Learning Objective
After completing this section, learners will be able to identify how ST-segment changes and electrolyte disturbances (potassium and calcium) affect the ECG and recognize their characteristic patterns.
ST Segment Changes
ST Elevation:
- Causes: Transmural myocardial infarction, Prinzmetal angina (coronary vasospasm)
ST Depression:
- Causes: Subendocardial ischemia, exertional (stable) angina
Potassium (K⁺)
Hyperkalemia:
- Accelerates repolarization → tall, peaked T waves, shortened QT interval
Hypokalemia:
- Slows repolarization → prominent U waves, prolonged QT interval
Calcium (Ca²⁺)
Hypercalcemia:
- Decreases the QT interval
Hypocalcemia:
- Increases the QT interval
