MUSCLE INJURIES Flashcards
Myocardial infarction is diagnosed by the presence of 2 out of 3 features:
a. Chest pain
b. ECG changes
c. Cardiac enzymes
- prolonged
Chest pain
most important condition
heart attack
decreased flow of blood in the heart causing damage to the
heart muscle
major cause of morbidity in the US
Myocardial infarction
Enzymes released from cells
AST, CK & LDH
LDH ()
LD1 > LD2
Enzyme leaks from cells after injury; half-life is about
4 hours
longer during
renal dysfunction
PROTEIN MARKERS
Heme-containing protein that binds O2 with cardiac and skeletal muscle
Myoglobin
Earliest marker in MI
Myoglobin
Reasonable sensitivity but poor specificity for MI dx
Myoglobin
Used in dx but not specific
Myoglobin
Levels are related to muscle mass and activity
Myoglobin
Bind O2 within cardiac and skeletal muscle
Troponin
Govern excitation-contraction coupling
Troponin
Troponin Three subunits:
o Troponin T (cTnT) - tropomyosin-binding unit
o Troponin C (TnC) - calcium-binding subunit
o Troponin I (cTnI) - inhibitory subunit (binds to actin)
o Troponin T (cTnT) -
tropomyosin-binding unit
o Troponin C (TnC) -
calcium-binding subunit
o Troponin I (cTnI) -
inhibitory subunit
(binds to actin)
cTnI
are bound to muscle fibers
cTnT and cTnI
cTnT and cTnI slowly released ((?)after MI)
1-2 weeks
Essentially absent from normal serum
Troponin
Troponin Highly sensitive assay:
0.1 ng/mL
“gold standard” for diagnosis of MI Together w/ CK and LDH
Troponin
Troponin Specimen of choice:
heparinized plasma samples
Troponin False positive results:
Fibrin
Rheumatoid Factor
(incompletely clotted specimen) Adhere to walls of testing kits
Fibrin
Risk factor for CVD
Rheumatoid Factor
Involved in contraction and relaxation on the heart muscle
Troponin
Troponin Location: (responsible for the excitation of the heart)
Actin and Tropomyosin
Direct trauma
physical injury, surgery, strenuous exercise, or IM injection
CK
o Severe disorders caused by adverse effects that
triggers dopamine receptors
Neuroleptic malignant syndrome
CK
Direct trauma (physical injury, surgery, strenuous exercise, or IM injection)
Neuroleptic malignant syndrome
Chronic skeletal muscle damage
Protein marker found in skeletal muscle and NOT found in cardiac muscle
Carbonic Anhydrase – III
Type of muscle injury
RHABDOMYOLYSIS
Caused by:
drugs (ethanol & cocaine), viral infections, extreme
exertion, crush injuries, ischemia of lower extremities and
inflammatory myopathies
Higher total CK w/ myoglobinuria
RHABDOMYOLYSIS
: release of cell contents (K+, PO5, and nucleotides)
“Cell lysis syndrome”
Muscle fiber die causing release of cell contents ito
the blood stream
RHABDOMYOLYSIS
RHABDOMYOLYSIS Complication :
kidney / renal failure
Kidney cannot process the contents of muscle fiber that passes through the glomerulus
RHABDOMYOLYSIS
RHABDOMYOLYSIS TYPES
• Cardiac Muscle Injury (CMI), Skeletal Muscle Injury (SMI), Rhabdomyolysis (RML)
Difficult to distinguish the two
Cardiac Muscle injury existing with Skeletal Muscle
injury
is the diagnostic test of choice for recognition of
cardiac injury
Troponin
↑ Total CK, AST, Myoglobin, Tropomin =
SMI and CMI
↑ Total CK, AST, Myoglobin, Normal Troponin =
SMI
↑ Myoglobin, CA-III =
SMI
↑ Myoglobin and CA - III =
SMI
↑CA-III=
SMI
↑ Tropomin =
SMI
↑ CK, AST, Myoglobinuria =
RML
↑ Myoglobin =
RML