Acute coronary syndrome Flashcards
What is ACS?
Acute coronary syndrome (ACS) refers to a set of symptoms and signs that occur due to reduced blood flow to the heart at rest. It encompasses 3 distinct diagnoses: unstable angina, non-ST elevation myocardial infarction (NSTEMI), and ST elevation myocardial infarction (STEMI). In the case of infarction, this is a medical emergency requiring urgent treatment.
(Clinical manifestation MI.)
What is unstable angina?
Acute myocardial ischaemia that is not severe enough to cause detectable quantities of myocardial injury biomarkers or ST-segment elevations on ECG.
What is NSTEMI?
“Non-ST-segment elevation myocardial infarction”
Acute myocardial ishemia that is severe enough to cause detectable quantities of myocardial injury biomarkers but without ST-segment elevations on ECG.
What is a STEMI?
“ST- segment elevation myocardial infarction”
Acute myocardial ischaemia that is severe enough to cause ST-segment elevations on ECG
What causes ACS?
Mostly due to atherosclerosis.
Describe the pathophysiology behind ACS
- Coronary artery disease refers to the narrowing of coronary arteries by atherosclerosis and plaque formation.
- In stable angina, when the demand for myocardial oxygen increases with exertion, narrowed coronary arteries cannot meet this increased demand leading to myocardial ischaemia and pain.
- Conversely, in ACS, the symptoms occur at rest. This is because there is sudden plaque rupture and clot formation in the narrowed coronary arteries.
- If there is partial occlusion of the coronary artery this leads to ischaemia and chest pain at rest (unstable angina).
- If the coronary artery becomes more occluded or fully occluded this leads to significant hypoperfusion of the myocardium and ultimately leads to infarction (death) of the myocardial tissue (NSTEMI or STEMI).
What are the risk factors of ACS?
- Smoking
- Hypertension
- Family history
- Diabetes
- Hyperlipidaemia
- Hypercholesterolaemia
- Obesity
- Advanced age
- Peripheral vascular disease
- Stress
- High fat diets
- Physical inactivity
What are the different types of ACS?
- Unstable angina: caused by partial occlusion of a coronary artery. Troponin negative chest pain with normal/abnormal ECG signs.
- Non-ST Elevation Myocardial Infarction: caused by severe but incomplete occlusion of a coronary artery. Troponin positive chest pain without ST elevation.
- ST-Elevation Myocardial Infarction: caused by complete occlusion of a coronary artery. Troponin positive chest pain with ST elevation on ECG.
What are the presenting symptoms of ACS?
- Acute central chest pain → dull, squeezing tightness. Usually radiates to left chest, arm, shoulder, neck, jaw or epigastrium
- Dyspnoea (especially on exertion)
- Sweating
- Pallor
- N&V
- Dizziness & Syncope
- Atypical Presentations ⇒ may be painless in patients with diabetes
What signs of ACS can be found on physical examination?
- ACS: May have no clinical signs. Pale, sweating, restless, low-grade pyrexia. Check both radial pulses for aortic dissection.
- Arrhythmias, disturbances of BP. New heart murmurs (e.g. pansystolic murmur of mitral regurgitation from papillary muscle rupture or ventricular septal defect).
- Signs of complications, i.e. acute heart failure, cardiogenic shock (hypotension, cold peripheries, oliguria).
What investigations are used to diagnose/ monitor ACS?
- 12-Lead ECG → best initial test. Differentiate between STEMI & NSTEMI to determine treatment. Repeat every 15-30 mins in the first hour:
- NSTEMI → ST depression and T wave inversion
- STEMI → ST elevation and new LBBB.
*ST Elevation >2mm in adjacent chest leads (V1-V6) and >1mm in adjacent limb leads (II,III,avF,avL)
*PAIL (Posterior-Anterior-Inferior-Lateral) ⇒ ST elevations in these leads most commonly create reciprocal ST depressions in the corresponding leads of the next letter in the mnemonic. - Cardiac Troponin Levels → measure ASAP and repeat after 1-6 hrs. Typically rise 3 hours after MI begins.
- Troponin remains elevated for 10 days after infarction
- CK-MB remains elevated for 3-4 days following infarction → hence most useful to look for reinfarction (ie. troponin may still be elevated from intial infarct)
How would you interpret ECG findings to localise a STEMi?
- Anteroseptal (V1-V4)= left anterior descending artery
- Inferior (II, III, aVF)= Right coronary artery
- Lateral (I, aVL +/- V5-6)= left circumflex
(main 3 to learn) - Anterolateral (V4-6, I, aVL)= left anterior descending or left circumflex artery
- Posterior (changes in V1-3)= usually left circumflex, also right coronary artery
How is ACS managed?
General management for all ACS:
MOAN (Tx for Acute ACS) → Morphine (patients with severe pain), Oxygen (only if sats <94%), Aspirin (300mg), Nitrates (contraindicated if hypotensive, <90mmHg)
STEMI:
- Aspirin 300mg and continue indefinitely
- Symptoms <12h and PCI (Percutaneous coronary intervention) possible in 2h → Angiography + PCI
*Also give Prasugrel if undergoing PCI
- Symptoms <12h and PCI not possible in 2h → Thrombolysis (alteplase + antithrombin)
If present >12h after symptoms, manage pharmacologically.
Unstable Angina/NSTEMI:
1. 1st Line → Aspirin 300mg (and continue indefinitely) + Fondaparinux (activates antithrombin III - given unless high bleeding risk or immediate PCI planned)
*If immediate angiography = aspirin + unfractionated heparin (preferred due to easier reversibility with protamine sulfate)
2. Calculate GRACE (estimated 6 month mortality)
*Low Risk (6 month mortality ≤3%) → aspirin + ticagrelor/clopidogrel (ticagrelor if not high bleeding risk, clopidogrel if high bleeding risk)
*Intermediate/High Risk (6 month mortality >3%) → angiography with follow up PCI if indicated (72h). Give ticagrelor + aspirin.
- If patients haemodynamically unstable ⇒ immediate coronary angiography with PCI
Secondary Prevention of MI (long-term management) → Dual Antiplatelet Therapy (aspirin + ticagrelor/clopidogrel), ACEi (ramipril), Beta Blocker (bisoprolol), Statin (Atorvastatin 80mg)
What is the difference between right and left BBB?
- LBBB ⇒ WiLLiaM → ‘W’ in v1, ‘M’ in v6
- Always Pathological → may be due to MI, hypertension, aortic stenosis, cardiomyopathy, hyperkalaemia
- New onset LBBB should prompt investigation for ACS (ie. troponin levels) - RBBB ⇒ MaRRoW → ‘M’ in v1, ‘W’ in v6
- Can be normal (more common with increasing age). May also be due to RVH or chronically increased right ventricular pressure (cor pulmonale).
What complications may arise from ACS?
Ventricular arrhythmia
Recurrent ischaemia/infarction/angina
Acute mitral regurgitation
Congestive heart failure
2nd, 3rd degree heart block
Cardiogenic shock
Cardiac tamponade
Ventricular septal defects
Left ventricular thrombus/aneurysm
Left/right ventricular free wall rupture
Dressler’s Syndrome
Acute pericarditis
