Medical review: October 2026. Educational summary of the 2021 ESC Guidelines on cardiac pacing and cardiac resynchronization therapy, with reference to the 2025 ESC/EHRA consensus on conduction system pacing. Assess reversible causes and the clinical context before deciding on implantation.
Sinus node dysfunction (SND)
- Class I: Permanent pacing is indicated when symptoms (syncope, presyncope, fatigue or exercise intolerance) are clearly attributable to bradyarrhythmia in SND, including bradycardia–tachycardia syndrome.
- Important: A resting heart rate below 40/min, or a pause of a particular duration, does not by itself establish an indication for pacing. Asymptomatic SND is not an indication.
- Symptomatic chronotropic incompetence requires clinical evaluation, confirmation of symptom–rhythm correlation and consideration of pacing in appropriate patients.
Atrioventricular block (AVB)
- Class I: Permanent or intermittent third-degree AVB, Mobitz II second-degree AVB, high-degree AVB or infranodal 2:1 block, when not due to a reversible or physiological cause, warrants permanent pacing regardless of symptoms.
- Mobitz I / nodal 2:1 AVB: Correlate symptoms, site of block and clinical circumstances; pacing is not automatic when asymptomatic.
- First-degree AVB: Marked PR prolongation causing attributable haemodynamic symptoms may justify individual assessment; isolated asymptomatic PR prolongation is not a routine pacing indication.
- 2:1 AVB: Cannot be reliably designated Mobitz I or II from the surface ECG alone. Investigate the level of block when needed.
- Do not pace an AVB caused by a transient, correctable and preventable condition unless persistence or another indication is established.
Bundle branch block and unexplained syncope
- In unexplained syncope with bifascicular block, EPS/implantable monitoring can establish an indication; a positive EPS (e.g. HV ≥70 ms or induced infra-Hisian block) supports pacing. Empirical pacing may be considered in selected patients after risk assessment.
- Alternating bundle branch block is a pacing indication even without symptoms. Asymptomatic isolated bundle branch block is not.
Reflex syncope
Class I (ESC 2021): Dual-chamber pacing can reduce recurrence in selected patients aged over 40 with severe, unpredictable, recurrent reflex syncope and documented asystolic cardioinhibition: symptomatic spontaneous pause >3 s, asymptomatic spontaneous pause >6 s, cardioinhibitory carotid sinus syndrome or asystolic tilt-induced syncope. Pacing is not indicated without evidence of a cardioinhibitory mechanism.
When urgent hospital evaluation is required
Haemodynamic compromise, syncope with suspected high-grade conduction disease, symptomatic advanced AVB or severe bradycardia require prompt monitoring, treatment of reversible triggers and access to emergency pacing if necessary. Urgent assessment does not mean every patient requires immediate permanent pacemaker implantation.
Device choice also depends on LVEF, anticipated ventricular pacing burden and heart failure: CRT or conduction system pacing can be preferable to conventional RV pacing in selected patients.
References: ESC 2021 cardiac pacing guidelines; 2025 ESC/EHRA conduction system pacing consensus.
