Tricuspid Valve Dysplasia
The condition should be described as a congenital malformation of the tricuspid valve (right atrioventricular valve) and its supporting structures (chordae tendineae, papillary muscles, valvular leaflets) resulting in tricuspid stenosis (narrowing) or regurgitation (insufficiency). Tricuspid valve dysplasia leads to increased volume load on the right atrium and ventricle towards the end of diastole. A stenotic tricuspid valve can limit ventricular filling during diastole and increased pressure as a result of increased volume can cause right-sided congestive heart failure.
This is a condition which is common in dogs and cats, quite common in horses and rare in large animals. Predisposed breeds of dog include the Labrador Retrievers, German Shepherds, Boxers and Great Danes. It is the second most common congenital abnormality seen in cats.
Often presence of a murmur on physical exam is the only clinical sign. Other clinical signs vary depending on the severity of the disease but will include exercise intolerance, dyspnea, weight loss, poor appetite and abdominal distension.
Physical examination findings will reveal a right-sided soft systolic murmur (tricuspid regurgitation), a right-sided diastolic murmur and jugular pulses and distension in severe cases. Femoral pulses are usually normal to weak and there may be signs of right-sided congestive heart failure in severe cases.
Radiographic findings may include right atrial and right ventricular enlargement, caudal vena cava enlargement, pulmonary underperfusion and signs of right sided heart failure.
Echocardiographic findings include right ventricular and atrial dilation and abnormalities of the tricuspid valve. Doppler shows tricuspid regurgitation and/or stenosis.
Electrocardiographic (ECG) study can show classic signs of right atrial and ventricular enlargement, atrial arrhythmias as well as ventricular conduction problems.
Treatment is usually palliative. Signs of right sided congestive heart failure can be controlled pharmacologically, as can arrhythmias. Thoracocentesis should be performed when needed to relieve pleural effusion. Abdominocentesis when needed to relieve peritoneal effusion.
Mild to moderate cases can lead a normal life. Severe cases have a poor prognosis, however, if heart failure is controlled these patients can live several years.
Ettinger, S.J. and Feldman, E. C. (2000) Textbook of Veterinary Internal Medicine Diseases of the Dog and Cat Volume 2 (Fifth Edition), W.B. Saunders Company
Ettinger, S.J, Feldman, E.C. (2005) Textbook of Veterinary Internal Medicine (6th edition, volume 2), W.B. Saunders Company
Fossum, T. W. et. al. (2007) Small Animal Surgery (Third Edition), Mosby Elsevier
Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition), Merial
Nelson, R.W. and Couto, C.G. (2009) Small Animal Internal Medicine (Fourth Edition), Mosby Elsevier.
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