The ventricular septal defect is usually a large defect that often occurs at the insertion for the overriding aorta, thereby facilitating the aorta’s connection to both ventricles. Right ventricular hypertrophy occurs in response to the increased R ventricle _____________ caused by the pulmonary artery stenosis. The right ventricle contracts more forcefully to move a larger volume of blood into the pulmonary artery, causing the hypertrophy of the ventricular myocardium. The Tetralogy of Fallot is seen clinically as ____________ at birth, heart murmur, poor growth and development, dyspnea, exercise intolerance, syncope, brain damage and death.
Diagnosis is made through clinical signs and symptoms, radiography and EKG.
Treatment is the administration of beta-blockers, morphine and epinephrine.
Prognosis is poor, though spontaneous resoloution of the ventricular septal defect and the overriding aorta may occur in some individuals with growth. Prognosis for athletic performance is grave as stenosis and ventricular hypertrophy are not likely to reverse. Animals affected by the Tetralogy of Fallot, or those who are closely related to affected individuals should not be used for breeding as this condition is thought to run in families.
Tricuspid Atresia
Tricuspid atresia describes the congenital ______________ of the tricuspid valve that normally connects the right atrium and the right ventricle. The absence of this valve prevents the flow of blood into the right ventricle, and therefore prevents blood from entering the pulmonary artery and reaching the lungs for oxygenation. Often there is a secondary defect seen in conjunction with tricuspid atresia that allows communication of the right and left sides of the heart, which allows the foal to survive for a short period of time, however the blood becomes progressively more deoxygenated, and the foal eventually dies from __________________________________. Tricuspid atresia is seen clinically as cyanosis, fatigue, dyspnea, heart murmur, recumbency and death. Diagnosis can be made through clinical signs and symptoms, blood analysis revealing __________ of blood and EKG. There is no treatment for tricuspid atresia in the horse. Euthanasia may be recommended if diagnosis is confirmed through EKG.
This condition is considered rare and may account for some still births.
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