Development of a non-invasive multifaceted evaluation system for arterial function under transmural pressure manipulation

A novel apparatus for multifaceted evaluation of arterial function was developed in which functions of endothelial cells and smooth muscle cells and the function of the artery as a conduit tube, i.e., mechanical properties were measured. A rigid airtight chamber with an ultrasound probe was attached to the upper arm to manipulate transmural pressure (TP) of the brachial artery by changing the pressure in the chamber. Pressure-diameter curve of the artery was obtained by measuring the diameter change with the probe during TP manipulation. Endothelial function was measured with a standard FMD (flow-mediated dilation) protocol. Smooth muscle function was evaluated with its myogenic response, pressure-mediated contraction (PMC), i.e., spontaneous contraction of the artery following its stepwise passive dilation caused by the stepwise application of negative pressure to the chamber. Examples of pressure-diameter curves, FMD and PMC results are presented. Pressure-diameter relationship of the brachial artery could be obtained reproducibly over a wide range of TP. Contrary to intuition, the diameter decreased and increased when TP increased and decreased, respectively, in some TP ranges. PMC and FMD measurements showed reasonable results with active contraction and dilation of smooth muscle cells, respectively. This apparatus may be useful to measure not only pressure-diameter relationship but also contractility of smooth muscle cell.