Tetralogy of fallot

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  • About 6% of feline congenital heart defects.
  • Cause : combination of defects - pulmonic stenosis, high ventricular septal defect (VSD), dextroposition/overriding aorta; plus right ventricular hypertrophy.
  • Signs : usually stunted and cyanotic.
  • Diagnosis : radiographic signs of right-sided enlargement, cardiac murmur, ultrasonography.
  • Treatment : none to medical to cardiac surgery, depends on severity.
  • Prognosis : poor to grave.


Clinical signs

  • Cyanosis, affecting cranial and caudal mucosae uniformly.
  • Dyspnea and tachypnea.
  • Murmurs  [Cardiac sounds: overview]  - forward of left heart base (pulmonic stenosis); right sternal border (VSD).
  • Signs of right-sided congestive heart failure, eg hepatomegaly, ascites (rare).


Differential diagnosis

Systolic murmurs in young cats



  • Poor if mild.
  • Hopeless if severe.

Expected response to treatment

  • Exercise tolerance.
  • PCV.

Reasons for treatment failure

  • Severity of defect.
  • Thrombosis of surgically induced shunt.
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