Upload
cameron-foster
View
218
Download
2
Tags:
Embed Size (px)
Citation preview
Cardiac MarkersCardiac Markers1. After the loss of integrity of cardiac myocyte
membranes,
intracellular macromolecules diffuse into the interstitium
lymphatics, and microvasculature.
2. CK, CK isoforms, troponins, and myoglobin
Creatine KinasesCreatine Kinases1. CK is formed by two subunits, B and M, and thus
including
isoforms CK-MB, CK-BB and CK-MM.
2. CK exists in various types of tissue.
3. CK-MB predominates in cardiac muscle.
- up to ~45% of total CK in cardiac muscle
- <1% of total CK in skeletal muscle
Creatine KinasesCreatine Kinases4. Serum CK-MB levels rise within 2~8 hours after AMI.
5. CK-MB values return to normal 2~3 days after the event.
6. Reference range in NTUH (Abbott assay)
CK 38~160 U/l
CK-MB <16 U/l
Creatine KinasesCreatine KinasesA ratio of CK-MB mass: CK activity 2.5
suggests MI.
CK-MB from skeletal muscle produces a plateau pattern.
CK-MB from MI peaks at approximately 12~24 hour.
TroponinsTroponins1. Three subunits including troponin C, I, and T. The
complex
regulates the contraction of striated muscle.
2. TnC binds to calcium ions.
TnI binds to actin and inhibits actin-myosin interaction.
TnT binds to tropomyosin, attaching to thin filament.
3. Cardiac-specific isoforms
Troponin ITroponin I1. Cardiac Troponin I (cTnl) is a cardiac muscle protein
with a
molecular weight of 24 kilo-Daltons.
2. The human cTnl has a additional amino acid residues
on its N-terminal that are not exist on the skeletal form.
3. The half life of cTnI is estimated to be 2~4 hours.
4. Serum increase is found between 2-8 hours and returns to
normal 7~10 days after AMI.
5. Cardiac TnI levels provide useful prognostic information.
6. Reference range in NTUH (Abbott assay)
cTnI <2 ng/ml
Troponin TTroponin T1. Cardiac Troponin T (cTnT) is present in fetal skeletal
muscle.
2. In healthy adult skeletal muscle cTnT is absent.
3. The gene of cTnT may be re-expressed in skeletal muscle
disease. (Clin Chem. 1999;45:2129-2135)
4. Biological half life and early serum increases of cTnT are
similar to that of cTnI.
5. Peak between 12~96 hours and return to normal 14 days
after AMI.
MyoglobinMyoglobin1. The major protein responsible for O2 supply of
striated
muscle.
2. It is released into blood rapidly (as early as 1 hour) after
damage to muscle cell.
3. Early detectable, more sensitive but non-cardiospecific.
4. High negative predictive value.
ComparisonComparison1. CK and CK-MB may be elevated in renal and
muscular
disorders.
2. Elevated cTnI level in uremic patients has been a source
of great controversy.
3. Elevated cTnT has been found in regenerating skeletal
muscle and in patients with ESRD. (cTnT is elevated in asymptomatic patients with CRF. Am J Clin
Pathol
1996;106:118-123)
4. Myoglobin is more suitable for the detection of reinfarction.
Utility After CABG or Vascular Utility After CABG or Vascular SurgerySurgery
1. Early ischemia or infarction after CABG is most likely to be
due to problems with the grafts.
2. Due to the surgical trauma, the usual indicators of MI
have uncertain diagnostic value.
3. It is important to establish new biochemical diagnostic
limits for perioperative MI after CABG.
4. Cardiac markers are released rapidly into blood (washout)
in cases of successful reperfusion after surgery.
5. Elevated cTnI (Dade assay) is associated increased risk of
6-month mortality and MI. (Circulation 2002;106:2366-2371)
ConclusionConclusion
1. Elevated serum cTnI in patients with renal disorders,
especially in lower ranges, should be interpreted with
caution.
2. Cardiac TnI is useful for predicting short-term mortality in
vascular surgery patients.
3. Normal values of cardiac markers after cardiac surgery
are still not defined.