Cardiac profile test

Cardiac profile test The heart is a muscular organ responsible for pumping blood through the blood vessels by repeated, rhythmic contraction.

Role of laboratory: Note: Assess cardiac disease such as AMI Offer body chemistry information to aid supportive cardiac therapy Note: Single diagnostic laboratory test that assess cardiac function does not exist

Cardiac marker: Enzyme markers Aspartate transaminase (AST; SGOT) Lactate dehydrogenase Five isoenzymes, composed of combinations of H (heart) and M (muscle) subunits Creatine kinase Three isoenzymes, composed of combinations of M (muscle) and B (brain) subunits

Lactate dehydrogenase (LD) Pyrvate + NADH Lactate + NAD LD activity is measured by monitoring absorbance at  = 340 nm (NADH) Methods can be P  L or L  P But. . .reference range is different Total LD activity has poor specificity

Tissue specificity of LD isoenzymes

5 isoenzymes composed of a cardiac (H) and muscle ( M ) component LDH - 1 ( HHHH ) LDH - 2 ( HHHM ) LDH - 3 ( HHMM ) LDH - 4 ( HMMM ) LDH - 5 ( MMMM ) LD-1 is the fastest towards the anode

Diagnostic Significance In healthy individuals LD-2 is in highest quantity than LD-1, LD-3, LD-4 and LD-5 Heart problems: 2-10 X (Upper Limit of Normal) ULN in acute MI If problem is not MI, both LD1 and LD2 rise, with LD2 being greater than LD1 If problem is MI, LD1 is greater than LD2. This is known as a flipped pattern

Assay for Enzyme activity The reaction can proceed in either a forward or reverse direction Pyruvate + NADH+ Lactate + NAD + H+ The optimal pH: for the forward reaction is 8.3 – 8.9 For the reverse reaction 7.1 – 7.4 Reference Range : 100-225 IU/L (37°C) LD

Creatine Kinase (CK) Action – This enzyme is associated with the regeneration and storage of high energy phosphate (ATP). It catalyzes the following reversible reaction in the body.

Tissue specificities of CK isoenzymes

Diagnostic Significance The value of CK isoenzyme separation can be found principally in detection of myocardial damage. Cardiac tissue contains significant quantities of CK-MB, approximately 20% of all CK-MB. increased CK – MB ( > 6% of the total CK activity ) is a strong indication of AMI Post AMI CK-MB CK-MB increases 4 – 8 hours post AMI Peaks at 12 - 24 hours post AMI Returns to normal 48 - 72 hours

CK Assay Reference Range for Total CK: Male, 15-160 U/L (37°C) Female, 15-130 U/L (37°C) CK-MB: <6% total CK

CK isoenzymes For CK isoenzymes, electrophoresis is the reference method. Calculation of relative index (CK- MB mass assay*100 / total CK ) may be used as indicator of MI relative index allows the distinction between increased total CK due to myocardial damage and that due to skeletal or neural damage A relative index exceeding 3 is indicative of AMI

CK – MB Assay A specific antibody inhibits both M subunits of CK-MM(CK-3), and the single M subunit of CK-MB(CK-2) and thus allow determination of the B subunit of CK-MB (assuming the absence of CK-BB (CK-1)). CK-B catalytic concentration, which corresponds to half of CK-MB concentration, is determined from the rate of NADPH formation, measured at 340 nm .

CK-MB procedure Bring the WR and the instrument to 37 Pipette into labeled test tube mix thoroughly and incubate immediately at 37. start stop watch Read the absorbance at 340 nm after exactly 5 min and 10 min of incubation 40 u Sample 1 ml WR

Calculation: The CK-MB concentration in the sample is calculated using the following formula: (A10 – A5)*((Vt*10Λ6)/(з*l*Vs*5min))*2=u/l The molar absorbance(з) of NADPH at 340nm is 6300 The light bath is 1 cm The total reaction volume (Vt) is 1.04 ml The samplevolume (Vs) is 0.04 ml CK-MB CONC. = (A10 –A5)*1651=U/L

Reference value The discrimination value for myocardial infarction is around 25 U/L. however, an index higher than 6%the total CK conc. Discriminate better

Cardiac proteins Myoglobin O2-binding cytosolic protein found in all muscle tissue (functional and structural analog of hemoglobin) Low molecular weight (17,800 daltons) Elevations detected within 1-4 hours after symptoms; returns to normal after 12 hours Nonspecific but sensitive marker--primarily used for negative predictive value Usually measured by sandwich, nephelometric, turbidimetric, or fluorescence immunoassay Myoglobin should not be used for early diagnosis of AMI patients with renal disease because of its decreased clearance

Troponin The preferred biomarker for assessment of myocardial necrosis Complex of 3 proteins that bind to filaments of striated muscle ( cardiac and skeletal) Troponin T (TnT) Troponin I (TnI) Troponin C (TnC) The major function of troponins is to bind Calcium and Regulate muscle contraction

Tissue specificity of Troponin subunits Troponin C is the same in all muscle tissue Troponins I and T have cardiac-specific forms, cTnI and cTnT Circulating concentrations of cTnI and cTnT are very low cTnI and cTnT remain elevated for several days Hence, Troponins would seem to have the specificity of CK-MB (or better), and the long-term sensitivity of LD-1

TnT It allows for both early and late diagnosis of AMI Serum concentration begins to rise within 4-10hr of chest pain onset and peak by day 2, it remains elevated beyond 7days before returning to reference values. Unlike CK-MB, the serum troponins are not found in the serum of healthy individuals

TnI Serum concentration begins to rise within 4-6hr of chest pain onset and peak at 12-18hr, it remains elevated beyond 6days before returning to reference values. TnT tends to remain elevated longer and maintain higher sensitivity after day 7 after infarct than TnI

Markers of Inflammation and coagulation disorder Inflammation plays a role in atherosclerotic plaque formation, and acute coronary syndrome. Several studies have identified such biomarkers of inflammation over recent years including high-sensitivity C- reactive protein (hsCRP)

hsCRP CRP is an acute-phase reactant produced primarily by liver. It increased rapidly with inflammation. It rises response to injury, infection, or other inflammatory conditions, it is nonspecific CRP may considered as a risk factor marker for cardiovascular disease.

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