Myocardial Infarction, acute (AMI) / ST elevation myocardial infarction (STEMI)

I21.0-4/I21.9/I22.0-1/I22.8-9/I24.8-9/I25.6/I25.8-9

DESCRIPTION

AMI/STEMI is caused by the complete or partial occlusion of a coronary artery and requires prompt hospitalisation and intensive care management. The major clinical feature is severe chest pain with the following characteristics:

  • site: retrosternal or epigastric
  • quality: crushing, constricting or burning pain or discomfort
  • radiation: to the neck and/or down the inner part of the left arm
  • duration: at least 20 minutes and often not responding to sublingual nitrates
  • occurrence: at rest

May be associated with:

  • pallor
  • pulmonary oedema
  • sweating
  • a decrease in blood pressure
  • arrhythmias

Note: Not all features have to be present.

EMERGENCY TREATMENT

Before transfer

Cardio-pulmonary resuscitation if necessary (See: Cardiac arrest – cardiopulmonary resuscitation).

  • Oxygen 40% via facemask, if saturation < 94% or if in distress.

LoEI [23]

AND

  • Aspirin, oral, 150 mg as a single dose (chewed or dissolved) as soon as possible.

LoEI [24]

AND

  • Nitrates, short acting, e.g.:
    • Isosorbide dinitrate, sublingual, 5 mg, immediately as a single dose.
      • May be repeated at 5 minute intervals for 3 or 4 doses.

LoEIII [25]

AND

  • Morphine 10mg diluted with 10mL of water for injection or sodium chloride 0.9%, slow IV (Doctor prescribed).
    • Start with 5 mg; thereafter slowly increase by 1 mg/minute up to 10mg.
    • Can be repeated after 4–6 hours if necessary, for pain relief.
    • Beware of hypotension.

AND

  • Thrombolytic, e.g.:(see table for time window below): (Doctor initiated)

LoEI [26]

  • Streptokinase, IV 1.5 million units diluted in 100 mL sodium chloride 0.9%, infused over 30–60 minutes. Do not use heparin if streptokinase is given.
    • Hypotension may occur. If it does, reduce the rate of infusion but strive to complete it in < 60 minutes.
    • Streptokinase is antigenic and should not be re-administered in the period of 5 days to 2 years after 1st administration.
    • Severe allergic reactions are uncommon but antibodies which may render it ineffective may persist for years.

LoEI [27]

Indications Contra-indications
For acute myocardial infarction with ST elevation or left bundle branch block:

  • maximal chest pain is ≤6 hours
  • Beyond 6 hours and chest pain, consult a specialist
    • >6 hours and no chest pain, manage with anticoagulants. See: NSTEMI
  • if on-going ischaemic pain


    • LoEI [28]     		Absolute:
  • streptokinase used within the last year,

  • previous allergy,

  • CVA within the last 3 months,

  • history of recent major trauma,

  • bleeding within the last month,

  • aneurysms,

  • brain or spinal surgery or head injury within the preceding month, or recent (<3 weeks) major surgery,

  • active bleeding or known bleeding disorder.
    • aortic dissection.
    Relative (consult specialist):,
  • refractory hypertension,

  • warfarin therapy,

  • recent retinal laser treatment,

  • subclavian central venous catheter,

  • pregnancy,

  • TIA in the preceding 6 months,

  • traumatic resuscitation.
    		•

    LOEI [28]

    Note: Refer all suspected or diagnosed cases urgently.

    Continuation of aftercare treatment initiated at higher level of care:

    Continue therapy with appropriate lifestyle modification and adherence support.

    • Aspirin, oral, 150 mg daily (continued indefinitely in absence of contraindications).

    LoEI [29]

    If unavailable:

    • Aspirin, oral, 150 mg daily.

    When clinically stable without signs of heart failure, hypotension, bradydysrhythmias or asthma:

    • Cardio-selective beta-blocker, e.g.:(Doctor prescribed)
    • Atenolol, oral, 50 mg daily.
    • HMGCoA reductase inhibitors (statins), e.g.:
    • Simvastatin, oral, 40 mg at night.

    LoEI [30]

    Patients on protease inhibitor:

    • Atorvastatin, oral, 10 mg at night.

    LoEI [31]

    Patients on amlodipine (and not on a protease inhibitor):

    • Simvastatin, oral, 10-20 mg at night.

    LoEIII [32]

    If patient complains of muscle pain:

    Reduce dose to:

    • Simvastatin, oral, 20 mg at night.
      • If 20 mg not tolerated, reduce to 10 mg.

    LoEIII [33]

    OR

    • Refer for further management.

    AND

    If there is cardiac failure or LV dysfunction (Doctor initiated):

    • ACE-inhibitor, e.g.:
    • Enalapril, oral, target dose 10 mg 12 hourly (usually titrated from 2.5 mg 12 hourly).

    LoEIII [34]

    Angioedema is a potentially serious complication of ACE-inhibitor treatment and if it occurs it is a contraindication to continued therapy or to re-challenge.

    REFERRAL

    Urgent

    All suspected or diagnosed cases.