How is an electrocardiography (ECG) read (analyzed)?

Updated: Mar 11, 2019
  • Author: Tarek Ajam, MD, MS; Chief Editor: Terrence X O'Brien, MD, MS, FACC  more...
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Answer

Answer

The initial review of the 12-lead electrocardiogram (ECG) should encompass the following: heart rate and rhythm, P-QRS-T morphology, presence of ST segment, and PR-QRS-QT intervals (see the image below). Each ECG should be thoroughly analyzed ("read") in a systematic fashion to avoid overlooking important abnormalities. The following steps are important to consider:

  1. Rate: Normal versus tachycardia versus bradycardia
  2. Rhythm: Abnormal versus normal sinus 
  3. Intervals: PR, QRS, QT
  4. Axis: Normal versus left deviation versus right deviation
  5. Chamber abnormality: Atrial enlargement, ventricular hypertrophy
  6. QRST duration: Q waves, poor R-wave progression, ST-segment depressions/elevations, or T-wave changes
Electrocardiogram waves, intervals, and segments. Electrocardiogram waves, intervals, and segments.

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