A 46-year-old male with rheumatic heart disease (RHD) involving both mitral and aortic valves for 10 years, frequently hospitalized for heart failure (HF) in the past 5 years. Currently admitted again for HF. Physical exam: semi-recumbent position, jugular vein distension, enlarged cardiac borders, heart rate 140 bpm, atrial fibrillation, gallop rhythm audible at apex. Systolic and diastolic murmurs heard over both mitral and aortic valves. Left lung base shows rales/crackles, right lung exhibits dullness on percussion and absent breath sounds. Liver palpable 2 fingerbreadths below costal margin, soft consistency. Spleen not palpable, no ascites. Mild lower limb edema. The mechanism of right-sided pleural effusion in this case is: