First-Ever Case: Congenital Left Coronary–Pulmonary Artery Fistula Identified in an Asymptomatic Dog

Case report of an incidental left coronary artery to main pulmonary artery fistula in a dog

C. F. Agudelo, B. Lukac, A. Bockay, V. Vargova, G. Kackova, M. Figurova, S. Hornak

Background

A coronary artery fistula (CAF) is an uncommon congenital or acquired anomaly involving an abnormal communication between a coronary artery and a cardiac chamber or great vessel, bypassing the myocardial capillary bed. CAFs are rarely documented in veterinary medicine, accounting for roughly 0.9% of canine cardiac diseases. In humans, the majority drain into the right heart, with only a minority connecting to the main pulmonary artery (MPA). This report describes the first documented case of a congenital fistula between the left coronary artery (LCA) and the MPA in a dog, incidentally discovered during pre-anesthetic evaluation.

Methods / Case Presentation

A 3-year-old, 14-kg, female Tatra hound underwent routine pre-anesthetic assessment prior to orthopedic radiography. The dog was asymptomatic and clinically normal. Standard electrocardiography revealed sinus arrhythmia at 100 bpm. Transthoracic echocardiography (TTE) showed dilation of the left coronary ostium and continuous turbulent flow from the left coronary cusp to the MPA, observed on color Doppler in both systole and diastole (velocity ≈0.8 m/s). These findings suggested a coronary fistula, later confirmed by computed tomography (CT) imaging under general anesthesia. CT demonstrated a short LCA dividing into the left circumflex and paraconal arteries, with the latter forming a tortuous channel that terminated directly in the MPA.

Routine bloodwork, including cardiac biomarkers (troponin I = 0.05 ng/mL; NT-proBNP <500 pmol/L), showed no myocardial injury or pressure overload. The dog tolerated anesthesia well and remained asymptomatic following recovery.

Results

Imaging confirmed a congenital, solitary macrofistula between the LCA and MPA, without evidence of aneurysm, chamber enlargement, or volume overload. No clinical or biochemical signs of myocardial ischemia, pulmonary hypertension, or coronary steal syndrome were observed. Mild pulmonary regurgitation and minimal bulging of the ascending aorta were noted radiographically but were not clinically significant. Follow-up evaluations revealed no progression or new symptoms.

Limitations

Diagnostic clarity was limited by the moderate resolution of the 16-slice CT scanner and motion artifacts, which reduced visualization of smaller coronary structures. Coronary angiography—the gold standard for CAF diagnosis—was not performed due to technical limitations. Advanced imaging such as transesophageal or 3D echocardiography might have provided additional anatomical detail.

Conclusions

This report presents the first documented case of a congenital left coronary artery to main pulmonary artery fistula in a dog. The condition was incidentally discovered and remained clinically silent, with no evidence of hemodynamic compromise. Echocardiography combined with CT provided a comprehensive, non-invasive diagnostic approach. Asymptomatic CAFs of this nature may not require intervention, but awareness is crucial for accurate differential diagnosis in veterinary cardiology and for preventing misinterpretation during imaging.

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