Congenital heart

Question 1

what is the effect of a atrial septal defect in horses?

Answer 1

clinical significance unknown
in foetus the blood flow is right to left, in adult it is left to right due to the changes in pressure

Question 2

what is the clinical significane of ventral septal defects?
what is the prognostic criteria?

Answer 2

• Most common congenital heart defect with some breed predisposition (Section A Welsh Mountain ponies, standardbreds, arabians)
• Can be a component of more complex congenital cardiac defects
• Prognostic criteria
  ◦ Size of VSD - small defect = better prognosis
  ◦ Size of cardiac chambers - reflect cardiac workload and the possibility of volume overload
  ◦ Maximal shunt velocity - smaller defect = higher velocity and therefore higher velocity = better
  ◦ Presence of significant AR or MR
  ◦ Pulmonary HyperTension
  ◦ CHF

Question 3

what is the prognosis of horses with VSD?

Answer 3

• The horse with a small VSD has an excellent prognosis and should experience a normal performance life (less than 2cm in diameter)
• Moderate defects are often well-tolerated at rest; although performance in high-intensity sports might be affected
• Progressive MR or AR and cardiac remodeling can facilitate the development of Atrial Fibrillation, Pulmonary hypertension or Left Ventricular Dilation with progressively negative impact on exercise capacity and eventually on survival
• The finding of a large diameter, unrestrictive VSD has a poor prognosis and shortened life expectancy
• These should be examined annually and consider affected horses unsuitable for breeding