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Enzymes, Cardiac Markers, Hepatic Tests. clinically useful enzymes: tissue sources preanalytical variables affecting enzyme activities isoenzymes myocardial markers and diagnosis of myocardial injury hepatic function, choice of tests, interpretation of results. Clinically Useful Enzymes.
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Enzymes, Cardiac Markers, Hepatic Tests • clinically useful enzymes: tissue sources • preanalytical variables affecting enzyme activities • isoenzymes • myocardial markers and diagnosis of myocardial injury • hepatic function, choice of tests, interpretation of results
Clinically Useful Enzymes • LDH: heart, liver, muscle, RBC, neural tissue, leukocytes, tumor cells • AST: liver, heart, muscle • ALT: liver • CK: muscle, heart, neural tissue • ALP: liver, bone, intestine, placenta • GGT: liver, pancreas, kidney
Preanalytical Variables • IN THE PATIENT - age, sex, food, exercise, trauma • IN THE SAMPLE • Hemolysis -inc in Total LDH & LDH 1/II • EDTA: inhibition of ALP
CK Isoenzymes • Dimer: M & B monomers • CK- 1: BB; neural & mesenchymal tissue • CK- 2: MB; muscle (<1%); heart (<40%) • CK- 3: MM; heart (60 - 80%) muscle (>99%)
CK Isoforms • CKMM-3 & CKMB-2 (tissue isoforms of CK) after tissue release are converted by carboxypeptidases in blood to:- CKMM-2 & CKMM-1, and- CKMB-1
Detection of Myocardial Injury Major Issues • THE Acute Coronary Syndrome - stable angina - unstable angina - acute myocardial infarction • Choice of biochemical cardiac marker
Acute Coronary Syndrome: Risk Stratification • Chest pain • ECG – ST segment changes • Troponins • Other risk factors: CRP, fibrinogen, BNP
Myocardial Markers • Troponin-I or T • Myoglobin • CK- MB • CK- MB Relative Index • CK Isoforms
Myocardial Markers:References • Donnelly, R, Millar-Craig, MW: Cardiac troponins: IT upgrade for the heart. Lancet 1998;351:537-9 • Apple,FS & Wu,A: Myocardial infarction redefined: role of cardiac troponin testing. Clin Chem 2001; 47:377-8 • Sabatine, MS et al: Multimarker approach to risk stratification in non-ST elevation ACS. Circulation 2002; 105:1760-3