Cardiac troponin I (cTnI) is a regulatory protein related to myocardial contraction. Troponin is a type of protein found in the muscles of your heart. Troponin isn’t normally found in the blood. When heart muscles become damaged, troponin is sent into the bloodstream. As heart damage increases, greater amounts of troponin are released in the blood. Cardiac Troponins are more accurate and sensitive than CKMB and so is therefore the current gold standard for assessing cardiac injury over CKMB.