Acute Coronary Syndrome Flashcards
What does ACS include?
- Unstable angina
- N-STEMI
- STEMI
What is a STEMI?
- An ST elevation myocardial infarction
- A persistent ST segment elevation or new LBBB on their ECG.
What size must the ST elevation be?
How many leads must the ST elevation be in?
- > 1mm in limb leads
- > 2mm in chest leads
The STEMI must be present in 2 contiguous leads.
What will hs-TnI level be in a STEMI?
> 100ng/L
What will CK level be in STEMI?
> 400
What is the pathophysiology of a STEMI?
A complete atherothrombotic occlusion of a coronary artery, causing myocardial cell death.
- Occurs after an abrupt and catastophic disruption of a cholesterol laden plaque.
- This promotes platelet activation and aggregration, thrombin generation and thrombus formation.
- This interrupts blood flow in the coronary arteries.
- The artherothrombotic occlusion causes myocardial cell necrosis.
What is the pathophysiology of athersclerotic plaques?
- They form gradually over years, beginning with the accumulation of LDL in the intima of blood vessels.
- Leukocytes (macrophages) adhere to the endothelium, then enter the intima and accumulate lipids and become foam cells.
- The lesion is called a fatty steak and is proinflammatory.
- Smooth muscle cells infiltrate from the media and proliferate.
- They deposit extracellular matrix (collagen and elastin) and form a plaque as they undergo apoptosis.
- The plaque enroaches on the arterial lumen and causes stenosis, limiting blood flow.
How does an MI cause heart failure?
- A significant portion of the myocardium undergoes ischaemic injury and cannot perform contractile work.
- LV pump volume becomes depressed: CO, SV, BP, compliance is reduce so ESV increases.
How does cardiogenic shock occur?
If 40% of the LV myocardium is lost.
After a 12 lead ECG shows ACS, what other ECG leads should you investigate and why?
- V7, V8, V9 (posterior leads) as anterior leads may show ST depression as there is a posterior STEMI.
- RV3, RV4, RV5, RV6 (right ventricular leads) as RV4 is very sensitive for RV MI.
How would you investigate a suspected MI?
- ECG
- CXR - Cardiomegaly, pulmonary oedema, widened mediastium
- FBC, U+E, LFT, glucose, lipids, cardiac enzymes, HbA1C
- Echocardiogram - Regional wall abnormalities
What should you keep in mind when interpreting troponin levels?
- Can rise with other causes of myocardial damage - myocarditis, pericarditis, ventricular strain (troponins likely to change little hour by hour)
- Iatrogenic causes of troponin rise - CPR, DC cardioversion, ablation therapy
- Non cardiac causes - massive PE causing RV strain, burns, sepsis, SA haemorrhage, renal failure
- The CHANGE in troponin is more important than the troponin level itself
What are the ECG changes with a STEMI?
- Hyperacute T waves, ST elevation, new LBBB within hours
2. T wave inversion and pathological Q wave in days
What are some symptoms of an MI?
Acute central chest pain lasting over 20 minutes
Nausea, sweatiness, dyspnoea, palpitations
How does a silent MI present?
Syncope, pulmonary oedema, epigastric pain and vomiting, post operative hypotension, oliguria, acute confusion, stroke
What are some signs of an MI?
- Distress, anxiety, pallor, sweatiness
- Pulse and BP increased/decreased
- Signs of heart failure - Raised JVP, 3rd heart sound, basal crepitations
- Pansystolic murmur
- Later - pericardial rub and peripheral oedema
A patient has had an ECG and is found to have a STEMI - how do you manage them?
- Get IV access
- Pain relief (morphine 2.5m-5mg IV and antiemetic metoclopramide 10mg IV)
- Oxygenation (if hypoxic, aim for 94%)
- Aspirin (300mg loading chew tablet, then 75mg od for life)
- Antiplatelets - Prasugrel 60mg loading, then 10mg OD for 12 months, clopidogrel 600mg loading, then 75mg OD for 12 months if prasugrel unsuitable. Ticagrelor is preferred to clopidogrel.
- Primary PCI if available within 120 minutes and within 12hrs of onset, if not consider fibrinolysis.
When is prasugrel inappropriate to give as an antiplatelet?
- Patients over 75
- Previous TIA/stroke
- Patient weighs under 60kg
After immediate management, what can be given for pain relief in ACS?
- GTN spray
- Opiates
How can patient risk factors be modified?
- Stop smoking
- Identify and treat diabetes, hypertension and hyperlipidaemia
- Diet high in oily fish, fruit, veg and fibre. Low in saturated fat
- Encourage daily exercise
- Mental health referral
What cardioprotective medication should be given after an MI?
- Antiplatelet - aspirin for life
- Second antiplatelet - clopidogrel for 12 months minimum
- Anticoagulate until discharge eg fondaparinux
- Beta blocker - bisoprolol (not in shock/hypotension) to reduce myocardial O2 demand
- Ace-i - If LV dysfunction, HTN, diabetes
- High dose statin eg atorvastatin
What are risk factors for an ACS?
Non modifiable - Age, male, FH of IHD,
Modifiable - Smoking, hypertension, DM, hyperlipidaemia, obesity, sedentary lifestyle, cocaine use
What is the management for a NSTEMI or unstable angina?
- Analgesia - morphine and metoclopramide
- Nitrates - GTN prn
- Aspirin 300mg loading, 75mg OD
- Repeat ECG at regular intervals
Measure troponin and clinical parameters to risk assess (GRACE score)
If high risk: - LMWH - Enoxaparin for 48hr
- Ticagrelor 180mg loading and 80mg BD
- IV nitrates if pain continues
- Oral beta blockers eg bisoprolol
- Inpatient cardiologist review for angiography
If low risk:
- Outpatient investigations eg stress test
What will an ECG show with unstable angina and STEMI?
- ST segment depression
- T wave flattening or inversion
Name some complications of MI?
- Cardiac arrest
- Cardiogenic shock
- Left ventricular failure/Right ventricular failure
- Arrythmia
- Pericarditis
- Systemic embolism
- Cardiac tamponade
- Mitral regurgitation
- Ventricular septal defect
