Tetralogy of Fallot in Dogs

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Tetralogy of Fallot is a congenital defect of the heart that involves four abnormalities: ventricular septal defect (a hole between the two ventricles), pulmonic stenosis (obstruction of blood flow through the pulmonary valve), an overriding aorta, and right ventricular hypertrophy (thickening of the heart muscle).

Symptoms and Types

  • Weakness
  • Fainting
  • Shortness of breath
  • Cyanosis


Tetralogy of Fallot is a congenital disease that likely is influenced by genetic factors. Keeshonds and English bulldogs are predisposed.


Your veterinarian will start with a physical examination on your dog, which may reveal a heart murmur. Routine blood testing may be recommended. Your veterinarian will likely want to take radiographs (X-rays) of the heart and an ultrasonic study of the heart (known as an echocardiogram) will probably be necessary as well. Other testing that may be pursued include an electrocardiogram (ECG), pulse oximetry (measurement of hemoglobin saturation), and/or angiocardiography.

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