Atrial Septal Defect

1
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

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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
• Pulmonary Blood Flow Systemic Blood Flow
• Shunt Suspected If
• Pulmonary Artery Saturation gt80 (?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

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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

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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 patients
  age, gender and body surface area when not
  directly measured

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Shunt Quantification

• Pulmonary 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
• Oxygen Consumption
• __________________
• (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

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In the Absence of Shunt

• PBFSBFEBF

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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

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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.

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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

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TTE and ASD

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

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Indications for Intervention

• Asymptomatic Children
• Right Heart dilation
• ASDgt 5mm
• No signs of Spontaneous Closure

• Older Patients
• Hemodynamically insignificant ASD with Qp/Qslt1.5
  if concern for stroke
• Pulmonary Hypertension
• PA pressuresgt 2/3 systemic arterial resistance
• Pulmonary artery reactivity with vasodilator
  challenge
• Reversible changes on lung biopsy
• Net L-gtR Shunt of 1.51

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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

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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

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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

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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

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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.

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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

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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

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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

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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

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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

• 2005 36th 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

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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