P1.38 Conversion Between Definitions of Pulse Wave Velocity

Abstract

Background

Different methodologies for determination of carotid-femoral pulse wave velocity (PWV) exist. Distance (L) can be measured from carotid-femoral measurement sites (L_direct) or obtained by subtracting carotid-sternum from sternum-femoral distances (L_subtracted). Transit times are usually obtained either by detection of the maximal upstroke (Δt_{maximal upstroke}) or the foot (Δt_{intersecting tangent}) of the waveform at the measurement sites. This study investigates conversion factors between PWV methodologies.

Methods

3043 subjects in which both distance measurements were available were divided into model and validation groups (1502/1541 subjects, respectively). In the model population the main determinants of the ratio_distance = L_subtracted/L_direct were determined and a multivariate model was constructed. Estimated ratio_distance,est was used to convert from PWV_direct to PWV_{subtracted,est} in the validation population. PWV_{subtracted,est} was compared to measured PWV_subtracted. Ninety three subjects in which both transit times were available were divided into model and validation groups (46/47 subjects, respectively). In the model population a model for estimation of Δt_{maximal upstroke,est} from Δt_{intersecting tangent} was constructed and used to estimate Δt_{maximal upstroke,est} in the validation population. Δt_{maximal upstroke,est} was compared to measured Δt_{maximal upstroke}. Data are presented as mean(stdev).

Results

The main determinants of ratio_distance were age (R² = 0.17) and BMI (R² = 0.15) (combined: R² = 0.27, all P<0.001). PWV_{subtracted,est} correlated well with PWV_subtracted (R = 0.97, P<0.001) with mean difference of 0.0007 (0.40) m/s. Δt_{maximal upstroke,est} correlated well with Δt_{maximal upstroke,est} (R = 0.82, P<0.001) and mean difference of 0.58 (1.03) m/s.

Conclusions

Differences in absolute PWV values are important to compensate for in order to compare between studies. The models proposed allow for such conversion.