September 14, 2022
Years published: 1986, 1994, 2005
Atrioventricular septal defect (AVSD) is a general term for a group of rare heart defects that are present at birth (congenital). Infants with AVSDs have improperly developed atrial and ventricular septa and adjoining valves.
The normal heart has four chambers. The two upper chambers, known as atria, are separated from each other by a fibrous partition called the atrial septum. The two lower chambers, known as ventricles, are separated from each other by the ventricular septum. Valves (e.g., mitral and tricuspid) connect the atria (left and right) to their respective ventricles. The valves allow for blood to be pumped through the chambers. Blood travels from the right ventricle through the pulmonary artery to the lungs where it receives oxygen. The blood returns to the heart through pulmonary veins and enters the left ventricle. The left ventricle sends the now oxygen-filled blood into the main artery of the body (aorta). The aorta sends the blood throughout the body.
The parts of the heart described above are formed from an embryonic structure called the endocardial cushions. In individuals with AVSD there is some combination of malformation of these parts of the heart. They may include a hole in the atrial septum, a hole in the ventricular septum, and/or abnormalities of the mitral and triscupid valves. AVSD may be classified as one of three forms: an incomplete (or partial) AVSD (atrial septal defect primum); a transitional form (atrial septal defect and small ventricular septal defect); or a more severe or complete form (large atrial and ventricular defects).
The symptoms of AVSD vary greatly and depend on the severity of the malformations (e.g., valve leakage between ventricles and ventricular size). About half the cases of AVSD occur in children with Down syndrome.
Infants with the complete form of atrioventricular septal defect usually develop a limited ability to circulate blood to the lungs and the rest of the body resulting in fluid buildup in the heart, lung and various body tissues (congestive heart failure). Pulmonary congestion may lead to difficulty breathing (dyspnea) and fatigue. Infants with complete atrioventricular septal defect often have a bluish discoloration of the skin and mucous membranes (cyanosis) due to insufficient oxygen supply to these tissues.
Other symptoms that may occur in all forms of AVSD include poor feeding, abnormally rapid breathing (tachypnea), excessive sweating, and/or an abnormally rapid heartbeat (tachycardia).
Frequent episodes of acute inflammation of the lungs (pneumonia) and bronchial tubes (bronchitis) are common in children with all forms of AVSD. Abnormally high pressure within the artery that leads to the heart from the lungs (pulmonary artery) may impair lung function and result in permanent pulmonary vascular disease before the age of 1 year. Some more severely affected infants may have congestive heart failure as a direct result of these serious complications.
Older children with untreated AVSD may be at risk for brain abscesses, the development of blood clots (thrombosis) that may travel and lodge in the arteries (embolism), and/or acute inflammation of the inner membranes that line the heart (bacterial endocarditis).
Adults with AVSD who have not had surgery to correct this heart defect may develop Eisenmenger syndrome. This is a rare disorder characterized by restricted blood flow between the lungs and the heart that occurs because of a ventricular septal defect. Symptoms of this condition may include abnormally low blood pressure, irregular heartbeats, and/or rapid heart rate. (For more information on this disorder, choose “Eisenmenger” as your search term in the Rare Disease Database.)
The exact cause of atrioventricular septal defect is not known (idiopathic). This birth defect can occur alone with no apparent cause (sporadically), or it can occur in association with other disorders such as Down syndrome.
Researchers believe that, in cases of isolated AVSD, environmental, genetic, and/or other factors (multifactorial) may be involved in some way.
Atrioventricular septal defect affects males and females in equal numbers. Approximately 50 percent of cases occur in association with other disorders, especially Down syndrome. AVSD may also occur with other congenital heart defects, in 10 percent of cases it occurs in association with patent ductus arteriosus or tetralogy of Fallot. (For more information on these disorders, choose the exact disorder name as your search term in the Rare Disease Database.)
The exact incidence of AVSD in the general population is unknown. The complete form of AVSD occurs more often than the partial or transitional forms. Approximately 75 percent of cases of complete AVSD occur in individuals with Down syndrome. Most cases of partial AVSD do not occur in individuals with Down syndrome.
The diagnosis of atrioventricular septal defect can be made by imaging techniques of the heart such as magnetic resonance imaging (MRI) and echocardiogram (EC). In another procedure known as a cardiac catheterization, a long fine tube (catheter) is inserted into a large vein and then channeled directly into the heart. This allows the physician to determine the extent of the defect (i.e., complete, transitional, or incomplete) and to determine the rate of blood flow through the heart. Angiography is another useful diagnostic procedure and allows the physician to view an enhanced x-ray of the heart. Children with AVSD typically have an abnormal EKG reading.
Infants with AVSD should be referred to a hospital that can perform sophisticated diagnostic procedures and cardiovascular surgery. Infants with AVSD generally require surgery at a young age, usually before the age of 6 to 12 months.
Prior to surgery, congestive heart failure associated with AVSD may be managed by reducing fluid volume with diuretic drugs and, if necessary, the dietary restriction of fluids and salt. The drug digoxin may also be administered to decrease the heart rate and increase the strength of the heart's contractions. Oxygen therapy and adequate nutrition may also prove beneficial.
Because children with AVSD are susceptible to bacterial infection of the membranes that surround the heart (endocarditis), any respiratory infection should be treated vigorously and early. Affected individuals should also be given antibiotics before invasive dental procedures (e.g., root canal or extractions) or other surgical procedures to help prevent potentially life-threatening infections.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government website.
For information about clinical trials being conducted at the National Institutes of Health (NIH) Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
Tollfree: (800) 411-1222
TTY: (866) 411-1010
Email: [email protected]
For information about clinical trials sponsored by private sources, contact:
Lange A, Palka P. Atrioventricular Septal Defects. In: NORD Guide to Rare Disorders. Lippincott Williams & Wilkins. Philadelphia, PA. 2003:43-4.
Cecil Textbook of Medicine, 19th Ed.: James B. Wyngaarden and Lloyd H. Smith, Jr., Editors; W.B. Saunders Co., 1992. Pp. 280-84.
The Merck Manual, 16th Ed.: Robert Berkow, Editor; Merck Research Laboratories, 1992. Pp. 2051-55.
Birth Defects Encyclopedia, Mary Louise Buyse, Editor-In-Chief; Blackwell Scientific Publications, 1990. Pp. 209-10.
Nelson Textbook of Pediatrics, 14th Ed.; Richard E. Behrman et al.; W.B. Saunders Co., 1992. Pp. 1169-70.
Dunlop KA, Mulholland HC, Casey FA, Craig B, Gladstone DJ. A ten year review of atrioventricular septal defects. Cardiol Young. 2004;14:15-23.
Pretre R, Dave H, Kadner A, Bettex D, Turina MI. Direct closure of the septum primum in atrioventricular canal defects. J Thorac Cardiovasc Surg. 2004;127:1678-81.
Maslen CL. Molecular genetics of atrioventricular septal defects. Curr Opin Cardiol. 2004;19:105-10.
Mahoney LT. Acyanotic congenital heart disease. Atrial and ventricular septal defects, atrioventricular canal, patent ductus arteriosus, pulmonic stenosis. Cardiol Clin. 1993;11:603-16.
Lozano C., et al., Surgery of atrioventricular septal defects. Review of the first 100 cases. Eur J Cardiothorac Surg. 1990;4:359-64.
Cheng TO. Cardiac failure in coronary heart disease. Am Heart J. 1990;120:396-412.
Ilbawi MN. Current status of surgery for congenital heart diseases. Clin Perinatol. 1989;16:157-76.
NORD strives to open new assistance programs as funding allows. If we don’t have a program for you now, please continue to check back with us.
NORD and MedicAlert Foundation have teamed up on a new program to provide protection to rare disease patients in emergency situations.Learn more https://rarediseases.org/patient-assistance-programs/medicalert-assistance-program/
Ensuring that patients and caregivers are armed with the tools they need to live their best lives while managing their rare condition is a vital part of NORD’s mission.Learn more https://rarediseases.org/patient-assistance-programs/rare-disease-educational-support/
This first-of-its-kind assistance program is designed for caregivers of a child or adult diagnosed with a rare disorder.Learn more https://rarediseases.org/patient-assistance-programs/caregiver-respite/
Powered by NORD, the IAMRARE Registry Platform® is driving transformative change in the study of rare disease. With input from doctors, researchers, and the US Food & Drug Administration, NORD has created IAMRARE to facilitate patient-powered natural history studies to shape rare disease research and treatments. The ultimate goal of IAMRARE is to unite patients and research communities in the improvement of care and drug development.