Flashcards in 15. Acute myocardial infarction Deck (20):
What is meant by an acute myocardial infarction (AMI)?
I.e. a heart attack
This occurs when blood flow to the heart stops to a part of the heart and causes damage to the heart muscle
Generally occurs following the rupture of an atheromatous plaque which can cause blood clots further down
What are the different classifications used for AMI?
STEMI - ST elevation Myocardial Infarction
NSTEMI - Non-ST elevation Myocardial Infarction
Give the pathophysiology of NSTEMI
Ruptured coronary plaque results in subocclusive thrombus i.e. the artery is not completely blocked but there is some form of blockage that prevents blood flow
How does an NSTEMI show in an ECG and how is it diagnosed?
For an NSTEMI, the ECG may be normal or may show ST depression or pathological T waves
For an NSTEM, the ECG is not diagnostic and you must await troponin analysis
Give the pathophysiology for a STEMI
The ruptured coronary plaque results in an occlusive thrombus - the artery is completely blocked and blood flow is hence completely blocked
How does a STEMI appear on an ECG and how is this diagnosed?
For a STEMI, the ACG shows an ST elevation
For a STEMI, the ECG is diagnostic
Why is it important to determine whether the AMI is STEMI or NSTEMI?
The treatment for both of these are different to each other SO should know which one the patient has
Why might an AMI be STEMI vs. NSTEMI and vice versa?
Whether the AMI is STEMI or NSTEMI is dependent on the type of blood of the patient
I.e. if a patient smokes, their blood is more likely to be sticky and this is more likely to result in a STEMI
If the patient is on anti-platelets e.g. aspirin, then the patient is more likely to present with NSTEMI (this is how aspirin works as a secondary prevention drug)
What are the clinical manifestations of an AMI?
Ischaemic myocardial injury can result in chest pain, a 4th heart sound, low grade fever (this is due to the leakage of proteins which stimulates an inflammatory response), leak of component trononin
Autonomic disturbance due to massive symaptho-adrenal response leading to tachycardia and also activation of vagus leading to sweating and vomiting and maybe bradycardia
Describe the prognosis of AMI and the major cause of death in these patients
Not a good prognosis
40% of patients are dead after the first year of their AMI
Due to left ventricular failure, cardiogenic shock is a major cause of their death
NB. the development of this is dependant on how bad the damage is i.e. the size of the block and the level of ischaemia (SO need to limit the amount of damage in these patients to provide them with a better prognosis)
What is meant by cardiogenic shock?
Inadequate circulation of blood and insufficient perfusion of tissue to meet oxygen demands - this can lead to cardiac arrest which is the cause of death
What is meant by cardiac arrest?
A sudden stop in effective blood flow due to a failure of the heart to contract effectively
What are the two main treatment methods to treat STEMI?
Reduce the infarct size
What treatment is used for STEMI to reduce the infarct size?
Use of thrombolytic drugs -these drugs work to dissolve blood clots
There are two main types - streptokinase and tissue plasminogen activator (tPA)
Streptokinase lysis the fibrin in the thrombus directly
tPA converts plasma protein plasmolinogen to plasmin which then lysis the fibrin in the thrombus
This lysis results in restoration of the blood flow
Beta Blockers should also be administered to improve rate of survival after the infarction (should be started upon admission)
What is the main complication associated with thrombolytic drugs?
Bleeding and haemorrhage - haemorrhagic stroke
This can occur at the injection site (of drug), the GI tract or elsewhere
Can then lead to hypotension
When should streptokinase be administered and what is the main concern with this drug?
Should be administered up to 12 hours after the onset of symptoms via IV infusion
Streptokinase can only be used once due to the development of autoantibodies against the drug which can result in an allergic reaction and anaphylaxis
Describe the use of reperfusion therapy to treat STEMI
Primary PCI is used - primary percutaneous coronary intervention
Involves placing a wire down and across the blockage and inserting a stent to allow the coronary artery to open up
This needs to be done immediately once the patient comes into the hospital wth STEMI
Should also be given anti-platelet drugs e.g. aspirin/heparin as they are about to have PCI
What is the main treatment for NSTEMI and why does this differ to STEMI?
Treatment for STEMI differs to NSTEMI because as the artery is not completely occluded, the main priority is not preventing the block but instead is looking at keeping the artery open and preventing further blockages
Give anti-platelets e.g. aspirin and tricagrelor
Provide anti-ischaemic drugs for the pain
Then administer a PCI - SO still need the same treatment but the urgency for this is not the same as it was for STEMI - dependant on the clinical situation
Give some common anti-platelet drugs that can be used (generally)