In Vivo PAB Model

Animal experiments were approved by the institutional animal ethics committee. Thirty‐six male Sprague‐Dawley rats (200 g body weight) were randomized to either sham (n=10) surgery (thoracotomy) or to PAB (n=26). Anesthesia was induced by IP pentobarbital sodium (60 mg/kg). After intubation, animals were mechanically ventilated using a volume‐controlled respirator and oxygen‐enriched room air. Positive end‐expiratory pressure was maintained at 4 cm H₂O. Through a left thoracotomy, the pulmonary artery (PA) was separated from the aorta. Then, an 18‐gauge needle was placed under the PA, and a silk suture was tied around the needle and vessel. Subsequent removal of the needle produced a fixed and standardized external PA constriction, proportional to the needle diameter. Both groups, sham and PAB rats, were then maintained for the following 6 weeks when the PAB animals developed permanent PA constriction, leading to RV pressure overload.