CausesBy Mayo Clinic Staff
Atrioventricular canal defect occurs before birth when a baby's heart is developing. Some factors, such as Down syndrome, might increase the risk of atrioventricular canal defect. But the cause is generally unknown.
The normal-functioning heart
The heart is divided into four chambers, two on the right and two on the left.
The right side of your heart moves blood into vessels that lead to the lungs. There, oxygen enriches the blood. The oxygen-rich blood flows back to your heart's left side and is pumped into a large vessel (aorta) that circulates blood to the rest of your body.
Valves control the flow of blood into and out of the chambers of your heart. These valves open to allow blood to move to the next chamber or to one of the arteries, and close to keep blood from flowing backward.
What happens in atrioventricular canal defect
In partial atrioventricular canal defect:
- There's a hole in the wall (septum) that separates the upper chambers (atria) of the heart
- Often the valve between the upper and lower left chambers (mitral valve) also has a defect that causes it to leak (mitral valve regurgitation)
In complete atrioventricular canal defect:
Aug. 14, 2015
- There's a large hole in the center of the heart where the walls between the atria and the lower chambers (ventricles) meet. Oxygen-rich and oxygen-poor blood mix through that hole.
- Instead of separate valves on the right and left, there's one large valve between the upper and lower chambers.
- The abnormal valve leaks blood into the ventricles.
- The heart is forced to work harder and enlarges.
- Fleishman CE, et al. Clinical manifestations, pathophysiology, and diagnosis of atrioventricular (AV) canal defects. http://www.uptodate.com/home. Accessed June 3, 2015.
- Bonow RO, et al. Congenital heart disease. In: Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 10th ed. Philadelphia, Pa.: Saunders Elsevier; 201t. http://www.clinicalkey.com. Accessed June 3, 2015.
- Fleishman CE, et al. Management and outcome of atrioventricular (AV) canal defects. http://www.uptodate.com/home. Accessed June 3, 2015.
- What are holes in the heart? National Heart, Lung, and Blood Institute. http://www.nhlbi.nih.gov/health/health-topics/topics/holes. Accessed June 4, 2015.
- Martin RJ, et al. Genetic and environmental contributions to congenital heart disease. In: Fanaroff and Martin's Neonatal-Perinatal Medicine. 10th ed. Philadelphia, Pa.; Saunders Elsevier; 2015.
- AskMayoExpert. What other conditions are associated with ventricular septal defect (VSD)? Rochester, Minn.: Mayo Foundation for Medical Education and Research; 2014.
- Backer CL. Modified single patch: Are we still worried about subaortic stenosis? Annals of Thoracic Surgery. 2015;99:1671.
- Creasy RK, et al. Fetal cardiac malformations and arrhythmias. In: Creasy and Resnik's Maternal-Fetal Medicine: Principles and Practice. 7th ed. Philadelphia, Pa.: Saunders Elsevier; 2014.
- The impact of congenital heart defects. http://www.heart.org/HEARTORG/Conditions/CongenitalHeartDefects/TheImpactofCongenitalHeartDefects/The-Impact-of-Congenital-Heart-Defects_UCM_001218_Article.jsp. American Heart Association. Accessed June 7, 2015.