Cardiac Markers Flashcards
Phased out Biomarkers
Aspartate Aminotransferase - AST
Alanine Aminotransferase - ALT
Lactic Dehydrogenase - LDH
CK/CPK [Creatine Phosphokinase]
(location and function)
Location : heart, skeletal muscle and brain
Function: catalyze conversion of creatine to phosphocreatine.
Phosphocreatine is an energy revervior for rapid regeneration of ATP.
[2 subunits- B (brain) and M (muscle)
CK-BB
brain and lung isoenzyme
disease correlation: brain injury, CVA, brain CA, subarachnoid hemorrage, seizure, ECT
CK-MB
heart muscle isoenzyme
disease correlation: acute MI, myocarditis, cardiac ischemia, cardiac defribrillation, cardiac sx
CK-MM
heart and skeletal muscle
disease correlation: rhabdomyolysis, muscular dystrophy, myositis, IM injections, crush injuries, strenuous exercise, shock
CK interpretation
Diagnostic criteria:
2 fold total increase with concurrent CK-MB increase
[Early in diagnostic process]
Total CK rises within 4-6 hours
Peaks 18-24 hours
Normal within 2-3 days
CK-MB behavior after and infarc
Rises 4-6 hours after infarc
Peaks 12-20 hours
normal in 24-48 hours
If the patient baseline in unknown there is risk of a false positive.
CK-MB Indications
High specificity for cardiac tissue
**.marker of choice for re-infarction.
Serial determinations in evaluation -
cases where total CK is low or increase due to severe skeletal muscle in jury, use relative index ration CK-MB to total CK.
CK-MB/Total CK * 100
> 2.5 suggestive of MI
CK-MB False positives
Significant skeletal muscle injury
Cardiac injury other than MI
[cardioversion, defibrillation, blunt chest trauma, cardiac and non cardiac sx, cocaine abuse]
Troponin -
defined
Regulatory protein specific to cardiac muscle tissue
Damage to the heart muscle releases troponin into the serum.
Increased window of opportunity for earlier diagnosis and use of thrombolytics.
Troponin subunits
Troponin T - binds myosin/actic complex (tropomyosin complex)
Troponin I - binds Ca to initiate muscle contraction
Troponin C - binds muscle contraction in the absence of Ca ( inhibitory)
Troponin -
Cardiac testing implications
Cardiac marker of choice for ACS.
Cardiospecific, sensitive, and provides prognostic value
Unlike CK levels are virtually undetectable in normal individuals.
How Troponin is used
serial determinations used to monitor incremental rise and confirm acute MI.
Chronic elevation in HF or renal failure but less likely to see incremental rise with serial measurements.
HTN urgency, tachycardias, and trauma can also raise levels.
Troponin Interpretation
Isoforms used Troponin I and Troponin T
Rise in 4-8 hours, remains elevated for 7-14 days
-the rise in trop can be as early as 2-3 hours after MI onset
- 80% of Pts with have positive values at 3 hours
Myoglobin Indications
protein in smooth, cardiac, and skeletal muscle- transports Hb to enzymes in contractile cells
one of 1st protein markers released from ischemic cardiac muscle cells ( before CK)
