ECG Level 2 Tutorial: Origins of Activity
Tutorial: Origins of Activity
This module will teach how to determine the origins (pacemaker location) of the electrical activity.
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Develop your skills by completing our Practice Cases!
Tutorial: Origins of Activity Wavy Baselines
Times Practiced
Cases Completed
1h 24m
Total Time spent
1m 24s
Average Time
Wavy Baselines
Wavy Baselines!

When the heart is in between heartbeats (diastole), there should be no electrical activity (blue and yellow ovals). The tracing should show a nice flat "isoelectric" line that is doing nothing:
no activity in blue and yellow ovals

Sometimes this nice flat line is replaced by some random wavy garbage. There are 2 things that cause wavy garbage:
  • fibrillation
  • muscle tremors (or patient movement)
Fibrillation is chaotic electrical activity. Fibrillation can occur in the atria or in the ventricles. If fibrillation is occuring in the atria, there will be no P waves. If fibrillation occurs in the ventricles, there will be no QRS complexes. The reverse is also true: the presence of regular consistent P waves rules out atrial fibrillation and the presence of QRS complexes rules out ventricular fibrillation.

Rule #1: Wavy baseline + regular P waves + QRS complexes = no fibrillation.

Below we see P waves + QRS complexes + wavy garbage. This is muscle tremor (or movement). Can you see the P waves? Can you see the T waves? They are all present.
wavy garbage WITH P waves and T waves easily seen = artifact

Rule #2: Wavy baseline + no P waves + QRS complexes = atrial fibrillation (probably) = atrial origin

Here are 2 examples of wavy garbage that is caused by atrial fibrillation. There are QRS complexes and T waves, but no P waves. Sometimes the wavy garbage can mimic P waves.
wavy garbage with NO P waves = atrial fibrillation (usually)
wavy garbage with NO P waves = atrial fibrillation (usually)

Rule #3: Wavy baseline with
no QRS complexes = ventricular fibrillation = ventricular origin

There are no QRS complexes in the ECG below. The ventricular rate is zero. This is one form of cardiac arrest. This patient will have no pulse and will require CPR and defibrillation.
wavy garbage and NO QRS = ventricular fibrillation

For more details on atrial fibrillation and ventricular fibrillation, see our helpful videos in the Rhythm Diagnostic Criteria tutorial.

Summary of the wavy garbage:
  • P waves + QRS + wavy garbage = movement artifact
  • No P waves + QRS + wavy garbage = atrial fibrillation = atrial origin
  • No QRS + wavy garbage = ventricular fibrillation = ventricular origin