Chapter 12: CHD: Left to Right Shunt

Question 1

The most commonly encountered left-to-right shunts include :

Answer 1

• ASDs,
• VSDs,
• patent ductus arteriosus ( PDA), and
• atrioventricular septal defects,

Un merong mga D!

Question 2

Answer 2

FIGURE 12-4 Schematic of congenital left-to-right shunts. Arrows indicate the direction of
blood flow.

• A, Atrial septal defect (ASD).
• B, Ventricular septal defect (VSD). With VSD the shunt is left-to-right, and the pressures are the same in both ventricles. Pressure hypertrophy of the right ventricle and volume hypertrophy of the left ventricle are generally present.
• C, Patent ductus arteriosus (PDA).
• D, Atrioventricular septal defect (AVSD).
• E, Large VSD with irreversible pulmonary hypertension. The shunt is right-to-left (shunt reversal). Volume hypertrophy and pressure hypertrophy of the right ventricle are present. The right ventricular pressure is now sufficient to yield a right-to-left shunt. Ao, aorta; LA, left
• atrium; LV, left ventricle; PT, pulmonary trunk; RA, right atrium; RV, right ventricle.

Question 3

What is ASD?

Answer 3

An atrial septal defect (ASD) is an abnormal, fixed opening in the atrial septum caused by
incomplete tissue formation that allows communication of blood between the left and right atria
(not to be confused with patent foramen ovale,see below

Question 4

ASDs are usually symptomatic until
adulthood

T or F

Answer 4

FALSE

ASDs are usually asymptomatic until
adulthood

Question 5

What are the three major types of ASDS?

Answer 5

The three major types of ASDs are classified according to their location as :

• secundum,
• primum, and
• sinus venosus.

Question 6

What is the most common type of ASD?​

Answer 6

SECUNDUM

” Madalas ang heart ng BOYS kumukuha ng PANGALAWA”

Question 7

What is secundum ASD?

Answer 7

Secundum ASDs (90% of all ASDs) result from a

deficient or fenestrated oval fossa near the center of the atrial septum.

These are usually
not associated with other anomalies, and may be of any size, be single or multiple, or be
fenestrated.

Question 8

What is Primum ASD?

Answer 8

Primum anomalies (5% of ASDs)

occur adjacent to the AV valvese.

Primum meaning mas mataas ang loca kesa sa secundum!

Question 9

What is Sinus venosus defects?

Answer 9

Sinus
venosus defects (5%) are **located near the entrance of the superior vena cava** and **may be** **associated with anomalous pulmonary venous return to the right atrium**

” Kaya nga dba Venosus kase malapit sa SVC”

Question 10

ASDs result in a left-to-right shunt largey because of what?

Answer 10

• *pulmonary vascular resistance is considerably less than systemic vascular resistance and because the compliance (distensibility)**
• of the right ventricle is much greater than that of the left*.

Question 11

What are the clinical features of ASD?

Answer 11

• Pulmonary blood flow may be two to four times normal.
• A murmur is often present as a result of excessive flow through the pulmonary valve
• . Despite the right-sided volume overload, ASDs are generally well tolerated and usually do not become symptomatic before age 30;
• irreversible pulmonary hypertension is unusual.

Question 12

What reverses the hemodynamic abnormalities of ASDs?

Answer 12

Surgical or catheter-based closure of an ASD reverses the hemodynamic
abnormalities and prevents complications, including heart failure, paradoxical embolization, and
irreversible pulmonary vascular disease. [36]

Mortality is low, and long-term survival is
comparable to that of a normal population.

Question 13

What is patent foramen ovale?

Answer 13

A patent foramen ovale is a small hole created by an open flap of tissue in the atrial septum at
the oval fossa. [37]

Question 14

In the fetus, the foramen ovale is an important functional right-to-left shunt
that allows oxygen-rich blood from the placenta to bypass the not yet inflated lungs by traveling
directly from the right to left atrium.

T or F

Answer 14

True

Question 15

How is the foramen ovale in fetus forced to be closed?

Answer 15

The hole is forced shut at birth as a result of increased
blood pressure on the left side of the heart,and thetissue flap closes permanently in
approximately 80% of people.

In the remaining 20% of people, the unsealed flap can open when there is more pressure on the right side of the heart.

Thus, sustained pulmonary
hypertension or even transient increases in right-sided pressures, such as occurs during a
bowel movement, coughing, or sneezing, can produce brief periods of right-to-left shunting, with
the possibility of paradoxical embolism.

Question 17

What is VSD?

Answer 17

Incomplete closure of the ventricular septum, allowing free communication of blood between the
left to right ventricles,is themost common form of congenital cardiac anomaly ( Fig. 12-4B ).

Question 18

What is the most common form of Congenital cardiac anomaly?

Answer 18

VSD

Question 19

Most ventricular septal defects (VSDs) are associated with other congenital cardiac anomalies
such as _______; only 20% to 30% are isolated

Answer 19

tetralogy of Fallot

Question 20

VSDs are classified according to what?

Answer 20

VSDs are classified according to their :

size and location.

Most are about the
size of the aortic valve orifice.

Question 21

What is the most common type of VSD?

Answer 21

About 90% involve the region of the membranous
interventricular septum (membranous VSD) ( Fig. 12-5 ).

The remainde**r lie below the
pulmonary valve (infundibular VSD)** or within the muscular septum.

Although most VSDs are
single, those in the muscular septum may be multiple (so-called “Swiss-cheese” septum).

Question 22

What are the types of VSD ?

Answer 22

• Membranous
• infundibular
• muscular septum

Question 23

What is the Swiss-cheese” septum?

Answer 23

. Although most VSDs are
single, those in the muscular septum may be multiple (so-called “Swiss-cheese” septum).

Question 24

Answer 24

FIGURE 12-5 A ventricular septal defect (membranous type), denoted by the arrow.

Question 25

The functional consequences of a VSD depend on what?

Answer 25

The functional consequences of a VSD depend on the size of the defect and whether there are
associated with right-sided malformations.

Question 26

Which are more tolerated small or large VSD?

Answer 26

Large VSDs cause difficulties virtually from birth;

smaller lesions are generally well tolerated for years, and may not be recognized until much
later in life

Question 27

Approximately 50% of small muscular VSDs close spontaneously.

T or F

Answer 27

True

Question 28

Large Defects are usually of what type?

Answer 28

Large defects
are usually membranous or infundibular, and they generally cause significant left-to-right
shunting, leading to right ventricular hypertrophy and pulmonary hypertension virtually from
birth.

Question 29

Over time what happens in patients with VSDs?

Answer 29

Over time, irreversible pulmonary vascular disease develops in essentially all persons with
large unclosed VSDs, ultimately resulting in shunt reversal, cyanosis, and death.

Question 30

Surgical or
catheter-based closure of asymptomatic VSDs is generally delayed beyond infancy, in hope of
spontaneous closure.

Early correction, however, must be performed in babies with large defects
to prevent the development of irreversible obstructive pulmonary vascular disease.

Question 31

What is PDA?

Answer 31

Patent (also called persistent) ductus arteriosus (PDA) results when the ductus arteriosus, an
essential fetal structure that normally spontaneously closes, remains open after birth (see Fig.
12-4C ).

Question 32

In fetal circulation, where does ductus arteriosus shunts blood ?

Answer 32

In the fetal circulation the ductus arteriosus shunts blood from the pulmonary artery to the aorta, which (like the patent foramen ovale) serves to bypass the lungs.

Question 33

About 90% of PDAs occus as ?

Answer 33

About 90% of PDAs
occur as an isolated anomaly.

The remainder are most often associated with VS D, coarctation
of the aorta, or pulmonary or aortic valve stenosis.

Question 34

What is the characteristic sound the PDA produces?

Answer 34

PDA produces a characteristic continuous harsh murmur, described as “machinery-like”.

“Kissing in PDA makes a machinery sound! “

Question 35

Where does the clinical impact of PDA depends on?

Answer 35

The
clinical impact of a PDA depends on its diameter and the cardiovascular status of the
individual. [40]

Question 36

How is PDA in patients at birth?

Answer 36

PDA is usually asymptomatic at birth, and a narrow PDA may have no effect on
the child’s growth and development.

Because the shunt is at first left-to-right, there is no
cyanosis, but eventually the additional volume and pressure overload produce obstructive
changes in small pulmonary arteries, leading to reversal of flow and its associated
consequences.

Question 37

T or F

A narrow PDA may have an effect on the child’s growth and development?

Answer 37

FALSE

PDA is usually asymptomatic at birth, and a narrow PDA may have no effect on
the child’s growth and development.

Because the shunt is at first left-to-right, there is no
cyanosis, but eventually the additional volume and pressure overload produce obstructive
changes in small pulmonary arteries, leading to reversal of flow and its associated
consequences.

Question 38

What is the reason that PDA is usually asymptomatic at birth?

Answer 38

Because the shunt is at first left-to-right, there is no
cyanosis, but eventually the additional volume and pressure overload produce obstructive
changes in small pulmonary arteries, leading to reversal of flow and its associated
consequences.

Question 39

There is general agreement that an isolated PDA should not be closed as early in life as is feasible.

T or F

Answer 39

FALSE

There is general agreement that an isolated PDA should be closed as early in life as is feasible.

Question 40

What is administer in the patency of ductus when it is needed to be preserved?

Answer 40

.
Conversely, preservation of ductal patency (by administering prostaglandin E) assumes great
importance in the survival of infants with various congenital malformations that obstruct the
pulmonary or systemic outflow tracts.

For example, in aortic valve atresia a PDA provides thebulk of the systemic blood flow.

Depending on the context, therefore, a PDA may be either lifethreatening
or lifesaving

Question 41

There is general agreement that an isolated PDA should be closed as early in life as is feasible.

Answer 41

Kasi in some PDA with other congenital anomalies, patency of this helps in the provision the
bulk of the systemic blood flow

For example, in aortic valve atresia a PDA provides the bulk of the systemic blood flow.

Depending on the context, therefore, a PDA may be either lifethreatening or lifesaving.

Question 42

What is Atrioventricular Septal Defect?

Answer 42

Atrioventricular septal defect (AVSD, also called complete atrioventricular canal defect) results
from the embryologic failure of the superior and inferior endocardial cushions of the AV canal to
fuse adequately.

The consequence is incomplete closure of the AV septum and malformation of
the tricuspid and mitral valves (see Fig. 12-4D).

Question 43

What are the tho most common forms of AVSD?

Answer 43

• partial
• complete

Question 44

What is partial AVSD?

Answer 44

The two most common forms are consisting of a primum ASD and a cleft anterior mitral leaflet, causing mitral insufficiency

Question 45

What is complete AVSD?

Answer 45

complete AVSD (**consisting of a large combined AV** **septal defect** and a **large common AV valve**
—essentially a **hole in the center of the heart**).

In the complete form, all four cardiac chambers
freely communicate, inducingvolume hypertrophy of each.

Question 46

What Left to Right shunt congenital anomaly is associated with Down’s syndrome?

Answer 46

More than one third of all patients
with a complete AVSD have Down syndrome.

Surgical repair is possible.