PassFinals
Cardiovascular

Unstable Angina

Unstable angina is acute coronary ischaemia that causes rest or crescendo pain but stops short of killing myocytes, so troponin never rises and falls diagnostically.

In a nutshell

Unstable angina is acute coronary ischaemia with no acute myocardial injury: no rise and fall of high-sensitivity troponin above the 99th-percentile limit. Treat the acute phase exactly as a non-ST-elevation myocardial infarction (NSTEMI): aspirin 300 mg chewed, then fondaparinux 2.5 mg subcutaneously once daily.

Classic presentation

Crescendo chest pain now coming on at rest and lasting 20 minutes, with transient ST depression during pain, and two high-sensitivity troponins that do not move.

Key points

  • Troponin is one input to the risk score, alongside age, blood pressure, heart rate, the ECG, creatinine, glucose and haemoglobin.
  • Risk bands from predicted 6-month mortality: 1.5% or below lowest, above 1.5% to 3.0% low, above 3.0% to 6.0% intermediate, above 6.0% to 9.0% high, over 9.0% highest.
  • The diagnosis is a pattern: rest pain over 15 minutes, new severe angina, or previously stable angina now more frequent and provoked by less.
  • Stable angina is three features: constricting front-of-chest, neck, jaw or arm discomfort, brought on by exertion, relieved by rest or glyceryl trinitrate within about 5 minutes.
  • A detectable troponin on the first high-sensitivity test does not mean the person has had an infarct, and patients should be told so.
  • Before blaming a raised troponin on ACS, exclude myocarditis, aortic dissection and pulmonary embolism as causes of the rise.

First-line investigation

Resting 12-lead ECG plus high-sensitivity troponin on arrival, repeated on the schedule validated for that assay. A normal ECG and a flat troponin do not exclude acute coronary syndrome (ACS).

Management

Treat as ACS until the troponin reports

  • Monitored bed, continuous ECG, pulse oximetry, resting 12-lead ECG as soon as possible. Aspirin 300 mg once, chewed or dispersed in water.1,3,6
  • Oxygen only if SpO2 is below 94%: target 94% to 98%, or 88% to 92% if at risk of hypercapnic respiratory failure.1
  • Glyceryl trinitrate (GTN) sublingual: 1 to 2 sprays of 400 micrograms, or one 500 or 600 microgram tablet, repeat at 5 minutes, maximum 3 doses.1,7
  • Ongoing pain: morphine 5 to 10 mg by slow intravenous injection at 1 to 2 mg/minute, or 2.5 to 5 mg if frail or elderly.1,8
  • No second antiplatelet until unstable angina or NSTEMI has actually been diagnosed.3

Confirmed: identical to NSTEMI

  • Fondaparinux 2.5 mg subcutaneously once daily, up to 8 days or until discharge, unless bleeding risk is high or immediate angiography is planned.3,9
  • Creatinine above 265 micromoles per litre: unfractionated heparin instead, 5000 units intravenously then 18 units/kg/hour, adjusted by clotting monitoring.3,10
  • Avoid fondaparinux if creatinine clearance is below 20 mL/minute. Weigh age, bleeding history, renal impairment and low body weight before choosing either.3,9
  • Then score predicted 6-month mortality with GRACE (Global Registry of Acute Cardiac Events), which decides whether and how fast to do coronary angiography.3
  • Anyone going to percutaneous coronary intervention (PCI) also gets systemic unfractionated heparin in the catheter laboratory, whether or not fondaparinux was given.3,10

Timing the angiography

  • Clinically unstable: immediate coronary angiography, whatever the score says.3
  • Above 3.0% predicted 6-month mortality: consider angiography with follow-on PCI within 72 hours of first admission.3
  • 3.0% or less: consider conservative management without early angiography, and arrange angiography if ischaemia recurs or is demonstrated by testing.3
  • A young person with a low 6-month mortality score can still be high risk and may benefit from early angiography.3

Second antiplatelet and revascularisation

  • Having angiography, not anticoagulated: ticagrelor 180 mg then 90 mg twice daily. Or prasugrel 60 mg at PCI then 10 mg daily, 5 mg if under 60 kg or 75 and over.3,11,12
  • Already on an anticoagulant: clopidogrel 300 mg then 75 mg once daily. PCI not indicated: ticagrelor, or clopidogrel or aspirin alone at high bleeding risk.3,13,11
  • Ticagrelor here needs ischaemic ST or T-wave change plus one high-risk feature, and the diagnosis confirmed, ideally by a cardiologist, to continue past initial treatment.4
  • Choose PCI or coronary artery bypass grafting (CABG) on anatomy, comorbidity and procedural risk, with multidisciplinary discussion when the strategy is unclear.3

Before discharge, and what not to start

  • Managed conservatively without angiography: consider ischaemia testing before discharge. Consider assessing left ventricular function, deliberately weaker than the "assess" that follows an NSTEMI.3
  • Atorvastatin 80 mg once daily started without delay; a lower dose for interactions, adverse-effect risk or patient preference. Full lipid profile on admission and at 2 to 3 months.5,14
  • Target LDL cholesterol 2.0 mmol/litre or less, or non-HDL cholesterol 2.6 mmol/litre or less. Aspirin 75 mg once daily indefinitely.5,3,6
  • No automatic angiotensin-converting enzyme (ACE) inhibitor or beta-blocker: prescribe either only for a separate indication such as hypertension, heart failure or angina control.3

Exam traps

  • Response to glyceryl trinitrate does not make the diagnosis. CG95 recommendation 1.2.1.4 says so explicitly, and oesophageal pain also settles.
  • Unstable angina is not a synonym for troponin-negative chest pain. Without a convincing ischaemic history or ECG, reassess for stable angina or a non-cardiac cause.
  • NG185's secondary-prevention drugs (section 1.4) and cardiac rehabilitation (section 1.8) are written for after an MI, so neither is automatic after unstable angina.
  • Left ventricular assessment is "assess" after an NSTEMI (recommendation 1.2.27) but only "consider" in unstable angina (1.2.28). The wording is deliberate.
  • Fibrinolysis has no role in unstable angina or NSTEMI. It is a STEMI option only, and only when timely primary PCI is unavailable.
  • CT coronary angiography belongs to the stable pathway. NICE says not to routinely offer non-invasive imaging or exercise ECG in the initial assessment of acute chest pain.
  • The 300 mg aspirin is a single loading dose. Maintenance is 75 mg once daily, continued indefinitely.

Key sources

  1. NICE, Recent-onset chest pain of suspected cardiac origin: assessment and diagnosis (CG95)Published 24 Mar 2010 | Updated 30 Nov 2016
  2. NICE, High-sensitivity troponin tests for the early rule out of NSTEMI (HealthTech guidance, replaces DG15 and DG40) (HTG552)Published 26 Aug 2020
  3. NICE, Acute coronary syndromes (NG185)Published 18 Nov 2020
  4. NICE, Ticagrelor for the treatment of acute coronary syndromes (TA236)Published 26 Oct 2011
  5. NICE, Cardiovascular disease: risk assessment and reduction, including lipid modification (NG238)Published 14 Dec 2023
  6. BNF, Aspirin (BNF drug monograph)
  7. BNF, Glyceryl trinitrate (BNF drug monograph)
  8. BNF, Morphine (BNF drug monograph)
  9. BNF, Fondaparinux sodium (BNF drug monograph)
  10. BNF, Heparin (unfractionated) (BNF drug monograph)
  11. BNF, Ticagrelor (BNF drug monograph)
  12. BNF, Prasugrel (BNF drug monograph)
  13. BNF, Clopidogrel (BNF drug monograph)
  14. BNF, Atorvastatin (BNF drug monograph)

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.