Dirk G. Dechering

Short-term and long-term repeatability of the morning blood pressure in older patients with isolated systolic hypertension

Objective Using 24-h ambulatory blood pressure monitoring, we studied the repeatability of the morning blood pressure in older (≥60 years) patients with isolated systolic hypertension. Methods The sleep-through morning surge was the morning blood pressure minus the lowest nighttime blood pressure. The preawake morning surge was the morning blood pressure minus the preawake blood pressure. In addition, we determined the cusum plot height of blood pressure from 04:00 to 10:00 h from a plot of cumulative sums. Results In 173 patients with repeat recordings within 33 days (median), the short-term repeatability coefficients, expressed as percentages of maximal variation, ranged from 35 to 41% for the daytime and nighttime blood pressures and from 50 to 56% for the night-to-day blood pressure ratios. Short-term repeatability ranged from 52 to 75% for the sleep-through and the preawake morning surge, and from 51 to 62% for the cusum plot height. In 219 patients with repeat recordings within 10 months (median), the corresponding long-term estimates ranged from 45 to 64%, from 69 to 71%, from 76 to 83%, and from 50 to 78%, respectively. In categorical analyses of the short-term repeatability of the sleep-through morning surge and the preawake morning surge, using the 75th percentile as arbitrary cut-off, surging status changed in 28.0 and 26.8% of patients (κ-statistic ≤0.33). In the long-term interval, these proportions were 32.0 and 32.0%, respectively (κ-statistic ≤0.20). The κ-statistic threshold for moderate reproducibility is 0.4. Conclusion The morning surge of blood pressure is poorly reproducible, irrespective of whether it is analysed as continuous or categorical variable.

Thirty years of research on diagnostic and therapeutic thresholds for the self-measured blood pressure at home.

ObjectiveThe goal of this review study is to summarize 30 years of research on cut-off limits for the self-measured blood pressure. MethodsWe reviewed two meta-analyses, several prospective outcome studies in populations and hypertensive patients, studies in pregnant women, three clinical trials and the thresholds proposed in earlier and current hypertension guidelines. ResultsIn line with existing guidelines, prospective studies support that levels of the self-measured blood pressure at home of greater than or equal to 135 mmHg systolic or greater than or equal to 85 mmHg diastolic indicate hypertension. Circumstantial data suggest that levels of the self-measured blood pressure below 120/80 and 130/85 mmHg are optimal and normal, respectively. Therapeutic targets of the self-measured blood pressure to be attained on antihypertensive drug treatment are currently unknown, but should logically be lower (<135/85 mmHg) than those used to diagnose hypertension. Currently, there is no proof that therapeutic thresholds for the home blood pressure should be lower in high-risk compared with normal-risk patients. A large body of evidence, however, demonstrated that each millimetre of mercury of blood pressure lowering counts in the prevention of cardiovascular complications and that in high-risk patients even small decreases in blood pressure result in large absolute benefit. ConclusionThe thresholds to diagnose hypertension from self-measured blood pressure readings at home remain unaltered since the 2000 consensus conference, but are currently supported by outcome data. Further studies need to establish what values of the self-measured blood pressure are optimal and normal in terms of cardiovascular outcome.

Determinants of the Ambulatory Arterial Stiffness Index in 7604 Subjects From 6 Populations

The ambulatory arterial stiffness index (AASI) is derived from 24-hour ambulatory blood pressure recordings. We investigated whether the goodness-of-fit of the AASI regression line in individual subjects (r2) impacts on the association of AASI with established determinants of the relation between diastolic and systolic blood pressures. We constructed the International Database on the Ambulatory Blood Pressure in Relation to Cardiovascular Outcomes (7604 participants from 6 countries). AASI was unity minus the regression slope of diastolic on systolic blood pressure in individual 24-hour ambulatory recordings. AASI correlated positively with age and 24-hour mean arterial pressure and negatively with body height and 24-hour heart rate. The single correlation coefficients and the mutually adjusted partial regression coefficients of AASI with age, height, 24-hour mean pressure, and 24-hour heart rate increased from the lowest to the highest quartile of r2. These findings were consistent in dippers and nondippers (night:day ratio of systolic pressure ≥0.90), women and men, and in Europeans, Asians, and South Americans. The cumulative z score for the association of AASI with these determinants of the relation between diastolic and systolic blood pressures increased curvilinearly with r2, with most of the improvement in the association occurring above the 20th percentile of r2 (0.36). In conclusion, a better fit of the AASI regression line enhances the statistical power of analyses involving AASI as marker of arterial stiffness. An r2 value of 0.36 might be a threshold in sensitivity analyses to improve the stratification of cardiovascular risk.

Interstudy Variability in the Ambulatory Arterial Stiffness Index

To the Editor: In 2006, Li et al1 proposed the ambulatory arterial stiffness index (AASI) as a novel marker for arterial stiffness. AASI is derived from the linear relationship between systolic blood pressure and diastolic blood pressure observed using 24-hour ambulatory blood pressure monitoring. The literature published on this topic shows some large differences in the mean AASI between studies. In our opinion, these differences cannot be fully accounted for by differences in methodology and patient characteristics. The Table shows a review of important issues of methodology and …

Reproducibility of the ambulatory arterial stiffness index in hypertensive patients.

Background We studied the repeatability of the ambulatory arterial stiffness index (AASI), which can be computed from 24-h blood pressure (BP) recordings as unity minus the regression slope of diastolic on systolic BP. Methods One hundred and fifty-two hypertensive outpatients recruited in Nijmegen (mean age = 46.2 years; 76.3% with systolic and diastolic hypertension) and 145 patients enrolled in the Systolic Hypertension in Europe (Syst-Eur) trial (71.0 years) underwent 24-h BP monitoring at a median interval of 8 and 31 days, respectively. We used the repeatability coefficient, which is twice the SD of the within-participant differences between repeat recordings, and expressed it as a percentage of four times the SD of the mean of the paired measurements. Results Mean AASI (crude or derived by time-weighted or robust regression) and 24-h pulse pressure (PP) were similar on repeat recordings in both cohorts. In Nijmegen patients, repeatability coefficients of AASI and PP were ∼50%. In Syst-Eur trial patients, repeatability coefficient was ∼60% for AASI and ∼40% for PP. For comparison, repeatability coefficients for 24-h systolic and diastolic BP were ∼30%. Differences in AASI between paired recordings were correlated with differences in the goodness of fit (r2) of the AASI regression line as well as with differences in the night-to-day BP ratio. However, in sensitivity analyses stratified for type of hypertension, r2, or dipping status, repeatability coefficients for AASI did not widely depart from 50 to 60% range. Conclusion Estimates of mean AASI were not different between repeat recordings, and repeatability coefficients were within the 50–60% range.

Putting a spin on the ambulatory arterial stiffness index.

Division of Hypertension and Cardiac Rehabilitation, Department ofCardiovascular Diseases, University of Leuven, Leuven, BelgiumCorrespondence to Jan Staessen, Studies Coordinating Centre, Division ofHypertension and Cardiovascular Rehabilitation, Department of CardiovascularDiseases, University of Leuven, Campus Gasthuisberg, Herestraat 49, Box 702,B-3000 Leuven, BelgiumTel: +32 16 34 7104; fax: +32 16 34 7106;e-mail: jan.staessen@med.kuleuven.be

The Use of the Ambulatory Arterial Stiffness Index in Patients Suspected of Secondary Hypertension

The ambulatory arterial stiffness index (AASI) is a marker of arterial stiffness and is derived from ambulatory 24-h blood pressure registration. We studied whether the AASI could be used as a predictive factor for the presence of renal artery stenosis (RAS) in patients with a suspicion of secondary hypertension and as such as a diagnostic tool for RAS. We included 169 patients with difficult-to-treat hypertension. They all underwent 24-h ambulatory blood pressure monitoring registration, imaging of the renal arteries, and cardiovascular risk measurement, including smoking, history, biometrics, blood pressure, renal function, lipids, and glucose metabolism. Performing univariate and multivariate analyses, we investigated if AASI and the other cardiovascular risk factors were related to the presence of RAS. Of the 169 patients (49% women), 31% had RAS. The mean AASI was 0.44 (0.16). The presence of RAS showed no significant correlation with AASI (r = 0.14, P = 0.06). Age (r = 0.19, P = 0.01), hypercholesterolemia (r = 0.26, P = 0.001), history of CVD (r = 0.22, P = 0.004), and creatinine clearance (r = −0.34, P < 0.001) all demonstrated a correlation with RAS. Although AASI is higher in patients with RAS, AASI does not independently predict the presence of RAS in hypertensive subjects.

335 THE AMBULATORY ARTERIAL STIFFNESS INDEX HAS LITTLE IMPACT ON THE DETECTION OF RENAL ARTERY STENOSIS IN HYPERTENSIVE PATIENTS

Aims: Atherosclerotic Renal Artery Stenosis (RAS) shares a pathophysiological link with arterial stiffness. Both indicate a higher risk of cardiovascular disease, but the relation is not clear. We investigated the relation between RAS and AASI and evaluated AASI as predictive factor for RAS, as well as its suitability as a diagnostic tool for RAS. Methods: The population researched comprised of 169 hypertensive patients. Patients underwent a 24-hour ABPM registration, imaging of the renal arteries and measurement of relevant parameters for the uncovering of secondary hypertension. We used the commonly agreed definition of AASI. Vascular radiologists measured the presence and the degree of RAS. Using univariate and multivariate analyses, we investigated if AASI and other risk factors (sex, age, (LDL) cholesterol, history of CVD, renal failure, 24-hour blood pressure, pulse pressure, resistance to antihypertensive treatment and diabetes) were related to RAS and to what extent they could predict the presence of a renal artery stenosis. Results: Of the 169 patients (49% women) with a mean age (SD) of 48.0 (13.5) years and a mean AASI of 0.44 (0.16), 31% were classified as having a RAS. The presence of RAS did not significantly correlate with AASI (r=0.14, p=0.06). Age (r=0.19, p=0.01), hypercholesterolemia (r=0.26, p=0.001), history of CVD (r=0.22, p=0.004) and creatinine clearance (r=-0.34, p<0.001) showed a significant correlation with RAS. Conclusions: Although AASI is higher in patients with a RAS, AASI does not independently predict the presence of RAS in hypertensive subjects. Therefore AASI cannot be used as a test for RAS.

Response to Determinants of the Ambulatory Arterial Stiffness Index Regression Line

We thank Schillaci and colleagues for their continued interest1–3 in the ambulatory arterial stiffness index (AASI). Schillaci et al1 reported that the inverse association between AASI and nocturnal dipping is stronger for diastolic than for systolic blood pressure. This observation has no repercussion on r 2, which is a measure of fit of the regression line. When A (diastolic blood pressure) is regressed on B (systolic blood pressure) or vice versa, estimates of r 2 are exactly the same. With regard to the proposed threshold value of r 2 (0.36), Schillaci and colleagues …