A permanent pacemaker is implanted to treat bradyarrhythmias or conduction disorders that prevent the heart from maintaining an adequate heart rate or cardiac output. Pacemakers are most commonly required for symptomatic bradycardia, advanced atrioventricular (AV) block, and sinus node dysfunction (SND).

The American College of Cardiology (ACC), American Heart Association (AHA), and Heart Rhythm Society (HRS) provide official guideline-based recommendations for pacemaker implantation.

Primary Reference: ACC/AHA/HRS Guideline for Device-Based Therapy of Cardiac Rhythm Abnormalities

Pacemakers are required when intrinsic cardiac electrical activity is too slow or fails to conduct properly, resulting in:

• Persistent or intermittent bradycardia
• AV block impairing atrioventricular conduction
• Sinus pauses or chronotropic incompetence
• Symptoms such as syncope, presyncope, fatigue, heart failure, or exercise intolerance

The essential principle:

Is the rhythm disturbance producing symptoms or hemodynamic compromise? If yes, pacing is generally indicated.

Sinus node dysfunction includes sinus bradycardia, sinus pauses, sinus arrest, and chronotropic incompetence.

Pacemaker implantation is recommended for:

• Symptomatic sinus bradycardia
• Symptomatic chronotropic incompetence
• Sinus pauses or sinus arrest causing symptoms (or pauses ≥3 seconds while awake)
• Symptomatic bradycardia caused by medications required for another condition (e.g., beta-blockers)

• Minimally symptomatic patients with chronic HR < 40 bpm while awake
• Unexplained syncope with documented SND on monitoring

• Bradycardia < 40 bpm without clear symptom correlation

Reference: StatPearls – Sinus Node Dysfunction

Pacemaker use in AV block is often more straightforward due to the risk of asystole in advanced block.

Permanent pacing is recommended for:

• Complete (3rd-degree) AV block (symptomatic or not)
• Mobitz type II AV block
• High-grade AV block (≥2 consecutive blocked P waves)
• Symptomatic second-degree AV block (Mobitz I or II)
• AV block resulting from required medications
• Persistent AV block after MI, cardiac surgery, or ablation

• First-degree AV block with symptoms clearly due to AV delay
• Asymptomatic Mobitz I AV block with wide QRS (suggesting infranodal disease)
• Post-MI transient AV block with persistent conduction abnormalities

• First-degree AV block with PR > 300 ms, even without symptoms

Reference: ACC/AHA/HRS – Bradycardia Guidelines Summary

Pacemaker implantation is indicated for:

• Persistent Mobitz II or 3rd-degree AV block after anterior MI
• Symptomatic bradycardia or high-grade block after inferior MI

Reference: AHA STEMI Guidelines

Pacemaker is indicated for:

• Recurrent syncope with documented cardioinhibitory response
• Asystole ≥ 3 seconds during carotid sinus massage

Indications include:

• Congenital complete heart block
• Post-surgical AV block
• Symptomatic bradycardia in complex congenital repairs

Pacemaker indicated when:

• Symptomatic bradycardia is present
• AV node ablation is planned (“pace-and-ablate”)

Reference: ACC/AHA/HRS AFib Management Guidelines

Pacemaker should NOT be implanted for:

• Asymptomatic sinus bradycardia
• Nocturnal/sleep-related sinus pauses
• AV block due to reversible causes (e.g., drug toxicity, Lyme disease, hypothyroidism, hyperkalemia)
• Expected transient AV block
• Asymptomatic first-degree AV block
• Asymptomatic Mobitz I block with narrow QRS complexes

Reference: NICE Guideline – Bradycardia Management

• Pacemakers treat symptomatic bradyarrhythmias or conduction disturbances.
• Third-degree AV block and Mobitz II are almost always Class I indications.
• In sinus node dysfunction, symptoms drive pacemaker need.
• Reversible causes of bradycardia should be corrected before considering pacing.
• Pacemakers are not indicated for asymptomatic or physiologic bradycardia.
• Guideline decisions should follow ACC/AHA/HRS recommendations.