Objectives: Determination of endothelial function has emerged as a crucial factor in the assessment of individual cardiovascular risk. Sonographic measurement of flow-mediated dilation (FMD) is the most widespread technique to assess endothelial function, but analysis is very time-consuming and requires an experienced examiner. Recently, it was speculated that a reduction of small artery compliance (C2) measured by pulse wave analysis might be an indicator of endothelial dysfunction. In the present study, we investigated the correlation of pulse wave analysis parameters and endothelial function with special regard to patients who are at increased risk for endothelial dysfunction.
Methods: One hundred and thirty-six subjects (65 male, 71 female) were included in the study. One hundred and twenty-three probands were hypertensive. Endothelium-dependent vasodilation was assessed sonographically (flow-mediated dilation) using standard protocols and as a change of reflection index (deltaRI) after application of salbutamol by photoplethysmography. Small artery compliance, large artery compliance (C1), and systemic vascular resistance (SVR) were measured by computerized pulse wave analysis of the radial artery (CR-2000; Hypertension Diagnostics, Eagan, Minnesota, USA) and were tested for correlation with FMD.
Results: Mean FMD was 6.29 +/- 2.86%. Means of pulse wave analysis-derived vascular parameters were 4.91 +/- 2.86 ml/mmHg x 100 (C2), 13.35 +/- 5.41 ml/mmHg x 10 (C1) and 1611.6 +/- 348.5 dynes x s x cm(-5) (SVR). Regression analysis excluded a significant correlation between FMD, C2, C1 and SVR (r2 < 0.05 each) both in hypertensives and normotensives. There was no significant correlation between C2 and deltaRI (r2 = 0.023).
Conclusion: Our findings show that static measurement of vascular parameters by an automated pulse-wave analysis procedure cannot be used to assess endothelial function. Further studies are needed to examine whether a dynamic measurement of arterial compliance before and after stimulation of the endothelium (e.g. by ischemia) might quantify endothelial dilatory capacity in a better way.