What are the next steps for a healthy, asymptomatic 79-year-old man with an electrocardiogram (ECG) showing normal sinus rhythm with right bundle branch block (RBBB), left anterior fascicular block, and bifascicular block?

Management of Asymptomatic 79-Year-Old Man with Bifascicular Block

For an asymptomatic 79-year-old man with ECG showing normal sinus rhythm with RBBB, left anterior fascicular block, and bifascicular block, no permanent pacemaker implantation is indicated as there is strong evidence that pacing is not beneficial in asymptomatic patients with bundle branch block.

Evaluation of Asymptomatic Bifascicular Block

Initial Assessment

• Confirm the ECG findings of:
  • Right bundle branch block (RBBB)
  • Left anterior fascicular block
  • Normal sinus rhythm
  • Absence of alternating bundle branch block (which would warrant immediate pacing)

Risk Stratification

• Despite the presence of bifascicular block, the patient is:
  • Asymptomatic (no syncope, presyncope, or heart failure symptoms)
  • In normal sinus rhythm
  • Without documented high-degree AV block

Evidence-Based Approach

• European Society of Cardiology guidelines clearly state that permanent pacemaker implantation is not indicated for bundle branch block (BBB) without symptoms, as only a small minority of these patients will develop AV block (1-2% per year) 1
• ACC/AHA/HRS guidelines similarly do not recommend pacing for asymptomatic bifascicular block 1
• The rate of progression from bifascicular block to third-degree AV block is slow 1
• No single clinical or laboratory variable, including bifascicular block alone, identifies patients at high risk of death due to future bradyarrhythmia 1

Recommended Management

Monitoring and Follow-up

• Annual clinical evaluation with ECG is recommended for surveillance of potential progression
• More frequent follow-up (every 3-6 months) may be considered given the patient's age (79) and presence of both RBBB and left anterior fascicular block 2
• Patient education regarding symptoms that would warrant immediate evaluation:
  • Syncope or presyncope
  • Unexplained dizziness
  • Exercise intolerance
  • Symptoms of heart failure

When to Consider Further Testing

• If the patient develops symptoms, particularly syncope, additional evaluation is warranted:
  • 24-48 hour continuous cardiac monitoring
  • Echocardiography to assess cardiac structure and function
  • Consider electrophysiological study (EPS) if syncope occurs

Indications for Pacemaker in the Future

Permanent pacing would be indicated if the patient develops:

1. Alternating bundle branch block (clear ECG evidence of block in all three fascicles on successive ECGs) 1
2. Syncope not demonstrated to be due to other causes 1
3. HV interval ≥70 ms on electrophysiological study 1
4. Evidence of infranodal block during EPS 2
5. Documented intermittent high-degree AV block 1

Important Caveats

• Bifascicular block in elderly patients requires vigilance but not immediate intervention when asymptomatic
• The presence of bifascicular block may complicate the management of future cardiac conditions or surgical procedures
• If the patient requires medications that could further impair AV conduction (e.g., beta-blockers, calcium channel blockers), closer monitoring may be warranted
• Anesthesia may precipitate complete heart block in patients with pre-existing bifascicular block 3

Conclusion

For this asymptomatic 79-year-old man with bifascicular block, current guidelines strongly support observation rather than prophylactic pacemaker implantation. The focus should be on regular follow-up and prompt evaluation if symptoms develop.