Bargiotas Ioannis, Mousseaux Elie, Yu Wen-Chung, Venkatesh Bharath Ambale, Bollache Emilie, de Cesare Alain, Lima Joao A C, Redheuil Alban, Kachenoura Nadjia
Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Laboratoire d'Imagerie Biomédicale, F-75013, Paris, France.
INSERM, UMR 970, PARCC, F-75015, Paris, France.
J Cardiovasc Magn Reson. 2015 Jul 30;17(1):65. doi: 10.1186/s12968-015-0164-7.
Aortic pulse wave velocity (PWV), which substantially increases with arterial stiffness and aging, is a major predictor of cardiovascular mortality. It is commonly estimated using applanation tonometry at carotid and femoral arterial sites (cfPWV). More recently, several cardiovascular magnetic resonance (CMR) studies have focused on the measurement of aortic arch PWV (archPWV). Although the excellent anatomical coverage of CMR offers reliable segmental measurement of arterial length, accurate transit time (TT) determination remains a challenge. Recently, it has been demonstrated that Fourier-based methods were more robust to low temporal resolution than time-based approaches.
We developed a wavelet-based method, which enables temporal localization of signal frequencies, to estimate TT from ascending and descending aortic CMR flow curves. This method (archPWVWU) combines the robustness of Fourier-based methods to low temporal resolution with the possibility to restrict the analysis to the reflectionless systolic upslope. We compared this method with Fourier-based (archPWVF) and time domain upslope (archPWVTU) methods in relation to linear correlations with age, cfPWV and effects of decreasing temporal resolution by factors of 2, 3 and 4. We studied 71 healthy subjects (45 ± 15 years, 29 females) who underwent CMR velocity acquisitions and cfPWV measurements.
Comparison with age resulted in the highest correlation for the wavelet-based method (archPWVWU:r = 0.84,p < 0.001; archPWVTU:r = 0.74,p < 0.001; archPWVF:r = 0.63,p < 0.001). Associations with cfPWV resulted in the highest correlations for upslope techniques whether based on wavelet (archPWVWU:r = 0.58,p < 0.001) or time (archPWVTU:r = 0.58,p < 0.001) approach. Furthermore, while decreasing temporal resolution by 4-fold induced only a minor decrease in correlation of both archPWVWU (r decreased from 0.84 to 0.80) and archPWVF (r decreased from 0.63 to 0.51) with age, it induced a major decrease for the archPWVTU age relationship (r decreased from 0.74 to 0.38).
By CMR, measurement of aortic arch flow TT using systolic upslopes resulted in a better correlation with age and cfPWV, as compared to the Fourier-based approach applied on the entire cardiac cycle. Furthermore, methods based on harmonic decomposition were less affected by low temporal resolution. Since the proposed wavelet approach combines these two advantages, it might help to overcome current technical limitations related to CMR temporal resolution and evaluation of patients with highly stiff arteries.
主动脉脉搏波速度（PWV）随动脉僵硬度增加和年龄增长而显著升高，是心血管死亡率的主要预测指标。通常采用平板式眼压计在颈动脉和股动脉部位测量PWV（cfPWV）。最近，多项心血管磁共振（CMR）研究聚焦于主动脉弓PWV（archPWV）的测量。尽管CMR具有出色的解剖覆盖范围，能够提供可靠的动脉长度分段测量，但准确确定传输时间（TT）仍然是一项挑战。最近有研究表明，基于傅里叶的方法在低时间分辨率下比基于时间的方法更稳健。
我们开发了一种基于小波的方法，该方法能够对信号频率进行时间定位，以从升主动脉和降主动脉CMR血流曲线估计TT。此方法（archPWVWU）将基于傅里叶的方法对低时间分辨率的稳健性与将分析限制在无反射收缩期上升支的可能性相结合。我们将该方法与基于傅里叶的方法（archPWVF）和时域上升支方法（archPWVTU）在与年龄、cfPWV的线性相关性以及时间分辨率降低2倍、3倍和4倍的影响方面进行了比较。我们研究了71名健康受试者（45±15岁，29名女性），他们接受了CMR速度采集和cfPWV测量。
与年龄的比较显示，基于小波的方法相关性最高（archPWVWU：r = 0.84，p < 0.001；archPWVTU：r = 0.74，p < 0.001；archPWVF：r = 0.63，p < 0.001）。与cfPWV的相关性方面，无论是基于小波（archPWVWU：r = 0.58，p < 0.001）还是基于时间（archPWVTU：r = 0.58，p < 0.001）的上升支技术，相关性都最高。此外，当时间分辨率降低4倍时，archPWVWU（r从0.84降至0.80）和archPWVF（r从0.63降至0.51）与年龄的相关性仅略有下降，而archPWVTU与年龄的关系则大幅下降（r从0.74降至0.38）。
通过CMR测量，与应用于整个心动周期的基于傅里叶的方法相比，使用收缩期上升支测量主动脉弓血流TT与年龄和cfPWV的相关性更好。此外，基于谐波分解的方法受低时间分辨率的影响较小。由于所提出的小波方法结合了这两个优点，它可能有助于克服当前与CMR时间分辨率相关的技术限制，并有助于评估动脉高度僵硬的患者。
