**Abstract**

Four pulmonary veins come from respective lung lobes drain oxygen-rich blood back to the left atrium. Failure of incorporation with the left atrium can lead to a condition, called Cor triatriatum sinister, that the left atrium is separated into two chambers by an abortive fibrous tissue. The venous system of lung and whole body communicate with each other in the earlier time and they will be disconnected in the following developmental process. Total or partial anomalous pulmonary venous connection refers to that there is/are some degree of the communication exists after birth, which can occur in different sites. In the veterinary field, retrospective studies and several case reports have been published to describe these rare congenital cardiovascular diseases in several species. More cases are need for better understanding their clinical manifestation, treatment options and outcomes.

**Keywords:** congenital, development, Cor triatriatum sinister, anomalous pulmonary venous connection, outcome
