Do beta (β) blockers reduce mortality after myocardial infarction (MI)?

Beta-Blockers Significantly Reduce Mortality After Myocardial Infarction

Beta-blockers should be prescribed to all patients who have experienced a myocardial infarction (MI) without contraindications, as they reduce mortality by 20-25% and should be continued indefinitely. 1

Evidence for Beta-Blocker Use Post-MI

Beta-blockers provide substantial mortality benefits after MI through several mechanisms:

• Decrease myocardial oxygen demand by reducing heart rate, blood pressure, and contractility
• Reduce cardiac automaticity and risk of ventricular fibrillation
• Improve coronary perfusion by prolonging diastole
• Provide anti-ischemic effects

A systematic review of randomized controlled trials including 54,234 patients demonstrated that beta-blockers are effective in secondary prevention after MI, with a 23% reduction in the odds of death in long-term trials 1. The CAPRICORN trial specifically showed that carvedilol reduced all-cause mortality by 23% (95% CI 2-40%, p=0.03) in post-MI patients with left ventricular dysfunction 2.

Specific Benefits

Beta-blockers provide multiple protective effects after MI:

• 20-25% reduction in mortality and reinfarction 1
• 23% reduction in odds of death in long-term trials 1
• Significant reduction in sudden cardiac death 1, 3
• 40% reduction in fatal or non-fatal myocardial reinfarction with carvedilol 2

Recommended Agents

For patients with MI complicated by left ventricular systolic dysfunction (LVSD), the following beta-blockers have proven mortality benefits:

• Bisoprolol
• Carvedilol
• Extended-release metoprolol succinate 1

For patients without LVSD, lipophilic beta-blockers (timolol, metoprolol, propranolol) have shown the most consistent benefits in reducing sudden cardiac death 3.

Duration of Therapy

The AHA/ACC guidelines recommend:

• Beta-blockers should be prescribed at hospital discharge for all MI patients without contraindications 1
• Treatment should continue indefinitely in patients who tolerate therapy 1
• While some guidelines suggest a 3-year minimum treatment course for uncomplicated MI, many patients have indications for continued therapy (hypertension, heart failure) 1

Contraindications and Cautions

Beta-blockers should not be used in patients with:

• Advanced heart block without a pacemaker
• Significant bradycardia or hypotension
• Active asthma or reactive airways disease
• Increased risk of heart failure/cardiogenic shock
• Recent cocaine or methamphetamine use with signs of acute intoxication 1

Implementation Strategy

1. Start beta-blocker therapy as soon as hemodynamically stable after MI
2. Begin with low doses and titrate gradually
3. For patients with LVSD, use one of the three proven agents (bisoprolol, carvedilol, extended-release metoprolol)
4. Monitor for bradycardia, hypotension, and worsening heart failure
5. Reassess patients with initial contraindications to determine subsequent eligibility
6. Continue therapy indefinitely in the absence of adverse effects

Common Pitfalls

Despite strong evidence, beta-blockers remain underutilized in post-MI patients. Common pitfalls include:

• Failure to prescribe at hospital discharge
• Inappropriate discontinuation during follow-up
• Using agents without proven mortality benefits
• Inadequate dose titration
• Not reassessing patients with initial contraindications
• Assuming beta-blockers are contraindicated in all patients with lung disease or diabetes

Beta-blockers should be considered a cornerstone of post-MI therapy along with antiplatelet agents and ACE inhibitors, as part of comprehensive secondary prevention.