What treatment will most likely reduce mortality risk in a patient with acute myocardial infarction (AMI)?

Beta-Blockers for Acute Myocardial Infarction

Metoprolol is the treatment that will most likely reduce mortality risk in this patient with acute myocardial infarction (AMI) presenting with ST-segment elevation. 1, 2

Rationale for Beta-Blocker Therapy

Beta-blockers have consistently demonstrated mortality reduction in patients with acute myocardial infarction across multiple clinical trials and guidelines. The ACC/AHA guidelines specifically recommend early intravenous beta-blocker therapy followed by oral therapy for patients with evolving acute MI, regardless of whether reperfusion therapy was given 1.

Key benefits of beta-blockers in AMI include:

• 20-25% reduction in mortality and reinfarction in post-MI patients 3
• Reduction in the incidence of ventricular fibrillation 1, 4
• Decreased myocardial oxygen demand by reducing heart rate, blood pressure, and contractility 1
• Significant mortality reduction when initiated within the first 24 hours in hemodynamically stable patients 3

Evidence for Metoprolol in AMI

The Göteborg Metoprolol Trial demonstrated a 36% reduction in 3-month mortality when metoprolol was administered early (within 12 hours) to patients with suspected acute MI 5. This landmark study showed that:

• Mortality was reduced from 8.9% in the placebo group to 5.7% in the metoprolol group
• Benefits persisted regardless of age, previous infarction, or previous beta-blockade
• Fewer episodes of ventricular fibrillation occurred in the metoprolol group

The FDA label for metoprolol specifically indicates its use in hemodynamically stable patients with definite or suspected acute myocardial infarction to reduce cardiovascular mortality 2.

Clinical Application for This Patient

For this 55-year-old man with:

• Substernal chest pain radiating to left arm and jaw for 2 hours
• ST-segment elevation in leads II, III, and aVF (indicating inferior MI)
• Risk factors including diabetes, obesity, and hyperlipidemia

Metoprolol is the optimal choice because:

1. The patient is hemodynamically stable (no mention of hypotension or heart failure)
2. The ST-segment elevation indicates an acute STEMI where early beta-blockade has proven mortality benefit
3. The patient's presentation is within the timeframe where beta-blockers show maximum benefit

Comparison with Other Options

• Captopril (ACE inhibitor): While beneficial in AMI, ACE inhibitors have shown less immediate mortality reduction compared to beta-blockers in the acute phase 1
• Dipyridamole: Not recommended in current guidelines for acute MI management
• Nifedipine (calcium channel blocker): Potentially harmful in acute MI; guidelines specifically warn against calcium channel blockers with negative inotropic effects 1
• Warfarin: Not indicated for immediate management of acute MI; may have role in long-term therapy for selected patients 1

Implementation

The recommended dosing for metoprolol in acute MI 2:

1. Initial treatment: Three bolus injections of 5 mg IV metoprolol at approximately 2-minute intervals
2. Follow with oral metoprolol 50 mg every 6 hours for 48 hours
3. Maintenance dose: 100 mg orally twice daily

Cautions

Beta-blockers should be used with caution in patients with:

• Heart rate less than 60 bpm
• Systolic blood pressure less than 100 mmHg
• Moderate or severe left ventricular failure
• AV block or severe bradycardia
• Severe COPD or asthma 1

This patient has none of these contraindications based on the information provided.