1. Kendra Marsh, MD Division of Cardiology, UIC Fellow
Atrial Septal Defect
Kendra Marsh, MD
Division of Cardiology, UIC
Fellow

2. Embryology Gestational Week 4 Gestational Week 4-6 •
A thin, crescent shaped wedge of tissue of (septum primum) grows towards and fuses with endocardial cushions.
The remaining opening is called the ostuim primum. •
As the septum primum is growing down, the endocardial cushions fuse and the ostium primum is eventually obliterated.

3. Embryology
The interatrial septum forms during the first and second months of fetal development.
Stage I is the formation of the septum primum.
The septum primum walls off a crescent-shaped portion of the hole between the right and left atria.
Foramen primum (also called the ostium primum) stays open
The remaining part of the opening between the right and left atria is closed by the septum secundum.
The 2 tissue layers overlap like a flap, allowing blood flow to continue during fetal life.
Changes in circulation at birth, closes the flap permanently.

4. Anatomy and Physiology
Extends from cavo-atrial junction with superior and inferior vena cavae
Ends near the atrio-ventricular canal near the tricuspid valve

5. Ostium Secundum Most common type of ASD
Center of the septum between the right and left atrium
Variant of this type of ASD is called a Patent Foramen Ovale (PFO) which is very small.

6. Ostium Primum Next most common type
Located in the lower portion of the atrial septum.
Will often have a mitral valve defect associated with it called a mitral valve cleft.
A mitral valve cleft is a slit-like or elongated hole usually involves the anterior leaflet of the mitral valve.

7. Sinus Venosus Least common type of ASD
Located in the upper portion of the atrial septum.
Association with an abnormal pulmonary vein connection
Four pulmonary veins, two from the right lung and two from the left lung, normally return red blood to the left atrium.
Usually with a sinus venosus ASD, a pulmonary vein from the right lung will be abnormally connected to the right atrium instead of the left atrium.
This is called an anomalous pulmonary vein.
..\asd-veno.jpg

8. Foramen Ovale Remnant of fetal circulation Behaves like flap valve
Opens during increased intra-thoracic pressure

9. Incidence and Prevalence
one of the most common congenital heart defects seen in pediatric cardiology
7-10% of all patients with congenital heart disease
Twice as frequent in females than males

10. Presentation Fatigue Shortness of Breath Growth retardation
Frequent respiratory infections
Persistent murmur

11. Diagnostics ECG X-RAY ECHOCARDIOGRAPHY
Sometimes cardiac catheterization

12. Shunt Determination Normally… Shunt Suspected If… Types of Shunts
Pulmonary Blood Flow = Systemic Blood Flow
Shunt Suspected If…
Pulmonary Artery Saturation >80% (?Left-Right)
Unexplained Arterial Saturation less than 93%
(Right to Left)
may also see in Pulmonary Edema, Pulmonary Disease, over sedation and cardiogenic shock
Types of Shunts
Systemic Circulation to Pulmonary Circulation
Left to right
Pulmonary Circulation to Systemic Circulation
Right to Left

13. Invasive Methods to Diagnose Shunting
Oximetric Method
Indicator Dilution Method

14. Principles of the Oxymetric Method
Blood Sampling from various chambers to determine Oxygen Saturation
Left to Right Shunt is present when a significant increase in blood oxygen saturation is found between 2 right sided vessels or chambers

15. Oximetric Method
“Shunt Run” is performed if a difference of 8% or more is noted in blood sampling between chambers
Blood samples taken from all right sided locations: IVC, SVC, Right Atrium, Right Ventricle and Pulmonary Artery
In case of Inter-atrial shunt multiple samples should be collected from the High, middle and low right atrium

16. Saturation Run Obtain Samples from…
IVC: High and Low
SVC: High and Low
Right Atrium: High, Middle and Low
Right Ventricle: Inflow and Outflow tracts, mid-cavity
Pulmonary Artery: Main, Left or Right
Localizing Right to Left Shunts one should also obtain….
Pulmonary Vein
Left Atrium
Left Ventricle
Distal Aorta

17. Fick Equation to Calculate Oxygen Content
Assumes in steady state that…
that rate of substance entering (C in x Qflow) is equal to the rate of substance leaving
(C out x Qflow) + the rate at which indicator, V, is added.
Flow= Oxygen consumption/Arterial-Venous oxygen content difference
Where oxygen content is determined by automated methods
oxygen consumption is assumed based on patient’s age, gender and body surface area when not directly measured

18. Shunt Quantification Pulmonary Blood Flow Systemic Blood Flow
Oxygen consumption
_________________________________________
Difference in oxygen content across pulmonary bed
(PvO2-PaO2)
Systemic Blood Flow
Oxygen Consumption
Difference in oxygen content across systemic bed
(SaO2- MvO2)
Effective Blood Flow: Fraction of Mixed Venous blood received by the lungs without contamination from shunt
__________________
(PvO2-MvO2)

19. Flamm Formula Average Oxygen Content in Chambers proximal to the Shunt
Method to calculate Mixed Venous Oxygen content
Need to factor in Contribution from IVC and SVC which is not equal
Flamm Equation:
3xSVC Oxygen Content + IVC Oxygen Content
______________________________________ 4

20. In the Absence of Shunt
PBF=SBF=EBF

21. How Significant is the Shunt?
Flow Ratio PBF/SBF
2.0 or more = Large Left to Right Shunt
1.0 or less= Net Right to left Shunt
No need to measure Oxygen consumption
Since this number will cancel out of the equation

22. Indicator Dilution Method
More Sensitive for smaller shunts
Cannot localize the level of left to right shunt
Left to Right : Dye (indocyanine green) is injected into pulmonary artery and a sample is taken from the systemic artery
Right to Left: dye injected just proximal to the presumed shunt and blood sample is taken from systemic artery

23. Interpretation of Indicator Dilution Method

24. Eisenmenger Syndrome defect in the septum between the atria
increased flow through the lungs after birth.
eventually result in pulmonary hypertension.
The first indication of this may be a reduction in heart size
flow overload is converted to a pressure overload ( to which the heart responds with hypertrophy, rather than dilatation ). Reduction in heart-size,
As the left-to-right shunt is converted by reversal of flow across the septum to right-to-left shunt, the patient becomes cyanotic from mixing of un-oxygenated blood.
Cyanosis is thus a late feature of Atrial Septal defect.
If cyanosis is present from birth, ASD will be complicated by one or more contributions:
Pulmonary Stenosis.
Patent Ductus, usually causes a very large pulmonary artery and enlargement of the aorta.
Common Atrium, allowing complete mixing of oxygenated and unoxygenated blood.
Truncus arteriosus, complete mixing at aortic level.

25. Pregnancy and ASD Well tolerated after closure
Increased risk of paradoxical emboli peri and post partum
Contraindicated in Eisenmenger Syndrome
Maternal mortality 50%
Fetal Mortality 60%

26. TTE and ASD
Transthoracic echocardiogram four chamber view to evaluate atrial septal defect. Note presence of inter-atrial communication between left and right atrium.

27. Indications for Intervention
Asymptomatic Children
Right Heart dilation
ASD> 5mm
No signs of Spontaneous Closure
Older Patients
Hemodynamically insignificant ASD with Qp/Qs<1.5 if concern for stroke
Pulmonary Hypertension
PA pressures> 2/3 systemic arterial resistance
Pulmonary artery reactivity with vasodilator challenge
Reversible changes on lung biopsy
Net L->R Shunt of 1.5:1

28. Treatment Options
1976, King et al published the first attempt to close an ASD with a double umbrella device
Size of the sheath was 23 Fr
Primary Method of to date for closure is surgical
Recent advances in interventional closure techniques

29. Trans-catheter Closure Technique
Implantation of one or more devices via catheter method
Eliminates need for cardio-pulmonary bypass
No need to stop the heart with cardioplegic agents

30. Patient Selection Strict Food and Drug Administration guidelines
Efficacy measured using data from strict follow up
Follow-up at regular intervals- 3, 6, and 12 months the year following the initial procedure
Any adverse events require follow up for 5-7 years

31. Patient Selection Defects smaller than 20-25mm in diameter
Should not have defects in the very upper or lower portions of the septum
Ostium Primum or Sinus Venosus, not good candidates because defect usually involves heart valves or abnormal venous drainage from the lungs
Only benefit Ostium Secundum defects
No lower age limit, but must weigh more than 8-10 kg

32. Trans-catheter Approach
Device is advance through an introducer sheath
One- Half of the device is deployed on left side of atrial septum, the second half is deployed on the right side
A “sandwich” is formed over the defect
6-8 weeks, device as a frame work for scar tissue to form
In children the new tissue formation with continue to grow

33. TTE post Intervention
Transesophageal echocardiogram showing Amplatzer device placed across the defect forming a “sandwich” over the atrial septal defect

34. TTE after intervention
Transthoracic echocardiogram four chamber view one day after Amplatzer device placement

35. Complete resolution of shunt
Transthoracic echocardiogram one day after Amplatzer device placed with highlighted area that shows no further shunting of blood across atrial septum.

36. Tissue formation over Helex device in canine model
In vivo tissue response demonstrating flat profile, conformance to the septum, and nonthrombogenic Occluder material; top photo shows left atrial view; bottom photo shows right atrial side view.

37. Trans-catheter Devices

38. Amplitizer Atrial Septal Defect Occluder
AGA Medical, Golden Valley Mn
2001- FDA approved for Secundum lesions
Nitinol mesh frame work and left/right atrial disks
Filled with poly-fabric to promote thrombosus
Cost $11K, Surgery$ 21K

39. Helex atrial septal defect device.
W.L. Gore & Associates
July 1999
Nitinol, nickel/titanium alloy
Wire frame in shape of coil with Gore-Tex
9 Fr introducer sheath
Cost: $6000

40. Helex Septal Occluder Delivery System components

41. Helex Septal Occluder Device components

42. Outcomes Amplatzer study 100 children and adults
Mean age 13.3
93 patients successful implantation
Occlusion rate at 3 months total occlusion
Improve RV and LV function and decreased LA volumes
Percutaneous Closure and Functional Capacity
32 adults mean age 43 yo
Qp/Qs 2.0+
6 months-improved O2 uptake with exercise as compared pre-closure status

43. Comparison to Surgery Study of children and young adults
Median age 9.8 y
442 underwent Amplatzer placement
154 underwent surgery
Success rate 100% surgery, 96 % Amplatzer
Complication 7% Amplatzer, 24 % surgery

44. Complication of Percutaneous Intervention
Early
Device Embolization
A. Fib, SVT
Heart Block
Pericardial Effusion
Groin Hematoma
Device Fractures
Cardiac Perforation
Device Erosion
Sudden Death

45. Participation in sports
th Bethesda Conference on Eligibility Recommendations for Competitive Athletes with Cardiovascular Abnormalities…
Small defect no Pulmonary HTN
partcipate in all sports
Large Defect, normal PA pressures
all competative sports
Moderate to large ASD and Pulmonary HTN sever-
no competative sports
ASD and mild Pulmonary HTN
Low intensisty sports

46. Follow Up 3-6 months post intervention
May participate in sports if no Pulm HTN, Heart Block, or Myocardial Dysfunction
Exercise evaluation if these conditions exist
American Heart Association, no endocarditis prophylaxis post corrrection of ASD unless patient has MR or MV malformation

47. Follow Up
Aspirin and Plavix 6 months post percutaneous closure