Cor triatriatum

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Marked abdominal distension in a pup with cor triatriatum[1]
Gross heart showing cor triatriatum defect, with anomalous partitioning of the right atrium by a septum or diaphragm. Small arrows indicate the axial edge of the septum orifice. Ref name="Cor" />

Cor triatriatum is a rare congenital heart disease of dogs characterized by the atrium partitioned into two compartments, effectively creating a triatrial heart. In dogs, cor triatriatum dexter (involving the right atrium) is common[2].

It is thought that the abnormal partitioning results from persistent valve remnants of the sinus venosus[3].

This defect primarily affects young large purebred dogs including the Boxer[4], Chow Chow[5], Cocker Spaniel[6], English Bulldog[7], German Shepherd[8], German Short-haired Pointer[9], Golden Retriever[10], Greyhound and Rottweiler.

This disease is not dissimilar clinically from subaortic stenosis[11]. Cases of cor triatriatum in older dogs is not uncommon.

Clinical signs are normally seen in young dogs (under 12 months of age) and usually present with signs of right-sided congestive heart failure, including tachypnea, decreased appetite, exercise intolerance, syncope, ascites and pale mucus membranes. A cough may be present intermittently, indicative of cardiogenic pulmonary edema.

A tentative diagnosis can be established by auscultation of a harsh holosystolic ejection murmur at the left cardiac apex[12]. The intensity of the murmur correlates fairly well with the degree of stenosis and may increase as animals mature, reflecting progressive stenosis. Puppies without detectable murmurs should not be considered free of disease until they reach 6 months of age.

Radiographically, there is variable right ventricular enlargement and pleural effusion.

Electrocardiographic examinations can be misleading as this syndrome can be confused with double-chambered right ventricle[13].

Diagnosis can be confirmed by cardiac catheterization[14], or use of M-mode and Doppler echocardiography, which usually reveal an abnormal membrane in the right atrium and retrograde flow in the caudal vena cava[15].

A differential diagnosis would include subaortic stenosis, ventricular septal defect[16], double-chambered right ventricle[17], hyperthyroidism, cardiomyopathy, Duchenne muscular dystrophy, endocarditis, pulmonic stenosis, mitral valve endocardiosis and infections with Dirofilaria spp.

The prognosis for animals with clinical signs of congestive heart failure is poor

Medical therapy is currently the recommended treatment option, consisting of exercise restriction, atenolol, pimobendan[18] and taurine supplementation.

Surgical intervention can be employed in severe cases with balloon catheterization and cutting of the pinpoint opening in the abnormal membrane[19]. Post-operative complications have been reported, particularly transient tricuspid regurgitation[20]

Balloon dilatation may be an alternative surgical procedure in cases where bypass facilities are unavailable[21][22].


  1. Duncan RB et al (1999) Cor triatriatum dexter in an English Bulldog puppy: case report and literature review. J Vet Diagn Invest 11(4):361-365
  2. Mitten RW et al (2001) Diagnosis and management of cor triatriatum dexter in a Pyrenean mountain dog and an Akita Inu. Aust Vet J 79(3):177-180
  3. Doucette J & Knoblich R (1963) Persistent right valve of the sinus venosus, so-called cor triatriatum dextrum: review of the literature and report of a case. Arch Pathol 75:105–112
  4. Höglund K et al (2007) Time-frequency and complexity analyses for differentiation of physiologic murmurs from heart murmurs caused by aortic stenosis in Boxers. Am J Vet Res 68(9):962-969
  5. Fossum TW & Miller MW (1994) Cor triatriatum and caval anomalies. Semin Vet Med Surg Small Anim 9:177–184
  6. Otto CM et al (1990) Cortriatriatum dexter with Budd-Chiari syndrome and review of ascites in young dogs. J Small Anim Pract 31:385–389
  7. Jevens DJ et al (1993) Cor triatriatum dexter in two dogs. J Am Anim Hosp Assoc 29:289–283
  8. Brayley KA et al (1994) Cor triatriatum dexter in a dog. J Am Anim Hosp Assoc 30:153–156
  9. Tobias AH et al (1993) Cor triatriatum dexter in two dogs. J Am Vet Med Assoc 202:285–290
  10. van der Linde-Sipman JS & Stokhof AA (1974) Triple atria in a pup. J Am Vet Med Assoc 165:539–541
  11. Chetboul V et al (2006) Congenital heart diseases in the boxer dog: A retrospective study of 105 cases (1998-2005). J Vet Med A Physiol Pathol Clin Med 53(7):346-351
  12. Höllmer M et al (2008) Aortic stenosis in the Dogue de Bordeaux. J Small Anim Pract 49(9):432-437
  13. López-Alvarez J et al (2011) Balloon dilation of an imperforate cor triatriatum dexter in a Golden Retriever with concurrent double-chambered right ventricle and subsequent evaluation by cardiac magnetic resonance imaging. J Vet Cardiol 13(3):211-218
  14. Nieuwland J et al (2010) Resolution of ascites after successful balloon dilatation of cortriatriatum dexter in a dog. Tijdschr Diergeneeskd 135(8):330-333
  15. Szatmári V et al (2000) Doppler-ultrasonographic detection of retrograde pulsatile flow in the caudal vena cava of a puppy with cor triatriatum dexter. Vet Rec 147(3):68-72
  16. Guglielmini C et al (2002) Atrial septal defect in five dogs. J Small Anim Pract 43(7):317-322
  17. Fukushima R et al (2011) Epidemiological and morphological studies of double-chambered right ventricle in dogs. J Vet Med Sci 73(10):1287-1293
  18. Boswood A (2010) Current use of pimobendan in canine patients with heart disease. Vet Clin North Am Small Anim Pract 40:571–580
  19. Leblanc N et al (2012) Cutting balloon catheterization for interventional treatment of cor triatriatum dexter: 2 Cases. J Vet Cardiol Nov 21
  20. Chanoit G et al (2009) Transient tricuspid valve regurgitation following surgical treatment of cor triatriatum dexter in a dog. J Small Anim Pract 50(5):241-245
  21. Tanaka R et al (2003) Surgical correction of cor triatriatum dexter in a dog under extracorporeal circulation. J Small Anim Pract 44(8):370-373
  22. Johnson MS et al (2004) Management of cor triatriatum dexter by balloon dilatation in three dogs. J Small Anim Pract 45(1):16-20