• Use this guideline only in patients where the most likely diagnosis is acute myocardial infarction
• To check you are using the correct guideline, use Assessment of chest pain suspected to be cardiac in origin guideline

Symptoms and signs

• Severe, persistent chest pain
• Dyspnoea
• Fear
• Pallor
• Sweating
• Anxiety
• Peripheral vasoconstriction
• Shock

Investigations

• ECG (see below)
• Locally available cardiac biomarkers of myocardial injury
• Raised cardiac biomarkers signify myocardial infarction, not unstable angina
• A raised troponin I concentration can suggest myocardial necrosis but can also occur in a number of other conditions:
  • auto-immune disease
  • congestive cardiac failure
  • critical illness
  • dilated cardiomyopathy
  • extreme physical effort
  • hypertension
  • hypothyroidism
  • multiple injury
  • myocarditis
  • pericarditis
  • pneumonia
  • pulmonary embolism
  • renal failure
  • sepsis/septic shock
  • subarachnoid haemorrhage
  • tachyarrythmias
  • vasculitis
• Plasma cholesterol profile (within 12 hr of onset of symptoms; otherwise leave for at least 6 weeks)
• Venous blood glucose and HbA_1c
• FBC, INR, APTT

• Aspirin 300 mg (chew and swallow)
• Diamorphine 1 mg/min IV until pain relieved, up to maximum 10 mg (5 mg in elderly or frail patients)
• Metoclopramide 10 mg IV over 1-2 min (5 mg <60 kg) with ≥8 hr before repeating
• Oxygen - see Hypoxaemia guideline
• Bisoprolol 2.5 mg oral daily, unless contraindicated (e.g. decompensated heart failure, bradycardia)
• Unless history of CKD present, atorvastatin 80 mg once daily for all acute coronary syndromes. If history of CK, start with atorvastatin 20 mg once daily

Admission

• Admit all patients with acute myocardial infarction (MI), or unstable angina with acute ST depression and/or raised troponin I to CCU under the care of duty consultant cardiologist. Contact on-call cardiology SpR immediately for immediate transfer and treatment
•  If ECG shows ST elevation MI (STEMI), follow Management of STEMI below
  
  • ≥2.5 mm in men aged <40 yr
  • ≥2 mm in men aged ≥40 yr
  • ≥1.5 mm in women regardless of age
• If patient has a Non-ST elevation MI (NSTEMI), follow Management of NSTEMI below

• Administer loading dose of aspirin (300 mg oral) if not already given
• Immediately administer prasugrel (contraindicated in stroke/TIA) and not taking oral anticoagulant
  
  • if aged <75 yr, weight <60 kg, then load with 60 mg and then 5 mg daily for 1 yr
  • if aged <75 yr, weight >60 kg, then load with 60 mg and then 10 mg daily for 1 yr
  • if aged ≥75 yr, then load with 60 mg and then 5 mg daily for 1 yr
  • if prasugrel not suitable (stroke/TIA or aged ≥75 yr and increased risk of bleeding) use clopidogrel 600 mg oral (unlicensed loading dose) 
• Refer to cardiology for primary angioplasty (pPCI), the national default strategy for STEMI management
• If transportation time to a pPCI ready hospital is likely to be >2 hr, then consider thrombolysis, and follow Thrombolytic therapy (STEMI), and immediate transportation to a pPCI centre thereafter
  
  • if decision is not for primary angioplasty, only give thrombolytic therapy if directed by on-call cardiology service - then follow Thrombolytic therapy (STEMI) guideline. Usually, a contraindication for primary angioplasty is a contraindication for thrombolysis

• Treatment of choice for most patients for NSTEMI is early (within 72 hr) inpatient cardiac catheterisation with early revascularisation, either by percutaneous intervention (PCI) or coronary artery bypass graft (CABG)
  
  • patients unlikely to be suitable for an early invasive strategy because of frailty or multiple comorbidities should have that decision made early and by an experienced clinician
• Prescribe fondaparinux 2.5 mg once daily by SC injection 
• Antiplatelet therapy has changed since 2020
• If patient has an NSTEMI, but is likely to go through an invasive angiographic assessment early, then aspirin alone is administered
• Dual antiplatelet therapy decisions will be made in the catheter laboratory
• If an invasive strategy may be delayed then give clopidogrel loading dose 600 mg oral and 75 mg daily
• Risk of bleeding is increased in patients with low body weight (<50 kg), physiological frailty, severe liver (bilirubin >2 x upper limit of normal and AST/ALT/alk phos >3 x upper limit of normal) or renal failure (eGFR <20 mL/min, or serum creatinine ≥ 200µmol/L), alcohol abuse, thrombocytopenia or defective platelet function or impaired clotting, anaemia and following surgery, trauma or haemorrhagic stroke
  
  • seek advice from appropriate team (e.g. cardiology, renal, liver or haematology)

• On admission, check blood glucose/HbA_1c and, if blood glucose is >11 mmol/L, commence variable rate insulin infusion (VRII) - see Hyperglycaemia: can’t eat/drink guideline. In patients with diabetes/raised blood glucose, seek advice from endocrinologist/diabetes nurse specialist early 

• Aspirin 75 mg oral daily (to be continued indefinitely) plus:
  
  • if STEMI and treated by pPCI with no history of CVA or TIA, then either prasugrel or clopidogrel may be appropriate 
  • otherwise clopidogrel 75 mg oral daily for 1 yr 
• For prasugrel
  
  • if aged <75 yr, weight <60 kg, then maintenance dose 5 mg daily for 1 yr
  • if aged <75 yr, weight >60 kg, then maintenance dose 10 mg daily for 1 yr
  • if aged >75 yr, then maintenance dose 5 mg daily for 1 yr
• Bisoprolol 2.5 mg oral daily, or atenolol 25 mg 12-hrly (to be titrated to target heart rate of 60 bpm and continued indefinitely)
• If no clinical suspicion of significant mitral/aortic stenosis or hypertrophic cardiomyopathy, plasma creatinine <300 μmol/L and there is no other contraindication to using ACE inhibitor, start ramipril - see Ramipril guideline. Check electrolytes on day 3-5. Increase titration rapidly to achieve a dose on discharge as near to 10 mg as achievable
• Check statin (atorvastatin 80mg) has been prescribed, target LDL to ≤2.0 mmol/L or non-HDL cholesterol to ≤2.6 mmol/L, subject to renal function (see above)
  
  • give patient information sheet 
• If pain persists, consider glyceryl trinitrate (GTN) infusion - see Glyceryl trinitrate guideline or further dose of atenolol 5 mg IV if heart rate >70 bpm and systolic BP >100 mmHg
• If pain persists, contact duty cardiology team to facilitate transfer to ward/CCU
• Unless complications ensue, recommend early return to physical activity:
  
  • mobilisation depends on revascularisation strategy, with early mobilisation and discharge by day 3 the norm post STEMI managed with an early invasive strategy
• Refer all patients to rehabilitation co-ordinator, who will arrange for assessment of all suitable patients by cardiac rehabilitation team as soon as practically possible after discharge
  
  • patients not wishing to join rehabilitation programme - provide appropriate dietary advice
• Refer all patients treated with glucose and insulin infusions to diabetes nurse specialist to distinguish diabetes from stress-induced hyperglycaemia

• Continuous ECG monitoring for 24-48 hr (longer if continuing instability or arrhythmia)
• Measure BP 4-hrly for 24 hr, then twice daily
• Daily 12-lead ECG. Plasma troponin I next day, as peak troponin indicates infarct size
• Observe for specific complications (more likely to occur if patient not re-perfused)

Specific complications

• In all complications, seek further cardiological input

Arrhythmias

• See Cardiac arrhythmias

Pericarditis

• More likely after large or late presenting infarcts 
• Positional pain with persistent/intermittent pericardial rub 2-5 days after infarction 
• Adequate analgesia (may need diamorphine). Give colchicine 500 microgram 12-hrly (500 mg once daily <70 kg) (unlicensed) if no contraindication 

Recurrent ischaemic pain

• Isosorbide mononitrate SR oral (GTN infusion if necessary - see Glyceryl trinitrate guideline
• If persistent chest pain occurs, refer to duty cardiology team for consideration of inpatient stress testing, coronary angiography and possible inpatient revascularisation
• If re-infarction occurs during admission, contact duty cardiology team immediately

Cardiac failure

• In patients with left ventricular failure (LVF) or impaired LV function, introduce an ACE inhibitor as soon as this is practical - see Acute heart failure guideline
• In patients with significant LVF and/or anterior infarct, arrange echocardiogram as inpatient, to document LV function and exclude LV aneurysm and/or thrombus

• If no complications, discharge home on day 3 (72 hr post admission)
• Check risk factors for recurrent MI (e.g. smoking, hyperlipidaemia, hypertension, obesity) and advise or treat accordingly (mortality in first 2 years is doubled in those who continue to smoke and is 3.5-times greater if total cholesterol >6.5 mmol/L)
• Explain graded return to full activity (see advice booklet)
• Where appropriate, ensure patient has climbed stairs to assess for chest pain/shortness of breath
• Ensure advice booklet and chest pain alert card have been issued
• If taking atorvastatin, ensure GP letter regarding intensive statin therapy accompanies patient on discharge
• Warn about post-infarct angina
• Ensure GTN 400 microgram spray for sublingual use has been prescribed TTO and patient has been counselled on use
• Advise not to drive as per DVLA rules and check with insurer (Group 2 drivers must notify DVLA, taxi drivers must notify local council)
• Ensure referral has been made to cardiac rehabilitation team
• Check that rehabilitation plan has been made
• middle grade in cardiology will be able to review patients who attend as an outpatient at cardiac rehabilitation. Rehabilitation co-ordinator will arrange
• if patient declines cardiac rehabilitation or is unsuitable for programme, refer to cardiology follow-up clinic
• Check that follow-up has been arranged in diabetic clinic for all patients treated with glucose and insulin infusions

Follow-up clinic visit

• Ask about smoking, exercise and weight reduction
• Ask about angina - if occurring, consider referral for further cardiology assessment
• Look for signs of heart failure and measure BP
• Check cholesterol (target LDL to ≤2.0 mmol/L or non-HDL cholesterol to ≤2.6 mmol/L)
• If patient has not been to catheter laboratory, consider treadmill exercise if symptomatic
• Encourage return to work 1 month after infarction
• Resume driving 1 month after infarction (except Group 2 drivers), unless qualifies for a 1 week DVLA driving ban (normal LV function, single vessel disease, treated by PCI)
• Unless there are contraindications, all patients should be taking the following treatment

STEMI

• ACE inhibitor (target dose ramipril 10 mg or equivalent)
• Statin therapy (target dose atorvastatin 80 mg or equivalent, target LDL to ≤2.0 mmol/L or non-HDL cholesterol to ≤2.6 mmol/L,unless history of CKD)
• Beta-blocker (target dose to achieve heart rate of 60 bpm at rest)
• Aspirin (75 mg) indefinitely
• If STEMI and treated by PCI, prasugrel or clopidogrel 75 mg oral daily for 1 yr, as per cardiac catheter laboratory instruction. Prasugrel maintenance dose guided by weight and age (5 or 10 mg daily)

NSTEMI

• ACE inhibitor (target dose ramipril 10 mg or equivalent)
• Statin therapy (target dose atorvastatin 80 mg or equivalent, unless history of CKD)
• Beta-blocker (target dose to achieve heart rate of 60 bpm at rest)
• Antiplatelet therapy aspirin (75 mg) indefinitely, prasugrel or clopidogrel 75 mg oral daily for 1 yr, as per cardiology instruction. Prasugrel maintenance dose guided by weight and age (5 or 10 mg daily)