Is there an indication for temporary external pacing lead placement in patients with Right Bundle Branch Block (RBBB) undergoing Coronary Artery Bypass Grafting (CABG)?

Temporary Epicardial Pacing Leads for RBBB in CABG Surgery

There is no specific indication for routine placement of temporary external pacing leads in patients with isolated Right Bundle Branch Block (RBBB) undergoing Coronary Artery Bypass Grafting (CABG). 1

Current Guideline Recommendations

The 2018 ACC/AHA/HRS guideline on bradycardia and cardiac conduction delay provides clear recommendations regarding temporary pacing during cardiac surgery:

• For patients undergoing isolated CABG, routine placement of temporary epicardial pacing wires is reasonable (Class IIa, Level B-NR) 1
• This recommendation applies to all CABG patients regardless of pre-existing conduction disorders
• The guideline does not specify different management for patients with pre-existing RBBB

Risk Assessment for Bradycardia During CABG

While RBBB alone does not warrant special consideration for temporary pacing lead placement, several factors should be considered:

1. Conduction System Risk in CABG:

   • Conduction defects after CABG occur in 2-58% of cases 1
   • These are related to:
     • Pre-existing degenerative disease
     • Direct surgical damage
     • Myocardial ischemia
     • Inadequate myocardial protection

2. Specific Risk Factors for Post-CABG Pacing:

   • Advanced age 2
   • Pre-existing arrhythmias (especially bundle branch blocks) 2
   • Need for pacing during separation from cardiopulmonary bypass 2
   • Use of antiarrhythmic medications when leaving the operating room 2

Clinical Decision Algorithm

1. For all CABG patients:

   • Routine placement of temporary epicardial pacing wires is reasonable 1

2. Higher vigilance warranted if RBBB plus:

   • Advanced age
   • Other conduction abnormalities
   • Hemodynamic instability
   • Extensive coronary disease affecting the right coronary artery

3. Post-operative management:

   • If new SND or AV block develops with persistent symptoms or hemodynamic instability that doesn't resolve, permanent pacing is recommended before discharge 1

Important Considerations

• In a study of 770 CABG patients, only 2.9% required pacing postoperatively 2
• Some evidence suggests OPCAB (off-pump CABG) may be associated with reduced requirement for pacing wires compared to conventional CABG 3
• Temporary biventricular pacing has been studied in patients with reduced left ventricular function undergoing CABG and appears feasible and safe 4

Potential Pitfalls

1. Overuse of temporary pacing wires:

   • Studies show that routine placement may be unnecessary in many cases 2, 3
   • In one study, when selective criteria were used, no patients without pacing wires required postoperative pacing 3

2. Complications of temporary pacing wires:

   • Bleeding
   • Tamponade
   • Rare mortality

3. Misinterpretation of ECG patterns:

   • RBBB pattern during RV pacing may be misinterpreted as lead malposition or perforation, when it could be a normal variant 5

In conclusion, while routine placement of temporary epicardial pacing wires is reasonable for all CABG patients per guidelines, there is no specific indication that patients with pre-existing RBBB require special consideration for external lead placement beyond standard practice.