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 ( %) 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

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