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Biochemical Investigations In Heart Disaeses

Biochemical Investigations In Heart Disaeses. Overview. Myocardial infarction Time-course of plasma enzyme changes Creatine kinase (CK) Lactate dehydrogenase (LDH) Aspartate aminotransferase (AST) Myoglobin Cardiac troponins I and T. Similar pathophysiology

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Biochemical Investigations In Heart Disaeses

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  1. Biochemical Investigations In Heart Disaeses

  2. Overview • Myocardial infarction • Time-course of plasma enzyme changes • Creatinekinase (CK) • Lactate dehydrogenase (LDH) • Aspartateaminotransferase (AST) • Myoglobin • Cardiac troponins I and T

  3. Similar pathophysiology Similar presentation and early management rules STEMI requires evaluation for acute reperfusion intervention Unstable Angina Non-ST-Segment Elevation MI (NSTEMI) ST-Segment Elevation MI (STEMI) Acute Coronary Syndromes The increased levels of troponins although not associated by ECG changes indicates increased risk of subsequent cardiac events

  4. What isMyocardial Infarction? • Myocardial ischemia results from the reduction of coronary blood flow to an extent that leads to insufficiency of oxygen supply to myocardial tissue • When this ischemia is prolonged & irreversible, myocardial cell death & necrosis occurs ---this is defined as: myocardial infarction is the death & necrosis of myocardial cells as a result of coronary prolonged & irreversible ischemia

  5. Previously: • WHO criteria for the diagnosis of myocardial infarction ( at least 2/3): • Typical history of chest pain • Presence of ECG changes • Rise of biochemical markers With the advent of troponins, which is more sensitive biochemical marker, new definition:

  6. Types ofBiochemical Markers 1- Cardiac Enzymes (isoenzymes): Total CK CK-MB activity CK-MB mass Aspartate aminotransferase (AST) Lactate dehydrogenase (LDH) 2- Cardiac proteins: Myoglobin Troponins

  7. Cardiac Enzymes • Total CK (sum of CK-MM, CK-MB & CK-BB) non specific to cardiac tissue (available in skeletal ms.) • CK-MB (CK-2) activity more specific than total CK BUT: less specific than troponin I (available in sk. Ms) appears in blood: within 4-6 hours of onset of attack peak: 12 - 24 hours returns to normal: within 2 - 3 days (no long stay in blood) Advantages: - useful for early diagnosis of MI - useful for diagnosis reinfarction Disadvantages: not used for delayed admission (more than 2 days) not 100% specific (elevated in sk.ms damage)

  8. Cardiac Proteins • Myoglobin cytosolic protein - not specific for cardiac tissue (also in sk.ms. & renal tissue) - appears in blood EARLIER than other markers (within 1-4 hours) So, with high sensitivity - BUT: Returns to normal in 24 hours So, not for delayed admission cases (after one day of onset of attack)

  9. Cardiac Troponins Protein complex located on the thin filament of striated muscles consists of 3 subunits: cTn T, cTnI & cTn C with different structures & functions cTnI & cTnT are used are biomarkers for MI diagnosis Cardiac troponins (cTn) are different from skeletal muscle tropnins So, more specific for MI diagnosis cTnI: • 100 % cardiac specific • With greater sensitivity for diagnosing minor damage of MI • Appears in blood within 6 hours after onset of infarction • peak: around 24 hours • Disappears from blood after about one week (stays longer) So, useful for diagnosis of delayed admission cases • Prognostic marker (relation between level in blood & extent of cardiac damage)

  10. Lactate dehydrogenase (LDH) • LDH is a tetramer, each chain may be one of two types (H,M) where LDH1 is (H4) while LD5 is (M4) • LD1 & LD2 predominates in heart and red cells • LDH increases later than CK-Mb and Ck • Reaches a max. level in 48 h • Remains elevated for 5-6 days after the MI • A non-specific marker of tissue injury: • * High levels are found in liver, lung, • kidney and other diseases

  11. Aspartateaminotransferase (AST) • AST is somewhat heart-specific than ALT • A non-specific marker of MI • It appears in liver and other diseases

  12. Time-course of enzyme changes • Plasma enzymes follow a pattern of activities after a MI • The initial lag phase lasts for about 3 hours • Enzymes rise rapidly to peak levels in 18-36 hours • The levels return to normal based on enzyme half-life • Rapid rise and fall indicates diagnostic value.

  13. Blood samples collected at: * Baseline (upon admission) * Between 12 to 24 hours after the onset of symptoms

  14. Time-Course of Changes

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