<prompt> Troponin -T is preferable to CPK- MB in the diagnosis of acute myocardial Infarction MI in all of the following situations except-Bedside diagnosis of MIpostoperatively aftre CABGReinfarction after 4 daysSmall infarcts  <response>: Ref: R Alagappan - Manual of Practical Medicine 4th Edition.pg no:184 Cardiac Enzymes a. CPK-MB: This cardiac isoenzyme stas rising within 4-6 hrs after development of acute MI, peaks during the 2nd day 4 fold rise and disappears in 2-3 days. Other causes of total CK elevation: 1. Skeletal diseases - Polymyositis, Muscle dystrophy, Myopathies 2. Electrical cardioversion 3. Skeletal muscle damage - trauma, convulsions, immobilisation 4. Hypothyroidism 5. Stroke 6. Surgery b. AST: Stas rising on the 1st day, peaks in 2-3 days 3 fold rise and disappears by 3rd day. c. LDH1: Stas rising by second day, peaks around 3- 4 days 3 fold rise and disappears in 10 days. d. Troponin T: Cardiac troponin T is a regulatory contractile protein not normally found in blood. Its detection in the circulation has been shown to be a sensitive and specific marker for myocardial cell damage. Troponin T and I reach a reliable diagnostic level in plasma by 12-16 hrs, maximal activity by 24-32 hrs, returns to normal in 10-12 days. Troponin I : 0-0.4 ngml Troponin T: 0-0.1 ngml Cardiac troponins are detected in the serum by using monoclonal antibodies. These antibodies have negligible cross reactivity to skeletal muscle. Cardiac troponins I and T sta to rise within 3-4 hours after myocardial infarction and remain raised for 4-10 daysOther causes of elevated cardiac troponins: Cardiac causes: Cardiac contusionsurgery Myocarditis Cardiomyopathy Hea failure Cardioversion Percutaneous coronary intervention Cardiac amyloidosis Radiofrequency ablation Supraventricular tachycardia Post-cardiac transplantation Non-cardiac causes: Primary pulmonary hypeension Pulmonary embolism Cerebrovascular stroke High dose chemotherapy Sepsis and septic shock Renal failure Critically ill patients Scorpion envenomation Ultra-endurance exercise marathon e. Myoglobin It is increased within 2 hrs of onset of symptoms and remains increased for at least 7-12 hrs. Normal level is 20-100 mgL. 