Myocardial Infarction (MI)

• Definition: Partial or complete occlusion of one or more of the coronary arteries (a.k.a. heart attack).
• Pathophysiology: Coronary artery occlusion deprives the myocardium (muscle tissue of heart) of O₂ and blood. Subsequent death of myocardial tissue occurs.
• Etiology: Thrombus (clot) occludes an artery in 90% of cases. CAD, hemorrhage, coronary artery spasm, hypoxia, inflammation from disease, severe exertion or stress in the presence of significant CAD.
• Manifestations: Severe and persistent pain (pain does not subside with rest or nitrates). Crushing or squeezing sensation in center of chest behind sternum. Pain may radiate or be localized to the shoulder, neck, arm, back, teeth, jaw, or fourth and fifth fingers of the left hand. N/V, sweating, SOB, pale or ashen color. 15 to 20% of MIs are painless. ECG: dysrhythmias; T-wave inversion; ST segment elevation; pathologic, deep Q wave. Lab: Elevated troponin, CK-MB, LDH.
  NOTE: Validity of lab results is dependent on proper timing of specimen collections. Refer to specific test in Laboratory Tests later in this section.
• Med Tx: Medical care should be instituted without delay. Hemodynamic and ECG monitoring, O₂, bed rest, analgesics, nitroglycerin, antiarrhythmics, thrombolytics, tissue plasminogen activator, PTCA, or surgical intervention.
• Nsg Dx: Alteration in tissue perfusion (cardiac), pain, potential alteration in cardiac output (decreased), activity intolerance, knowledge deficit, anxiety.
• Nsg Care: Promote rest and calm, quiet environment. Assist with ADL. Monitor VS and hemodynamic parameters and response to medical regimen. Provide information including rehabilitation teaching.
• Prognosis: Mortality rate is 30 to 40% with over half of the deaths occurring within the first hour after onset of symptoms and prior to arrival at an acute care facility.