Tetralogy of Fallot is a cardiovascular disorder that makes the skin and membranes develop a distinct bluish tinge, due to a lack of adequate oxygen in the blood. It is the result of an amalgamation of defects that include pulmonic stenosis, ventricular septal defects, excessive growth of muscle fibres of the right ventricle, and rotation of the aorta to the right. Dog breeds most susceptible to tetralogy of Fallot are Miniature Schnauzers, Keeshonds, Miniature Poodles, Wire-haired, Fox Terrier and English Bulldogs.
The defects that are associated with this particular condition are dependent on the complexity of the pulmonic stenosis, the extent of the ventricular septal defect, and the total resistance to blood flow offered by the blood vessels. The ultimate outcome may include diminished blood flow to the lungs, generalized oxygen deficit in the blood (leading to a bluish tinge), abnormal red blood cells, production of blood clots and weak blood circulation. Common symptoms in dogs are stunted development, exercise intolerance, fainting, and seizures. Diagnostic techniques include echocardiography, electrocardiographs, and x-rays.
Treatment alternatives comprise surgery and therapeutic management. Though surgery to augment the defects or to minimise the pain can be performed, it is not a common alternative for dogs. In certain instances, reducing pulmonic stenosis makes it possible to lower pain, while beta-adrenergic blocking drugs and bloodletting are viable alternatives in the management of dogs with tetralogy of Fallot. The outlook is not very positive, though dogs with little to moderate shunting may get to adulthood.