Case studies · Medicine · 20 October 2026

Acute myocardial infarction case study

The case

Patient: A 58‑year‑old man, Mr R, presents to the emergency department (ED) with chest discomfort.

Presenting complaint: Central, crushing chest pain radiating to the left arm and jaw, onset 45 minutes ago while he was climbing stairs. He describes the pain as 9/10 in intensity, continuous, and associated with diaphoresis, nausea, and a sense of impending doom.

History of present illness:

• No prior episodes of similar pain.
• The pain began abruptly, peaked within 5 minutes, and has not subsided despite resting.
• He attempted self‑medication with sublingual nitroglycerin (0.4 mg) en route to the hospital; the pain persisted.

Past medical history:

• Hypertension for 12 years, on amlodipine 10 mg daily.
• Dyslipidaemia, on atorvastatin 40 mg nightly.
• Smoker: 20 pack‑years, currently 1 pack/day.
• No known diabetes, coronary artery disease, or prior revascularisation.

Family history: Father died of myocardial infarction at 62 years; mother has hypertension.

Social history: Works as a sales manager, sedentary lifestyle, occasional alcohol (2–3 drinks/week).

Review of systems: Denies dyspnoea at rest, orthopnoea, palpitations, syncope, fever, cough, or recent infections.

Examination:

Initial investigations (performed within the first hour):

• 12‑lead ECG: ST‑segment elevation ≥2 mm in leads II, III, aVF; reciprocal ST depression in I and aVL; Q‑waves not yet evident.
• Cardiac biomarkers (high‑sensitivity troponin I): 0.03 ng/mL on arrival (reference <0.04 ng/mL); repeat at 3 h: 2.8 ng/mL.
• Chest X‑ray: Normal cardiac silhouette, clear lung fields, no pneumothorax.
• Basic labs:
  • Haemoglobin 14.2 g/dL, WBC 9.8 × 10⁹/L, platelets 240 × 10⁹/L.
  • Serum electrolytes: Na⁺ 138 mmol/L, K⁺ 4.2 mmol/L, Cl⁻ 102 mmol/L, HCO₃⁻ 24 mmol/L.
  • Creatinine 1.0 mg/dL (eGFR ≈ 90 mL/min/1.73 m²).
  • Lipid profile: Total cholesterol 210 mg/dL, LDL‑C 138 mg/dL, HDL‑C 38 mg/dL, TG 160 mg/dL.
• Point‑of‑care glucose: 112 mg/dL.

The patient is transferred immediately to the cardiac catheterisation laboratory for primary percutaneous coronary intervention (PCI).

Questions

1. What is the most likely diagnosis, and which clinical and investigative findings support it?
2. According to the 2023 ESC and ACC/AHA guidelines, what are the immediate management steps for this patient in the ED?
3. Which coronary artery is most likely occluded, and what angiographic findings would you expect?
4. Outline the post‑PCI pharmacological regimen, including doses, duration, and rationale.
5. Identify two major early complications of acute myocardial infarction and describe how they are recognised and managed.

Answers

1. Diagnosis and supporting findings

The presentation fulfills the criteria for ST‑segment elevation myocardial infarction (STEMI).

• Clinical clues:

  • Sudden onset, crushing retrosternal pain radiating to left arm/jaw, lasting >30 min.
  • Associated autonomic symptoms (diaphoresis, nausea).
  • High‑risk profile (age >55, hypertension, dyslipidaemia, smoking).

• ECG evidence:

  • New ST‑segment elevation ≥2 mm in contiguous inferior leads (II, III, aVF).
  • Reciprocal ST depression in lateral leads (I, aVL).
  • According to the 2023 ESC Guidelines for ACS, ST‑elevation in ≥2 contiguous leads meeting the above thresholds defines STEMI.

• Biomarker trend:

  • Initial high‑sensitivity troponin within normal range (early presentation) followed by a marked rise to 2.8 ng/mL at 3 h, confirming myocardial necrosis.

Thus, the combination of typical chest pain, diagnostic ST‑elevation, and dynamic troponin rise establishes a diagnosis of acute inferior STEMI.

2. Immediate ED management (2023 ESC & ACC/AHA)

The guidelines emphasise a “door‑to‑balloon” time ≤90 min for primary PCI. Immediate steps:

1. Aspirin 300 mg chewed – irreversible platelet COX‑1 inhibition; give within the first 10 min.
2. P2Y12 inhibitor – ticagrelor 180 mg loading (or clopidogrel 600 mg if ticagrelor unavailable).
3. Anticoagulation:
   • Unfractionated heparin (UFH) bolus 70 U/kg (max 5,000 U) IV, aiming for activated clotting time (ACT) 250–300 s; or
   • Bivalirudin 0.75 mg/kg bolus then 1.75 mg/kg/h infusion (if high bleeding risk).
4. Analgesia & anxiety control:
   • Morphine 2–4 mg IV if pain persists after nitrates (caution: may delay absorption of oral antiplatelets).
5. Oxygen therapy: Only if SpO₂ < 90 % (per 2023 ACC/AHA).
6. Nitrates: Sublingual nitroglycerin 0.4 mg repeat up to 3 doses; IV nitroglycerin infusion if persistent hypertension or pain, titrated to SBP ≥ 90 mmHg.
7. Beta‑blocker: Metoprolol 5 mg IV bolus (if no signs of heart failure, bradycardia, or hypotension); otherwise oral within 24 h.
8. Statin loading: High‑intensity atorvastatin 80 mg PO once (early initiation reduces recurrent events).

All above measures should be instituted while preparing for immediate transfer to the cath lab.

3. Likely occluded artery and expected angiographic appearance

Inferior STEMI with ST‑elevation in II, III, aVF most commonly reflects occlusion of the right coronary artery (RCA), particularly its proximal segment.

• Angiographic expectations:
  • Thrombotic occlusion of the proximal RCA with TIMI (Thrombolysis In Myocardial Infarction) flow grade 0–1.
  • Presence of a culprit lesion (often a ruptured atherosclerotic plaque with overlying thrombus).
  • Possible retrograde collateral flow from the left coronary system, but insufficient to prevent ischemia.

If the RCA is dominant (≈70 % of population), the inferior wall, right ventricle, and possibly the posterior left ventricle are jeopardised, explaining the clinical picture.

4. Post‑PCI pharmacological regimen

If the patient develops atrial fibrillation or another indication for anticoagulation, a triple therapy (DAPT + anticoagulant) may be required, but the default post‑PCI regimen follows the above.

5. Early complications: recognition & management

1. Cardiogenic shock (occurs in ≈5–10 % of STEMI).

   • Recognition: SBP < 90 mmHg, cool clammy skin, oliguria, elevated lactate, pulmonary congestion, reduced cardiac index (<2.2 L/min/m²).
   • Management:
     • Immediate inotropic support (e.g., norepinephrine 0.05–0.5 µg/kg/min) to maintain MAP ≥ 65 mmHg.
     • Mechanical circulatory support if refractory: intra‑aortic balloon pump (IABP) or Impella.
     • Prompt revascularisation of the culprit artery (primary PCI).
     • Optimise preload (small fluid bolus if hypovolaemic) and treat arrhythmias.

2. Ventricular arrhythmias (ventricular tachycardia/fibrillation).

   • Recognition: Palpitations, syncope, sudden haemodynamic collapse; ECG shows VT/VF.
   • Management:
     • Immediate defibrillation for VF or pulseless VT.
     • Anti‑arrhythmic therapy (e.g., amiodarone 150 mg IV bolus, then 1 mg/min infusion).
     • Beta‑blocker once stable (reduces recurrent VT).
     • Consider implantable cardioverter‑defibrillator (ICD) if LVEF ≤ 35 % after 40 days post‑MI (per 2023 ESC).

Early identification and treatment of these complications are vital to improve survival and functional recovery.

Key learning points

• STEMI is diagnosed by typical chest pain + new ST‑segment elevation in ≥2 contiguous leads, confirmed by a rising cardiac biomarker.
• Door‑to‑balloon ≤90 min is the benchmark; every minute of delay increases myocardial loss.
• Immediate therapy includes aspirin, a P2Y12 inhibitor, anticoagulation, nitrates, and early beta‑blockade (if not contraindicated).
• Inferior STEMI most often involves the proximal right coronary artery; dominance influences the extent of myocardial jeopardy.
• Post‑PCI dual antiplatelet therapy (aspirin + ticagrelor/clopidogrel) for at least 12 months, plus high‑intensity statin, ACE‑I/ARB, and beta‑blocker form the backbone of secondary prevention.
• Early complications such as cardiogenic shock and ventricular arrhythmias require rapid recognition and protocol‑driven management, including mechanical support and defibrillation.
• Lifestyle modification (smoking cessation, blood pressure and lipid control) is essential to prevent recurrent events.

Practice MCQs

1. Which of the following ECG criteria best defines a STEMI in the inferior leads?
A. ST‑elevation ≥1 mm in leads II, III, aVF
B. ST‑elevation ≥2 mm in leads II, III, aVF
C. New left bundle‑branch block with ST‑depression in V1‑V3
D. ST‑depression ≥1 mm in leads I and aVL

Answer: B — The 2023 ESC guideline defines STEMI as new ST‑segment elevation ≥2 mm in contiguous inferior leads (II, III, aVF).

2. A 58‑year‑old man with inferior STEMI receives primary PCI with a drug‑eluting stent. Which of the following is the recommended duration of dual antiplatelet therapy (DAPT) according to the 2023 ACC/AHA guideline?
A. 1 month
B. 3 months
C. 6 months
D. 12 months

Answer: D — For patients with a drug‑eluting stent and no high bleeding risk, a minimum of 12 months of DAPT (aspirin + P2Y12 inhibitor) is recommended.

3. Which early complication of STEMI is most strongly associated with a reduced left ventricular ejection fraction (LVEF ≤35 %) at 40 days post‑MI, prompting consideration of an ICD?
A. Pericarditis
B. Ventricular arrhythmia
C. Cardiogenic shock
D. Papillary muscle rupture

Answer: B — Ventricular arrhythmias (sustained VT/VF) post‑MI are a major predictor of low LVEF and are an indication for ICD implantation if LVEF remains ≤35 % after optimal medical therapy.

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