A more detailed discussion of pacemaker technology is conducted elsewhere. Specifically, single and dual chamber pacing modes have their own dedicated chapter.

Previous questions about pacing modes include:

This is a brief point-form summary.

Single chamber pacing modes

  • Single-chamber atrial pacing
    • AOO - asynchronous atrial pacing
    • AAI - atrial demand pacing
    • AAT - atrial pacing
  • Single-chamber ventricular pacing
    • VOO - asynchronous ventricular pacing
    • VVI - ventricular demand pacing
    • VVT - ventricular pacing

Dual chamber pacing modes

  • VAT - atrial sensing, ventricular pacing
  • DDD - dual chamber demand pacing

 

Nomenclature of Pacing Modes

Position 1: chamber paced

Position 2: chamber sensed

Position 3: response to sensing

O = none

O = none

O = none

A = atrium

A = atrium

T = triggered

V = ventricle

V = ventricle

I = inhibited

D = dual

D = dual

D = dual (triggered and inhibited)

A Comparison of Single and Dual Chamber Pacing Modes
Pacing Mode Description Advantages Disadvantages
AOO asynchronous atrial pacing.
  • Only one lead required
  • Preserves AV synchrony in the presence of an intact AV node
  • Protects against interference by diathermy
  • contraindicated in the presence of intrinsic cardiac rhythms. 
  • If the rate is not high enough, you will have an underlying rhythm competing with the pacemaker.
  • Useless if the AV node is dysfunctional
  • Useless in the presence of AF
  • Increased risk of perforating the thin atrial wall
AAI atrial demand pacing
  • Only one lead required
  • Preserves AV synchrony in the presence of an intact AV node
  • Only paces on demand; allows intrinsic rhythm while the rate is high enough
  • Useless if the AV node is dysfunctional
  • Useless in the presence of AF

Increased risk of perforating the thin atrial wall

AAT atrial pacing
  • Only one lead required
  • Preserves AV synchrony in the presence of an intact AV node
  • Useful for testing atrial sensing (using the pacing spike)
  • Useless if the AV node is dysfunctional
  • Useless in the presence of AF
  • Unproductive in general (paces in response to normal atrial contraction, while the atrium is in a refractory period); thus, not a useful permanent mode
  • Increased risk of perforating the thin atrial wall
VOO asynchronous ventricular pacing
  • Only one lead required
  • Protects against interference by diathermy
  • Asynchronous AV contraction
  • May result in the R - on - T phenomenon
  • Difficult to assess ST changes (LBBB-like QRS morphology)
VVI ventricular demand pacing
  • Only one lead required
  • Only paces on demand; allows intrinsic rhythm while the rate is high enough
  • Asynchronous AV contraction
  • Difficult to assess ST changes (LBBB-like QRS morphology)
VVT ventricular pacing
  • Useful for testing ventricular sensing (using the pacing spike)
  • Asynchronous AV contraction
  • Unproductive in general (paces in response to normal ventricular contraction, while the ventricle is in a refractory period); thus, not a useful permanent mode
  • Difficult to assess ST changes (LBBB-like QRS morphology)
  • Possibility of "endless loop" tachycardia
VAT atrial sensing, ventricular pacing
  • AV synchrony is preserved
  • "Pacemaker syndrome" is thus avoided
  • Advantageous in patients with normal atrial activity and a dysfunctional AV node
  • Two leads required
  • Bundle of His is bypassed
  • Difficult to assess ST changes (LBBB-like QRS morphology)
  • Increased risk of perforating the thin atrial wall
DDD dual chamber demand pacing
  • AV synchrony is preserved
  • "Pacemaker syndrome" is thus avoided
  • Advantageous in patients with normal atrial activity and a dysfunctional AV node
  • Versatile mode, with hemodynamic
  • Two leads required
  • Bundle of His is bypassed
  • Possibility of "endless loop" tachycardia
  • Increased risk of perforating the thin atrial wall

References

Reade, M. C. "Temporary epicardial pacing after cardiac surgery: a practical review." Anaesthesia 62.3 (2007): 264-271.

Reade, M. C. "Temporary epicardial pacing after cardiac surgery: a practical review: Part 2: Selection of epicardial pacing modes and troubleshooting."ANAESTHESIA-LONDON- 62.4 (2007): 364.

Gammage, Michael D. "Temporary cardiac pacing." Heart 83.6 (2000): 715-720.

Sanders, Richard S. "The Pulse Generator." Cardiac Pacing for the Clinician. Springer US, 2008. 47-71.