eMedicine Specialties > Pediatrics: Cardiac Disease and Critical Care Medicine > Cardiology
Atrial Septal Defect, Ostium Secundum
Updated: Nov 10, 2008
Introduction
Background
An ostium secundum atrial septal defect is an abnormally large opening in the atrial septum at the site of the foramen ovale and the ostium secundum.
Embryology
In the early embryo heart, the atria comprise a common chamber. As the atria enlarge, the septum primum forms and grows toward the developing atrioventricular canal area, which is later divided by the superior and inferior endocardial cushions. These cushions fuse and bend with their convexity toward the atria, thereby approaching the down-growing septum primum. This process continually narrows the passageway between the atria, which is then defined as the ostium primum.1
The ostium primum completely closes; however, before this occurs, a central perforation appears in septum primum, allowing continuous unrestricted flow from the right atrium to the left atrium. This perforation, the second opening in the septum primum, is called ostium secundum. As the atria expand to either side of the truncus arteriosus, a fold is produced within the atria just to the right of septum primum. This passively formed fold is septum secundum. The leading edge of septum secundum is concave in shape and is called the foramen ovale. It comes to overlay the ostium secundum but does not interfere with blood flow from right to left through ostium secundum. After birth, with onset of pulmonary blood flow and elevation of left atrial pressure, the septum primum is pushed against the septum secundum, effectively closing the ostium secundum.
Fusion of the septum primum and the septum secundum closes the foramen ovale. Complete closure occurs in most individuals. In 25-30% of normal adult hearts, however, a probe can be passed from the right atrium to the left atrium via the foramen ovale and ostium secundum. This patent foramen ovale allows a tiny left-to-right shunt that can be detected by sensitive techniques, such as color Doppler echocardiography, in 15-20% of adults.
Anatomy
A secundum atrial septal defect is usually bordered by the edge of the fossa ovalis and the exposed circumference of ostium secundum. The shape of the defect varies from circular to oval. Less often, strands of tissue cross the defect creating a fenestrated appearance that suggests multiple defects. Rarely, a defect can extend posteriorly and inferiorly, approaching the site of inferior vena cava entrance into the right atrium.2
Pathophysiology
A secundum atrial septal defect can result from inadequate formation of the septum secundum so that it does not completely cover the ostium secundum. More often, the ostium secundum is excessively large because of increased resorption so that septum secundum cannot cover it.
Natural history
Although heart failure from secundum atrial septal defect rarely occurs in children, this complication can often occur in adults. Adults also demonstrate a propensity for atrial dysrhythmias, including atrial flutter and fibrillation, presumably caused by chronic right atrial dilation. These complications may not be reversible if closure is delayed. Data indicate that closure in persons older than 40 years does not reduce the risk of atrial dysrhythmia. Spontaneous closure of a small secundum atrial septal defect does occur and is usually documented when the initial diagnosis is made early in infancy.3,4 A moderate atrial septal defect may also decrease significantly in size or even close when the defect is diagnosed early in life.5 However, defects diagnosed later in childhood seldom decrease in size and many significantly increase in size.6
The foramen ovale mechanism remains patent in at least 15% of adults (echocardiography can identify clinically insignificant shunts with this frequency). Some of these individuals could be classified as having a small secundum atrial septal defect. The presence of this phenomenon has been identified as a potential risk factor for stroke due to embolization into the systemic arterial circulation.
Although unusual, obstructive pulmonary vascular disease may occur in adults with an atrial septal defect.7
Frequency
International
Isolated secundum atrial septal defects account for approximately 7% of congenital cardiac defects. Congenital heart defects of significance occur in approximately 8 per 1000 live births. Therefore, 5-6 cases of secundum atrial septal defect occur per 10,000 live births. This number refers only to defects that are large enough to come to clinical attention. Many small defects that remain undetected occur in addition to numerous cases of patent foramen ovale, as mentioned above.
Mortality/Morbidity
An isolated secundum atrial septal defect very seldom causes significant symptoms in pediatric patients, regardless of defect size.
- Rarely, an infant may develop congestive heart failure in the presence of a secundum atrial septal defect. Whether the defect alone is responsible for causing heart failure is not well established, although it certainly adds to the patient's hemodynamic difficulties. Failure to thrive caused only by a secundum atrial septal defect is, similarly, a rare occurrence.
- Bacterial endocarditis is not a risk with this lesion and the American Heart Association does not advise use of antibiotic prophylaxis.
- No data indicate that an uncomplicated secundum atrial septal defect can cause pulmonary vascular disease in pediatric patients.
- A patient with primary pulmonary hypertension may demonstrate a secundum atrial septal defect, but no cause-and-effect relationship can be established.
- Patients with a significant secundum atrial septal defect who live at an altitude higher than 4000 feet may incur a small risk of developing pulmonary vascular disease.
- Death from an isolated secundum atrial septal defect does not occur in pediatric patients.
Race
No significant racial influences have been identified.
Sex
Secundum atrial septal defect occurs more commonly in females than males, with a female-to-male ratio of 2:1.
Age
Secundum atrial septal defect is a congenital abnormality and, therefore, is present at birth. It may be diagnosed at any age, including early infancy, although the characteristic findings on physical examination often escape detection until the patient reaches a few years of age. An acquired defect occurs only iatrogenically.
Clinical
History
Patients with ostium secundum atrial septal defects rarely have symptoms resulting directly from the defect. Decreased exercise tolerance in relation to peers may occur in older children and young adults. Some reports suggest that children with secundum atrial septal defects are smaller than other children; if so, this is an association. A cause-and-effect relationship has not been established.
Physical
Patients are acyanotic and may have a slender build. Respirations are normal except in the young infant, in whom mild tachypnea may occur.
The jugular venous pulse demonstrates equal a and v waves when the defect is large enough to allow equilibration of right and left atrial pressure. A right ventricular lift occurs along the lower left sternal edge, and a mild precordial bulge may be present in the same location, both caused by right ventricular dilation. A pulmonary artery systolic impulse may be felt at the upper left sternal edge. The normal left ventricular apical impulse may be absent because the left ventricle is displaced posteriorly because of the dilated anterior right ventricle. The first heart sound may be split. This is not a particularly helpful observation except that it should not be confused with the presence of a pulmonary ejection sound.
A systolic ejection murmur is found over the pulmonary trunk in the second left intercostal space. This murmur peaks in mid systole and is never more than grade 2-3/6. If a thrill is palpated in this location, the patient likely has pulmonic valve stenosis. The murmur radiates well over both lung fields. This murmur, by itself, is indistinguishable from an innocent pulmonic flow murmur. Significance of the systolic murmur depends upon identification of an abnormal second heart sound (S2) and a diastolic murmur. The S2 is widely split, and respiratory variation in the splitting interval cannot be identified.
Indeed, with a large shunt caused by a secundum atrial septal defect, the splitting interval does not vary at all with respiration; it is fixed. Wide fixed splitting of S2 typically occurs with a large atrial shunt caused by an atrial septal defect. Identifying by auscultation alone that S2 splitting is fixed, as opposed to very wide but with some respiratory variation (eg, with right bundle branch block), may be difficult. Diagnosis of an atrial septal defect by auscultation requires identification of the characteristic diastolic murmur.
A medium frequency mid diastolic murmur at the lower left sternal edge occurs with rapid ventricular filling of the right ventricle after the tricuspid valve opens. The murmur is never more than grade 1-2/6, and identifying it usually takes effort. If the shunt is large enough to cause wide, seemingly fixed, splitting of S2, this murmur should be audible.
Causes
Isolated secundum atrial septal defect occasionally demonstrates familial inheritance in an autosomal dominant pattern, particularly when associated with prolonged atrioventricular conduction (ie, prolonged PR interval on ECG). Familial secundum atrial septal defect also occurs in Holt-Oram Syndrome.
Even when not associated with an identifiable inheritance pattern, the incidence of secundum atrial septal defect is 2-3 times higher in first-degree relatives than in the general population.8 A PTPN11 gene mutation has been identified in patients with Noonan syndrome in whom heart defects occur in 85%.9 The most prevalent defects are secundum atrial septal defect and pulmonary valve stenosis; these defects were significantly associated with this gene mutation. Evidence suggests that increased folic acid intake in the general population by fortification of grain products can produce a 20% reduction in occurrence of atrial septal defects.10
More on Atrial Septal Defect, Ostium Secundum |
 Overview: Atrial Septal Defect, Ostium Secundum |
| Differential Diagnoses & Workup: Atrial Septal Defect, Ostium Secundum |
| Treatment & Medication: Atrial Septal Defect, Ostium Secundum |
| Follow-up: Atrial Septal Defect, Ostium Secundum |
| References |
| Next Page » |
References
Gessner IH. Atrial septal defect. In: Surgery of Congenital Heart Disease: Pediatric Care Consortium 1984-1995. Armonk, NY: Futura Publishing Co.; 1998:31-44.
Vick GW, Titus JL. Defects of the atrial septum, including the atrioventricular canal. In: Garson A, Bricker JT, Fisher, DJ, Neish, SR eds. The Science and Practice of Pediatric Cardiology. Vol 2. Baltimore, MD: Lippincott Williams & Wilkins; 1998.
Azhari N, Shihata MS, Al-Fatani A. Spontaneous closure of atrial septal defects within the oval fossa. Cardiol Young. Apr 2004;14(2):148-55. [Medline].
Saxena A, Divekar A, Soni NR. Natural history of secundum atrial septal defect revisited in the era of transcatheter closure. Indian Heart J. Jan-Feb 2005;57(1):35-8. [Medline].
Hanslik A, Pospisil U, Salzer-Muhar U, Greber-Platzer S, Male C. Predictors of spontaneous closure of isolated secundum atrial septal defect in children: a longitudinal study. Pediatrics. Oct 2006;118(4):1560-5. [Medline]. [Full Text].
McMahon CJ, Feltes TF, Fraley JK, et al. Natural history of growth of secundum atrial septal defects and implications for transcatheter closure. Heart. Mar 2002;87(3):256-9. [Medline].
Sachweh JS, Daebritz SH, Hermanns B, et al. Hypertensive pulmonary vascular disease in adults with secundum or sinus venosus atrial septal defect. Ann Thorac Surg. Jan 2006;81(1):207-13. [Medline].
Caputo S, Capozzi G, Russo MG, et al. Familial recurrence of congenital heart disease in patients with ostium secundum atrial septal defect. Eur Heart J. Oct 2005;26(20):2179-84. [Medline].
Sznajer Y, Keren B, Baumann C, et al. The spectrum of cardiac anomalies in Noonan syndrome as a result of mutations in the PTPN11 gene. Pediatrics. Jun 2007;119(6):e1325-31. [Medline]. [Full Text].
Godwin KA, Sibbald B, Bedard T, Kuzeljevic B, Lowry RB, Arbour L. Changes in frequencies of select congenital anomalies since the onset of folic acid fortification in a Canadian birth defect registry. Can J Public Health. Jul-Aug 2008;99(4):271-5. [Medline].
Wu ET, Akagi T, Taniguchi M, et al. Differences in right and left ventricular remodeling after transcatheter closure of atrial septal defect among adults. Catheter Cardiovasc Interv. May 1 2007;69(6):866-71. [Medline].
Walker RE, Moran AM, Gauvreau K, Colan SD. Evidence of adverse ventricular interdependence in patients with atrial septal defects. Am J Cardiol. Jun 1 2004;93(11):1374-7, A6. [Medline].
Giardini A, Donti A, Formigari R, et al. Determinants of cardiopulmonary functional improvement after transcatheter atrial septal defect closure in asymptomatic adults. J Am Coll Cardiol. May 19 2004;43(10):1886-91. [Medline].
Arrington CB, Tani LY, Minich LL, Bradley DJ. An assessment of the electrocardiogram as a screening test for large atrial septal defects in children. J Electrocardiol. Nov-Dec 2007;40(6):484-8. [Medline].
Brassard M, Fouron JC, van Doesburg NH, Mercier LA, De Guise P. Outcome of children with atrial septal defect considered too small for surgical closure. Am J Cardiol. Jun 1 1999;83(11):1552-5. [Medline].
Doll N, Walther T, Falk V, et al. Secundum ASD closure using a right lateral minithoracotomy: five-year experience in 122 patients. Ann Thorac Surg. May 2003;75(5):1527-30; discussion 1530-1. [Medline].
Argenziano M, Oz MC, Kohmoto T, et al. Totally endoscopic atrial septal defect repair with robotic assistance. Circulation. Sep 9 2003;108 Suppl 1:II191-4. [Medline]. [Full Text].
Shah D, Azhar M, Oakley CM, et al. Natural history of secundum atrial septal defect in adults after medical or surgical treatment: a historical prospective study. Br Heart J. Mar 1994;71(3):224-7; discussion 228. [Medline].
Bolz D, Lacina T, Buser P, et al. Long-term outcome after surgical closure of atrial septal defect in childhood with extensive assessment including MRI measurement of the ventricles. Pediatr Cardiol. Sep-Oct 2005;26(5):614-21. [Medline].
Lock JE, Cockerham JT, Keane JF, et al. Transcatheter umbrella closure of congenital heart defects. Circulation. Mar 1987;75(3):593-9. [Medline].
Jones TK, Latson LA, Zahn E, et al. Results of the U.S. multicenter pivotal study of the HELEX septal occluder for percutaneous closure of secundum atrial septal defects. J Am Coll Cardiol. Jun 5 2007;49(22):2215-21. [Medline].
Patel A, Lopez K, Banerjee A, Joseph A, Cao QL, Hijazi ZM. Transcatheter closure of atrial septal defects in adults > or =40 years of age: immediate and follow-up results. J Interv Cardiol. Feb 2007;20(1):82-8. [Medline].
Post MC, Suttorp MJ, Jaarsma W, Plokker HW. Comparison of outcome and complications using different types of devices for percutaneous closure of a secundum atrial septal defect in adults: a single-center experience. Catheter Cardiovasc Interv. Mar 2006;67(3):438-43. [Medline].
Handke M, Harloff A, Olschewski M, Hetzel A, Geibel A. Patent foramen ovale and cryptogenic stroke in older patients. N Engl J Med. Nov 29 2007;357(22):2262-8. [Medline].
Vida VL, Barnoya J, O'Connell M, et al. Surgical versus percutaneous occlusion of ostium secundum atrial septal defects: results and cost-effective considerations in a low-income country. J Am Coll Cardiol. Jan 17 2006;47(2):326-31. [Medline].
Butera G, Carminati M, Chessa M, et al. Percutaneous versus surgical closure of secundum atrial septal defect: comparison of early results and complications. Am Heart J. Jan 2006;151(1):228-34. [Medline].
Giardini A, Donti A, Specchia S, Formigari R, Oppido G, Picchio FM. Long-term impact of transcatheter atrial septal defect closure in adults on cardiac function and exercise capacity. Int J Cardiol. Feb 29 2008;124(2):179-82. [Medline].
Brochu MC, Baril JF, Dore A, et al. Improvement in exercise capacity in asymptomatic and mildly symptomatic adults after atrial septal defect percutaneous closure. Circulation. Oct 1 2002;106(14):1821-6. [Medline]. [Full Text].
Further Reading
Keywords
ostium secundum atrial septal defect, ASD, fossa ovalis defect, secundum atrial septal defect, atrial dysrhythmia, right heart dysfunction, patent foramen ovale, chronic right atrial dilation, heart failure, atrial fibrillation, atrial flutter, atrial dysrhythmia, stroke, obstructive pulmonary vascular disease, failure to thrive, bacterial endocarditis, primary pulmonary hypertension, pulmonary valve stenosis, Holt-Oram syndrome
