Acute myocardial infarction/ACS Flashcards
What is acute coronary syndrome?
umbrella term covering a number of acute presentations of ischaemic heart disease, including:
- ST elevation myocardial infarction (STEMI)
- Non-ST elevation myocardial infarction (NSTEMI)
- Unstable angina
What is meant by ischaemic heart disease?
synonymous with coronary heart disease; gradual build up of fatty plaques within walls of coronary arteries
What are the 2 main problems associated with fatty plaques deposited in the walls of the coronary arteries in ischaemic heart disease?
- Gradual narrowing: less blood + therefore oxygen to myocardium at times of increased demand → angina
- Risk of sudden plaque rupture: plaques in endothelium may rupture causing sudden occlusion of the artery → no blood/oxygen reaching the area of myocardium
What is angina?
chest pain due to insufficient oxygen reaching the myocardium during exertion
What are 3 unmodifiable risk factors for ischaemic heart disease?
- Increasing age
- Male gender
- Family history
What are 5 modifiable risk factors for ischaemic heart disease?
- Smoking
- Diabetes mellitus
- Hypertension
- Hypercholesterolaemia
- Obesity
What are 6 stages to the pathophysiology of ischaemic heart disease?
- Initial endothelial dysfunction triggered by factors e.g. smoking, HTN, hyperglycaemia
- Results in changes to endothelium: pro-inflammatory, pro-oxidant, proliferative and reduced nitric oxide bioavailability
- Fatty infiltration of subendothelial space by low-density lipoprotein (LDL) particles
- Monocytes migrate from blood and idfferentiate into macrophages: phagocytose oxidised LDL, turning into large ‘foam cells’. As they die can propagate inflammatory process
- Smooth muscle proliferation and migration from tunica media into intima results in formation of fibrous capsule covering fatty plaque
What can result if the plaque within a coronary artery ruptures?
can cause complete occlusion of coronary artery which may result in myocardial infarction
What are 5 key symptoms of acute coronary syndrome?
- Chest pain
- Dyspnoea
- Sweating
- Nausea and vomiting
- Palpitations
How is the chest pain of ACS typically described?
- central/left-sided
- may radiate to jaw or left arm
- often described as ‘heavy’ or ‘constricting’, ‘like an elephant on my chest’
- but can be wide variety of types of chest pain
What are 2 examples of groups of patients who may not experience any chest pain in ACS?
- Diabetics
- Elderly patients
What may observations (vital signs) show in a patient with ACS?
pulse, BP, temperature and oxygen sats often normal or only mildly altered e.g. tachycardia
What may be seen on examination in patients with ACS?
- if complication has developed e.g. cardiac failure - signs of this
- pale, clammy
What are the 2 most important investigations when assessing a patient with chest pain?
- ECG
- Cardiac markers e.g. troponin
What are the 5 broad groups of territories affected by ACS and the corresponding ECG leads and arteries?
- Anterior: V1-V4: left anterior descending artery
- Inferior: II, III, aVL: right coronary artery
- Anterolateral: V4-6, I, aVL: left anterior descending or left circumflex
- Lateral: I, aVL ± V5-6: left cicumflex artery
- Posterior: tall R waves, V1-2: left circumflex, right coronary
(also new LBBB anywhere)
How do the LAD, right coronary and left circumflex arteries relate to each other?
left coronary artery and right coronary artery arise from the ascending aorta
left coronary artery splits into left anterior descending and left circumflex
What are the 3 aims of treatment of ACS?
- Prevent worsening of presentation (further occlusion of coronary vessel)
- Revascularise the vessel if occluded (patients with STEMI)
- Treat pain
What is the commonly taught mnemonic for the treatment of ACS generally?
MONA:
Morphine IV (±anti-emetic) - only if severe pain
Oxygen (if sats <94)
Nitrates
Aspirin (300mg, often given pre-hospital)
For patients who have presented with STEMI, what are 3 additional aspects of the management as well as MONA?
- Second antiplatelet drug shoudl be given in addition to aspirin - options include clopidogrel, prasugrel and ticagrelor
- PCI (percutaneous coronary intervention)
- Before PCI introduced, thrombolysis with clot-busting drug was used to break down the thrombus
What does PCI involve?
catheter inserted into either radial or femoral artery; blocked arteries opened up using a balloon (angioplasty) folowing whcih a stent may be deployed ot prevent the artery occluding again in the future
If a patient presents with NSTEMI (no ST elevation on ECG) what are 2 steps that can be taken to determine further management (in addition to MONA)?
- Risk stratification tool such as GRACE can be used to decide upon further management
- If considered high-risk or clinically unstable, coronary angiography performed during admission
- if lower risk, patient can have coronary angiogram at later date
What are 5 types of medications that patients are prescribed lifelong following ACS to reduce risk of a further event?
- Aspirin
- Second antiplatelet if appropriate (e.g. clopidogrel)
- Beta-blocker
- ACE-inhibitor
- Statin
What is the name of the system used to stratify risk post-myocardial infarction?
GRACE (Global Registry of Acute Coronary Events) score
What are 9 poor prognostic factors in acute coronary syndrome according to the GRACE score?
- Age
- Development (or history) or heart failure
- Peripheral vascular disease
- Reduced systolic blood pressure
- Killip class
- Initial serum creatinine concentration
- Elevated initial cardiac markers
- Cardiac arrest on admission
- ST segment deviation (elevation or depression)
What is Killip class and what are the 4 categories?
system sed to stratify risk post-myocardial infarction
- I: no clinical signs of heart failure (6% 30-day mortality)
- II: lung crackles, S3 (17%)
- III: frank pulmonary oedema (38%)
- IV: cardiogenic shock (81%)
What is the definition of ST-elevation?
ST-segment elevation and elevated biomarkers of myocardial damage
What are the criteria for NSTEMI?
ECG changes but no ST-segment elevation, + elevated biomarkers of myocardial damage
What are the 2 groups into which to categories patients with ACS for management?
- STEMI
- NSTEMI/unstable angina
When should IV morphine be given in ACS and what may be a disadvantage of it?
only if patient is in severe pain
previously given routinely but evidence suggests this may be associated with adverse outcomes
In which patients should nitrates be used to manage ACS with caution?
hypotensive patients (can worsen)
Following the MONA treatment what is the next step to determine what further treatment is indicated for ACS?
determine if patient meets ECG criteria for STEMI (interpret in context of clinical history)
What are the ECG/clinical criteria for a STEMI diagnosis?
- clinical symptoms consistent with ACS (>20 minutes duration) with persistent (>20min) ECG features in 2 or more contiguous leads of:
- 2.5 mm (≥ 2.5 small squares) ST elevation in leads V2-3 in men <40 years, or ≥ 2.0 mm (i.e ≥ 2 small squares) ST elevation in leads V2-3 in men over 40 years
- 1.5 mm ST elevation in V2-3 in women
- 1mm ST elevation in other leads
- new LBBB (LBBB should be considered new unless evidence otherwise)
What are 3 factors which determine whether ST elevation is considered significant?
- Gender: in V2-3, 2-2.5 needed in males, 1.5 in females
- Age: in V2-3, 2mm needed in male >40, 2.5mm needed in male <40
- Leads: 1mm only needed in leads other than V2-3
When should LBBB be considered new?
always consider new (and therefore evidence of STEMI) unless evidence otherwise