Dependency of flow‐mediated vasodilatation from basal nitric oxide activity
Dennis Kannenkeril, Agnes Bosch, Julie Kolwelter, Susanne Jung, Kristina Striepe, Christian Ott, Christian Delles, Roland E. Schmieder
Abstract
Abstract Background Flow‐mediated vasodilatation (FMD) has become one of the most widely assessed parameters to analyse endothelial and vascular function in cardiovascular medicine. The degree of contribution of nitric oxide (NO) to FMD is inconclusive and varies widely depending on the device used. In this study, we used a semi‐automatic ultrasound device to analyse to what extent basal NO activity contributes to FMD of the brachial artery. Methods FMD was assessed with the UNEX EF device in a cross‐over single blinded randomized study at baseline and then during infusion of either a NO‐synthase‐inhibitor (NG‐monomethyl‐L‐arginine (L‐NMMA)) or saline. The analysis was repeated after 1 week with the alternative infusion of L‐NMMA or saline. All measurements were analysed both automatically and by a technician manually. Results In total, 25 healthy men subjects completed the study. Diastolic blood pressure and heart rate significantly changed during infusion of L‐NMMA. Infusion of L‐NMMA reduced FMD significantly (−37%, p = 0.002). Saline solution had no effect on FMD (+14%, p = 0.392). Change in FMD was significantly different between the groups (ΔFMD L‐NMMA vs. ΔFMD saline , p = 0.032). There was a statistically significant correlation between automatically analysed results and those obtained by an experienced technician (FMD saline : r = 0.822, p < 0.001; FMD L‐NMMA : r = 0.645, p = 0.007). Conclusion The influence of NO on FMD is approximately 40% if assessed using the UNEX EF. Prior to use FMD as a marker of endothelial dysfunction, we should explore different methods including various duration of forearm ischaemia to increase NO dependency of FMD.