Atrial Septal Defect

Atrial septal defect (ASD) is a congenital abnormality of the upper chambers of the heart marked by the failure of the wall between the right and left atria to close completely. Although ASD has been considered relatively rare in veterinary medicine, the current thinking is that its incidence in dogs is in fact much higher than previously thought, representing the second most commonly diagnosed congenital heart defect after mitral valve dysplasia.

Approximately 30% of animals with atrial septal defect also have one or more other congenital heart defects, including mitral valve dysplasia, dilated cardiomyopathy, and subaortic stenosis, one of the most common congenital cardiac anomalies in dogs.4 The Boxer and Domestic Shorthair cat are the most common canine and feline breeds affected.

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Common signs include heart murmur, exercise intolerance, fainting, difficulty breathing and cough, although the majority of afected dogs and cats have no signs at all.2 Modern echocardiographic and Doppler echocardiography currently offer a good view of the abnormalities facilitating earlier detection of ASD in awake animals. The long-term prognosis for dogs with isolated and small-sized ASD is usually good, but can be compromised by the presence of concurrent congenital or acquired cardiac diseases.3


  1. Atrial septal defect
  2. Chetboul V, Charles V, Nicolle A, Sampedrano CC, Gouni V, Pouchelon JL, Tissier R. Retrospective study of 156 atrial septal defects in dogs and cats
  3. Guglielmini C, Diana A, Pietra M, Cipone M. Atrial septal defect in five dogs.

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