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Creatine Kinase or Creatine Phosphokinase

• Creatine kinase (CK) is important for energy utilization. Most circulating CK is from muscle. CK can be measured by one total enzyme or can be separated into 3 isoenzymes The isoenzymes help to detect MI and muscular diseases

Isoenzymes of CK

• CK-I (BB): produced by smooth muscle and brain tissue
  • Less than 1%
• CK-II (MB): produced by heart tissue
  • Less than 3%
• CK-III (MM): produced by muscle tissue
  • 95-100%

Creatine Kinase

• Enzymes will disappear from the bloodstream. CK may disappear in less than 24 hr after a MI.
• Avoid IM injections if possible or total CK will be elevated
• Total CK
  • Women: 40-150 U/L, KU: 21-215 U/L
  • Male: 60-400 U/L, KU: 35-232 U/L

Increased Serum CK

• First enzyme to be elevated after a MI
• Rise in 3-6 hrs and may peak in the first 24 hrs. Can last for 3 days
• Some patients returns to normal within 16 hrs
• If CK elevated then CK-MB taken.
• CK greater than 12 U/L MI probable
• KU CK-MB Mass: 0-5.0 ng/ml (Chemoluminescence)

CK and MI

• Some laboratory report isoenzymes in %. More than 3 -4% is considered evidence of MI. KU: CK-MB > 5%
• First CK on admission, second test within 12 hrs. A third CK may be taken at 24 hrs
• May repeat tests if patient has recurrent chest pain or side effects (CHF, hypotension, dysrhythmias)

Lactic Dehydrogenase

• LDH is an enzyme helps remove H2O from lactic acid.
• Several types of LDH isoenzymes (LDH 1-5)
• Total LDH, LDH1 and LDH2 are used to detect MI. Begins rising at 12-24 hrs in MI. Peak usually at 300-800 U/L is in 2-6 days and enzyme remains in blood stream for 2 weeks.

LDH

• LDH1 and LDH2 can also be elevated in hemolytic and macrocytic anemias
• Liver damage can increase LDH4 and LDH5
• LDH very common marker used for non-Hodgkins lymphoma
• LDH is elevated with pneumocystis carinii pneumonia

Troponins

• Actin and myocin filaments
• Troponin is attached to tropomyocin on actin
• Troponin is a regulatory protein found in muscles in 3 forms (I, T and C)
• Sensitive using assay tests using antibodies have allowed for the measurement of cardiac troponin I (cTnI) and cardiac troponinT (cTnT)
• KU Troponin T: 0 - 0.1 ng/ml

Troponins

• Troponin T test now available at bedside
• Troponin I begins to increase in about 4-6 hrs, peaks in 14-18 hrs and remains elevated for up to 7 days
• Troponin T increase in 3-4 hrs and remains elevated in 10-14 days
• Serial troponin measurements are often taken at 3, 6 and 9 hrs or longer

Myoglobin

• A ferrous globin in striated muscle that makes muscle look “red” and its ability to store O2.
• After a MI myoglobin is the earliest marker of MI but can be elevated by many other factors such as skeletal muscle damage
• May be used to assess for reperfusion injury of myocardium after thrombolytic therapy

Serum Cholesterol

• Essential for the production of bile salts, to manufacture steroid hormones, cell membranes
• Liver esterifies cholesterol by combining it with a fatty acid and most in the bloodstream is esterified.
• Cholesterol levels vary by age, diet, genetic influence, & geographic location

Cholesterol

• Cholesterol greater than 200 mg/dL, pt. considered to have mod-high risk for cardiovascular disease
• Increased cholesterol from many factors but reason still unknown.
• Decreased cholesterol usually due to hyperthyroidism, sever liver damage and malnutrition

Triglycerides

• Most abundant of the lipids and triglycerides if not used store as adipose tissue.
• Triglyceride test used to identify some types of hyperlipidemia and is used to determine LDL
• Increased triglyceride levels
  • pancreatitis, diabetes nephrotic syndrome

Lipoprotein Electrophoresis and Lipid Profiles

• Lipoproteins contain lipids such as cholesterol and triglycerides and other proteins
• Broad classifications were made based on the density of their molecules
  • HDL , LDL, LVDL
• Electrophoresis separates these types with an electric current to cause migration of the molecules

High-Density Lipid Cholesterol (HDL)

• 20% of cholesterol is HDL. Low levels of HDL have been associated with increased incidence of CHD
• Levels below 35 mg/dL are considered at risk for CHD
• Levels above 60 mg/dL are considered a negative risk for CHD

Ratio of Total Cholesterol to HDL

• Total cholesterol divided by HDL is used to predict heart attack risk
• A ratio lower than 4.5 is good so decreased risk
• Total cholesterol of 200 and a HDL of 40 is ratio of 5 which is high risk

Low Density Lipoprotein Cholesterol (LDL)

• Carry cholesterol in the plasma.
• LDL calculation

total cholesterol - (HDL + triglycerides /5)

Example = cholesterol 200, HDL 55, triglycerides = 100

LDL = 200 - (55 + 100/5) = 125

Not valid formula if chylomicrons present or if triglyceride is greater than 400 mg/dL

Homocysteine

• Moderate levels of homocysteine can cause peripheral, cerebrovascular and coronary artery disease.
• Normal fasting is 5 -15 micromoles
• Vitamins (folic acid, B6 and B12) may decrease homocysteine levels

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