Use of ambrisentan in the management of refractory pulmonary arterial hypertension following occlusion of a bidirectionally shunting patent ductus arteriosus in a dog.

Ambrisentan-based combination therapy enabled successful management of refractory PAH after bidirectional PDA occlusion in a dog.

This case report describes the successful management of refractory pulmonary arterial hypertension (PAH) in a 9-year-old intact male Pomeranian following transcatheter occlusion of a bidirectionally shunting patent ductus arteriosus (PDA). The dog presented with a 2-day history of anorexia and lethargy, and echocardiography confirmed bidirectional PDA shunting with concurrent PAH. Despite successful transcatheter ductal occlusion, the patient developed right-sided congestive heart failure secondary to persistent PAH postoperatively. A multimodal pharmacological approach was employed, incorporating ambrisentan (an endothelin receptor antagonist), sildenafil (a phosphodiesterase-5 inhibitor), pimobendan (an inodilator), and amlodipine (a calcium channel blocker). This combination therapy resulted in resolution of right-sided congestive heart failure and elimination of oxygen dependency. Serial echocardiographic and thoracic radiographic monitoring demonstrated progressive cardiac reverse remodeling, ultimately achieving a structurally normal cardiac architecture. The patient remained clinically stable at last follow-up without procedure-related complications. This case is clinically significant as it demonstrates that bidirectional PDA occlusion, historically considered high risk due to potential for acute right heart decompensation post-closure, can be performed successfully when coupled with aggressive postoperative PAH-targeted therapy. The novel inclusion of ambrisentan in a veterinary patient highlights the potential role of endothelin receptor antagonism as a key component of combination PAH therapy in dogs.

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