Objective: To determine the anatomy expression of the left coronary artery and its branches in the horse. Methods: The left coronary artery of 120 hearts of horse were perfused with semi-synthetic resin (85% Palatal GP40L with 15% styrene) and mineral red dye. A digital calibrator (Mitutoyo®) was used to measure the external diameter of the left coronary artery and its branches. The samples were assessed for the existence of myocardial bridges. The findings obtained were compared with those from humans, donkeys, pigs, elephants, and camels. Results: The left coronary artery had a diameter of 6.76 ± 2.1 mm. It bifurcated into the paraconal interventricular branch and the left circumflex branch in 113 specimens (94.2%). The proximal diameter of the paraconal interventricular branch was 5.62 ± 1.97 mm, and it ended at the apex in most cases (65.8%). The left circumflex branch was short and ended as a left marginal branch in 55 samples (45.8%); its proximal diameter was 4.05 ± 1.49 mm. The sinoatrial node branch originated from the left circumflex branch in 100% of the cases. The left marginal branch was found in 92 specimens (76.7%), and ended primarily at the upper third of the obtuse margin of the heart. Discussion: The sinus node branch emerging in all cases from the left circumflex branch differs from what has been observed in other species. Due to its similarity with the human heart, we may ratify the equine model for both procedural and hemodynamic applications
