What are the indications for pacemaker (artificial cardiac pacemaker) implantation?

Indications for Pacemaker Implantation

Permanent pacemaker implantation is indicated for symptomatic bradycardia due to complete heart block, sinus node dysfunction with documented symptomatic bradycardia, and advanced second-degree or type II second-degree AV block, as these conditions significantly impact morbidity, mortality, and quality of life. 1, 2, 3

Class I Indications (Definite Need for Pacing)

Complete Heart Block (Third-Degree AV Block)

• Implant a pacemaker for complete heart block with any of the following: 2, 3
  • Symptomatic bradycardia (fatigue, dizziness, syncope, heart failure)
  • Congestive heart failure
  • Documented asystole ≥3.0 seconds or escape rate <40 bpm (even if asymptomatic)
  • Confusional states that resolve with temporary pacing
  • Need for medications that suppress escape rhythms

Second-Degree AV Block

• Type II second-degree AV block requires pacing even when asymptomatic, as progression to complete heart block is common 2, 3
• Second-degree AV block with symptomatic bradycardia is a definite indication 2, 3
• Advanced second-degree AV block persisting 10-14 days after cardiac surgery requires permanent pacing 3

Sinus Node Dysfunction (Sick Sinus Syndrome)

• Implant for documented symptomatic bradycardia with correlation between symptoms and heart rate <40 bpm 1, 2, 3
• Bradycardia-tachycardia syndrome requiring antiarrhythmic drugs (other than digitalis or phenytoin) that cause symptomatic bradycardia 3
• The key is documented correlation between symptoms (syncope, presyncope, dizziness, fatigue) and bradycardia on monitoring 1, 2

Bifascicular/Trifascicular Block

• Intermittent complete heart block with symptomatic bradycardia 2, 3
• Intermittent type II second-degree AV block (even without symptoms) 2, 3

Post-Myocardial Infarction

• Persistent advanced second-degree or complete heart block after MI 2, 3
• Transient advanced AV block with associated bundle branch block after MI 3

Pediatric and Congenital Heart Disease

• Advanced second- or third-degree AV block with symptomatic bradycardia, ventricular dysfunction, or low cardiac output 4
• Postoperative advanced AV block persisting ≥7 days after cardiac surgery 4
• Congenital third-degree AV block with: 4, 3
  • Wide QRS escape rhythm
  • Complex ventricular ectopy
  • Ventricular dysfunction
  • Ventricular rate <55 bpm in infants

Hypersensitive Carotid Sinus Syndrome

• Recurrent syncope due to cardioinhibitory reflex with documented pauses 3

Class II Indications (Reasonable to Consider)

Class IIa (Weight of Evidence Favors Usefulness)

• Asymptomatic complete heart block with ventricular rates ≥40 bpm 2, 3
• Asymptomatic type II second-degree AV block 2, 3
• Bifascicular or trifascicular block with syncope when complete heart block not proven but suspected 2, 3
• Markedly prolonged HV interval >100 msec on electrophysiology study 2, 3

Class IIb (Usefulness Less Well Established)

• Medically refractory symptomatic hypertrophic cardiomyopathy with significant LV outflow tract obstruction 4
• Sinus node dysfunction with heart rates <40 bpm when symptom-bradycardia correlation not clearly documented 3

Class III Indications (Not Indicated - Do Not Implant)

Pacemaker implantation is contraindicated in: 2, 3

• First-degree AV block without symptoms
• Asymptomatic fascicular block without AV block
• Sinus node dysfunction in asymptomatic patients, even with heart rate <40 bpm (may be physiologic in athletes)
• Transient AV block that resolves within 1 week
• Asymptomatic congenital heart block without profound bradycardia
• Symptoms clearly documented NOT to be associated with bradycardia

Device Selection Considerations

Dual-Chamber vs. Single-Chamber Pacing

• Dual-chamber pacemakers are preferred over single-chamber atrial pacemakers in sick sinus syndrome, as they reduce reoperation rates (OR 0.48) and risk of atrial fibrillation (OR 0.75) 5
• Devices maintaining AV synchrony are preferred in older patients to preserve atrial contribution to ventricular filling 1
• Dual-chamber pacing is cost-effective (ICER £6,506) compared to single-chamber atrial pacing 5

Cardiac Resynchronization Therapy (Biventricular Pacing)

• Consider biventricular pacing for advanced heart failure with major intraventricular conduction defects, predominantly left bundle branch block 1, 2

Critical Pitfalls to Avoid

• Never implant based on bradycardia alone—symptoms must correlate with documented bradycardia 3
• In complete heart block, always presume symptoms are cardiac unless proven otherwise 3
• Sinus bradycardia in trained athletes is physiologic and does not require pacing 3
• Avoid long-term right ventricular apical pacing when possible, as emerging data suggest potential harmful effects 6
• Transient bradycardia in children is often self-limited—do not rush to implant without persistent documentation 4