Can I give Lopressor (metoprolol) in STEMI (ST-elevation myocardial infarction)?

Metoprolol in STEMI: Evidence-Based Administration Guidelines

Intravenous metoprolol can be given in STEMI, but only to hemodynamically stable patients who are hypertensive or have ongoing ischemia, and who do not have contraindications such as heart failure, low cardiac output, risk of cardiogenic shock, or other beta-blocker contraindications. 1

Patient Selection for IV Metoprolol in STEMI

When to Use IV Metoprolol:

• Only in hemodynamically stable STEMI patients
• Particularly beneficial in patients with:
  • Hypertension at presentation
  • Ongoing ischemia
  • Tachyarrhythmias

Absolute Contraindications (Do NOT Use):

• Signs of heart failure
• Evidence of low cardiac output state
• Increased risk for cardiogenic shock:
  • Age >70 years
  • Systolic BP <120 mmHg
  • Heart rate >110 bpm or <60 bpm
  • Increased time since symptom onset
• PR interval >0.24 seconds
• Second or third-degree heart block
• Active asthma or reactive airway disease

Administration Protocol for IV Metoprolol in STEMI

Dosing:

• Three bolus injections of 5 mg IV metoprolol given approximately 2 minutes apart (total 15 mg) 2
• Monitor blood pressure, heart rate, and ECG during administration
• If patient tolerates the full IV dose (15 mg), initiate oral metoprolol 50 mg every 6 hours, starting 15 minutes after the last IV dose 2
• Continue oral dosing for 48 hours, then transition to maintenance dose of 100 mg twice daily 2

For Patients with Partial Intolerance:

• If patient cannot tolerate the full IV dose, start oral metoprolol at either 25 mg or 50 mg every 6 hours (depending on degree of intolerance) 2
• Begin oral dosing 15 minutes after the last IV dose or as soon as clinical condition allows

Evidence and Rationale

The 2013 ACCF/AHA guidelines for STEMI management (Class IIa recommendation) support the use of IV beta-blockers at presentation for hypertensive patients without contraindications 1. This represents a shift from earlier guidelines that more broadly recommended IV beta-blockers.

This change was based on the COMMIT/CCS-2 trial, which showed that while early IV metoprolol followed by oral therapy reduced recurrent MI and ventricular fibrillation, it increased the risk of cardiogenic shock, particularly in high-risk patients during the first 24 hours 1.

More recent evidence from the METOCARD-CNIC trial suggests that early IV metoprolol before primary PCI in anterior STEMI patients without contraindications can reduce infarct size and improve left ventricular ejection fraction 3. This study showed a significant reduction in infarct size (25.6g vs 32.0g) and higher LVEF in patients receiving early IV metoprolol.

Alternative Approach: Oral Beta-Blockers

For STEMI patients who don't meet criteria for IV metoprolol but have no contraindications to beta-blockers:

• Initiate oral beta-blockers within the first 24 hours (Class I recommendation) 1
• Continue beta-blockers during and after hospitalization 1

Important Clinical Pitfalls

1. Avoid IV beta-blockers in patients with risk factors for cardiogenic shock - this can significantly increase mortality
2. Monitor closely for hemodynamic deterioration - be prepared to discontinue therapy if signs of heart failure or hypotension develop
3. Don't delay primary PCI to administer beta-blockers - reperfusion remains the priority
4. Reassess patients with initial contraindications - they may become candidates for beta-blocker therapy as secondary prevention later in their course 1
5. For patients with LV dysfunction - initiate beta-blockers for secondary prevention using a gradual titration scheme 1

By carefully selecting appropriate candidates and following evidence-based administration protocols, metoprolol can be safely used in STEMI management to reduce recurrent ischemia and improve outcomes.