Organ-Specific, Age-Dependent Associations of Steady-State Pressures and Pulsatile Pressure Wave Components With End-Organ Measures

Relation of forward and backward traveling pressure waves with subclinical carotid artery wall remodeling and central pulse pressure

Central pulse pressure (PP) is the sum of forward and backward traveling pressure waves that have been associated with cardiovascular disease (CVD) risk. However, previous studies have reported differential findings regarding the importance of the forward versus the backward wave for CVD risk. Therefore, we sought to determine the degree to which the forward and backward pressure waves are associated with subclinical carotid artery wall remodeling and central PP in healthy adults. Using applanation tonometry, carotid pressure waveforms were acquired in 308 healthy individuals (aged 45 ± 17 years, range 19-80 years, 61% women), from which the time integral of the forward (PfTI) and backward (PbTI) pressure waves were derived via pressure-only wave separation analysis. Common carotid artery intima-media thickness (cIMT), a biomarker of subclinical CVD risk, was derived via B-mode ultrasonography measured ∼2 cm from the carotid bulb. Both PfTI (r = 0.31, P < 0.001) and PbTI (r = 0.40, P < 0.001) were correlated with cIMT. However, further analysis revealed that PbTI mediated the relation between PfTI and cIMT (proportion mediated = 156%, P < 0.001). The association between PbTI and cIMT remained after adjusting for age, sex, body mass index, blood glucose, low-density lipoprotein cholesterol, heart rate, brachial systolic pressure, and aortic stiffness (B = 0.02, 95% confidence interval = 0.01, 2.77, P < 0.001). Both PfTI (r = -0.58, P < 0.001) and PbTI (r = -0.50, P < 0.001) were correlated with central PP, however, PfTI fully mediated the association between PbTI and central PP (proportion mediated = 124%, P < 0.001). Although PfTI is correlated with higher central PP, it is PbTI that is directly associated with carotid artery wall remodeling.NEW & NOTEWORTHY The present study contributes to the growing body of evidence highlighting the physiological and clinical insight provided by the pulsatile hemodynamic components of central artery pulse pressure. The notable findings of this study are: 1) The reflected (backward) pressure wave is associated with carotid intima-media thickness independent of traditional cardiovascular risk factors, including systolic blood pressure and aortic stiffness. 2) The incident (forward) pressure wave, and not the reflected pressure wave, is associated with greater central pulse pressure.

Association of Pressure Wave Reflections With Left Ventricular Mass: a Systematic Review and Meta-Analysis

BACKGROUND

Pressure wave reflections (PWRs) within the circulation are assessed at various arterial sites by various noninvasive methods. We aimed at reviewing the conflicting data regarding the hypothesis that higher PWRs are associated with higher left ventricular mass and tested whether this association stands for all available indices of PWRs, all (proximal or distal to the heart) sites of assessment, and is modified by sex, age and heart rate.

METHODS

Based on a predefined protocol applying the Meta-Analysis of Observational Studies in Epidemiology (MOOSE) guidelines, we identified eligible for meta-analysis data regarding: augmentation index, augmentation pressure, backward pressure (Pb), reflection index, and their association with left ventricular mass index (19 studies, total population n=8686).

RESULTS

We found statistically significant associations, independent from blood pressure level, for all indices of PWRs at all arterial sites (carotid augmentation index; odds ratio; standardized beta coefficient [β]: 0.14 [95% CI, 0.07% to 0.21%], per SD increase), radial augmentation index (β: 0.21; 0.11 to 0.31), central augmentation pressure (β: 0.15; 0.03 to 0.27), central Pb (β: 0.23; 0.05 to 0.42), and central reflection index (β: 0.14; 0.06 to 0.22), except for aortic augmentation index as estimated by generalized transfer functions. Meta-regression analysis showed that the association between carotid augmentation index and left ventricular mass was higher among populations with higher heart rate (P=0.036, beta: 0.017 [95% CI, 0.001 to 0.033]) and tended to be higher in middle-aged (P=0.07, beta: -0.001; -0.021 to 0.001).

CONCLUSIONS

A clinically meaningful association between PWRs and left ventricular mass, assessed at either central or peripheral arterial sites by most available methods was shown, suggesting that PWR reduction strategies might be useful. Based on the present evidence, such trials should target middle-aged populations with high normal heart rate.

Pulse wave velocity in South African women and children: comparison between the Mobil-O-Graph and SphygmoCor XCEL devices

BACKGROUND

Carotid-femoral pulse wave velocity (PWV) is the gold-standard noninvasive measure of arterial stiffness. Data comparing tonometry-based devices such as the SphygmoCor XCEL to simpler brachial-cuff-based estimates of PWV, such as from the Mobil-O-Graph in African populations are sparse. We therefore aimed to compare PWV measured by the Mobil-O-Graph and the SphygmoCor XCEL device in a sample of South African women and children.

METHODS

Women (n = 85) 29 years [interquartile range (IQR): 29-69] and their children/grandchildren (n = 27) 7 years (IQR: 4-11) were recruited for PWV measurement with Mobil-O-Graph and SphygmoCor XCEL on the same day. Wilcoxon signed-rank test, regression analysis, spearman correlation and Bland-Altman plots were used for PWV comparison between devices.

RESULTS

For adults, the SphygmoCor XCEL device had a significantly higher PWV (7.3 m/s, IQR: 6.4-8.5) compared with the Mobil-O-Graph (5.9 m/s, IQR: 5.0-8.1, P = 0.001) with a correlation coefficient of 0.809 (P ≤ 0.001). Bland--Altman analysis indicated an acceptable level of agreement but significant bias (mean difference PWV: 0.90 ± 1.02 m/s; limits of agreement: -1.10 to 2.90). The odds of having a PWV difference more than 1 m/s decreased with a higher age [odds ratio (OR): 0.95, 95% confidence interval (95% CI) = 0.92-0.98] and increased with greater height (OR: 1.10, 95% CI = 1.01-1.21, P = 0.03) in multivariable analysis. In children, the Bland-Altman indicated an excellent level of agreement (-0.03 ± 0.63 m/s; limits of agreement: -1.26 to 1.21), but no correlation was found (rs = 0.08, P = 0.71).

CONCLUSION

Particularly in younger and taller women, the Mobil-O-Graph significantly underestimated PWV compared with the SphygmoCor. Although no correlation was found between the two devices for children, further research is required due to the small sample size. Furthermore, the clinical value of both methods in young African populations requires further investigation.

Marked Arterial Functional Changes in Patients With Arterial Vascular Events Across the Early Adult Lifespan

Objective:

The age at which arteriosclerosis begins to contribute to events is uncertain. We determined, across the adult lifespan, the extent to which arteriosclerosis-related changes in arterial function occur in those with precipitous arterial events (stroke and critical limb ischemia).

Approaches and Results:

In 1082 black South Africans (356 with either critical limb ischemia [n=238] or stroke [n=118; 35.4% premature], and 726 age, sex, and ethnicity-matched randomly selected controls), arterial function was evaluated from applanation tonometry and velocity and diameter measurements in the outflow tract. Compared with age- and sex-matched controls, over 10-year increments in age from 20 to 60years, multivariate-adjusted (including steady-state pressures) aortic pulse wave velocity, characteristic impedance (Zc), forward wave pressures (Pf), and early systolic pulse pressure amplification were consistently altered in those with arterial events. Increases in Zc were accounted for by aortic stiffness (no differences in aortic diameter) and Pf by changes in Zc and not aortic flow or wave re-reflection. Multivariate-adjusted pulse wave velocity (7.48±0.30 versus 5.82±0.15 m/s, P <0.0001), Zc ( P <0.0005), and Pf ( P <0.0001) were higher and early systolic pulse pressure amplification lower ( P <0.0001) in those with precipitous events than in controls. In comparison to age- and sex-matched controls, independent of risk factors, pulse wave velocity, and Zc ( P <0.005 and <0.05) were more closely associated with premature events than events in older persons and Pf and early systolic pulse pressure amplification were at least as closely associated with premature events as events in older persons.

Conclusions:

Arteriosclerosis-related changes in arterial function are consistently associated with arterial events beyond risk factors from as early as 20 years of age.