Non-ST-Elevation Acute Coronary Syndrome (NSTE-ACS) — SAQ

Stem

A candidate is asked to manage a classic presentation of Non-ST-Elevation Acute Coronary Syndrome (NSTE-ACS) in an exam setting. Use precise definitions, scores, doses, and decision thresholds.

Core knowledge (model answer backbone)

Non-ST-elevation acute coronary syndrome (NSTE-ACS) is myocardial ischaemia at rest or on minimal exertion caused by a partially or intermittently occlusive intra-coronary thrombus over a disrupted atherosclerotic plaque, but without the ST elevation that mandates immediate reperfusion. It comprises NSTEMI (myocardial necrosis demonstrated by a rise and/or fall of high-sensitivity cardiac troponin with at least one value above the 99th centile) and unstable angina (ischaemia without troponin release). Diagnosis rests on the 12-lead ECG within 10 minutes plus serial high-sensitivity troponin (0-hour/1-hour or 0-hour/3-hour algorithms). Risk-stratify with the GRACE (death) and TIMI (composite endpoint) scores to triage the timing of invasive coronary angiography: immediate (within 2 hours) for very high-risk (haemodynamic instability, life-threatening arrhythmia, mechanical complication, acute heart failure, recurrent dynamic ST-T change), early (within 24 hours) for high risk (GRACE above 140, dynamic ST-T change, troponin rise-fall), and within 72 hours for intermediate risk. Every patient receives immediate dual antiplatelet therapy (aspirin 300 mg load then 75 mg daily plus ticag

Red flags

• Ischaemic chest pain at rest with dynamic ST depression over 0.5 mm or deep T-wave inversion in multiple leads = NSTE-ACS; serial high-sensitivity troponin to separate NSTEMI from unstable angina
• NSTE-ACS with haemodynamic instability, cardiogenic shock, life-threatening arrhythmia, acute heart failure, or recurrent dynamic ST-T change = very high risk; immediate invasive coronary angiography within 2 hours
• A new pansystolic murmur days after an ACS with sudden pulmonary oedema = mechanical complication (papillary muscle rupture, ventricular septal rupture) — urgent echocardiogram and surgery
• Tearing chest/abdominal pain radiating to the back with a pulse or blood-pressure differential between arms = aortic dissection; exclude with CT angiography BEFORE giving any antiplatelet or anticoagulant

High-yield structure examiners expect

Cover: Overview & Definition, Classification, Epidemiology & Risk Factors, Pathophysiology, Clinical Presentation, Differential Diagnosis.

Key doses / thresholds (from topic teaching)

• aspirin 300 mg + ticagrelor 180 mg) + *anticoagulant
• fondaparinux 2.5 mg SC/UFH/enoxaparin/bivalirudin) + **high
• starting at 10 micrograms/min, titrated up to 200 micrograms/
• morphine 2 to 4 mg IV every 5 to 15 minutes** for refracto
• fondaparinux 2.5 mg subcutaneous once daily** (preferred fo
• enoxaparin 1 mg/kg subcutaneous twice daily**, **unfrac

Questions

a) Define the condition and give the most important classification or severity framework used in exams. (3 marks)

• Clear one-line definition matching standard teaching.
• Named classification / stages / types with discriminating features.
• One sentence on why classification changes management.

b) Outline pathophysiology in a mechanism chain that explains the main clinical features. (3 marks)

• Initiating insult → intermediate pathway → end-organ effect.
• Link at least two symptoms/signs to mechanism.
• Mention one complication pathway (e.g. shock, perforation, herniation, arrhythmia).

c) List discriminating clinical features and bedside assessment. (3 marks)

• Classic presentation plus one atypical group (elderly, pregnancy, child, immunocompromised).
• Named signs/manoeuvres if relevant.
• What must never be missed on exam/bedside (pregnancy test, airway, glucose, etc.).

d) Investigations with thresholds and one named score if applicable. (3 marks)

• First-line tests and what positive findings mean.
• Gold-standard or definitive investigation when needed.
• Score components reproduced exactly if a named score is standard for this topic.

e) Immediate resuscitation and definitive management with doses where standard. (3 marks)

• ABC / time-critical steps first.
• First-line drug(s) with agent + dose + route (or procedure steps).
• Escalation triggers (theatre, ICU, thrombolysis window, antidote, etc.).
• Disposition and safety-netting.

Marking tips

Full marks require specificity (numbers, names, doses) not generic "give antibiotics/fluids." Regional practice (ICMR / NICE / AHA) may be cited as alternative where relevant.