What is the management of a patient presenting with inferior wall ST-elevation myocardial infarction (STEMI)?

Management of Inferior Wall STEMI

Immediate Reperfusion Strategy

Primary PCI is the definitive treatment for inferior wall STEMI and must be performed within 90-120 minutes of first medical contact, with patients transferred directly to the catheterization laboratory bypassing the emergency department. 1

• 12-lead ECG must be obtained and interpreted within 10 minutes of first medical contact, with continuous ECG monitoring and defibrillator capacity immediately available. 1
• Right-sided ECG leads (V3R-V4R) are mandatory in all inferior STEMI patients to screen for ST elevation suggestive of right ventricular infarction, which occurs in approximately 30-50% of inferior STEMIs and dramatically alters hemodynamic management. 1
• If primary PCI cannot be performed within 120 minutes of STEMI diagnosis, fibrinolytic therapy must be initiated within 10 minutes using a fibrin-specific agent (tenecteplase preferred as single weight-adjusted bolus, or alteplase/reteplase). 1, 2

Pre-Hospital and Transport Logistics

• Emergency Medical Services should diagnose STEMI in the field and activate the catheterization laboratory before hospital arrival, transporting patients directly to PCI-capable centers 24/7. 1
• Direct transport to the catheterization laboratory reduces door-to-balloon time by approximately 27 minutes compared to emergency department evaluation first. 3
• The systems goal is first medical contact-to-balloon time ≤90 minutes for PCI-capable hospitals. 1

Immediate Pharmacotherapy

Antiplatelet Therapy

Aspirin 150-325 mg oral (chewable) or IV must be administered immediately as soon as STEMI is diagnosed, with no contraindications in uncomplicated inferior STEMI. 1, 4

For P2Y12 inhibitor selection:

• Ticagrelor 180 mg loading dose is preferred (then 90 mg twice daily), given before or at the time of PCI. 1, 4, 5
• Prasugrel 60 mg loading dose (then 10 mg daily) is an alternative if no prior stroke/TIA and age <75 years. 1, 6
• Clopidogrel 300-600 mg loading dose only if ticagrelor and prasugrel are unavailable or contraindicated. 1

Critical pitfall: Prasugrel is contraindicated in patients with any prior stroke or TIA (even remote history), as stroke risk increases to 6.5% versus 1.2% with clopidogrel. 6

Anticoagulation

For primary PCI: Unfractionated heparin as weight-adjusted IV bolus (70-100 units/kg) followed by infusion is the standard anticoagulant. 1, 7 Bivalirudin or enoxaparin are acceptable alternatives. 1, 5

For fibrinolytic therapy: Enoxaparin IV bolus (30 mg) followed by subcutaneous (1 mg/kg every 12 hours) is preferred over unfractionated heparin, continued until revascularization or up to 8 days. 1, 2

Special Considerations for Inferior STEMI

Right Ventricular Infarction

When right-sided ECG shows ST elevation in V3R-V4R (present in 30-50% of inferior STEMIs):

• Avoid nitrates, diuretics, and morphine as they cause profound hypotension by reducing preload in RV-dependent hemodynamics. 1
• Aggressive IV fluid resuscitation (500-1000 mL normal saline boluses) is first-line for hypotension. 1
• Maintain AV synchrony as atrial contribution to ventricular filling is critical; consider temporary pacing for high-degree AV block. 1

Atrioventricular Block

Complete heart block occurs in 10-20% of inferior STEMIs due to RCA occlusion affecting AV nodal blood supply:

• Immediate reperfusion with PCI can restore normal conduction even in late presentations (>72 hours), potentially avoiding permanent pacemaker. 8
• Temporary transvenous pacing is indicated for symptomatic bradycardia or hemodynamic instability, but reperfusion is the definitive treatment. 8
• Most AV blocks resolve within 24-48 hours after successful reperfusion. 8

Post-Fibrinolytic Management (Pharmacoinvasive Strategy)

If fibrinolytic therapy is administered due to PCI delay:

• Transfer to PCI-capable center must be initiated immediately after fibrinolysis without waiting to assess reperfusion success. 1, 2
• Rescue PCI is indicated immediately if <50% ST-segment resolution at 60-90 minutes, or any hemodynamic/electrical instability. 1, 2
• Routine angiography and PCI of the infarct-related artery should be performed 2-24 hours after successful fibrinolysis, reducing mortality by 38% and reinfarction by 41%. 1, 2, 9

Post-Reperfusion Care

• Dual antiplatelet therapy (aspirin 75-100 mg daily plus ticagrelor 90 mg twice daily) must continue for 12 months unless excessive bleeding risk develops. 1, 4
• High-intensity statin therapy (atorvastatin 80 mg or rosuvastatin 40 mg) should be initiated immediately with target LDL-C <70 mg/dL. 4
• Routine echocardiography during hospitalization is mandatory to assess LV/RV function, detect mechanical complications (papillary muscle rupture, ventricular septal defect), and exclude LV thrombus. 1, 4

Critical Pitfalls to Avoid

• Never delay reperfusion therapy to obtain additional imaging or consultations—every 30-minute delay increases mortality. 1, 7
• Never administer nitrates if RV infarction is suspected or confirmed—this causes catastrophic hypotension. 1, 7
• Never use prasugrel in patients ≥75 years, <60 kg body weight, or any prior stroke/TIA history due to increased fatal bleeding risk. 6
• Never withhold aspirin or P2Y12 inhibitors due to perceived bleeding risk in uncomplicated STEMI—untreated STEMI has immediate high mortality that far exceeds bleeding risk. 4