Ambulatory arterial stiffness evaluation: A step forward in the management of hypertension

Arterial stiffness represents an independent risk factor for cardiovascular events.1 Several studies reported that increased pulse wave velocity (PWV), the gold standard for evaluating arterial stiffness, is associated with increased cardiovascular morbidity and mortality in both the general population2, 3 and in patients with hypertension.4-6 A meta-analysis of 17 longitudinal studies (n = 15 877) showed that each increase in PWV by 1 m/s is related with a 14% and 15% increase in cardiovascular events and cardiovascular mortality, respectively.1 Accordingly, current guidelines recommend the measurement of PWV to evaluate target-organ damage in patients with hypertension.7 However, the wider applicability of the evaluation of PWV is hampered by the cost and the limited availability of the appropriate equipment and by the rigorous methodology that is required to obtain valid measurements.8 In this context, the first results of the Vascular health Assessment Of The hypertensive patients (VASOTENS) Registry, which are reported in the current issue of the Journal, have potentially important implications for the management of hypertensive patients.9 In this study, 24-hour ambulatory blood pressure (BP) and arterial stiffness measurements were performed in 1342 patients followed up in 24 hypertension centers from 10 countries worldwide.9 Notable, recordings were successful in 89.4% of the patients.9 In addition to PWV, other indices of arterial stiffness, including augmentation index, central systolic BP, and central pulse pressure, were also measured over a 24-hour period.9 When measured with conventional applanation tonometry, these indices predict cardiovascular events independently of BP.10 Interestingly, PWV was lower during the night than during the day.9 However, this nocturnal decrease in PWV was less pronounced in older subjects, in males, and in patients with the metabolic syndrome.9 As expected, patients with hypertension had higher PWV than normotensive subjects.9 Notably, this difference was more pronounced during nighttime.9 Overall, these findings show that 24-hour measurement of arterial stiffness is feasible in large numbers of patients followed up in different healthcare settings worldwide. It is well established that 24-hour ambulatory BP measurements are more strongly related to cardiovascular risk than office BP measurements.11, 12 Accordingly, current guidelines recommend home or 24-hour ambulatory BP measurements, if feasible, to establish the diagnosis of hypertension.7 Therefore, since both arterial stiffness and BP can be evaluated simultaneously over 24 hours using a single device, it might be easier to incorporate the measurement of arterial stiffness in the everyday management of hypertensive patients. This strategy will improve risk stratification in this population and, conceivably, reduce cardiovascular morbidity. An interesting finding of the analysis of the baseline data from the VASOTENS Registry is that PWV decreases during nighttime and that this decrease is less pronounced in high-risk subjects, including the elderly, males, and patients with the metabolic syndrome. The lack of a nocturnal reduction in BP pressure has been consistently shown to predict cardiovascular events.11, 12 It is unclear whether an attenuated decrease in PWV during nighttime will also exert a detrimental cardiovascular effect. If this is shown in prospective studies, 24-hour measurement of arterial stiffness will be even more attractive than spot measurements as currently performed. Despite the practical advantages of 24-hour ambulatory measurement of arterial stiffness, a major limitation of this method is that there are no prospective studies that evaluated their association with cardiovascular morbidity and mortality in the general population or in hypertensive patients. Only one small study in 170 patients undergoing hemodialysis evaluated the predictive value of 24-hour ambulatory measurement of arterial stiffness and reported that 48-hour ambulatory PWV was independently associated with cardiovascular morbidity.13 However, several studies reported a strong correlation between 24-hour ambulatory and both tonometric and intra-arterial measurements of arterial stiffness.14-17 The follow-up of patients enrolled in the VASOTENS Registry is expected to provide useful data regarding the relationship between ambulatory arterial stiffness and cardiovascular events.9 In conclusion, 24-hour ambulatory measurement of arterial stiffness can be successfully implemented in everyday clinical practice. Given the increasing importance of 24-hour ambulatory BP measurements for the diagnosis of hypertension, simultaneous measurement of arterial stiffness provides a useful option for cardiovascular risk stratification in patients evaluated for the presence of hypertension. However, more data regarding the association between 24-hour ambulatory measurement of arterial stiffness and cardiovascular morbidity are needed before the wider application of this promising method. The authors report no specific funding in relation to this research and no conflicts of interest to disclose.