Assessment of Arterial Reflection Markers using an A-Mode Ultrasound Device

Abstract

Reflections of arterial blood pulse waves have a pivotal role in the equilibrium of the vasculature. Elevated levels of wave reflections cause an increase in pulse pressure and pulse propagating speeds, exacerbating cardiovascular risk. Quantification of reflection markers is either based on augmentation index or reflection magnitude (RM) and reflection index (RI), both derived from wave separation analysis (WSA). Simultaneous measurement of pressure and flow velocity from the same arterial site is a requirement for WSA and has its practical challenges. Subsequently, simplified WSA based on modelling flow is proposed. This work explores the feasibility of using multi-Gaussian decomposition (MGD) of diameter scaled pressure waveform to perform a WSA and quantify the reflection markers. The diameter waveforms are obtained using an A-mode ultrasound device (ARTSENS®). The decomposed pressure signals scaled from diameter waveforms (or Gaussians) are uniquely combined to yield a forward and backward wave. The reflection markers derived from MGD based WSA are then compared with the clinically relevant stiffness markers and with age. The study was conducted on 110 healthy subjects (60 males and 50 females). A moderately significant correlation <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\mathrm{r} &gt; 0.51,\mathrm{p} &lt; 0.001)$</tex> was obtained for RM and RI when compared with stiffness markers ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\beta$</tex> , Ep, AC, PWV and AIx). The highest correlation was observed for RM versus Ep <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\mathrm{r}= 0.602,\ \mathrm{p} &lt; 0.001)$</tex> , followed by <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\beta$</tex> and PWV. The correlation in reflection markers with age was captured with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{r}=0.51, \mathrm{p} &lt; 0.001$</tex> . A change of 25.2% and 15.4% were observed for the group average RM and RI, respectively, among normotensive and hypertensive subjects in this cohort. The proposed MGD model has the potential to explore the central arterial biomechanics from a diameter or pressure waveform. The variations in reflection markers with stiffness and age derived using the proposed WSA approach were faithfully captured. The flow-independent WSA, combined with a field-deployable measurement device like ARTSENS®, has the potential to conduct large scale vascular screenings in a resource-limited setting.