Cardiac Lab Values
Cardiac Enzymes
Creatine Kinase or CK: an isoenzyme present in heart muscle, skeletal muscle, brain tissue that catalyses’ conversion of
creatine and uses ATP to create phosphocreatine and ADP important in tissues that consume ATP rapidly
Measured in serum as a marker of damage of CK rich tissue (MI, rhabdomyolysis, acute renal failure…)
Normal
CK 1 or BB
brain, nervous tissue, GI, GU tract
0%
CK 2 or MB
elevation is specific to myocardial
Tissue injury
Rises 4 – 6 hours after symptom onset (acute evaluation)
Peak 18-24 hours (m/b/ several times normal)
Return to baseline within 3 days after MI
10-13 units/L
CK 3 or MM
Constitutes almost all circulatory enzymes in normal people,
skeletal muscle, cardiac muscle
96 – 100%
0 – 4%
Total CK
Men
38 – 174 units/L
Women
96-140 units/L
*African-Americans have higher baseline CK levels than Caucasians or Hispanic persons
Creatinine phosphokinase – CPK
Men
Women
38 – 174 units/L
26 – 140 units/L
Troponin – most sensitive test; myocardial muscle protein released into circulation after injury – normally negative
2 subtypes:
T (cTnT) troponin T – cardiac specific troponin
less than 0.1 ng/mL
Troponin 1 (cTnl) – Troponin I
Detectable w/in 1 – 3 hours after myocardial injury
High specificity at 3 – 6 hours after onset of symptoms
Peak w/in 12 hours
Returns to normal in 14 – 15 days
Monitored for healing and reperfusion
Less than 1.5 ng/mL
Lactic acid dehydrogenase (LDH) : intracellular enzyme widely distributed in kidney, heart, skeletal muscle, brain, liver,
lungs
Elevations reflect cellular death, leakage from cell
Elevated levels may be non-specific but view in relation to other tests
Ex: LDH remains elevated longer than CK after an MI
Test 48-72 hours after onset of symptoms when pt receives medical attention
0 – 5 yo
5 – 12 yo
12 – 14 yo
14 – 16 yo
Adult > 16 yo
425 – 975
370 - 840
370 – 785
370 – 645
313 – 618
ANP , BNP, NT-proBNP used to detect CHF, Left Ventricular (LV) dysfunction
Higher levels found in pts with GFR < 60 mL/min & thin pts, lower in obese pts
Recommended levels be drawn on admission, 24 hrs and at D/C
Predictors of mortality, sudden cardiac death
Also elevated in ARF, HTN, COPD, pneumonia, PE, ARDS, MI, Afib, ACS, valvular disease, myocarditis, cirrhosis
Atrial Naturitic Peptide (ANP) – a potent natriuretic (causes loss of Na thru urine) agent and vasodilator,
- mostly found in atria
- Secreted in response to atrial stretching
– produces diuresis and increases GFR.
- Helps regulate extracellular fluid volume, blood pressure, sodium metabolism, promote Na excretion,
- inhibits renin-angiotensin-aldosterone systems effect on aldosterone secretion.
- Decreases atrial pressure by decreasing venous return, thereby reducing B/P and volume
- Highly elevated in obvious heart failure, CVR disease, and increased cardiac filling pressures
- Marker for early asymptomatic LV dysfunction and increased cardiac volume
Reference value
20 – 77 ng/L
Brain natriuretic peptide (BNP) or NT-proBNP (a pre form of BNP) – most common level but no significant difference
- Found in high concentrations in cardiac tissues, especially the ventricles
- Secreted in response to volume overload
- stimulates diuresis, natriuretic, & vasodilation
- originally found in “pig” brains
- NT-proBNP is excreted in higher levels (3-5 times higher) than BNP and makes diagnosis easier
- Since the level is higher in myocardial tissue is more useful than ANP
- Inhibits the renin-angiotensin-aldosterone system
- Marker of increased LV (left ventricular) filling pressures and LV dysfunction
- Cleared by kidneys so pts with renal insufficiency may have skewed results due to prolonged excretion
Reference values
BNP, pg/mL
< 100 HF unlikely
> 500 HF likely
< 200 HR unlikely
> 500 HF likely
if GFR < 60
NT-proBNP, pg/mL
< 300 HF unlikely
> 450 HF likely
> 900 HF likely
>1800 HF likely
21 – 50 yo
50 – 75 yo
> 75 yo
C-reactive Protein (CRP) – acute phase reactant made by liver and released into blood w/in a few hours after tissue
injury, start of infection, or other inflammation. Not specific but helpful…
Secreted by macrophages and T cells, binds to dead or dying cells and some bacteria, activates
Elevated during inflammatory processes, elevated levels indicate risk for thrombosis
Normal
0.1 to 2.5 mg/L
Heart patients
4 – 10 mg/L
Risk for future CV events screening tool:
Low risk
Average risk
High risk
<0.1 mg/dL
0.1 to 0.3 mg/dL
> 0.3 mg/dL