Ambulatory arterial stiffness index derived from 24-hour ambulatory blood pressure monitoring

We hypothesized that 1 minus the slope of diastolic on systolic pressure during 24-hour ambulatory monitoring (ambulatory arterial stiffness index [AASI]) might reflect arterial stiffness. We compared AASI with established measures of arterial stiffness and studied its distribution in Chinese and European populations. We used 90207 SpaceLabs monitors and the SphygmoCor device to measure AASI, central and peripheral pulse pressures, the central (CAIx) and peripheral (PAIx) systolic augmentation indexes, and aortic pulse wave velocity. In 166 volunteers, the correlation coefficient between AASI and pulse wave velocity was 0.51 (P<0.0001). In 348 randomly recruited Chinese subjects, AASI correlated (P<0.0001) with CAIx (r=0.48), PAIx (r=0.50), and central pulse pressure (r=0.50). AASI increased with age and mean arterial pressure but decreased with body height. Both before and after adjustment for arterial wave reflections by considering height and heart rate as covariates, AASI correlated more (P<0.0001) closely with CAIx and PAIx than 24-hour pulse pressure. Among normotensive subjects, the 95th percentile of AASI was 0.55 in Chinese and 0.57 in 1617 Europeans enrolled in the International Database on Ambulatory Blood Pressure Monitoring. The upper boundary of the 95% prediction interval of AASI in relation to age ranged from 0.53 at 20 years to 0.72 at 80 years. In conclusion, AASI is a new index of arterial stiffness that can be easily measured under ambulatory conditions. Pending additional validation in outcome studies, normal values of AASI are probably <0.50 and 0.70 in young and older subjects, respectively.     

高血压患者动态动脉僵硬指数与血压变异性的关系

目的探讨高血压患者动态动脉僵硬指数(AASI)与血压变异性(BPV)的关系。方法入选2009-03-2011-10中国医科大学附属第一医院就诊的高血压患者119例,所有患者均行24h动态血压监测。AASI定义为1减去24h舒张压和收缩压的回归系数。依据AASI水平,分为4组:AASI<0.30、0.30～<0.41、0.41～<0.52、≥0.52。结果相关性分析显示,AASI分别与年龄(r=0.301,P<0.01)、24h收缩压(r=0.276,P=0.001)、白昼收缩压(r=0.225,P=0.008)、夜间收缩压(r=0.366,P<0.01)、24h脉压(r=0.510,P<0.01)、24h收缩压标准差(r=0.297,P=0.001)呈正相关,而与24h舒张压标准差(r=-0.256,P=0.002)、24h平均心率标准差(r=-0.205,P=0.017)及24h平均动脉压标准差(r=-0.202,P=0.017)呈负相关。多元线性逐步回归分析显示,AASI与24h脉压和24h收缩压标准差呈正相关(β=0.321,β=0.725,均P<0.01),与24h舒张压标准差和24h平均动脉压标准差呈负相关(β=-0.428,β=-0.346,均P<0.01)。结论 AASI与BPV密切相关。     

Ambulatory arterial stiffness index: rationale and methodology

OBJECTIVES: Increased arterial stiffness is associated with the development of cardiovascular disease and may even predict its development at an early stage. Increased pulse pressure is seen as a marker of increased arterial stiffness and can be readily measured by ambulatory blood pressure monitoring. We propose another surrogate measure of arterial stiffness derived from ambulatory blood pressure monitoring that may predict cardiovascular mortality over and above pulse pressure, namely, the dynamic relationship between diastolic and systolic blood pressure over 24 h--the ambulatory arterial stiffness index. METHODS: Using all blood pressure readings over the 24-h period from 11 291 (5965 women; mean age 54.6 years) patients referred for ambulatory blood pressure monitoring to a blood pressure clinic, diastolic blood pressure was plotted against systolic blood pressure, and the regression slope was calculated; ambulatory arterial stiffness index was defined as one minus this regression slope. RESULTS: Both ambulatory arterial stiffness index and pulse pressure were higher in women (0.42 vs. 0.40 and 57.0 vs. 55.3 mmHg, respectively). For the entire group, the correlation between ambulatory arterial stiffness index and pulse pressure was 0.5. CONCLUSIONS: Ambulatory arterial stiffness index is a new measure that is readily available from ambulatory blood pressure monitoring and may provide added prognostic information for cardiovascular outcome.     

Ambulatory arterial stiffness index: determinants and outcome

OBJECTIVES: We hypothesized that one minus the slope of diastolic on systolic blood pressure in individual 24-h ambulatory blood pressure recordings (ambulatory arterial stiffness index) might reflect arterial stiffness and predict cardiovascular mortality. METHODS: In volunteers and a population recruited in China, we studied concordance between ambulatory arterial stiffness index and established indexes of arterial stiffness. We assessed the predictive value of ambulatory arterial stiffness index in relation to cardiovascular outcome in Irish hypertensive patients. RESULTS: In 166 healthy volunteers, aged 22-83 years, the correlation coefficient between ambulatory arterial stiffness index and pulse wave velocity was 0.51 (P<0.001). In 348 randomly recruited Chinese, the correlations between ambulatory arterial stiffness index and both the central and peripheral systolic augmentation indexes were significantly stronger than those for 24-h ambulatory pulse pressure, particularly in study participants younger than 40 years. Among normotensive participants, the 95th percentile of the ambulatory arterial stiffness index was 0.55 in 234 Chinese and 0.57 in 1617 Europeans enrolled in the International Database on Ambulatory Blood Pressure Monitoring. The upper boundary of the 95% prediction interval of the ambulatory arterial stiffness index in relation to age ranged from 0.53 at 20 years to 0.72 at 80 years. In 11 291 patients enrolled in the Dublin Outcome Study, both ambulatory arterial stiffness index and 24-h ambulatory pulse pressure significantly predicted cardiovascular mortality. Ambulatory arterial stiffness index was a strong predictor of fatal stroke in normotensive participants, whereas pulse pressure better predicted heart attack in hypertensive patients. CONCLUSION: Ambulatory arterial stiffness index is a novel measure of arterial stiffness, which can be readily determined from ambulatory blood pressure recordings and which independently predicts cardiovascular mortality.     

Ambulatory arterial stiffness index or pulse pressure: which correlates better with arterial stiffness in resistant hypertension?

The ambulatory arterial stiffness index (AASI) is a recently proposed index derived from 24-h ambulatory blood pressure monitoring (ABPM) for the evaluation of arterial stiffness. In this cross-sectional study we investigated whether AASI reflects arterial stiffness in patients with resistant hypertension by comparing AASI and ambulatory pulse pressure (PP) with aortic pulse wave velocity (PWV), a measure of arterial stiffness, in 391 resistant hypertensives. Clinical, laboratory and echocardiographic variables, 24-h ABPM and aortic PWV (measured using the Complior device) were obtained. AASI was calculated as 1--the regression slope of 24-h diastolic on systolic blood pressure (BP). Statistical analysis involved single and multiple linear regressions to assess the correlations between the two ABPM variables and PWV, both unadjusted and adjusted for potential confounders (age, gender, body height, presence of diabetes, 24-h mean arterial pressure [MAP], heart rate, and nocturnal BP reduction). Ambulatory PP and aortic PWV were independently associated with age, gender, presence of diabetes, and 24-h MAP, whereas AASI was associated with age, diabetes, and nocturnal diastolic BP reduction. PP showed stronger unadjusted (r=0.39, p<0.001) and adjusted (r=0.22, p<0.001) correlations with aortic PWV than AASI (r=0.12, p=0.032 and r= -0.04, p=0.47, respectively). In the analysis of subgroups stratified by gender, age, presence of atherosclerotic diseases and diabetes, dipping pattern, and ambulatory BP control, the superiority of PP over AASI was apparent in all subgroups. In conclusion, 24-h ambulatory PP was better correlated to arterial stiffness, as evaluated by aortic PWV, than the novel AASI, in patients with resistant hypertension.     

Blood pressure variability and arterial stiffness

Blood pressure variability (BPV) is defined by the standard deviation of a given sample of population of normotensive or hypertensive subjects. Recent studies have suggested that this parameter might constitute a cardiovascular risk factor. Reduction of blood pressure variability could be an important purpose of anti-hypertensive treatment, as suggested from experimental studies. In a double-blind controlled investigation, the thiazide compound indapamide was compared to placebo, to the angiotensin blocker candesartan and to the calcium-entry blocker amlodipine for 12 weeks treatment. The 3 drugs reduced significantly and identically blood pressure. Only indapamide and amlodipine reduced significantly BPV. This study was the first to demonstrate the interest of BPV in the setting of a double-blind, placebo controlled, trial.     

Ambulatory arterial stiffness index predicts stroke in a general population

OBJECTIVE: The ambulatory arterial stiffness index (AASI) can be computed from individual 24-h blood pressure recordings. METHODS: We investigated the prognostic value of AASI and 24-h pulse pressure in a random sample of 1829 Danes, aged 40-70 years. We adjusted for sex, age, body mass index, mean arterial pressure, smoking, diabetes, ratio of total to high-density lipoprotein cholesterol, and history of cardiovascular disease with Cox regression. RESULTS: Over a median follow-up of 9.4 years, incidences of fatal and nonfatal endpoints were 40 for stroke, 150 for coronary heart disease, and 212 for cardiovascular events. In fully adjusted models, the hazard ratios associated with 1 SD increase (0.14 U) in the AASI were 1.62 (95% confidence interval, 1.14-2.28; P = 0.007) for stroke, 0.96 (0.80-1.14; P = 0.62) for coronary heart disease, and 1.06 (0.91-1.23; P = 0.49) for cardiovascular events. None of these ratios reached significance for pulse pressure (P > 0.47). The AASI still predicted stroke after excluding individuals with previous cardiovascular disease or after adjustment for systolic and/or diastolic blood pressure instead of mean arterial pressure. CONCLUSIONS: In a randomly recruited European population, the AASI was a strong predictor of stroke, beyond traditional cardiovascular risk factors, including the mean arterial pressure and pulse pressure.     

Ambulatory arterial stiffness index is not a specific marker of reduced arterial compliance

Ambulatory arterial stiffness index (AASI), a measure based on the relative behavior of 24-hour systolic and diastolic blood pressure (BP), has been suggested as a marker of arterial stiffness and a predictor of cardiovascular mortality. However, a narrow range of diastolic BP values over the 24 hours tends to flatten the regression slope and to artificially increase AASI. We explored the possible influence of different ranges of 24-hour diastolic BP fluctuations, such as those related to nocturnal BP fall, on AASI, and on its relationship with target organ damage. In 515 untreated hypertensive patients, AASI was directly related to age (r=0.30) and 24-hour systolic BP (r=0.20), whereas it was inversely related with nocturnal systolic and diastolic BP reduction (r=-0.28 and -0.46, respectively; all P<0.001). A direct relationship was found between AASI and left ventricular mass index (r=0.17; P<0.001), but this relation was no longer significant after adjustment for age, sex, body mass index, daytime systolic BP, and day-night systolic BP reduction (all P<0.05). AASI was directly related to carotid-femoral pulse wave velocity, an intrinsic measure of aortic stiffness (r=0.28; P<0.001), but no independent relation was found in a multiple linear regression. Our conclusions are as follows: (1) AASI is strongly dependent on the degree of nocturnal BP fall in hypertensive patients; (2) there is no significant relation between AASI and left ventricular mass after proper adjustment for confounders; and (3) the relation between AASI and a widely accepted measure of aortic stiffness, such as pulse wave velocity, is weak and importantly affected by other factors.     

Self–measured (blood pressure) arterial stiffness index: A promising new measure of arterial stiffness

Increased arterial stiffness is predictive of increased cardiovascular risk. The ambulatory arterial stiffness index is a new measure derived from 24–hour ambulatory blood pressure (BP) monitoring. We retrospectively studied 59 consecutive patients, (36 females; age 62 ± 12 years), evaluated for hypertension in an academic cardiology practice. All had eight or more self–measured BP recorded over a period of 2 through 8 weeks while stable. The self–measured arterial stiffness index (SMASI) was calculated according to the same formula as the ambulatory arterial stiffness index, 1 minus the regression slope of the regression line of diastolic plotted against systolic BP. Mean SMASI was 62 ± 0.20. SMASI correlated directly with age (r = 0.27; P = .03), BP load (r = 0.40; P = .002), home pulse pressure (r = 0.47; P < .001), and office pulse pressure (r = 0.44; P = .001). SMASI was higher in patients with multiple cardiovascular risk factors and correlated with pulse wave velocity (r = 0.45; P = .04) among 21 patients who underwent arterial tonometry. SMASI correlated with left ventricle (LV) mass/body surface area (BSA) (r = 0.30; P = .035) in 50 patients. SMASI increases with age, is associated with weaker BP control, hypertensive organ damage and correlates with pulse wave velocity. SMASI obtained by self–measured BP may serve as a useful surrogate measure of arterial stiffness.     

Ambulatory arterial stiffness index and renal abnormalities in primary hypertension

OBJECTIVE: Arterial stiffness is a predictor of cardiovascular mortality in the general population as well as in hypertension and end-stage renal disease. We investigated the relationship between a recently proposed ambulatory blood pressure monitoring-derived index of arterial stiffness and early signs of renal damage in patients with primary hypertension. DESIGN AND SETTING: A total of 168 untreated patients with sustained primary hypertension were studied. Ambulatory arterial stiffness index (AASI) was calculated based on 24-h ambulatory blood pressure readings. Albuminuria was measured as the albumin to creatinine ratio. Creatinine clearance was estimated using the Cockcroft-Gault formula, and the interlobar resistive index was evaluated by renal ultrasound and Doppler examination. RESULTS: AASI was positively related to urinary albumin excretion and resistive index, and was negatively related to estimated creatinine clearance and renal volume to the resistive index ratio. Patients with AASI above the median (i.e. > 0.51) showed a higher prevalence of microalbuminuria and a mild reduction in creatinine clearance. Moreover, patients with microalbuminuria or a mild reduction in creatinine clearance had significantly higher AASI values compared with those without, and the greater the renal involvement, the greater the AASI. After adjusting for several potentially confounding variables, we found that each standard deviation increase in AASI (i.e. 0.16) entails an almost twofold greater risk of renal involvement. CONCLUSION: Increased AASI is independently associated with early signs of renal damage in patients with sustained primary hypertension. These results strengthen the usefulness of AASI and ambulatory blood pressure monitoring in cardiovascular risk assessment.     

Cardio-ankle vascular index measures arterial wall stiffness independent of blood pressure

Although brachial-ankle pulse wave velocity (baPWV) is a non-invasive method of detecting arteriosclerosis, it is affected by changes in blood pressure (BP). Cardio-ankle vascular index (CAVI) is a new method for estimating arteriosclerosis, and it has been reported to be less influenced by BP. We investigated the influence of BP changes on CAVI and the correlation of CAVI to clinical factors and carotid arteriosclerosis. CAVI and baPWV in 35 non-diabetic and 33 diabetic subjects were measured in increased BP (after stair climbing) and rested BP (after 10min of rest). Intima-media thickness (IMT) of carotid arteries was measured by ultrasoundsonography. We achieved the following results: CAVI did not show a significant change with a change in BP in both non-diabetic and diabetic subjects. On the contrary, baPWV was significantly influenced by BP changes. Carotid artery IMT had a significant positive correlation with CAVI and baPWV. Multiple regression analysis revealed that significant risk factors of high baPWV were age and systolic BP. On the contrary, significant risk factors of high CAVI were age and hemoglobin A1c, while systolic BP was not relevant. Our findings suggest that CAVI is independent of BP and useful as an indicator of early arteriosclerosis in diabetic subjects.     

Long sleep duration and cardiovascular disease: Associations with arterial stiffness and blood pressure variability

Although short and long sleep duration are both risk factors of cardiovascular disease (CVD), the recent meta‐analyses have been shown that long sleep duration was closely associated with CVD mortality. While the specific mechanism underlying the association between long sleep duration and CVD remains unclear, long sleep duration was shown to be associated with arterial stiffness and blood pressure variability (BPV) in many Asian populations. This review article will focus on the pathophysiology of long sleep duration, arterial stiffness, BPV and their effects on CVD. To set the stage for this review, we first summarize the current insights for the relationship between long sleep duration and CVD in relation to arterial stiffness and BPV.     

老年高血压病患者血压昼夜节律与动态的动脉硬化指数的关系

目的 探讨老年高血压病患者血压昼夜节律与动态动脉硬化指数的关系。方法 根据动态血压检测结果将112例老年高血压病患者分为杓形组(n=37)、非杓形组（n=45）和反杓形组（n=30）,并测定及计算动态动脉硬化指数（AASI）。结果 3组年龄,体质量指数,总胆固醇、三酰甘油、低密度脂蛋白胆固醇、高密度脂蛋白胆固醇、空腹血糖、病程和全天及白天平均收缩压、舒张压和脉压比较均无显著性差异。3组夜间平均收缩压、夜间平均舒张压、AASI比较有显著性差异（P<0.01）。结论 动态血压昼夜节律的改变与动态动脉硬化指数相关。     

Ambulatory pulmonary arterial pressure in primary pulmonary hypertension: variability, relation to systemic arterial pressure, and plasma catecholamines

The variability of pulmonary arterial pressure, the relation of pulmonary pressure to systemic pressure, pulmonary pressure responses to stimuli (exercise, hypoxia, smoking, free ambulation), and plasma catecholamine responses were assessed in five patients with primary pulmonary hypertension. Ambulatory monitoring techniques provided data for the computerised analysis of continuous, beat-to-beat, direct recordings of both pulmonary and systemic arterial pressures for 8 to 10 hours. The absolute variability of pulmonary arterial pressure and the magnitude of absolute changes in this variable in response to stimuli were increased in primary pulmonary hypertension. The variability of systemic pressure was similar to that in healthy volunteers. Basal and stimulated plasma catecholamine values were normal, suggesting preservation of normal sympathetic nervous system activity in primary pulmonary hypertension.