3.1 Myocardial Infarction (MI) – Coronary Artery Thrombosis

📘 Cross-reference: [See Section 2 – Acute Coronary Syndromes (ACS)] https://passmap.co.uk/cardiology-1-acute-coronoary-syndromes/ for full clinical approach, ECG patterns, biomarkers, and guideline-driven management.

📄 Definition

Myocardial infarction (MI) is myocardial necrosis due to acute thrombotic occlusion of a coronary artery. It is a clinical manifestation of arterial thrombosis and a common cause of sudden cardiac death.

🔬 Pathophysiology

  • Triggered by rupture of an atherosclerotic plaque in a coronary artery.

  • Results in platelet aggregation and formation of a white thrombus in high-pressure arterial flow.

  • Thrombus partially or completely occludes the coronary artery:

    • Partial occlusion → NSTEMI

    • Complete occlusion → STEMI

  • Leads to ischaemia, hypoxia, and myocyte death.

🧠 PASSMAP Integration

This condition is the archetype of arterial thrombosis and integrates with systemic atherosclerosis. Recognising shared risk factors with PAD, stroke, and acute limb ischaemia is high-yield for PARA success.

⚠️ Risk Factors – Mnemonic: THROMBUS

  • Tobacco use

  • Hypertension

  • Raised lipids

  • Obesity

  • Male sex / Metabolic syndrome

  • Blood glucose (diabetes mellitus)

  • Unhealthy diet / sedentary lifestyle

  • Stress / psychosocial factors

🩺 Red Flag Signs (pre-hospital recognition)

  • Crushing central chest pain ± radiation to arm/jaw

  • Sweating, nausea, breathlessness

  • Syncope or hypotension

  • Sudden collapse or cardiac arrest

🧪 Investigations

✅ Full workup found in Section 2 (ACS), but key mechanistic markers include:

  • Troponin T or I – indicates myocardial necrosis

  • ECG – ST elevation (STEMI) or T wave changes/ST depression (NSTEMI)

  • Coronary angiography – to confirm thrombotic occlusion

Mechanism-Based Management Highlights

🧠 Refer to ACS section for comprehensive protocol, but note:

  • Antiplatelet therapy (Aspirin + P2Y12 inhibitor) targets arterial thrombosis

  • Anticoagulation (e.g. fondaparinux) in NSTEMI

  • Thrombolysis if PCI not available within 120 minutes (STEMI)

  • PCI (Percutaneous Coronary Intervention) – definitive treatment

  • Statins + ACE-i/ARB + Beta-blockers post-event

Long-Term Considerations

  • Lifestyle modification

  • Cardiac rehabilitation

  • Antiplatelets and statins long-term

  • Risk factor optimisation (BP, glucose, lipids)

🔺 Last updated in line with NICE CG167 (STEMI) & NG185 (NSTEMI & UA)

Published: July 2013 & October 2020 • Last updated: July 2023
Last reviewed: August 2025
✅ PASSMAP ensures all content is NICE-aligned and reviewed for Physician Associate Registration Assessment (PARA) success.

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