C - Enzymes & Cardiac Biomarkers Flashcards
define enzyme
substance (usually a protein that increases the rate of a chemical reaction without itself being changed in the process
what is Km (michaelis menten constant)
substrate concentration at which reaction velocity is 50% of maximum
what does having a high Km mean
weak binding
what does having a low Km mean
strong binding
when are intracellular enzymes released
- give examples of this
tissue / cellular injury
- infection, immune mediated, inflam, MI, inherited, trauma, toxins, tumour
where is ALP found
bone
biliary system
tumour marker - testicular etc
placenta
intestine
what does a lack of ALP cause
osteomalacia
when is ALP found in trimester
last trimester
when is ALP release from bone physiological
childhood as bones grow
raised ALP. Dx?
LFTs - gamma GGT or ALT
vitamin D
why check vit D with raised ALP
low vit D can cause raised ALP
why is ALP high in kids
bone growth releases ALP
where is ALT predominantly found
liver
where is AST predominantly found
heart, liver, muscle, kidney
why is AST not used for heart / kidney / muscle then but is used for liver?
heart - use trop
kidney - use creatinine or eGFR
muscle - use CK
liver - only AST and ALT are really useful
common causes of high ALT
hepatic - toxins, hepatitis, NAFLD, cancer, ischaemia
kidney issues
pancreatitis
MI
best biomarker for pancreatitis
amylase
when can you get hepatic ischaemia
post MI
upper limit of ALT
45
what happens to ALP when you fast
drops down low
where is gamma GGT released from
hepatobiliary system
pancreas
kidney
is GGT useful at distinguishing between hepatic and biliary issues?
no - high in both
what marker is useful in distinguishing between hepatic and biliary issues
ALT:ALP ratio
when is high GGT released due to high levels intracellularly that get released during normal cell turnover
alcoholics
what drugs induce enzymes to create high levels of GGT
rifampacin, phenytoin, phenobarbitone
where is LDH found
WBCs
RBCs
placenta
skeletal muscle
liver
cardiac
what diseases is LDH raised in
WBCs - lymphoma
RBCs - haemolysis
placenta - germ cell testicular Ca
skeletal muscle - myositis
hepatic disease
cardiac disease
where in a tissue is LDH found
intracellular
how is LDH used in lyphoma care
initially - high LDH = poor prognosis
subsequent - monitor treatment effectiveness
where is amylase produced
pancreas
salivary gland
what type of raised amylase is benign
macro amylase (large so not cleared by kidneys)
number 1 pathology with high amylase
pancreatitis
does high amylase = bad pancreatitis ?
no
what organs make CK
skeletal muscle
cardiac muscle
causes of raised CK
rhabdmyolysis
myositis / polymyositis / dermatomyositis
severe exercise
myopathy eg DMD
cardiac injury
what is the problem with high CK
can cause acute tubular necrosis and AKI
when is slightly high CK physiological
Afro Carribean
where is tropinin I found
cardiac and skeletal myocytes
causes of elevated troponin I
ACS
myocarditis
cardiomyopathy
aortic dissection
PE
infection
anaemia
what factors affect troponin result
age
gender
AKI / CKD
number of myocytes injured
time of test
when is troponin I raised after STEMI
rises within 2 hours, peaks at 12 hours, decreases steadily over 1 week
how is troponin practically used in ED
repeat troponin after 1-3 hours to check its increasing / decreasing by 50% (indicates ACS)
how is pathology of NSTEMI and STEMI different
NSTEMI is not full thickness ischaemia / occlusion, but STEMI is
how does Ix results of unstable angina differ from STEMI
abnormal ECG + normal troponin (unstable angina)
abnormal ECG + troponin (STEMI)
what chest pain is seen in stable angina
exertional cardiac chest pain
can 2 negative troponins and a normal ECG rule out ACS?
yes
why is BNP released
cardiac overload
cardiac myocytes stretch
what does BNP causes
increased urination to offload the fluid
why is BNP hard to measure in blood
short half life
what is measured in blood instead of BNP and why is that okay
NT-proBNP (produced from the same molecule as BNP so made in the same quantity, but is not active so doesn’t degrade)
