Electrolyte Abnormalities

  • The “hypers” (­K, ­Ca) shorten the QT interval
  • The “hypos” (K, Ca) prolong the QT interval
  • K abnormalities affect the T waves (­increased K: narrow Ts; decreased K: wide Ts)
  • Ca abnormalities affect the ST segments (­increased Ca: shorter STs; decreased Ca: longer STs)
​Hyperkalemia
  • Common findings, in order of severity:
  • Narrow based, peaked T waves (base of Ts “pinched down”)
  • Widened QRS complexes (nonspecific IVCD)
  • Axis shift, new fascicular block
  • Flattened P waves
  • QRS-T “sine wave” morphology
  • Double counting of HR by ECG interpretation software: highly specific for hyperkalemia
  • Arrhythmias: junctional rhythm; asystole; AV block; VT; VF
  • Less common findings:
    • Anterior ST segment elevation
    • “Brugada pattern”
    • Pathologic Q waves
Hypercalcemia
  • ST segment shortened
  • T waves are inscribed right after the QRS complex
  • May mimic coved ST segment elevation in anterior chest leads
  • May rarely cause a normothermic Osborn wave
  • ECG findings of hypercalcemia usually signify severity of hypercalcemia
Hypokalemia
  • Nonspecific ST depression (usually upsloping)
  • Wide, bifid T waves or T-U complexes
  • Prolonged QT/QU intervals
  • “Wavy ST-Ts” (3 waves between QRS complexes: T – U – P)
  • Severe hypokalemia may mimic ischemic ST segment depression
Hypocalcemia
  • Nice, smooth, normal looking T waves
  • Prolonged ST segments – T waves are pushed to the right
  • Prolonged QT intervals
  • A similar pattern is frequently seen in pts with advanced liver failure, even with normal Ca
Chronic renal failure, uremia
  • Combination of hyperkalemia and hypocalcemia
  • Flat, long ST segment followed by narrow-based, peaked T wave (“tent on a desert”)
  • Slowly upsloping ST segment followed by peaked T wave; QT prolonged