Heart-Carotid Pulse Wave Velocity for Non-invasive Vascular Stiffness Assessment: A Feasibility Study

Carotid-femoral pulse wave velocity (cfPWV) is one of the established markers of aortic arterial stiffness with proven predictive capability for adverse cardiovascular events. Despite a large body of clinical evidence, cfPWV is not routinely assessed in clinical practice nor used for ambulatory or self-monitoring, as it requires access to the femoral site, which leads to poor subject compliance for the assessment. Heart-carotid PWV (hcPWV) is a potential alternative for measuring aortic arterial stiffness in settings where cf-PWV is challenging to measure. We introduce a novel device for easy and reliable measurement of hcPWV, using simultaneously acquired phonocardiogram (PCG) signals at the heart and photoplethysmography (PPG) signals at the carotid. This study aimed to evaluate the feasibility of in-vivo measurements of hcPWV in 30 subjects and examine its association with cfPWV. The agreement between hcPWV and cfPWV was assessed using Pearson's correlation coefficient (r). The study demonstrated that the measured signal provided repeatable beat-to-beat pulse transit time (PTT) with a CoV <12%. The mean hcPWV and cfPWV values were 4.67 ± 0.95 m/s and 6.17 ± 1.17 m/s, respectively. A strong agreement was observed between hcPWV and cfPWV (r = 0.71, p <0.001), indicating good reliability of hcPWV on par with cfPWV. The findings suggest promising potential for hcPWV as a reliable measure, with implications for its use in settings where cfPWV is challenging to measure. However, while this study indicates a strong agreement, a comprehensive large-scale investigation is warranted further to validate the efficacy of hcPWV in comparison to cfPWV. In the future, this device can potentially be developed into wearable technology for self-measurement in homecare or ambulatory use cases.