myocardial infarction Flashcards
what 3 things does acute coronary syndromes include
- STEMI
- NSTEMI
- unstable angina
what is difference between MI and angina
in MI there is occluding thrombus which leads to myocardial necrosis and a rise in serum troponins or creatine kinase
when does MI occur
when cardiac myocytes die due to myocardial ischaemia
how can MI be diagnosed
- appropriate clinical history
- ECG
- elevated biochemical markers (troponin, CK)
when should MI term be used
when there is evidence of myocardial necrosis in clinical setting
how many types of MI are there
5
what mechanism causes all ACS
rupture or erosion of the fibrous cap of a coronary artery plaque
what does rupture of platelet plaque lead to
- platelet aggregation and adhesion
- localised thrombosis
- vasoconstriction
- distal thrombus embolisation
what platelets cause vasoconstriction
- serotonin
- thromboxane A2
why does ischaemia occur
reduction of coronary blood flow
symptoms
- chest pain at rest
- indigestion
- pleuritic chest pain
- dyspnoea
what does ECG show
- ST depression
- T wave inversion
what does a complete occlusion of coronary vessel show on ECG
ST elevation
where is troponin located
with tropomyosin on the thin actin filament
what troponin attaches tropomyosin
T
what does troponin C bind
calcium during excitation-contraction coupling
what does troponin I inhibit
the myosin binding site on the actin
what does increased troponin mean
higher mortality rate in ACS
what is a standard marker for myocyte death
CK
is CK accurate
no
what is CK better at determining
re-infarction
what becomes elevated very early in MI
myoglobin
is myoglobin specific
no
what does ECG show for NSTEMI
- ST depression
- dynamic ST changes
what are risk factors for NSTEI
- age
- prior MI
- bypass surgery
- diabetes
- heart failure
what is used to diagnose NSTEMI
- raised troponin
- ECG
whats done first for NSTEMI
PCI (within 2 hours)
what drugs are given for support (MI)
- aspirin
- anti-plattelet
- anti thrombotic (LMWH)
- oxygen (if hypoxic)
what is given to patient for sickness
opiates + GTN
what does rupture of atheromatous plaque expose
the circulating platelets to ADP, thromboxane A2, adrenaline, thrombin and collagen tissue factor
what does platelet activation stimulate
the expression of glycoprotein IIb/IIIa receptor on platelet surface
what antiplatelet therapy should ACS patients be given
dual platelet therapy
aspirin and an ADP-receptor antagonist (clopidogrel or prasugrel or tricagrelor)
what else should be added to the antiplatelet therapy
antithrombin
what drug is given to reduce myocardial ischaemia
beta blocker
how do beta blocker reduce myocardial ischaemia
by blocking circulating catecholamines
lower heart rate and blood pressure
what drug blocks HMG CoA reductase
statins
what additional 2 drugs are routinely administered
- statins
- ACE inhibitors
what are single vessel lesions are treated with
PCI
why does myocardial infarction occur
when cardiac myocytes die due to prolonged myocardial ischaemia
how long does it take for myocardial necrosis to occur
15-30 minutes
how long would chest pain last before you come concerned about MI
20 minutes
does STEMI chest pain respond to sublingual glycerol trinitrate
no
where can the pain radiate in STEMI
to the left arm, neck or jaw
what are other symptoms that can occur in elderly
- dyspnoea
- fatigue
- pre-syncope
- syncope
what are other common symptoms of STEMI
- pale
- clammy
- marked sweating
- thready pulse
- hypotension
- bradycardia/tachycardia
what ECG leads are affected in STEMI
those facing the infarction
what ECG changes are evident in STEMI
ST elevation (due to opening of K channels)
what leads have ST elevation in anterior STEMI
II
III
AVF
what leads have ST elevation in later STEMI
I
AVL
V5
V6
what leads have ST elevation in poster STEMI
ST depression V1-V3
ST elevation in V5-V6
ST elevation in V3-V4 is where
anterior
ST elevation in V1-V3 is where
anteroseptal
ST elevation in: V4-V6 AVL I is where
anterolateral
ST elevation in
I
AVL
is where
latteral
ST elevation in: II III AVF is where
inferior
ST elevation in:
V1-V2 is where
posterior
what imaging can be helpful in STEMI
transthoracic echocardiography
what has to be done quickly once patient diagnosed with STEMI
PCI or thrombolysis
what is the initial medical therapy given for STEMI
- oxygen
- morphine (opioids)
- aspirin
MONA + C
what is the time frame for PCI
90 minutes
what should patients undergoing primary PCI be given in STEMI
- dual antiplatelet
- aspirin
- ADP-receptor blocker (e.g. prasugrel or tricagrelor)
what do fibrinolytics enhance
the breakdown of occlusive thromboses by the activation of plasminogen. to form plasmin
what can be used if PCI unavailable in STEMI
fibrinolysis (thrombolysis)
can prevent death
when is cardiac artery bypass surgery usually done in STEMI
for complications of MI
complications
- heart failure
- mitral regurgitation
- ventricular arrhythmia
- heart block
- rupture
- dresslers syndrome
what can heart failure caused by MI respond to
IV furosemide
what is required for heart failure treatment
oxygen
what is an early fatal event that can happen post MI
ventricle rupture
how can you repair a minor rupture
pericardiocentesis followed by surgical repair
what valvular disease can occur post MI
mitral regurgitation
what does cardiac arrest require
defibrillation
what should ventricular tachycardia post MI be treated with
beta blocker
lidocaine
or
amiodarone
treatment of post MI AF
beta blockers + digoxin
what is treatment for heart blocks post MI
permanent pacing
post-MI lifestyle modifications
- exercise programme
- dietary recommendations (increase veggies, reduce salt)
- reduce alcohol
- stop smoking
- maintain a healthy weight
- reduce blood pressure (if high)
- regulate patients with diabetes
post MI drug therapy
- aspirin
- ADP-receptor blocker
- oral beta blocker (maintain heart rate)
- ACE inhibitors / ARB
- statins
- aldosterone antagonist
whats preferred PCI or thrombolysis
PCI
