Enhanced external counterpulsation creates acute blood flow patterns responsible for improved flow-mediated dilation in humans

Enhanced external counterpulsation (EECP) is a FDA-approved treatment for patients with coronary artery disease and unstable angina. Although beneficial effects of EECP have been linked to central/cardiac adaptations, recent findings have shown peripheral/vascular effects. Here, we sought to determine EECP-induced blood flow patterns and their association with vascular function. The present study was designed to investigate endothelium-mediated arterial vasodilation changes after one 45-min session of either EECP or Sham EECP in 18 randomly assigned apparently healthy, young men (25 +/- 4 years). Brachial (b) and femoral (f) flow-mediated dilation (FMD) were assessed before and within 10 min after completing EECP or Sham. After 20 min of EECP, peak blood flow velocity (V) and brachial and femoral artery diameters (D) were recorded live for 2 min. In addition, a blood sample was drawn from the earlobe to determine hematocrit and then to calculate blood viscosity (l) and density (q), Reynolds number (Re = V* D* rho l mu), and endothelial shear stress (ESS = 2 mu* V/D). EECP increased retrograde shear stress and retrograde-turbulent blood flow in the femoral artery and antegrade-laminar shear stress in the brachial artery. fFMD was increased after EECP compared with Sham and baseline (fFMD = 13.1 +/- 3.7 vs. 7.9 +/- 4.6% and 7.8 +/- 4.5%, respectively, P<0.05) and bFMD was increased after EECP compared with baseline (bFMD = 10.6 +/- 4.8 vs. 7.0 +/- 3.5%, P < 0.05), despite different blood flow patterns. These results provide novel evidence that a single session of EECP-induced blood flow patterns improve endothelial function in peripheral muscular conduit arteries. Hypertension Research (2013) 36, 297-305; doi: 10.1038/hr.2012.169; published online 18 October 2012