At presentation, Sadie was a 3-year-old, intact female, mixed-breed dog with a chief complaint of a heart murmur and a history of collapse after exertion. Examination revealed a 5/6 systolic murmur on the left, with a diastolic component, at times taking on a continuous character. Femoral pulses were weak, and examination was otherwise unremarkable. Radiographs revealed generalized cardiomegaly, hypervascular lungs, and dilatation of the aortic arch. Her differential diagnosis included subaortic stenosis (SAS) with aortic insufficiency (AI), and a patent ductus arteriosus (PDA). An echocardiogram revealed a subaortic ridge, left ventricular hypertrophy, and enlargement of the left atrium, consistent with SAS. Continuous wave Doppler showed turbulent flow in the aortic outflow tract, increased outflow velocity of 6 m/s, and aortic insufficiency. The PDA was also observed, with Doppler showing continuous blood flow through the ductus. Her final diagnosis was severe SAS with AI, and a PDA. The PDA was treated via transcatheter coil occlusion in order to resolve the PDA and the associated left ventricular volume overload which was exacerbating the stenosis. After surgery, echocardiographic evaluation showed 90% closure of the PDA, and diminished aortic outflow velocity (3.9 m/s). Her diagnosis was downgraded to mild to moderate SAS, and her prognosis upgraded to good.