An in-silico study of the effects of cardiovascular ageing on carotid flow waveforms and indices in a virtual population.

Cardiovascular aging is strongly associated with increased risk of cardiovascular disease and mortality. Health and lifestyle factors may accelerate age-induced alterations, such as increased arterial stiffness and wall dilation, beyond chronological age, making the clinical assessment of cardiovascular aging an important prompt for preventative action. Carotid flow waveforms contain information about age-dependent cardiovascular properties, and their ease of measurement via non-invasive Doppler ultrasound (US) makes their analysis a promising tool for the assessment of cardiovascular aging. In this work, the impact of different aging processes on carotid waveform morphology and derived indices is studied in-silico to evaluate the clinical potential of a carotid US-based assessment of cardiovascular aging. One-dimensional (1D) hemodynamic modeling was employed to generate an age-specific virtual population (VP) of N=5,160 carotid waveforms. The VP was statistically validated against in-vivo waveforms and indices from the literature, and simulated waveforms were studied in relation to age and underlying cardiovascular parameters. In our study, the carotid flow augmentation index (FAI) significantly increased with age (median increase of 50% from youngest to eldest age group) and was strongly correlated to local arterial stiffening (r=0.94). The carotid pulsatility index (PI) was inversely correlated with the reflection coefficient at the carotid branching (r=-0.88), and directly correlated with carotid net forward wave energy (r=0.90). There was a high correlation between corrected carotid flow time (ccFT) and cardiac output (r=0.99), which was not affected by vascular age. This study highlights the potential of carotid waveforms as a valuable tool for the assessment of cardiovascular aging.