Acute Coronary Syndrome: Overview

Related Subjects: |Acute Coronary Syndrome: Overview |Atherosclerosis |Ischaemic heart disease |Assessing Chest Pain |Acute Coronary Syndrome (ACS): Complications |ACS - General |ACS - STEMI |ACS - NSTEMI |ACS - GRACE Score |ACS - ECG Changes |ACS -Cardiac Troponins |ACS - Post MI arrhythmias |ACS: Right Ventricular STEMI |ACS: Sgarbossa Criteria |Wellen's syndrome

❤️ A Myocardial Infarction (MI) refers to necrosis of cardiac muscle due to prolonged ischaemia, most often from coronary artery thrombosis. It is a leading cause of morbidity and mortality worldwide, with outcomes improved by rapid recognition and early reperfusion therapy.

🔬 Pathophysiology

• 📉 Atherosclerotic plaque rupture or erosion → platelet aggregation → thrombus formation → coronary occlusion.
• ⚡ Imbalance between myocardial oxygen supply and demand → ischaemia → necrosis (after ~20–40 minutes of occlusion).
• 🧩 STEMI: complete occlusion of coronary artery; NSTEMI: partial occlusion or distal embolisation.
• 🧪 Histology: coagulative necrosis, neutrophilic infiltration, followed by granulation tissue and fibrosis.

⚠️ Risk Factors

• 🚬 Smoking.
• 💉 Hypertension, diabetes mellitus, dyslipidaemia.
• 👴 Age, male sex, family history of premature CAD.
• ⚖️ Obesity, sedentary lifestyle, poor diet.
• 💊 Cocaine use or vasospastic disorders (e.g. Prinzmetal angina).

🧩 Clinical Features

• 💔 Central chest pain: heavy, crushing, radiating to arm, neck, or jaw;>20 min; not relieved by rest or GTN.
• 😰 Associated symptoms: sweating, nausea, vomiting, palpitations, dyspnoea, syncope.
• 🩺 Examination: tachycardia or bradycardia, hypotension, raised JVP, added heart sounds, pulmonary oedema.
• 👵 Elderly, diabetics, and women may have atypical presentations (e.g. syncope, confusion, epigastric pain, silent MI).

🔎 Differential Diagnosis

• Unstable angina.
• Aortic dissection.
• Massive PE.
• Pericarditis.
• GORD or musculoskeletal chest pain.

🧪 Investigations

• 📊 ECG:
  • STEMI → ST elevation ≥1 mm in ≥2 contiguous limb leads, or ≥2 mm in chest leads, ± new LBBB.
  • NSTEMI → ST depression, T-wave inversion, or non-specific changes.
• 🧬 Cardiac biomarkers: Troponin I/T rises within 4–6h, peaks at 12–24h, normalises in 7–14 days.
• 🧪 Bloods: FBC, U&E, glucose, lipids, coagulation screen.
• 🩻 CXR: pulmonary oedema, exclude alternative diagnoses.
• 🩺 Echocardiography: regional wall motion abnormalities, LV dysfunction, complications (VSD, MR, pericardial effusion).

🚑 Immediate Management (MONA-BASH)

• 💊 Morphine + Metoclopramide (for pain and nausea).
• 💨 Oxygen if sats <94%.
• 💊 Nitrates (GTN spray if BP adequate).
• 💊 Aspirin 300 mg PO stat.
• 💊 Beta-blocker (if no contraindication).
• 💊 ACE inhibitor within 24h (start low, titrate up).
• 💊 Statin high-intensity (e.g. atorvastatin 80 mg).
• 💉 Heparin / fondaparinux.

📊 Comparison: STEMI vs NSTEMI vs Unstable Angina

⚡ Reperfusion Therapy

• ⏱️ Primary PCI: gold standard if available within 120 min of diagnosis.
• 💉 Thrombolysis (alteplase, tenecteplase): if PCI not possible within 2h of first medical contact.
• 📉 Rescue PCI: if thrombolysis fails (persistent ST elevation).

🏥 Inpatient / Long-term Management

• 💊 Dual antiplatelet therapy (Aspirin + clopidogrel/ticagrelor).
• 💊 Beta-blocker, ACE inhibitor/ARB, statin, aldosterone antagonist if LV dysfunction.
• 🩺 Cardiac rehabilitation: exercise, diet, psychological support.
• 🚭 Lifestyle modification: smoking cessation, weight loss, BP/glucose control.

⚠️ Complications

• 🫀 Arrhythmias: VF/VT, complete heart block, AF.
• 💧 Cardiogenic shock, LV failure, pulmonary oedema.
• 🩸 Mechanical: papillary muscle rupture → MR, VSD, free wall rupture → tamponade.
• 🧠 Thromboembolism → stroke, systemic emboli.
• 💔 Dressler’s syndrome: autoimmune pericarditis weeks post-MI.

💡 Teaching Pearls

🔑 Always obtain an ECG within 10 min of arrival for chest pain. ⏱️ “Time is muscle” - early reperfusion saves myocardium. ⚠️ Elderly and diabetic patients often present atypically; maintain a high index of suspicion. 🏥 All post-MI patients in the UK should be discharged on secondary prevention: DAPT, beta-blocker, ACEi, statin, and enrolled in cardiac rehab.

❤️ Case 1 - ST-Elevation Myocardial Infarction (STEMI)

A 58-year-old man presents with sudden severe central chest pain radiating to the left arm, associated with sweating and nausea. ECG shows ST elevation in leads II, III, and aVF. 💡 STEMI results from complete occlusion of a coronary artery by thrombus, causing transmural infarction. It is a time-critical emergency requiring immediate reperfusion - primary PCI if available within 120 minutes, or thrombolysis if not.

❤️ Case 2 - Non-ST Elevation Myocardial Infarction (NSTEMI)

A 72-year-old woman with diabetes and hypertension presents with prolonged chest tightness at rest. ECG shows ST depression in the lateral leads, and troponin is elevated. 💡 NSTEMI reflects partial coronary occlusion causing subendocardial infarction. Risk stratification (e.g. GRACE score) guides early invasive management. Treatment includes dual antiplatelet therapy, anticoagulation, and optimisation of secondary prevention.

❤️ Case 3 - Unstable Angina

A 65-year-old man with known angina reports worsening chest pain at rest and on minimal exertion, lasting longer than usual. ECG is normal, and troponin is not elevated. 💡 Unstable angina represents ACS without myocardial necrosis. It shares pathophysiology with NSTEMI (plaque rupture and thrombus) but without biomarker rise. Management includes hospital admission, anti-platelets, anticoagulation, and consideration of early coronary angiography.