Atrial septal defect (ASD)

ATRIAL SEPTAL
DEFECT
BY GROUP 1: KARISHMA K SHAH, RESHMA
NAYAK & CHELSEA REJI
(MAHE, MCHP, Bsc.CVT)

CONTENTS
◦ DEFINITION
◦ PREVALENCE AND INCIDENCE
◦ GENETICS
◦ EMBRYOLOGY
◦ CLASSIFICATION
◦ PATHOPHYSIOLOGY
◦ RIMS
◦ CLINICAL MANIFESTATIONS
◦ DIAGNOSTIC TESTS
◦ MANAGEMENT
KARISHMA SHAH RESHMA NAYAK CHELSEA REJI

DEFINITION
◦ Atrial septal defect (ASD) is a heart defect that is present at birth (congenital).
◦ As a baby develops in the womb, a wall (called the interatrial septum) forms that
divides the upper chamber into a left and right atrium.
◦ An abnormal formation of this wall can result in a hole that remains after birth.
◦ This defect allows oxygen-rich blood to leak into the oxygen-poor blood chambers in
the heart.
◦ ASD refers to an opening between the 2 atria other than the component of the
Foramen Ovale.

PREVALENCE
◦ 30-50% of children with CHD have an ASD as a part of Cardiac defect.
◦ ASD (ostium secundum defect) occurs as an isolated anomaly in 5 % to 10% of all congenital heart
defects.
◦ It is more common in females than in males (male/female ratio of 1:2).
INCIDENCE
◦ The true incidence of interatrial defects is underestimated due to the high rate of spontaneous closure
and the delay in the presentation into adulthood due to subtle signs and symptoms.

GENETICS
◦ The genetic basis of the ASD is not completely understood.
◦ In the majority of cases this is a sporadic lesion, yet some gene defects have been found to explain some
of the well-known familial cases with ASDs, such as NKX2- chromosome 5, which has an autosomal
dominant inheritance and AV conduction defect.
◦ Other genetic syndromes with skeletal abnormality such as Holt-Oram syndrome, which is caused by
mutations in the transcription factor TBX5, essential in the development of both the heart and upper
limbs.
◦ Atrial septal defects can be part of many other syndromes and more complex congenital heart diseases.
Down syndrome is associated with both primum and secundum ASD, while Noonan syndrome most
commonly is associated with secundum ASD and pulmonary valve stenosis

EMBRYOLOGY
◦ Heart begins to develop in the middle of the 3rd week from the aggregation of the
splanchnic mesoderm cells in the cardiogenic area.
◦ 2 endocardial tubes are developed
◦ The 2 tubes fuse to form a single tube
◦ The heart tube differentiates into:
1. Truncus Arteriosus
2. Bulbus cordis
3. Primitive ventricle
4. Primitive atria
5. Sinus venosus

EMBRYOLOGY
◦ The heart tube then undergoes looping from day 23 to day 28 where the :
1. Cephalic portion bends ventrally, caudally and to the right
2. Caudal portion bends dorsocranially and to the left

EMBRYOLOGY
◦ The development of the normal atrial septum occurs following the initial looping of the
heart that is after 28 days of gestation.
◦ The SEPTUM PRIMUM arises from the roof of the atrium to the left of the septum
spurium. It grows downwards towards the atrioventricular canal and ultimately fuses
with the septum intermedium.

EMBRYOLOGY
◦ Throughout the fetal life oxygenated blood reaches the RA from the placenta. This
blood has to reach the LA. For this purpose, a communication between the 2 atria is
essential.
◦ Before the septum primum fuses with the septum intermedium, blood flows through
the gap between them. This gap is referred to as the FORAMEN PRIMUM.
◦ Before foramen primum can be closed it is essential that another path for the flow of
blood is created.
◦ This is achieved by breaking down of the upper part of the septum primum.
◦ New gap is referred to as FORAMEN SECUNDUM.

EMBRYOLOGY
◦ The septum primum now has a free upper edge.
◦ The SEPTUM SECUNDUM grows down from the roof of the
atrial chamber to the right of the septum primum.
◦ As it grows, it comes to overlap and the blood has to flow
through the interval between the septa. This gap is referred
to as FORAMEN OVALE.
◦ After birth the foramen ovale is obliterated by the fusion of
the septum primum and septum secundum.

EMBRYOLOGY
◦ Any abnormality in the formation of the IAS results in an ASD:
◦ SECUNDUM ASD occurs secondary to deficiency of septum primum in majority of the
cases and rarely due to deficient septum secundum. Occurs in the fossa ovalis position.
◦ PRIMUM ASD occurs as a result of abnormal formation of the endocardial cushion. Are
usually anteroinferior in location relative to the fossa ovalis.
◦ SINUS VENOSUS and CORONARY SINUS defects occur as a consequence of abnormal
development of embryologic venous tributaries.

CLASSIFICATION
◦ OSTIUM SECUNDUM ASD:
Most common type; 50-70% of all ASDs
This defect is present at the site of Fossa Ovalis, allowing L R shunting of blood from
LA to RA
PAPVC is present in about 10% of the cases
◦ OSTIUM PRIMUM ASD:
Occurs in 30% of all ASDs, if those that occur as part of complete endocardial cushion
defect.
Isolated ostium primum ASD occurs in about 15% of all ASDs.

CLASSIFICATION
◦ SINUS VENOSUS DEFECT:
Occurs in about 10% of all ASDs.
There are 2 types; SVC and IVC type
The defect is most commonly located at the entry of the SVC into the RA and rarely at
the entry of the IVC into the RA.
Commonly associated with PAPVC (RUPV RA)
Is often associated with anomalous Pulmonary venous drainage of the Right lung into
the IVC (SCIMITAR SYNDROME)

CLASSIFICATION
◦ CORONARY SINUS DEFECT:
There is a defect in the roof of the coronary sinus and the LA blood shunts through the
defect and empties into RA through the CS Ostium, producing clinical picture similar to
other types of ASDs.
This is usually seen in dilated coronary sinus opening into RA and is often associated
with a persistent left SVC.
NB: Mitral valve prolapse (MVP) occurs in 20% of patients with either ostium
secundum or sinus venosus defects

CLASSIFICATION

CLASSIFICATION
BASED ON SIZE:
1. McMohan et al (2000):
Small; >3mm - <6mm
Moderate; ≥6 - <12mm
Large; ≥12mm
2. Anita Saxena (2005):
Small; 4-5mm
Medium; 6-8mm
Large; > 8mm KARISHMA SHAH RESHMA NAYAK CHELSEA REJI

PATHOPHYSIOLOGY
◦ The degree of the left to right shunting is dependent on:
The size of the defect
The relative compliance of the RV and LV
The relative vascular resistance in the pulmonary and systemic circulations.

PATHOPHYSIOLOGY
In moderate-to-large defects, a considerate shunt of oxygenated blood flows from the left to the right atrium
Volume overload and dilatation of the right atrium and ventricle
Increased flow across Tricuspid and Pulmonary Valves
The tricuspid and pulmonary annuli may dilate and become incompetent
Increased flow into the lungs
Pulmonary arteries, capillaries & veins are dilated

PATHOPHYSIOLOGY
Flow- related pulmonary artery hypertension
Medial hypertrophy of pulmonary arteries and muscularization of arterioles resulting in PVOD
Reversal of the shunt
Eisenmenger syndrome

RIMS
◦ AORTIC RIM – The superior/anterior rim between the ASD and aortic annulus and
aortic root.
◦ AV VALVE RIM – The inferior/anterior rim between the ASD and the AV valves.
◦ SVC RIM – The superior/posterior rim between the ASD and the SVC.
◦ IVC RIM – The inferior/posterior rim between the ASD and the IVC.
◦ POSTERIOR RIM – The posterior rim between the ASD and the posterior atrial walls.
◦ RIGHT UPPER PV RIM – The posterior rim between the ASD and RUPV.

CLINICAL MANIFESTATIONS
◦ HISTORY
Infants and children are usually asymptomatic.
Most of the patients present symptoms at the 4-5th decade.
◦ SYMPTOMS
Fatigue
Dyspnoea on exertion
Peripheral edema
Other symptoms of heart failure

◦ PHYSICAL EXAMINATION
A relatively slender body build is typical.
A widely split and fixed S2 due to a delay in the closure of the pulmonary valve as a reflection of the
dilated pulmonary artery and prolonged RV emptying.
Grade 2 to 3/6 systolic ejection murmur are characteristic findings of ASD in older infants and children.
With a large left-to-right shunt, a mid-diastolic rumble resulting from relative tricuspid stenosis may be
audible at the lower left sternal border

◦ NATURAL HISTORY
Earlier reports have indicated that spontaneous closure of the secundum defect occurs in about 40% of patients in
the first 4 years of life. In patients with an ASD less 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 greater than
8 mm rarely closes spontaneously.
Most children with an ASD remain active and asymptomatic. Rarely, congestive heart failure (CHF) can develop in
infancy.
If a large defect is untreated, CHF and pulmonary hypertension develop in adults who are in their 20s and 30s.
With or without surgery, atrial arrhythmias (flutter or fibrillation) may occur in adults.
Infective endocarditis does not occur in patients with isolated ASDs.
Cerebrovascular accident, resulting from paradoxical embolization through an ASD, is a rare complication.

DIAGNOSTIC TESTS
◦ CHEST X-RAY
Cardiomegaly with enlargement of the RA and
RV may be present.
A prominent pulmonary artery (PA) segment
and increased pulmonary vascular markings are
seen when the shunt is significant.

DIAGNOSTIC TESTS

DIAGNOSTIC TESTS
◦ ECG
Most instances – sinus rhythm
A.Fib and Atrial Flutter – older age
Lower atrial rhythm (-ve P waves); in Sinus venosus ASD
RAE
Right axis deviation of +90 to +180 degrees
Mild right ventricular hypertrophy (RVH)
Right bundle branch block (RBBB) with an rsR' pattern in V1 are typical findings.
If LAD is found, then Primum ASD should be highly suspected
1 degree AV block – older patients secondary to interatrial delay

DIAGNOSTIC TESTS
◦ ECHOCARDIOGRAPHY
Goals :
◦ To identify and confirm ASD
◦ To identify associated anomaly
◦ To diagnose complications of ASD
◦ For therapeutic purpose
◦ 2D echo shows location, size of the defect
◦ If the dropout is seen at the mid-atrial level then it is SECUNDUM ASD
◦ If dropout at the lower atrial septum-PRIMUM ASD
◦ Defect in the posterosuperior atrial septum-SINUS VENOSUS ASD
◦ Defect in the wall that separates coronary sinus from LA- CORONARY SINUS ASD

DIAGNOSTIC TESTS
Apical 4 chamber
◦ Hemodynamic consequences like
RA/RV dilatation
◦ RV pressure
◦ Evaluation of R->L shunt

DIAGNOSTIC TESTS
Parasternal short axis (PSAX)
◦ Ideal to identify aortic rim
◦ Highlights posterior rim in sinus
venosus and posteroinferior
secundum ASD
◦ Shows dilatation of RV
◦ Volume overload of RV flattens IVS in
diastole

DIAGNOSTIC TESTS
Subcostal 4C view
◦ Viewed with breath held in
inspiration- index marker in 3 O clock
position
◦ Distinguishes OS, OP, SV ASD
◦ This view is ideal for SVC ASD
◦ Measurements of septum can be
taken
◦ Anomalous drainage of PVs
◦ Useful in patients with COPD and
ventilated patients

DIAGNOSTIC TESTS
Suprasternal short axis
◦ To visualize PV drainage into LA
Hemodynamics
◦ Indirect signs of L->R atrial shunt include RA/RV/PA enlargement which often accompanies increase in
flow velocity across PV
◦ Pulse doppler reveals characteristic flow pattern with max L-> R shunt occupying in diastole
1. L->R shunt begins in ventricular late systole.
2. Diminishes through mid diastole.
3. Enhanced by atrial contraction.
4. Reverses in early systole.

DIAGNOSTIC TESTS
◦ Qp/Qs
◦ Qp/Qs= 1 in normal
◦ Qp/Qs>1.5 significant shunt
◦ Qp=VTI,RVOT diameter
◦ Qs=VTI, LVOT diameter
𝑄𝑝
𝑄𝑠
=
𝑅𝑉𝑂𝑇 𝑑2 ∗ 0.785 ∗ 𝑅𝑉𝑂𝑇 𝑉𝑇𝐼
𝐿𝑉𝑂𝑇 𝑑2 ∗ 0.785 ∗ 𝐿𝑉𝑂𝑇 𝑉𝑇𝐼
ASD in Eisenmenger syndrome
◦ Pulmonary hypertension
◦ Reversal of flow
◦ Cyanosis KARISHMA SHAH RESHMA NAYAK CHELSEA REJI

DIAGNOSTIC TESTS
◦ CONTRAST
ECHOCARDIOGRAPHY
Apical 4 chamber view is
used
Agitated saline used – 5ml
in each 10ml syringe, o.5ml
of air taken in the syringe
and agitated to create
microbubbles

DIAGNOSTIC TESTS
TRANSESOPHAGIAL ECHO
◦ Gold standard
◦ Evaluation of number and location of defect, dimensions and adequacy of the rims
◦ It is used in individuals whom TTE acoustic window is suboptimal
◦ Guide trans catheter device closure
3D ECHO
◦ Clear image with spatial relationship to surrounding landmarks
◦ Used when attempting to close the multiple defects percutaneously

DIAGNOSTIC TESTS
CATH
◦ Pulmonary artery blood oxygen saturation is more than 80%, the possibility of left to
right intracardiac shunt should be considered.
◦ Oxygen saturation in PA, RA, RV, VC can be measured.
◦ Step up oxygen level in RA.
◦ In case of right to left shunt there will be step down oxygen level in LA.

MANAGEMENT
1. Medical
◦ Exercise restriction is unnecessary.
◦ In infants with CHF, medical management (with a diuretic) is
recommended because of its high success rate and the possibility of
spontaneous closure of the defect

MANAGEMENT
2. Nonsurgical Closure
◦ Nonsurgical closure using a catheter-delivered device closure has become a preferred method, provided
the indications are met.
◦ Several closure devices that can be delivered through cardiac catheters have been shown to be safe and
efficacious for secundum ASD closure.
Indication for device closure :
◦ Secundum ASD measuring 5mm or more in diameter (but less than 32 mm for Amplatzer device and
less than 18 mm for Helex device)
◦ A hemodynamically significant L-R shunt with clinical evidence of RV volume overload (i.e., Qp/Qs ratio
of 1.5:1 or greater or RV enlargement)
◦ There must be enough rim (4 mm) of septal tissue around the defect for appropriate placement of the
device

MANAGEMENT
◦ The rim size is estimated in four directions:
anterosuperior, anteroinferior, posterosuperior, and
posteroinferior.
◦ Two-dimensional echocardiographic estimates of the
ASD rim size: The posterosuperior (PS) and
posteroinferior (PI) rims are estimated in the bi–-vena
cava view from the subcostal transducer position, the
anteroinferior (AI) rim from the apical four-chamber
view, and the anterosuperior (AS) (or retro-aortic) rim
from the parasternal short-axis view

MANAGEMENT
◦ Indication for infants:
Considering the possibility of spontaneous closure, it is wise not to use the device in infancy unless the
patient is symptomatic with heart failure.
ASD closure devices can be implanted successfully in children younger than 2 years of age.
◦ Advantages of nonsurgical closure
Complete avoidance of cardiopulmonary bypass with its attendant risk
Avoidance of pain and residual thoracotomy scars
 A less than 24-hour hospital stay
 Rapid recovery

MANAGEMENT
◦ Complications / Disadvantages
Early ECG abnormalities are common within the first 24 hours after implant
Early or late erosion of the device into the aortic root (Amplatzer device)
Thrombus formation in the right and left atrium occurs (Rarely)
Higher rate of small residual leak
◦ Postdevice Closure Follow-up
The patients are prescribed aspirin- 81 mg per day for 6 months.
 Post-procedure 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.

MANAGEMENT
3. Surgical Closure
◦ Indications and Timing
Surgical closure is indicated only when device closure is not considered appropriate.
Therefore, most patients with secundum ASD are not candidates for surgical closure of the defect.
A left-to-right shunt with a pulmonary-to-systemic blood flow ratio (Qp/Qs ratio of 1.5:1 or greater) is a
surgical indication.
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, again if device
closure is considered inappropriate.
High pulmonary vascular resistance (PVR) (i.e., >10 units/m2, >7 units/m2 with vasodilators) may be a
contraindication for surgery (or device closure).

MANAGEMENT
◦ Procedure
For secundum ASD, the defect is traditionally repaired through a midsternal incision under
cardiopulmonary bypass by either a simple suture or a pericardial or Teflon patch.
For a sinus venosus defect without associated anomalous pulmonary venous return, the defect is
closed using an autologous pericardial patch.
When it is associated with pulmonary venous anomaly, a tunnel is created between the anomalous
pulmonary vein and the ASD by using a Teflon or pericardial patch.
For coronary sinus ASD, the ostium of the coronary sinus is closed with an autologous pericardium with
care to avoid conduction tissues, provided it is not associated with persistent left SVC. This will result in
drainage of coronary sinus blood into the left atrium.

MANAGEMENT
PERICARDIAL PATCH NORMAL PATCH

MANAGEMENT
◦ Complications
Cerebrovascular accident and postoperative arrhythmias may develop in the immediate
postoperative period.
◦ Mortality
Fewer than 0.5% of patients die
however, there is a greater risk for small infants and those with increased PVR.
◦ 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.

Atrial septal defect (ASD)

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