Spectral inference of arterial stiffness from a single distal velocity waveform

Arterial stiffness is a key determinant of cardiovascular health and a central quantity in biological wave mechanics. Conventional pulse wave velocity (PWV) measurement requires simultaneous recordings at two spatially separated sites, limiting clinical accessibility. Here, we formulate arterial stiffness estimation as a spectral inverse problem: the wave transit time is recovered from a single distal velocity waveform by minimizing the residual between measured harmonic coefficients and those predicted by a parameterized traveling-plus-reflected-wave model. The method exploits phase delays in the harmonic structure of the velocity signal, a physically direct encoding of propagation speed, without a proximal measurement. To evaluate the approach, physiologically realistic waveforms were generated using a 3D fluid-structure interaction model of the aorta across linear and nonlinear arterial wall constitutive regimes as well as different heart rates. Following systematic sensitivity analysis and parameter optimization, the nondimensionalized spectral index showed a strong inverse correlation with reference PWV (r = -0.86, P < 0.001), consistent with the expected reduction in transit time with increasing wave speed. These findings demonstrate that arterial stiffness is robustly encoded in the spectral phase structure of distal velocity waveforms and recoverable via a physics-based inverse approach, providing a pathway toward scalable noninvasive vascular assessment.