Atrial septal defect overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editors-In-Chief: Priyamvada Singh, MBBS [[2]]; Cafer Zorkun, M.D., Ph.D. [3]; Assistant Editor-In-Chief: Kristin Feeney, B.S. [[4]]
Overview
Atrial septal defects (ASD) refer to a group of congenital heart diseases that involve the inter-atrial septum. The inter-atrial septum is the tissue that separates the right and left atria from each other. This tissue prevents arterial and venous blood from mixing with each other. If there is a defect in this septum, a direct communication between the atria can occur, which allows shunting, resulting in mixing of arterial and venous blood. It is possible for blood to travel from the left side of the heart to the right side of the heart, or vice versa.
Epidemiology and demographics
Atrial septal defect are common heart defects and comprises approximately 7% of all the congenital heart disorders. [1]. Unlike other conditions ASD has a slight female preponderance of 2:1.
Natural History, Complications and Prognosis
The natural history of atrial septal defect depends on the location, size, amount of shunting of blood and the associated anomalies seen. A small atrial septal defect may remain asymptomatic throughout the life and closes spontaneously in infants. Patients with atrial septal defects are able to survive to adulthood. It can also present in adulthood with insidious development of symptoms. Complications like pulmonary hypertension, atrial fibrillation, right heart failure and stroke can occur if large sized defects are left uncorrected. The mortality rate for surgical intervention repair is less than 1% for atrial septal defect patients under the age of 45, with no history failure or pulmonary artery pressure issues.
Causes
Like other congenital heart defects the cause behind ASDs are still not clear. Secundum defects are the commonest type of atrial septal defect. Many a times they occur sporadically. However, they have been found to occur with increased incidences in some genetic disorders like, the Holt-Oram (heart-hand) syndrome, Down’s syndrome, Noonan syndrome,Treacher Collins syndrome, and the thrombocytopenia-absent radii (TAR) syndrome.
Diagnosis
History and physical examination
Atrial septal defect patients may present with features that occurs due to left-to-right shunting of blood. Symptoms like difficulty in breathing, exercise intolerance, fatigue may be seen. Volume overload on the right side of heart can lead to right heart failure that may present with symptoms of swelling of extremities, difficulty breathing and signs like hepatomegaly and raised jugular venous pulse. On cardiovascular examinations there is a fixed splitting of second heart sound. Also, an ejection systolic murmur that is attributed to the increased flow of blood through the pulmonic valve can be heard.
Electrocardiogram
The ECG findings may show a prolonged PR interval (a first degree heart block). The prolongation of the PR interval is probably due to the enlargement of the atria that is common in ASD. Other findings like right bundle branch block (RBBB), right axis deviation, right ventricular hypertrophy (RVH) atrial fibrillation or atrial flutter
Echocardiography
Echocardiography along with doppler ultrasound are the preferred imaging modalities to diagnose atrial septal defect. In transthoracic echocardiography, an atrial septal defect may be seen on color flow imaging as a jet of blood from the left atrium to the right atrium.
Treatment
Atrial septal defects can stay asymptomatic until fourth decade of life. Treatment approach for the patients could be either medical or surgical. Surgical closure further could be divided into per-cutaneous repair or open heart surgery involving either suture or patch closure. Medical therapy has very limited role in the definitive treatment of the lesion. Medical therapy is often used to manage arrhythmia and some comorbidity complexes associated with atrial septal defect such as stroke and migraine. Percutaneous closure is commonly done for ostium secundum atrial septal defects. It is still not FDA approved for other types of atrial septal defects like primum, sinus venosus. With proper patient's selection it has been found to be as successful, safe and effective as surgical closure. Additionally, it was associated with fewer complications and decreased average hospital stay compared to surgical care.
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