Pulse Wave Velocity, Systolic Hypertension and Vascular Calcification in Chronic Kidney Disease Patients
Pulse wave velocity (PWV) is the gold standard method for evaluating arterial stiffness non-invasively. It depends on the arterial wall structure and function but is mainly influenced by age-associated alterations and BP.17 Temmar et al. studied the temporal link between PWV and aortic and coronary calcifications in a cohort of 150 patients with different stages of CKD.18 They found that both vascular stiffness and vascular calcification appeared early in CKD patients. Age, mean arterial BP, diabetes and aortic calcification score were all independent determinants of increased PWV. The relationship between measures of arterial stiffness PWV and the extent of calcification in the coronary arteries was also examined by Haydar et al. in a small population of 66 haemodialysis patients.19 The mean age of the 55 patients was 56.4 years and the mean duration of dialysis was 65.4 months; they demonstrated that PWV is strongly related to the degree of EBCT-derived coronary artery calcium score in CKD patients. The next step in validating PWV as a useful tool for the risk assessment of CKD patients was to study the effect of pharmacological intervention. Clinical studies involving essential hypertension and CKD patients have shown that angiotensin-converting enzyme (ACE) inhibitors and calcium antagonists decreased aortic PWV to a large extent in response to BP lowering.20 The results indicate that independent of BP changes, survival was substantially better for those subjects whose aortic PWV decreased in response to decreased BP. Guerin et al. hypothesised that the PWV is partly dependent on BP.21 They evaluated if the changes in PWV in response to decreases in BP can predict mortality in dialysis patients. They showed that the loss of aortic PWV sensitivity to BP was predictive of adverse outcome, indicating that arterial stiffness is not only a risk factor contributing to the development of CV disease but also a marker of more advanced, less reversible arterial damage. Taken together, these results support the hypothesis that measurement of arterial parameters exploring both structural and functional properties, such as quantification of arterial calcium deposit and determination of PWV, could help in stratifying the risk but also in evaluating the risk reduction strategies by monitoring these arterial parameters under different drug regimens. Significant alterations of the aortic PWV appear at an early stage of the disease; mild-to-moderate renal insufficiency, an elevated stiffness of the central arteries seems to be significantly associated with a reduced creatinine clearance, independent of BP and other standard CV risk factors.22 These results suggest that alterations of the viscoelastic properties of the arterial wall are significantly connected to renal alterations, and that this association is present long before the appearance of ESRD and macrovascular complications.23
High BP and proteinuria are major factors in the progression of CKD.24 Weir et al. have evaluated whether PWV was associated with increased risk of proteinuria in CKD patients.24 Systolic BP was important as an explanatory factor for variations in proteinuria, whereas PWV incrementally accounted for a significant portion of variation in proteinuria beyond that explained by brachial artery systolic BP in diabetics but not in non-diabetic patients.