IHD Patho 2012_Student Version (1)

Creatine kinase intracellular enzyme found within

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Creatine Kinase Intracellular enzyme found within muscle cells Isoforms = CK-MM, CK-BB, CK-MB Elevated within 2-4 hours Peak = Within 24 hours Return to baseline = 2-3 days Less sensitive and less specific than troponins
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CK-MB Single measurement not adequate to exclude diagnosis of MI Need at least 2 CK-MB values greater than MI decision limit (set by hospital laboratory) to make clinical diagnosis of STE MI or NSTE MI Baseline, 6-12 hr, and 12-24 hr Can also be elevated in patients with skeletal muscle injury or renal dysfunction
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Troponins A protein complex that is part of the actin filaments; responsible for regulating calcium-mediated actin-myosin contraction in striated muscle Troponin T (TnT) and troponin I (TnI) sensitive and specific than CK-MB in detecting minor myocardial necrosis Can be elevated within 2-4 hr – May take up to 8-12 hours Peak = Within 24 hours Return to baseline: – 7 days (TnI) – 10-14 days (TnT) – Cannot be used to detect early reinfarction CK-MB is preferred
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Troponins Also measured serially Baseline, 6-12 hr, and 12-24 hr MI diagnosed if ≥ 1 troponin value greater than MI decision limit (set by hospital laboratory) For NSTE MI, positive troponin is predictive of subsequent mortality Higher the troponin, greater infarction, higher the risk of mortality
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Myoglobin Not cardiac specific Oxygen-carrying protein present in cardiac and skeletal muscle False (+) from skeletal muscle injury, trauma, renal failure Released more rapidly from infarcted myocardium than troponins or CK-MB Highly sensitive, can be detected as early as 1 hr after onset of myocardial necrosis Peak = 4-8 hours Returns to baseline within 24 hr Can be useful if patients present shortly after onset of symptoms Would still measure troponins and CK-MB
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Biomarkers Used in the  Diagnosis of ACS Range of Time to Initial Evaluations (hr) Mean Time to Peak Elevations Time to Return to Normal Range CTnI 3 – 12 24 hr 7 days CTnT 3 – 12 24 hr 10 – 14 days CK-MB 3 – 12 24 hr 2 – 3 days Myoglobin 1 – 4 4 – 8 hr 24 hr
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Copyright ©2007 American College of Cardiology Foundation. Restrictions may apply. Anderson, J. L. et al. J Am Coll Cardiol 2007;50:e1-e157 Timing of Release of Various Biomarkers After Acute Myocardial Infarction
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Further Testing Patients with ACS, ongoing chest pain, (+) ST and/or T-wave changes, with (+) biomarkers or pending results Go straight to cath lab! Coronary angiography
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Coronary Angiography “Gold standard” for diagnosis Used to assess presence and severity of CAD Steps in process Cardiac catheterization Catheter inserted into femoral artery and threaded up into aorta into coronary arteries Coronary angiography Contrast media (dye) is injected into coronary arteries to assess the % blockage in each major artery Significant CAD: 50% stenosis of left main coronary artery 70% stenosis of 1 major epicardial artery segment LAD, LCx, RCA
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Coronary Angiography Cardiac catheterization Coronary angiography
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Creatine Kinase Intracellular enzyme found within muscle...

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