Myocardial infarction is death of cardiac myocytes (necrosis) caused by prolonged ischemia. The term acute "usually" refers to the time 6 hours to 7 days following pathologic appearance of the infarct.
The patient may experience ischemic-type chest discomfort with accompanying symptoms of nausea, vomiting, dyspnea, diaphoresis, lightheadedness, dizziness, syncope, fatigue and weakness.
Rapid diagnosis and risk stratification of chest pain patients is important to identify acute myocardial infarction patients who will benefit from reperfusion therapy.
Ideally, patient diagnosed with myocardial infarction should begin treatment within 30 minutes of arrival to hospital.


Acute Myocardial Infarction (AMI)

  • Myocardial infarction is death of cardiac myocytes (necrosis) caused by prolonged ischemia
  • The term “acute” usually refers to the time 6 hours - 7 days following pathologic appearance of the infarct

Signs and Symptoms

The patient may experience ischemic-type chest discomfort with the following characteristics:

  • Retrosternal/substernal chest pain lasting 10-20 minutes or longer
    • Pain is usually described as heaviness, pressure or burning in nature
    • Pain may occur at rest or during activity and does not respond fully to Glyceryl trinitrate (GTN)
  • The pain which is usually central or in the left chest may radiate to the jaw, neck, left arm, back or shoulder
  • Discomfort is diffuse, not localized, positional nor affected by movement of the region
  • Occasionally, symptoms are mistaken for indigestion or heartburn if pain occurs in the epigastric region
  • Accompanying symptoms may include nausea, vomiting, dyspnea, diaphoresis, lightheadedness, dizziness, syncope, fatigue and weakness
  • Atypical pattern may occur especially in females, diabetics and elderly patients; the pain develops in the arm, shoulder, wrist, jaw or back without occurring in the chest
  • MI should be suspected especially if the symptoms are severe and occur suddenly
  • MI may present with autonomic nervous system activation (eg pallor, sweating), hypotension or narrow pulse pressure, bradycardia or tachycardia, 3rd heart sound (S3), basal rales

Risk Factors

  • Identifying patients who are at increased risk of further reinfarction or death is essential in order that it can be prevented or intervention be done accordingly

High-Risk Patients

  • Left ventricular ejection fraction (LVEF) <35% ischemia that affects >50% of viable myocardium
  • Clinical indicators include:
    • Advanced age
    • Hypotension
    • Anterior infarction
    • Elevated initial serum creatinine
    • Malignant arrhythmias
    • Early angina on minimal exertion
    • Tachycardia
    • Killip class >1
    • Previous infarction
    • Heart failure history
    • Persistent chest pain

Medium-Risk Patients

  • Patients not considered low risk or high risk based on imaging criteria should be treated based on symptomatic status

Low-Risk Patients

  • LVEF >50% or mild inducible ischemia that affects <20% of viable myocardium

Patient Instructions

  • The patient should carry out previous instructions on medications to be taken in case of a possible myocardial infarction (MI):

Glyceryl Trinitrate (GTN)

  • Should take one dose of sublingual GTN
  • Contraindicated in patients with hypotension and or have taken phosphodiesterase 5 inhibitor within 24 hours
  • If symptoms do not subside, seek emergency medical treatment


  • If patient is not on regular Aspirin and is not allergic, it is recommended that he chew and swallow 162-325 mg of Aspirin
  • Enteric-coated form should not be used because of its slow onset of action
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