What are the immediate management steps for a patient with ST elevation myocardial infarction (STEMI) indicated by telemetry monitoring showing ST changes in leads 2, 3, and AVF, with a recent 2.5-second pause?

Immediate Management of STEMI with ST Elevation in Leads II, III, AVF and 2.5-Second Pause

The patient requires immediate activation of a "fast-track" system with transfer to the catheterization laboratory for primary PCI within 90 minutes of first medical contact, along with continuous cardiac monitoring due to the inferior wall STEMI with evidence of conduction abnormality (2.5-second pause). 1

Initial Assessment and Stabilization

• Immediately initiate continuous ECG monitoring to detect further arrhythmias or conduction disturbances, as the 2.5-second pause indicates potential for more serious conduction abnormalities 1
• Administer oxygen only if the patient is hypoxemic (SaO₂ < 90% or PaO₂ < 60 mmHg), as routine oxygen is not recommended when SaO₂ ≥ 90% 1
• Provide pain relief with titrated intravenous opioids (morphine), recognizing that this may slow the uptake of oral antiplatelet agents 1
• Consider a mild tranquilizer (benzodiazepine) if the patient is anxious 1
• Obtain 12-lead ECG confirmation of the inferior STEMI (ST elevation in leads II, III, AVF) 1
• Obtain right-sided ECG leads (V3R-V6R) to assess for right ventricular involvement, which is common in inferior wall infarctions 1

Immediate Pharmacological Therapy

• Administer aspirin 160-325 mg orally immediately 1, 2
• Administer a P2Y12 inhibitor (ticagrelor or prasugrel preferred over clopidogrel if no contraindications) 1
• Initiate anticoagulation with unfractionated heparin, enoxaparin, or bivalirudin according to local protocol 1
• Consider beta-blockers with caution due to the presence of a conduction pause - monitor closely for worsening bradycardia or heart block 1

Reperfusion Strategy

• Alert the cardiac catheterization laboratory for immediate primary PCI, which should be performed within 90 minutes of first medical contact 1
• If primary PCI cannot be performed within 120 minutes, consider fibrinolytic therapy (if no contraindications) followed by transfer to a PCI-capable facility 2
• For patients with inferior STEMI and conduction abnormalities, primary PCI is strongly preferred over fibrinolysis when available within the recommended timeframe 1

Management of Conduction Abnormalities

• The 2.5-second pause requires close monitoring as it may indicate sinoatrial node dysfunction or developing heart block, which is common in inferior wall infarctions 1
• Have transcutaneous pacing capabilities immediately available 1
• If bradycardia is symptomatic or hemodynamically significant:
  • Administer atropine 0.5-1.0 mg IV (may repeat to a maximum of 3 mg) 1
  • If atropine is ineffective, initiate temporary transcutaneous pacing 1
  • Be prepared for temporary transvenous pacing if transcutaneous pacing is ineffective or poorly tolerated 1

Monitoring for Complications

• Monitor for right ventricular involvement, which occurs in up to 40% of inferior wall MIs and may require specific management (fluid administration, avoiding nitrates) 1
• Watch for signs of cardiogenic shock, which would require additional hemodynamic support 1
• Monitor for recurrent or worsening conduction abnormalities, as inferior MIs often affect the AV node 1
• Perform echocardiography to assess ventricular function and rule out mechanical complications 1

Common Pitfalls and Caveats

• Avoid nitrates in patients with inferior STEMI with suspected right ventricular involvement as they can cause profound hypotension 1
• Avoid excessive fluid administration in patients without right ventricular involvement as it may worsen left ventricular failure 1
• Do not delay reperfusion therapy while waiting for cardiac biomarker results when ECG shows clear ST-segment elevation 1
• Be cautious with beta-blockers and calcium channel blockers in the setting of conduction abnormalities, as they may worsen bradycardia or heart block 1