Heart-Carotid Pulse-Wave Velocity via Laser-Doppler Vibrometry as a Biomarker for Arterial Stiffening: a Feasibility Study

Background: Pulse-wave velocity (PWV) is the most commonly used biomarker of arterial stiffness and has been proven useful in monitoring arterial stiffness and predicting cardiovascular risk. We previously introduced a Laser doppler vibrometry (LDV) prototype which can measure carotid-femoral PWV (cfPWV). We assessed the feasibility of using the same device to infer heart-carotid PWV (hcPWV). The advantage of hcPWV over cfPWV is that the ascending aorta, which is the most distensible segment of the aorta contributing most to total arterial compliance, is included in the PWV pathway. Methods: Signals were simultaneously acquired from a location on the chest (near either the base or apex of the heart) and the (left/right) carotid artery in 100 subjects, age 19 to 81 (44M, 38F). Fiducial points on the heart waveforms are associated with opening (S1) and closure (S2) of the aortic valve, which can be combined with, respectively, the foot and dicrotic notch of the carotid waveform to retrieve heart-carotid pulse transit times (hcPTT) for hcPWV. Considering two distinct heart-signal measurement sites (base and apex), four hcPTTs estimations are evaluated. Correlations of these hcPTTs with cfPTT, age and blood pressure were evaluated. Results: hcPTTs could be measured in 94% of the subjects. hcPTT derived from S2 from a heart-measurement site located at the base of the heart with the carotid dicrotic notch provided the strongest correlations with age (r=-0.377, P<0.001) and cfPTT (r=0.475, P<0.001). Conclusions: We conclude that LDV may provide a corollary biomarker of arterial stiffness, encompassing the ascending aorta.