14) Cardiac function Flashcards
Biochemical feature or facet that can be used to measure the progress of disease or the effects of treatment.
biomarker
Greek for gruel and refers to the massive accumulation of lipids in these vascular lesions.
athero
Was considered to be a bland lipid storage disease
Now thought to evolve from the inflammatory process
Atherosclerotic vascular disease (ASVD)
Acute coronary syndrome (ACS)
Described as a continuum of clinical signs and symptoms ranging from…
unstable angina (chest pain) to…
non-Q-wave (ECG pattern) acute myocardial infarction (AMI) and Q-wave AMI.
most common cause of ASC
atherosclerosis in coronary arteries
Locally acting autacoid polypeptides that mediate vasoconstriction by interacting with phospholipase C-linked receptors.
Released early in the inflammatory response preceding an ACS.
cytokines
Double-walled sac that encloses the heart
pericardium
Made up of cardiac muscle
Anchored to the heart’s fibrous skeleton
myocardium
Connective tissue and squamous cells make up the internal lining of the myocardium
endocardium
Deposition of tough, rigid collagen inside the vessel wall and around the atheroma
arteriosclerosis
Most common form of arteriosclerosis
Caused by the formation of multiple plaques within the coronary arteries
atherosclerosis
Results from the accumulation of atheromatous plaques within the walls of the arteries that supply the myocardium
CAD
cardiac biomarker release affected by…
- Cytosolic enzymes
- Subcellular location
- Molecular mass
- Plasma clearance
- Concentration gradients
Layering or gradation of risk factors, which are described as elements or constituents that may put someone’s health in peril
risk stratification
Many cardiac biomarkers are used for evaluating….
risk stratification
characteristics of ideal cardiac biomarkers
- Smaller markers are released faster from injured tissues.
- Soluble cytoplasmic marker is preferred to structural markers.
- Have absolute cardiac tissue specificity and should not exist in other tissues.
- Useful to differentiate between reversible (ischemic) and irreversible (necrotic) damage.
- Release from the myocardium should be complete following injury.
- Amount of marker released should be in direct proportion to the size of the injury (infarct sizing).
- Remain elevated long enough (12 to 24h) to be detected in the serum of the “late presenter.”
- For risk stratification, there should be a correlation between outcome and the presence or absence of a marker in serum or the degree of elevation of the marker above “normal.”
- Should be cleared rapidly to allow diagnosis of recurrent injury.
- Should be useful for monitoring of reperfusion and re-occlusion.
- Assays should be relatively easy and quick to perform.
Regulatory protein of the myofibril
troponin
3 troponins and their functions
- Troponin I—Binds to actin and inhibits contraction
- Troponin T—Binds tropomyosin
- Troponin C—Contains 4 Ca-binding sites & regulates contraction
Two isoforms of TnI
Several isoforms of TnT
skeletal muscle
One isoform of TnI
Several isoforms of TnT
cardiac muscle
Binds to actin and inhibits muscle contraction
cTnI
Binds tropomyosin
cTnT
Has 3 isoforms, one of which has unique cardiac specificity
cTnI
Isoform can be demonstrated in patients with muscular dystrophy, polymyositis, and end-stage renal disease.
cTnT
(cTnI/cTnT) is NOT expressed in skeletal muscle.
cTnI
what makes troponins good cardiac biomarkers?
- High level of diagnostic specificity and sensitivity.
- Possess early release kinetics after an AMI
- Remain elevated for a long interval of time
- Very low to undetectable concentrations in serum from healthy patients
- Relatively few interfering substances
Drawing blood samples periodically, usually at prescribed time intervals over the course of the patient’s admission
serial sampling
Total CK
rise
peak
return to normal
4-6 hours
24 hours
3-4 days
CK-MB
rise
peak
return to normal
4 hours
18 hours
2 days
Myoglobin
rise
peak
return to normal
1-3 hours ★ (earliest)
8-12 hours
1 day
TnT
rise
peak
return to normal
4-6 hours
10-24 hours
10 days ★ (longest)
TnI
rise
peak
return to normal
4-6 hours
10-24 hours
4 days
sources of error for cTnI
False positive
Heterophile antibodies
Rheumatoid factor
False negative
Bilirubin
Hemoglobin
Circulating cTnI autoantibodies
Interfering factor (IF)
do not affect TnT