Measurement of circulating concentrations of cardiac troponin I and T in healthy subjects: a tool for monitoring myocardial tissue renewal?

The increased analytical sensitivity of the new generation of methods for cardiac troponin I (cTnI) and T (cTnT) has demonstrated that measurable troponin is present in the blood of healthy adult subjects. These data are not in accordance with the prevailing opinion that any reliably detected increase in cardiac troponins should be considered abnormal and potentially caused by cardiac necrosis. The goal of the present review is to discuss the hypothesis that cardiac troponins can be released from cardiomyocytes, even in healthy adult subjects as a result of a process related to "physiological renewal" of the human myocardium and possibly enhanced by physical exercise or aging. The latest generation of high-sensitive cTnI and cTnT immunoassays are characterized by detection limits (DLs) as low as a few picograms. This clearly represents a greater increase in discrimination than that obtained by the most sophisticated cardiac imaging techniques that are commercially available at present. However, the critical question is whether high-sensitive troponin assays are clinically useful and in particular, whether some specific laboratory biomarkers (such as cTnI and cTnT) yield better diagnostic (or prognostic) accuracy and cost-effectiveness when compared with echocardiography in patients with cardiovascular disease. Only specific and well-designed clinical trials will answer this important question.