‍Introduction

In this pacing mode, both atrial and ventricular pacing is observed.

Indications for AV sequential pacing

• Sick sinus syndrome with bradycardia
• Brady-tachy syndrome
• Complete heart block

ECG features

• Atrial and ventricular pacing spikes are visible before each QRS complex
• There is 100% atrial capture — small P waves are seen following each atrial pacing spike
• There is 100% ventricular capture — a QRS complex follows each ventricular pacing spike

ECG 1 AV sequential right ventricular stimulation  (atrial and ventricular pacing spikes are visible before each QRS complex)

ECG 2 AV sequential BiV stimulation (atrial and ventricular pacing spikes are visible before each QRS complex)

References

1) Yashar JJ, Kitzes DL, Arif M, Carleton RA, Goldberg M, Burnard RJ, Weyman AK, Yashar J. Atrioventricular sequential pacemakers: indications, complications, and long-term follow-up. Ann Thorac Surg. 1980 Jan;29(1):91-8. doi: 10.1016/s0003-4975(10)61638-4. PMID: 7356816.
2) Dalia T, Amr BS. Pacemaker Indications. [Updated 2020 Aug 31]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK507823/
3) https://www.uptodate.com/contents/ecg-tutorial-pacemakers
‍4) Brignole M, Auricchio A, Baron-Esquivias G, Bordachar P, Boriani G, Breithardt OA, Cleland J, Deharo JC, Delgado V, Elliott PM, Gorenek B, Israel CW, Leclercq C, Linde C, Mont L, Padeletti L, Sutton R, Vardas PE; ESC Committee for Practice Guidelines (CPG), Zamorano JL, Achenbach S, Baumgartner H, Bax JJ, Bueno H, Dean V, Deaton C, Erol C, Fagard R, Ferrari R, Hasdai D, Hoes AW, Kirchhof P, Knuuti J, Kolh P, Lancellotti P, Linhart A, Nihoyannopoulos P, Piepoli MF, Ponikowski P, Sirnes PA, Tamargo JL, Tendera M, Torbicki A, Wijns W, Windecker S; Document Reviewers, Kirchhof P, Blomstrom-Lundqvist C, Badano LP, Aliyev F, Bänsch D, Baumgartner H, Bsata W, Buser P, Charron P, Daubert JC, Dobreanu D, Faerestrand S, Hasdai D, Hoes AW, Le Heuzey JY, Mavrakis H, McDonagh T, Merino JL, Nawar MM, Nielsen JC, Pieske B, Poposka L, Ruschitzka F, Tendera M, Van Gelder IC, Wilson CM. 2013 ESC Guidelines on cardiac pacing and cardiac resynchronization therapy: the Task Force on cardiac pacing and resynchronization therapy of the European Society of Cardiology (ESC). Developed in collaboration with the European Heart Rhythm Association (EHRA). Eur Heart J. 2013 Aug;34(29):2281-329. doi: 10.1093/eurheartj/eht150. Epub 2013 Jun 24. PMID: 23801822.
5) https://litfl.com/pacemaker-rhythms-normal-patterns/