Felis ISSN 2398-2950

Heart: atrial septal defect

Synonym(s): ASD

Contributor(s): Serena Brownlie, Phil Fox, Philip K Nicholls, Liz Bode

Introduction

  • Uncommon, often associated with other defects. Rare as isolated defect.
  • Cause: anomalous formation of cardiac septa.
  • Signs: usually asymptomatic; rarely a clinical problem as shunting velocity low due to small pressure difference between atria.
  • Diagnosis: clinical examination, radiography, electrocardiography, 2-D and Doppler echocardiography.
  • Treatment: medical treatment of congestive heart failure  Heart: congestive heart failure, surgery to close defect.
  • Prognosis: good in asymptomatic cases; other cases depend on complexity of defects.

Pathogenesis

Etiology

  • Embryological failure of normal development of the interatrial septum. Septal defects can be high in the region of the fossa ovale (secundum defect), or result from anomalous development of septum primum or endocardial cushions (ostium primum defect).
  • Rarely identified forms of ASD include sinus venosus ASD, seen high in the atrial septum adjacent to cranial or caudal vena cava and coronary sinus ASD where there is communication between the coronary sinus and left atrium. 

Specific

  • Hereditary?

Pathophysiology

  • Atrial septal defect allows communication between left and right atria; producing shunting of blood between the atria.
  • Normally left to right shunt; large shunts may result in volume overload of the right atrium and ventricle, leading to pulmonary overperfusion, pulmonary hypertension and right ventricular hypertrophy. Right-sided CHF may ensue.
  • Left-to-right atrial shunt  →  overloads right atrium and ventricle  →  increased right atrial and right ventricular pressures  →  overcirculation of lungs  →  left atrium (and left ventricle).
  • If pulmonary overcirculation is sufficient  →  vascular changes  →  pulmonary hypertension   →   right ventricular hypertrophy (but rarely right-sided CHF).
  • Pulmonic stenosis and pulmonary hypertension may result in right-to-left shunting of blood and cyanosis.
  • Atrial stretch  →  dysrhythmias (especially atrial) Heart: dysrhythmia.

Timecourse

  • From birth.

Diagnosis

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Treatment

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Schrope D (2013) Atrioventricular septal defects: natural history, echocardiographic, electrographic and radiographic findings in 26 cats. J Vet Cardiol 15 (4), 233-242 PubMed.
  • Moise N S (1989) Doppler echocardiographic evaluation of congenital cardiac disease - An introduction. J Vet Intern Med (4), 195-207 PubMed.
  • Bonagura J D, Herring D S (1985) Echocardiography - congenital heart disease. Vet Clin North Am Small Anim Pract 15 (6), 1195-1208 PubMed.
  • Farrow C S (1984) Atrial septal defect in a kitten. Mod Vet Pract 65 (4), 281-282 PubMed.


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