Lore has it that pure-right sided heart disease in pulmonary arterial hypertension doesn't cause pleural effusions. Luo et al report here that it does, in 35 of 89 people (39%) with connective-tissue disease-related PAH. (29 of the 35 had no other discernible cause for the effusion.) CHEST 2011;140:42-47.
Their group previously reported that people with IPAH or familial PAH also commonly develop pleural effusions (~20%).