Minimum detectable change estimates of heart-to-finger arterial pulse wave conduction time in cardiovascular-healthy young adults

Background

Pulse wave velocity (PWV) measurements are the gold standard for assessing arterial stiffness and estimating time or treatment-related changes in cardiovascular status. What constitutes a statistically significant change is an important clinical consideration. This study aimed to describe the variability of heart-to-finger pulse wave conduction time (PWCT) to provide estimates of the minimum detectable change (MDC) dependent on the number of PWCT samples used.

Materials and methods

Heart-to-finger PWCT was measured based on the time delay between the peak of the EKG R-wave and arterial pulse arrival at the left hand index finger as measured by a photoplethysmographic sensor. Measurements were done in 10 young adults (25.7 ± 1.2 years) while supine for 45 min. Depending on the subject's heart rate, these measurements yielded 2430 to 3750 contiguous PWCT for analysis. The variability in these PWCTs was used to determine the minimal detectable percentage change for specified p-values of 0.05, 0.01, and 0.001.

Results

Sample sizes of 10, 30, 50, or 300 contiguous PWCTs yield similar MDC estimates for a given targeted p-value. The MDC% depended on the chosen p-value, with values of MDC% for p-values of 0.05, 0.01, and 0.001 being 7.8%, 10.5%, and 13.6%.

Conclusions

The estimates may help plan experiments when changes or differences in PWCT or PWV are of interest. Also, these MDC estimates may help assess the validity of clinical study outcomes if PWV changes are outcome measures. The main limitation of the estimates is that they are based on 10 healthy subjects.