Multimodal imaging of a coronary artery fistula in a Welsh Springer spaniel

A four-year-old intact male Welsh Springer spaniel was presented for a prebreeding evaluation. Thoracic auscultation revealed a grade 2/6 left basilar systolic murmur. Echocardiography demonstrated left atrial and left ventricular dilation with systolic dysfunction, including a left atrium-to-aortic root ratio of 2.24, normalized left ventricular internal dimension in diastole of 2.44, and fractional shortening of 19%. Color and spectral Doppler interrogation identified continuous flow with a peak velocity of approximately 1.5 m/s in the left pulmonary artery. Transesophageal echocardiography, selective angiography, and computed tomography angiography combined revealed a complex, anomalous coronary artery conformation. Branches of the left and right coronary arteries formed two major tortuous vascular plexuses: a cranial one that drained into the pulmonary artery via a multitude of small fistulous openings, and a caudal one that drained into a branch of the celiac artery. These findings confirmed a diagnosis of a complex coronary artery fistula. Because the supernumerary openings meant surgical ligation or interventional embolization could not guarantee complete closure, medical management with oral pimobendan was elected. Three years after the initial diagnosis, the dog developed atrial fibrillation and right-sided congestive heart failure. Despite the escalation of medical therapy, the dog died four months later. This case highlights the rare anatomical presentation and severe long-term hemodynamic consequences of a complex, untreated coronary artery fistula in a dog.