asd

1. ASD EMBRYOLOGY, ECHO ASSESSMENT AND DEVICE
CLOSURE
- DR. PRISCILLA
PG DNB CARDIOLOGY

2. INTRODUCTION:
• ASD is the most common congenital heart lesion in
adults and is often asymptomatic until adulthood.
• Diagnosis is important, as timely ASD repair improves
outcomes

3. • ASDs result from lack of sufficient tissue to completely
septate the atria and are classified according to their
location in the atrial septum.
• The location of the defect in relation to adjacent cardiac
structures defines the anomalies associated with the ASD
and impacts the natural history and requirements for
repair.

4. EMBRYOLOGY AND CLASSIFICATION

5. TYPES OF ATRIAL SEPTAL DEFECT

10. SEPTUM PRIMUM
• The development of the normal atrial septum occurs
following the initial looping of the heart that is after 28
days of gestation.
• The initial step in septation, a ridge of tissue develops
from the superior aspect of the primary atrial component
of the heart tube.
• This ridge is the primary septum (septum primum), and its
the leading edge is covered by cushion-like mesenchymal
tissue that is continuous over the dorsal mesocardium.

11. • As it grows into the atrial cavity, it extends down towards
the endocardial cushions that are developing
concomitantly within the atrioventricular canal.
• Normal septal development also involves incorporation of
another mass of tissue derived from the dorsal
mesocardium.

12. • This is known as the vestibular spine (spina vestibuli),
and it also carries on its leading edge a mesenchymal
cap.
• As the primary septum approaches the atrioventricular
endocardial cushions, the various mesenchymal
structures fuse together. The mass derived from the
vestibular spine then muscularises, eventually forming the
prominent infero-anterior border of the oval foramen

13. • After the fusion between the primary septum and the
endocardial cushions of the atrioventricular canal, the
upper part of the primary septum disintegrates to form the
‘ostium secundum’.
• Development of the ostium secundum occurs during the
fifth and sixth wks of embryologic life.

14. • The remaining part of the primary septum becomes the
flap valve of the oval fossa.
• This flap valve, along with the muscularised antero-
inferior rim, forms the true septum that separates the
cavities of the atrial chambers.

15. • Flow through the foramen ovale is essential for fetal
circulation.
• The foramen ovale closes spontaneously within the first
two years of life in 70 percent of children.
• However, in a significant proportion (20 to 30 percent) of
the population, the septum does not fuse, leading to a
patent foramen ovale

16. SEPTUM SECUNDUM
• After integration of the pulmonary veins into the left atrium
the superior walls of the two atriums ‘infold’, creating the
“septum secundum” in the superior portion of the atriums.
• Septum secundum is also concave in shape, with the
concavity directed more posteriorly toward the opening of
the sinus venosus of the primitive heart.
• It has 2limbs- Superior and inferior.
• Inferior limb fuses with the lowest portion of the atrial
septum.

17. • The flap valve overlaps, but is not completely adherent to,
the rims of this superior atrial fold, also known as
Waterston's or Sonderggard's groove, providing a
passage during fetal life for blood to pass from the right to
the left atrium .
• The opening in the septum secundum is called the
foramen ovale.

19. • Closure after birth –physiologically immediately
anatomically – 72 hours to 2 weeks .
• In about20% of cases, fusion of the septum primum and
septum secundum is incomplete,and a narrow oblique
cleft remains between the two atria.
• This condition is called probe patency of the oval
foramen; it does not allow intracardiac shunting of blood.

20. SECUNDUM ASD:
• SECUNDUM ASD accounts for 70 to 75 percent of all
ASDs.
• Secundum ASD is a defect in the septum primum
resulting from poor growth of the secundum septum or
excessive absorption of the septum
• Although most secundum ASDs are isolated defects,
familial forms exist, some of which are associated with
other congenital cardiac and extracardiac abnormalities.

21. • Other genes linked to familial isolated secundum ASD
include GATA 4,MYH6, NKX2-5.
• These syndromes typically present in childhood or
adolescence
• The genetic disorder associated with secundum ASD is
the HOLT ORAM SYNDROME (also known as heart-hand
syndrome) which is caused by various mutations, most
commonly mutations in the TBX5 gene

22. • Secundum ASDs are occasionally associated with partial
anomalous pulmonary venous connection and/or
pulmonary stenosis.
• The rare combination of an ASD with rheumatic mitral
stenosis is known as Lutembacher syndrome.

24. Primum ASD
• Primum ASD accounts for 15 to 20 percent of ASDs.
• A primum ASD is a defect in the septum secundum
caused by failure of the primum septum to fuse with the
endocardial cushions at the base of the interatrial septum.
• This results from maldevelopment/malalignment of the
ventricular septum due to malformation of the endocardial
cushions rather than a decrease in atrial septal tissue.

25. • Primum ASDs are nearly always associated with
anomalies of the atrioventricular (AV) valves, particularly a
cleft in the anterior mitral valve leaflet, with or without a
contiguous defect in the inlet ventricular septum.
• When the combination of the primum ASD, cleft mitral
valve, and an inlet ventricular septal defect are seen, this
is called a partial AV septal defect (AVSD).

26. • The most severe form of AVSD (or endocardial cushion
defect) is the complete AV septal (or canal) defect, in
which a primum ASD and inlet ventricular septal defect
are present along with a common AV valve
• The most severe form of AVSD (or endocardial cushion
defect) is the complete AV septal (or canal) defect, in
which a primum ASD and inlet ventricular septal defect
are present along with a common AV valve

29. Sinus venosus defect
• Sinus venosus defects account for 5 to 10 percent of
ASDs and are located in the venoatrial portion of the atrial
septum.
• Sinus venosus defects represent an abnormality in the
insertion of the superior or inferior vena cava, which
overrides the interatrial septum; the interatrial
communication is then formed within the mouth of the
overriding vein and is outside the area of the fossa
ovalis .

30. • Thus, sinus venosus defects are technically not ASDs
since the defect is within the sinus venosus septum.
• An anomalous connection involving one or more
pulmonary veins is present in most patients with sinus
venosus ASD
• Sinus venosus defects are of two types:
– SUPERIOR SINUS VENOSUS ASD
– INFERIOR SINUS VENOSUS ASD

31. SUPERIOR SINUS VENOSUS ASD:
• Superior sinus venosus defects are located immediately
below the orifice of the superior vena cava.
• The right upper lobe and middle lobe pulmonary veins
often connect to the junction of the superior vena cava
and right atrium or on the superior vena cava, resulting in
a partial anomalous pulmonary venous connection

32. INFERIOR SINUS VENOSUS ASD:
• Inferior sinus venosus defects, also known as inferior
vena caval defects, are much less common.
• They are located immediately above the orifice of the
inferior vena cava.
• These defects are also often associated with partial
anomalous connection of the right pulmonary veins to the
junction of the right atrium and inferior vena cava.

33. Unroofed coronary sinus:
• Unroofed coronary sinus (also known as coronary sinus
defect) is caused by absence of part or all of the common
wall between the coronary sinus and the left atrium.
• This defect accounts for less than 1 percent of ASDs and
is commonly associated with a persistent left superior
vena cava.

34. THANK YOU