Myocardial isonzyme of CK which is specific for myocardial infarction is-
**Core Concept**
Myocardial isoenzymes of creatine kinase (CK) are a group of enzymes that are specific to the heart muscle. These enzymes are released into the bloodstream when the heart muscle is damaged, such as during a myocardial infarction. The most specific myocardial isoenzyme of CK is MM-CK, but another isoenzyme, specifically the MB-isoenzyme, is also highly specific for myocardial infarction.
**Why the Correct Answer is Right**
The MB-isoenzyme of CK is highly specific for myocardial infarction because it is predominantly expressed in the heart muscle. When the heart muscle is damaged, the MB-isoenzyme is released into the bloodstream, making it a useful diagnostic marker for myocardial infarction. The MB-isoenzyme is particularly useful for diagnosing acute myocardial infarction in the early stages, when other biomarkers such as troponins may not yet be elevated.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not specified, but typically, the other isoenzymes of CK (such as BB-CK or MM-CK) are not as specific for myocardial infarction as the MB-isoenzyme. These isoenzymes can be elevated in a variety of conditions, making them less useful as diagnostic markers.
* **Option B:** This option is not specified, but it is likely that another isoenzyme of CK is being referred to. However, this isoenzyme is not as specific for myocardial infarction as the MB-isoenzyme.
**Clinical Pearl / High-Yield Fact**
The MB-isoenzyme of CK is highly specific for myocardial infarction, but it is not as sensitive as troponin for diagnosing acute myocardial infarction. Troponin is a more sensitive marker for myocardial infarction, but the MB-isoenzyme is still useful for diagnosing myocardial infarction in the early stages.
**Correct Answer:** **C**. MB-isoenzyme.