Introduction

Chest pain is one of the most common presentations in Canadian Emergency Departments and primary care settings. For the MCCQE1, the candidate must demonstrate the ability to rapidly differentiate between life-threatening conditions (the “Killer” diagnoses) and benign causes. This requires a structured approach aligned with the Medical Expert role of the CanMEDS framework.

MCCQE1 Objectives

When preparing for the MCCQE1, focus on the following key objectives regarding chest pain:

1. Data Acquisition: Elicit a relevant history (onset, quality, radiation, risk factors) and perform a focused physical exam.
2. Problem Solving: Construct a differential diagnosis distinguishing cardiac, pulmonary, gastrointestinal, and musculoskeletal causes.
3. Management: Initiate immediate management for unstable patients (ABCs, MONA-BASH equivalent) and appropriate investigations for stable patients.
4. Health Promotion: Identify modifiable risk factors (smoking, hypertension, dyslipidemia) relevant to the Canadian population.

Differential Diagnosis: The “Killer” Causes

For MCCQE1 preparation, you must prioritize ruling out life-threatening conditions. We categorize these using the 4+2+2 rule (Cardiac, Pulmonary, Vascular/Other).

Clinical Approach

1. History (The OPQRST Mnemonic)

A thorough history is the most powerful tool in the MCCQE1 arsenal.

# OPQRST Mnemonic
O - Onset (Sudden vs. Gradual)
P - Provocation/Palliation (Exertion, position, nitroglycerin)
Q - Quality (Pressure, tearing, pleuritic, burning)
R - Region/Radiation (Jaw, left arm, back, epigastrium)
S - Severity (Scale 1-10)
T - Timing (Duration, constant vs. intermittent)

2. Physical Examination

Focus on signs of hemodynamic instability and specific findings for the differential.

3. Diagnostic Investigations

Follow this stepwise approach for the MCCQE1 clinical reasoning scenarios:

Canadian Guidelines (CCS & Thrombosis Canada)

Understanding Canadian-specific guidelines is essential for high performance on the MCCQE1.

Acute Coronary Syndrome (CCS Guidelines)

• Antiplatelet Therapy:
  • ASA: 160–325 mg chewed immediately (stat). Long-term 81 mg daily.
  • P2Y12 Inhibitor: Ticagrelor or Clopidogrel added for ACS.
• Nitroglycerin: 0.4 mg spray SL q5min x 3 doses (avoid in RV infarct or if use of PDE-5 inhibitors like Sildenafil).
• Oxygen: Only if SpO2 < 90% (routine oxygen is no longer recommended).

Pulmonary Embolism (Thrombosis Canada)

• Low Pre-test Probability: Use PERC Rule. If negative, no testing. If positive, D-Dimer.
• High Pre-test Probability: CT Pulmonary Angiogram (CTPA).
• Treatment: DOACs (e.g., Rivaroxaban, Apixaban) are now first-line over Warfarin for most stable PEs in Canada.

Management Summary

Initial Stabilization (The “Safety Net”)

For any unstable patient (Hypotensive, Hypoxic, Altered Mental Status):

1. IV: Two large-bore IVs.
2. O2: Supplemental oxygen if hypoxic.
3. Monitor: Cardiac monitor, BP, Saturation.
4. ECG: Stat 12-lead.
5. Defibrillator: Pads on if unstable.

Condition-Specific Management Table

Key Points to Remember for MCCQE1

• Women and Diabetics: Often present with atypical symptoms (nausea, fatigue, jaw pain) rather than classic chest crushing.
• Cocaine Chest Pain: Benzodiazepines are first-line for anxiety/tachycardia. Avoid Beta-blockers in the acute phase (theoretical risk of unopposed alpha stimulation).
• Costochondritis: Reproducible tenderness is suggestive but does not rule out ACS. You must still risk stratify.
• Gastric Cocktail: Relief with a “GI cocktail” (lidocaine/antacid) does not rule out cardiac ischemia.

Sample Question

Scenario: A 62-year-old male presents to the Emergency Department with a sudden onset of severe, “tearing” chest pain radiating to his interscapular region. He has a history of poorly controlled hypertension and smoking. On examination, he appears anxious and diaphoretic. His blood pressure is 180/100 mmHg in the right arm and 150/90 mmHg in the left arm. Heart rate is 105 bpm. Auscultation reveals a new diastolic decrescendo murmur at the right upper sternal border. An ECG shows sinus tachycardia with left ventricular hypertrophy but no ST-segment changes. A portable chest X-ray shows a widened mediastinum.

Question: Which one of the following is the most appropriate next step in the diagnostic management of this patient?

• A. Transthoracic Echocardiogram (TTE)
• B. Measurement of serum D-dimer
• C. CT Angiography of the chest
• D. Coronary Angiography
• E. Magnetic Resonance Imaging (MRI) of the chest

Explanation

The correct answer is:

• C. CT Angiography of the chest

Detailed Explanation:

The clinical presentation is highly suggestive of an Acute Aortic Dissection. Key features include:

• Demographics/Risk Factors: Older male, uncontrolled hypertension (most significant risk factor), smoking.
• Symptoms: Sudden onset, “tearing” pain radiating to the back (interscapular).
• Signs: Significant blood pressure differential (>20 mmHg) between arms, new aortic regurgitation murmur (diastolic decrescendo), and widened mediastinum on CXR.

Why C is correct: CT Angiography (CTA) is the gold standard diagnostic test for stable patients with suspected aortic dissection in the acute setting. It is rapid, widely available in Canadian centres, and has high sensitivity and specificity.

Why other options are incorrect:

• A. Transthoracic Echocardiogram (TTE): While useful, TTE has low sensitivity for the descending aorta and limited visualization of the aortic arch. Transesophageal Echocardiogram (TEE) would be a valid alternative, especially in unstable patients, but CTA is preferred in stable patients.
• B. D-dimer: While often elevated in dissection, it is non-specific. A negative D-dimer can help rule out dissection in low-risk patients, but this patient is high-risk and requires imaging.
• D. Coronary Angiography: This is indicated for ACS. While dissection can involve coronary arteries (causing STEMI), the clinical picture points primarily to dissection. Catheterization could delay life-saving treatment or propagate the dissection.
• E. MRI: While highly accurate, MRI is time-consuming and often not feasible in an acute emergency setting where rapid diagnosis is required. It is better suited for chronic follow-up.

References

1. Medical Council of Canada. (n.d.). Objectives for the Qualifying Examination Part I. Retrieved from mcc.ca 
2. Canadian Cardiovascular Society. (2024). CCS Guidelines for the Management of Acute Coronary Syndromes.
3. Thrombosis Canada. (2023). Pulmonary Embolism: Diagnosis and Management. Retrieved from thrombosiscanada.ca 
4. Toronto Notes. (2024). Cardiology: Chest Pain Approach. Toronto Notes for Medical Students, Inc.
5. Canadian Association of Emergency Physicians (CAEP). CTAS Guidelines.