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Myocardial Infarction for NP

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Myocardial Infarction for the Nurse Practitioner Licensing Exam
Myocardial infarction (MI), or heart attack, occurs when there is an acute reduction in coronary blood flow, leading to prolonged ischemia and myocardial cell death. MI is commonly due to atherosclerotic plaque rupture, causing thrombus formation and partial or complete coronary artery blockage. MIs are classified as ST-segment elevation MI (STEMI) and non-ST-segment elevation MI (NSTEMI) based on ECG findings.
Pathophysiology
  • Atherosclerosis: Plaque buildup in coronary arteries narrows the vessel lumen, reducing blood flow. Risk factors include smoking, hypertension, hyperlipidemia, diabetes, and obesity.
  • Plaque Rupture and Thrombosis: Plaque rupture activates platelets and the coagulation cascade, leading to thrombus formation. A thrombus can partially or fully occlude a coronary artery.
  • Ischemia and Infarction: Prolonged ischemia causes myocardial cell death. In STEMI, ischemia is usually transmural (full thickness), while NSTEMI typically involves subendocardial ischemia.
Risk Factors
  • Modifiable: Smoking, hypertension, hyperlipidemia, diabetes, obesity, and sedentary lifestyle.
  • Non-Modifiable: Age, race, sex, family history of early CAD. Risk is higher in African Americans than in White Americans. Women have higher mortality than men.
Clinical Presentation
myocardial infarction signs and symptoms
  • Chest Pain: Described as a crushing or squeezing pain in the chest, often radiating to the left arm, neck, jaw, or back. Pain lasts over 20 minutes and may not resolve with rest.
  • Associated Symptoms: Diaphoresis, nausea, vomiting, shortness of breath, and a sense of impending doom.
  • Additional Presentations: Common in women, elderly, and diabetic patients, presenting with symptoms like fatigue, syncope, or abdominal discomfort.
Diagnosis
  • STEMI:
    • ECG: ST-segment elevation in two or more contiguous leads.
    • Biomarkers: Elevated troponins confirm myocardial injury.
  • NSTEMI:
    • ECG: ST depression, T-wave inversion, or nonspecific changes.
    • Biomarkers: Elevated troponins indicate myocardial necrosis.
Management
  • STEMI:
    • Reperfusion Therapy: Primary PCI within 90 minutes is preferred. If PCI is unavailable within 120 minutes, fibrinolysis should be initiated within 30 minutes.
    • Medications: Aspirin, P2Y12 inhibitors (e.g., clopidogrel), heparin, beta-blockers, ACE inhibitors, and statins.
  • NSTEMI:
    • Medications: Dual antiplatelet therapy (aspirin and P2Y12 inhibitor), anticoagulation, beta-blockers, ACE inhibitors, and statins.
    • Risk Stratification: TIMI or GRACE score to guide the timing of PCI.
Key Points
  • Pathophysiology: MI is caused by atherosclerotic plaque rupture and thrombus formation, leading to ischemia and cell death.
  • Types of MI:
    • STEMI: Complete coronary occlusion with ST elevation; requires immediate reperfusion (PCI or fibrinolysis).
    • NSTEMI: Partial occlusion; managed with antithrombotic therapy and risk assessment for PCI.
  • Diagnosis:
    • ECG: ST elevation in STEMI; ST depression or T-wave inversion in NSTEMI.
    • Biomarkers: Elevated troponins confirm myocardial injury.
  • Management:
    • STEMI: Immediate PCI or fibrinolysis.
    • NSTEMI: Antiplatelet therapy, anticoagulation, and PCI for high-risk patients.

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