1. Dr. Jawad Alzamil Demonstrator KFCC,KKUH
Atrial Septal Defect
Dr. Jawad Alzamil Demonstrator KFCC,KKUH

2. Outlines: Defenition. Embryology Anatomy. Physiology. Pathophysiology.
Types.
Clinical features.
Diagnosis.
Treatment.
Follow up.

3. Defenition:
Congenital cardiac anomaly characterized by a defect in the interatrial septum –other than PFO- allowing pulmonary venous return from the left atrium to pass directly to the right atrium.

4. Is it an ASD???
NO, it is a PFO!!!

5. Embryology:

6. Cont.
During the first 23 days of the embryo’s life, the atrial chamber is a common one and connected to the sinus venosus to drain the blood coming from right and left vens horns. After completion of cardiac looping by the third week, atrial septation begins by developing the septum primum partly from the endocardial cushion tissue. It is important to note that there is always atrial communication between the left and right sides throughout all developmental stages to maintain adequate right to left shunt and oxygenate the developing brain tissue.

7. Cont.
Even before the completion of the septum primum, fenestrations start to take place in this septum to allow blood to flow freely though it. By the early fifth week of fetal life, the septum secondum starts to appear from the superior- posterior aspect of the mid-atrial wall and extends inferiorly and anteriorly, leaving a flap of the septum primum in the mid-portion to be uncovered. This flap is pushed by the blood flow coming from the umbilical vein and remains open till the end of pregnancy

8. Frequency:
Atrial septal defect (ASD) account for 10% of all congenital heart disease and as much as 20-40% of congenital heart disease presenting in adulthood.
Sex: ASD occurs with a female-to-male ratio of 2:1
Age: Patients with ASD can be asymptomatic through infancy and childhood, though it depends on the degree of left-to-right shunt. Symptoms become more common with advancing age. By the age of 40 years, 90% of untreated patients have symptoms of exertional dyspnea, fatigue, palpitation, arrhythmia, or heart failure

9. ASD SECUNDUM 75%: A large foramen ovale occur as a result of defective development of the septum secundum, a combination of excessive resorption of the septum primum and a large foramen ovale produces a large ostium secundum ASD
Types:
Coronary sinus ASD: Coronary sinus defect is characterized by unroofed coronary sinus and persistent left superior vena cava that drains into the left atrium. A dilated coronary sinus often suggests this defect. This can result is desaturation due to right-to-left shunt into the left atrium. The diagnosis can be made by injecting contrast agent into left upper extremity; coronary sinus opacification precedes right atrial opacification
Ostium primum ASD 15-20%: caused by incomplete fusion of septum primum with the endocardial cushion. The defect lies adjacent to the atrioventricular (AV) valves, either of which may be deformed and incompetent. In most cases, only the anterior or septal leaflet of the mitral valve is displaced, and it is commonly cleft. The.tricuspid valve is usually not involved.
Sinus venosus ASD 5-10%: Abnormal fusion between the embryologic sinus venosus and the atrium causes these defects. In most cases, the defect lies superior in the atrial septum near the entry of superior vena cava. Often there is associated anomalous drainage of the right superior pulmonary vein. The relatively uncommon inferior type is associated with partial anomalous drainage of the right inferior pulmonary vein into the right atrium, the superior vena cava, or the inferior vena cava.

10. Cont.

12. So the classification according to their location relative to the fossa ovalis.

13. Genetics:
Holt-Oram syndrome characterized by an autosomal dominant pattern of inheritance and deformities of the upper limbs. The penetrance is nearly 100%.
syndrome familial ASD !! :Mutations in the cardiac transcription factor NKX2.5 have been attributed to the syndrome. Is it like simple ASD?
No, it is associated later in life with progressive AV block.
Smits JP, Veldkamp MW, Wilde AM (2005) Mechanisms of inherited cardiac conduction disease. Europace 7:

14. Pathophysiology:
The magnitude of the left-to-right shunt across the ASD depends : the defect size, the relative compliance of the ventricles, and the relative resistance in both the pulmonary and systemic circulation. With small ASD, left atrial pressure may exceed right atrial pressure by several millimeters of mercury, whereas with large ASD, mean atrial pressures are nearly identical. Shunting across the interatrial septum is usually left-to-right and occurs predominantly in late ventricular systole and early diastole. Likely some augmentation occurs during atrial contraction. Note, however, that a transient and small right-to-left shunt can occur, especially during respiratory periods of decreasing intrathoracic pressure, even in the absence of pulmonary arterial hypertension.

15. Cont.
The chronic left-to-right shunt results in increased pulmonary blood flow and diastolic overload of the right ventricle. Resistance in the pulmonary vascular bed is commonly normal in children with ASD, and the volume load is usually well tolerated even though pulmonary blood flow may be more than 2 times systemic blood flow. Altered ventricular compliance with age can result in an increased left-to-right shunt contributing to symptoms. The chronic significant left-to-right shunt can alter the pulmonary vascular resistance leading to pulmonary arterial hypertension, even reversal of shunt and Eisenmenger syndrome.

16. Cont.
Because of an increase in plasma volume during pregnancy, shunt volume can increase, leading to symptoms. Pulmonary artery pressure usually remains normal.

17. Effect on the heart: http://www.youtube.com/watch?v=e46jtin-H50
This extra blood from the left atrium may cause a volume overload of both the right atrium and the right ventricle, which if left untreated, can result in enlargement of the right side of the heart (in case of Large ASD)
The right ventricle will have to push out more blood than the left ventricle due to the left-to-right shunt. This constant overload of the right side of the heart will cause an overload of the entire pulmonary vasculature. Eventually the pulmonary vasculature will develop pulmonary hypertension to try to divert the extra blood volume away from the lungs.

18. Cont
The pulmonary hypertension will cause the right ventricle to face increased afterload in addition to the increased preload that the shunted blood from the left atrium to the right atrium caused. The right ventricle will be forced to generate higher pressures to try to overcome the pulmonary hypertension. This may lead to right ventricular failure (dilatation and decreased systolic function of the right ventricle) or elevations of the right sided pressures to levels greater than the left sided pressures.
When the pressure in the right atrium rises to the level in the left atrium, there will no longer be a pressure gradient between these heart chambers, and the left-to-right shunt will diminish or cease.

19. Cont.
If left uncorrected, the pressure in the right side of the heart will be greater than the left side of the heart. This will cause the pressure in the right atrium to be higher than the pressure in the left atrium. This will reverse the pressure gradient across the ASD, and the shunt will reverse; a right-to-left shunt will exist. This phenomenon is known as Eisenmenger's syndrome.
Once right-to-left shunting occurs, a portion of the oxygen-poor blood will get shunted to the left side of the heart and ejected to the peripheral vascular system. This will cause signs of cyanosis.

20. Cont. So we can say on the Heart:
Dilatation of right atrium and Ventricle.So what about the risk of Mural thrombus?
uncommon
Dilated and mildly thickened incompetent tricuspid and pulmonary valves.
Dilatation of MPA.
Mildly dilated left atrium.How about left ventricle?
Normal if isolated ASD

21. Cont. On the Lung: (with chronic volume overload):
Dilatation of pulmonary vascular bed.
Severe and irreversible hypertensive pulmonary vascular disease develop ( in few patient with striking female predominance).
Mainly in adults: chronic pulmonary venous hypertension LVH LVF or chronic hypoxic pulmonary hypertension chronic obstructive or interstitial pulmonary disease