Bovis ISSN 2398-2993

Ventricular septal defect

Synonym(s): VSD, congenital heart disease

Contributor(s): Louise Cox-O’Shea , Gayle Hallowell

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Introduction

  • The most common congenital cardiac defect in cattle.
  • Cause: congenital.
  • Signs: variable.
  • Diagnosis: auscultation of characteristic murmur/murmurs and visualization of lesion on echocardiography.
  • Treatment: none currently available; palliative if heart failure results.
  • Prognosis: dependent on position and size.

Pathogenesis

Etiology

  • A defect in the ventricular septum of varying size  .
  • Usually the defect is in the membranous portion of the ventricular septum beneath the aortic valve (perimembranous and subaortic).
  • Defects in the membranous portion are caused by lack of fusion of the atrioventricular endocardial cushion and the muscular ventricular septum.
  • Occasionally the defect occurs in the infundibular or outflow portion of the membranous septum with the result that shunted blood enters the RV close to the pulmonary valve (subpulmonic).
  • Defects in the muscular portion (rare) are caused by abnormal development of the bulbous cordis.
  • May occur alone or as part of a complex of malformations, e.g. Tetralogy of Fallot.

Pathophysiology

  • Hemodynamic effect of a VSD depends on the size and amount of blood shunted through it.
  • Blood flows from the high pressure left ventricle to the low pressure right ventricle.
  • If a large proportion of the LV stroke volume is shunted this will   →    pulmonary overcirculation and volume overload primarily of the LA.
  • Increased pulmonary and left atrial pressures can result in secondary right ventricular failure.  
  • Flow across the defect depends both on the size of the defect and on the pressure differential between the LV and RV; an increase in RV pressure will   →    a decreased flow across the VSD.
  • A reverse shunt (Eisenmenger's syndrome) can theoretically occur if there is a very large defect and substantial increase in RV pressure.
  • Turbulence can lead to damage to the endocardium which in turn can predispose to bacterial endocarditis of the tricuspid valve.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed Papers

  • Recent references from PubMed and VetMed Resource.
  •  Buczinski S, Fecteau G & Difruscia R (2006) Ventricular septal defects in cattle: A retrospective study of 25 cases. Can Vet J  47 (3), pp 246-252 PubMed.
  • Pipers F S et al (1985) Echocardiographic detection of ventricular septal defects in large animals. JAVMA 187 (8), pp 810-816 PubMed.


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