Aortic pulse pressure is associated with carotid IMT in chronic kidney disease: report from Chronic Renal Insufficiency Cohort.

There is a substantial incidence and prevalence of chronic kidney disease (CKD) in the United States, with poor outcomes and profound economic implications.1 The burden of morbidity and mortality from CKD derives from the progression to end-stage renal disease, and the disproportionate risk of cardiovascular disease (CVD).2 Carotid intima-media thickness (IMT) has emerged as a noninvasive means to assess cardiovascular (CV) risk. An IMT measurement above the 95th percentile is predictive of coronary heart disease risk.3 Change in IMT in participants with CKD over 2 years has been associated with cardiovascular events.5 Measures of large artery stiffness are increasingly recognized to provide information about CV risk in certain populations. Pulse wave analysis (PWA) is a useful tool to study arterial wave reflection in the central circulation. Augmentation index (AI) measures the magnitude and timing of wave reflection. In very young, healthy individuals, the reflected wave returns to the central circulation after a longer time interval and arrives during diastole that augments coronary perfusion pressure. In health, the amplitude of the returning wave is relatively low because healthy elastic arteries dampen its magnitude. In disease states, such as hypertension, the arteries become stiffer resulting in a large magnitude of the reflected wave and an increased pulse wave velocity. Thus, the reflected wave will return to central circulation earlier during systole hereby increasing the cardiac workload. This contributes to left ventricular hypertrophy and reduces coronary perfusion pressure.6 Central aortic systolic pressure (C_SP) is an estimate of aortic systolic pressure derived from the radial artery waveform. Devices used in PWA often employ applanation tonometry of a peripheral artery and then, by means of a transfer algorithm, estimate C_SP and the aortic pulse pressure (C_PP).7 PWA provides prognostic information above and beyond that from traditional CV risk factors in the general population,8 but its significance in patients with CKD who are not on dialysis is limited.9 PWA measurements are noninvasive, easily made and well-suited to large epidemiological trials. PWA is a highly reproducible measurement in CKD.10 Central pressures are better predictors of atherosclerosis, as measured by carotid IMT and plaque, compared to traditional brachial blood pressures.11 Central pulse pressures (PPs) predict CVD outcomes in normal, hypertensive, and end-stage renal disease populations.12,13 Increased AI is associated with angiographic evidence of coronary artery disease in CKD.14 Although PWA and IMT measurements provide information about CV risk, little is known about their association among CKD patients. The radial artery tonometry procedures used in PWA are more easily and quickly performed, and seem better suited for epidemiology usage compared with carotid ultrasonography. Because carotid IMT and carotid plaque assessments, although technically difficult to obtain, are considered better measures of CV risk compared to PWA, we sought to determine how well common radial PWA parameters, and which ones in particular, correlated best with these more generally accepted parameters. We hypothesized that PWA would correlate with IMT and carotid plaque, which are established predictors of CVD. Further, we anticipated that all PWA-derived measures of large artery stiffness would not be equivalent in their prediction of carotid IMT. Thus, we sought to examine which of the PWA parameters, AI, C_SP or C_PP, best correlates with IMT and carotid plaque among patients with CKD.