:An elevated total CPK (a collective measure of all CPK isoenzymes) is a NONSPECIFIC marker for myocardial infarction. However, an elevation in the level of CPK-MB isoenzyme is a more specific marker for myocardial infarction. The CPK-MM isoenzyme is specific for skeletal muscle. CPK levels begin to rise 4-8 hours following an infarction, usually peak within the first 24-48 hours, and then return to baseline within 3-4 days. A normal CPK level is 35 to 250 IU/L.

:Troponin I is a contractile protein that is increased in serum after myocardial necrosis; it is a sensitive and specific marker of acute MI, and better than CK-MB as a cardiac injury marker Indications Acute, recent, or perioperative MI, cardiac contusion, heart allograft rejection, assessment of side-branch occlusion during coronary revascularization procedures or thrombolysis. Normally troponin I values are less than 10 µg/L but values can rise 5 to 50 times after an acute myocardial infarction.