Are beta blockers (beta-adrenergic blocking agents) helpful in patients with a history of coronary artery disease (CAD) who have undergone coronary artery bypass grafting (CABG) and have a permanent pacemaker?

Beta Blockers Post-CABG with Permanent Pacemaker

Beta blockers should be prescribed to all CABG patients with permanent pacemakers at hospital discharge unless specific contraindications exist, as they reduce long-term mortality and prevent recurrent myocardial infarction. 1

Primary Recommendation

The presence of a permanent pacemaker does not constitute a contraindication to beta blocker therapy after CABG. 1 The ACC/AHA guidelines provide a Class I recommendation that beta blockers should be prescribed to all CABG patients without contraindications at the time of hospital discharge. 1 This recommendation is based on Canadian registry data showing reduced mortality over 75 months of follow-up in patients receiving beta blockers, with improved survival noted in all patient subgroups—even those without perioperative myocardial ischemia or heart failure. 1

Evidence for Long-Term Benefit

The most recent high-quality evidence demonstrates that ongoing treatment with cardioselective beta blockers after CABG reduces major adverse cardiovascular events, primarily through a 17% reduction in recurrent myocardial infarction risk. 2 This Swedish nationwide observational study of 35,184 CABG patients followed for a median of 5.2 years found that cardioselective beta blockers were associated with reduced MACEs (HR 0.93,95% CI 0.89-0.98) and MI (HR 0.83,95% CI 0.75-0.92). 2 Importantly, this benefit was consistent across all subgroups, including patients with and without previous MI, heart failure, atrial fibrillation, or reduced LVEF. 2

Specific Considerations for Pacemaker Patients

Why Pacemakers Are Not a Contraindication

• Beta blockers can cause bradycardia, heart block, and sinus node dysfunction, which are listed as warnings in the FDA label. 3
• However, patients with permanent pacemakers are protected from symptomatic bradycardia because the device provides backup pacing. 3
• The pacemaker eliminates the primary safety concern that would otherwise limit beta blocker use in patients with conduction system disease. 3

Actual Contraindications to Monitor

Left ventricular ejection fraction <30% is the most critical contraindication to assess. 1, 4 The guidelines note that the effectiveness of beta blockers in reducing in-hospital mortality in patients with LVEF <30% is uncertain (Class IIb). 1

Other absolute contraindications include: 3

• Active decompensated heart failure or cardiogenic shock
• Severe bronchospastic disease unresponsive to other treatments
• Pheochromocytoma without concurrent alpha blockade

Perioperative Management Algorithm

Immediate Postoperative Period (0-48 hours)

1. Reinstitute beta blockers as soon as possible after CABG (Class I recommendation). 1, 4
2. For patients unable to take oral medications, intravenous administration is reasonable in clinically stable patients (Class IIa). 1
3. Continuous ECG monitoring must be performed for at least 48 hours to detect arrhythmias. 4, 5
4. Maintain mean arterial pressure >60 mm Hg, particularly in patients with preexisting renal dysfunction. 4, 5

Hospital Discharge

Beta blockers should be prescribed at discharge to all CABG patients without contraindications (Class I, Level of Evidence C). 1, 4 The preferred agents are cardioselective beta blockers: carvedilol, metoprolol succinate, or bisoprolol, which have been shown to reduce mortality. 1

Long-Term Continuation

• Continue beta blockers indefinitely for patients with LV systolic dysfunction (EF ≤40%) with heart failure or prior MI (Class I, Level of Evidence A). 1
• Continue for at least 3 years in patients with normal LV function who have had MI or ACS (Class I, Level of Evidence B). 1
• It is reasonable to continue >3 years as chronic therapy in all patients with normal LV function (Class IIa, Level of Evidence B). 1

Additional Benefits Beyond Mortality

Beta blockers provide multiple benefits in the post-CABG population: 1

• Reduce incidence and clinical sequelae of postoperative atrial fibrillation (Class I indication for perioperative use)
• Decrease perioperative myocardial ischemia (Class IIa, Level of Evidence B)
• Reduce in-hospital mortality, particularly in patients with LVEF >30% (Class IIa, Level of Evidence B)

Common Clinical Pitfalls

Pitfall 1: Withholding Beta Blockers Due to Pacemaker Presence

The pacemaker provides rate support, making bradycardia concerns largely irrelevant. 3 Do not withhold beta blockers solely because a pacemaker is present.

Pitfall 2: Abrupt Discontinuation

Never abruptly discontinue beta blockers in patients with coronary artery disease. 3 The FDA label warns that severe exacerbation of angina, myocardial infarction, and ventricular arrhythmias have been reported following abrupt discontinuation. 3 When discontinuation is necessary, taper gradually over 1-2 weeks with careful monitoring. 3

Pitfall 3: Inadequate Dosing

The Swedish study found that 73.7% of patients were still on cardioselective beta blockers at 10 years, suggesting significant discontinuation rates. 2 Ensure adequate dosing and adherence to maximize benefit.

Pitfall 4: Focusing Only on Atrial Fibrillation Prevention

While beta blockers reduce postoperative AF, the primary long-term benefit is reduction in recurrent MI and mortality. 2, 6 One older study found no difference in AF rates between metoprolol and placebo when using a titrated dosing algorithm, 7 and another suggested carvedilol may be superior to metoprolol for AF prevention. 8 However, the mortality and MI benefits are consistent across cardioselective beta blockers. 2

Coordination with Other Post-CABG Medications

Beta blockers should be part of comprehensive guideline-directed medical therapy: 4, 9, 5

• Aspirin should be initiated within 6 hours postoperatively and continued indefinitely
• Statins must never be discontinued perioperatively (Class III: HARM to stop)
• ACE inhibitors or ARBs should be reinstituted once the patient is stable