Enzymes, Cardiac Markers, Hepatic Tests
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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.
Enzymes, Cardiac Markers, Hepatic Tests
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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