Myocardial Infarction

Myocardial infarction (Table 5) is caused by abrupt anoxia to a portion of the heart resulting in myocardial tissue necrosis. Anoxia results from conditions that lead to the formation of atherosclerotic plaques. In later stages, atherosclerotic plaques may become disrupted and contribute to thrombus formation. Atherosclerotic plaques and thrombi impair blood flow to large and medium-sized arteries of the heart. History of cardiovascular diseases, diabetes mellitus, and cerebrovascular disease increases the overall risk of perioperative MI.

Table 5. Myocardial Infarction.

Prevention:
  • Identify at-risk patient
    • Reduce anxiety
    • Ensure profound local anesthesia
      • Use local anesthetic agents containing a vasoconstrictor congruent with the patient’s functional capacity
Signs and symptoms:
  • Severe substernal chest pain lasting longer than 3 to 5 minutes
    • Radiates to the arms, neck, shoulders, or jaw
  • Weakness, dizziness, light-headedness
  • Nausea and/or vomiting
  • Dyspnea, tachypnea, or apnea
  • Pale or ashen skin (especially around the face)
  • Diaphoresis
    • Cool, clammy skin
  • Hypotension
    • Systolic blood pressure <90 mm Hg
  • Tachycardia (over 100 beats/minute)
    • Palpitation
Emergency response:
  • Place patient in an upright or semi-reclining position
    • Activate EMS
      • Administer oxygen
        • 6 L/min by nasal cannula
      • Encourage patient to chew an adult aspirin, 325 mg, unless otherwise contraindicated
      • Monitor vital signs
        • If at any time the patient becomes unresponsive, no normal breathing, and no palpable pulse consider the diagnosis of cardiac arrest
          • Immediate CPR and defibrillation congruent with current recommendations
Nota bene:
  • Signs of recovery: pain is subsiding, vital signs returning to baseline values
  • Signs of deterioration: pain persists, vital signs unstable, altered mentation (loss of consciousness)
  • Signs and symptoms of MI vary from mild, vague discomfort to cardiogenic shock with an overall mortality rate to greater than 80%
  • Patient denial may minimize symptoms and elderly and diabetic patients have a higher incidence of silent MI characterized by vague symptoms of shortness of breath, epigastric distress, hypotension, and altered mental state
  • More than 60 days should elapse after a MI before elective noncardiac procedures, e.g., elective dental care
  • Recent MI, defined as having occurred within 6 months of noncardiac surgery, is an independent risk factor for perioperative stroke