Are there really biomarkers of vulnerable plaque?

The rationale for the search of biomarkers of vulnerable plaques seems sound. Plaque rupture is a key step in the initiation of an acute coronary syndrome (ACS). The atherosclerotic plaque contains large numbers of inflammatory cells that may release hydrolytic enzymes and cytokines, thereby destabilizing the plaque (1 ). Therefore, many inflammatory biomarkers and enzymes have been suggested as potential biomarkers of vulnerable plaques; however, considerable confusion exists in the literature regarding what is meant by “a biomarker of plaque vulnerability,” and other closely related (but not identical) concepts have emerged as alternatives. These concepts are described briefly below.