What is the management plan for a patient with an inferior ST-elevation myocardial infarction (STEMI)?

Management of Inferior ST-Elevation Myocardial Infarction

Primary percutaneous coronary intervention (PCI) is the preferred reperfusion strategy for inferior STEMI if door-to-balloon time can be achieved within 90 minutes; if not achievable within 120 minutes of first medical contact, administer fibrinolytic therapy within 30 minutes. 1, 2, 3

Immediate Diagnosis and Assessment

ECG Diagnosis

• Obtain a 12-lead ECG within 10 minutes of presentation showing ST-segment elevation ≥1 mm (0.1 mV) in at least two contiguous inferior leads (II, III, aVF) 1, 2
• Critically important: Obtain right-sided ECG leads (V3R-V4R) in all inferior STEMIs to screen for right ventricular (RV) infarction, which complicates 30-50% of cases and carries 25-31% in-hospital mortality 1, 2

Initial Prehospital Management

• Patients should chew non-enteric-coated aspirin 162-325 mg immediately unless contraindicated 1
• Emergency Medical Services should obtain prehospital 12-lead ECG and activate the cardiac catheterization laboratory directly, which significantly reduces door-to-balloon times and mortality 1
• Transport directly to a PCI-capable center rather than the nearest hospital if interhospital transfer would subsequently be required 1

Reperfusion Strategy Algorithm

Primary PCI (Preferred Strategy)

Primary PCI should be performed if first medical contact-to-device time can be achieved within 90 minutes (lowered from the previous 120-minute goal to maximize myocardial salvage) 1, 2, 3

• The mortality benefit of PCI over fibrinolysis exists only when treatment is delayed by no more than 60 minutes 1
• Every 15-minute delay in door-to-balloon time significantly increases mortality 1
• Time from symptom onset to balloon inflation correlates with 1-year mortality (relative risk 1.08 for each 30-minute delay) 1

Fibrinolytic Therapy (When PCI Unavailable)

If expected door-to-balloon time exceeds 120 minutes from first medical contact, administer fibrinolytic therapy within 30 minutes, particularly if symptom duration is less than 3 hours when more myocardium can be salvaged 1, 2, 3

• Fibrin-specific agents (tenecteplase, alteplase) are preferred 1
• The previously recommended "facilitated PCI" strategy (full-dose fibrinolysis followed by routine PCI) is harmful and no longer recommended 1
• After fibrinolysis, transfer for urgent angiography if failed reperfusion, reocclusion, or as part of an invasive strategy within 3-24 hours 1

Adjunctive Pharmacotherapy

Antiplatelet Therapy

• Dual antiplatelet therapy with aspirin (75-325 mg daily) plus a potent P2Y12 inhibitor should be administered before or at the time of PCI 3, 4
• Ticagrelor or prasugrel are strongly preferred over clopidogrel for superior outcomes 3, 4
• Critical caveat: Prasugrel is generally not recommended in patients ≥75 years except in high-risk situations (diabetes or prior MI) due to increased fatal/intracranial bleeding risk 3, 5
• For patients <60 kg, consider prasugrel 5 mg daily instead of 10 mg 5

Glycoprotein IIb/IIIa Inhibitors

• Abciximab has demonstrated added value for STEMI patients undergoing primary PCI, particularly for addressing thrombo-embolic complications 6

Anticoagulation

• Bivalirudin is supported by multiple trials as an effective anti-thrombin agent for PCI that does not stimulate platelets 6, 4

Critical Complication: Right Ventricular Infarction

This is the single most dangerous pitfall in inferior STEMI management—RV infarction requires completely opposite hemodynamic management from standard STEMI care.

Recognition

• ST-segment elevation ≥1 mm in right-sided lead V4R is diagnostic 1, 2
• Clinical signs: hypotension, elevated jugular venous pressure, clear lung fields (the triad) 2

Management

• Aggressive volume resuscitation with IV normal saline is the single most important initial intervention, with a goal of maintaining elevated right-sided filling pressure 2
• Absolutely avoid nitrates, diuretics, and morphine—these cause catastrophic hypotension by reducing preload 2
• Never use beta-blockers or calcium channel blockers acutely in RV infarction 1
• If hypotension persists despite volume loading, initiate vasopressor support and consider intra-aortic balloon pump (IABP) 1

Management of Conduction Abnormalities

Atrioventricular Block

• Transient AV block (including complete heart block) is relatively common in inferior STEMI and typically resolves with successful reperfusion 7, 8
• First-line management: correct rhythm disturbances causing hypotension immediately 1
• Temporary transvenous pacing is indicated for symptomatic bradycardia or complete heart block 7, 8
• Conservative management with temporary pacing for 5-7 days is appropriate before considering permanent pacemaker, as most cases resolve after successful reperfusion 7, 8
• Reperfusion strategy (even in late presentation >72 hours) may prevent need for permanent pacemaker in patients with advanced AV block 7

Cardiogenic Shock Management

Patients with inferior STEMI and cardiogenic shock require immediate transport to a facility capable of cardiac catheterization and rapid revascularization (PCI or CABG). 1

Hemodynamic Support

• Rapid volume loading with IV infusion for patients without volume overload 1
• Vasopressor support for hypotension not resolving after volume loading 1
• IABP should be performed in patients who do not respond to pharmacological interventions 1, 3
• Echocardiography to evaluate mechanical complications (papillary muscle rupture, ventricular septal rupture, free wall rupture) 1

Revascularization

• Early revascularization (PCI or CABG) is strongly recommended for patients <75 years who develop shock within 36 hours of MI, when revascularization can be performed within 18 hours of shock onset 1
• For selected patients ≥75 years with good prior functional status, early revascularization is reasonable 1
• Emergency CABG is indicated for failed PCI with persistent pain/hemodynamic instability or at time of mechanical complication repair 3

Secondary Prevention

Medications to Continue Indefinitely

• ACE inhibitors should be initiated within 24 hours in all patients, particularly those with anterior extension, heart failure, or ejection fraction ≤0.40 3
• Oral beta-blockers should be continued indefinitely in all eligible patients 3
• High-intensity statin therapy 3
• Dual antiplatelet therapy duration per guidelines (typically 12 months minimum) 3

Common Pitfalls to Avoid

1. Most dangerous error: Treating RV infarction like standard STEMI—giving nitrates, diuretics, or morphine causes catastrophic hypotension. Always obtain right-sided ECG in inferior STEMI. 1, 2

2. Never delay reperfusion therapy to wait for cardiac biomarker results—the diagnosis is secure with ST-segment elevation on ECG 1

3. Do not use facilitated PCI (full-dose fibrinolysis followed by routine PCI)—this strategy is harmful 1

4. Avoid beta-blockers or calcium channel blockers in acute setting with frank cardiac failure, pulmonary congestion, or signs of low-output state 1

5. Premature discontinuation of antiplatelet therapy dramatically increases risk of stent thrombosis, MI, and death 5

6. Do not start prasugrel in patients likely to undergo urgent CABG; when possible, discontinue at least 7 days prior to surgery 5

7. For late presentation (>72 hours) with advanced AV block, consider PCI even outside typical window to potentially avoid permanent pacemaker 7