Tricuspid dysplasia, tricuspid valve dysplasia, TVD
The tricuspid valve is located between the right atrium and the right ventricle. When the tricuspid valve fails, venous blood from the right ventricle flows back into the right atrium. This results in blood backing up into the venous circulation and a reduced supply of oxygen-rich blood to the body. Tricuspid valve dysplasia (TKD) is a congenital malformation of the tricuspid valve apparatus, consisting of tricuspid valve leaflets, chordae tendineae, and ventricular papillary muscles. These structures may be affected individually or in combination. Depending on severity, dogs may show symptoms from birth or later during the first year of life, but no later than the third year of life. In severe cases, symptoms such as fluid accumulation in the abdominal cavity (abdominal dropsy, ascites), liver enlargement (blood backing up in the liver), respiratory distress and cardiac arrhythmias, and brief loss of consciousness (syncope) may occur as a result of the cardiac problems, leading to right heart failure. In rare cases, other congenital heart abnormalities may occur in addition to TKD. TKD in dogs is similar to Ebstein's anomaly in humans.
In the veterinary literature, TKD is among the most commonly described congenital heart defects. The incidence of TKD in dogs ranges from 3.1-8.9%, depending on the study (Tidholm, 1997; Amberger and Lombard, 1998; Buchanan, 1999; Baumgartner and Glaus, 2003; Oliveira et al., 2011). Certain breeds are predisposed to TKD. This supports the assumption of a genetic cause. TKD is most commonly seen in large dog breeds. The most commonly affected breed is the Labrador Retriever (25.7%). Other breeds affected include the Boxer (14.3%), German Shepherd (14.3%), English Bulldog (8.6%), and Golden Retriever (8.6%) (Oliveira et al., 2011), as well as Great Danes, Weimaraners, Irish Setters, and Bobtails (Liu and Tilley, 1976; Kornreich and Moïse, 1997).
There is also some predisposition with respect to sex. For the most part, this is not significant, but males are slightly more commonly affected overall (Tidholm, 1997; Baumgartner and Glaus, 2003). The age at diagnosis averages between 1 month and 3.5 years (Baumgartner and Glaus, 2003; Oliveira et al., 2011).
Several studies already indicate the heritability of TKD. In a study on Labrador retrievers, a very high heritability (h2 = 0.71) was found. Studies on heritability point to a recessive major gene (Famula et al., 2002). Recent pedigree analyses in dogs of the Dogue de Bordeaux breed strengthen the suspicion of an autosomal recessive inheritance (Ohad et al., 2013). However, further pedigree analyses of Labrador retrievers also suggest an autosomal dominant inheritance with incomplete penetrance (Andelfinger et al., 2003). To date, a genomic region linked to TKD is known to be located on canine chromosome 9 (CFA 9) (Andelfinger et al., 2003). Further analysis is needed to further elucidate the genetic variants responsible for TKD. This project aims to identify genetic variants associated with TKD and subsequently elucidate the causative mutations for TKD.
Therefore, we ask you to send EDTA blood samples from Labrador Retrievers and dogs of other breeds. Other breeds that may be considered for the project are:
- Golden Retriever
- Boxer
- German Shepherd
- English Bulldog
- Great Dane
- Weimaraner
- Irish Setter
- Bobtail
- Mongrels
Other documentation:
Please fill out our form (English: Form) and attach a copy of the pedigree, if available, and copies of the heart findings. An echocardiographic examination, including color Doppler if possible, should have been performed. It is very important to indicate the age at the time of the cardiac examination.
Sample submission:
Samples from clearly TKD affected and free dogs are required. Samples from dogs of the above mentioned breeds can be sent. Classification by disease can be done subsequently. The project distinguishes the following categories of samples:
1. status still unknown, findings will be submitted subsequently
2. clinical suspicion of TKD (auscultation findings)
3. TKD, echocardiographic
4. TKD, pathological-anatomical
5. TKD, free, evidence via echocardiography and older than 5 years
References:
Amberger CN, Lombard CW (1998): Prevalence of cardiovascular disease in Switzerland. ESVC Newsletter 2: 17.
Andelfinger G, Wright KN, Lee HJ, Siemens LM, Benson DW (2003): Canine tricuspid valve malformation, a model of human Ebstein anomaly, maps to dog chromosome 9. J Med Genet 40: 320-324.
Baumgartner C, Glaus TM (2003): Angeborene Herzerkrankungen beim Hund: Eine retrospektive Analyse. Schweiz Arch Tierheilkd 145: 527-536.
Buchanan JW (1999): Prävalenz von Herz-Kreislauf-Erkrankungen. In: Fox PR, Sisson DD, Moise NS, Eds. Textbook of Canine and Feline Cardiology. WB Saunders, Philadelphia, 457-470.
Famula TR, Siemens LM, Davidson AP, Packard M (2002): Evaluation der genetischen Basis der Trikuspidalklappendysplasie bei Labrador Retrievern. Am J Vet Res 63: 816-820.
Kornreich BG, Moïse NS (1997): Rechtsatrioventrikuläre Klappenfehlbildung bei Hunden und Katzen: Eine elektrokardiographische Untersuchung mit Schwerpunkt auf gesplitterten QRS-Komplexen. J Vet Intern Med 11: 226-230.
Liu SK, Tilley LP (1976): Dysplasia of the tricuspid valve in the dog and cat: J Am Vet Med Assoc 169: 623-630.
Ohad DG, Avrahami A, Waner T, David L (2013): Das Auftreten und der vermutete Vererbungsmodus von kongenitaler Subaortenstenose und Trikuspidalklappendysplasie bei Bordeauxdoggen. Vet J 197: 351-357.
Oliveira P, Domenech O, Silva J, Vannini S, Bussadori R, Bussadori C (2011):Retrospective Review of Congenital Heart Disease in 976 Dogs. J Vet Intern Med 25: 477-483.
Tidholm A (1997): Retrospektive Studie über angeborene Herzfehler bei 151 Hunden. J Small Anim Pract 38: 94-98.
