A 57-year-old man presents to the emergency department for shortness of breath. He was riding the train home from a business conference when his symptoms began. The patient has a medical history of obesity, diabetes, diabetic nephropathy, hypertension, and a 40-pack-year smoking history. His current medications include atorvastatin, lisinopril, insulin, metformin, and nicotine gum. His temperature is 99.5°F (37.5°C), blood pressure is 130/87 mmHg, pulse is 120/min, respirations are 15/min, and oxygen saturation is 93% on room air. An ECG is ordered as seen in Figure A. A chest radiograph is ordered as seen in Figure B. Laboratory values are ordered as seen below: Serum: Na+: 137 mEq/L Cl-: 105 mEq/L K+: 4.1 mEq/L HCO3-: 24 mEq/L BUN: 22 mg/dL Glucose: 129 mg/dL Creatinine: 1.2 mg/dL Ca2+: 10.1 mg/dL AST: 11 U/L ALT: 12 U/L On physical exam, the patient appears to be in distress. His cardiac exam is notable for tachycardia. Pulmonary exam reveals bilateral air movement without any wheezes or crackles. The patient's right lower extremity appears mildly inflamed, and palpation of the calf elicits pain. Which of the following is the most appropriate next step in management?
Aspirin
Cardiac troponins
Heparin
Ventilation perfusion scan
Heparin
This patient is presenting with a score of 7.5 on Wells criteria suggesting a diagnosis of pulmonary embolism. The most appropriate initial step in management is heparin administration.

Patients with suspected pulmonary embolism (PE) can be evaluated with Wells criteria which consists of: clinical signs and symptoms of DVT (3 points), PE is the most likely diagnosis (3 points), pulse > 100 (1.5 points), immobilization for 3 days, or surgery within 4 weeks (1.5 points), history of DVT or PE (1.5 points), hemoptysis (1 point), and malignancy (1 point). Scores higher than 3 suggest a high probability of PE. Patients will often present with shortness of breath, with ECG findings of sinus tachycardia, and a chest radiograph that is typically normal. With a high pre-test probability, the most important initial step in management is anticoagulation with heparin versus further diagnostic workup.

Doherty reviews the evidence regarding the diagnosis and treatment of pulmonary embolism. He discusses how clinical criteria such as Wells criteria can be helpful in assessing the likelihood of a PE. He recommends immediate treatment in patients who have a PE.

Figure/Illustration A is an ECG demonstrating sinus tachycardia with a P wave, a QRS complex, and a T wave during every beat (red circle). This is the most common ECG presentation in PE, though right heart strain can also be seen.

Figure B is a chest radiograph that is within normal limits without evidence of fluid in the dependent portions of the lung (red circles). This is the most common radiological presentation in PE.

Incorrect Answers:
Answer A: Aspirin would be the most appropriate initial step in the management of MI and can reduce mortality by up to 25% if administered promptly. PE is a more likely diagnosis in this patient given the ECG that only demonstrates sinus tachycardia.

Answer B: Cardiac troponins could be used to confirm the diagnosis of myocardial infarction (MI). In the presence of this patient's ECG (which does not demonstrate ST elevation), MI is a less likely diagnosis. Treatment would be with aspirin in patients who had an MI followed by emergent revascularization.

Answer C: A CT scan of the chest without contrast would not confirm the diagnosis in this patient; however, a CT angiogram would be the most accurate test. It is more important to begin treatment with heparin when there is a very high clinical suspicion of PE.

Answer E: A ventilation perfusion scan is the most accurate test for PE in a patient who cannot tolerate contrast. This test has a low specificity.

Bullet Summary:
The most appropriate initial step in the management of a pulmonary embolism in patients with a high pre-test probability is anticoagulation with heparin.