Cardiac Rhythms and ECG Overview

Study of a patient's cardiac rhythms using an ECG may indicate normal or abnormal conditions. Abnormal rhythms are called arrhythmia or sometimes, dysrhythmia. Arrhythmia is an abnormally slow or fast heart rate or an irregular cardiac rhythm. During a single heart beat, several electrical events occur. These events are part of an ECG tracing and are called P, Q, R, S, T and U.

The first movement of the ECG tracing (usually upwards) is the P wave, indicating electrical activity that triggers atrial contraction. The QRS complex indicates ventricular depolarization and contraction and are usually of greater amplitude than the P wave. The PR interval indicates the electrical signal traveling from the sinus node to the ventricles.

T wave is normally a smaller (than QRS) upwards waveform, indicating ventricular repolarization.

cardiac rhythms example tracing

cardiac rhythms strip

Cardiac Rhythm Strip Reference Guide

Our rhythm strips guide provides information on essential dysrhythmia categories:

  • Atrial
    • Premature Atrial Contractions
    • Atrial Flutter
    • Atrial Fibrillation
    • Multifocal Atrial Tachycardia
    • Wandering Atrial Pacemaker
  • Junctional
    • Junctional Rhythm
    • Junctional Tachycardia
    • Premature Junctional Contraction
    • Supraventricular Tachycardia
  • Ventricular
    • Premature Ventricular Contractions (several type of)
    • Accelerated Idioventricular Rhythm
    • Ventricular Fibrillation
    • Monomorphic Ventricular Tachycardia
    • Polymorphic Ventricular Tachycardia
  • Heart Blocks
    • First Degree Heart Block
    • Second Degree Heart Block, Type 1 - Mobitz I
    • Second Degree Heart Block, Type 2 - Mobitz II
    • Third Degree Heart Block
  • Sudden Arrhythmic Death Syndrome

For each cardiac rhythm category we provide one or more ECG tracings. A synopsis of the cardiac rhythm (dysrhythmia) is provided and electronic calipers can be used to study each tracing.

Cardiac Rhythms Strip Guide

Cardiac Rhythms - Training Tools

Learn about cardiac rhythms using these tools:

  • Cardiac Rhythm Strips Drills
  • Rhythms Quiz
  • ECG Guide
  • Basic Training Lessons

Each of these training methods is summarized below.

Authors and Sources

Authors and Reviewers


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