What is it?

When a heart attack is suspected, apart from clinician's bedside review of patient's symptoms, history and mandatory ECG, certain blood tests may also help in clinching the diagnosis. As a result of injury to the heart tissue, certain proteins are released, which can be detected in blood by doing tests. However, one must remember that these proteins are indicators of injury to heart tissue in general, rather than heart attack per say.

These tests are:

1. CREATINE KINASE, AND CREATINE KINASE MB FRACTION rises in blood in response to injury to the heart tissue. The values must be read with caution in following conditions:
   • Skeletal muscle injury (Myopathy)
   • Hypothyroidism
   • Renal failure
   • Combined skeletal muscle and cardiac injury
     
     
2. TROPONINS There are two types of troponin, I and T. False positive elevations of T, but not I, have been observed in patients with renal failure. The level of troponin T parallels the severity of left ventricular dysfunction. Elevated troponin I levels have also been found in patients with cirrhosis, especially when due to alcohol.
   
   
3. LACTATE DEHYDROGENASE (LD) The fraction of LDH sensitive for heart rises indicating injury to heart tissue.
   
   
4. MYOGLOBIN Estimation of myoglobin has been used to ascertain establishment of flow in the coronary arteries since it rises in the blood following flush out by blood. The best criteria appear to be a rate of change over the first hour of more than 2.6 ng/min or a 4.6 fold rise over two hours.
   
   
5. FATTY ACID BINDING PROTEIN as a test specific to injury to heart tissue is being evaluated.