Agreement Between Single- And Double-point Estimations Of Pulse Wave Velocity

Abstract

Aortic pulse wave velocity (PWV) is a common measure of large artery stiffness, and an independent predictor of cardiovascular disease risk. Currently, the gold standard PWV measure, carotid-femoral pulse wave velocity (cfPWV), is taken using two arterial sites. A single-point method of PWV would be useful as it would decrease required operator training and patient burden. PURPOSE: To assess (1) overall, and (2) repeated measures (RM) agreement, between cfPWV and two test measures, which estimate aortic PWV from the brachial artery. METHODS: The criterion cfPWV measure was obtained with carotid and femoral artery oscillometric cuffs. Brachial-based PWV was obtained using the BP+ device (PWVBP) and the Mobil-o-graph device (PWVMOG). Measurements were made in the supine, then semi-recumbent, then seated position. Postural change was used as a hemodynamic perturbation for ascertainment of RM agreement. Multi-level correlation was used to calculate overall agreement (independent of posture), and RM correlation was used to determine whether change (i.e., with change in posture) in the test measure agrees with change in the criterion. Strength of agreement was interpreted as the intraclass correlation coefficient (ICC), with estimates of <0.2, 0.2, 0.4, 0.7, and 0.9 representing negligible, weak, moderate, strong, and very strong agreement, respectively. RESULTS: Complete data was collected for 30 subjects (age: 24 ± 5.5 years, 57% female). cfPWV increased approximately 1m/s from the supine to semi-recumbent, and from the semi-recumbent to seated posture. The overall and RM agreements between PWVMOG and cfPWV were weak, with the ICC: 0.35, 95%CI [0.15, 0.52] and ICC -0.28, 95% CI [-0.50, -0.02], respectively. The overall agreement between PWVBP and cfPWV was moderate (ICC 0.50, 95% CI [0.32, 0.64]) and the RM agreement was weak (ICC 0.30, 95% CI [0.05, 0.52]). Limits of agreement plots indicated bias, with both single-point methods producing lower PWV than the criterion. CONCLUSIONS: The results show PWVMOG weakly but significantly agreed with cfPWV, whereas PWVBP moderately and significantly agreed with cfPWV. RM agreement was weak, likely because both single point-measures changed minimally with postural change, whereas the criterion device recorded expected increases in PWV with more upright posture.