Non-invasive in vivo assessment of changes in peripheral arterial properties with estimation of arterial volume compliance

Arterial volume compliance reduces with age and with arterial disease and its easy non-invasive measurement will be of significant clinical value in monitoring the development of cardiovascular disease or evaluating therapy. However, the relationship between arterial volume compliance and pressure is not fully understood. To enable us to examine changing arterial characteristics, we studied the effect of naturally occurring pressure change, and in this pilot study investigated the effect of ectopic beats. Twenty-five subjects were studied. The electrocardiogram and the peripheral pulses, detected optically at the right ear and right finger, were recorded for subsequent analysis. The difference in pulse transit times between the finger and ear allowed the arm pulse propagation time to be determined, as the effect of ventricular ejection time was common to both measurements and hence removed. Finally, the relative arterial volume compliance changes were estimated based on the Moens–Korteweg equation. The arm pulse propagation time for sinus beats was 58 ± 11 ms (mean ± SD). Ectopic beats induced a significant increase of 7.2 ± 6.9 ms (p < 0.001), those ectopic beats with short coupling intervals to the previous sinus beats a significant increase of 11.4 ± 10.2 ms (p < 0.001) and post-ectopic sinus beats a significant fall of 3.4 ± 4.6 ms (p = 0.001), all relative to the initial sinus beats. Ectopic beats induced a mean 14% increase in the arm pulse propagation time, equivalent to a 31% increase in relative arterial volume compliance. In conclusion, we have demonstrated that dynamic changes in arterial characteristics can be detected at a beat-to-beat level by the measurement of the arm pulse propagation time.