Pacemaker ECG - An introduction

Raja Selvaraj, JIPMER

Pacemaker ECG - Raja Selvaraj

General principles of pacemaker function

Pacing

  • Delivers a rectangular electrical stimulus a timed intervals
  • Seen as a high frequency pacing spike
  • Followed by capture of the respective chamber

Pacing

pace_animation.gif

Pacing

pacing.jpg

Unipolar / bipolar pacing

uni_bi.jpg

Sensing

  • Watches for intrinsic activity
  • Generally inhibits pacing (resets timer)
  • For dual chamber pacemaker, sensing in atrium initiates pacing in ventricle after delay

Sensing

pace_sense_animation.gif

Sensing

sensing.png

Atrial pacing

aai.jpg

Ventricular pacing

rva.jpg

Pacing location - RVOT

rvot.jpg

Troubleshooting

Pacing spikes not seen

  • Not pacing because intrinsic rate is faster than set lower rate
  • Bipolar pacing - small spikes
  • Lead malfunction
  • Battery depletion
  • Concern if rate is slow and patient is symptomatic

R wave in V1

  • Normally LBBB pattern with RV pacing
  • But sometimes an R wave may be seen in V1
  • Can happen with LV pacing / septal perforation
  • But more often occurs in presence of normal location

Example ECGs

History of pacemaker implanted 2 years back

no_pacing.jpg

Pacemaker implanted for complete heart block

ddd3.jpg

Pacemaker implanted 2 weeks back, recurrent syncope

v_non_capture.jpg

Summary

  • Understanding basic functioning of pacemaker helps interpret ECGs
  • Stepwise approach
    • Identify device
    • For each location - Pacing, sensing
  • As in other situations, interpret in context of overall clinical findings