Atrial septal defect

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Atrial septal defect in an old dog[1]

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[2].

This condition in dogs is relatively rare and is sometimes observed as part of the Tetralogy of Fallot. ASD does not produce severe hemodynamic lesions compared with ventricular septal defect[3].

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[4].

In the Cavalier King Charles Spaniel, ASDs can develop as a sequela of severe mitral regurgitation due to myxomatous mitral valve degeneration.

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[5], mitral valve dysplasia and subaortic stenosis[6][7].

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[8], double-chambered right ventricle[9], 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[10].

References

  1. Cavalcanti, GA et al (2011) Atrial septal defect in an elderly dog. Arq Bras Med Vet Zootec 63(2):April
  2. Liu XY et al (2011) Involvement of a novel GATA4 mutation in atrial septal defects. Int J Mol Med 28(1):17-23
  3. McConkey MJ (2011) Congenital cardiac anomalies in an English bulldog. Can Vet J 52(11):1248-1250
  4. Gerbode F et al (1958) Syndrome of left ventricular-right atrial shunt. Ann Surg 148:433–466
  5. García-Rodríguez MB et al (2009) Complex cardiac congenital defects in an adult dog: an ultrasonographic and magnetic resonance imaging study. Can Vet J 50(9):933-935
  6. Chetboul V et al (2006) Congenital heart diseases in the boxer dog: A retrospective study of 105 cases (1998–2005). J Vet Med A Physiol Pathol Clin Med 53:346–351
  7. Chetboul V et al (2006) Retrospective study of 156 atrial septal defects in dogs and cats (2001–2005). J Vet Med A Physiol Pathol Clin Med 53:179–184
  8. Guglielmini C et al (2002) Atrial septal defect in five dogs. J Small Anim Pract 43(7):317-322
  9. Fukushima R et al (2011) Epidemiological and morphological studies of double-chambered right ventricle in dogs. J Vet Med Sci 73(10):1287-1293
  10. Zhu YF et al (2012) Animal Experimental Study of the Fully Biodegradable Atrial Septal Defect (ASD) Occluder. J Biomed Biotechnol 2012:735989
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