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

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

• 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

• 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

Aspirin

• 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