Cardiac Biomarkers
Cardiac
Biomarkers
1.
Advantages
Disadvantages
Highly sensitive to myocardial injury
a. Minor injury can still give significant
increase in level
2. Absolute myocardial specificity
3. Can detect late myocardiac
infarction event up to 2 weeks
1.
2.
3.
1.
Low sensitivity to very early stage
myocardial infarction event below than 6
hours of time
a. Should be repeated when produces
negative reading
2. Limited ability to detect late minor
infarction
a. Superimposed by the long standing
increased level of troponin during the 1st
attack
3. Produces false positive in
a. Rheumatoid arthritis
b.
Renal failure
1.
1.
Starts to ↑
1st 3-4 hours after onset of symptoms
2. Peak
a. 12-24hours
3. Duration
a. 10-14 days
Pattern in release in MI is BIPHASIC
1.
Troponin
1. Regulatory proteins in striated muscle
2. Responsible for Ca2+ modulated
contraction
3. Exists in number of isoform
4. Cardiac specific frms immunologically
separable
a. Troponin T (Tpn T)
b.
Troponin I (Tpn I)
1.
a.
Timeline
Description
Creatine Kinase-MB (CKMB)
Cardiac Troponin
4.
Rapid
Cost effective
Accurate assays in detecting
MI within 4-6 hours after onset
of symptoms
Able to detect early even of
reinfarction
Loss of specificity in the even of
a. Severe skeletal muscle disease
b. Skeletal muscle injury including
surgery
i. 5% of muscle are CK-MB
isoform
c. Marathon runners
d. Chronic renal failure
e. Hypothyroidism
2. Loss of sensitivity when MI
happens early than 4 hours after
onset of symptoms
Total Creatine Kinase (Total
CK)
1.
2.
Not reccomended for routine
diagnosis of MI
Provides additional support for
CK-MB test to confirm
myocardial injury event through
CK-MB/Total CK ratio
1.
Poor sensitivity
a. Present in the blood due to
normal tissue turnover
b. Normal reference interval
indicates substantial
interindividual variation
2. Poor specificity
a. Lacks myocardial specificity
b. Wide tissue distribution
c. Loss specificity in the presence
of skeletal muscle
i. Disease
ii. Injury
Starts to ↑
1st 4-6 hours after onset of symptoms
2. Peak
a. 8-12 hours
3. Duration
a. 2-3 days
a.
The best benchmark for biochemical marker to detect myocardial injury in the
past
2. At the moment, the best alternative if cTn is not available
CK Isoenzymes
1. CK-1 (CK-BB)
a. Brain tissues
2. CK-2 (CK-MB)
a. 10-20% in myocardium
b. 5% in skeletal muscle
3. CK-3 (CK-MM)
a. Skeletal muscle
Macro Creatine Kinase
1. Type 1
a. CK-BB + Immunoglobulin
2. Type 2
a.
Mitochondrial CK
Myoglobin
1.
2.
High diagnostic sensitivity
Useful in the very early event
of MI
a. Early than 4 hours after
the onset of symptoms
3. Most useful in ruling out MI
a. ↑negative predictive
value
1.
Loss specificity in the presence
of skeletal muscle
a. Disease
b. Injury
2. Rapid renal clearence
a. Rapidly reduces to normal
level for later presentation
3. Should not be used as the only
diagnostic marker due to
a. Lack of cardiac specificity
b. Rapid renal clearence
i. So that events after 6-12
hours can be detected
confidently
1. Starts to ↑
a. 1st 2-3 hours after onset of
symptoms
2. Peak
a. 6 hours
3. Duration
a. 12-24 hours
1.
Relatively small protein
located at the cytosol of
a. Skeletal muscle cells
b. Myocardium
2. Rapidly being release to
circulation upon tissue
damage
3.
Oxygen binding protein