1. Imaging Conference 12/15/09 A. Zucker
Atrial Septal Defects
Imaging Conference
12/15/09
A. Zucker

2. Because we can fix it!! We might have to diagnose it Why do we care?
Most common congenital heart defect that presents during adulthood…
We might have to diagnose it
Because we can fix it!!

3. Outline: Embryology Types of ASD Presentation Shunts
Echocardiographic evaluation
MRI
ASD closure

4. ASD 10-15% of congenital heart defects 1:1500 live births have an ASD
The 2nd most common congenital lesion found in adults (bicuspid aortic valve is the most common)
1:1500 live births have an ASD
Male: Female ratio is 1:2
Spontaneous closure is rare in children/ adults
Generally would have closed in infancy if it was going to close
Closure only seen in 4% of patients
Life expectancy is not normal, though many patients live to advanced age.
Natural survival beyond age is <50%.
The attrition rate after age 40 is ~6% per year
First open heart closure of an atrial septal defect (ASD) on September 5th, 1952

5. Embryology Septation of the atria
Septum primum arises from the superior portion of the common atria and grows caudally towards the endocardial cushions.
Before the septum primum closes off the atria, it develops a fenestration called the ostium secundum.
The septum secundum arises from the right atrial side of the septum primum and grows caudally.
The septum secundum does not completely divide the atria and does not immediately fuse with the septum primum.

7. Types of ASDs Ostium Secundum Ostium Primum Sinus Venosus
Coronary Sinus Defects

8. Secundum ASD Most common type of ASD (70-75%)
~7% of all congenital heart defects
Female predominance (2:1)
Includes all defects located in the area of the foramen ovales
Mechanisms of formation:
Septum secundum does not grow to cover the ostium secundum.
Ostium secundum is too large for the septum secundum to cover and so is left exposed despite a fully formed septum secundum.

9. Secundum ASD Associatd findings: Specific EKG findings
MVP is present in 70% of pts with this type of ASD
Partial anomalous pulmonary venous connection (rare)
Specific EKG findings
Right atrial abnormality
Prolonged PR
Right axis deviation (>100 degrees)
rSR’ in v1 (incomplete RBBB)
Notching of R wave peak (“crochetage sign”)

10. Secundum ASD
rSR’ in v1 (incomplete RBBB) and notching of the R wave peak (“crochetage sign”)

11. Secundum ASD

12. Secundum ASD

13. Primum ASD 15-20% of all ASDs Female to Male ratio is 1:1
Simplest form of AV canal defect
Generally associated with other anomalies
Commonly have AV valve defects, most notably a cleft in the anterior mitral valve leaflet
Defects of the ventriular septum
Common AV canal
Seen commonly in trisomy 21
40-50% of pts w/ Downs syndrome have CHD. Of these pts 65% are AV canal defects
Usually not a subtle finding

14. Primum ASD Mechanism of formation: EKG findings:
Failure of the septum primum to fuse with the endocardial cushions (i.e. the ostium primum remains unclosed)
EKG findings:
PR prolongation
Right atrial enlargement
Left axis deviation
rSR’ (incomplete RBBB)

15. Primum ASD
Left axis deviation, rSR’ (incomplete RBBB), and PR prolongation

16. Primum ASD

17. Primum ASD

18. Sinus Venosus Defect
1% of all congenital heat defects in the United States
Account for 10% of all ASDs
Not truly considered an ASD:
Abnormality in the insertion of the superior or inferior vena cava (which overrides the interatrial septum)
Two types:
Superior sinus venosus defects, located in the atrial septum immediately below the SVC
Inferior sinus venosus defects (less common), located in the atrial septum immediately above the IVC

19. Sinus Venosus Defect EKG changes Associated Findings
Both defects are often associated with a partial anomalous pulmonary vein connection with abnormal drainage
Pulmonary veins may be directed into the right atrium even if they are in the normal position
Pulmonary veins may also be completely displaced and insert into either vena cava
EKG changes
P wave negative in III and aVF and positive in Avl
Junctional/ low atrial rhythms

20. Sinus Venosus Defect

21. Sinus Venosus Defect

22. Coronary Sinus ASD <1% of ASDs. Mechanism of formation:
Loss of the common wall between the coronary sinus and the left atrium
Defect of at least a portion of the common wall separating the coronary sinus and the left atrium – AKA “unroofed coronary sinus”
Can be associated with a persistent left SVC draining into the coronary sinus

23. Shunting
Degree of shunt has implications as to whether to repair as ASD
Qp/Qs ratio correlates to the size of the ASD.
This falls apart when pulmonary hypertension is present
Repair of ASD when Qp/Qs (ratio of pulmonary flow to system flow) > 2:1 although some papers argue for 1.5:1
AHA recommends >1.5:1, but this excludes individuals over 21 yrs of age
Canadian Cardiac Society recommends Qp/Qs >2:1, or >1.5:1 in the presence of reversible pulmonary hypertension
Recalculation of Qp/Qs every 2-3 yrs

24. Shunting
Decreased ventricular compliance +/- increased left atrial pressure lead to an increase in shunting
Decrease ventricular compliance:
Systemic hypertension
Cardiomyopathy MI
Increase LA pressure
Mitral valve disease

25. Presentation
Often asymptomatic until the 3rd or 4th decade for moderate to large ASDs
Pts who present in infancy usually have associated cardiac defects
Fatigue
DOE
30% by 3rd decade
75% by 5th decade
Atrial arhythmias/ SVT and R sided HF:
10% by 4th decade
Increases with age
Arrhythmias present in ~20% of pts

26. Presentation Paradoxical embolus – stroke, TIA, or peripheral emboli:
Transient flow reversal secondary to increased R side pressures (valsalva)
PFO
Pulmonary hypertension
Migraine headaches:
PFO > ASD
Pulmonary hypertension:
Seen in less than 10% of pts w/ ASD at presentation
Seen in 50% of individuals above the age of 40.
Progression to Eisenmenger's syndrome occurs in 5 to 10% of individuals late in the disease process
Altitude intolerance
Increased decompression sickness and/or paradoxical emboli
Increased right to left shunting and decreased O2 saturations

27. Physical Findings “Left atrialization” of JVP (A=V wave)
Hyperdynamic RV impulse
RV heave
PA tap
Split S1
S2 wide/fixed split
Murmurs
Not hearing ASD (too little turbulance and too low velocity)
Systolic:
increased flow over pulmonic valve
Mitral regurgitation
Diastolic:
Pulmonary regurgitation due to PA dilatation
Increased flow across tricuspid valve

28. Echocardiographic Evaluation
Subcostal view most reliable: US beam perpendicular to plane of IAS
Other views may have loss of signal from the atrial septum from parallel alignment
Secundum ASD: central portion of atrial septum (89% sensitivity)
Primum ASD: adjacent to AV valve annuli (100% sensitivity)
Sinus Venosus defects: difficult to visualize on TTE (44% sensitivity)

29. Echocardiographic Evaluation
RV and RA size and function
Aids in evaluation of right to left shunt
Potentially the first abnormality noted on echocardiography
PW and CW Doppler to estimate RVSP and PA pressures
Drop-out of inferior portion of IAS can be seen on apical 4 or subcostal views
TV NOT more apically positioned than MV; at same horizontal level
Color to differentiate from dilated coronary sinus

30. Echo: Identify: Coronary sinus Entrance of pulmonary veins
Primum portion of atrial septum
Drop-out of inferior portion of IAS can be seen on apical 4 or subcostal views
TV NOT more apically positioned than MV; at same horizontal level
Color to differentiate from dilated coronary sinus

31. Echo: Secundum ASD

32. Echo: Secundum ASD

33. Echo: Secundum ASD

34. Echo: Primum ASD

35. Echo: Primum ASD

36. Echo: Primum ASD

37. Echo: Primum ASD

38. Doppler Echocardiography
Color Doppler can identify left to right flow
Subcostal view is best
Multiple views needed:
Low-velocity flow signal between atria
SVC flow along IAS can be mistaken for shunting
TR jet directed toward IAS can also be confused as a shunt

39. Doppler Echocardiography
Location and timing of flow critical (as oppsed to the velocity)
Flow from L -> R atrium in both systole and diastole
More prominent diastolic component
Can extend across open TV in diastole into RV
Seen in larger shunts
Flow acceleration on side of LA
Absolute velocity of flow less important

40. Doppler Echocardiography
Shunt calculation:
Can be performed utilizing these equations to relate pulmonic CO and systemic CO
Qp = TVI pulm X PULd
Qs = TVI lvot X LVOTd
Qp/Qs = shunt fraction
Significant usually if > 1.5/1.0 in ASD

41. Constast Echocardiography
Microbubbles seen across IAS
Even if shunting predominantly L to R
RA pressure transiently > LA pressure
“Negative” contrast jet:
Flow from LA to RA appears as area with no echo contrast
Rarely needed for ASD - more useful for smaller shunts (PFO’s)

42. TEE
Needed when TTE images are suboptimal
Usually necessary to see sinus venosus defect or partial anomalous pulmonary venous return
To locate small secundum ASDs
Device sizing before percutaneous closure
Estimation of defect size using the diameter of the Doppler color flow jet correlates with surgical findings
TEE is often used when contrast echo suggests shunting, but a defect can’t be visualized on TTE. The TEE then helps to differentiate between a PFO and a true ASD

43. MRI
Phase constrast MRI compares well against the gold standard (invasive measurement)
93% sensitivity and specificity for Qp/Qs > or = 1.5:1
100% sensitivity and specificity for Qp/Qs > or = 1.7:1

44. MRI
Correlation of PC-MRI to TEE and IVBM (invasive balloon measurement) measurements of ASD size
Some studies have noted MR to have better correlation to balloon sizing of ASDs than TEE
MR also able to provide information about shape of ASD and proximity to adjacent structures
Possible that TEE will not be able to measure the largest section of the ASD if it is not round

45. ASD Closure Percutaneous ASD closure was first performed 30 years ago
First report percutaneous ASD closure of via Amplatzer septal occluder in 1997
Successful closure in >80% of secundum ASDs
Compared to surgical approach
Decreased LOS
Decreased complication rate
Same success rate
Determining factors:
Location
Size
<30 – 40 mm by TEE
Rim
Initial studies used rim of ~5mm in all directions
Some authors have proposed that it is the posterior inferior rim in particular that must be of adequate size for successful transcatheter closure

46. ASD Closure Indications Asymptomatic in the presence of:
Right-sided cardiac dilatation
ASD > 5mm with no signs of spontaneous closure
Hemodynamics reserved for “borderline” cases
HD insignificant (Qp/Qs <1.5) - no closure required until later in life for embolism prevention after CVA
HD significant (Qp/Qs >1.5) - should be closed
In presence of PA HTN:
Defined as PAP > 2/3 systemic or PVR > 2/3 SVR
Closure can be recommended IF:
Net L--> R shunt of 1.5:1 or greater
Pulmonary artery reactivity upon challenge with pulmonary vasodilator
Lung biopsy evidence of reversibility to pulmonary arterial changes

47. ASD Closure Percutaneous indications:
Only for Secundum ASD with stretch diameter < 41 mm
Need adequate rims to enable secure device deployment
Cannot have anomalous pulm venous connection, be too proximal to AV valves, coronary sinus, or systemic venous drainage
~2/3rds of secundum ASDs meet this criteria

48. ASD Closure Introduced in 1996.
Approved for percutaneous ASD closure in 2001 by F.D.A.
Over 90,000 have been manufactured and delivered to date.
Consists of two round disks made of Nitinol (nickel + titanium) wire mesh linked together by a short connecting waist.

49. ASD Closure Amplatzer - advantages over other devices:
Can be delivered through smaller catheters
It is self-centering but can be repositioned easily
Has round retention disks that extend radially beyond the defect, which results in a much smaller overall size and firmer contact with the atrial septum
Shape enhances endothelialization and reducing the risk of residual shunting

50. ASD Closure Complications of percutaneous closure:
Thrombus formation on the device leading to CVA
Decreased in newer devices
ASA and plavix after procedure for ~6 months
Heart block, effusion, and thrombus formation in LA (2.4%)
Device embolization and/ or malposition (2.4%)
Atrial fibrillation (2.4%)
Erosion (0.1%):
aortic to right or left atrial fistula
Free-wall perforation of the atria resulting in tamponade
Factors associated with erosion:
Amplatzer Septal Occluder size greater than 4 mm larger than the unstretched ASD
Device size greater than 1.5 times the size of the unstretched ASD

51. ASD Closure
AI – anterior inferior rim, PS – posterior superior rim, PI – posterior inferior rim

52. ASD Closure
TEE
Can be used to evaluate suitability of transcutaneous approach
Monitoring during interventional procedure
Measure stretch diameter of ASD
Doppler to look for residual shunting during occlusion of the ASD with the balloon
Doppler to look for residual shunting after occluder is in place

53. ASD Closure Decreased rim
A more technically difficult transcutaneous procedure with higher rates of failure
Long term complications are increased
Erosion of device through cardiac wall and formation of fistulas.

54. Percutaneous Repair

55. Percutaneous Repair

56. Percutaneous Repair

57. ASD Closure

58. ASD Closure Surgical Indications
Reserved for cases that are not candidates for percutaneous closures:
Non-secundum ASDs
Secundum ASDs with unsuitable anatomy
Primary suture vs tissue/synthetic patch
Symptomatic improvement seen
Does not prevent AF/aflutter in adults (especially >40 years old)
Concomitant MAZE a consideration

59. ASD Closure Surgical outcomes:
Surgery before the age of 25 yields in 30-year survival rates comparable to age- and sex-matched controls.
At years of age, surgical survival is reduced, though not significantly if PA pressures are normal.
If PASP > 40 mmHg, late survival is 50% less than control rates, though life expectancy in surgically treated older patients is better than that of medically treated patients.
No benefit of surgery in reducing the incidence of AF, though the patient’s age at the time of closure is the most important predictor of the development of atrial arrhythmias.

60. Stroke Risk
Data are widely conflicting on the relationship between PFO, atrial septal aneurysm, and/or ASD and recurrent cerebral emboli.
Increased prevalence of PFO and ASA in cryptogenic stroke; less clear for ASD.
The role of defect closure vs. medical therapy for prevention of recurrent stroke is not well defined.
Aspirin is often used in setting of PFO or an isolated atrial septal aneurysm, and especially if PFO + ASA. Role of coumadin is not as clear – coumadin recommended if patient has a documented DVT/PE. Less data available for ASDs.
Surgical excision of an atrial septal aneurysm (without PFO or ASD) may be considered if aspirin or coumadin fail to prevent a recurrent embolic event.