A modified ambulatory arterial stiffness index is independently associated with all-cause mortality

Ambulatory arterial stiffness index, mortality, and adverse cardiovascular outcomes; Systematic review and meta-analysis

The ambulatory arterial stiffness index (AASI) is a novel measure of both blood pressure (BP) variability and arterial stiffness. This systematic review and meta-analysis was designed to evaluate the strength of the association between AASI and mortality and major adverse cardiovascular events (MACE). PubMed, Scopus, CINAHL, Google Scholar. and the Cochrane library were searched for relevant studies to July 31, 2023. Two investigators independently extracted data. The Newcastle-Ottawa Scale (NOS) was used to assess the quality of all included articles. The relationship between baseline AASI and outcomes were examined using relative risk (RR) ratios with 95% confidence intervals (CI) with RevMan web. Thirteen studies were included and representing 28 855 adult patients who were followed up from 2.2 to 15.2 years. A 1-standard deviation (1-SD) increase in AASI was associated with a significant increase in all-cause death (RR 1.12; 95% CI: 0.95-1.32), stroke (RR 1.25; 95% CI: 1.09-1.44), and MACE (RR 1.07; 95% CI: 1.01-1.13; [I2  = 32%]). Higher dichotomized AASI (above vs. below researcher defined cut-offs) was associated with a significant increase in all-cause mortality (RR 1.19; 95% CI: 1.06-1.32), cardiovascular death (RR 1.29; 95% CI: 1.14-1.46), stroke (RR 1.57; 95% CI: 1.33-1.85), and MACE (RR1.29; 95% CI: 1.16-1.44). There was a significant risk of bias in more than 50% of studies with no evidence of significant publication bias. Higher AASI is associated with an increased risk of all-cause and cardiovascular death, stroke, and MACE. Further high-quality studies are warranted to determine reproducible AASI cut-offs to enhance its clinical risk precision.

Do estimated 24-h pulse pressure components affect outcome? The Ohasama study

OBJECTIVE

Twenty-four-hour ambulatory pulse pressure (PP) is a powerful predictor of outcome. We attempted to apply the recently described PP components, an elastic (elPP), and systolic stiffening (stPP) components from 24-h ambulatory blood pressure (BP) monitoring (AMBP), and examine their influence on outcome in the Ohasama study population.

DESIGN AND METHODS

Included were participants of the Ohasama study without history of cardiovascular disease (CVD), who were followed-up for total and CVD mortality, and for stroke morbidity. The PP components were derived from 24-h SBP and DBP using a model based on the nonlinear pressure--volume relationship in arteries expressing pressure stiffness relationship. Outcome predictive power was estimated by Cox regression models; hazard ratio with 95% confidence interval (CI), applied to elPP, and stPP, adjusted for age, sex, BMI, smoking, alcohol drinking, diabetes mellitus, total cholesterol, antihypertensive treatment, and mean arterial pressure (MAP), whenever appropriate.

RESULTS

Of 1745 participants (age 61.4 ± 11.6, 65% women), 580 died, 212 of CVD, and 290 experienced a stroke during 17 follow-up years. PP was strongly correlated with elPP (r = 0.89) and less so with stPP (r = 0.58), and the correlation between the two components was weak (r = 0.15). After the adjustment, hazard ratio of PP per 1 SD increment for total mortality, CVD mortality, and stroke morbidity were 1.095 (95% CI 0.973-1.232), 1.207 (1.000-1.456), and 0.983 (0.829-1.166), respectively. Corresponding hazard ratios and 95% CIs were nonsignificant for elPP, and stPP. However, among participants with median pulse rate 68.5 bpm or less (median, n = 872), total (327 deaths) and CVD (131 deaths) mortality were predicted by elPP (per 1 SD increment), hazard ratio 1.231 (95% CI, 1.082-1.401), and 1.294 (95% CI, 1.069-1.566), respectively. In the subgroup of treated participants with hypertension and pulse rate 68.5 or less bpm (n = 309), total (177 deaths) and CVD (77 deaths) mortality were predicted by elPP, hazard ratio of 1.357 (95% CI, 1.131-1.628), and 1.417 (95% CI, 1.092-1.839), respectively. Stroke morbidity was not predicted by either PP or the PP components.

CONCLUSION

In a rural Japanese population, elPP but not stPP was predictive of total and CVD mortality even when adjusted for MAP and conventional risk factors in the subpopulation with slower pulse rate. This was mostly among the treated hypertensive patients.

Association of Blood Pressure Variability Ratio With Glomerular Filtration Rate Independent of Blood Pressure and Pulse Wave Velocity

BACKGROUND

Blood pressure variability ratio (BPVR)(derived from within-subject SD of 24-hour ambulatory blood pressure [BP]) predicts all-cause mortality independent of BP and has a similar prognostic ability to ambulatory arterial stiffness (AASI). Whether BPVR, and AASI, offer prognostic information beyond measurements of arterial stiffness at a given pressure, as indexed by pulse wave velocity (PWV), is not known.

METHODS

We assessed whether BPVR and AASI were associated with indices of subclinical organ damage (TOD) [estimated glomerular filtration rate (eGFR), left ventricular mass index, early-to-late transmitral velocity (E/A), carotid intima-media thickness (IMT)] independent of BP, and whether BPVR-TOD and AASI-TOD relations were independent of PWV (applanation tonometry) in 772 randomly selected participants from an urban, developing community. AASI was derived from 24-hour diastolic BP vs. systolic BP standard linear regression.

RESULTS

On bivariate analyses, BPVR, AASI, and PWV were correlated with all indices of TOD (P < 0.0005). However, after adjustments for potential confounders including age and 24-hour mean BP, BPVR, and PWV (P < 0.005 to P < 0.0001), but not AASI (P > 0.25), were independently associated with eGFR, but not other indices of TOD. Importantly, the BPVR-eGFR relation was independent of BP variability (P < 0.005) and PWV (P < 0.001).

CONCLUSIONS

BPVR was negatively associated with eGFR independent of mean BP, BP variability, and PWV. Therefore, in the prediction of cardiovascular risk, measurements of arterial stiffening (BPVR) may provide information beyond the impact of arterial stiffness.

Elevated sympathetic activity, endothelial dysfunction, and late hypertension after repair of coarctation of the aorta

BACKGROUND

There is a high prevalence of late hypertension after coarctation repair. The relative contribution of elevated sympathetic tone and endothelial dysfunction to its development is unknown. This study aims to investigate the neural profile of coarctation patients including muscle sympathetic nerve activity testing to directly measure sympathetic nervous activity.

METHODS

Twenty-three patients aged ≥18years with a coarctation repair underwent measurements of clinic and 24-h blood pressures, muscle sympathetic nerve activity, sympathetic and cardiac baroreflex functions, digital endothelial function, and ambulatory arterial stiffness index. Median age at repair was 1.2months (interquartile range: 0-9months). Patients were compared to 17 healthy matched controls.

RESULTS

After 26±5years, 6% (1/18) and 44% (8/18) suffered clinic hypertension and prehypertension, respectively. On 24-h blood pressure monitoring, 15% (3/20) and 20% (4/20) had hypertension and prehypertension, respectively. Coarctation patients had elevated muscle sympathetic nerve activity compared with controls (49.6±24.9 vs. 29.9±14.0 bursts/100 heartbeats, p=0.02), dampened sympathetic baroreflex function (-2.2±2.1 vs. -7.0±5.6 bursts/100heartbeats·mm·Hg^-1, p=0.007), normal cardiac baroreflex function (41.9±30.4 vs. 35.7±21.1ms·mm·Hg^-1, p=0.6), endothelial dysfunction (pulse amplitude tonometry ratio: 0.39±0.32 vs. 0.81±0.50, p=0.004), and increased ambulatory arterial stiffness index (0.46±0.15 vs. 0.29±0.17, p=0.008).

CONCLUSION

After coarctation repair patients have increased muscle sympathetic nerve activity, dampened sympathetic baroreflex response, endothelial dysfunction, and increased ambulatory arterial stiffness index, all of which may contribute to the development of late hypertension.

Arterial Stiffness: Going a Step Beyond

Interest in arterial stiffness has been fueled by the scientific and clinical implications of its "vicious cycle" relationship with aging and systolic blood pressure. In physical terms, stiffness is the slope of the relationship between an artery's distending pressure and its cross-sectional area or volume. Pulse wave velocity (PWV, in m/s), the most common arterial stiffness indicator, is usually measured by the foot-to-foot time and distance method and is proportional to [stiffness × area (or volume)]1/2 at a given pressure. Its intrinsic pressure dependency and other flaws in current PWV methods limit its utility. In contrast, the arterial stiffness-arterial pressure relationship is near-linear, with a slope β, the exponent of the curvilinear arterial pressure-arterial volume relationship. The concept of arterial stiffening is related to β and describes a more functionally relevant aspect of arterial behavior: the change in stiffness for a given change in pressure. Arterial stiffening can be estimated from the variability of within-individual BP measurements (24-h ambulatory, home BP, or BP measured at different arm heights) and can be expressed as the pulse stiffening ratio (PSR) = [systolic stiffness]/[diastolic stiffness] or the ambulatory arterial stiffness index (AASI or its symmetric form, sAASI). High arterial stiffness (PWV) and stiffening (β, stiffness index, cardio-ankle vascular index, AASI, and PSR) are associated with increased cardiovascular disease risk, but it remains unclear whether these indicators are useful in improving medical care quality; the standard of care remains stringent BP control.

Symmetric ambulatory arterial stiffness index in the young

The ambulatory arterial stiffness index (AASI) and the symmetric ambulatory arterial stiffness index (s-AASI) have been shown to correlate to arterial stiffness in adults. This study assesses these indices with anthropometric and blood pressure (BP) measures in children. A total of 102 children at a pediatric hypertension clinic who had ambulatory blood pressure monitoring (ABPM) done from 2009 to 2013 were included (75% males, 7-22yo, 47% hypertensive, 24% prehypertensive, and 34% white-coat hypertensives). AASI is 1 minus the regression slope of diastolic BP values on systolic BP values from a 24-hour ambulatory blood pressure monitoring. s-AASI is the symmetric regression of AASI. Obese patients had a significantly higher AASI. s-AASI correlated with systolic BP variability. In multivariable regression, BP variability independently correlated with AASI and s-AASI. s-AASI is related to systolic dipping.AASI and s-AASI are highly dependent on BP variability in children. Further studies are necessary to assess their utility.

Association of ambulatory arterial stiffness index with sEPCR in newly diagnosed hypertensive patients

AIM

Increased arterial stiffness is strongly associated with cardiovascular diseases, while thrombotic events are more common than hemorrhagic events in hypertensive patients. Markers of a hypercoagulable state may also predict future cardiovascular events in hypertensive patients. Here, we speculated that increased arterial stiffness might lead to the development of a hypercoagulable state that can play a role in the thrombotic complications of hypertension. Soluble endothelial protein C receptor (sEPCR) is one such marker of hypercoagulation. The ambulatory arterial stiffness index (AASI) could be accepted as a non-invasive measure of arterial stiffness. The aim of this study was to investigate association of AASI with levels of sEPCR in newly diagnosed hypertensive patients.

MATERIALS AND METHODS

The study included 263 newly diagnosed essential hypertensive patients and 55 healthy normotensive controls. All subjects underwent 24 h ambulatory blood pressure monitoring (ABPM); the AASI was derived from ABPM tracings. Plasma sEPCR was measured by ELISA.

RESULTS

Hypertensive patients (n = 263) had higher AASI, C-reactive protein (CRP) and sEPCR versus the normotensive healthy group (n = 55). Univariate analysis showed that AASI was positively associated with age (r = 0.212, p <  0.001) body mass index (r = 0.412, p < 0.001), pulse pressure (r = 0.350, p < 0.001), plasma sEPCR (r = 0.894, p < 0.001), 24-h heart rate (r = 0.176, p = 0.001) and inversely related to high-density lipoprotein (HDL) (r = -0.293, p < 0.001). Multivariate analyses revealed that sEPCR and HDL are independently correlated to AASI.

CONCLUSION

We suggest that increased AASI is associated with elevated sEPCR. It might be responsible for subsequent thrombotic events in newly diagnosed hypertensive patients.

Treatment-induced changes in ambulatory arterial stiffness index: one-year prospective study and meta-analysis of evidence

The ambulatory arterial stiffness index (AASI) has been introduced as an index of arterial function, predicting cardiovascular events. However, treatment-induced changes in AASI are rather equivocal. This study aims to: (i) present the results of treatment-induced changes in AASI in untreated subjects with elevated blood pressure (BP), subjected to antihypertensive treatment for 1 year and (ii) perform a meta-analysis of studies reporting on treatment-induced change in AASI. A total of 104 subjects (mean age 51.4±10.3 years, 62% males, mean follow-up: 13.6±2.4 months) were analyzed. Despite significant reductions in 24-h ambulatory systolic/diastolic BP, pulse pressure and pulse wave velocity (mean change: -15.9±12/-10.4±7.6 mm Hg, -5.4±6.8 mm Hg, -0.7±1.9 m s(-1), respectively, all P<0.05), there was no significant change (Follow up-Baseline) in AASI values (mean change: 0.01±0.17, P=not significant). The treatment-induced change in AASI was correlated with baseline AASI (r=-0.61), baseline 24-h pulse pressure (-0.26), treatment-induced change in 24-h pulse pressure (0.26) and in systolic/diastolic nocturnal dipping (-0.25/-0.40, respectively). Meta-analysis of eight trials (n=990) revealed a marginal decrease in AASI with antihypertensive treatment (pooled change: -0.018 (95% confidence interval (CI): -0.033,-0.003)). When the analysis was restricted to data with renin-angiotensin system blockers (n=755, 76% of total), the results did not significantly change (pooled change -0.028 (95% CI -0.048, -0.007)). In conclusion, although AASI is an independent predictor of cardiovascular events, its response to antihypertensive treatment is only marginal and clinically uncertain, which may render its use as a therapeutic target in clinical practice questionable.

A systematic review of vascular and endothelial function: effects of fruit, vegetable and potassium intake

AIM

To review the relationships between: 1) Potassium and endothelial function; 2) Fruits and vegetables and endothelial function; 3) Potassium and other measures of vascular function; 4) Fruits and vegetables and other measures of vascular function.

DATA SYNTHESIS

An electronic search for intervention trials investigating the effect of potassium, fruits and vegetables on vascular function was performed in MEDLINE, EMBASE and the Cochrane Library. Potassium appears to improve endothelial function with a dose of >40 mmol/d, however the mechanisms for this effect remain unclear. Potassium may improve measures of vascular function however this effect may be dependent on the effect of potassium on blood pressure. The effect of fruit and vegetables on endothelial function independent of confounding variables is less clear. Increased fruit and vegetable intake may improve vascular function only in high risk populations.

CONCLUSION

Increasing dietary potassium appears to improve vascular function but the effect of increasing fruit and vegetable intake per se on vascular function is less clear.

The relationship between renal resistive index, arterial stiffness, and atherosclerotic burden: the link between macrocirculation and microcirculation

The renal resistive index (RRI) measured by Doppler sonography is a marker of microvascular status that can be generalized to the whole of the arterial tree. Its association with large-vessel dysfunction, such as arterial stiffness or the atherosclerotic burden, can help to establish physiopathological associations between macrocirculation and microcirculation. The authors conducted a cross-sectional study of hypertensive patients (n=202) and a healthy control group (n=16). Stiffness parameters, atherosclerotic burden, and determination of the RRI in both kidneys were performed. The average RRI was 0.69±0.08 and was significantly greater in patients with diabetes and chronic kidney disease. Renal resistive index positively correlated with age, creatinine, and albuminuria. Positive correlations were found with arterial stiffness parameters (pulse wave velocity, ambulatory arterial stiffness index, and 24-hour pulse pressure), as well as atherosclerotic burden and endothelial dysfunction measured as asymmetric dimethylarginine in serum. In the multivariate analysis, independent factors for increased RRI were age, renal function, 24-hour diastolic blood pressure, and arterial stiffness. The authors concluded that there is an independent association between renal hemodynamics and arterial stiffness. This, together with the atherosclerotic burden and endothelial dysfunction, suggests that there is a physiopathologic relationship between macrovascular and microvascular impairment.

Symmetric ambulatory arterial stiffness index and 24-h pulse pressure in HIV infection: results of a nationwide cross-sectional study

OBJECTIVE

HIV infection has been associated with increased cardiovascular risk. Twenty-four-hour ambulatory blood pressure (BP) is a more accurate and prognostically relevant measure of an individual's BP load than office BP, and the ambulatory BP-derived ambulatory arterial stiffness index (AASI) and symmetric AASI (s-AASI) are established cardiovascular risk factors.

METHODS

In the setting of the HIV and HYpertension (HIV-HY) study, an Italian nationwide survey on high BP in HIV infection, 100 HIV-infected patients with high-normal BP or untreated hypertension (72% men, age 48 ± 10 years, BP 142/91 ± 12/7 mmHg) and 325 HIV-negative individuals with comparable age, sex distribution, and office BP (68% men, age 48 ± 10 years, BP 141/90 ± 11/8 mmHg) underwent 24-h ambulatory BP monitoring.

RESULTS

Despite having similar office BP, HIV-infected individuals had higher 24-h SBP (130.6 ± 14 vs. 126.4 ± 10 mmHg) and pulse pressure (49.1 ± 9 vs. 45.9 ± 7 mmHg, both P < 0.001), and a lower day-night reduction of mean arterial pressure (14.3 ± 9 vs. 16.3 ± 7%, P = 0.025). Both s-AASI and AASI were significantly higher in HIV patients (s-AASI, 0.22 ± 0.18 vs. 0.11 ± 0.15; AASI, 0.46 ± 0.22 vs. 0.29 ± 0.17; both P <0.001). In a multivariate regression, s-AASI was independently predicted by HIV infection (β = 0.252, P <0.001), age, female sex, and 24-h SBP. In HIV patients, s-AASI had an inverse relation with CD4 cell count (Spearman's ρ -0.24, P = 0.027).

CONCLUSION

Individuals with HIV infection and borderline or definite hypertension have higher symmetric AASI and 24-h systolic and pulse pressures than HIV-uninfected controls matched by office BP. High ambulatory BP may play a role in the HIV-related increase in cardiovascular risk.

Salt loading and potassium supplementation: effects on ambulatory arterial stiffness index and endothelin-1 levels in normotensive and mild hypertensive patients

The authors investigated effects of excessive salt intake and potassium supplementation on ambulatory arterial stiffness index (AASI) and endothelin-1 (ET-1) in salt-sensitive and non-salt-sensitive individuals. AASI and symmetric AASI (s-AASI) were used as indicators of arterial stiffness. Plasma ET-1 levels were used as an index of endothelial function. Chronic salt-loading and potassium supplementation were studied in 155 normotensive to mild hypertensive patients from rural northern China. After 3 days of baseline investigation, participants were maintained sequentially for 7 days each on diets of low salt (51.3 mmol/d), high salt (307.7 mmol/d), and high salt+potassium (60 mmol/d). Ambulatory 24-hour blood pressure (BP) and plasma ET-1 were measured at baseline and on the last 2 days of each intervention. High-salt intervention significantly increased BP, AASI, s-AASI (all P<.001); potassium supplementation reversed increased plasma ET-1 levels. High-salt-induced changes in BP, s-AASI, and plasma ET-1 were greater in salt-sensitive individuals. Potassium supplementation decreased systolic BP and ET-1 to a significantly greater extent in salt-sensitive vs non-salt-sensitive individuals (P<.001). Significant correlations were identified between s-AASI and ET-1 change ratios in response to both high-salt intervention and potassium supplementation (P<.001). Reducing dietary salt and increasing daily potassium improves arterial compliance and ameliorates endothelial dysfunction.

Ambulatory arterial stiffness indices and non-alcoholic fatty liver disease in essential hypertension

BACKGROUND AND AIM

Non-alcoholic fatty liver disease (NAFLD) has been found to be strongly related to an increased arterial stiffness in patients with essential hypertension, suggesting a pathophysiologic link between major cardiovascular and metabolic abnormalities associated with liver steatosis and the functional and structural alterations of the arterial wall. The aim of our study was to investigate, in a group of essential hypertensive patients without additional cardiovascular risk factors, the relationship between NAFLD and arterial stiffness.

METHODS AND RESULTS

Sixty-eight consecutive patients with essential hypertension underwent 24-h ambulatory blood pressure monitoring (ABPM) and were separated according to the presence (n = 40) or absence (n = 28) of NAFLD at liver ultrasonography. The Ambulatory Arterial Stiffness Index (AASI) and Symmetric AASI (Sym-AASI) were derived from ABPM tracings. Patients with diabetes, obesity, hyperlipidaemia or other risk factors for cardiovascular or liver disease were excluded. Hypertensive patients were compared with a normotensive control group.The two hypertensive groups had comparable age, sex distribution and clinic/ABPM blood pressure levels. In hypertensive patients with NAFLD, body mass index, fasting glucose, insulin, homeostasis model of assessment of insulin resistance index and triglyceride levels were higher, whereas plasma adiponectin was lower than in patients without NAFLD. In hypertensive patients, AASI and Sym-AASI were higher (P < 0.001) than in normotensive subjects, but both indices of vascular stiffness were comparable in patients with and without NAFLD.

CONCLUSIONS

In essential hypertensive patients without additional cardiovascular risk factors, NAFLD is associated with insulin resistance but not with increased arterial stiffness.

Prognostic factors in resistant hypertension: implications for cardiovascular risk stratification and therapeutic management

Resistant hypertension (RH) is defined as uncontrolled office blood pressure (BP) in spite of the use of at least three antihypertensive medications. Although its condition has a high prevalence, it is still understudied, and its prognosis is not well established. Some prospective studies evaluated the prognostic value of ambulatory BP monitoring, ECG and renal parameters. They pointed out that ambulatory BPs are important predictors of cardiovascular morbidity and mortality, whereas office BP has no prognostic value. The diagnosis of true RH and the nondipping pattern are also valuable predictors of cardiovascular outcomes. Moreover, several ECG (prolonged ventricular repolarization, serial changes in the strain pattern and left ventricular hypertrophy) and renal parameters (albuminuria and reduced glomerular filtration rate) are also powerful cardiovascular risk markers in RH. These markers and others yet unexplored, such as arterial stiffness and serum biomarkers, may improve cardiovascular risk stratification in these very high-risk patients.

Association of changes in ambulatory arterial stiffness index and pulse wave velocity during antihypertensive treatment: the J-CORE study

BACKGROUND

We aimed to investigate the association of the change in the ambulatory arterial stiffness index (AASI) with that in carotid-femoral pulse wave velocity (cfPWV) during treatment with antihypertensive medication.

METHODS

We enrolled 207 hypertensive patients treated with olmesartan monotherapy for 12 weeks. Patients were randomly assigned to treatment with hydrochlorothiazide (HCTZ; n = 104) or azelnidipine (n = 103) for 24 weeks. The cfPWV and 24-h ambulatory blood pressure monitoring (ABPM) results were assessed at baseline and 24 weeks later. The AASI was defined as 1 minus the regression slope of diastolic blood pressure (DBP) on systolic BP (SBP), and was calculated by standard and symmetric regression.

RESULTS

The changes in the AASI and symmetrical AASI were similar between the two groups, while cfPWV in the azelnidipine group decreased more than in the HCTZ group (P < 0.001). The change in AASI was not significantly correlated with change in cfPWV (r = 0.08, P = 0.26), whereas the change in symmetrical AASI was significantly but weakly correlated with change in cfPWV (r = 0.22, P < 0.001). The multivariable linear regression analysis revealed that the association of the change in symmetrical AASI with change in cfPWV remained significant even after adjustments for covariates derived from ABPM (regression coefficient (95% confidence interval): 1.33 (0.35-2.30), P = 0.01).

CONCLUSIONS

The present study demonstrated that neither AASI nor symmetrical AASI may be an unequivocal marker of arterial stiffness during antihypertensive treatment.

Ambulatory arterial stiffness index in chronic kidney disease stage 2-5. Reproducibility and relationship with pulse wave parameters and kidney function

BACKGROUND

Arterial stiffness contributes to the increased cardiovascular risk in patients with chronic kidney disease (CKD). Reproducible and easily obtainable indices of arterial stiffness are needed in order to monitor therapeutic strategies. The ambulatory arterial stiffness index (AASI) has been proposed as such a marker. The present study investigated the day-to-day reproducibility of AASI in CKD stage 2-5 and its relationship with other markers of arterial stiffness as well as with kidney function.

METHODS

Eighty-three patients (29% female, median age 62 years) were studied by 24 h ambulatory blood pressure monitoring (ABPM), aortic pulse wave velocity (aPWV), augmentation index (AIx) and estimated glomerular filtration rate (eGFR) at a median interval of 7 days. Individual AASIs were calculated from 24 h ABPMs as 1 minus the regression slope of diastolic blood pressure over systolic blood pressure.

RESULTS

Mean AASI, aPWV, AIx and 24 h pulse pressure (PP) were similar on repeated measurements. The intraclass correlation coefficients were between 72% and 78% for AASI calculated by three different methods, 87% for aPWV, 88% for AIx, and 96% for 24 h PP. The correlation coefficients between AASI and aPWV were from 0.48 to 0.53; with AIx it was between 0.19 and 0.34. After adjustment for covariates none of the arterial stiffness indices were significantly correlated to eGFR.

CONCLUSIONS

In patients with CKD stage 2-5 AASI had a moderate, but acceptable reproducibility. The correlation between AASI and aPWV was good whilst the correlation between AASI and AIx was considerably lower. There was no significant correlation between AASI and eGFR.

Ambulatory arterial stiffness indexes in acromegaly

OBJECTIVE

Acromegaly is associated with increased cardiovascular morbidity and mortality and with specific heart and vascular abnormalities. The aim of our study was to investigate arterial stiffness using the ambulatory arterial stiffness index (AASI) and symmetric AASI (Sym-AASI), two indexes derived from 24-h ambulatory blood pressure monitoring (ABPM), in a group of normotensive and hypertensive patients with active acromegaly, compared with normotensive controls (NOR-CTR) or hypertensive controls (HYP-CTR).

SUBJECTS AND METHODS

Ninety-six consecutive patients with active acromegaly (46 males, mean age 49±14 years) underwent 24-h ABPM and evaluation of cardiovascular risk factors. Based on ABPM measurement, acromegalic patients were divided into 64 normotensive (normotensive acromegalic patients (NOR-ACRO)) and 32 hypertensive (hypertensive acromegalic patients (HYP-ACRO)) patients, and were compared with 35 normotensive (NOR-CTR) and 34 hypertensive (HYP-CTR) age-, sex,- and ABPM-matched control subjects.

RESULTS

The AASI and Sym-AASI indexes were significantly higher in acromegalic patients than in controls, either in the normotensive (NOR-ACRO vs NOR-CTR, P<0.0001 for AASI and P=0.005 for Sym-AASI) or in the hypertensive (HYP-ACRO vs HYP-CTR, P=0.01 for AASI and P=0.01 for Sym-AASI) group. Multiple logistic regression analysis showed a significant association of the highest AASI tertile with serum IGF1 (P=0.034) in the whole acromegalic group.

CONCLUSION

AASIs are increased in acromegaly, independent of blood pressure (BP) elevation, and may have an important role in predicting cardiovascular risk in this disease.

Adherence to antihypertensive therapy affects Ambulatory Arterial Stiffness Index

BACKGROUND

A major contributor to poor blood pressure (BP) control is nonadherence to therapy, which remains poorly recognized by physicians. The prevention of hypertension-induced changes in arterial wall, namely increased arterial stiffness and peripheral vascular resistance, is a reasoned adequate end-point of hypertension treatment. Indirect measurement of these arterial factors can be derived from the analysis of 24-hour Ambulatory BP Monitoring (24 h-ABPM). This pilot study evaluated the association between antihypertensive therapy adherence and 24 h-ABPM-derived parameters in hypertensive patients.

METHODS

We studied 42 hypertensive patients (70±10 years) in chronic antihypertensive therapy. Patients were divided according to the Morisky Medication Adherence Scale (MMAS) in Low-Adher (MMAS <6) and High-Adher (MMAS 6-8) groups. The Ambulatory Arterial Stiffness Index (AASI) and its symmetric calculation (Sym_AASI) were derived from 24 h-ABPM. A bivariate logistic regression analysis was performed to evaluate the predictive value of MMAS for increased AASIs (i.e. above the median).

RESULTS

Low-Adher group (n=17) showed higher AASIs compared to High-Adher group (n=25). The two groups were similar in terms of BP burden at the 24 h-ABPM. AASIs were inversely related to MMAS. MMAS resulted a predictor for both increased AASI (O.R. 0.49, 95% CI 0.31-0.76, P<0.01) and increased Sym_AASI (O.R. 0.67, 95% CI 0.47-0.95, P=0.026). After adjustment for PP, age and nocturnal diastolic BP reduction, MMAS persisted as an inverse predictor only of increased AASI. MMAS was also related to the diastolic vs systolic BP correlation coefficient r.

CONCLUSIONS

Low adherence to antihypertensive therapy seems to be associated with increased standard AASI. In this setting, AASI could represent an additional information derived from the 24 h-ABPM in hypertensive patient evaluation.

Association of hemoglobin with ambulatory arterial stiffness index in untreated essential hypertensive patients without anemia

OBJECTIVE

Increased hemoglobin (Hb) levels are known to be associated with increased cardiovascular events and mortality in hypertensive patients, but the underlying mechanism remains unclear. However, an increased Ambulatory Arterial Stiffness Index (AASI), the surrogate maker of arterial stiffness, has been proven to be an independent predictor of cardiovascular disease. This pilot study evaluated the association between Hb and AASI in untreated essential hypertensive patients without anemia.

METHODS

A total of 566 untreated essential hypertensive patients without anemia were divided into Normal-Hb and High-Hb groups according to their Hb levels. The AASI and its symmetric calculation (Sym_AASI) were derived from 24h-Ambulatory Blood Pressure Monitoring (24h-ABPM). A multivariable linear regression analysis was performed to determine the relationship between Hb and AASI, Sym_AASI.

RESULTS

High-Hb group (n=127) showed higher AASI and Sym_AASI (0.51±0.11 vs 0.43±0.12, p<0.001; 0.33±0.10 vs 0.27±0.08, p<0.001) compared to Normal-Hb group (n=439). Univariate correlation analysis showed that Hb levels were positively related to AASI and Sym_AASI values (r=0.459, p<0.001; r=0.353, p<0.001). After adjustment for age, sex, BMI, current smoker, eGFR, uric acid, total cholesterol, high-density lipoprotein, 24h-SBP, 24h-PP and dipper status, Hb persisted as a independent determinant of AASI and Sym_AASI (β=0.402, p<0.001 and β=0.298, p<0.001, respectively).

CONCLUSION

High hemoglobin seems be to associated with increased AASI in untreated essential hypertensive patients without anemia.

Prognostic impact of the ambulatory arterial stiffness index in resistant hypertension

OBJECTIVE

The ambulatory arterial stiffness index (AASI), derived from ambulatory blood pressure (BP) monitoring recordings, is an indirect marker of arterial stiffness and a potential predictor of cardiovascular risk. Resistant hypertension is defined as uncontrolled office BP despite the use of at least three antihypertensive drugs. The aim of this prospective study was to investigate the AASI prognostic value in patients with resistant hypertension.

METHODS

At baseline, 547 patients underwent clinical-laboratory, and 24-h ambulatory BP monitoring examinations. AASI was defined as 1 minus the regression slope of DBP on SBP, and was calculated by standard and symmetric regression. Primary endpoints were a composite of fatal and nonfatal cardiovascular events and all-cause and cardiovascular mortalities. Multiple Cox regression was used to assess associations between AASI and subsequent endpoints.

RESULTS

After median follow-up of 4.8 years, 101 patients (18.4%) reached the primary endpoint, and 65 all-cause deaths (11.9%) occurred (45 from cardiovascular causes). 24-h AASI was the best independent predictor of composite endpoint (hazard ratio 1.46, 95% confidence interval 1.12-1.92, for increments of 1-SD = 0.14), whereas cardiovascular mortality was best predicted by night-time AASI (hazard ratio 1.73, 95% confidence interval 1.13-2.65), after adjustments for cardiovascular risk factors, including mean ambulatory BPs and nocturnal BP reduction. Symmetric AASI was not superior to standard AASI. In sensitivity analysis, 24-h AASI was a better predictor of cardiovascular outcomes in women, in younger individuals, and in nondiabetic individuals.

CONCLUSION

AASI is a predictor of cardiovascular morbidity and mortality in resistant hypertension, over and beyond traditional risk factors and other ambulatory BP monitoring parameters.

Symmetrical ambulatory arterial stiffness index: relationship with microalbuminuria and renal function

OBJECTIVE

The aim of this study was to investigate the arterial stiffness parameters derived from the proposed linear relationship between SBP and DBP obtained by ABPM, regarding its relationships with two markers of renal disease, microalbuminuria and renal function.

DESIGN AND METHODS

One hundred and sixty six patients were studied: 73 males and 93 females mean age 55.2+/-15.5 years. 36.2% were receiving antihypertensive drug treatment. Microalbuminuria was measured in 24-h urine collection as well as albumin to creatinine ratio (ACR) in first morning urine. The ambulatory BP was measured non-invasively for 24 h by the Spacelab devices.

RESULTS

Correlation test showed a significant relationship of Sym-AASI with age (p<0.001), serum creatinine (p=0.038), creatinine clearance (-0.423, p<0.001) and GFR (-0.263, p<0.001). On the other hand AASI was also correlated with age (p<0.001) and creatinine clearance (p=0.012), but not with the other parameters studied. 24-h albumin excretion rate was not correlated with Sym-AASI or AASI. Contrariwise, the albumin to creatinine ratio was correlated with Sym-AASI (p=0.013). As expected, AASI and Sym-AASI increase as severity of renal diseases grows. The patients in the highest quartile of Sym-AASI distribution showed an older age (p<0.001) and worse parameters of renal function (GFR, p<0.001; and creatinine clearance, p<0.008).

CONCLUSIONS

Sym-AASI, an improved method for detecting arterial stiffness, seems to get an independent relationship with these parameters of renal disease which could not be detected with AASI.

Ambulatory arterial stiffness index: reproducibility of different definitions

BACKGROUND

Ambulatory arterial stiffness index (AASI) has been proposed as a marker of arterial stiffness, which predicts cardiovascular mortality. This study compared the reproducibility of 24-h, daytime, night time, and symmetrical AASI.

METHODS

A total of 126 untreated hypertensives (mean age 48.2 +/- 10.7 (s.d.) years, 70 men) underwent 24-h ambulatory blood pressure (ABP) monitoring twice 2-4 weeks apart. The reproducibility of AASI was assessed using the following criteria: (i) repeatability coefficient (RC = 2 x s.d. of differences); (ii) RC expressed as a percentage of close to maximal variation (pMV = RC/(4 x s.d. of the mean of paired recordings)); (iii) coefficient of variation (CV); (iv) concordance correlation coefficient (CCC); (v) agreement (kappa) between the two AASI measurements to detect subjects at the top quartile of the respective AASI distributions.

RESULTS

There was no difference in average AASI values between the two assessments. For 24-h, daytime, night time, and symmetrical AASI, respectively, (i) RC values were 0.24, 0.38, 0.42, and 0.30; (ii) pMV 49.6, 68.8, 73.9, and 56; (iii) CV 40.3, 39.3, 62.9, and 116.3; (iv) CCC 0.60, 0.35, 0.28, and 0.52; (v) agreement 82.5% (kappa 0.54), 72.2% (0.28), 73% (0.22), and 81.7% (0.50). Differences in 24-h mean arterial ambulatory pressure (MAP) and in nocturnal MAP decline between the two assessments were significant determinants of the differences in 24-h and symmetrical AASI values.

CONCLUSIONS

Although no differences were found in average AASI values of the two ambulatory recordings, significant differences were observed in their reproducibility, with 24-h AASI being the most reproducible measure in terms of all the examined criteria.American Journal of Hypertension 2010; doi:10.1038/ajh.2009.217.

Increased ambulatory arterial stiffness index and pulse pressure in microalbuminuric patients with type 1 diabetes

BACKGROUND

Ambulatory arterial stiffness index (AASI) has been proposed as an indirect measure of arterial stiffness. The aims of this study were (i) to analyze AASI and pulse pressure (PP) in micro- and normoalbuminuric type 1 diabetes mellitus (T1DM) patients and healthy controls and (ii) to explore the relation between nocturnal blood pressure (BP) reduction, BP variability, and AASI.

METHODS

Ambulatory BP monitoring was performed in 34 micro- and 34 normoalbuminuric T1DM patients matched for gender, age, and diabetes duration and in 34 nondiabetic controls matched for gender and age. AASI and PP were calculated based on 24-h, day, and night BP recordings.

RESULTS

AASI increased from the control group (0.30 +/- 0.14) to the normo- (0.35 +/- 0.15) and microalbuminuric group (0.41 +/- 0.19; P < 0.05). After adjustment for nightly systolic BP reduction and systolic daytime BP variability (s.d.) in multivariate analysis, the association weakened and became nonsignificant (P = 0.078). No significant intergroup differences were found when AASI was calculated separately from day and night BP data. There was no significant difference between day and night AASI. The 24-h PP increased from the control group (48 +/- 7 mm Hg) to the normo- (50 +/- 6 mm Hg) and microalbuminuric group (54 +/- 9 mm Hg; P < 0.01). The association remained in the multivariate analysis. Day and night PPs were higher in microalbuminuric patients compared to healthy controls.

CONCLUSIONS

AASI and PP are higher in microalbuminuric T1DM patients compared to healthy controls. The nocturnal BP reduction and systolic daytime BP variability are determinants of AASI. We propose these associations to reflect biological characteristics of arterial stiffness.