Atrial septal defect
Atrial septal defect (ASD) is a congenital heart disease of dogs characterized by shunting of blood from the left to right atrial chambers of the heart. This can also occur due to a patent foramen ovale, which has the same clinical presentation.
ASD is a genetically heterogeneous disease and the genetic determinants remain to be identified.
Although most ASDs are a defect with communication between left and right atria, abnormal ASDs can occur as left ventricular-right atrial communications, known collectively as Gerbode defects.
Approximately 30% of dogs with an atrial septal defect also have one or more other heart defects such as patent ductus arteriosus, persistence of the left cranial vena cava, mitral valve dysplasia and subaortic stenosis.
Clinical signs are normally seen in young dogs (1 - 2 years of age) but can present at an older age with symptoms of generalized weakness, exercise intolerance, syncope and pale mucus membranes. A cough may be present intermittently.
A tentative diagnosis can be established by auscultation of a holosystolic heart murmur and radiographic evidence of cardiomegaly but definitive diagnosis requires use of M-mode and Doppler echocardiography.
Echocardiographs usually elucidate the septal defect and often shows concurrent right ventricular hypertrophy.
A differential diagnosis would include ventricular septal defect, double-chambered right ventricle, hyperthyroidism, cardiomyopathy, Duchenne muscular dystrophy, endocarditis, mitral valve endocardiosis, other causes of congestive heart failure and infections with Dirofilaria spp.
Treatment is usually conservative, with management of the secondary congestive heart failure, but surgical correction can be performed at specialty referral centers via cardiopulmonary bypass using biodegradable atrial septal defect occluders.
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