Exploring the repeatability of pulse arrival time in healthy subjects: A test-retest approach

Objectives: Vascular ageing is increasingly being recognised as a vital marker of cardiovascular morbidity and mortality. Assessment of vascular stiffness is an important parameter in this context. Pulse arrival time (PAT) assessed using photoplethysmography (PPG) and digital electrocardiogram (ECG) signals is a feasible and cost-effective parameter for this assessment. However, there are few, if any, studies that have assessed the test-retest repeatability of this parameter over time. Materials and Methods: We computed PAT using finger PPG and Lead II ECG and measured it sequentially at five instances over a period of 1 month in 21 healthy adults (10 males and 11 females). Mean and diastolic blood pressure (MBP and DBP) and heart rate (HR) were also measured at each visit. A novel parameter, PAT normalised for HR of 75 (PAT-75), was also computed. PAT and PAT-75 were compared for these visits using repeated measures analysis of variance. The intraclass correlation coefficient (ICC) was used to assess the test-retest reliability of this parameter. Results: MBP, DBP, and PAT values did not show any difference between the visits. HR was significantly different between the visits. PAT-75 was significantly lower for the afternoon of day 1 as compared to the forenoon. ICC demonstrated only moderate reliability of PAT (ICC = 0.57), with further reduction observed for PAT-75 (ICC = 0.38). Conclusion: PAT was only moderately repeatable on repeated evaluation over a 1-month period. This finding may have implications for the large-scale applicability of this technology, and therefore, we propose further investigation into the repeatability of this parameter in large cohorts.