Yesterday was world thrombosis day. This unfortunate patient had trouble breathing despite a normal chest x-ray and having a filter to prevent blood clots from going to the lung. CT scan was ordered, which shows a massive blood clot at the branch point of the main pulmonary artery within the lung, depicted here by the yellow arrow. This is a life threatening condition known as “saddle” pulmonary embolism. Difficulty breathing is a serious complaint and must be fully evaluated.