Endothelial dysfunction as an early sign of atherosclerosis.

The endothelium, the monolayer covering the inner surface of blood vessels, plays a pivotal role in the regulation of vascular tone and structure, as well as vascular inflammation and thrombosis, i.e., of key events of the atherosclerotic disease process and its clinical complications, such as myocardial infarction and stroke. In particular a reduced endothelial availability of nitric oxide (NO), in part due to increased vascular oxidant stress, has been shown to promote a pro-inflammatory and prothrombotic phenotype of the endothelium. More recently, it has been observed that cardiovascular risk factors reduce the number and impair the function of circulating bone marrow-derived endothelial progenitor cells (EPCs), thereby impairing the endogenous endothelial repair capacity.Importantly, endothelial dysfunction has been identified as a common link of all cardiovascular risk factors. Numerous clinical studies have further demonstrated a close association of the degree of endothelial dysfunction with the risk of future cardiovascular events. Whether endothelial dysfunction can improve cardiovascular risk prediction on top of a careful evaluation of classic cardiovascular risk factors is currently prospectively analyzed in several studies, i.e., in the PREVENT-it study. Furthermore, novel easier to use methods to assess endothelial function are currently explored, i.e., the Endo-PAT system, for their potential in improving cardiovascular risk prediction.At present, assessment of endothelial function and EPCs are highly valuable research tools to improve our understanding of mechanisms of vascular disease and to determine the impact of novel therapeutic approaches on vascular function. Before endothelial function measurements can, however, be recommended in clinical practice for cardiovascular risk assessment, the results of ongoing prospective studies assessing the additive value of these measurements for cardiovascular risk prediction should be awaited.