Pacemakers

• Constantly monitors for need to pace
• Depending on programming will pace at varying lower and upper rates

Single Chamber

• Most common
• RV Lead

Dual Chamber

• RA Lead
• RV Lead

Note: LBBB like QRS

What do pacemakers do?

• Pace
• Sense
• (Defibrillate)

Pacemaker Modes

Common Modes: VVI, DDD, AAI, VOO

VOO

https://derangedphysiology.com/main/required-reading/cardiothoracic-intensive-care/Chapter%209.1.2.7/single-and-dual-chamber-pacing-modes

DDD

https://derangedphysiology.com/main/required-reading/cardiothoracic-intensive-care/Chapter%209.1.2.7/single-and-dual-chamber-pacing-modes

Pacemaker Issues

• Threshold
• Sensing
• Algorithms

Note: Pacemaker is usually not the problem

Threshold

• Testing how much output is needed to achieve pacing
• Set rate higher than patients intrinsic
• Progressively reduce output till lose capture (watch morphology change)
• Threshold is one above and set pacemaker to 3x or more

Failure to Capture

• Note enough output to achieve a QRS
• Example: lead fracture or lead dislodgement

Over and Under Sensing

• If spikes are where they shouldn't be or rate is much lower than the set lower rate, think about sensing issues

Sensing

• Pacemaker needs to be able to sense to know when to pace or not pace
• If it under-senses (b), it will miss QRS and pace when not needed
  • extra spikes
• If it over-sense (c), it will think other waves are QRS and not pace when needed
  • less spikes

Sitting