Congenital heart disease, also called a defect, refers to one or more problems with the heart structure that are present at birth. These abnormalities occur when the heart or blood vessels don't form correctly in utero. At least eight out of every 1000 infants born in the US each year have a heart defect.

4.  For thousands of years, the heart has been considered one of the most
important organs in the body. Aristotle even believed that other organs
existed just to cool it, including the brain and lungs (which we now
know perform their own vital functions). Although it may not be
exactly as Aristotle once thought, the heart does perform a role that is
absolutely necessary for survival.
 The heart is the first organ to form and become functional,
emphasizing the importance of transport of material to and from the
developing infant. It originates about day 18 or 19 from the
mesoderm and begins beating and pumping blood about day 21 or 22.
It forms from the cardiogenic region near the head and is visible as a
prominent heart bulge on the surface of the embryo. Originally, it
consists of a pair of strands called cardiogenic cords that quickly
form a hollow lumen and are referred to as endocardial tubes. These
then fuse into a single heart tube and differentiate into the truncus
arteriosus, bulbus cordis, primitive ventricle, primitive atrium, and
sinus venosus, starting about day 22. The primitive heart begins to
form an S shape within the pericardium between days 23 and 28.

5.  The internal septa begin to form about day
28, separating the heart into the atria and
ventricles, although the foramen ovale
persists until shortly after birth. Between
weeks five and eight, the atrioventricular
valves form. The atrioventricular valves form.
The semilunar valves form between weeks
five and nine.

7.  Schematic representation of the formation of the adult heart. With the onset of
embryonic folding the left and right heart forming region (HFR). The yellow
structures represent the endocardial cells (endo) that form the inner lining of the
heart and in gray the formed primary myocardium.
 VP refers to the venous pole were the blood will enter the heart and AP to the
arterial pole where the blood will leave the heart. For easy comparison of panels
(a) through (d), a red line indicates the lateral border of the HFR and a blue line the
medial border. With ongoing folding the HFR becomes positioned ventrally of the
foregut (see also Figure 1).
 At the position where the lateral borders of the HFR meet, the linear heart tube is
connected to the body wall via the dorsal mesocardium (dm) (panel d). The DM
breaks due to which the heart is only attached to the body wall at the AP and VP
(panel h–k). Whereas panels (a)–(d) show a dorsal view of the forming heart,
panels (e)–(h) show a ventral view, illustrating the transition of linear heart tube to
four-chambered heart.
 Only at the ventral site of the linear heart tube the differentiation of the embryonic
ventricle (V) is locally initiated.

8.  The forming working myocardium of the chambers is indicated in blue (panels f–k). Note in
panel (g) that at the dorsal side of the heart tube, primary myocardium is retained, which is
referred to as the inner curvature (IC). Flanking the forming ventricle, primary myocardium is
retained which is referred to as the inflow tract (IFT) and outflow tract (OFT). With ongoing
development, the linear heart tube loops to the right and chamber formation becomes evident
(panel h).
 At this stage the right ventricle (RV) starts to form when primary myocardium of the OFT
differentiates into chamber myocardium. Moreover, upstream of the left ventricle (LV), the
primary myocardium of the IFT locally differentiates into the left atrium (LA) and right
atrium (RA). In the meantime, newly differentiated cardiomyocytes are added to the
lengthening heart forming the sinus venous (SV) myocardium. The heart is connected to the
blood circulation at the VP via the left and right cardinal vein (cv) and at the AP via the
pharyngeal arch arteries (paa).
 Panel (j) shows a representation of the 5 week old human heart showing the expanding
(ballooning) atria and ventricles, as well as the remnants of the primary myocardium of the
IFT, AVC (atrioventricular canal), IC and OFT. The forming primary atrial septum (pAS) and
ventricular septum (VS) are identified. Within the LA the attachment to the body wall is
identified as the mediastinal mesenchyme (mm) through which the cardinal vein (cv) and the
future pulmonary vein (pv) drain into the heart. In the formed heart (panel k) the primary
myocardium of the IFT and AVC has differentiated into the central conduction system,
comprising the sinoatrial node (sn), the atrioventricular node (avn), the His bundle (His) and
the bundle branches (bb). Within the right atrium the superior and inferior caval veins (scv
and icv) drain in the RA and the pulmonary veins (pv) in the LA. Flanking the chambers,
valves are formed of which only the mitral valve (mv) and the tricuspid valve (tv) are shown.

9.  In the healthy normal post-natal heart, oxygen-rich blood enters the left
atrium, is propagated to the left ventricle and then pumped via the aorta into
the systemic circulation. The oxygen-deprived blood, returning from the body,
enters the right atrium and is propelled by the right ventricle via the
pulmonary trunk toward the lungs.
 The cardiac conduction system orchestrates the efficient contraction-relaxation
cycle of the atria and ventricles. The electrical impulse resulting in cardiac
contraction is triggered in the sinus node, which is located at the entrance of
the superior caval vein into the right atrium.
 The electrical impulse spreads through both atria, but cannot directly activate
the ventricles due to the electrical isolation of the atria from the ventricles by
the annulus fibrosus (also called insulating plane or fibrous continuity). The
electrical impulse is delayed in the atrioventricular (AV) node, and then
quickly propagated through the His-bundle (AV-bundle), which penetrates the
insulating annulus fibrosis plane, via the bundle branches and the peripheral
conduction system (the Purkinje fibers) to the cardiomyocytes.
 The coordinated propagation of the electrical impulse ensures the
synchronous contraction of the ventricles from the apex toward the aorta and
pulmonary trunk.

10. PROCESS
 FORMATION AND GROWTH OF THE LINEAR HEART TUBE
 THE GROWTH AND LOOPING OF THE HEART TUBE
 FROM LINEAR TO FOUR CHAMBERED HEART
 DEVELOPMENT OF THE CONDUCTION SYSTEM
 THE SINUS NODE
 ATRIOVENTRICULAR NODE AND BUNDLE BRANCHES
 PERIPHERAL VENTRICULAR CONDUCTION SYSTEM
 SEPTATION

12.  Schematic representation of septation. Panel (a) shows the same
schematic drawing of the four chamber-forming heart as Figure 2(j), in
which now the major cushions have been added within the
atrioventricular canal (AVC) and outflow tract (OFT) and the left and
right bloodstreams through the heart is indicated. The ventricular
foramen is located between the distal edge of the ventricular septum (VS)
and the inner curvature (IC).
 Noteworthy is that the left bloodstream passes the ventricular foramen
during systole, while the right bloodstream already passes through the
ventricular foramen during diastole. Panels (b)–(f) illustrate atrial
septation and show the cutting edge (sagittal sections) at the level of the
dashed line in panel (a). For easy comparison the cushions are numbered.
The mesenchymal complex formed by the anterior (1) and posterior (2)
atrioventricular cushion, the extension of the anterior cushion over the
roof of the atrium (MC), and the extracardiac mesenchyme that protrudes
into atrial lumen (DMP), surround the connection between the left (LA)
and right atrium (RA).
 With expansion of this complex the primary atrial foramen (pAF)
becomes smaller and eventually closes forming the primary atrial septum
(pAS). Prior to closure of the pAF, the secondary atrial foramen (sAS) is
formed. Within the RA the secondary atrial septum (sAS) folds down
from the atrial wall into the lumen and covers the pAS partly and the pAF
completely. The uncovered part of the pAS is recognized as the oval
fossa (OF)

13. PROCESS
CONTINUE
 ATRIAL SEPTATION
 VENTRICULAR SEPTATION
 SEPTATION OF THE OUTFLOW TRACT
 THE CARDIAC CONNECTIVE TISSUES
 EPICARDIUM AND ITS DERIVATIVES
 DEVELOPMENT OF THE VALVES
 REMODELING OF THE EMBRYONIC VALVES

23.  Development of the heart begins in the third
week with the formation of two endothelial
strands called the angioblastic cords. These
cords canalize forming two heart tubes,
which fuse into single heart tube by the end
of the third week due to lateral embryonic
folding. By the fourth week, the developing
heart receives blood from three pairs of
veins: the vitelline veins, umbilical veins, and
common cardinal veins.
 The vitelline veins carry poorly oxygenated
blood from the yolk sac, and enter the sinus
venosus;
 The umbilical veins carry oxygenated blood
from the chorion, the primordial placenta;
and the common cardinal veins carry poorly
oxygenated blood from the rest of the
embryo.

24.  As the primordial liver develops in close association
with the septum transversum, the hepatic cords join
and surround epithelial-lined spaces, forming the
primordial hepatic sinusoids.
 These primordial sinusoids become connected to the
vitelline veins. Vitelline veins pass through the septum
transversum and enter sinus venosus, also called as
venous end of the heart.
 Left vitelline veins regress while right vitelline veins
form the hepatic veins, and a network of vitelline veins
around the duodenum form the portal vein.

25. As the development of liver progresses, umbilical veins lose connection with
heart and empty into liver. The right umbilical vein and cranial part of the left
umbilical vein degenerate during seventh week of gestation, leaving only the
caudal part of the left umbilical vein. The caudal part of the left umbilical vein
carries oxygenated blood to the embryo from the placenta. The umbilical vein is
connected to the inferior vena cava (IVC) via the ductus venosus, a venous shunt
that develops in the liver. This bypass directs most of the blood directly to the
heart from placenta without passing through liver.

26.  Umbilical vein (ventral view)
 The embryo is drained primarily by the cardinal veins, with
the anterior cardinal vein draining the cranial part of the
embryo and the posterior cardinal vein draining the caudal
part. These two join to form the common cardinal vein, which
enters the sinus venosus.
 By the eighth week, the anterior cardinal veins are connected
by a vessel running obliquely between them. This oblique
vessel allows for the shunting blood from the left anterior
cardinal vein to the right. Once the caudal part of the left
anterior cardinal vein degenerates, this oblique anastomotic
vessel becomes the left brachiocephalic vein. The right
anterior cardinal vein and right common cardinal vein
eventually become the superior vena cava (SVC), and the
posterior cardinal veins contribute to the common iliac
veins and the azygos vein.

27.  As the subcardinal and supracardinal veins form, they first supplement
but soon replace the posterior cardinal veins. The subcardinal
veins appear first, and eventually form parts of the left renal vein,
suprarenal vein, gonadal vein, and inferior vena cava (IVC). Above
the kidneys, anastomoses join the supracardinal veins, forming the
azygos and hemiazygos veins. Below the kidneys, the right
supracardinal vein contributes to IVC, while the left supracardinal vein
degenerates.
 In the fourth and fifth weeks of development, the pharyngeal
arches form. These are supplied by the pharyngeal arch arteries, which
connect the aortic sac to the two dorsal aortae. The dorsal
aortae extend the length of the embryo, eventually fusing in the caudal
part of the embryo to form the lower thoracic/abdominal aorta. The
rest of the right dorsal aorta degenerates, while the remainder of the
left dorsal aorta becomes the primordial aorta.

28.  The dorsal aortae give off the intersegmental arteries, which supply the
somites and their derivatives. These intersegmental arteries become
the vertebral arteries in the neck region, the intercostal arteries in
the thorax, the lumbar arteries and common iliac arteries in
the abdomen, and the lateral sacral arteries in the sacral region. The very
caudal end of the dorsal aorta gives rise to the median sacral artery, and
any other intersegmental arteries regress.
 The umbilical vesicle (i.e. yolk sac), allantois, and chorion are supplied
by unpaired branches of the dorsal aorta. The umbilical vesicle is
supplied by the vitelline arteries, and once part of the umbilical vesicle
forms the primordial gut, this region is supplied by the vitelline arteries
as well. The vitelline arteries give rise to the celiac artery, which
supplies the foregut; the superior mesenteric artery, which supplies the
midgut; and the inferior mesenteric artery, which supplies the hindgut

29.  The two umbilical arteries, contained within the umbilical cord, carry
poorly oxygenated blood from the embryo to the placenta.
The proximal part of these arteries become the internal iliac
and superior vesical arteries, while the distal parts regress and become
the medial umbilical ligaments.
 Heart layers
 As the heart tubes fuse, the primordial myocardium begins to form
from the splanchnic mesoderm around the pericardial cavity. This
primordial myocardium becomes the middle, muscular layer of the
heart. Separated from the primordial myocardium by gelatinous tissue
called cardiac jelly, the heart begins to develop as a thin tube. This
endothelial tube becomes the endocardium, the innermost layer of the
heart. Epicardium, the outermost layer, originates from mesothelial
cells from the outer surface of the sinus venosus.

30.  Heart tube
 As the cranial part of the embryo folds, the heart tube elongates.
As it elongates, the heart tube develops alternating constrictions
and expansions, forming the bulbus cordis, ventricle, atrium, and
sinus venosus. The bulbus cordis has multiple components,
including the truncus arteriosus, conus arteriosus, and conus
cordis. The truncus arteriosus is cranial to the aortic sac, to which
it is connected, and gives off the pharyngeal arch arteries.
 Blood leaves the heart via the pharyngeal arch arteries, and returns
to the sinus venosus of the heart via the umbilical, vitelline, and
common cardinal veins. The bulbus cordis and ventricles grow at
a faster rate than other parts of the developing heart, and because
of this the heart bends and folds in on itself, forming the bulbo-
ventricular loop.
 As this bending occurs, the atrium and sinus venosus move so that
they are dorsal to the truncus arteriosus, bulbus cordis, and
ventricle. During this time, the sinus venosus also develops lateral
extensions, the left and right horns.

31.  The heart is initially attached to the dorsal wall of the pericardial
cavity by a mesentery called the dorsal mesocardium, but as the
heart grows it begins to fill the pericardial cavity and the central
part of the dorsal mesocardium degenerates. The loss of part of
this mesentery allows a communication to form between the left
and right sides of the pericardial cavity, the transverse pericardial
sinus.
 Primitive circulation
 The sinus venosus receives blood from the common cardinal
veins, umbilical veins and vitelline veins. The common cardinal
veins carry blood from the embryo; the umbilical veins carry
blood from the placenta; and the vitelline veins carry blood from
the umbilical vesicle.

32.  After entering the sinus venosus, blood flows through
the sinuatrial valves into the primordial atrium. It then
flows from the primordial atrium into the primordial
ventricle via the atrioventricular (AV) canal.
 When the primordial ventricle contracts, it pumps
blood into the bulbus cordis and through the truncus
arteriosus, into the aortic sac. From there, blood enters
the pharyngeal arch arteries, and then the dorsal aortae,
which allows it to travel back to the embryo, placenta,
and umbilical vesicle.

39.  Partitioning of the developing heart : In the middle of the fourth week,
the atrioventricular canal, primordial atrium and ventricle start to partition, and this
process is completed by the end of week eight. It begins with the formation of
the endocardial cushions, specialized extracellular matrix tissue related to myocardial
tissue. At the end of the fourth week, these cushions appear on the ventral and dorsal
walls of the AV canal and start to grow toward each other. They eventually fuse,
separating the AV canal into left and right components, partially separating the atrium
and ventricle and acting as AV valves.
 The primordial atrium becomes separated into the right and left atria by two septa, the
septum primum and septum secundum. The septum primum appears first in the form of a
thin membrane, growing out of the roof of the primordial atrium toward the endocardial
cushions, leaving an opening between its edge and endocardial cushion. This opening is
called the foramen primum, and it allows blood to continue to be shunted from the right
atrium to the left. It progressively shrinks and eventually closes as the septum primum
elongates and fuses with the endocardial cushions, forming the primordial AV septum.
Before the foramen primum closes completely, however, apoptosis of cells in the middle
of the septum primum forms perforations in the septum.
 These perforations form a new second opening, the foramen secundum, which allows
oxygenated blood to continue to flow from the right atrium to the left even after the
foramen primum has closed.

40.  The muscular septum, the septum secundum, grows immediately adjacent to
the septum primum, just to its right. It grows downward from the ventro-
cranial wall of the atrium during the fifth and sixth weeks of development,
gradually overlapping the foramen secundum in the septum primum. By
overlapping the foramen secundum without fusing to the septum primum, an
incomplete barrier between the atria is formed.
 At this point in development, the opening between the atria is called
the foramen ovale, and it allows oxygenated blood to continue to flow from
the right atrium, under the flap of the septum secundum, through the
foramen secundum, and into the left atrium. This arrangement also prevents
blood from flowing in the opposite direction, from the left atrium to the
right atrium: the thin septum primum gets pressed up against the more firm
and inflexible septum secundum, blocking blood from flowing through the
foramen ovale.
 Although the cranial part of the septum primum slowly regresses, some
parts of the septum primum remain attached to the endocardial cushions.
These residual parts of the septum primum form the valve of the foramen
ovale.

41.  Valve of foramen ovale (lateral-left view)
 After a baby is born, the pressure in the left atrium increases significantly,
becoming much higher than the pressure in the right atrium. This causes the
septum primum to be pushed against the septum secundum and the valves of
the foramen primum to fuse with the septum secundum, functionally closing
the foramen ovale. When this occurs, the foramen ovale becomes the fossa
ovalis and the two septae form a complete barrier between the atria.
 Sinus venosus: The sinuatrial orifice, the opening of the sinus venosus into the
single primordial atrium, is initially located in the posterior wall of the
primordial atrium. This changes, however, at the end of the fourth week, when
the right sinual horn grows larger than the left. This unequal growth moves the
sinuatrial orifice to the right, shifting it into what will become the adult right
atrium. As the right sinual horn continues to grow, blood from the head and
neck region of the embryo flows into it via the SVC, and blood from the
placenta and the rest of the body of the embryo flows into it via the IVC.

42.  As the heart continues to develop, the sinus venosus gets integrated
into the wall of the right atrium as the smooth part of the internal
surface of the right atrium, the sinus venarum. The rest of the internal
surface of the right atrium and auricle has a thicker, trabeculated
appearance; these parts of the adult atrium originate from the
primordial atrium. The transition from the smooth to the rough internal
surface of the right atrium is demarcated on the inside of the atrium by
a ridge called the crista terminalis, which originates from the cranial
part of the right sinuatrial valve, and on the outside by a groove called
the sulcus terminalis. The caudal part of the right sinuatrial valve
forms the valves of the IVC and coronary sinus.
 The left sinual horn develops into the coronary sinus; and the left
sinuatrial valve eventually fuses with the septum secundum, becoming
part of the interatrial septum.

43.  Interatrial septum
 Primary pulmonary vein: The majority of the inner wall of the left atrium is
smooth and is derived from the primordial pulmonary vein, which develops
from the dorsal atrial wall just left of the septum primum. As the left atrium
grows, the primordial pulmonary vein, as well as its main branches, become
integrated into the atrial wall. This results in four pulmonary veins entering
into the left atrium. The left auricle has the same origin as the right auricle:
the primordial atrium. As such, its internal surface is trabeculated.
 Ventricles: The primordial ventricle begins its division into two ventricles
with the growth of the median ridge, a muscular interventricular (IV)
septum with a superior free edge that arises from the floor of the primordial
ventricle, close to the apex of the heart. Dilation of the developing ventricles
on either side of this septum is responsible for the initial increase in the
septal height, with additional growth occurring due to the contribution of
ventricular myocytes from both sides of the heart.

58.  Between the upper free edge of this septum and the endocardial cushions, there
remains an opening called the IV foramen. This foramen allows blood to
continue to flow between the right and left ventricles until its closure at the end
of the seventh week, when the left and right bulbar ridges fuse with the
endocardial cushion, forming the membranous part of the IV septum. The bulbar
ridges form in the fifth week as proliferations of mesenchymal neural crest cells
in the walls of the bulbus cordis.
 The membranous part of the IV septum results when tissue from the right side of
the endocardial cushion extends to the muscular part of the IV septum, ultimately
merging with the aorticopulmonary septum and muscular IV septum. Once the
IV foramen closes and the membranous part of the IV septum forms, the aorta
becomes the sole outflow tract of the left ventricle, and the pulmonary trunk
becomes the sole outflow tract of the right ventricle.
 As the ventricles continue to develop, cavitation results in the formation of
muscular bundles. While some of these persist as trabeculae carneae (irregular
columns of muscle on the inner surface of the ventricles), others form the
papillary muscles and chordae tendinae (heart strings), which connect the
papillary muscles to the AV valves.

59.  Cardiac valves: The aortic and
pulmonic semilunar valves each develop from
three swellings of subendocardial tissue present
around the opening of aorta and pulmonary
trunk. They evolve into three thin cusps.
 Anterior cusp of mitral valve (cranial view):
The tricuspid and mitral AV valves form from
proliferations of tissue surrounding the AV
canals. The tricuspid valve develops three cusps,
whereas the mitral (i.e. bicuspid) valve develops
two.

62.  Conducting system: Heart conductive system
 Initially, the primordial atrium functions as the developing heart’s
pacemaker; but the sinus venosus soon takes over this role. In the
fifth week, the sinuatrial (SA) node develops in the right atrium
near the opening of the SVC. After the sinus venosus is integrated
into the heart, cells from its left wall can be found near the
opening of the coronary sinus, at the base of the interatrial
septum. With the addition of some cells from the AV region,
the AV node and bundle are formed just above the endocardial
cushions. Fibes originating from the AV bundle project from the
atrium into the ventricle and divide into left and right bundle
branches, which can be found throughout the ventricular
myocardium. Although the SA node, AV node, and AV bundle
eventually receive nervous innervation from outside the heart, the
primordial conducting system develops before this occurs.

69.  The majority of congenital developmental anomalies of the heart
are present 6 weeks after conception.Congenital heart disease can
be cyanotic or acyanotic.
 There are three types of congenital heart disease
 Grade 1 - Left to Right shunts
 Grade 2 - Right to Left shunts
 Grade 3 - Obsructive lesions
 Clinical features of LEFT to RIGHT shunts(acyanotic heart disease)
 Frequent chest infections are seen (6-8 attacks first year of life)
 Tendency for increased sweating that is related to their tendency for developing
Congestive cardiac failure
 Precordial bulge is seen.
 Hyperkinetic precordium occur.
 Tricuspid /mitral mid diastolic murmur is heard.
 X-ray show plethoric lung field + cardiomegaly.
 Example are VSD,ASD, PDA,AV canal defect

71. CYANOTIC
CONGENITAL
HEART
DISEASE

73.  Cyanotic Congenital Heart Defects
 Cyanotic heart defects are cardiac defects in
which the blood pumped to the rest of the
body contains less than normal amounts of
oxygen.
 In other words, the heart pumps mixed
oxygen-poor and oxygen-rich blood to the
body.
 This can lead to cyanosis which is a bluish
discoloration of the skin.
 Cyanotic heart defects typically contain right-
to-left shunts, meaning deoxygenated blood
from the right heart is shunted to the left
heart.
 As a result, oxygen-poor blood is delivered
to the body and can cause cyanosis.

81. ECG

90.  Echocardiography
 Cardiac catheterization

91.  The treatment of choice for most congenital heart diseases
is surgery to repair the defect. There are many types of
surgery, depending on the kind of birth defect. Surgery may
be needed soon after birth, or it may be delayed for months or
even years. Some surgeries may be staged as the child grows.
 Your child may need to take water pills (diuretics) and other
heart medicines before or after surgery. Be sure to follow the
correct dosage. Regular follow-up with the provider is
important.
 Many children who have had heart surgery must take
antibiotics before, and sometimes after having any dental
work or other medical procedures. Make sure you have clear
instructions from your child's heart provider.
 Ask your child's provider before getting any immunizations.
Most children can follow the recommended guidelines for
childhood vaccinations

95. 1. Truncus Arteriosus : Trick: Hold up 1 finger
 Truncus Arteriosus: One great vessel leaving the heart, instead of 2
 The first cyanotic congenital heart defect is truncus arteriosus.
 You can hold up 1 finger to remember this.
 Truncus arteriosus is when one blood vessel leaves the heart instead of
2.
 You might remember from the anatomy of the heart lecture that
normally there are 2 main arteries leaving the heart.
 The main pulmonary artery leaves the right side of the heart and
delivers deoxygenated blood to the lungs.
 The aorta leaves the left side of the heart and delivers oxygenated blood
to the rest of the body.

96.  In the case of truncus arteriosus, the great vessel
coming out of the heart fails to divide during
development.
 This leaves a connection between the aorta and
pulmonary artery.
 A ventricular septal defect (VSD) is typically
present, and the blood from the right and left
ventricle combine and exit the heart through one
great vessel.
 A VSD is a hole in the wall between the right and
left ventricle.
 As a result, oxygen-poor blood from the right
heart and oxygen-rich blood from the left heart
are delivered to the rest of the body.
 This can lead to potential cyanosis.
 So again, use 1 finger to remember truncus
arteriosus and one great vessel leaving the heart.

98. Truncus Arteriosus: Hold up 1 finger to remember one great
vessel leaves the heart, instead of two (normally pulmonary
artery [1] and aorta [2] leave the heart).

106.  Causes: In normal circulation, the pulmonary artery comes out of
the right ventricle and the aorta comes out of the left ventricle,
which are separate from each other.
 With truncus arteriosus, a single artery comes out of the ventricles.
There is most often also a large hole between the 2 ventricles
(ventricular septal defect). As a result, the blue (without oxygen)
and red (oxygen-rich) blood mix.
 Some of this mixed blood goes to the lungs, and some goes to the
rest of the body. Often, more blood than usual ends up going to the
lungs.
 If this condition is not treated, two problems occur:
 Too much blood circulation in the lungs may cause extra fluid to
build up in and around them. This makes it hard to breathe.
 If left untreated and more than normal blood flows to the lungs for
a long time, the blood vessels to the lungs become permanently
damaged. Over time, it becomes very hard for the heart to force
blood through them. This is called pulmonary hypertension, which
can be life threatening.

118. 2. Transposition of Great Arteries; Trick: Hold up 2 fingers and cross
them
 Transposition of Great Arteries: Two great arteries leaving the heart are
transposed
 The second cyanotic heart defect is transposition of great arteries.
 You can remember this by holding up 2 fingers and crossing them (to
represent the transposition).
 Transposition of great arteries is when the 2 main arteries leaving the
heart (main pulmonary artery and aorta) are transposed or reversed.
 Remember we said the main pulmonary artery normally leaves the right
heart and goes to the lungs, and the aorta leaves the left heart and goes to
the rest of the body.
 In transposition of great arteries, the pulmonary artery and aorta are
reversed.
 Therefore, the main pulmonary artery arises from the left ventricle
instead of the right, and the aorta arises from the right ventricle instead of
the left.

119. Transposition of Great Arteries: Hold up 2 fingers and cross them
to remember the pulmonary artery (1) and aorta (2) are
transposed (reversed) as shown by the arrows.

120.  The transposition of the aorta and pulmonary artery creates 2 separate
circuits.
 Circuit 1: Deoxygenated blood from the right heart flows to the rest of the
body (via the aorta) and back to the right side of the heart again.
 Normally deoxygenated blood would flow from the right heart to the lungs
via the pulmonary artery.
 Circuit 2: Oxygenated blood from the left heart flows to the lungs (via the
pulmonary artery) and back to the left side of the heart again.
 Normally oxygenated blood would flow from the left heart to the rest of the
body via the aorta.
 In order to be compatible with life, there needs to be a connection between
the 2 circuits to allow for mixing of oxygen-rich and poor blood.
 So there is typically a patent ductus arteriosus or a ventricular septal defect
present.
 As you can imagine, this will lead to the delivery of oxygen-poor blood to
the body and subsequent cyanosis.
 So again, use 2 fingers and cross them to remember transposition of great
arteries and how the 2 great arteries are reversed or transposed.

132. 3. Tricuspid Atresia: Trick: Hold up 3 fingers
 Tricuspid Atresia: Tricuspid valve fails to form (Tri = 3)
 The third cyanotic heart defect is tricuspid atresia.
 Hold up 3 fingers to remember this defect.
 Tricuspid atresia is a congenital heart defect in which the tricuspid valve fails to form.
 Remember in our medical terminology lecture, we learned the prefix “tri-” means 3.
 So holding up 3 fingers will help you remember tricuspid atresia.
 You might remember from the anatomy of the heart lecture that the tricuspid valve is
located between the right atrium and right ventricle.
 In the case of tricuspid atresia, the tricuspid valve fails to form.
 As a result, blood from the right atrium cannot enter the right ventricle.
 Instead, an atrial septal defect is present (a hole in the wall between the right and left
atrium).
 This allows for deoxygenated blood in the right atrium to flow into the left atrium.
 As a result, oxygen-poor blood from the right heart mixes with the oxygen-rich blood in
the left heart.
 This can lead to decreased oxygen levels in the blood delivered to the rest of the body,
which can cause cyanosis.

133. Tricuspid Atresia: Hold up 3 fingers to remember the tricuspid valve
(star) fails to form and blood is unable to flow from the right atrium to
the right ventricle (red X)

134.  There are different types of tricuspid atresia,
but the right ventricle is typically
underdeveloped and the presence of a
ventricular septal defect allows blood from
the left ventricle to enter the right ventricle.
 Remember the right ventricle is not
receiving blood from the right atrium in this
case, so it receives blood from the left
ventricle instead.
 So again, use 3 fingers to remember
tricuspid atresia and how the tricuspid valve
fails to form.

140. Embryology

143. Types

179. 4. Tetralogy of Fallot: Trick: Hold up 4 fingers
 Tetralogy of Fallot: Tetrad of 4 cardiac defects (Tetra = 4)
 The fourth cyanotic heart defect is tetralogy of Fallot.
 Hold up 4 fingers to remember this, as tetralogy of Fallot is a tetrad of 4 cardiac
defects.
 Remember in our medical terminology lecture, the prefix “tetra-” means 4.
 So holding up 4 fingers will help you remember tetralogy of Fallot is a tetrad.
 The tetrad includes:
 Pulmonary Stenosis
 Right Ventricular Hypertrophy (RVH)
 Overriding Aorta
 Ventricular Septal Defect (VSD)
 Pulmonary stenosis is narrowing of the pulmonary valve and main pulmonary artery.
 Right ventricular hypertrophy is thickening of the right ventricular wall.
 Overriding aorta refers to the enlarged aortic valve that seems to open from both
ventricles and sits on top of the ventricular septal defect.
 Finally, the ventricular septal defect is a hole in the wall between the right and left
ventricle.

180.  The pulmonary stenosis, RVH, and VSD can alter
pressure gradients and create a right-to-left shunt,
allowing oxygen-poor blood in the right heart to
flow to the left heart.
 This can lead to cyanosis.
 So again, use 4 fingers to remember tetralogy of
Fallot and how there is a tetrad of 4 cardiac
defects.

181. Tetralogy of Fallot: Hold up 4 fingers to remember the
tetrad of cardiac defects including pulmonary stenosis
(1), right ventricular hypertrophy (2), overriding aorta (3),
and ventricular septal defect (4)

205. Total Anomalous Pulmonary Venous Return (TAPVR): Hold up
5 fingers to remember the 5 words in TAPVR. The pulmonary
veins do not connect to the left atrium (X) like they
normally should (star), instead they connect to the
systemic venous system.

206. 5. Total Anomalous Pulmonary Venous Return (TAPVR)
 Trick: Hold up 5 fingers
 Total Anomalous Pulmonary Venous Return (5 words):
Pulmonary veins connect to systemic venous system rather than
the left atrium
 The fifth cyanotic heart defect is total anomalous pulmonary
venous return (TAPVR).
 Hold up 5 fingers to remember this because there are 5 words
that make up the defect.
 TAPVR is when the pulmonary veins connect to the systemic
venous system rather than the left atrium.
 Normally the 4 pulmonary veins deliver oxygenated blood from
the lungs to the left atrium.
 In the case of TAPVR, the pulmonary veins do not connect to
the left atrium.
 They connect to the systemic venous system instead.

207.  As a result, the oxygenated blood from the lungs mixes with the
deoxygenated venous blood from the body, and the mixed blood flows
back to the right atrium.
 Since the pulmonary veins are not delivering blood to the left atrium,
there is usually an atrial septal defect present to allow blood to travel
from the right atrium to the left atrium.
 Remember the right atrial blood in this case is mixed oxygen-rich and
oxygen-poor blood coming from the rest of the body.
 So the left side of the heart is receiving blood with less than normal
amounts of oxygen (compared to the oxygenated blood it would
normally receive from the pulmonary veins).
 This can cause cyanosis.
 So again, use 5 fingers to remember total anomalous pulmonary
venous return as the defect contains 5 words.
 This is when the pulmonary veins connect to the systemic venous
system rather than the left atrium.