Is there still a beneficial effect from beta blockers (beta-adrenergic blocking agents) after a myocardial infarction (MI) in patients with a heart block and a pacemaker?

Beta Blockers After MI in Patients with Heart Block and Pacemaker

Beta blockers should still be used in patients with a history of myocardial infarction who have heart block and a pacemaker, as they provide significant mortality benefit and are not contraindicated in this population. 1

Benefits of Beta Blockers Post-MI

Beta blockers provide several important benefits after myocardial infarction:

• Reduce mortality and reinfarction by 20-25% in post-MI patients 1, 2
• Decrease myocardial oxygen demand by reducing heart rate, blood pressure, and contractility 1
• Reduce cardiac automaticity and risk of ventricular fibrillation after MI 1
• Improve coronary perfusion by prolonging diastole 1
• Provide greatest benefit in patients with MI complicated by heart failure, systolic cardiomyopathy, or ventricular arrhythmias 1

Beta Blockers in Patients with Heart Block and Pacemaker

The presence of a pacemaker in a patient with heart block specifically addresses what would otherwise be a contraindication to beta blocker therapy:

• Advanced heart block without a pacemaker is listed as a contraindication to beta blockers 1, 3
• However, the presence of a pacemaker removes this contraindication, as the pacemaker provides protection against bradycardia 1
• The 2017 AHA/ACC guidelines specifically list "advanced heart block and no pacemaker" as a contraindication, implying that with a pacemaker, beta blockers can be used 1

Recommended Beta Blockers Post-MI

For patients with MI, particularly those with left ventricular systolic dysfunction (LVSD), the following beta blockers are recommended:

• Bisoprolol 1
• Carvedilol 1
• Extended-release metoprolol succinate 1

Duration of Therapy

• AHA/ACCF secondary prevention guidelines recommend at least a 3-year treatment course with beta blockers for patients with uncomplicated MI 1
• Many patients, particularly those with hypertension or heart failure/systolic cardiomyopathy, are usually continued on beta blockers indefinitely 1
• Evidence from all available studies suggests beta blockers should be used indefinitely in all patients who recovered from an MI and without contraindications 1

Special Considerations

• Start with lower doses and titrate gradually in patients with a pacemaker to monitor for any adverse effects 1
• Monitor for hypotension, which can still occur even with a pacemaker in place 1
• Beta blockers without intrinsic sympathomimetic activity are preferred 1
• Patients with initial contraindications to beta blockers in the first 24 hours after MI should be reevaluated to determine their subsequent eligibility 1

Strength of Evidence

The evidence for beta blocker use after MI is robust:

• A systematic review of randomized controlled trials including 54,234 patients demonstrated beta blockers are effective in secondary prevention after MI with a 23% reduction in the odds of death in long-term trials 1
• A meta-analysis of 82 randomized trials provides strong evidence for long-term use of beta blockers to reduce morbidity and mortality after MI 1
• Even in patients traditionally considered high-risk (including elderly and those with various comorbidities), beta blockers have shown mortality benefit 4

Conclusion

The presence of heart block with a pacemaker should not preclude the use of beta blockers after MI. The pacemaker effectively addresses the heart block contraindication, allowing these patients to receive the mortality benefit of beta blocker therapy. The choice of beta blocker and dosing should be carefully selected, with appropriate monitoring for adverse effects.