NAC OSCE Chest Pain Case: ACS Station
A 58-year-old male presents to the emergency department with 45 minutes of central chest pain. Complete station walkthrough — candidate instructions, clinical approach, differential, Canadian ACS management, and patient counselling.
Station Overview
Station type: History-taking and management. This station assesses your ability to rapidly identify an acute coronary syndrome presentation, prioritise the most dangerous diagnosis in a time-critical scenario, and outline immediate Canadian-guideline-aligned management.
Competencies assessed: History taking, diagnosis, investigations, data interpretation, management, communication.
Key focus: Most marks in this station come from the management plan — specifically, knowing the first steps in suspected ACS and the door-to-ECG time target. Communication marks come from how you open the encounter and how clearly you explain your plan to the patient.
Candidate Instructions
Setting: Emergency department, City General Hospital
Mr. Robert Singh, 58 years old, has arrived in your emergency department by ambulance with a chief complaint of chest pain. He describes the pain as starting approximately 45 minutes ago. He is alert and cooperative.
Your tasks:
1. Take a focused history from Mr. Singh.
2. Tell Mr. Singh what investigations you will order and explain your working diagnosis.
3. Outline your initial management plan.
The physician examiner will ask you questions at the end of the encounter.
Clinical Approach
Opening the encounter
Enter, introduce yourself, and acknowledge the patient's distress immediately. Do not begin with closed questions — the opening tells the examiner whether you are patient-centred.
"Mr. Singh, I'm Dr. [Name], one of the emergency physicians. I understand you came in with chest pain — that must have been very frightening. I'm going to ask you a few questions so we can understand what's happening and get you the right treatment quickly. Is that okay?"
Focused history — SOCRATES
- Site: Central/retrosternal — classic for cardiac origin
- Onset: Sudden onset at rest vs. exertional? Time of onset?
- Character: Pressure, squeezing, or crushing — versus sharp or tearing (aortic dissection)
- Radiation: To left arm, jaw, shoulder, or back
- Associations: Diaphoresis (a red flag), nausea/vomiting, dyspnea, palpitations, pre-syncope
- Time/course: Constant since onset? Any previous similar episodes? Any relief with rest or NTG?
- Exacerbating/relieving: Exertional onset, relief with NTG (supports anginal aetiology)
- Severity: Pain score, functional impact
Targeted past history
- Known coronary artery disease, previous MI, PCI or CABG
- Risk factors: hypertension, dyslipidaemia, type 2 diabetes, smoking history (pack-years), family history of premature CAD (<55 male, <65 female first-degree relative)
- Current medications — especially antiplatelet, statin, nitrates, PDE5 inhibitors (contraindication to nitroglycerin)
- Allergies — especially ASA, iodine (contrast)
In ACS stations, the physician examiner commonly asks: "What is your most responsible diagnosis?" and "What would you do first?" Practice stating these answers concisely. "My working diagnosis is STEMI until proven otherwise — I would get a 12-lead ECG within 10 minutes of his arrival" is the kind of answer that earns marks.
Differential Diagnosis
| Diagnosis | Supporting features | Against |
|---|---|---|
| STEMI / NSTEMI | Pressure-type pain, radiation to arm/jaw, diaphoresis, multiple risk factors, rest onset | — |
| Unstable angina | Similar presentation, but troponin negative; exertional onset | Pain at rest and with diaphoresis raises STEMI concern |
| Aortic dissection | Severe, tearing pain maximal at onset; posterior radiation to back | Character described as pressure, not tearing; onset not maximal immediately |
| Pulmonary embolism | Pleuritic pain, dyspnea, risk factors (immobility, DVT history, malignancy) | Central pressure-type pain without pleuritic component is less typical |
| GERD / esophageal spasm | Burning, post-prandial, relief with antacids | Diaphoresis and radiation to arm not consistent; must rule out cardiac first |
Management — Canadian ACS Guidelines
Management of suspected ACS in Canada follows the Canadian Cardiovascular Society (CCS) guidelines and ACLS protocols. The key principle: treat as STEMI until the ECG and clinical picture prove otherwise.
Immediate (first 10 minutes)
- 12-lead ECG — must be obtained within 10 minutes of arrival (door-to-ECG target)
- Continuous cardiac monitoring, pulse oximetry, IV access (two large-bore IVs)
- Aspirin 160–325 mg chewed immediately (unless true allergy) — first-line antiplatelet
- Oxygen only if SpO₂ <90% — routine oxygen is not indicated and may be harmful in normoxic patients
- Nitroglycerin 0.4 mg SL q5 minutes × 3 for ongoing pain — withhold if BP <90 systolic, right ventricular infarct suspected (inferior ST elevation), or PDE5 inhibitor use within 24–48h
If STEMI confirmed on ECG
- Activate STEMI protocol and cardiology immediately
- Primary PCI is preferred reperfusion strategy — door-to-balloon time target ≤90 minutes at PCI-capable centres
- P2Y12 inhibitor (ticagrelor 180 mg or clopidogrel 600 mg) loading dose pre-PCI per local protocol
- Anticoagulation: unfractionated heparin or bivalirudin per cath lab protocol
- Fibrinolysis if PCI unavailable within 120 minutes of STEMI diagnosis
Investigations to order
- Troponin I or T (high-sensitivity) — on arrival and repeat at 1–3 hours
- CBC, electrolytes, creatinine, glucose, coagulation screen
- Chest X-ray (portable — do not delay ECG for CXR)
- Lipid panel (if not recent)
Counselling the Patient
Marks in the counselling component come from three things: explaining the diagnosis in plain language, acknowledging the patient's concerns, and describing what happens next in terms the patient can follow.
"Mr. Singh, based on your symptoms and what I'm seeing, I'm very concerned that you may be having a heart attack — what we call a myocardial infarction. I want to be honest with you about that. What's happening is that one of the arteries supplying blood to your heart has likely become blocked."
"The most important thing right now is to open that blockage as quickly as possible. We're going to give you aspirin immediately to thin the blood, and we'll be getting a heart tracing — the ECG — done right now. If the ECG confirms what I suspect, the heart specialists will take you to the cardiac catheterization lab, where they'll open the blocked artery with a small balloon and a stent. The goal is to do that within 90 minutes."
"I know this is a lot to take in. Do you have family here, or would you like us to call someone? Is there anything you'd like to ask me right now?"
In high-stakes emergency stations, Calgary-Cambridge marks still apply. Notice the structure above: explain clearly → use patient-friendly language → check for questions → offer to involve family. Many IMGs focus entirely on the clinical plan and forget the final "Is there anything you'd like to ask?" — that single phrase is on many marking checklists.
This is a practice case based on a station from NAC OSCE: A Comprehensive Review (2nd Edition). The full book version includes a detailed patient history, physical examination findings, an expanded differential diagnosis, step-by-step management aligned to Canadian guidelines, and a complete counselling script — across all 92 stations.