Enzymes and Cardiac Assessment

Question 1

International unit

Answer 1

Amount of enzyme that catalyze the reaction of one umol/min

Question 2

Lactate dehydrogenase (LD) location and ref. range

Answer 2

Found in liver, heart, skeletal muscle, kidney, RBCs

Ref. range = 100-225 IU/mL

Question 3

LD isoenzymes

Answer 3

4 subunits (either M for muscle/liver or H for heart)

LD-1 and LD-2 with MI
LD-3 with pulmonary disorders, pancreatitis, and lymphocytosis
LD-4 and LD-5 with liver and skeletal muscle disorders

Question 4

Creatine kinase (CK) location and ref. range

Answer 4

Found in skeletal muscle, heart muscle, and brain tissue

Ref. range male = 15-160 IU/L
Ref. range female = 15-130 IU/L
CK-MB < 6% of total CK

Question 5

CK isoenzymes

Answer 5

2 subunits (can be M for muscle or B for brain) 
CK-MM is major isoenzymes, CK-MB < 6% of total (increase suggestive of AMI), CK-BB not normally detected

Question 6

Aspartate aminotransferase (AST)

Answer 6

Found in heart, liver, skeletal muscle, less in kidneys and other tissues

Evaluate hepatocellular disorders

Ref. range = 5-30 IU/L

Question 7

Alanine aminotransferase (ALT)

Answer 7

Found in liver with less in other tissues

Evaluated for liver disease

Ref. range = 6-37 IU/L

Question 8

Alkaline phosphatase (ALP)

Answer 8

Found in liver, bone, intestines, spleen, kidney, and placenta

Increased seen in hepatobiliary disease and bone disorders
Decreased seen in hypophosphatasia/insufficient bone calcification

Higher in children and pregnant women
Child ref. range = 54-369 IU/L
Adult ref. range = 50-115 IU/L

Question 9

Acid phosphatase (ACP)

Answer 9

Found in prostate, less in bone, liver, spleen, RBCs, and platelets

Increased in prostate cancer, bone disease, Paget disease, Gaucherie disease, platelet damage, and idiopathic thrombocytopenia purpura

Evaluated for rape cases (found in seminal fluid)

Male ref. range = 2.5-11.7 IU/L
Female ref. range = 0.3-8.2 IU/L

Question 10

Gamma-glutamyltransferase (GGT)

Answer 10

Found in liver, kidneys, pancreas, intestine
Not in skeletal muscle or bone

Increased in hepatobiliary disease and biliary tract obstruction
Induced by drugs and alcohol

Male ref. range < 55 IU/L
Female ref. range < 38 IU/L

Question 11

Amylase

Answer 11

Found in pancreas, saliva, small intestine, Fallopian tubes and other

Increased in acute pancreatitis, mumps, ulcer, intestinal obstruction, cholecystitis, ruptured ectopic pregnancy, mesenteric infarction, and acute appendicitis

Ref. range = 28-100 IU/L

Question 12

Lipase

Answer 12

Found in pancreas, less in gastric/intestinal mucosa and adipose tissue

Increased in acute pancreatitis, ulcer, intestinal obstruction, and cholecystitis

Ref. range < 38 IU/L

Question 13

Cholinesterase

Answer 13

True cholinesterase and pseudo-cholinesterase

True found in RBCs, lungs, spleen, nerve endings, and brain gray matter
Pseudo found in liver, pancreas, heart, brain white matter, and serum

Decreased in hepatocellular disease and insecticide poisoning

Male ref. range = 40-78 IU/L
Female ref. range = 33-76 IU/L

Question 14

Glucose-6-phosphate dehydrogenase (G6PD)

Answer 14

Found in RBCs, adrenals, thymus, lymph nodes, spleen

Decreased in inherited deficiency, drug-induced hemolytic anemia
Increased in megaloblastic anemias and AMI

Ref. range = 8-14 IU/g Hgb

Question 15

Troponin

Answer 15

Found in skeletal and cardiac muscle

cTnI increases in 3-6 hours after MI, peaks 14-20 hours, and normal in 5-10 days

Ref. range < 0.40 ng/mL

Question 16

Myoglobin

Answer 16

Found in skeletal and cardiac muscle

Increased in skeletal muscle injuries, muscular dystrophy, and AMI

Rises sooner than troponin in AMI but not specific to heart so used as negative predictor after chest pains

Male ref. range = 30-90 ng/mL
Female ref. range < 50 ng/mL

Question 17

Beta natriuetic peptide (BNP)

Answer 17

Synthesized/secreted from myocardial ventricles, causes vessel dilation and reduction of fluid load

Increased in CHF

Ref. range < 100 pg/mL

Question 18

High-Sensitivity CRP

Answer 18

Predictor for cardiovascular risk (increased in inflammation, infection, stress, trauma, and AMI)

Male ref. range = 0.3-8.6 mg/L
Female ref. range = 0.2-9.1 mg/L

Low risk < 1.0 mg/L
Average risk = 1-3 mg/L
High risk > 3.0 mg/L

Question 19

Homocysteine

Answer 19

Elevated levels cause damage to arterial walls, precedes plaques
Indicates arterial inflammation

Ref. range = 5-15 umol/L