Aortic pulse wave velocity and reflecting distance estimation from peripheral waveforms in humans: detection of age- and exercise training-related differences

Abstract

We hypothesized that demographic/anthropometric parameters can be used to estimate effective reflecting distance (EfRD), required to derive aortic pulse wave velocity (APWV), a prognostic marker of cardiovascular risk, from peripheral waveforms and that such estimates can discriminate differences in APWV and EfRD with aging and habitual endurance exercise in healthy adults. Ascending aortic pressure waveforms were derived from peripheral waveforms (brachial artery pressure, n = 25; and finger volume pulse, n = 15) via a transfer function and then used to determine the time delay between forward- and backward-traveling waves (Δtf-b). True EfRDs were computed as directly measured carotid-femoral pulse wave velocity (CFPWV) × 1/2Δtf-b and then used in regression analysis to establish an equation for EfRD based on demographic/anthropometric data (EfRD = 0.173·age + 0.661·BMI + 34.548 cm, where BMI is body mass index). We found good agreement between true and estimated APWV (Pearson's R² = 0.43; intraclass correlation = 0.64; both P < 0.05) and EfRD (R² = 0.24; intraclass correlation = 0.40; both P < 0.05). In young sedentary (22 ± 2 years, n = 6), older sedentary (62 ± 1 years, n = 24), and older endurance-trained (61 ± 2 years, n = 14) subjects, EfRD (from demographic/anthropometric parameters), APWV, and 1/2Δtf-b (from brachial artery pressure waveforms) were 52.0 ± 0.5, 61.8 ± 0.4, and 60.6 ± 0.5 cm; 6.4 ± 0.3, 9.6 ± 0.2, and 8.1 ± 0.2 m/s; and 82 ± 3, 65 ± 1 and 76 ± 2 ms (all P < 0.05), respectively. Our results demonstrate that APWV derived from peripheral waveforms using age and BMI to estimate EfRD correlates with CFPWV in healthy adults. This method can reliably detect the distal shift of the reflecting site with age and the increase in APWV with sedentary aging that is attenuated with habitual endurance exercise.

Keywords: aortic stiffness; blood pressure; finger volume pulse; transfer function.

Figures

Fig. 1.

Conversion of peripheral pressure (left) or volume pulse (right) waveforms into ascending (Asc.) aortic pressure waveforms by applying a model transfer function according to Sugimachi et al. (26, 27) and decomposition of the aortic pressure waveform into a forward-traveling and backward-traveling (reflected) wave according to Qasem and Avolio (20). The dotted vertical lines indicate the time delays (Δtf-b) between the forward- and backward-traveling waves. The brachial artery pressure waveform (left) is from a 54-yr-old female subject, and the finger volume pulse waveform (right) is from a 57-yr-old female subject.

Fig. 2.

Correlations between true effective reflecting distance (EfRD) and estimated EfRD and between measured carotid-femoral pulse wave velocity (CFPWV) and estimated aortic pulse wave velocity (APWV). Pearsons's R2 values and intraclass correlation coefficients (ICC) were calculated with data from subjects with invasive brachial artery blood pressure (BP) recordings (●) and subjects with noninvasive finger volume pulse recordings (○) pooled. Both correlations were statistically significant (P < 0.05).

Fig. 3.

Bland-Altman plots for the dependency of the differences between estimated and true EfRD and between estimated APWV (via waveform analysis) and measured CFPWV (via SphygmoCor) from the mean EfRD and mean pulse wave velocity (PWV). Data from subjects with invasive brachial artery BP recordings (●) and subjects with noninvasive finger volume pulse recordings (○) are pooled. CI, confidence interval.

Fig. 4.

EfRD (top) derived from the regression equation established in this study, half of the time delay between the forward- and backward-travelling pressure waves in the ascending aorta (½Δtf-b; middle) derived by waveform analysis, and estimated APWV (bottom) calculated based on EfRD and ½Δtf-b in young sedentary, older sedentary, and older endurance-trained subjects. *Significant difference vs. young sedentary subjects (P < 0.05). †Significant difference vs. older sedentary subjects (P < 0.05).