Troponin elevation: is it ischemia?

Cardiac troponin is the preferred biomarker for myocardial infarction, thanks to its sensitivity and absolute specificity for the heart. The availability of high-sensitivity assays (hs-cTnT and hs-cTnI), capable of measuring with excellent analytical precision very low levels of circulating troponin, raised the issue of whether transient ischemia is a sufficient stimulus for troponin release. For this purpose, in a series of patients submitted to a stress test (exercise ECG/echo test; dipyridamole echo test; dobutamine echo test), we measured plasma levels of hs-cTnT at baseline and 6 hours after the end of the test. Plasma concentrations of hs-cTnT significantly increased in the vast majority of patients after the test. Significant elevations were documented in response to each stressor, regardless of the test result, after both positive and negative tests. Moreover, troponin significantly increased in response to the stress, both in patients with and in patients without obstructive coronary artery disease. Despite a good sensitivity (80% and 89%), troponin showed a very low specificity (32% and 47%) for stress-induced ischemia and coronary artery disease, respectively. Myocardial release of troponin is a multifactorial process, mediated not only by cardiomyocyte necrosis, but also through several different mechanisms such as myocardial ischemia, increase in cardiac work, and hemodynamic overload. Transient elevation of high sensitivity cardiac troponin is not a useful tool for detecting spontaneous or stress-induced ischemia. L