What is the definition or description of: troponin i?

A blood test: That is typically used to detect heart damage, often caused by a heart attack.

Marker for damage: It is a lab marker drawn at the time of a presumed heart attack. If elevated, it shows the presents of myocardial damage from coronary artery disease, and the patient will need an angiogram. If negative, the chest pain is not cardiac related and the patient will likely be discharged home for an outpatient workup.

Enzyme in heart: Troponin is an enzyme found in heart muscle, which is involved in the muscle fiber's ability to contract. It is extremely specific to heart muscle, and hence if levels are elevated in the blood, it points very confidently toward heart muscle damage as a cause of patient's symptoms. In fact, it is the test that is used to definitively diagnose a heart attack.