A DIAGNOSTIC DILEMMA: NORMAL D-DIMER IN A PATIENT WITH EXTENSIVE PULMONARY EMBOLISM

Abstract

SESSION TITLE: Medical Student/Resident Pulmonary Vascular Disease Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: October 18-21, 2020 INTRODUCTION: The presentation of pulmonary embolism (PE) is very non-specific and carries a significant morbidity and mortality. Typically, D-dimer assay has a very high sensitivity and a negative predictive value of 99-100% in both low and moderate risk groups. We present a unique case of diagnosing extensive PE with deep vein thrombosis (DVT) in presence of a normal D-dimer. CASE PRESENTATION: A 69-year-old female with significant history of hypertension and diabetes presented with dry cough and worsening of dyspnea on exertion for four days. Patient denied chest pain, palpitations, fever, chills, diaphoresis, leg pain or swelling. Vitals showed a T 98.6, BP 112/64 mmHg, HR 56, RR 16, oxygen saturation of 90% on 3LPM of nasal canula. Physical exam, especially the pulmonary exam, was largely unremarkable. No swelling or pain in the lower extremities was noted. Laboratory findings including the metabolic panel, blood count, and a set of troponins were within normal limits. ECG showed a normal sinus rhythm, and a follow-up chest radiograph and a non-contrast CT scan of chest did not demonstrate any significant findings. Acute PE was ruled out since the D-dimer assay was normal and the pretest probability was low-moderate. Preliminary diagnosis of pulmonary hypertension was suspected and worked up. An echocardiogram showed severe pulmonary hypertension with elevated right ventricular systolic pressure in the setting of a normal LV ejection fraction. A ventilation perfusion scan was subsequently done to evaluate for CTEPH, and was overwhelmingly positive with a high probability of PE. A CT angiogram revealed extensive bilateral central and segmental PE. Doppler ultrasound of lower extremities revealed an acute non-occlusive DVT involving the left popliteal vein. Patient was subsequently started on anti-coagulants and the supplemental oxygen was continued prior to safe discharge. DISCUSSION: D-dimer assay is a highly sensitive test used in the evaluation of PE. It is a measure of monoclonal antibody to D-Dimer produced during the process of fibrinolysis. D-dimer has a half-life of 4-6 hours and stays elevated for about seven days. Once the clot organization and adherence begins, levels of D-dimer drop. As such, D-dimer levels correlate with the presence of fibrin clots. The assay can be falsely negative if the specimen is collected very early or later than 7 days of clot formation. Regardless, a negative assay should be able to safely rule out a large PE in low and moderate risk patients. A low d-dimer assay on presentation in light of an extensive PE/DVT makes our case unique. CONCLUSIONS: D-dimer assay usually provides excellent diagnostic yield while ruling out a PE/DVT. However, it remains prudent to consider the overall clinical presentation and go through a step by step approach to not miss a disease with a fatal potential such as a PE in our case. Reference #1: Dagkiran H, Atas R, Tomic I, Plachtzik C, Geisler T, Gawaz MP, Oberhoff M, Anger T. Severe Pulmonary Embolism with Negative D-Dimer-Testing. Journal of Cardiology and Therapy 2015; 2(1): 265-268 Available from: URL: http://www.ghrnet.org/index.php/jct/article/view/1033 Reference #2: Gupta RT, Kakarla RK, Kirshenbaum KJ, Tapson VF. D-dimers and efficacy of clinical risk estimation algorithms: sensitivity in evaluation of acute pulmonary embolism. AJR Am J Roentgenol. 2009;193(2):425-430 Reference #3: Le Gal G, Righini M, Roy P, et al. Value of D-Dimer Testing for the Exclusion of Pulmonary Embolism in Patients With Previous Venous Thromboembolism. Arch Intern Med. 2006;166(2):176 -180. doi:http://dx.doi.org/10.1001/archinte.166.2.176 DISCLOSURES: No relevant relationships by Richard Miller, source=Web Response No relevant relationships by Kinjal Patel, source=Web Response No relevant relationships by Rutwik Patel, source=Web Response No relevant relationships by Krunal Trivedi, source=Web Response