Westermark Sign in Pulmonary Embolism

A 47-year-old woman presented to the emergency department with acute shortness of breath and hypoxia. Her medical history included sex reassignment, for which she was taking estrogen, and a deep-vein thrombosis on the left side, for which she had required warfarin. A 47-year-old woman presented to the emergency department with acute shortness of breath and hypoxemia. Her medical history included sex reassignment, for which she was taking estrogen, and a deep-vein thrombosis on the left side, for which she had required treatment with warfarin. She had a family history of fatal pulmonary emboli. An electrocardiogram revealed right bundle-branch block and right axis deviation (the electrocardiogram is available in the Supplementary Appendix). Blood tests revealed an elevated D-dimer level of 2073 ng per milliliter. A chest radiograph showed a Westermark sign (Panel A, arrow), with a focal area of oligemia in the right . . .