What is the differential diagnosis for a patient with chest pain on the left side after a workout, considering potential underlying conditions such as acute coronary syndrome (ACS) or pulmonary embolism (PE), and taking into account the patient's past medical history, including possible cardiovascular disease (CVD)?

Differential Diagnosis for Left-Sided Chest Pain After Workout

Left-sided chest pain after exercise requires immediate exclusion of acute coronary syndrome (ACS), as exertion-provoked substernal discomfort is the hallmark presentation of myocardial ischemia, regardless of age or baseline cardiovascular risk. 1

Immediate Life-Threatening Conditions to Rule Out First

Acute Coronary Syndrome

• Substernal pressure or discomfort building gradually over minutes during or after exertion, potentially radiating to left arm, jaw, or neck, with associated diaphoresis, dyspnea, or nausea 1
• Exercise provocation is a classic ischemic trigger, and examination may be completely normal in uncomplicated cases 1, 2
• Women and elderly patients frequently present with atypical symptoms including isolated dyspnea, nausea, or fatigue without classic chest pressure 3, 4
• Obtain 12-lead ECG within 10 minutes and measure high-sensitivity cardiac troponin immediately 1, 3

Pulmonary Embolism

• Acute dyspnea with pleuritic chest pain, tachycardia (present in >90% of patients), and tachypnea 1, 4
• Can mimic ACS with electrical changes and cardiac enzyme elevation 5
• Consider risk factors including recent immobilization, surgery, or hypercoagulable states 6

Acute Aortic Dissection

• Sudden-onset "ripping" or "tearing" chest or back pain with pulse differentials between extremities or blood pressure differential >20 mmHg 1, 2
• New aortic regurgitation murmur may be present 1

Pneumothorax

• Dyspnea and sharp pain on inspiration with unilateral absence of breath sounds 1, 2
• Primary spontaneous pneumothorax characteristically presents with acute chest pain 7

Cardiac Causes (Non-ACS)

Pericarditis

• Sharp, pleuritic chest pain worsening when supine and improving when leaning forward, with friction rub on examination and fever 1, 2, 4
• Pain may be positional and affected by breathing 4

Myocarditis

• Chest pain with fever, signs of heart failure, and S3 gallop 1
• May follow recent viral illness 2

Musculoskeletal Causes

Costochondritis/Tietze Syndrome

• Tenderness of costochondral joints on palpation with pain reproducible by chest wall pressure 1, 2, 4
• Pain affected by palpation, breathing, turning, twisting, or bending 4
• Most common diagnosis when cardiac causes are excluded 4
• Point tenderness renders ischemia less likely but does not exclude it 1

Chest Wall Strain

• Pain localized to very limited area, affected by specific movements or positions 4
• May result from exercise-related muscle strain 2

Pulmonary Causes

Pleurisy

• Sharp, pleuritic chest pain related to breathing movements 7
• May be associated with respiratory infection 7

Pneumonia

• Fever, localized chest pain (may be pleuritic), friction rub, regional dullness to percussion, egophony 1, 6

Gastrointestinal Causes

Gastroesophageal Reflux Disease/Esophagitis

• Burning retrosternal pain, acid regurgitation, sour or bitter taste in mouth 4, 6
• May be relieved by antacids 4

Esophageal Rupture

• History of emesis, subcutaneous emphysema, pneumothorax, unilateral decreased or absent breath sounds 1, 2

Mandatory Initial Evaluation Algorithm

Step 1: Immediate Assessment (Within 10 Minutes)

• Obtain 12-lead ECG to identify ST-segment elevation, ST-segment depression, new Q waves, or T-wave inversions 1, 3
• Measure high-sensitivity cardiac troponin as soon as possible 1, 3
• Assess vital signs including blood pressure in both arms, heart rate, respiratory rate, and oxygen saturation 1, 3

Step 2: Focused History

• Exact onset, duration, quality (pressure vs. sharp vs. burning), and severity of pain 1, 2
• Radiation pattern to left arm, jaw, neck, back, or upper abdomen 1, 4
• Relationship to exertion, breathing, position, or meals 1, 4
• Associated symptoms: diaphoresis, dyspnea, nausea, syncope, palpitations 3, 4
• Cardiovascular risk factors: age, diabetes, hypertension, hyperlipidemia, smoking, family history of premature CAD 3

Step 3: Focused Physical Examination

• Cardiovascular examination for murmurs, friction rub, S3 gallop, pulse differentials, and blood pressure differentials 1, 3
• Chest wall palpation for reproducible tenderness 1, 2
• Pulmonary examination for unilateral decreased breath sounds, crackles, or egophony 1

Step 4: Risk Stratification and Disposition

• If ST-elevation or new ischemic ECG changes: immediate transfer by EMS for reperfusion therapy 3, 4
• If elevated troponin without ST-elevation: admit to coronary care unit with continuous cardiac monitoring 3
• If ECG and initial troponin negative but high clinical suspicion: serial ECGs and troponins, consider stress testing or coronary CT angiography 1
• If clearly musculoskeletal with reproducible tenderness and no high-risk features: outpatient management with close follow-up 2, 4

Critical Pitfalls to Avoid

• Do not use nitroglycerin response as a diagnostic criterion, as esophageal spasm and other non-cardiac conditions also respond to nitroglycerin 1, 2, 4
• Do not dismiss chest pain based on young age, as ACS can occur even in adolescents without traditional risk factors 3
• Do not assume sharp or pleuritic pain excludes ACS, as pericarditis and atypical presentations occur 3, 4
• Do not delay transfer to emergency department for troponin testing in office settings when ACS is suspected 1, 3
• Do not underestimate risk in women, elderly patients, or patients with diabetes, as they frequently present with atypical symptoms 3, 4

High-Risk Features Requiring Immediate Emergency Department Transfer by EMS

• Age ≥75 years with accompanying dyspnea, syncope, acute delirium, or unexplained fall 2, 4
• Prolonged ongoing rest pain or pain lasting >20 minutes 3
• Hemodynamic instability (hypotension, tachycardia, diaphoresis) 1, 3
• New ECG abnormalities 4
• Pulse differentials or blood pressure differential >20 mmHg 1, 2
• New cardiac murmurs 1