Myocardial Infarction (MI)
作者：jasper onuohaeke
1. Risk Factors
1.1. Non-modifiable: Age (increased risk with age). Male gender or postmenopausal women. Family history of coronary artery disease. Modifiable: Smoking. Hypertension. Dyslipidemia (elevated LDL, low HDL). Diabetes mellitus. Obesity. Sedentary lifestyle. Stress. (McCance & Huether, 2019, Chapter 33)
2. Pathophysiology:
2.1. Myocardial infarction occurs when blood flow to a portion of the heart muscle is blocked, usually by a thrombus formed due to plaque rupture in coronary arteries. This leads to ischemia and cell death (necrosis) within the affected myocardium. Key mechanisms: Atherosclerosis → Plaque rupture → Platelet aggregation → Thrombus formation. Imbalance between oxygen supply and demand. (McCance & Huether, 2019, Chapter 33)
2.2. Etiology: Coronary artery disease (primary cause). Vasospasm. Coronary embolism. Other rare causes: vasculitis, trauma, or coronary artery anomalies. (McCance & Huether, 2019, Chapter 33)
3. Treatment Options
3.1. Immediate Management: Oxygen (if hypoxic). Nitroglycerin (to relieve pain and improve perfusion). Aspirin (to prevent further clot formation). Morphine (for pain unresponsive to nitroglycerin)
4. Medications:
4.1. Antiplatelets (e.g., clopidogrel). Anticoagulants (e.g., heparin). Beta-blockers (reduce heart workload). ACE inhibitors/ARBs (to manage blood pressure). Statins (to stabilize plaque).
4.1.1. Procedures: Percutaneous coronary intervention (PCI) or stenting. Coronary artery bypass grafting (CABG) for severe cases.
5. Signs and Symptoms
5.1. Chest pain: Pressure, heaviness, or tightness, often radiating to the arm, neck, or jaw. Shortness of breath. Diaphoresis (sweating). Nausea and vomiting. Dizziness or lightheadedness. Fatigue (especially in women or older adults). (McCance & Huether, 2019, Chapter 33)
6. Impact on Other Body Systems & Possible Complications
6.1. Cardiovascular: Heart failure. Arrhythmias (ventricular fibrillation, atrial fibrillation). Cardiogenic shock.
6.1.1. Renal: Acute kidney injury due to reduced perfusion.
6.1.2. Other complications: Ventricular aneurysm. Pericarditis (inflammatory response). (McCance & Huether, 2019, Chapter 33)
6.2. Stroke or transient ischemic attack (from embolism).
7. Diagnostic Tests/Labs
7.1. Laboratory Tests: Cardiac biomarkers: Troponin I and T (gold standard for MI diagnosis). Creatine kinase-MB (CK-MB). Complete blood count (CBC). Lipid profile. Basic metabolic panel (to assess electrolyte imbalances).
7.1.1. Imaging and Procedures: Electrocardiogram (ECG): ST-segment elevation or other changes. Echocardiogram: Wall motion abnormalities. Coronary angiography: Visualize and confirm blockages. Chest X-ray: Rule out other causes like aortic dissection. (McCance & Huether, 2019, Chapter 33)