Pacemaker Modes

Pacemaker modes use a 3–5 letter code describing

  1. Chamber paced
  2. Chamber sensed
  3. Response to sensing
  4. (Optional) Rate modulation
  5. (Optional) Multisite pacing
Pacemaker Code
1
First letter
Chamber paced
A Atrium
V Ventricle
D Atrium and ventricle
O No pacing
2
Second letter
Chamber sensed
A Atrium
V Ventricle
D Atrium and ventricle
O No sensing
3
Third letter
Response to sensing
O No response
I Inhibited
T Triggered
D Dual response

Core Modes

DDD (Dual paced, dual sensed, dual response)

  • Paces: Atrium + Ventricle
  • Senses: Atrium + Ventricle
  • Response:
    • Triggers ventricular pacing after sensed atrial beat (AV synchrony)
    • Inhibits pacing if intrinsic activity present
  • Use:
    • Most common
    • AV block with intact sinus node
    • Sick sinus + AV conduction disease

Maintains AV synchrony → most “physiologic”

VVI (Ventricle paced, ventricle sensed, inhibited)

  • Paces: Ventricle only
  • Senses: Ventricle
  • Response: Inhibits pacing if intrinsic ventricular beat
  • Use:
    • Atrial fibrillation with slow ventricular response
    • When atrial lead not needed or not possible

No AV synchrony → can cause pacemaker syndrome

AAI (Atrium paced, atrium sensed, inhibited)

  • Paces: Atrium
  • Senses: Atrium
  • Response: Inhibits if intrinsic atrial beat
  • Use:
    • Pure sinus node dysfunction
    • Intact AV conduction

Requires reliable AV conduction

DDI (Dual paced, dual sensed, inhibited only)

  • Paces: Atrium + Ventricle
  • Senses: Atrium + Ventricle
  • Response: Inhibits only (no tracking of atrial beats)
  • Use:
    • Prevents rapid ventricular pacing in atrial tachyarrhythmias

No atrial tracking → safer in AF/flutter

DOO / VOO / AOO (Asynchronous modes)

  • No sensing
  • Fixed-rate pacing regardless of intrinsic rhythm
  • Use:
    • Magnet mode
    • OR / electrocautery situations

Can cause R-on-T if competing rhythm

4th Letter (Rate Modulation “R”)

  • Example: DDDR, VVIR
  • Adjusts pacing rate based on activity (motion, respiration)
  • Use: chronotropic incompetence
PPM Comparison
Mode AV synchrony Tracks atrium Typical use
DDD Yes Yes AV block, most patients
VVI No No AF with slow rate
AAI Yes N/A Sinus node dysfunction
DDI Partial No Atrial arrhythmias
DOO No No Temporary/asynchronous
DDD AV block, most patients
AV synchrony Yes
Tracks atrium Yes
VVI AF with slow rate
AV synchrony No
Tracks atrium No
AAI Sinus node dysfunction
AV synchrony Yes
Tracks atrium N/A
DDI Atrial arrhythmias
AV synchrony Partial
Tracks atrium No
DOO Temporary/asynchronous
AV synchrony No
Tracks atrium No

Trick

  • DDD = Does Everything
  • VVI = Ventricle Only
  • AAI = Atrium Only
  • DDI = Dual but Doesn’t track

References

  1. Bernstein, A. D., Daubert, J.-C., Fletcher, R. D., Hayes, D. L., Lüderitz, B., Reynolds, D. W., Schoenfeld, M. H., & Sutton, R. (2002). The revised NASPE/BPEG generic code for antibradycardia, adaptive-rate, and multisite pacing. Pacing and Clinical Electrophysiology, 25(2), 260–264. https://doi.org/10.1046/j.1460-9592.2002.00260.x
  2. Bernstein, A. D., Camm, A. J., Fisher, J. D., Fletcher, R. D., Mead, R. H., Nathan, A. W., Parsonnet, V., Rickards, A. F., Smyth, N. P., & Sutton, R. (1987). The NASPE/BPEG generic pacemaker code for antibradyarrhythmia and adaptive-rate pacing and antitachyarrhythmia devices. Pacing and Clinical Electrophysiology, 10(4), 794–799. https://doi.org/10.1111/j.1540-8159.1987.tb06059.x
  3. Kusumoto, F. M., Schoenfeld, M. H., Barrett, C., Edgerton, J. R., Ellenbogen, K. A., Gold, M. R., Goldschlager, N. F., Hamilton, R. M., Joglar, J. A., Kim, R. J., Lee, R., Marine, J. E., McLeod, C. J., Oken, K. R., Patton, K. K., Pellegrini, C. N., Selzman, K. A., Thompson, A., & Varosy, P. D. (2019). 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay. Journal of the American College of Cardiology, 74(7), e51–e156. https://doi.org/10.1016/j.jacc.2018.10.044
  4. Gregoratos, G., Abrams, J., Epstein, A. E., Freedman, R. A., Hayes, D. L., Hlatky, M. A., Kerber, R. E., Naccarelli, G. V., Schoenfeld, M. H., Silka, M. J., Winters, S. L., & Gibbons, R. J. (2002). ACC/AHA/NASPE 2002 guideline update for implantation of cardiac pacemakers and antiarrhythmia devices: Summary article. Journal of the American College of Cardiology, 40(9), 1703–1719. https://doi.org/10.1016/S0735-1097(02)02528-X
  5. Slotwiner, D., Varma, N., Akar, J. G., Annas, G., Beardsall, M., Fogel, R. I., Galizio, N. O., Glotzer, T. V., Leahy, R. A., Love, C. J., McLean, R. C., Mittal, S., Morichelli, L., Patton, K. K., Raitt, M. H., Ricci, R. P., Rickard, J., Schoenfeld, M. H., Serwer, G. A., ... Wilkoff, B. L. (2015). HRS expert consensus statement on remote interrogation and monitoring for cardiovascular implantable electronic devices. Heart Rhythm, 12(7), e69–e100. https://doi.org/10.1016/j.hrthm.2015.05.008