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Understanding the ECG Waveform Components

Apr 25, 2025

ECG Waveform Review

Introduction

  • Video by Sarah from registerednessrn.com
  • Focus on parts of the ECG waveform

P Wave

  • Represents atrial depolarization.
  • Leads to contraction of the atria initiated by the SA node.

PR Segment

  • Found right after the P wave and before the QRS complex.
  • Demonstrates the delay created by the AV node (gatekeeper).
    • Gives atria time to dump blood into the ventricles.

PR Interval

  • Measurement starts at the beginning of the P wave and extends to the beginning of the QRS complex.
  • Important for determining heart block.
  • Demonstrates the time for electrical signal to go from atria to AV node.
  • Long PR interval could indicate a heart block.

QRS Complex

  • Represents ventricular depolarization leading to contraction of the ventricles.
  • Atrial repolarization occurs but is overshadowed by ventricles.

J Point

  • Point where the QRS complex meets the ST segment.

ST Segment

  • Represents completion of ventricular depolarization and beginning of ventricular repolarization.
  • Should be isoelectric (flat and without depression or elevation).

T Wave

  • Represents beginning of ventricular repolarization (relaxation).
  • Large ventricles create the T wave upon relaxation.

Flat Line (Post T wave)

  • Represents completion of ventricular repolarization.
  • Flat line is isoelectric.

U Wave

  • Sometimes appears after T wave.
  • May indicate low potassium levels (hypokalemia).

QT Interval

  • Starts at beginning of QRS complex and ends after the T wave.
  • Demonstrates time taken for ventricles to contract and rest.

Recap of PQRST Complex

  1. P Wave: Atrial depolarization begins (contraction of atria).
  2. PR Segment: Atrial depolarization complete.
  3. QRS Complex: Ventricular depolarization begins; atrial repolarization occurs but is not visible.
  4. ST Segment: Ventricular depolarization completes.
  5. T Wave: Ventricular repolarization begins.
  6. Flat Line: Ventricular repolarization complete.

Conclusion

  • Explains each part of the ECG waveform and its significance.
  • Encourages watching more ECG interpretation videos via the provided YouTube link.

Full transcript