The influence of exercise upon cardiac biomarkers: a practical guide for clinicians and scientists

The field of diagnostic cardiac biomarkers has grown exponentially since the development of an assay for aspartate transaminase activity to diagnose myocardial infarction in 1954. The clinician now has a vast array of clinical tools, which include biomarkers of inflammation, ischaemia and necrosis as well as sensitive imaging technology and coronary anatomy intervention at their disposal when evaluating acute coronary syndromes. Previously the World Health Organisation (1979) defined a myocardial infarction (MI) in the presence of two of the following triad: History of chest pain, electrocardiographic (ECG) changes and a rise in cardiac enzymes to twice the upper limit of normal. At this time, creatine kinase and its MB isoenzyme were the preferred biochemical markers. The clinical requirements of early diagnosis, risk stratification and effective treatment have stimulated the development of numerous new and cardiac specific biomarkers (e.g. cardiac troponins). Cardiac troponins are now integral to the diagnosis of MI and have led to the reclassification of MI into either ST elevated MI (STEMI) or non-ST elevated MI (NSTEMI). Subsequent to the release of each new cardiac specific assay there typically follows an array of studies supporting or refuting its efficacy. Many cardiac biomarkers originally proposed with high sensitivity and specificity for ACS are now of questionable clinical value or require the addition of significant caveats once they have been fully evaluated. Indeed, acute exercise often stimulates perturbations in cardiac biomarkers; such as elevations in creatine kinase, cardiac troponins or reductions in Ischemia Modified Albumin (IMA). Such an influence of exercise upon commercially available cardiac biomarkers may hamper or distort the viability of such assays in the clinical arena. The purpose of this review is to examine the influence of exercise upon a number of established and novel cardiac biomarkers, including markers of necrosis, inflammation, cardiac function and ischemia. We will also address the clinical relevance of such exercise-induced perturbations.