$Unique_ID{BRK03506} $Pretitle{} $Title{Atrial Septal Defects} $Subject{Atrial Septal Defects Atrioseptal Defects Ostium Primum Defect endocardial cushion defects Ostium Secundum Defect Sinus Venosus} $Volume{} $Log{} Copyright (C) 1986 National Organization for Rare Disorders, Inc. 138: Atrial Septal Defects ** IMPORTANT ** It is possible that the main title of the article (Atrial Septal Defects) is not the name you expected. Please check the SYNONYM listing to find the alternate names and disorder subdivisions covered by this article. Synonyms Atrioseptal Defects DISORDER SUBDIVISION: Ostium Primum Defect; such defects belong to the "endocardial cushion" defects, and may sometimes be known as such Ostium Secundum Defect Sinus Venosus General Discussion ** REMINDER ** The information contained in the Rare Disease Database is provided for educational purposes only. It should not be used for diagnostic or treatment purposes. If you wish to obtain more information about this disorder, please contact your personal physician and/or the agencies listed in the "Resources" section. Atrial septal defects are a relatively common form of congenital heart disease. The septum separating the two atria is incompletely formed before birth and the opening persists. This can result in inefficient distribution of oxygen to the various tissues of the body, heart failure characterized by edema, difficulty breathing, fatigue, and other cardiovascular disturbances. Symptoms tend to be mild at first, so that the defect is sometimes not recognized until adulthood, when various cardiorespiratory problems and heart failure begin to develop. Atrial defects can take several forms, with different clinical consequences. Many symptoms are shared by several different kinds of congenital heart defects. To determine the exact anatomic abnormality, physicians rely on the patterns and quality of the sounds of the beating heart, electrocardiographic (EKG) and echocardiographic findings, and information from cardiac catheterization. The heart sounds and EKG are the most commonly performed investigations and may be characteristic. Symptoms A short discussion of the structure and function of the normal heart follows. The human heart has four chambers, two atria and two ventricles. Deoxygenated blood enters the right atrium from the systemic veins (i.e., the veins draining all the body organs and tissues except the lungs). It is pumped from the right atrium to the right ventricle, and from the right ventricle to the pulmonary artery. The pulmonary artery carries the blood to the lungs, where it is saturated with oxygen. From the lungs, the blood passes through the pulmonary veins to the left atrium, and thence into the left ventricle, the most muscular of the four chambers of the heart. The contraction of the left ventricle forces the blood back into the systemic circulation, where it supplies oxygen to the various body tissues. Blood then collects in veins, which eventually come together and drain again into the right atrium. The two atria are separated from each other by a relatively thin membrane, known as the atrial septum. The ventricular septum separates the right and the left ventricles. In atrial septal defects, this thin membrane separating the atria is incomplete. In ostium primum defects, the membrane at the lower part of the septum has failed to develop normally; often the valves separating the atrium from the ventricle on each side [tricuspid (right side) and bicuspid or mitral (left side) valves] are also malformed, and even the apex of the ventricular septum may be missing. Ostium primum defects are often associated with Down's Syndrome and are a relatively severe form of septal defect. The most common atrial septal defect is known as the ostium secundum defect. Here, the middle part of the atrial septum (region of foramen ovale) fails to close during development of the fetus. This condition superficially appears similar to what is known as patent foramen ovale, but develops differently, and has a different course. (The foramen ovale is a hole in the atrial septum covered by a flap of tissue; it allows blood to flow in one direction between the two atria during the fetal stage, when the circulation bypasses the lungs. Normally, it closes shortly after birth, but in some cases it remains anatomically, though not functionally, open.) A third form of atrial septal defect, known as sinus venosus, occurs high in the septum and is often associated with anomalous entry of the pulmonary veins or vena cava (from the systemic circulation) in to the right and left atria respectively. Septal defects allow deoxygenated blood from the right atrium to mix with freshly oxygenated blood from the left atrium. This decreases the overall oxygen saturation of the blood that is pumped into the systemic circulation. Many children with atrial septal defects do not have symptoms. Some have mild growth retardation, and there seems to be an unusual susceptibility to respiratory infections. However, by about 40 years of age, or even earlier at high altitudes where there is more stress on the cardiorespiratory system, patients may begin to have difficulties. This is because hypertension (high blood pressure) gradually develops in the pulmonary circulation, changing the direction in which the blood is shunted through the opening in the atrial septum. Right to left shunts have several clinical consequences, including cyanosis (bluish complexion) due to poor oxygen saturation of the blood and tissues, clubbing of the finger tips, and polycythemia, or an increase in the number of red blood cells. This condition also predisposes its victims to brain abscesses. In severe cases, the tissues may receive less than adequate amounts of oxygen. Eventually, there may be heart failure, with edema and breathlessness. Death may result without surgical repair of this defect. Another later manifestation of atrial septal defects is disturbance of the rhythm of atrial contractions (arrhythmias, including atrial fibrillation). Heart defects seem to predispose the patient to bacterial infection of the inner lining of the heart (bacterial endocarditis). The resulting damage can aggregate the patient's condition. Causes The causes of the arrest in embryonic development resulting in congenital heart disease are poorly understood. Only about 10% of the cases appear to be hereditary. Maternal rubella (measles), alcoholism, or diabetes are associated with heart defects. Ostium primum defects often occur in individuals with Down's syndrome, and certain other chromosomal abnormalities. Affected Population About one percent of live births have some kind of congenital heart defect; of these, about ten percent have atrial septal defects. Males are affected more often than females. Related Disorders Other congenital heart defects include ventricular septal defects, valve defects of various kinds, malformations of the large vessels entering and leaving the heart, and anomalous positions of the heart in the chest. Therapies: Standard The definitive treatment for atrial septal defects is surgical. The hole in the septum is either sutured shut, or patched with a graft. The success rate is quite high. In ostim primum (endocardial cushion) defects, the atrioventricular valves may have to be repaired or replaced; the success rate is substantially lower in these more complex operations. Surgery is usually most successful in patients between the ages of 3 and 6 years. Presurgical, palliative, treatment includes medication such as digitalis to treat arrhythmias, excessively rapid heart beat, and heart failure. Sodium restriction, diuretics, and rest are also effective in treating congestive heart failure. Respiratory infections are treated vigorously, and antibiotics are given prophylactically with such procedures as tooth extractions to reduce the risk of developing bacterial endocarditis. Therapies: Investigational This disease entry is based upon medical information available through March 1987. Since NORD's resources are limited, it is not possible to keep every entry in the Rare Disease Database completely current and accurate. Please check with the agencies listed in the Resources section for the most current information about this disorder. Resources For more information on Atrial Septal Defects, please contact: National Organization for Rare Disorders (NORD) P.O. Box 8923 New Fairfield, CT 06812-1783 (203) 746-6518 American Heart Association 7320 Greenville Ave. Dallas, TX 75231 (214) 750-5300 NIH/National Heart, Lung and Blood Institute 9000 Rockville Pike Bethesda, MD 20892 (301) 421-8453 American Lung Association 1740 Broadway New York, NY 10019 (212) 315-8700 References Petersdorf, Robert G., et al, editors, Harrison's Principles of Internal Medicine, tenth edition. New York: McGraw-Hill 1983, pp. 1383-96.