Prevalence of Patent Foramen Ovale with Right-to-Left Shunting in Dogs with Pulmonic Stenosis

Background Right-to-left (R-L) shunt caused by patent foramen ovale (PFO) concurrent with pulmonic stenosis (PS) is considered common, although there is a lack of published evidence. Objectives To investigate the prevalence of R-L shunt caused by a PFO in dogs with PS. Animals Thirty-one client-owned dogs with PS, without obvious extracardiac disease detected on the clinical examinations. Methods Case control study: R-L shunt probably caused by PFO was diagnosed when IV injected microbubbles appeared at the left atrial level with an intact atrial septum on echocardiography (bubble-positive dogs). The severity of PS concurrent tricuspid regurgitation (TR), relative thickness of the right ventricle, and relative right atrial area were compared between bubble-positive and bubble-negative dogs. Results The prevalence of R-L shunts caused by PFO was 39% (12 of 31 cases). The instantaneous pressure gradient (PG) across the pulmonic valve and relative thickness of the right ventricle were significantly increased in bubble-positive compared with those in bubble-negative dogs. None of the dogs with mild or moderate PS (pressure gradient