Cardiac Enzymes Flashcards
natriuretic peptides
inhibit reabsorption of sodium in renal tubule (so sodium excretion in urine increases)
3 major natriuretic peptides
ANP (synthesized in atrial cardiomyocytes), BNP (identified in brain, released from ventricles of heart), c-type (CNP; found in nervous system and endothelium)
function of BNP
released when atria and ventricles stretch; cause vasorelaxation, increase amt of sodium and water excreted; released during CHF and MI
CHF
occurs when heart is not able to perfuse all tissues sufficiently; frequently results in cardiomegaly, dyspnea, fatigue, peripheral edema
BNP test
used to dx CHF. normal less than 100 pg/mL. increased (>500) = probable CHF
creatine kinase
is metabolized to phosphocreatine to generate ATP. found primarily in cardiac, skeletal muscle, and brain (high-energy tissue)
creatine kinase exists as 3 different isoenzymes
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)
CK (total) - test
elevated in disorders/injury to muscle (typically) or neuro disease. multiple factors influence levels. normal: 50-200 U/L
CK increased in:
strenuous exercise, recent surgery, rhabdomyolosis, myositis, recent convulsions, trauma/crush inj., neuromuscular disorders
CK-MB
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
increased CK-MB in:
acute MI, cardiac defibrillation, myocarditis, ventricular arrhythmias, cardiac ischemia
troponins
proteins that control interaction of actin and myosin in skeletal and cardiac muscle; interact w/ calcium ions and tropomyosin during muscle contraction
3 subtypes of troponin
troponin I (inhibits interaction of actin and myosin), T (binds troponin and tropomyosin), and C (contains the calcium binding site)
troponin subtypes used to dx MI
troponin I and T
troponin released in:
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.
troponin test
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
trop I used more commonly than T b/c:
renal failure more frequently increases cardiac troponin T
troponin elevated in:
cardiac injury typically. unstable angina, MI, CHF, myocarditis, severe PE, CPR, cardioversion, pacemaker findings, cath/stent
myoglobin
short-term O2 storage in skeletal and cardiac muscle; released when there is skeletal or cardiac injury. increased 3 hrs after cardiac injury
myoglobin elevated in:
MI, myositis, skeletal muscle injury, sz, muscular dystrophy, recent cocaine use, trauma or inflammation
lactate dehydrogenase (LDH)
an enzyme that catalyzes the conversion of lactate to pyruvate. involved in energy production in cells. released when tissue injury occurs. nonspecific
most abundant LDH isoenzyme typically
LDH-2 (5 total)
most abundant LDH isoenzyme in myocardial injury
LDH-1 (w/ some increase in LDH-2) “flipped LDH”
d-dimer
formed during lysis of cross-linked fibrin through the action of plasmin. indicative of intravascular clotting.
d-dimer test
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
d-dimer elevated in:
DVT, PE, disseminated intravascular coagulation (DIC), sickle cell, surgery, pregnancy, elderly pts
c-reactive protein
acute phase reactant. pro- and anti-inflammatory actions in body. produced in liver. nonspecific.
c-reactive protein - high sensitivity (CRP-HS)
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
CRP-HS elevated in:
DM, HTN, depression, obesity, low physical activity, smoking, aging, others
CRP-HS indications
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
lipid panel includes:
total cholesterol, triglycerides, HDL (high-density lipoprotein), LDL (low-density lipoprotein)
cholesterol
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)
routine lipid panel screening
men >35, at risk men 20-35, women >45, at risk women 20-45; diabetics annually
total cholesterol
normal less than 200 mg/dL; includes LDL+HDL+VLDL; alone is not a good indicator of risk d/t high variability
triglycerides
produced in liver, form of fat composed of chain of fatty acids and glycerol; energy source
triglyceride test
normal less than 150 mg/dL; high 200-499, very high >500
triglycerides are increased by:
familial hypertiglyceridemia, hyperlipidemia, hypothyroidism, high carb diet, poorly controlled diabetes, chronic renal failure
triglycerides decreased in
malabsorption/malnutrition, hyperthyroidism
high-density lipoprotein (HDL)
“good cholesterol” - transports cholesterol from tissues of body and vascular endothelium, returning it to liver (less in tissue); provides protective effect against CHD
HDL test
men >40mg/dL acceptable, >60 desired, less than 40 at risk. women >50 acceptable, >60 desired, less than 50 at risk
HDL increased in
familial HDL lipoproteinemia, exercise, moderate alcohol use, healthier eating choices, estrogen administration
HDL decreased in
tobacco use, metabolic syndrome, genetically low HDL, hepatic disease
low-density lopoprotein (LDL)
“bad cholesterol:” - cholesterol deposited into walls of arteries, a/w increased risk of atherosclerosis and CHD
LDL =
= total cholesterol - (HDL+TG/5); only valid is TG less than 400 mg/dL
LDL test
70-100 mg/dL ideal for at risk for heart disease; 100-130 near ideal. 130-159 borderline. >160 high
LDL increased in
familial LDL lipoproteinemia, hypothyroidism, excessive alcohol consumption, chronic liver disease
LDL decreased in
familial hypolipoproteinemia, hyperthyroidism, exercise, low fat diet
LDL particle testing
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)
