Cardiac Enzymes

Question 1

natriuretic peptides

Answer 1

inhibit reabsorption of sodium in renal tubule (so sodium excretion in urine increases)

Question 2

3 major natriuretic peptides

Answer 2

ANP (synthesized in atrial cardiomyocytes), BNP (identified in brain, released from ventricles of heart), c-type (CNP; found in nervous system and endothelium)

Question 3

function of BNP

Answer 3

released when atria and ventricles stretch; cause vasorelaxation, increase amt of sodium and water excreted; released during CHF and MI

Question 4

CHF

Answer 4

occurs when heart is not able to perfuse all tissues sufficiently; frequently results in cardiomegaly, dyspnea, fatigue, peripheral edema

Question 5

BNP test

Answer 5

used to dx CHF. normal less than 100 pg/mL. increased (>500) = probable CHF

Question 6

creatine kinase

Answer 6

is metabolized to phosphocreatine to generate ATP. found primarily in cardiac, skeletal muscle, and brain (high-energy tissue)

Question 7

creatine kinase exists as 3 different isoenzymes

Answer 7

CK-MM (predominately skeletal muscle, most of body’s total CK), CK-BB (predominantly in brain), CK-MB (predominantly found in heart, specific for cardiac cells, but can also exist in skeletal muscles)

Question 8

CK (total) - test

Answer 8

elevated in disorders/injury to muscle (typically) or neuro disease. multiple factors influence levels. normal: 50-200 U/L

Question 9

CK increased in:

Answer 9

strenuous exercise, recent surgery, rhabdomyolosis, myositis, recent convulsions, trauma/crush inj., neuromuscular disorders

Question 10

CK-MB

Answer 10

injury to myocardium. rises 3-6 hrs after MI. not elevated in all pts. can be elevated in pt w/ underlying muscle disorder/injury. normal 0-3 mcg/L. NOT preferred test to dx MI

Question 11

increased CK-MB in:

Answer 11

acute MI, cardiac defibrillation, myocarditis, ventricular arrhythmias, cardiac ischemia

Question 12

troponins

Answer 12

proteins that control interaction of actin and myosin in skeletal and cardiac muscle; interact w/ calcium ions and tropomyosin during muscle contraction

Question 13

3 subtypes of troponin

Answer 13

troponin I (inhibits interaction of actin and myosin), T (binds troponin and tropomyosin), and C (contains the calcium binding site)

Question 14

troponin subtypes used to dx MI

Answer 14

troponin I and T

Question 15

troponin released in:

Answer 15

myocardial injury. rises w/in 2-3 hrs onset, remains elevated 7-14 days after. can be elevated d/t cath/stent, card procedure, etc.

Question 16

troponin test

Answer 16

used to dx MI. gold standard. more specific and sensitive than CK-MB. cardiac troponin rises faster, stays around longer. normal trop I less than 0.03 ng/mL. normal trop T less than 0.1 ng/mL

Question 17

trop I used more commonly than T b/c:

Answer 17

renal failure more frequently increases cardiac troponin T

Question 18

troponin elevated in:

Answer 18

cardiac injury typically. unstable angina, MI, CHF, myocarditis, severe PE, CPR, cardioversion, pacemaker findings, cath/stent

Question 19

myoglobin

Answer 19

short-term O2 storage in skeletal and cardiac muscle; released when there is skeletal or cardiac injury. increased 3 hrs after cardiac injury

Question 20

myoglobin elevated in:

Answer 20

MI, myositis, skeletal muscle injury, sz, muscular dystrophy, recent cocaine use, trauma or inflammation

Question 21

lactate dehydrogenase (LDH)

Answer 21

an enzyme that catalyzes the conversion of lactate to pyruvate. involved in energy production in cells. released when tissue injury occurs. nonspecific

Question 22

most abundant LDH isoenzyme typically

Answer 22

LDH-2 (5 total)

Question 23

most abundant LDH isoenzyme in myocardial injury

Answer 23

LDH-1 (w/ some increase in LDH-2) “flipped LDH”

Question 24

d-dimer

Answer 24

formed during lysis of cross-linked fibrin through the action of plasmin. indicative of intravascular clotting.

Question 25

d-dimer test

Answer 25

primarily used to dx DVT or PE. normal less than 0.4 mcg/mL. highly specific for amt of fibrin degradation products present in blood; sensitive but LACKS SPECIFICITY - better negative predictive value than positive. can be used to monitor efficacy and duration of thrombolytic therapy

Question 26

d-dimer elevated in:

Answer 26

DVT, PE, disseminated intravascular coagulation (DIC), sickle cell, surgery, pregnancy, elderly pts

Question 27

c-reactive protein

Answer 27

acute phase reactant. pro- and anti-inflammatory actions in body. produced in liver. nonspecific.

Question 28

c-reactive protein - high sensitivity (CRP-HS)

Answer 28

highly sensitive but nonspecific. normal: less than 1.0 mg/dL. low cardiac risk less than 1 mg/L; avg cardiac risk 1-3 mg/:; high card risk >3 mg/L

Question 29

CRP-HS elevated in:

Answer 29

DM, HTN, depression, obesity, low physical activity, smoking, aging, others

Question 30

CRP-HS indications

Answer 30

can be used to monitor pts with MI, monitor pts for future cardiovascular events (inflammation a/w atherosclerosis), monitoring post-op complications, etc. not used routinely in asymptomatic pts

Question 31

lipid panel includes:

Answer 31

total cholesterol, triglycerides, HDL (high-density lipoprotein), LDL (low-density lipoprotein)

Question 32

cholesterol

Answer 32

aids in production of steroids, sex hormones, bile acids, and cellular membranes. metabolized in liver and carried on lipoproteins to circulation (75% by LDL, 25% by HDL)

Question 33

routine lipid panel screening

Answer 33

men >35, at risk men 20-35, women >45, at risk women 20-45; diabetics annually

Question 34

total cholesterol

Answer 34

normal less than 200 mg/dL; includes LDL+HDL+VLDL; alone is not a good indicator of risk d/t high variability

Question 35

triglycerides

Answer 35

produced in liver, form of fat composed of chain of fatty acids and glycerol; energy source

Question 36

triglyceride test

Answer 36

normal less than 150 mg/dL; high 200-499, very high >500

Question 37

triglycerides are increased by:

Answer 37

familial hypertiglyceridemia, hyperlipidemia, hypothyroidism, high carb diet, poorly controlled diabetes, chronic renal failure

Question 38

triglycerides decreased in

Answer 38

malabsorption/malnutrition, hyperthyroidism

Question 39

high-density lipoprotein (HDL)

Answer 39

“good cholesterol” - transports cholesterol from tissues of body and vascular endothelium, returning it to liver (less in tissue); provides protective effect against CHD

Question 40

HDL test

Answer 40

men >40mg/dL acceptable, >60 desired, less than 40 at risk. women >50 acceptable, >60 desired, less than 50 at risk

Question 41

HDL increased in

Answer 41

familial HDL lipoproteinemia, exercise, moderate alcohol use, healthier eating choices, estrogen administration

Question 42

HDL decreased in

Answer 42

tobacco use, metabolic syndrome, genetically low HDL, hepatic disease

Question 43

low-density lopoprotein (LDL)

Answer 43

“bad cholesterol:” - cholesterol deposited into walls of arteries, a/w increased risk of atherosclerosis and CHD

Question 44

LDL =

Answer 44

= total cholesterol - (HDL+TG/5); only valid is TG less than 400 mg/dL

Question 45

LDL test

Answer 45

70-100 mg/dL ideal for at risk for heart disease; 100-130 near ideal. 130-159 borderline. >160 high

Question 46

LDL increased in

Answer 46

familial LDL lipoproteinemia, hypothyroidism, excessive alcohol consumption, chronic liver disease

Question 47

LDL decreased in

Answer 47

familial hypolipoproteinemia, hyperthyroidism, exercise, low fat diet

Question 48

LDL particle testing

Answer 48

gel electrophoresis. Pattern A (large particle size), pattern B (small, dense, higher ability to enter walls of blood vessel, increased risk of CHD), Pattern I (intermediate)