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

Abstract

Dependence of the ambulatory arterial stiffness index (AASI) on data scattering interferes with its potential clinical relevance. We assessed the correlates and all-cause mortality associations of a modified AASI (s-AASI). AASI was derived from the 24-h diastolic vs systolic blood pressure linear regression line, whereas s-AASI was derived by symmetric regression (bisecting the line of diastolic vs systolic and systolic vs diastolic). Of 2918 patients 55% were women; age was 56 ± 16 years and body mass index was 27.3 ± 4.5 kg/m 2 . Average 24-h ambulatory blood pressure was 138±16/78±10 mm Hg.Applying the modified method for calculating AASI yielded a different measure: the negative correlation between AASI and blood pressure dipping (r ¼ À0.304, Po0.0001) was abolished (r ¼ þ 0.223, Po0.0001), s-AASI was more dependent on age (r ¼ 0.266 vs r ¼ 0.089 for AASI), and prediction of all-cause mortality was enhanced; hazard ratio (95% confidence intervals) 1.17 (1.00-1.36) per 1 s.d. increase in s-AASI in the fully adjusted model as compared with 1.15 (0.97-1.36) for AASI.

The association of a simple blood pressure-independent parameter derived from ambulatory blood pressure variability with short-term mortality

“…6,30 However, the importance of these parameters as measures of arterial properties has been questioned by downplaying the role of AASI as a genuine correlate of arterial stiffness 31,32 because of its strong dependence on age, gender, 31,32 pulse pressure 32 and nocturnal BP decline. 3,25, 32 We report here that the slope-related indices, AASI, AASI(bisect), Slope(bisect) and BPVR, all predict mortality to a certain extent, and that the indices derived from the proper symmetric regression 8 and the calculated BPVR, tend to predict even better. Indeed, after adjustment for age, ambulatory BP level, 24-h PP (an arterial stiffness characteristic) and the corresponding decline of ambulatory BP or PP during sleep (an independent mortality predictor in this patient population 28 ), BPVR remains significantly associated with increased mortality.…”

“…of the 24-h ambulatory BP is available from any report. AASI and its related slope have been shown to predict outcome, 5,7,8,29 as well as target organ damage. 6,30 However, the importance of these parameters as measures of arterial properties has been questioned by downplaying the role of AASI as a genuine correlate of arterial stiffness 31,32 because of its strong dependence on age, gender, 31,32 pulse pressure 32 and nocturnal BP decline.…”

“…4 Slope and AASI have been shown to be independent of mean blood pressure, 3 and to incorporate clinical and prognostic information. [5][6][7][8] One problem in using these parameters in clinical practice is their sensitivity to the estimation method applied: originally, AASI was derived by standard regression [hence, we identify it as AASI(standard)]. 4 Standard regression is known to be an inappropriate estimation method in this case (as systolic and diastolic cannot be described as 'independent' and 'dependent' variables), 9,10 leading to artifactual dependence of AASI(standard) on data scattering, and bias in relating this parameter to clinical variables.…”

The relationship between systolic and diastolic blood pressure: a clinically meaningful slope?

“…12 A modified AASI, calculated with symmetric regression, may reduce its dependence on day-night BP changes and on the correlation between SBP and DBP, and has been associated with all-cause mortality. 32,33 The method, however, has not been compared with direct measures of arterial stiffness, and its clinical and prognostic relevance awaits further confirmation. Notably, symmetric AASI is mathematically connected to the ratio between the standard deviation of 24-h SBP and 24-h DBP (BP variability ratio) 12 (Table 1).…”

The dynamic relationship between systolic and diastolic blood pressure: yet another marker of vascular aging?

“…28 A modified AASI, calculated with appropriate statistical methods (symmetric regression), has been suggested as a method to reduce the dependence of AASI on nocturnal BP reduction and on the correlation between SBP and DBP 28 and has been associated to all-cause mortality. 29,30 The method has, however, not been compared with direct measures of arterial stiffness, and its clinical and prognostic relevance awaits further confirmation. Stergiou et al 15 also used symmetric regres-sion to evaluate ambulatory or home measures of SBP-DBP relationship.…”