Paced Rhythms

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Pacemakers are programmed with five variables, the first three are relevant to emergency physicians.

 

Pacemaker codes.

Examples

ECG Showing Paced Rhythm

Ventricular Paced Rhythm

Normal appearance of ventricular paced rhythm. Note the pacing spikes preceding each QRS complex. The pacing lead is in the right ventricle, which produces a left bundle branch block pattern in V1, and down-going complexes across the precordium with expected discordant changes.
ECG Showing Paced Rhythm

Ventricular Paced Rhythm

Atrial flutter without native conduction but with paced ventricular activity. The pacemaker threshold was set to 40 beats per minute, and was later increased to 60 beats per minute.
ECG Showing Paced Rhythm

Atrial Paced Rhythm

This patient has a dual chamber pacemaker (i.e., leads within the right atria and the right ventricle) that is in DDD mode. Currently, the rhythm is atrial-paced (note the pacemaker spikes immediately preceding the P waves) and there is a prolonged PR interval without ventricular pacing.
ECG Showing Paced Rhythm

Ventricular Paced Rhythm

Ventricular paced rhythm in a patient with a single right ventricular lead (note the pacer spikes immediately preceding the QRS complex). The pacer mode is set to VVI with a rate of 80 bpm. P waves can be seen marching through the rhythm indicating AV dissociation. This patient had known complete heart block.
ECG Showing Paced Rhythm

Biventricular Paced Rhythm

Normally, ventricular paced rhythms will have a left bundle branch block appearance with downgoing complexes across the precordium (i.e., the right ventricle is the chamber being paced). Biventricular pacemakers like this one often have a right bundle branch block appearance (i.e., upgoing complex in V1) because an additional lead in the coronary sinus paces the left ventricle. This is called cardiac resynchronization therapy.
ECG Showing Paced Rhythm

Dual Chamber Pacemaker

Dual chamber pacemaker programmed to DDD mode.

References

  1. Wagner GS, Strauss DG. Marriott’s Practical Electrocardiography. 12th ed. Lippincott Williams & Wilkins; 2014.
  2. Mulpuru SK, Madhavan M, McLeod CJ, Cha YM, Friedman PA. Cardiac Pacemakers: Function, Troubleshooting, and Management: Part 1 of a 2-Part Series. Journal of the American College of Cardiology. 2017;69(2):189-210.