Transcript 12/09 Atrial Septal Defect

Atrial Septal Defects
Imaging Conference
12/15/09
A. Zucker
Why do we care?
 Most common congenital heart defect
that presents during adulthood…
WeBecause
might have
diagnose
weto
can
fix it!! it
Outline:
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Embryology
Types of ASD
Presentation
Shunts
Echocardiographic evaluation
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MRI
ASD closure
ASD
 10-15% of congenital heart defects
 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 40-50 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
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.
Types of ASDs
Ostium Secundum
Ostium Primum
Sinus Venosus
Coronary Sinus Defects
Secundum ASD
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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.
Secundum ASD
 Associatd findings:
 MVP is present in 70% of pts with this type of ASD
 Partial anomalous pulmonary venous connection (rare)
 Specific EKG findings
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Right atrial abnormality
Prolonged PR
Right axis deviation (>100 degrees)
rSR’ in v1 (incomplete RBBB)
Notching of R wave peak (“crochetage sign”)
Secundum ASD
rSR’ in v1 (incomplete RBBB) and notching of the R wave peak (“crochetage sign”)
Secundum ASD
Secundum ASD
Primum ASD
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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
Primum ASD
 Mechanism of formation:
 Failure of the septum primum to fuse with the endocardial
cushions (i.e. the ostium primum remains unclosed)
 EKG findings:
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PR prolongation
Right atrial enlargement
Left axis deviation
rSR’ (incomplete RBBB)
Primum ASD
Left axis deviation, rSR’ (incomplete RBBB), and PR prolongation
Primum ASD
Primum ASD
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
Sinus Venosus Defect
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Associated Findings
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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
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P wave negative in III and aVF and positive in Avl
Junctional/ low atrial rhythms
Sinus Venosus Defect
Sinus Venosus Defect
Coronary Sinus ASD
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<1% of ASDs.
Mechanism of formation:
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Loss of the common wall between
coronary sinus and the left atrium
the
 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
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
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
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
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.
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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
Physical Findings
 “Left atrialization” of JVP (A=V wave)
 Hyperdynamic RV impulse
 RV heave
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PA tap
Split S1
S2 wide/fixed split
Murmurs
 Not hearing ASD (too little turbulance and too low velocity)
 Systolic:
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increased flow over pulmonic valve
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Mitral regurgitation
 Diastolic:
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Pulmonary regurgitation due to PA dilatation
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Increased flow across tricuspid valve
Echocardiographic Evaluation
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Subcostal view most reliable: US beam
perpendicular to plane of IAS
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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)
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
Echo:
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Identify:
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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
Echo: Secundum ASD
Echo: Secundum ASD
Echo: Secundum ASD
Echo: Primum ASD
Echo: Primum ASD
Echo: Primum ASD
Echo: Primum ASD
Doppler Echocardiography
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Color Doppler can identify left to right
flow
Subcostal view is best
Multiple views needed:
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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
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
Doppler Echocardiography
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Shunt calculation:
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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
Constast Echocardiography
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Microbubbles seen across IAS
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“Negative” contrast jet:
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Even if shunting predominantly L to R
RA pressure transiently > LA pressure
Flow from LA to RA appears as area with no
echo contrast
Rarely needed for ASD - more useful for
smaller shunts (PFO’s)
TEE
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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
MRI
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Phase constrast MRI compares well
against the gold standard (invasive
measurement)
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93% sensitivity and specificity for
Qp/Qs > or = 1.5:1
100% sensitivity and specificity for
Qp/Qs > or = 1.7:1
MRI
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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
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Possible that TEE will not be able to measure the largest
section of the ASD if it is not round
ASD Closure
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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
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Decreased LOS
Decreased complication rate
Same success rate
Determining factors:
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Location
Size
 <30 – 40 mm by TEE
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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
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
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
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.
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
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
ASD Closure
AI – anterior inferior rim, PS – posterior superior rim, PI – posterior inferior rim
ASD Closure
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TEE
 Can be used to evaluate suitability of
transcutaneous approach
 Monitoring during interventional procedure
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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
ASD Closure
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Decreased rim
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A more technically difficult
transcutaneous procedure with higher
rates of failure
Long term complications are increased
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Erosion of device through cardiac wall and
formation of fistulas.
Percutaneous Repair
Percutaneous Repair
Percutaneous Repair
ASD Closure
ASD Closure
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Surgical Indications
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Reserved for cases that are not candidates for
percutaneous closures:
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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)
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Concomitant MAZE a consideration
ASD Closure
 Surgical outcomes:
 Surgery before the age of 25 yields in 30-year survival
rates comparable to age- and sex-matched controls.
 At 25-40 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.
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.