Atrial septal defect

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Atrial septal defect
Classification and external resources
Illustration of an atrial septal defect.
ICD-10 Q21.1
ICD-9 745.5-745.6
OMIM 108800
DiseasesDB 1089
MedlinePlus 000157
eMedicine med/3519 article/894813
MeSH C14.240.400.560.375

Atrial septal defect (ASD) is a form of a congenital heart defect that enables blood flow between two compartments of the heart called the left and right atria. Normally, the right and left atria are separated by a septum called the interatrial septum. If this septum is defective or absent, then oxygen-rich blood can flow directly from the left side of the heart to mix with the oxygen-poor blood in the right side of the heart, or vice versa.[1] This can lead to lower-than-normal oxygen levels in the arterial blood that supplies the brain, organs, and tissues. However, an ASD may not produce noticeable signs or symptoms, especially if the defect is small.

A "shunt" is the presence of a net flow of blood through the defect, either from left to right or right to left. The amount of shunting present, if any, determines the hemodynamic significance of the ASD (see Pathophysiology below). A "right-to-left-shunt" typically poses the more dangerous scenario. (see Pathophysiology below.)

During development of the fetus, the interatrial septum develops to separate the left and right atria. However, a hole in the septum called the foramen ovale /fɒˈrmən ˈvɑːl/, allows blood from the right atrium to enter the left atrium during fetal development. This opening allows blood to bypass the nonfunctional fetal lungs while the fetus obtains its oxygen from the placenta. A layer of tissue called the septum primum acts as a valve over the foramen ovale during fetal development. After birth, the pressure in the right side of the heart drops as the lungs open and begin working, causing the foramen ovale to close entirely. In approximately 25% of adults,[2] the foramen ovale does not entirely seal.[3] In these cases, any elevation of the pressure in the pulmonary circulatory system (due to pulmonary hypertension, temporarily while coughing, etc.) can cause the foramen ovale to remain open. This is known as a patent foramen ovale (PFO), which is a type of atrial septal defect.


In unaffected individuals, the chambers of the left side of the heart are under higher pressure than the chambers of the right side of the heart. This is because the left ventricle has to produce enough pressure to pump blood throughout the entire body, while the right ventricle needs only to produce enough pressure to pump blood to the lungs.

In the case of a large ASD (>9mm), which may result in a clinically remarkable left-to-right shunt, blood will shunt from the left atrium to the right atrium. This extra blood from the left atrium may cause a volume overload of both the right atrium and the right ventricle. If untreated, this condition can result in enlargement of the right side of the heart and ultimately heart failure.[4]





As a group, atrial septal defects are detected in 1 child per 1500 live births. PFO are quite common (appearing in 10–20% of adults) but asymptomatic and therefore undiagnosed. ASDs make up 30 to 40% of all congenital heart diseases that are seen in adults.[5]

The ostium secundum atrial septal defect accounts for 7% of all congenital heart lesions. This lesion shows a female preponderance, with a male:female ratio of 1:2.[6]

Genetic research[edit]

In May 2013 team of researchers led by Professor Bernard Keavney of British Heart Foundation (BHF) discovered a new gene associated with the disease. According to them a common genetic variation near a gene called MSX1 is strongly associated with the risk of an ASD and this discovery of the particular gene is an important step forward as it will lead to better understanding of why some patients are born with ASD.[7]

Types of atrial septal defects[edit]

Schematic drawing showing the location of different types of ASD, the view is into an opened right atrium. HV: right ventricle; VCS: superior vena cava; VCI: inferior vena cava; 1: upper sinus venosus defect; 2: lower sinus venosus defect; 3: secundum defect; 4: defect involving coronary sinus; 5; primum defect.


Ostium secundum atrial septal defect[edit]



If the ostium secundum ASD is accompanied by an acquired mitral valve stenosis, that is called Lutembacher's syndrome.[9]\DR ABO EL ASRAR AT M.D

Natural history[edit]



While pulmonary hypertension is unusual before 20 years of age, it is seen in 50 percent of individuals above the age of 40. Progression to Eisenmenger's syndrome occurs in 5 to 10 percent of individuals late in the disease process.[9]

Patent foramen ovale[edit]

A patent foramen ovale (PFO) is a small channel that has some hemodynamic consequence; it is a remnant of the fetal foramen ovale. Clinically it is linked to decompression sickness, paradoxical embolism and migraine. On echocardiography, there may not be any shunting of blood noted except when the patient coughs.

There is debate within the neurology and cardiology communities about the role of a PFO in cryptogenic (i.e. of unknown cause) neurologic events such as strokes and transient ischemia attacks (TIAs) without any other potential cause. Some data suggested that PFOs may be involved in the pathogenesis of some migraine headaches.[citation needed][dubious ] Several clinical trials are currently underway to investigate the role of PFO in these clinical situations.[citation needed]

Ostium primum atrial septal defect[edit]

A defect in the ostium primum is occasionally classified as an atrial septal defect,[10] but it is more commonly classified as an atrioventricular septal defect.[11][12] Ostium primum defects are less common than ostium secundum defects.[13]

Sinus venosus atrial septal defect[edit]




Common or single atrium[edit]


Mixed atrial septal defect[edit]



Abnormal chest X-ray as seen in a patient of Atrial septal defect

Diagnosis in children[edit]


Diagnosis in adults[edit]



Physical exam auscultation of the heart[edit]












Transcranial Doppler (TCD) bubble study[edit]

A less invasive method for detecting a PFO or other ASDs than transesophagal ultrasound is Transcranial Doppler with bubble contrast.[17] This method reveals the cerebral impact of the ASD or PFO.











Evaluation prior to correction[edit]




Catheter procedure[edit]

Until the early 1990s, surgery was the usual method for closing all ASDs. Now, thanks to medical advances, doctors can use catheter procedures to close secundum ASDs, the most common type of ASD. For this procedure, the patient is given medicine so he or she will sleep through it and not feel any pain. During the procedure, the doctor inserts a catheter (a thin, flexible tube) into a vein in the groin (upper thigh) and threads it to the heart's septum. The catheter has a tiny umbrella-like device folded up inside it. When the catheter reaches the septum, the device is pushed out of the catheter and positioned so that it plugs the hole between the atria. The device is secured in place and the catheter is withdrawn from the body. Within 6 months, normal tissue grows in and over the device. There is no need to replace the closure device throughout the patient's life. Doctors often use echocardiography (echo) or transesophageal echo (TEE) as well as angiography to guide them in threading the catheter to the heart and closing the defect. TEE is a special type of echo that takes pictures of the heart through the esophagus (the passage leading from the mouth to the stomach). Catheter procedures are much easier on patients than surgery because they involve only a needle puncture in the skin where the catheter is inserted. This means that recovery is faster and easier. The outlook for patients having this procedure is excellent. Closures are successful in more than 9 out of 10 patients, with no significant leakage. Rarely, a defect is too large for catheter closure and surgery is needed.

Surgical ASD closure[edit]

Illustration depicting surgical patch closure of ASD


Percutaneous ASD closure[edit]

Percutaneous closure of an ASD is currently only indicated for the closure of secundum ASDs with a sufficient rim of tissue around the septal defect so that the closure device does not impinge upon the SVC, IVC, or the tricuspid or mitral valves. The Amplatzer Septal Occluder (ASO) is commonly used to close ASDs. The ASO consists of two self-expandable round discs connected to each other with a 4 mm waist, made up of 0.004–0.005´´ Nitinol wire mesh filled with Dacron fabric. Implantation of the device is relatively easy. The prevalence of residual defect is low. The disadvantages are a thick profile of the device and concern related to a large amount of nitinol (a nickel-titanium compound) in the device and consequent potential for nickel toxicity.

Percutaneous closure is the method of choice in most centres.[19]



Decompression sickness[edit]


Eisenmenger's syndrome[edit]


Paradoxical embolus[edit]





Associated conditions[edit]

See also[edit]


  1. ^ Atrial septal defect at Mount Sinai Hospital
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  9. ^ a b c Goldman 2011, pp. 400–401
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  11. ^ Fix, James D.; Dudek, Ronald W. (1998). Embryology. Baltimore: Williams & Wilkins. p. 52. ISBN 0-683-30272-8. 
  12. ^ Q21.2
  13. ^ a b Skelley, Tao Le, Vikas Bhushan, Nathan William. First aid for the USMLE step 2 CK (8th ed. ed.). New York: McGraw-Hill Medical. p. 357. ISBN 978-0-07-176137-6. 
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  15. ^ Valdes-Cruz, L. M., Cayre, R. O. (1998). Echocardiographic diagnosis of congenital heart disease. Philadelphia. 
  16. ^ Goldman 2011, pp. 270
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  18. ^ Clark E, Kugler J (1982). "Preoperative secundum atrial septal defect with coexisting sinus node and atrioventricular node dysfunction". Circulation 65 (5): 976–80. doi:10.1161/01.CIR.65.5.976. PMID 7074763. 
  19. ^ Bjørnstad P (2006). "Is interventional closure the current treatment of choice for selected patients with deficient atrial septation?". Cardiol Young 16 (1): 3–10. doi:10.1017/S1047951105002027. PMID 16454871. 
  20. ^ Lier H, Schroeder S, Hering R (2004). "Patent foramen ovale: an underrated risk for divers?". Dtsch Med Wochenschr 129 (1–2): 27–30. doi:10.1055/s-2004-812652. PMID 14703578. 
  21. ^ Saary M, Gray G (2001). "A review of the relationship between patent foramen ovale and type II decompression sickness". Aviat Space Environ Med 72 (12): 1113–20. PMID 11763113. 
  22. ^ Adams H (2004). "Patent foramen ovale: paradoxical embolism and paradoxical data". Mayo Clin Proc 79 (1): 15–20. doi:10.4065/79.1.15. PMID 14708944. 
  23. ^ Azarbal B, Tobis J, Suh W, Chan V, Dao C, Gaster R (2005). "Association of interatrial shunts and migraine headaches: impact of transcatheter closure". J Am Coll Cardiol 45 (4): 489–92. doi:10.1016/j.jacc.2004.09.075. PMID 15708691. 
  24. ^ Dowson, Andrew; Mullen, MJ; Peatfield, R; Muir, K; Khan, AA; Wells, C; Lipscombe, SL; Rees, T; De Giovanni, JV; Morrison, WL; Hildick-Smith, D; Elrington, G; Hillis, WS; Malik, IS; Rickards, A (18 March 2008). "Migraine Intervention With STARFlex Technology (MIST) trial: a prospective, multicenter, double-blind, sham-controlled trial to evaluate the effectiveness of patent foramen ovale closure with STARFlex septal repair implant to resolve refractory migraine headache.". Circulation 117 (11): 1397–404. doi:10.1161/CIRCULATIONAHA.107.727271. PMID 18316488. 
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 This article incorporates public domain material from the United States Department of Health and Human Services document "National Heart, Lung, and Blood Institute".

Additional references[edit]

  • Goldman, Lee (2011). Goldman's Cecil Medicine (24th ed ed.). Philadelphia: Elsevier Saunders. pp. 270, 400–401. ISBN 1437727883. 

External links[edit]