Ischemia
Summary
Ischemia is inadequate blood flow to tissues resulting in oxygen and nutrient deprivation. It can be acute or chronic and may lead to tissue dysfunction or death (infarction) if prolonged. Common causes include thrombosis, embolism, vasospasm, and atherosclerotic narrowing.
Detail
Ischemia occurs when oxygen delivery fails to meet metabolic demands of tissues, typically due to reduced blood flow. The mismatch between supply and demand can result from decreased arterial inflow (atherosclerosis, thrombosis, embolism, vasospasm) or increased metabolic needs. Cellular consequences include ATP depletion, anaerobic metabolism with lactate accumulation, cellular swelling, and membrane dysfunction. Clinically presents with pain (angina in heart, claudication in limbs), organ dysfunction, and potential tissue death. Reversible if blood flow is restored quickly; irreversible damage (infarction) occurs after critical time thresholds (20-40 minutes for myocardium, 3-6 minutes for brain). Key clinical examples include myocardial ischemia (coronary artery disease), cerebral ischemia (stroke/TIA), mesenteric ischemia (bowel), and peripheral arterial disease. Diagnosis involves clinical assessment, imaging (angiography, CT/MR perfusion), and biomarkers. Treatment focuses on revascularization, antiplatelet/anticoagulation, and risk factor modification.
Sources
- Robbins Basic Pathology (Kumar et al.)
- Harrison's Principles of Internal Medicine
- Pathophysiology of Disease (McPhee & Hammer)
- First Aid for the USMLE Step 1
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