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Conotruncal Heart Malformations
Defective development of the cardiac outflow tract results in congenital cardiac anomalies that are known clinically as conotruncal defects. Conotruncal defects (CTDs) are a group of genetically and embryologically related heart malformations inherited as autosomal recessive trait which occur both in humans and dogs.
Conotruncal abnormalities involve defects at the junction of the ventricular infundibulum (conus arteriosus, the funnel-shaped portion of the right ventricle at the entrance to the pulmonary trunk) with the great arteries, or, embryologically, truncus arteriosus (an artery connected with fetal heart) 5.
The most common form of CTDs in dogs is tetralogy of Fallot, which consists of ventricular septal defect, pulmonic stenosis, overriding of the aorta, and right ventricular hypertrophy.
The location of the abnormality in the dividing wall, and the heart structures involved, will create different syndromes that have similar presenting signs. For example, pulmonic stenosis causes a pot-bellied appearance due to fluid retention in the abdomen and an enlarged liver. Fluid accumulation in the hindlegs may also be seen. Affected dogs may show signs of reduced ability to exercise, difficulty breathing and stunted growth. Ventricular septal defect also causes a pot-bellied appearance, with fluid retention and an enlarged liver. Affected dogs will pant a lot and will have trouble breathing. Other signs are weakness and weight loss, and these dogs may have difficulty exercising. The gums may be bluish due to the resulting low blood oxygen levels 4.
The results of breeding experiments conducted in a colony of Keeshond dogs with conotruncal septal defects confirmed the hereditary nature of the abnormality but were not consistent with any simple genetic hypothesis. Both the incidence and the severity of the conotruncal lesions increased with the severity of the parental defect.
References
- The Keeshond defect in cardiac conotruncal development is oligogenic. Petra Werner. Human Genetics. Volume 116, Number 5/April, 2005
- A single major-gene defect underlying cardiac conotruncal malformations interferes with myocardial growth during embryonic development: studies in the CTD line of Keeshond dogs. Patterson DF, Pexieder T, Schnarr WR, Navratil T, Alaili R.
- Hereditary defects of the conotruncal septum in Keeshond dogs: Pathologic and genetic studies. Donald F. Patterson DVM, DSc, FACC , Robert L. Pyle VMD, MSc , Lodewyk Van Mierop MD, FACC , Julius Melbin VMD, PhD and Marcia Olson BA
- Disorder - Conotruncal heart malformation
- Mario J. Garcia. Noninvasive Cardiovascular Imaging: A Multimodality Approach
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