Aortic stiffness, an independent predictor of cardiovascular risk and all-cause mortality, can be estimated non-invasively by measuring carotid to femoral (aortic) pulse wave velocity (aPWV). The Vicorder device has been developed to measure aPWV with little operator training in a non-intrusive manner. The aim of this study was to assess the repeatability of aPWV measured with the Vicorder device and to compare aPWV values with those obtained using the SphygmoCor system. Vicorder and SphygmoCor aPWV was assessed in 122 subjects (53 ± 18 years, 46 male) using both the manufacturers' and a standardized approach. Vicorder aPWV measurement proved to be highly repeatable (within-subject coefficient of variation 2.8%). Transit time differed significantly between the two devices (mean difference 22±9 ms, Po0.001), independent of the different algorithms used to calculate transit time. However, aPWV was similar between the two devices (mean difference 0.31 ± 1.54 m s À1 , Po0.001) though with an inherent bias toward lower Vicorder aPWV values at high values of SphygmoCor aPWV. Bias was reduced by subtracting the additional femoral artery segment measured by the Vicorder device, also bringing the measure of transit time in closer agreement to SphygmoCor values (mean difference 5 ± 9 ms, Po0.001). Transit time values significantly differed between the two devices and the Vicorder device reported lower aPWV values at higher SphygmoCor values of aPWV. This difference in transit time and inherent bias was reduced when adjustment for the additional femoral artery segment measured by the Vicorder device was made.
Acute kidney injury after cardiac surgery (AKICS) is common. Previous studies examining the role that mean arterial pressure (MAP) during cardiopulmonary bypass (CPB) may have on AKICS have not taken into account how baseline central venous pressure (CVP) and mean perfusion pressure (MPP) (i.e. MAP − CVP) can influence its evolution. To assess whether the change in MPP to the kidneys (i.e. delta MPP or DMPP) during CPB compared to baseline is an independent predictor of AKICS. After ethical approval, a retrospective observational study was performed on all patients undergoing CPB between October 2013 and June 2015 at a university-affiliated hospital. Known risk factors for the development of AKICS were recorded, as were the MPP values at baseline and during CPB. From this, statistical modelling was performed to identify predictors of postoperative AKICS. 664 patients were identified. Analysis was performed on 513 patients after exclusion. On logistic regression, significant and independent predictors of AKICS included: d20DMPP (cumulative duration of MPP values during CPB that were 20% below baseline and exceeded three consecutive minutes) (P = 0.010); baseline CVP; age; pre-operative creatinine level; and left ventricular (LV) dysfunction (ejection fraction (EF) < 45%). On alternative modelling, the cumulative number of MPP values during CPB that were 10% below baseline was also independently associated with AKICS (P = 0.003). Modelling without taking into account CVP also supported this association. The duration of differences in perfusion pressure to the kidneys during CPB compared to baseline is an independent predictor of AKICS.
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