Increased circulating troponin I concentration 2018-05-18T20:20:47Z An increased concentration of tropnin I in the blood, which is a cardiac regulatory protein that controls the calcium mediated interaction between actin and myosin. Raised cardiac troponin concentrations are now accepted as the standard biochemical marker for the diagnosis of myocardial infarction. Increased troponin I level in blood Abnormal cardiac biomarker test