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.