Atherosclerosis is a progressive chronic arterial disease characterised by atheromatous plaque formation in the intima of the arterial wall. Several invasive and non-invasive imaging techniques have been developed to detect and characterise atherosclerosis in the vessel wall: anatomic/structural imaging, functional imaging and molecular imaging. In molecular imaging, vascular cell adhesion molecule-1 (VCAM-1) is a promising target for the non-invasive detection of atherosclerosis and for the assessment of novel antiatherogenic treatments. VCAM-1 is an adhesion molecule expressed on the activated endothelial surface that binds leucocyte ligands and therefore promotes leucocyte adhesion and transendothelial migration. Hence, for several years, there has been an increase in molecular imaging methods for detecting VCAM-1 in MRI, PET, SPECT, optical imaging and ultrasound. The use of microparticles of iron oxide (MPIO), ultrasmall superparamagnetic iron oxide (USPIO), microbubbles, echogenic immunoliposomes, peptides, nanobodies and other nanoparticles has been described. However, these approaches have been tested in animal models, and the remaining challenge is bench-to-bedside development and clinical applicability.

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Background Central blood pressure (cBP) is a better predictor of the damage caused by hypertension in comparison with peripheral blood pressure (pBP). Although challenging to measure, numerous devices are trying to reliably estimate cBP non-invasively. Pulse wave velocity (PWV) is another important independent cardiovascular risk factor. Aim We sought to deploy a new validation method using a high-fidelity pressure wire as the invasive gold standard measurement for sphygmomanometer devices estimating cBP. Moreover, we invasively calculated the PWV to investigate its relationship to the non-invasively estimated cBP. Methods In 50 patients requiring a cardiac catheterization, we measured the blood pressure in the ascending aorta (AAo) with a fluid-filled (FF) guiding catheter (NaCl 0,9%). We compared these values with the results derived simultaneously with a novel sphygmomanometer that estimates cBP from the analysis of brachial artery suprasystolic pressure waves, based on the pressure-wave propagation of a water-hammer acoustic model. This was measured on the left arm with the BP+ device from USCOM Pty Ltd (Sydney, NSW, Australia) while the catheterization was performed via the right radial artery. On 14 of these patients so far, we placed a 0.014" high-fidelity pressure wire in the AAo to measure cBP, when it was clinically indicated to evaluate one or more coronary stenosis by Fractional Flow Reserve (FFR). Ultimately, the wire was pulled back into the humeral artery (HUM). PWV was then calculated from the length of the pullback and the time delay between AAo and HUM pulses by gating to the R-wave of the ECG for both measurements, using MatLab software. Results Bland-Altman analysis of the sphygmomanometrically estimated cBPsys and the measured one by a FFR wire (left on figure) demonstrates less scatter than with the FF catheter (right). The mean difference with the sphygmomanometrically derived cBPsys was −1.2±4.7 mmHg (CI95%: −3.8; 1.8) for the FFR wire and 6.0±9.8 mmHg (CI95%: 3.2; 8.9) for the FF catheter. Central diastolic and mean BP were both overestimated by the sphygmomanometer, with respectively −7.8±6.8 mmHg (CI95%: −11.4; −4.2) and −5.5±6.1 mmHg (CI95%: −8.6; −2.3) compared to the FFR wire and −10.3±6.7 mmHg (CI95%: −12.2; −8.3) and −5.5±6.5 (CI95% : −7.3; −3.6) for the FF catheter. The average PWV was 7.0±1.4 m/s. No significant relationship of PWV and cBP was identified (p=0.189). The PWV was 0.8 m/s lower in patients with only one cardiovascular risk factor versus more than one, but without reaching statistical significance. cBPsys measured. A. FFR; B. FluidF vs BP+ Conclusions Using a FFR wire in the AAo as a high-fidelity pressure reference, we demonstrated that cBPsys derived from this new sphygmomanometer was accurate, with a non-significant bias (<5mmHg) and high precision (standard deviation <8mmHg) as recommended, criteria not met using the FF guiding catheter measurements. PWV measurements were also easily obtained from the FFR wire method.

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