Ventricular septal defect


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  • Second most common congenital heart defect after aortic valve dysplasia; 21% of feline congenital heart anomalies.
  • Isolated subaortic lesion communicating ventral to septal tricuspid valve leaflet frequently identified, larger defect typical of tetralogy of Fallot.
  • Occasionally combined with atrial septal defect producing common atrioventricular canal.
  • Cause : congenital abnormality, resulting from anomalous formation of cardiac septa.
  • Signs : vary from asymptomatic murmur to severe congestive heart failure.
  • Diagnosis : auscultation, radiography, electrocardiography, ultrasonography.
  • Treatment : medical management, surgery considered for severe cases.
  • Prognosis : good with restrictive asymptomatic cases; poor with severe defects.
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Clinical signs

  • Diagonal murmur - harsh, holosystolic murmur with point of maximum intensity on the right, but murmur may also be heard over mitral valve.
  • A murmur of relative pulmonic stenosis may be heard at left base of heart.
  • Left-sided congestive heart failure (CHF).
  • Eisenmenger's syndrome - marked dyspnea; cyanosis of mucous membranes; murmur may be reduced or absent.


Differential diagnosis

Systolic murmurs in young cats



  • Good - if mild, restrictive; normal life.
  • Poor - if severe, cats with unrestrictive defects usually develop CHF within first few weeks of life.
  • Hopeless - if Eisenmenger's syndrome.

Expected response to treatment

  • Control of congestive heart failure (if present).
  • Control of any dysrhythmias (if present).

Reasons for treatment failure

  • Lesion too severe.
  • Poor response to medical treatment.
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