Biomarker to rise earliest in myocardial infarction is:March 2010
**Core Concept**
Myocardial infarction (MI) is a condition where the blood supply to the heart is interrupted, leading to damage of the heart muscle. Biomarkers are substances in the blood that can indicate the presence of MI. The earliest detection of MI is crucial for timely intervention.
**Why the Correct Answer is Right**
The biomarker that rises earliest in myocardial infarction is Troponin I (cTnI). Troponin I is a contractile protein found in cardiac muscle cells. Following myocardial infarction, the damaged cardiac muscle cells release troponin I into the bloodstream, where it can be detected using sensitive immunoassays. This occurs within 2-3 hours after the onset of MI, making troponin I an early and sensitive marker for MI.
**Why Each Wrong Option is Incorrect**
* **Option A:** Creatine kinase (CK) is an enzyme found in various tissues, including the heart, brain, and skeletal muscle. While CK is elevated in MI, it is not the earliest biomarker to rise, as troponin I is more specific to the heart.
* **Option B:** Myoglobin is a protein found in muscle cells that is released into the bloodstream following muscle damage, including MI. However, myoglobin levels may rise earlier than troponin I but are less specific and sensitive for MI.
* **Option D:** Lactate dehydrogenase (LDH) is an enzyme found in many tissues, including the heart. While LDH is elevated in MI, it is not as sensitive or specific as troponin I for early detection of MI.
**Clinical Pearl / High-Yield Fact**
Remember that troponin I is a highly sensitive and specific biomarker for myocardial infarction, and its elevation is a critical diagnostic criterion for MI. Always consider troponin I levels in the context of clinical presentation and other diagnostic tests.
**Correct Answer: C. Troponin I**