Abstract 13899: Acute Effects of Enhanced External Counterpulsation on Flow Mediated Dilation are Related to Retrograde Turbulent and Antegrade Laminar Blood Flow Patterns
Enhanced External Counterpulsation (EECP) is a FDA-approved non-invasive intervention for CAD patients with refractory angina. However, the mechanisms responsible for clinical benefits are yet to be determined. We hypothesized that a single EECP session would improve brachial and femoral artery flow mediated dilation (FMD) due to acute alterations in blood flow patterns induced by the cuff compressions. Eighteen apparently healthy, young men (25 ± 4 years) were randomly assigned to one 45-minute session either sham- or active-EECP. Brachial (b) and femoral (f) FMD were assessed before and within 10 minutes after completing EECP using high resolution ultrasound and Doppler and analyzed off-line with edge-detection software. After 20 minutes of EECP, blood flow velocity (V) and artery diameters (D) were recorded live for 2 minutes for further off-line analysis. In addition, mean arterial (MAP), aortic systolic (ASBP) and diastolic (ADBP) pressures were assessed before and during EECP using applanation tonomtery, and a blood sample was drawn to determine hematocrit, blood viscosity (μ) and density (ρ), and Reynolds number (Re =V*D*ρ/μ). Two-way repeated measurements ANOVA were performed and statistical significance was set at α=0.05. fFMD was increased after active-EECP compared to sham (fFMD= 13.1 ± 1.4% vs. 7.9 ± 1.4%, p<0.05) and bFMD was increased after active-EECP compared to before EECP (bFMD= 10.6 ± 1.3% vs. 7.0 ± 1.2%, p<0.05). MAP and ADBP were increased during active-EECP compared to sham (MAP= 98 ± 3 vs. 81 ± 3 mmHg, ADBP= 111 ± 3 vs. 77 ± 3 mmHg, p<0.05). Brachial antegrade shear stress and femoral retrograde turbulent Re were increased during active-EECP compared to sham (58.1 ± 13.2 vs. 29.9 ± 7.3 dynes•cm−2, and 8811 ± 4410 vs. 274 ± 140, respectively, p<0.05) indicative of increased laminar antegrade and retrograde turbulent blood flow in the brachial and femoral artery, respectively. These results provide, for the first time, acute evidence in support of the hypothesis that EECP improves peripheral arterial function. EECP compressions create blood flow stimuli that appear to upregulate endothelial function. Improved peripheral vascular function may be a primary mechanism responsible for the anti-ischemic clinical benefits of EECP.
- © 2010 by American Heart Association, Inc.