Crucial importance of using a sliding calliper to measure distance for carotid-femoral pulse wave velocity assessment

Background and objectives: In the past, different methods have been used to measure the carotid-femoral distance for the assessment of pulse wave velocity (PWV). However, the latest consensus published advises to use 80% of the direct straight carotid-femoral distance (D-0.8) using either a flexible tape or a sliding calliper. We studied the influence of the use of a tape measure and a calliper on PWV values and provided equations to derive the straight D-0.8 distance from previous methodologies. Methods: PWV was measured in patients referred for ambulatory blood pressure monitoring. Carotid-femoral, carotid-sternal notch, and sternal notch-femoral distances were measured with a tape and a sliding calliper. Results: Two hundred and fifty-nine patients (141 men and 118 women) were recruited consecutively. Their BMI ranged from 18 to 45 kg/m(2) (28.4 +/- 5.0, mean +/- SD). As expected, distances measured with tape were longer (3.1 +/- 1.3cm for D-0.8) leading to higher values of PWV (0.6 +/- 0.3 m/s for PWV0.8). This difference was similar in men and women and depended for 20% on the BMI. Equations explaining more than 85% of variance can be used to convert tape carotid-femoral, carotid-sternal notch, and tape sternal notch-femoral distances to D-0.8. Conclusion: It is crucial to use a sliding calliper to assess distances for PWV measurement. The overestimation with flexible tape depends on the BMI but not on the sex. Conversion equations between previous methods and the D-0.8 method can be used.