-B could be calculated as the distance between A and B could be easily measured. The local PWV of a short segment at the middle of point A and B could be measured using our method. And these two PWVs should theoretically be equal. PWV, pulse wave velocity.
Fig 2.
The methodology of the in vitro study.
Panel A, the PWVA-B measurement, the top panel was the two dimensional echocardiographic imaging. The velocity spectra recorded at point A and B by pulse wave Doppler were displayed at the middle and bottom, respectively. The pressure curve recorded by the pressure transducer was shown under each spectrum. The time delay between the transducer and point A and B were respectively measured by foot detection using the intersecting tangent method (125ms and 184ms). Thus the transit time between A and B could be calculated as 184−125 = 59ms. Panel B, the local PWVM measured by the DPWD method, the simultaneously recorded dual velocity spectra were shown. The transit time between these two sites (9ms) was measured by wave foot detection using the intersecting tangent method. PWVA-B, pulse wave velocity between point A and B. DPWD, dual pulse wave Doppler; PWVM, pulse wave velocity at the middle of point A and B.
Table 1.
The PWV measurements by the in vitro model.
Fig 3.
The reproducibilities of the PWV measurements in the in vitro experiment.
Intra- (A, B) and inter-observer (C, D) variability of PWVA-B, intra- (E, F) and inter-observer (G, H) variability of PWVM were demonstrated by Bland-Altman plots and linear regression analysis, respectively. Abbreviations as in Fig. 2.
Table 2.
The reproducibility of the PWV measurements in vitro and in vivo studies.
Fig 4.
A representative local PWV measurement in a healthy subject.
In the upper part, the two dimensional echography showed the upstream sample volume 1 and downstream sample volume 2 and their exact distance could be measured. The Doppler simultaneous velocity spectra were shown at the lower part. The transit time between these two sites was measured (8ms). LCCA, left common carotid artery; PWV, pulse wave velocity.
Table 3.
The common characteristics of the participants in the in vivo study.
Fig 5.
Intra- and inter-observer variability of the local PWV measurements in vivo.
Intra- (A, B) and inter- (C, D) observer variability of local PWV measurements in healthy subjects (HS), intra- (E, F) and inter- (G, H) observer variability in hypertension patients (HP) were demonstrated by Bland-Altman plots and linear regression analysis, respectively.