A 35-year-old woman presents to the emergency department for evaluation of shortness of breath with chest pain which started 12 hours ago. She has no chronic medical conditions, and her only medications are a daily multivitamin and a combined oral contraceptive pill. She returned from visiting family in Greece yesterday and denies recent illness. Vital signs are notable for a heart rate of 115 beats/minute, respiratory rate of 32 breaths/minute, blood pressure of 132/86 mmHg, and an oxygen saturation of 89% on room air.
A) Administer low molecular weight heparin (LMWH)
This patient is presenting with signs and history consistent with pulmonary embolism (PE). Her modified Wells score is 4.5, with 3 points for presentation consistent with PE and 1.5 points for heart rate > 100 beats/minute. A score greater than 4 indicates high likelihood of PE, for which empiric anticoagulation should be given prior to diagnostic tests. Options for initial anticoagulation include LMWH, fondaparinux, unfractionated heparin, oral factor Xa inhibitors, or direct thrombin inhibitors. Limited data suggest that LMWH and fondaparinux are superior to unfractionated heparin, which also requires monitoring. Remember that the direct thrombin inhibitor dabigatran and the factor Xa inhibitor edoxaban require a short course of heparin (usually LMWH) for five days before transitioning to oral therapy alone.
Answer choice B: Administer tissue plasminogen activator (tPA), is incorrect. Fibrinolytics such as tPA are not indicated for pulmonary embolism when a patient is hemodynamically stable, as this patient is.
Answer choice C: Administer unfractionated heparin, is incorrect. Unfractionated heparin is indicated in patients with a glomerular filtration rate (GFR) of < 30 mL/minute. This is because low molecular weight heparin is renally cleared and can increase bleeding risk in individuals with renal pathology.
Answer choice D: Obtain CT pulmonary angiogram, is incorrect. While this is the gold standard imaging technique for suspected pulmonary embolism, there is high clinical suspicion that this patient has a PE. Anticoagulation should therefore precede diagnostic imaging.
Answer choice E: Place an inferior vena cava (IVC) filter, is incorrect. IVC filters can be used to treat pulmonary embolism in patients with contraindications to anticoagulation, such as those with a history of bleeding disorder or those who are already medically anti-coagulated (e.g. patient with atrial fibrillation taking warfarin). This patient has no such contraindications and should therefore be treated with anticoagulation.
Key Learning Point
A modified Wells score greater than 4 indicates high likelihood of pulmonary embolism, for which empiric anticoagulation should be given prior to pursuing diagnostic tests.
