MI Flashcards
what is chronic stable angina?
fixed stenosis
demand led ischaemia
predictable
safe
what to do in chronic stable angina?
stop
sit
spray
what is an acute coronary syndrome?
any acute presentation of coronary artery disease
only a provisional diagnosis that covers a spectrum of conditions
describe acute coronary syndrome
unstable angina dynamic stenosis supply led ischaemia unpredictable dangerous
what are the factors affecting plaque rupture?
lipid content of plaque
thickness of fibrous cap
sudden changes in intraluminal pressure or tone
bending and twisting of an artery during each heart contraction
plaque shape
mechanical injury
describe initiation of platelet cascade
vascular damage - percutaneous coronary interventions exposed tissue elements - subendothelial collagen - von willebrand factor
describe adhesion during platelet cascade
platelet recruitment and adhesion at the site of injury forming a monolayer
describe the release of activators during platelet cascade
ADP and other activators are released through degranulation
thromboxane A2 is generated via cycloxygenase
what are the surface receptors during platelet cascade?
ADP receptors
describe the amplification of platelet activation
platelet activation accelerates resulting in platelet aggregation
what does the activation of the platelet cascade trigger?
an inflammatory cascade as activated platelets express adhesion receptors for leukocytes
what is the pathway to platelet aggregation?
activator release aggregation inflammation vascular blockage acute MI, stroke or death
what is the history of someone with an MI?
severe crushing central chest pain
radiating to jaw and arms, especially the left
similar to angina but more severe, prolonged and not relieved by GTN
associated with sweating, nausea and often vomiting
what are the ECG changes in STEMI?
ST elevation
T wave inversion
Q waves
how to differentiate a STEMI?
> 1mm ST elevation in 2 adjacent limb leads
2mm ST elevation in at least 2 contiguous precordial leads
new onset bundle branch block
what are the evolving ECG changes of a STEMI?
ST elevation- first few hours
Q wave formation and T wave inversion- first day
Old MI- Q waves and sometimes inverted T waves
where to spot an inferior MI on an ECG?
II, III, AVF
where to spot an anterior MI on an ECG?
V1-V6
where to spot an anteroseptal MI on an ECG?
V1-V4
where to spot an anterolateral MI on an ECG?
I, AVL, V1-V6
what else can be used in the diagnosis of an MI?
cardiac enzymes and protein markers but they may be normal at presentation
what is the enzyme that can be used in the diagnosis of an MI?
creatinine kinase
peaks in 24 hours
what is the protein marker that can be used in the diagnosis of an MI?
troponin
highly specific for cardiac muscle damage
can detect tiny amounts of myocardial necrosis
how do you treat a STEMI?
early analgesis- diamorphine IV anti-emetic- IV aspirin and clopidogrel GTN if BP >90 oxygen if hypoxic primary angioplasty thrombolysis if angioplasty not available within 90 mins
what are the indications for repurfusion therapy?
chest pain suggestive of acute myocardial infarction
ECG changes
no contraindications
what is repurfusion therapy?
thrombolysis or PCI
what is chest pain suggestive of acute myocardial infarction?
more than 20 mins
less than 12 hours
what are the risks of thrombolytic therapy?
failure to re-perfuse
haemorrhage
hypersensitivity
what are the complications of an MI?
death
arrythmic complications
structural complications
functional complications
what is the usual arrythmic complication of an MI?
ventricular fibrillation
what are the structural complications of an MI?
cardiac rupture ventricular septal defect mitral valve regurgitation left ventricular aneurysm formation mural thrombus with or without systemic emboli inflammation acute pericarditis dressler's syndrome
what are the functional complications of an MI?
acute ventricular failure
chronic cardiac failure
cardiogenic shock
what system is used to classify in-hospital mortality?
killip classification
what is I?
no signs of heart failure
6%
what is II?
crepitations < 50% of lung fields
17%
what is III?
crepitations > 50% of lung fields
38%
what is IV?
cardiogenic shock
81%
what are the ECG changes in an NSTEMI?
may be normal
what can be used to diagnose an MI?
troponins
what are the typical features of an NSTEMI?
less chest pain
minor ECG changes
tach/low BP/ illness
smaller more static trop
what are the typical features of an NSTEMI?
less chest pain
minor ECG changes
tach/low BP/ illness
smaller more static trop
