Congenital Heart Defect, Atrial Septal Defect in Dogs

Atrial septal defect (ASD) is a congenital heart condition that enables blood flow between the left and right atria via the interatrial septum which is the wall separating the two atrial chambers. ASD occurs in one of three locations

Lower atrial septum or ostium primum defect, which is the most common,

Near the fossa ovalis or ostium secundum defect,

Craniodorsal to the fossa ovalis or sinus venous defect.

Typically, the blood will shunt into the right atrium, causing a volume overload to the right atrium, right ventricle, and pulmonary vasculature, which can sometimes lead to pulmonary hypertension. However, if right-sided pressures are too high, shunting may occur right to left, causing generalized cyanosis. Common signs associated with ASD include:

Exercise intolerance

Fainting/loss of consciousness (syncope)

Trouble breathing (dyspnea)


Heart murmur

Bluish skin (cyanosis)

Fluid buildup in the abdomen (ascites)

Heart failure 

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