An 85-year-old woman with...

An 85-year-old woman, who recently underwent cataract surgery and has no history of hypertension or diabetes mellitus, experienced a sudden episode of chest pain, tachycardia, tachypnoea, blood-stained frothing at the mouth, and dizziness. She was subsequently admitted to the ICU. On admission, her blood pressure was 220/120, SpO2 was 55, and an ECG revealed an old right bundle branch block (RBBB) with tachycardia but no ST changes. A chest X-ray showed an enlarged heart and increased lung markings, indicative of pulmonary plethora. Her creatinine level was elevated at 1.9, and cardiac enzymes were also elevated. D-dimer levels were high on two consecutive readings. Her hypertension was under control, and she was treated with intravenous Lasix and placed on BiPAP ventilation. The following day, her breathlessness improved after receiving high-flow oxygen to maintain her SpO2 at 94. The tachypnea also decreased, and her creatinine levels returned to normal. A 2D echocardiogram showed an ejection fraction of 55% with mild mitral regurgitation, mild aortic regurgitation, and mild tricuspid regurgitation, but no pericardial effusion. On the second day, the D-dimer levels remained high. What will be the diagnosis?