Should bisoprolol fumarate be reduced in a patient with intermittent Mobitz Type 1 second-degree atrioventricular block and bradycardia?

Management of Bisoprolol in a Patient with Mobitz Type I Second-Degree AV Block

Bisoprolol should be reduced in this 81-year-old patient with intermittent Mobitz Type I second-degree AV block, bradycardia, and HFrEF. 1

Rationale for Dose Reduction

The FDA drug label for bisoprolol explicitly states that it is contraindicated in second-degree AV block 1. While this contraindication is more strictly applied to Mobitz Type II AV block (which has a higher risk of progression to complete heart block), the patient's clinical presentation raises several concerns:

1. Bradycardia: The patient has documented bradycardia with heart rate as low as 31 bpm and a 2.7-second pause
2. First-degree AV block with intermittent Mobitz Type I: This suggests significant conduction system disease
3. Symptoms: Patient reports ongoing mild fatigue which may be related to bradycardia

Evidence-Based Approach

The 2018 ACC/AHA/HRS guidelines on bradycardia and cardiac conduction delay provide relevant guidance 2:

• Mobitz Type I second-degree AV block is generally considered less dangerous than Mobitz Type II
• However, when Mobitz Type I is accompanied by symptoms that are clearly attributable to the AV block, permanent pacing may be reasonable (Class IIa recommendation) 2

Beta-blockers like bisoprolol can worsen AV conduction abnormalities and exacerbate bradycardia. The drug label specifically warns about this risk 1.

Management Algorithm

1. Reduce bisoprolol dose:

   • Decrease from current 10 mg daily to 5 mg daily
   • Monitor heart rate and symptoms after dose reduction
   • If bradycardia persists with symptoms, consider further reduction to 2.5 mg daily

2. Monitor for improvement:

   • Reassess heart rate and AV conduction with ECG in 1-2 weeks
   • If bradycardia resolves and symptoms improve, maintain the reduced dose
   • If symptoms persist despite dose reduction, consider complete discontinuation

3. Consider alternative beta-blockers:

   • If beta-blockade is still needed for HFrEF but bradycardia persists
   • Consider switching to a beta-blocker with less AV nodal effects (e.g., metoprolol)

4. Evaluate need for permanent pacing:

   • If significant bradycardia or AV block persists despite medication adjustment
   • Especially if the patient has clear symptoms attributable to bradycardia
   • According to guidelines, symptomatic Mobitz Type I may warrant permanent pacing 2

Important Considerations

• HFrEF management: The patient has HFrEF (EF 45%) and is on guideline-directed medical therapy (GDMT) including Entresto, empagliflozin, and bisoprolol. Beta-blockers are a cornerstone of HFrEF therapy, so complete discontinuation should be avoided if possible.

• Risk of progression: While Mobitz Type I is typically less concerning than Mobitz Type II, the patient's advanced age and cardiac history (CAD s/p CABG, prosthetic valve repair) increase the risk of progression to higher-degree AV block.

• Monitoring: Close follow-up is essential after dose reduction to ensure the patient doesn't develop worsening heart failure symptoms due to reduced beta-blockade.

Pitfalls to Avoid

1. Complete discontinuation without monitoring: Abrupt discontinuation of beta-blockers can lead to rebound tachycardia and worsening heart failure.

2. Ignoring the conduction abnormality: Continuing high-dose bisoprolol despite documented conduction abnormalities could lead to complete heart block.

3. Attributing all symptoms to age/deconditioning: The patient's fatigue may be related to bradycardia and should improve with appropriate management.

4. Overlooking the need for pacing: If symptoms and conduction abnormalities persist despite medication adjustment, permanent pacing should be considered rather than continuing to adjust medications.