Noninvasive determination of carotid–femoral pulse wave velocity depends critically on assessment of travel distance: a comparison with invasive measurement

OBJECTIVES: European Society of Hypertension guidelines recommend use of carotid- femoral pulse wave velocity (cfPWV) as a favored measure of aortic stiffness. However, there is no consensus on the measurement of distance travelled by the pulse wave along the aorta to the femoral artery. The aim of our study was to compare cfPWV, calculated with commonly used noninvasive methods for travel distance assessment, against aortic PWV measured invasively. METHODS: One hundred and thirty-five patients had aortic PWV measured invasively during cardiac catheterization, from the delay in wave foot and distance travelled as the catheter was withdrawn from the ascending aorta to the aortic bifurcation. On the following day, noninvasive cfPWV was assessed, using the SphygmoCor system, relating the delay between carotid and femoral wavefoot to travel distance, estimated with five different methods on body surface. RESULTS: Mean travel times were in good agreement (travel time) TTinvasive was 63 ms, TTnoninvasive was 59.3 ms, Spearman's R: 0.8, P < 0.00001. Mean PWVinvasive was 8.5 m/s. CfPWV, as assessed noninvasively, depended largely on the method used for travel distance estimation: 11.5, 9.9, 8.7, 11.9, and 9.6 m/s, using direct carotid-femoral distance, carotid-femoral minus carotid-suprasternal notch distances, suprasternal notch-femoral minus carotid-suprasternal notch distances, suprasternal notch-femoral plus carotid-suprasternal notch distances, and suprasternal notch-symphysis distance, respectively. There was acceptable correspondence between PWVinvasive and cfPWVnoninvasive (Spearman's R: 0.73-0.77, P < 0.0001). CONCLUSION: For noninvasive assessment of cfPWV, estimation of pulse wave travel distance is critical. Best agreement with invasive measurements was found for the method of subtracting carotid-suprasternal notch distance from suprasternal notch-femoral distance.