Atrial septal defect

Last revised by Rohit Sharma on 25 May 2022

Atrial septal defect (ASD) is the second most common congenital heart defect after ventricular septal defects (VSDs) and the most common to become symptomatic in adulthood.

They are characterized by an abnormal opening in the atrial septum allowing communication between the right and left atria. Due to the low pressures of the atria, the lesion is typically asymptomatic until adulthood despite 2-4 times the normal pulmonary blood flow. Gradual (high output) congestive cardiac failure may eventually develop, becoming symptomatic by the age of 30 years.

Atrial septal defects account for ~10% of congenital heart disease 7. There may be greater female predilection.

Atrial septal defects are seen in association with the following:

Most patients are asymptomatic but as cardiac failure develops they may present with shortness of breath, palpitations, and weakness 7. Chest auscultation classically reveals an ejection systolic murmur heard at the left upper sternal border, attributed to increased flow across the pulmonary valve rather than blood shunting across the defect itself 7

There are characteristic ECG findings in patients with an atrial septal defect.

  • incomplete right bundle branch block (RBBB morphology with QRS duration between 110-120 ms) 
    • increased specificity with crochetage sign in the inferior (II, III, aVF) leads
  • right precordial (V1-3) "defective T waves"
    • describes biphasic morphology, initial T wave flattening or inversion and sharp, positive upstroke to terminal positive deflection 9
    • peak of the T wave delayed when compared to lateral precordial leads
  • notching of the terminal upstroke of the R wave (crochetage sign) correlates with the size of ASD and implies a greater degree of shunting 10
  • left axis deviation
    • characteristic of ostium primum defects and anatomical distortion of the left bundle branch fascicles
    • associated first degree AV block
  • right axis deviation
    • suggests ostium secundum defect
  • low atrial ectopic rhythms
    • negative P wave polarity in lead II
    • found in sinus venosus ASDs

An understanding of complex cardiac development is important in understanding the numerous possible abnormalities that can arise. There are four major types of atrial septal defect (ASD) 4, distinguished according to their location within the septum:

A patent foramen ovale (PFO) is a form of atrial septal defect.

Atrial septal defects do not cause any impairment in cardiac function in utero and even most neonates are asymptomatic. The defect can be closed surgically or percutaneously (e.g. atrial septal occlusion device). However, careful evaluation has to be made to ensure lack of development of elevated right heart pressures or a right to left shunt before any intervention.  

In approximately 10% of untreated patients, pulmonary hypertension develops. In this situation, flow through the shunt eventually reverses and becomes right-to-left leading to cyanosis, known as Eisenmenger syndrome.

Other complications include:

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Cases and figures

  • Figure 1: illustration
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  • Case 1
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  • Case 2
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  • Case 3
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  • Case 4: with closure device
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  • Case 5: with closure device
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  • Case 6
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  • Case 7: secundum ASD
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  • Case 8
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  •  Case 9
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  • Case 10
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  • Case 11
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  • Case 12: secundum ASD
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  • Case 13: with pulmonary hypertension
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  • Case 14
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  • Case 15: sinus venosus ASD + PAPVR
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  • Case 16: ostium primum (fetal echocardiography)
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  • Case 17
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  • Case 18: with total anomalous pulmonary venous return
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  • Case 19: ASD upper sinus venosus type with PAPVR into SVC
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  • Case 20
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  • Case 21
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