Transcript ASDx

Atrial Septal Defect
DR. JAWAD ALZAMIL
DEMONSTRATOR
KFCC,KKUH
Outlines:
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Defenition.
Embryology
Anatomy.
Physiology.
Pathophysiology.
Types.
Clinical features.
Diagnosis.
Treatment.
Follow up.
Defenition:
 Congenital cardiac
anomaly characterized
by a defect in the
interatrial septum –other
than PFO- allowing
pulmonary venous
return from the left
atrium to pass directly
to the right atrium.
http://emedicine.medscape.com/article/162914-overview
Is it an ASD???
Embryology:
http://www.hmc.org.qa/hmc/heartviews/H-V-v3%20N2/5.htm#
Cont.
 During the first 23 days of the embryo’s life, the
atrial chamber is a common one and connected to
the sinus venosus to drain the blood coming from
right and left vens horns. After completion of
cardiac looping by the third week, atrial septation
begins by developing the septum primum partly
from the endocardial cushion tissue. It is
important to note that there is always atrial
communication between the left and right sides
throughout all developmental stages to maintain
adequate right to left shunt and oxygenate the
developing brain tissue.
http://www.hmc.org.qa/hmc/heartviews/H-V-v3%20N2/5.htm#
Cont.
 Even before the completion of the septum
primum, fenestrations start to take place in this
septum to allow blood to flow freely though it. By
the early fifth week of fetal life, the septum
secondum starts to appear from the superiorposterior aspect of the mid-atrial wall and extends
inferiorly and anteriorly, leaving a flap of the
septum primum in the mid-portion to be
uncovered. This flap is pushed by the blood flow
coming from the umbilical vein and remains open
till the end of pregnancy
http://www.hmc.org.qa/hmc/heartviews/H-V-v3%20N2/5.htm#
Frequency:
 Atrial septal defect (ASD) account for 10% of all
congenital heart disease and as much as 20-40% of
congenital heart disease presenting in adulthood.
 Sex: ASD occurs with a female-to-male ratio of 2:1
 Age: Patients with ASD can be asymptomatic through
infancy and childhood, though it depends on the
degree of left-to-right shunt. Symptoms become more
common with advancing age. By the age of 40 years,
90% of untreated patients have symptoms of
exertional dyspnea, fatigue, palpitation, arrhythmia,
or heart failure
http://emedicine.medscape.com/article/162914-overview
Types:
ASD SECUNDUM 75%: A large
foramen ovale occur as a result of
defective development of the septum
secundum, a combination of excessive
resorption of the septum primum and a
large foramen ovale produces a large
ostium secundum ASD
Coronary sinus ASD:
Coronary sinus defect is
characterized by unroofed
coronary sinus and
persistent left superior vena
cava that drains into the left
atrium. A dilated coronary
sinus often suggests this
defect. This can result is
desaturation due to right-toleft shunt into the left
atrium. The diagnosis can
be made by injecting
contrast agent into left upper
extremity; coronary sinus
opacification precedes right
atrial opacification
Sinus venosus ASD 5-10%: Abnormal fusion between the
embryologic sinus venosus and the atrium causes these defects. In most
cases, the defect lies superior in the atrial septum near the entry of
superior vena cava. Often there is associated anomalous drainage of the
right superior pulmonary vein. The relatively uncommon inferior type
is associated with partial anomalous drainage of the right inferior
pulmonary vein into the right atrium, the superior vena cava, or the
inferior vena cava.
Ostium primum ASD 15-20%: caused by
incomplete fusion of septum primum with the
endocardial cushion. The defect lies adjacent
to the atrioventricular (AV) valves, either of
which may be deformed and incompetent. In
most cases, only the anterior or septal leaflet
of the mitral valve is displaced, and it is
commonly cleft. The.tricuspid valve is
usually not involved.
Cont.
So the classification
according to their location
relative to the fossa ovalis.
Genetics:
 Holt-Oram syndrome characterized by an
autosomal dominant pattern of inheritance and
deformities of the upper limbs. The penetrance
is nearly 100%.
 syndrome familial ASD !! :Mutations in the
cardiac transcription factor NKX2.5 have been
attributed to the syndrome. Is it like simple
ASD?
No, it is associated later in life with
progressive AV block.
Smits JP, Veldkamp MW, Wilde AM (2005) Mechanisms of inherited cardiac conduction disease. Europace 7:122-137.
Pathophysiology:
 The magnitude of the left-to-right shunt across the ASD
depends : the defect size, the relative compliance of the
ventricles, and the relative resistance in both the pulmonary
and systemic circulation. With small ASD, left atrial pressure
may exceed right atrial pressure by several millimeters of
mercury, whereas with large ASD, mean atrial pressures are
nearly identical. Shunting across the interatrial septum is
usually left-to-right and occurs predominantly in late
ventricular systole and early diastole. Likely some
augmentation occurs during atrial contraction. Note,
however, that a transient and small right-to-left shunt can
occur, especially during respiratory periods of decreasing
intrathoracic pressure, even in the absence of pulmonary
arterial hypertension.
http://emedicine.medscape.com/article/162914-overview
Cont.
 The chronic left-to-right shunt results in increased
pulmonary blood flow and diastolic overload of
the right ventricle. Resistance in the pulmonary
vascular bed is commonly normal in children with
ASD, and the volume load is usually well
tolerated even though pulmonary blood flow may
be more than 2 times systemic blood flow. Altered
ventricular compliance with age can result in an
increased left-to-right shunt contributing to
symptoms. The chronic significant left-to-right
shunt can alter the pulmonary vascular resistance
leading to pulmonary arterial hypertension, even
reversal of shunt and Eisenmenger syndrome.
http://emedicine.medscape.com/article/162914-overview
Cont.
 Because of an increase in plasma volume
during pregnancy, shunt volume can increase,
leading to symptoms. Pulmonary artery
pressure usually remains normal.
http://emedicine.medscape.com/article/162914-overview
Effect on the heart:
 http://www.youtube.com/watch?v=e46jtin-H50
 This extra blood from the left atrium may cause a
volume overload of both the right atrium and the right
ventricle, which if left untreated, can result in
enlargement of the right side of the heart (in case of
Large ASD)
 The right ventricle will have to push out more blood
than the left ventricle due to the left-to-right shunt.
This constant overload of the right side of the heart
will cause an overload of the entire pulmonary
vasculature. Eventually the pulmonary vasculature
will develop pulmonary hypertension to try to divert
the extra blood volume away from the lungs.
http://en.wikipedia.org/wiki/Atrial_septal_defect
Cont
 The pulmonary hypertension will cause the right ventricle to
face increased afterload in addition to the increased preload
that the shunted blood from the left atrium to the right atrium
caused. The right ventricle will be forced to generate higher
pressures to try to overcome the pulmonary hypertension.
This may lead to right ventricular failure (dilatation and
decreased systolic function of the right ventricle) or
elevations of the right sided pressures to levels greater than
the left sided pressures.
 When the pressure in the right atrium rises to the level in the
left atrium, there will no longer be a pressure gradient
between these heart chambers, and the left-to-right shunt will
diminish or cease.
Cont.
 If left uncorrected, the pressure in the right side of the
heart will be greater than the left side of the heart.
This will cause the pressure in the right atrium to be
higher than the pressure in the left atrium. This will
reverse the pressure gradient across the ASD, and the
shunt will reverse; a right-to-left shunt will exist.
This phenomenon is known as Eisenmenger's
syndrome.
 Once right-to-left shunting occurs, a portion of the
oxygen-poor blood will get shunted to the left side of
the heart and ejected to the peripheral vascular
system. This will cause signs of cyanosis.
Cont.
 So we can say on the Heart:
1. Dilatation of right atrium and Ventricle.So what
about the risk of Mural thrombus?
uncommon
2. Dilated and mildly thickened incompetent
tricuspid and pulmonary valves.
3. Dilatation of MPA.
4. Mildly dilated left atrium.How about left
ventricle?
Normal if isolated ASD
Cont.
 On the Lung: (with chronic volume overload):
1. Dilatation of pulmonary vascular bed.
2. Severe and irreversible hypertensive
pulmonary vascular disease develop ( in few
patient with striking female predominance).
3. Mainly in adults: chronic pulmonary venous
hypertension
LVH LVF or chronic
hypoxic pulmonary hypertension chronic
obstructive or interstitial pulmonary disease