Atrial Septal Defect

1. Atrial Septal Defect
Dr. Sayeedur Rahman Khan Rumi
Dr.rumibd@gmail.com
MD (Cardiology) Final Part Student
NHFH&RI

2. Definition
• An atrial septal defect is a communication between
the atria resulting from a deficiency of tissue in the
septum, as distinguished from a patent foramen
ovale, where septum primum, though preserved, is
not adherent to the superior limbic band of septum
secundum.

3. Prevalence
• Atrial septal defect (ostium secundum defect) occurs
as an isolated anomaly in 5% to 10% of all congenital
heart defects (CHDs).
• Male:Female = 1:2
• About 30% to 50% of children with CHDs have an ASD
as part of the cardiac defect.
• Excluding bicuspid aortic valve and mitral valve
prolapse, ASD is the most common form of congenital
heart defect found among adults and is the most
common acyanotic shunt lesion in adults as well.

4. EMBRYOLOGY

5. • The primitive atrium is first
partitioned into right and
left atria by growth of the
septum primum—a thin,
crescent-shaped
membrane that grows
from the roof of the
primitive atrium toward
the endocardial cushions.
• Foramen primum,
composed of the free edge
of the septum primum and
the endocardial cushions.

6. • Fenestrations develop in
the septum primum that
coalesce to form the
ostium secundum.
• As the septum primum
then fuses with the
endocardial cushions, the
ostium secundum
maintains a right-to-left
atrial flow that is important
in the fetal circulation.
• Failure of this fusion
results in the development
of a primum ASD.

7. • A second septum, the
septum secundum,
then forms to the right
of the septum
primum, growing
toward the
endocardial cushions
and usually closing the
ostium secundum.
• Failure to close the
ostium secundum
results in the
formation of a
secundum ASD.

8. ANATOMY
• When viewed from its right
aspect, the atrial septum is
composed of interatrial and
atrioventricular regions.
• The interatrial portion is
characterized by the fossa
ovalis, which is the anatomic
hallmark of a morphologic
right atrium.
• When viewed from the left
atrium, the atrial septum is
entirely interatrial because
the atrioventricular
component lies below the
mitral annuls between the
left ventricle and right
atrium.

9. Anatomic Types
• Ostium secundum defects
or secundum ASD
• Ostium primum defects or
primum ASD
• Sinoseptal defects
• SVC type
• IVC type
• Coronary sinus ASD

10. Ostium secundum defects or secundum ASDs
• The most common type, 70% to 75% of ASDs.
• Location: in the midportion of the atrial septum, within
or including the fossa ovalis.
• Defects result from a deficient septum primum or an
abnormally large foramen secundum.
• Two times more common in female patients.
• Association:
• Mitral valve prolapse and other forms of congenital heart
disease.
• It may also be associated with rheumatic mitral stenosis (i.e.,
Lutembacher syndrome).

11. Ostium primum defects or primum ASDs
• 15% to 20% of ASDs and are part of the spectrum of
atrioventricular (AV) septal defects (also known as AV
canal defects or endocardial cushion defects).
• Location: These defects occur in the inferior–anterior
portion of the atrial septum.
• Association: Cleft in the anterior leaflet of the mitral
valve, leading to varying degrees of mitral
regurgitation.
• In their complete form, they include a large ventricular
septal defect and a common AV valve.
• Most common ASD type associated with Down’s
syndrome.

12. Sinoseptal defects
• Constitute the remaining 5% to 10% of septal defects.
• These lesions involve the portion of the atrial wall
derived from the sinus venosus (i.e., there is no direct
communication between the right and left atria)
• Location: Sinus venosus defects are typically at the
orifice of the superior vena cava (SVC) at the junction
of the right atrium or, less frequently, in the region of
the inferior vena cava (IVC).
• Association: with partial anomalous pulmonary
venous drainage of the right pulmonary veins

13. Abnormal Physiology
• With moderate to large defects, no resistance to blood
flow across the defect is present, resulting in
equalization of pressure between the 2 atria.
• A left-to-right shunt of blood occurs because :
1. the right atrium is more distensible than the left,
2. the tricuspid valve is normally more capacious than
the mitral valve, and
3. the thin-walled, compliant right ventricular chamber
accommodates a larger volume of blood at the same
filling pressure than does the left ventricle.

14. Natural History
• In patients with an ASD smaller than 3 mm in size
diagnosed before 3 months of age, spontaneous
closure occurs in 100% of patients at 1½ years of age.
• Spontaneous closure occurs more than 80% of the time
in patients with defects between 3 and 8 mm before
1½ years of age.
• An ASD with a diameter larger than 8 mm rarely closes
spontaneously.
• Spontaneous closure is not likely to occur after 4 years
of age
• Most children with an ASD remain active and
asymptomatic. Rarely, congestive heart failure (CHF)
can develop in infancy.

15. • If a large defect is untreated, CHF and pulmonary
hypertension begin to develop in adults who are in
their 20s and 30s, and it becomes common after 40
years of age.
• With or without surgery, atrial arrhythmias (flutter or
fibrillation) may occur in adults. The incidence of atrial
arrhythmias increases to as high as 13% in patients
older than 40 years of age.
• Infective endocarditis does not occur in patients with
isolated ASDs.
• Cerebrovascular accident, resulting from paradoxical
embolization through an ASD, is a rare complication.

16. CLINICAL
MANIFESTATIONS

17. History
• Infants and children with ASDs are usually
asymptomatic
• Exercise intolerance with fatigue and dyspnea may
occur
• Frequent pulmonary infections
• Palpitations
• Occasionally, a paradoxical embolus causing a stroke or
transient ischemic attack (TIA) is the first clue to an
ASD.

18. Physical Examination
• A relatively slender body
build is typical.
• In the older child,
prominence of the left
anterior chest is
common, and a
hyperdynamic right
ventricular systolic lift
can be felt.
• A widely split and fixed
S2 and a grade 2 to 3 of
6 systolic ejection
murmur are
characteristic findings of
ASD in older infants and
children.

19. • If a shunt fraction (Qp/Qs) of 2.5:1, there may be a
diastolic murmur secondary to increased flow across the
tricuspid valve.
• A loud P2 component of the second heart sound
indicates the presence of pulmonary hypertension,
which can affect up to 20% of patients; if cyanosis is
present, this generally suggests advanced pulmonary
hypertension with reversal of shunt flow (Eisenmenger
syndrome).
• Classic auscultatory findings of ASD are not present
unless the shunt is reasonably large.
• The typical auscultatory findings may be absent in infants
and toddlers, even in those with a large defect because
the RV is poorly compliant.

20. Investigations

21. ECG
Secundum ASD:
• RSR’ pattern in lead V1
• QRS duration < 0.11 seconds (incomplete right bundle branch
block)
• Right-axis deviation
• RV hypertrophy
• First-degree AV block (20%)
• RA enlargement (about 50%) with a prominent P wave in lead II
Primum ASD:
• RSR’ pattern in lead V1
• Left-axis deviation
• First-degree AV block, classically seen with right bundle branch
block and left anterior fascicular block

23. Chest radiography
• Cardiomegaly with enlargement of the RA and right
ventricle (RV) may be present.
• A prominent pulmonary artery (PA) segment and
increased pulmonary vascular markings are seen
when the shunt is significant.

24. CXR P/A & Lat views from a 10-year-old child with atrial septal defect.
The heart is mildly enlarged with involvement of the RA (best seen in
the P/A view) and the RV (best seen in the lateral view with
obliteration of the retrosternal space). Pulmonary vascularity is
increased, and the main pulmonary artery segment is slightly
prominent.

25. Echocardiography
A two-dimensional echocardiographic study is diagnostic. The study
shows the position as well as the size of the defect, which can best be
seen in the subcostal four chamber view.
A. The SVC type of sinus venosus defect shows a defect in the
posterosuperior atrial septum.
B. In secundum ASD, a dropout can be seen in the midatrial septum.
C. The primum type shows a defect in the lower atrial septum.

26. • Indirect signs of a significant
left-to-right atrial shunt
include RV enlargement and
RA enlargement, as well as
dilated PA, which often
accompanies an increased
flow velocity across the
pulmonary valve.
• Pulsed Doppler examination
reveals a characteristic flow
pattern with the maximum
left-to-right shunt occurring in
diastole.
• Color-flow mapping enhances
the evaluation of the
hemodynamic status of the
ASD.

27. • M-mode
echocardiography may
show increased RV
dimension and
paradoxical motion of
the interventricular
septum, which are
signs of RV volume
overload.

28. • In older children and
adolescents, especially
in those with
overweight, adequate
imaging of the atrial
septum may not be
possible with the
ordinary transthoracic
echocardiographic study.
Transesophageal
echocardiography (TEE)
may be used as an
alternative.

29. Cardiac catheterization
Typically not required for diagnostic purposes except to assess
pulmonary pressures and resistance or as part of a planned
transcatheter device closure.
Oximetry measurements:
• Oximetry samples obtained during catheterization
demonstrate a step-up within the right atrium due to shunting
across the defect.
Hemodynamic assessment:
• An important assessment is comparison of pulmonary artery
pressure with systemic pressure and measurement of
pulmonary vascular resistance. If pulmonary pressures are
elevated, the response to oxygen or other vasodilators should
be assessed. Alternatively, the ASD can be balloon occluded
with assessment of hemodynamics to ensure that closure is
safe.

30. Cardiac MRI
• Can be helpful, as it can provide additional
information beyond echocardiography.

31. Management

32. Medical
• Exercise restriction is unnecessary.
• In infants with CHF, medical management (with a
diuretic) is recommended.
• Rhythm disturbances such as atrial fibrillation
require attention with respect to rate control and
anticoagulation.
• Endocarditis antibiotic prophylaxis during dental
procedures is not required in the setting of an
isolated ASD before surgery, but it is warranted for
6 months after surgical or device closure (AHA/ACC
class IIa).

33. Surgical or transcatheter therapy
Timing:
For asymptomatic infants and children, closure is
recommended at approximately 5 years of age
Indications:
• If there is evidence of
• hemodynamically significant shunt (Qp/Qs ≥ 1.5:1),
• evidence of right heart dilation,
• evidence of probable paradoxical embolism
• associated symptoms.

34. Contraindications:
• Defect is too small to be hemodynamically
significant
• Pulmonary vascular resistance more than one-half
of the systemic vascular resistance or
• An indexed pulmonary vascular resistance > 7
Wood units/m2
• Severe LV dysfunction, where ASD is acting as a
“pop-off” valve for the left ventricle
• In most cases where ASD is diagnosed in pregnancy,
closure can be postponed until 6 months after
delivery

35. Transcatheter closure
• Any patient with an isolated secundum ASD may be
suitable for transcatheter closure.
• Transcatheter device closure of secundum type ASD was
first performed in 1976 by Mills and King
• In the United States, currently only the Amplatzer septal
occluder and Helex septal occluder are approved for
secundum ASD closure.
• The use of the closure device may be indicated to close
a secundum ASD measuring ≥ 5 mm in diameter (but
less than 32 mm for Amplatzer device and less than 18
mm for Helex device)

36. • There must be
enough rim (4 mm)
of septal tissue
around the defect for
appropriate
placement of the
device.
• The defect must be
located centrally with
adequate room for
the device to be
positioned, without
interference of other
intracardiac
structures such as
the AV valves,
coronary sinus, or
pulmonary veins.

37. • The Amplatzer Septal Occluder (AGA Medical Corporation,
Golden Valley, MN) approved in December 2001.
• The Amplatzer device consists of two disks made of
Nitinol wire mesh filled with polyester fabric and
separated by a narrower waist, which is appropriately
fitted by balloon sizing

39. • The Helex Septal
Occluder (WL Gore &
Associates, Flagstaff, AZ)
approved in August 2006.
• The Helex device is also
disklike and consists of
expanded
polytetrafluoroethylene
(ePTFE) patch material
supported by a single
Nitinol wire frame.

40. Complications
• Complications are extremely rare (major complication
rate of 1.6%, including device embolism with surgical
removal).
• The overall risk of the procedure is 7.2%
• Probably the most feared complication with the
Amplatzer device (but not with the Helex device) is
early or late erosion of the device into the aortic root,
with subsequent pericardial tamponade and rare
death. It may be related to the oversizing of devices
and deficiency of the anterosuperior (or retroaortic)
rim.
• Release of nickel from the device (with peak at 1
month after implant) is a rare cause of significant
allergic reaction

41. Postdevice Closure Follow-up
• After closure, antiplatelet therapy, frequently aspirin
and clopidogrel, is prescribed for a minimum of 6
months, after which time the device is generally
believed to have endothelialized.
• Postprocedure echocardiographic studies check for a
residual atrial shunt and unobstructed flow of
pulmonary veins, coronary sinus, and venae cavae, and
proper function of the mitral and tricuspid valves.
• If 1-month and 1-year follow-up echocardiographic
findings are normal then yearly or biennial follow-up
will suffice.

42. Surgical closure
Indications:
• Surgical closure is indicated only when device closure is
not considered appropriate.
• It is the treatment of choice for ostium primum and
sinus venosus defects.
• Patients with secundum ASDs and anatomy that is not
amenable to percutaneous closure:
 ASD diameter > 35 mm
 inadequate septal rims to permit device deployment
 close proximity to AV valves, coronary sinus, or venae cavae
are also candidates for open surgical closure.

43. Timing
• Surgery is usually delayed until 2 to 4 years of age
because the possibility of spontaneous closure
exists.
• If CHF does not respond to medical management,
surgery is performed during infancy (if device
closure is considered inappropriate)

44. Procedure:
• Depending on the
defect size and
location, the
secundum ASD can
be closed by primary
suture or, if needed,
by the use of an
glutaraldehyde
treated autologous
pericardial or
synthetic patch.

45. • Ostium primum
defects require
patch closure as
well as repair of
the cleft mitral
valve.

46. • Repair of sinus
venosus defects is
technically more
challenging, as
the pulmonary
veins often have
anomalous
drainage and
require rerouting.

47. Preoperative risk factors:
• Older age at operation,
• Presence of atrial fibrillation, and
• Elevated pulmonary pressure and resistance.
Mortality: < 0.5%
Complications:
• Cerebrovascular accident
• Postoperative arrhythmias may develop in the immediate
postoperative period.
• Postpericardiotomy syndrome

48. Postoperative Follow-up
• Cardiomegaly on chest radiographs and enlarged
RV dimension on echo as well as the wide splitting
of the S2 may persist for 1 or 2 years after surgery.
• The ECG typically demonstrates RBBB (or RV
conduction disturbance).
• Atrial or nodal arrhythmias occur in 7% to 20% of
postoperative patients.
• Occasionally, sick sinus syndrome, which occurs
especially after the repair of a sinus venosus defect,
may require antiarrhythmic drugs, pacemaker
therapy, or both.

49. Thank you