A 50-year-old male, 1 month post-hip surgery, suddenly developed chest pain, hemoptysis, and dyspnea after getting up. Physical exam: tachypnea, rales in lungs, accentuated P<sub>2</sub>, left lower limb swelling with tenderness. ECG shows SⅠQⅢTⅢ pattern, WBC(+), D-dimer(+). The most likely diagnosis is: