A 78-year-old man, who has heart failure, is admitted to hospital because of acute onset of dyspnea. His chest x- ray reveals moderate bilateral pleural effusion. Thoracentesis is performed and pleural fluid analysis is done Pleural fluid-serum LDH ratio 0.52 Pleural fluid LDH level 46% of the upper limit of the normal level Pleural fluid-serum total protein ratio 0.45 Pleural fluid cytology Pending Which of the following is the most likely cause of this patient's pleural effusion?