A 55-year-old male had been treated at the surgical department for acute lower-extremity thrombophlebitis. On the 7th day of treatment he suddenly developed pain in the left part of chest, dyspnea and cough. Body temperature was 36,1°C, respiratory rate - 36/min. The patient was also found to have diminished breath sounds without wheezing. Ps- 140/min, thready. AP- 70/50 mm Hg. The ECG shows QIII-S1 syndrome. What is the most likely diagnosis?