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 ± 1.3 cm for D(0.8)) leading to higher values of PWV (0.6 ± 0.3 m/s for PWV(0.8)). 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.