Background Information

Definitions

ACS is the acute manifestation of coronary artery disease. This umbrella term includes the spectrum of STEMI , NSTEMI , and unstable angina. ^[Ref]

Risk Factors

Major risk factors: ^[Ref]

• Age (>65 y/o)
• Male
• Cardiovascular risk factors
• Family history of premature coronary artery disease
• Presence of other cardiovascular diseases
• Established coronary artery disease (e.g. previous MI, coronary revascularisation)

Other risk factors: ^[Ref]

• CKD
• Chronic inflammatory conditions (e.g. rheumatoid arthritis, SLE)
• Premature menopause
• Pregnancy-related complications (e.g. pre-eclampsia, gestational diabetes)

Complications

Complications of MI can be organised by the time frame after the event: ^{[Ref1, Ref2]}

Diagnosis

Clinical Features

Chest pain / discomfort is the main presenting feature of ACS, it can be mapped to the SOCRATES framework: ^[Ref]

• Site: central or retrosternal (typically non-specific)
• Onset: sudden onset, usually at rest
• Character: heavy / crushing / tightness
• Radiation: classically to the left arm, neck, jaw
• Associated symptoms: dyspnoea, nausea, vomiting, diaphoresis
• Timing: often lasts >15 min and does not resolve spontaneously
• Exacerbating factors: often precipitated by exertion or emotional stress but may occur at rest (ACS symptoms is characteristically not relieved by rest and nitrate)
• Severity: can be severe

Referral and Initial Assessment

Referral Criteria

This mainly applies to those who present to a non-hospital setting (e.g. GP, health centre)

There are 2 main referral scenarios:

Initial Assessment

Apart from a detailed clinical history and examination, perform ALL the following in suspected ACS cases:

• 12-lead ECG – most immediate test to perform (followed by serial ECGs)
• High-sensitivity cardiac troponin T/I (followed by serial samples)

• Other tests (non-ACS specific, but are routinely performed in patients with chest pain)
  • Chest X-ray – to rule out chest pathology and ACS complications
  • Routine bloods (including FBC, LFT, renal function, blood glucose)

Diagnostic Criteria

Diagnostic criteria of ACS: ^[Ref]

Troponin Interpretation

Rise and/or fall of cardiac troponin is indicative of myocardial infarction (STEMI and NSTEMI) (but not unstable angina, as there is no necrosis) ^[Ref]

• Troponin is a marker of myocardial injury, not specific to MI
• Necrosis in STEMI and NSTEMI causes a dynamic release of troponin, thus the rise and/or fall pattern
• A persistently raised troponin level is NOT indicative of ACS

Important non-ACS causes of elevated troponin: ^[Ref]

ECG Interpretation

STEMI

Dynamic ECG changes seen in STEMI: ^[Ref]

• ST elevation in ≥2 contiguous leads
• Reciprocal ST depression in opposite territory – presence strengthens diagnosis of STEMI as opposed to other causes of ST elevation
• Hyperacute T waves, T wave inversion, pathological Q wave

ECG changes in various myocardial territories: ^[Ref]

Other important causes of ST elevation:

NSTEMI and Unstable Angina

Main changes include: ^[Ref]

• Normal ECG
• ST depression (horizontal / down-sloping)
• T wave inversion

Management

Immediate Management

Once ACS is suspected based on clinical suspicion, the following should be started ASAP (often given at pre-hospital):

• Aspirin 300mg
• Pain relief
  • GTN (sublingual /buccal) – should be avoided in suspected right ventricular infarction (e.g. inferior MI)
  • IV morphine (esp. if MI is suspected)
• Oxygen therapy (only if SpO₂ <94%, or <88% in those who are at risk of type 2 respiratory failure)

Definitive Management

There are 2 management pathways – depending on whether it is STEMI or non-STEMI (i.e. NSTEMI and unstable angina):

• STEMI pathway – 2 options
  • Reperfusion therapy (PCI / fibrinolysis)
  • Medical management

• NSTEMI / unstable angina pathway – 2 options (depending on risk stratification)
  • PCI
  • Medical management

STEMI Management Algorithm

Initial management: aspirin 300mg (if not already given as part of immediate management)

Definitive management depends on eligibility for reperfusion therapy, which is determined by time from symptom onset – cut-off is 12 hours.

Symptom Onset <12 hours → Reperfusion Therapy

There are 2 options for reperfusion therapy:

• Angiography +/- percutaneous coronary intervention (PCI)
• Fibrinolysis (medical)

The choice is determined by whether there is access to PCI within 120 min (2 hours).

NICE guidelines also made the following recommendations regarding PCI:

• Offer if symptoms onset <12 hours with acute STEMI + cardiogenic shock
• Consider if onset >12 hours with evidence of MI
• Consider if onset >12 hours but develops cardiogenic shock

Access Within 120 min → Angiography +/- PCI

Recommendations regarding angiography +/- PCI:

• Drug-eluting stent preferred over bare metal stent, if stenting indicated
• Radial access is preferred over femoral access

Adjuvant drug therapy:

• Dual antiplatelet therapy
  • 1st line: aspirin + prasugrel 
  • If patient already takes oral anticoagulant: aspirin + clopidogrel

• Anti-thrombin therapy during PCI
  • Radical access: UFH + bailout GpIIb/IIIa inhibitor
  • Femoral access: bivalirudin + bailout GpIIb/IIIa inhibitor

No Access Within 120 min → Fibrinolysis

Offer all the following:

• Fibrinolytic agent: tissue plasminogen activator (e.g. alteplase, streptokinase)
• Anti-thrombin 
• Dual antiplatelet therapy
  • 1^st line: aspirin + ticagrelor
  • High bleeding risk: aspirin + clopidogrel OR aspirin monotherapy

Then, offer ECG 60-90 minutes after:

• If ST elevation still present on ECG → immediate angiography +/- PCI if indicated
• Do not repeat fibrinolytic therapy

Symptom Onset >12 hours → Medical Management

Dual antiplatelet therapy

• 1^st line: aspirin + ticagrelor
• High bleeding risk: aspirin + clopidogrel OR aspirin monotherapy

Tests Before Discharge

Offer echocardiogram to assess left ventricular function in all patients who had a STEMI.

NSTEMI / Unstable Angina Management Algorithm

Initial management (both):

• Aspirin 300mg (if not already given as part of immediate management)
• Antithrombin therapy
  • 1st line: fondaparinux
  • If high bleeding risk / renal impairment (creatinine >265 mmol/L) / immediate angiography planned: UFH

Definitive management depends on risk stratification with GRACE score (predicts 6-month mortality).

GRACE >3.0% (intermediate / high / highest)

Offer all of the following:

• Angiography +/- PCI within 72 hours
• UFH, even if fondaparinux has been given
• Dual antiplatelet therapy
  • 1st line: aspirin + prasugrel / ticagrelor
  • Already taking oral anticoagulant: aspirin + clopidogrel

Recommendations regarding angiography +/- PCI:

• Drug-eluting stent, if stenting indicated
• Radial access, preferred over femoral access

GRACE ≤3.0% (low / lowest)

Medical management with dual antiplatelet therapy:

• 1^st line: aspirin + ticagrelor
• High bleeding risk: aspirin + clopidogrel OR aspirin monotherapy

Only consider angiography +/- PCI if ischaemia testing is positive

Tests Before Discharge

• Offer echocardiogram to assess left ventricular function
  • In all NSTEMI cases
  • Consider in unstable angina

• Consider ischaemia testing in those who have been medically managed without coronary angiography

Choice of Dual Antiplatelet Therapy in ACS

ACS Secondary Prevention Guidelines

Conservative Management

• Cardiac rehabilitation program
• Lifestyle advice
  • Mediterranean-style diet
  • Regular physical activity
  • Smoking cessation
  • Advice on alcohol consumption
  • Weight management
  • Sexual activity can be resumed 4 weeks after

NICE guideline recommendations regarding various supplements:

Pharmacological Management

Offer ALL the following to ALL patients:

• Dual antiplatelet therapy
  • Aspirin lifelong (if aspirin not appropriate → clopidogrel)
  • 2nd antiplatelet agent for up to 12 months
• High-intensity statin (e.g. atorvastatin 80mg) life-long
• ACE inhibitor for life-long – start once hemodynamically stable
• Beta blocker for 12 months if normal LVEF – start once hemodynamically stable

Add-on if there are heart failure features and ↓ LVEF

• Aldosterone antagonist (e.g. spironolactone) – initiate within 3-14 days of MI, preferably after starting ACE inhibitor

References

NICE Visual Summary – STEMI Management

NICE Visual Summary – NSTEMI and Unstable Angina

NICE Visual Summary – Secondary Prevention

Original Guidelines