What are the indications for pacemaker implantation?

Pacemaker Indications

Pacemaker implantation is definitively indicated for complete heart block with symptomatic bradycardia, type II second-degree AV block (even when asymptomatic), and sinus node dysfunction with documented correlation between symptoms and bradycardia. 1, 2

Class I Indications (Definitive - Implant the Pacemaker)

Complete Heart Block (Third-Degree AV Block)

• Symptomatic bradycardia with documented correlation between symptoms and heart rhythm 1, 2
• Congestive heart failure attributable to bradycardia 2
• Documented asystole ≥3.0 seconds or escape rate <40 bpm, even in asymptomatic patients 1, 2
• Confusional states that resolve with temporary pacing 1, 2
• Need for medications (antiarrhythmics, beta-blockers) that suppress escape rhythms 2

Second-Degree AV Block

• Type II second-degree AV block - requires pacing even when asymptomatic, as progression to complete heart block is common 1, 2
• Any second-degree AV block with symptomatic bradycardia 1, 2
• Advanced second-degree AV block persisting 10-14 days after cardiac surgery 3, 1

Bifascicular/Trifascicular Block

• Intermittent complete heart block with symptomatic bradycardia 2, 4
• Intermittent type II second-degree AV block, even without symptoms 1, 2
• External ophthalmoplegia with bifascicular blocks 3, 2

Sinus Node Dysfunction (Sick Sinus Syndrome)

• Documented symptomatic bradycardia with clear correlation between symptoms and heart rate <40 bpm 1, 2
• Bradycardia-tachycardia syndrome requiring antiarrhythmic drugs (other than digitalis or phenytoin) that cause symptomatic bradycardia 1, 2

Post-Myocardial Infarction

• Persistent advanced second-degree or complete heart block 2, 4
• Transient advanced AV block with associated bundle branch block 2

Pediatric Patients

• Advanced second- or third-degree AV block with symptomatic bradycardia, ventricular dysfunction, or marked exercise intolerance 1
• Postoperative advanced AV block persisting ≥7 days after cardiac surgery 1
• Congenital third-degree AV block with wide QRS escape rhythm, complex ventricular ectopy, ventricular dysfunction, or ventricular rate <55 bpm in infants 1, 2

Special Indications

• Hypersensitive carotid sinus syndrome with syncope due to cardioinhibitory reflex 2

Class II Indications (Reasonable - Consider Pacemaker)

Asymptomatic Conduction Disease

• Asymptomatic complete heart block with ventricular rates ≥40 bpm 1, 2
• Asymptomatic type II second-degree AV block 1, 2
• Asymptomatic second or third-degree AV block with ventricular rate <45 bpm when awake 3, 2

Syncope with Conduction Abnormalities

• Bifascicular or trifascicular block with syncope when complete heart block not proven but suspected 1, 2
• Markedly prolonged HV interval >100 msec on electrophysiology study 1, 2

Other Considerations

• Medically refractory symptomatic hypertrophic cardiomyopathy with significant LV outflow tract obstruction 1
• Biventricular pacing for advanced heart failure with major intraventricular conduction defects, predominantly left bundle branch block 1, 4

Class III Indications (Do NOT Implant)

Absolute Contraindications

• First-degree AV block without symptoms 2
• Asymptomatic fascicular block without AV block 2
• Sinus node dysfunction in asymptomatic patients, even with heart rate <40 bpm (particularly in trained athletes where this is physiologic) 1, 2
• Transient AV block that returns to normal conduction within 1 week 2
• Asymptomatic congenital heart block without profound bradycardia 2
• Symptoms clearly documented NOT to be associated with slow heart rate 3, 2

Critical Pitfalls to Avoid

Never implant a pacemaker based on bradycardia alone - symptoms must correlate with documented bradycardia through ambulatory monitoring or transtelephonic ECG 1, 5

In complete heart block, presume symptoms are cardiac unless proven otherwise 1

Sinus bradycardia in trained athletes is physiologic and does not require pacing 1

Avoid long-term right ventricular apical pacing when possible, as emerging data suggest potential harmful effects 1

Distinguish cardioinhibitory from vasodepressor components in carotid sinus syndrome - pacing only addresses the cardioinhibitory component 3

Device Selection Algorithm

Maintain AV synchrony in older patients to preserve atrial contribution to ventricular filling 1

For sick sinus syndrome without AV block, dual-chamber devices are cost-effective and reduce reoperation rates (primarily due to development of AV block requiring upgrade) 6

Minimize unnecessary ventricular pacing - program dual-chamber devices to reduce right ventricular pacing when possible 6, 7