How long should beta (beta blockers) therapy be continued after a myocardial infarction (MI)?

Duration of Beta-Blocker Therapy After Myocardial Infarction

Beta-blockers should be continued indefinitely in all patients who have had a myocardial infarction, particularly those with left ventricular dysfunction, unless contraindicated. 1

Evidence-Based Recommendations

General Recommendations

• Beta-blocker therapy should be started within a few days of the MI event (if not initiated acutely) and continued indefinitely in all patients who have had MI, acute coronary syndrome, or left ventricular dysfunction with or without heart failure symptoms, unless contraindicated 1
• The American College of Cardiology/American Heart Association guidelines specifically state that treatment with beta-blockers should begin within a few days of the event and continue indefinitely 1
• For patients with normal left ventricular function who have had MI or acute coronary syndrome, beta-blocker therapy should be started and continued for at least 3 years 1

Duration Based on Patient Characteristics

Patients with Left Ventricular Dysfunction (LVEF ≤40%)

• Beta-blocker therapy should be used in all patients with left ventricular systolic dysfunction (ejection fraction ≤40%) with heart failure or prior myocardial infarction indefinitely, unless contraindicated 1
• Preferred agents with mortality benefit include carvedilol, metoprolol succinate, or bisoprolol 1, 2

Patients with Normal Left Ventricular Function

• It is reasonable to continue beta-blockers beyond 3 years as chronic therapy in all patients with normal left ventricular function who have had myocardial infarction 1
• The European Heart Journal states that evidence from all available studies suggests beta blockers should be used indefinitely in all patients who recovered from an MI without contraindications 3

Benefits of Long-Term Beta-Blocker Therapy

• Beta-blockers provide significant mortality benefit and reduce reinfarction by 20-25% in post-MI patients 3, 4
• They decrease myocardial oxygen demand by reducing heart rate, blood pressure, and contractility 3
• Beta-blockers reduce cardiac automaticity and risk of ventricular fibrillation after MI 3
• They improve coronary perfusion by prolonging diastole 3
• The greatest benefit is seen in patients with MI complicated by heart failure, systolic cardiomyopathy, or ventricular arrhythmias 3

Emerging Evidence and Controversies

• More recent observational studies have questioned the benefit of long-term beta-blocker therapy beyond one year in patients with normal left ventricular function in the reperfusion era 5, 6
• A systematic review of observational studies found that the majority failed to demonstrate a benefit in survival or cardiovascular events with long-term beta-blockers in post-MI patients with normal left ventricular function 5
• A meta-analysis of five cohort studies including 217,532 patients showed that beta-blocker treatment for 1 year or more does not reduce mortality in MI patients without heart failure 6
• Three large ongoing multicenter randomized trials (AβYSS, REDUCE-SWEDEHEART, and REBOOT-CNIC) are evaluating early discontinuation of β-blockers after an uncomplicated acute MI 7

Clinical Decision Algorithm

1. For all MI patients: Start beta-blocker therapy within a few days of the event if not initiated acutely 1

2. For patients with LV dysfunction (LVEF ≤40%) or heart failure:

   • Continue beta-blocker therapy indefinitely 1
   • Use evidence-based agents: carvedilol, metoprolol succinate, or bisoprolol 1, 2

3. For patients with normal LV function:

   • Continue beta-blocker therapy for at least 3 years 1
   • Consider indefinite continuation, especially in patients with:
     • Hypertension 3, 4
     • History of arrhythmias 3
     • Ongoing angina symptoms 1, 8

Common Pitfalls and Caveats

• Don't discontinue beta-blockers abruptly as this may lead to rebound tachycardia and worsening ischemia 8
• Monitor for side effects such as fatigue, sexual dysfunction, and bronchospasm, which may affect adherence to long-term therapy 7
• Remember that the evidence for indefinite beta-blocker therapy in patients with preserved LV function is less robust in the modern reperfusion era 5, 6, 7
• Consider that the 2017 European Society of Cardiology guidelines downgraded the recommendation for the use of beta-blockers in post-MI patients to a class IIa B recommendation 7