EKG Exam 4

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EKG Exam 4
2014-04-16 15:17:06

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  1. Ischemia
    • decrease in blood supply (hypoxia)
    • acute, short term, transient
    • stable plaque narrows artery; demand (e.g., exercise) exceeds supply
    • Tissue not injured, but recovers following removal of ischemia
  2. Injury
    • damage (acute)
    • demand > supply even at rest for prolonged period
    • Often caused by unstable plaque
  3. Infarction
    necrosis due to obstruction of blood supply (old - irreversible damage has already occurred)
  4. ST segment
    • measured from the J point (end of QRS complex) to the beginning of the T wave
    • represents the ventricles are between electrical depolarization and repolarization.
  5. ischemia is represented by
    • ST depression and inverted T waves
    • (measure 2 small boxes to right of J point, must be depressed > 1 mm from baseline at this point)
  6. T wave shape
    • Asymmetrical T waves are normal
    • Symmetrical T waves are found in pathological states such as - Ischemia, Electrolyte abnormalities, CNS problems
  7. injury is represented by
    • ST elevation, with or without loss of R wave
    • with or without T wave changes
  8. infarction
    • significant Q waves >= 0.04 sec or 1/3 of amplitude of QRS
  9. U wave
    a potential undulation of unknown origin immediately following the T wave and often concealed by it; seen in the normal electrocardiogram and accentuated in tachyarrhythmias and electrolyte disturbances.
  10. Hypokalemia ↓ K+
    • Low amplitude T waves
    • Prominent U waves (normal U waves are ventricular afterpolarizations, but many abnormal “U” waves are altered/interrupted T waves)
  11. Hyperkalemia ↑ K+
    • Tall/Peaked T waves
    • Flattened/lost P waves
    • Widening of QRS --> risk of ventricular defibrillation
  12. Hypocalcemia ↓ Ca2+
    QT prolongation with ↑ ST
  13. Hypercalcemia ↑ Ca2+
    QT shortened, as ↓ ST
  14. Quinidine effects:
    • Prolonged QT
    • (may have notched P, widened QRS, and depressed ST as well)
  15. Long QT syndrome
    • Acquired, e.g., medications, or may be an autosomal dominant condition
    • Guesstimate for HR 60-100 - normal QT interval should be < ½ of the RR interval
  16. Pulmonary embolism: EKG
    • Clinical scoring systems useful for differential diagnosis of dyspnea, tachycardia, acute chest pain
    • EKG changes may be seen in ~20% of PE patients; (+) findings may help with diagnosis, but (–) ones do not rule out
    • Tachycardia, “S1,Q3, inverted T3”, ST depression in II, T wave inversion in V1-4, all classically associated with pulmonary embolism (think increased right heart afterload)