Review Question - QID 218258

This patient with a history of malignancy and recent flights presenting with acute sharp non-radiating pleuritic chest pain, hemoptysis, dyspnea, tachycardia, tachypnea, and bibasilar rales most likely has a pulmonary embolism. In a hemodynamically stable patient in whom there is a high probability of PE, a definitive diagnosis with computed tomography pulmonary angiogram (CTPA) is the best initial step in management.

Acute pulmonary embolism (PE) is an obstruction of the pulmonary artery or its branches by thrombus, tumor, air, or fat that originates elsewhere in the body that causes symptoms and signs immediately after. A “massive” PE causes hemodynamic instability (systolic blood pressure < 90 mmHg or a drop in systolic blood pressure > 40 mmHg from baseline), a “submassive” PE does not cause hemodynamic instability but is associated with right ventricular strain, and a “low-risk” PE does not show evidence of risk ventricular strain. Symptoms and signs in patients with PE include dyspnea, pleuritic chest pain, cough, orthopnea, lower extremity swelling or pain, wheezing, hemoptysis, tachypnea, tachycardia, rales, and jugular venous distention. The diagnostic evaluation of PE varies based on hemodynamic stability and clinical suspicion of PE. The Wells criteria is commonly used for risk stratification of PE and assigns points to various PE criteria including: clinical signs of deep vein thrombosis (DVT) (3), PE is the #1 diagnosis (3), heart rate > 100 beats/minute (1.5), immobilization or recent surgery (1.5), previous PE or DVT (1.5), hemoptysis (1), recent malignancy (1). Scores greater than 6 are high risk, scores between 2 and 6 are intermediate risk, and scores less than 2 are low risk. Hemodynamically unstable patients despite resuscitation should undergo bedside ultrasonography to obtain a presumptive diagnosis of PE; treatment should then be promptly initiated. Hemodynamically stable patients with a high risk of PE should undergo definitive diagnostic testing with a CTPA if feasible (no allergy to iodinated contrast, body habitus that is able to fit in scanner, and ability to cooperate with breath holding). Otherwise, these patients should undergo diagnostic testing with a ventilation-perfusion scan. Patients at intermediate risk and patients at low risk that meet the pulmonary embolism rule-out criteria (PERC) should undergo testing with D-dimer. Patients with elevated D-dimer should then be assessed with CTPA. The treatment of acute pulmonary embolism can include anticoagulation, placement of an inferior vena cava filter, embolectomy, and delivery of tissue plasminogen activator (tPA).

Konstantinides et al. discuss the 2019 European Society of Cardiology guidelines for the diagnosis and management of acute pulmonary embolism. The authors note that the specificity of D-dimer for suspected PE decreases to as low as 10% in patients over the age of 80 years. Therefore, the authors recommend using D-dimer thresholds that are adjusted for age and clinical probability.
Figure/Illustration A shows an EKG from a patient with sinus tachycardia. There is a P wave (blue arrow) before every QRS (yellow box), a QRS after every P, and a rate of 125 beats per minute.

Incorrect Answers:
Answer 2: D-dimer would be an appropriate initial screening test in patients with a low or an intermediate probability of PE. However, this patient with multiple risk factors has a high probability of PE and should directly be evaluated with a CTPA.

Answer 3: Lower extremity compression ultrasonography can be used to assess for deep vein thrombosis. It can be used in the evaluation of PE in patients in which both a CTPA and a ventilation-perfusion scan are not feasible. This patient who is able to lie flat, has a BMI of 26, and has no contraindications to receiving iodinated contrast should receive a CTPA instead to rule out PE.

Answer 4: Transthoracic echocardiography can be used to assess right ventricular overload in order to obtain a presumptive diagnosis of PE in a hemodynamically unstable patient with suspected PE. However, echocardiography cannot provide a definitive diagnosis of PE. This patient who is hemodynamically stable and without evidence of right heart strain should undergo diagnostic evaluation for a definitive diagnosis of PE before treatment is initiated.

Answer 5: A ventilation-perfusion scan (VQ scan) can be used in patients with a contraindication to receiving a CTPA. A VQ scan uses radioactive isotopes to assess discrepancies between ventilation and perfusion that indicate the presence of a PE.

Bullet Summary:
The most appropriate diagnostic test for a stable patient who is at high risk for pulmonary embolism is a computed tomography pulmonary angiogram.