Hermeling Evelien, Reesink Koen D, Reneman Robert S, Hoeks Arnold P G
Department of Biophysics, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, Maastricht, The Netherlands.
J Hypertens. 2008 Dec;26(12):2374-80. doi: 10.1097/HJH.0b013e328311cdd5.
Local pulse wave velocity, a direct measure of arterial stiffness, can be measured using the systolic foot of the pressure waveform as the time reference point. The accuracy and precision of systolic foot identification, which may be disturbed by early wave reflections, heavily affects pulse wave transit time measurements. We investigated within subjects the existence of early wave reflections and their interference with systolic foot identification.
Fourteen ultrasound-derived distension waveforms, spaced over 16.4 mm, were simultaneously recorded in the CCA 3 cm proximal of the bifurcation of 12 young subjects. The second derivatives of the distension waveforms were calculated to identify the systolic foot and an inflection point preceding systolic peak distension. Pulse wave transit time was calculated as the time difference between the most proximal and most distal time-point, using either the systolic foot or the inflection point. The time to reflection (DeltaTSF_IP) was defined as the time difference between the systolic foot and the inflection point.
Both transit times (TT SF and TT IP) could be determined with good intrasubject precision: 0.7 and 1.4 ms, respectively. The systolic foot is running forward, TT SF = 3.1 +/- 0.9 ms, whereas the inflection point appears to run backward, TT IP = -3.9 +/- 1.4 ms. DeltaTSF_IP was 44.3 +/- 8.8 ms.
Despite the good intrasubject reproducibility, confluence of incident and reflected waves disturbs identification and discrimination of the systolic foot and the inflection point, resulting in biased estimates. Therefore both points are unsuitable for local pulse transit time measurements in the common carotid artery.
局部脉搏波速度是动脉僵硬度的直接测量指标，可将压力波形的收缩期波谷作为时间参考点来进行测量。收缩期波谷识别的准确性和精确性可能会受到早期波反射的干扰，这对脉搏波传播时间的测量有很大影响。我们在受试者体内研究了早期波反射的存在及其对收缩期波谷识别的干扰。
在12名年轻受试者分叉处近端3 cm的颈总动脉中同时记录14个间隔16.4 mm的超声衍生扩张波形。计算扩张波形的二阶导数以识别收缩期波谷和收缩期峰值扩张之前的一个拐点。使用收缩期波谷或拐点计算脉搏波传播时间，即最近端和最远端时间点之间的时间差。反射时间（DeltaTSF_IP）定义为收缩期波谷与拐点之间的时间差。
两种传播时间（TT SF和TT IP）在受试者内的精确性都很好，分别为0.7 ms和1.4 ms。收缩期波谷向前移动，TT SF = 3.1 +/- 0.9 ms，而拐点似乎向后移动，TT IP = -3.9 +/- 1.4 ms。DeltaTSF_IP为44.3 +/- 8.8 ms。
尽管在受试者内具有良好的可重复性，但入射波和反射波的汇合干扰了收缩期波谷和拐点的识别与区分，导致估计有偏差。因此，这两个点都不适用于颈总动脉局部脉搏传播时间的测量。
