Acute Coronary Syndrome (ACS): Chest Pain ❤️

⚡ ST elevation changes everything! → urgent coronary reperfusion required. 📉 A 12-lead ECG must be performed within 10 minutes of arrival for suspected ACS. 👵 Large myocardial infarctions may be silent in elderly or diabetic patients. 🫀 Early reperfusion saves myocardium → primary PCI is the preferred treatment.

📖About

ACS describes a spectrum of conditions caused by acute myocardial ischaemia due to coronary plaque rupture and thrombosis. ACS includes unstable angina, NSTEMI, and STEMI. 📈 The ECG differentiates STEMI (urgent reperfusion required) from NSTEMI/unstable angina. 🧪 A rise and/or fall in troponin confirms myocardial injury.

🧬 Aetiology

Most cases of acute coronary syndrome (ACS) occur when an atherosclerotic plaque ruptures or erodes within a coronary artery. This exposes thrombogenic material from the lipid core to circulating blood, triggering platelet activation, aggregation, and thrombus formation. The resulting clot reduces or blocks coronary blood flow, producing the spectrum of unstable angina, NSTEMI, or STEMI depending on the degree and duration of occlusion. Less common causes include coronary artery spasm, spontaneous coronary artery dissection, coronary embolism, and oxygen supply–demand mismatch (e.g. severe anaemia, sepsis, or tachyarrhythmia). Understanding this mechanism explains why ACS treatment focuses on antiplatelet therapy, anticoagulation, and rapid reperfusion.

🎓 Exam Tips

• 🧠 Most ACS events are caused by plaque rupture with thrombosis – this is the classic exam answer.
• ⚡ STEMI usually reflects complete coronary occlusion, whereas NSTEMI often reflects partial occlusion.
• 🧪 A diagnosis of myocardial infarction requires a rise and/or fall in troponin plus evidence of myocardial ischaemia.
• ⚠️ Not all troponin elevations represent ACS – think about Type 2 myocardial infarction (e.g. sepsis, PE, tachyarrhythmia).
• 📈 Early ECG changes may be subtle – repeat ECGs are essential if symptoms persist.

🔎 Types of Acute Coronary Syndrome

• 🟡 Unstable angina → ischaemic symptoms without troponin elevation
• 🟠 NSTEMI → myocardial necrosis without ST elevation
• 🔴 STEMI → transmural infarction with ST elevation

📊 NSTEMI vs STEMI

⚠️ Aetiology

• 🟢 Most ACS results from rupture or erosion of an atherosclerotic plaque.
• 🩸 Platelet activation and thrombus formation reduce coronary blood flow.
• ⏱️ “Time = muscle” → delayed reperfusion worsens myocardial damage.

🧬 Pathophysiology

• 🔓 Plaque rupture exposes thrombogenic material.
• 🧬 Platelets aggregate and activate the coagulation cascade.
• ⛔ Coronary blood flow decreases → myocardial ischaemia.
• 💔 Persistent occlusion leads to irreversible myocardial necrosis.

📑 Universal Classification of MI

⚠️ Not all troponin elevations represent coronary thrombosis. Type 2 myocardial infarction occurs when oxygen supply–demand mismatch causes myocardial injury.

⚠️ Risk Factors

• 👨 Age >40 (men) or >50 (women)
• 🚬 Smoking
• 🍔 Dyslipidaemia
• 💉 Diabetes
• ⬆ Hypertension
• 🧬 Family history of premature coronary disease

🩺 Clinical Presentation

• 🚨 Central crushing chest pain radiating to arm or jaw
• 😰 Sweating, nausea, feeling of impending doom
• 👵 Elderly or diabetic patients may present atypically
• 🫀 Signs of heart failure or cardiogenic shock in severe infarction

⚠️ Atypical Presentations may be seen in older adults, women, and patients with diabetes. Symptoms may include breathlessness, epigastric discomfort, nausea, vomiting, fatigue, dizziness, or syncope rather than obvious chest pain. Some patients describe only indigestion-like discomfort, jaw pain, or isolated arm pain. Diabetic patients may develop silent myocardial ischaemia due to autonomic neuropathy, resulting in minimal or absent pain despite significant myocardial injury. Because atypical presentations are common in high-risk groups, clinicians should maintain a low threshold for performing an ECG and checking troponin when evaluating unexplained acute symptoms.

🧪 Investigations

• 12-lead ECG within 10 minutes
• High-sensitivity troponin at presentation and repeat after 1–3 hours
• Blood tests: FBC, U&E, glucose
• Chest X-ray to exclude other pathology
• Echocardiography if haemodynamic instability or complications suspected

🫀 Management of Acute Coronary Syndrome

Management priorities: 1️⃣ Rapid diagnosis 2️⃣ Relieve myocardial ischaemia 3️⃣ Prevent thrombus propagation 4️⃣ Restore coronary perfusion

💊 Immediate Treatment

⚡ Reperfusion Strategy

• Primary PCI is the preferred treatment for STEMI.
• If PCI cannot be delivered promptly → consider thrombolysis.
• High-risk NSTEMI → early invasive coronary angiography.

⚠️ Complications of ACS

• ⚡ Ventricular arrhythmias (VT/VF)
• 💔 Cardiogenic shock
• 🫀 Heart failure
• 🧬 Mechanical rupture (papillary muscle, septum)
• 🧫 Pericarditis

💊 Secondary Prevention

• 🛡 Beta-blocker (once haemodynamically stable)
• 💊 Atorvastatin 80 mg
• 💊 ACE inhibitor
• 💊 Dual antiplatelet therapy
• 🚭 Smoking cessation
• 🥗 Lifestyle modification + cardiac rehabilitation

🧠 Advanced Clinical Insights (High-Yield)

These concepts are frequently tested in clinical exams and help explain real-world ACS management decisions.

Troponin Interpretation

• Troponin elevation indicates myocardial injury, not necessarily coronary thrombosis.
• Diagnosis of MI requires troponin rise/fall plus evidence of ischaemia.
• Common non-ACS causes include sepsis, pulmonary embolism, myocarditis, tachyarrhythmia, and renal failure.

ECG Evolution in STEMI

• Hyperacute T waves
• ST elevation
• Pathological Q waves
• T-wave inversion

Posterior Myocardial Infarction

• Often presents with ST depression in V1–V3
• Tall R waves may be seen
• Posterior leads (V7–V9) may reveal ST elevation

Right Ventricular Infarction

• Usually occurs with inferior MI due to RCA occlusion
• Features: hypotension, clear lungs, raised JVP
• Diagnosis confirmed with right-sided ECG leads
• Management: avoid nitrates; give cautious IV fluids

📚 References

• NICE NG185: Acute Coronary Syndromes
• NICE NG136: Myocardial Infarction Secondary Prevention

💡 Clinical Pearl The most common early cause of death in acute MI is ventricular arrhythmia. Rapid ECG diagnosis and immediate reperfusion remain the most important life-saving steps in ACS management.