APOE and pulmonary arterial hypertension: Similar examples of PH in the absence of RV hypertrophy have been reported in other mouse models of PAH, including spontaneous disease in mice bearing targeted mutations in the type II bone morphogenetic protein receptor (Bmpr2) (21, 27), as well as in ApoE−/− mice that develop PH in response to a high-fat Paigen diet (24).