| Abstract: | Vascular calcification (VC) is a novel vascular risk factor strongly associated with mortality in dialysis patients.1,2 Although various explanations exist for this association, one mechanism is through alterations in pulse-wave velocity (PWV). Vascular calcification is associated with increased aortic PWV,3 which in turn is associated with raised central aortic systolic pressure (CASP) and reduced coronary perfusion.4,5 As a result, brachial pressure may significantly under- or over-estimate central pressure.6Not surprisingly therefore, central blood pressure parameters have been shown to predict hard cardiovascular endpoints (including mortality) better than concomitant brachial measurements.7-10 Whether vascular calcification is directly linked to central pressures is, however, unknown since there are many determinants of aortic stiffening other than calcification. Furthermore, a primarily damaged and stiff aorta may be the target for secondary deposition of calcium.11CASP can be calculated using applanation tonometry-derived peripheral pulse waveforms and associated software.12 This avoids the obvious disadvantages of invasive central pressure determination. The major disadvantage of standard techniques, however, is the one-dimensional static measurement that is obtained, with no information on ambulatory values or nocturnal dipping status.Loss of normal nocturnal systolic blood pressure dipping is prevalent in chronic kidney disease (CKD) and likely contributes to cardiovascular disease.13 Dipping, which can only be assessed using ambulatory monitoring techniques, correlates better with left ventricular mass index (LVMI) in end-stage renal disease than office-based blood pressure measurement.14,15There have been calls for the routine use of ambulatory blood pressure monitoring (ABPM) in clinical studies of CKD13,16 and indeed, for investigations into the utility of ambulatory CASP in clinical practice.17,18 Combining both ambulatory and central pressure measurements is an attractive strategy, but until recently has not been technically possible.A non-invasive wrist watch-like device, BPro with A-Pulse CASP software (HealthStats, Singapore) was recently approved by the US Food and Drug Administration (FDA: K072593) for the measurement of CASP as well as ambulatory blood pressure. It is a small, wrist watch-like, cuffless monitor which obtains radial pressure waveforms by applanation tonometry. BPro has the ability to measure ambulatory CASP and although not yet commercially available, the manufacturer is able to convert data into ambulatory CASP using the same software.As part of a recently published study on vascular calcification,19 we sought to prospectively evaluate whether the presence of vascular calcification had any relationship with ambulatory CASP in our young CKD-5D cohort using the BPro® radial pulse-wave acquisition device. We also sought to determine the utility of inter-dialytic office brachial and central blood pressure measurements in predicting ambulatory parameters. |
